Article

Synthesis and properties of Nasicon-type materials

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Abstract

Various composition of Na1+xSixZr2P3−xO12 (x from 1.6 to 2.4), Y-doped Nasicon (Na1+x+yZr2−yYySixP3−xO12, Na1+xZr2−yYySixP3−xO12−y, where x = 2, y = 0.12) and Fe-doped Nasicon (Na3Zr2/3Fe4/3P3O12) were prepared by coprecipitating. Differential thermal analysis (DTA), thermogravimetry (TG), differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and impedance spectroscopy (IS) were used as experimental techniques.In order to obtain Nasicon materials free from ZrO2 admixture, the calcination of coprecipitates must be carried out in proper thermal conditions. The results of DTA, TG and XRD measurements allowed us to propose the best calcination conditions (to obtain mainly Nasicon phases – monoclinic or rhombohedral, depending on composition).Nasicon-type materials exhibit monoclinic to rhombohedral reversible structural transition, at transition temperature depending on composition (x). The influence of dopants was also studied. The DSC measurements in the temperature range RT–300°C allowed us to determine the temperatures of this structural transition in the case of Na1+xSixZr2P3−xO12, and Y-doped Nasicon. In the case of Fe-doped materials this transition was not detected.Additionally, the correlation between the composition, microstructure and electrical properties was studied.

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... In light of such developments, we marshaled a thorough investigation of the archetypal Na3Zr2Si2PO12 (where x = 2 in the Na1+xZr2SixP3−xO12 formula) that represents the limit case below which ionic conductivity decreases [3,4,[37][38][39]. The primary challenge arises in navigating through the multiple methods developed for NASICON synthesis, which vary from the conventional solid-state reaction (SSR) to sol-gel Pechini methods, and to laser and plasma deposition [40][41][42][43][44][45]. The above also diverge to include variations for optimizing electrical properties, by either controlling the elemental composition (e.g., sodium content) or by optimizing the grain boundaries in the crystalline lattice [46][47][48][49][50][51][52][53][54][55][56]. ...
... Na3Zr2Si2PO12 was synthesized according to the conventional SSR protocol, obtained by a thorough comparison of procedures found in the literature [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55]. Precursors were selected according to availability without special considerations for particle size [54,55], in order to comply with the typical selection of starting materials employed conventionally. ...
... The effects of thermal processing were gauged by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) conducted over the 20 °C to 800 °C range in an inert atmosphere at the same heating rate to emulate the non-oxidative conditions of calcination ( Figure 3). It is noteworthy that thermal analysis in the literature has been conducted largely in synthetic (oxidative) atmospheres, thus severely limiting the derivable information [40,46]. Samples of untreated NASICON powder collected after ball-milling and fully thermally treated powder (pulverized from NASICON pellet after sintering) were compared. ...
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With a crystal lattice structure first characterized in the 1970s, NASICON sodium-based superionic conductors have recently found renewed interest as solid electrolytes in sodium-ion and seawater flow batteries due to their exceptional ionic conductivity being on the same scale as liquid electrolytes. Since sodium ions in the crystal lattice move among interstitial positions through site-specific bottlenecks, the overall conductivity is strongly dependent on the NASICON composition. In this work, we report on the synthesis protocols and processing parameters of Na3Zr2Si2PO12 prepared from Na2CO3, SiO2, ZrO2, and NH4H2PO4 precursors by the conventional solid-state reaction (SSR) route. We critically evaluated important observations made in the extended literature on the topic including: (i) the importance of precursor particle size concerning the SSR synthesis, focusing on effective ball-milling protocols; and (ii) the onset of excess zirconia contamination, expanding on the effects of both thermal and pressure processing—the latter often overlooked in the available literature. In approaching the cryogenic regime, the dataset availability concerning ionic conductivity and dielectric permittivity measurements for NASICON was extended, starting from elevated temperatures at 200 °C and reaching into the very low temperature zone at −100 °C.
... Zr 4+ + OH -→ ZrOH 3+ K = 10 14 (1) ZrOH 3+ → ZrO 2+ + H + K = 10 0.7 (2) ZrO 2+ + HPO 4 2-→ ZrOHPO 4 K = 10 19.5 (3) In the formation of complex compounds, Zr 4+ reacted with carbonyl group in acidic compounds to form RCOOZr as the following predicted reactions: ...
... Meanwhile, the other exothermic reactions occurred at 200-750 0 C. These exothermic reactions were predicted due to oxidation of organic compounds [2] and decomposition of NH 4 NO 3 during calcinations processes [4]. The formation of ZrO 2 tetragonal as predicted happened at 605 0 C was in line with the previous research by Ignaszack et.al in 2005 [4]. ...
... These exothermic reactions were predicted due to oxidation of organic compounds [2] and decomposition of NH 4 NO 3 during calcinations processes [4]. The formation of ZrO 2 tetragonal as predicted happened at 605 0 C was in line with the previous research by Ignaszack et.al in 2005 [4]. The peaks at 975 0 C did not cause mass change. ...
... • Conventional solid-state reaction [3,11,12], • Precursor based sol-gel methods (i.e. metal alkoxides [13][14][15][16][17][18], citrate gel (Pechini's method [19]) [20,21], silica gel [22][23][24]), • Hydrothermal synthesis [25][26][27], • Nonhydrolytic synthesis [28], • Coprecipitation [29], • Mechanochemical synthesis [30], and • Combustion method [31] The conventional high-temperature solid-state reaction (SSR) is the most simple synthesis method. It involves mixing the oxides, hydroxides or carbonates followed by calcination and sintering at high temperature to get the desired material [32]. ...
... Samples produced by sintering of co-precipitated powder have a low conductivity of 9.2 × 10 −5 S cm −1 [29]. The highest conductivity of 1.8 × 10 −3 S cm −1 at 25°C is reported for spark plasma sintering of SSR powder. ...
... The formation of ZrO 2 during the densification of Na 3 Zr 2 (SiO 4 ) 2 (PO 4 ) was also observed by other synthesis and processing methods [10,29,36]. This is due to an earlier crystallization of ZrO 2 prior to the NASICON formation resulting from the high thermodynamic stability of ZrO 2 and not due to volatility of reagents (e.g. ...
Article
The Na⁺ super-ionic conductor Na3Zr2(SiO4)2(PO4), known as the original NASICON material, is a promising solid-state electrolyte that can be used for sodium batteries. A solution-assisted solid state reaction (SA-SSR) method has been developed for its synthesis. The method is convenient, low-cost, and has potential for large scale production. The total conductivity of the sample synthesized by SA-SSR is 1 × 10− 3 S cm− 1 at 25 °C, which is one of the highest reported data of this composition after conventional processing of the ceramic powder. To rationalize the advantages of the method, a comparison of powders and ceramics prepared by the Pechini and SA-SSR methods was carried out. Scanning electron microscopy, X-ray diffraction and impedance spectroscopy were used to investigate the products of both synthesis routes and the possible reasons of the high quality of SA-SSR samples are discussed.
... e l s e v i e r . c o m / l o c a t e / e l e c t a c t a conductivity [8][9][10][11][12]. Some reports on microstructure showed that the NASICON ceramics often are not monophase and a glassy phase which is basically a sodium silicophosphate with some dissolved zirconia results from the liquid phase formed during sintering [2,[12][13][14]. ...
... Some reports on microstructure showed that the NASICON ceramics often are not monophase and a glassy phase which is basically a sodium silicophosphate with some dissolved zirconia results from the liquid phase formed during sintering [2,[12][13][14]. Therefore, some attempts have been made to improve the phase purity including chemical synthesis method [9,[15][16][17] doping strategy [9,14,18] and spark plasma sintering route [13]. ...
... Some reports on microstructure showed that the NASICON ceramics often are not monophase and a glassy phase which is basically a sodium silicophosphate with some dissolved zirconia results from the liquid phase formed during sintering [2,[12][13][14]. Therefore, some attempts have been made to improve the phase purity including chemical synthesis method [9,[15][16][17] doping strategy [9,14,18] and spark plasma sintering route [13]. ...
Article
In this work, the solid electrolyte Na3+xZr2-xMxSi2PO12, M = Ce4+, Gd3+ and Yb3+ compounds were synthesized by a solid state reaction. The ceramic samples were sintered in the temperature range 1150-1300 °C with 5 h holding time. X-ray diffraction, scanning electron microscopy (SEM) and complex impedance spectroscopy (IS) were used as experimental techniques. The investigated compounds at room temperature belong to monoclinic symmetry, and Ce4+, Gd3+ and Yb3+ ions substitution range decreases with increases of x, therefore, optimal concentration was fixed at x = 0.1. Results showed the significant influences of dopant ions and the processing condition on the microstructure and conductivity of these ceramics. Dense Ce4+ and Gd3+ doped samples were obtained at higher sintering temperature than Yb3+ doped and Na3Zr2Si2PO12 ceramics. A drop in grain boundary conductivity due to glassy phase formation in Na3Zr2Si2PO12 and Yb3+ doped compounds was observed. Maximum conductivity value at room temperature was obtained for Na3+xZr1.9Ce0.1Si2PO12 sample.
... Many methods have been used to prepare NZSP such as conventional solid-state reaction (CSSR) [10], sol-gel [11], hydrothermal [12], coprecipitation [13], mechanochemical synthesis [14]. Although the sol-gel and coprecipitation methods can synthesize pure materials at lower temperatures due to the homogeneous mixing of precursors at the atomic/molecule scale, the obtained ceramic pellets show rather low electrical conductivity, 9.2 × 10 − 5 S cm − 1 at 25 • C for coprecipitation samples [13]. ...
... Many methods have been used to prepare NZSP such as conventional solid-state reaction (CSSR) [10], sol-gel [11], hydrothermal [12], coprecipitation [13], mechanochemical synthesis [14]. Although the sol-gel and coprecipitation methods can synthesize pure materials at lower temperatures due to the homogeneous mixing of precursors at the atomic/molecule scale, the obtained ceramic pellets show rather low electrical conductivity, 9.2 × 10 − 5 S cm − 1 at 25 • C for coprecipitation samples [13]. Accordingly, the solid-state reaction is still the dominant method to prepare NASICON considering its easy operation and costeffectiveness. ...
Article
NASICON-type solid-state electrolyte is characterized by high electrical conductivity but its application in all-solid-state battery is limited by the high sintering temperature and poor interface contact with the electrodes. Here, solid-state reactive sintering, without intermediate calcination and ball-milling steps and no sintering additive, is proposed to prepare dense and highly conductive NASICON at lower temperatures. The samples sintered at 950 and 1000 °C achieve relative density of ~90% and high ion conductivity of 8.43 × 10⁻⁴ and 1.48 × 10⁻³ S cm⁻¹ at room temperature, respectively. The reasonable interface contact between sodium metal and 950 °C-sintered electrolyte affords the symmetric sodium battery to cycle stably at 0.05 mA cm⁻² for ~1000 h and full battery at 0.1C (0.02 mA cm⁻²) at room temperature. This work provides a new strategy to prepare NASICON solid-state electrolyte, which can be extended to prepare other solid-state electrolytes and thus promote the development of all-solid-state battery.
... For LATP materials, the thermal stability varied from 497-475 °C depending on the percentage of Al-dopants as evidenced in Table 2. The same compartment was noted by [35] as well as in the synthesis of Na 1+x Zr 2 Si x P 3-x O 12 via the co-precipitation process by [36]. ...
Article
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The use of solid-state electrolytes (SSEs) instead of liquid organic electrolytes presents one of the important means to increase the energy density and resolve the protection issues of lithium batteries. The development of SSEs compounds, which can suit high-voltage cathodes and lithium metal anode (LMA) is rather important to progress high-energy–density lithium batteries. Among the different compounds, lithium aluminum titanium phosphates (LATP) are especially potential candidates for all-solid-state batteries (ASSBs) since their present high ionic conductivity, superior air stability, and low cost. In this paper, the Li1+xAlxTi2−x(PO4)3 (LATP) compounds with different mixtures have been synthesized via solid-state technique. The rhombohedral phase (space group \(R\overline{3 }c\)) of these samples is confirmed through the powder X-ray diffraction measurements. The thermogravimetric (TG) measurements show that when x-content increments in LATP, the integral temperature of decomposition reduces. Likewise, the temperature whereupon the samples turn stable decreases, which suggested that phase stability is related by the rise of the x-content in the basic sample. Through the 101–106 Hz frequency area, the real and imaginary parts of the dielectric permittivity, the electric modulus, and alternating current (AC) conductivity of LATP samples display temperature reliance. The different contributions of grains and grain boundaries to the total impedance are confirmed by the Nyquist curves. The alternating current (AC) conductivity is illustrated in terms of Jonncher’s power law. The studies on charge transportation suggest the presence of the overlapping large polaron tunneling mechanism (LATP − x = 0.0) and the non-overlapping small polaron tunneling mechanism (LATP − x = 0.3 and LATP − x = 0.5).
... Powders of NASICON oxides are extensively synthesized using two methods, i.e., sol-gel and solid-state reaction processes [90,95,[98][99][100][101]. However, in a few studies, other processes such as hydrothermal [102,103], co-precipitation [104], mechanochemical synthesis [105], and combustion synthesis [106] are also employed for the powder synthesis. In the solid-state reaction method, the stoichiometric proportions of required powder reactants are thoroughly mixed and ground into fine particles using wet ball milling. ...
Article
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Solid-state batteries have shown the potential to resolve the safety and durability issues associated with traditional liquid electrolyte-based batteries. This article reviews the current developments of NASICON-type solid electrolytes for Na-ion solid-state batteries. These ceramic-based oxides possess a 3D open-framework structure allowing for the fast diffusion of large sodium ions. To date, the conductivity value as high as ~ 5 mS·cm⁻¹ at 25 °C is reported for these materials, which needs to be further improved. The requirement of high-temperature sintering (> 1200 °C), anisotropic thermal expansion, impurity phase formation, and large interfacial impedance are other challenges of NASICON-type electrolytes. This article summarizes various fundamental aspects governing the sodium-ion conduction in these oxides. Particular emphasis is given to the strategies employed in recent investigations to improve the properties and alleviate the associated issues in designing stable solid-state sodium-ion rechargeable batteries. This will also establish the groundwork for future research in these materials. Graphical Abstract
... Rietveld refinements were done using WinPLOTR and FullProf software. For x = 1.5 the pattern was fitted using the R 3c space group 18,76,80,81 , while x = 2.0 and x = 2.4 were fitted using the C2=c space group 33,82 . ...
Article
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Lithium and sodium (Na) mixed polyanion solid electrolytes for all-solid-state batteries display some of the highest ionic conductivities reported to date. However, the effect of polyanion mixing on the ion-transport properties is still not fully understood. Here, we focus on Na1+xZr2SixP3−xO12 (0 ≤ x ≤ 3) NASICON electrolyte to elucidate the role of polyanion mixing on the Na-ion transport properties. Although NASICON is a widely investigated system, transport properties derived from experiments or theory vary by orders of magnitude. We use more than 2000 distinct ab initio-based kinetic Monte Carlo simulations to map the compositional space of NASICON over various time ranges, spatial resolutions and temperatures. Via electrochemical impedance spectroscopy measurements on samples with different sodium content, we find that the highest ionic conductivity (i.e., about 0.165 S cm–1 at 473 K) is experimentally achieved in Na3.4Zr2Si2.4P0.6O12, in line with simulations (i.e., about 0.170 S cm–1 at 473 K). The theoretical studies indicate that doped NASICON compounds (especially those with a silicon content x ≥ 2.4) can improve the Na-ion mobility compared to undoped NASICON compositions.
... Improved ionic conductivities of NZSP were obtained by substitution of Zr 4+ ions with aliovalent cations (e.g., Ni 2+ , Co 2+ , Zn 2+ , Mg 2+ , Ca 2+ , Al 3+ , Fe 3+ , Y 3+ , Sc 3+ , Yb 3+ , La 3+ , Nd 3+ , Nb 5+ ) and/or equivalent cations (e.g., Ce 4+ , Ti 4+ , Sn 4+ , Ge 4+ ) [6][7][8][9][10][11][12][13][14] . Besides, different synthesis strategies, such as solid-state reaction (SSR) 15,16 , solution-assisted SSR (SA-SSR) 17 , solgel 18 , coprecipitation 19 , mechanochemical 20 , and combustion method, 21 were employed to prepare NZSP. The NZSP ceramic powder prepared by SSR method with sintering temperature of 1220 • C/10 h or SA-SSR method with a sintering temperature of 1250 • C/5 h is reported to show the highest total conductivity of 1.0 mS/cm at 25 • C 17,22 . ...
Article
Sodium superionic conductor Na3Zr2Si2PO12 (NZSP) is a promising material as a solid electrolyte for sodium‐ion batteries. The highest conductivity of ∼1.0 mS/cm at room temperature (RT) was reported for the compound with Na content ∼3.3 per formula unit (f. u.) and when the material is synthesized with final sintering temperature ≥1220°C. Herein, we propose a new synthesis method to enhance the conductivity of the NZSP by liquid phase sintering with the optimum amount of additive of amorphous‐Na2Si2O5. In this regard, a series of composite materials were prepared by mixing Na3Zr2Si2PO12 with amorphous‐Na2Si2O5 (NZSP/NS‐x wt %; with x = 0.0, 2.5, 5.0, 7.5, 10.0) and sintering at a lower temperature of 1150°C. Enhanced conductivity of 1.7 mS/cm at RT has been achieved for the Na3Zr2Si2PO12/Na2Si2O5‐5.0 wt‐% (NZSP/NS‐5.0) composite. The effect of additives on the NZSP phase formation, microstructure, and ion conductivity has been investigated by XRD, MAS NMR, SEM, and impedance spectroscopy. Our study demonstrates that higher conductivity of NZSP/NS‐5.0 composite is caused by the combined effect of increased Na content in the NZSP phase (by diffusion of Na+ ions from the liquid phase of NS to bare NZSP phase), higher density, and microstructures with lesser pores. This article is protected by copyright. All rights reserved
... Since there is no commercially available source for Na 1+x Zr 2 (SiO 4 ) x (PO 4 ) 3−x (NaZSiP), a synthetization route had to established for the production of the starting powder. Since a simple solid-state reaction process is known to be problematic [13,23,24] achieving the target stoichiometry due to the high-temperature processes involved, the so-called solution-assisted solid-state reaction (SA-SSR) [25] was adapted for the production of the NaZSiP powder. For the consolidation of the ceramic powder, a field-assisted sintering technology (FAST) at a temperature of 900 °C and also CIP followed by pressureless sintering at 1250 °C for 5 h was applied. ...
Article
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We have studied the ionic and thermal transport properties along with the thermodynamic key properties of a Na-ion-conducting phosphate ceramic. The system Na1+xAlxTi2−x(PO4)3 (NATP) with x = 0.3 was taken as a NASICON-structured model system which is a candidate material for solid electrolytes in post-Li energy storage. The commercially available powder (NEI Coorp., USA) was consolidated using cold isostatic pressing before sintering. In order to compare NATP with the “classical” NASICON system, Na1+xZr2(SiO4)x(PO4)3−x (NaZSiP) was synthesized with compositions of x = 1.7 and x = 2, respectively, and characterized with regard to their ionic and thermal transport behavior. While ionic conductivity of the NaZSiP compositions was about more than two orders of magnitude higher than in NATP, the thermal conductivity of the NASICON compound showed an opposite behavior. The room temperature value was about a factor two higher in NATP compared to NaZSiP. While the thermal conductivity decreases with increasing temperature in NATP, it increases with increasing temperature in NaZSiP. However, the overall change of this thermal transport parameter over the measured temperature range from room temperature up to 800 °C appeared to be relatively small.
... This persistent presence of ZrO2 in the NaSICON materials was often reported earlier. [27][28][29][30] Here, monoclinic ZrO2 was detected as the secondary phase with different amounts only for samples with a high content of Zr (0 ≤ x ≤ 1) and heat-treated at high temperatures (> 1230 °C). As a result, Na3Zr1.67Si2P1.33O12.17 ...
Article
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Two types of solid electrolytes have reached technological relevance in the field of sodium batteries: ß/ß”‐aluminas and NaSICON‐type materials. In comparison, NaSICON materials can be processed at lower sintering temperatures than the ß/ß”‐aluminas and have a similarly attractive ionic conductivity. Since Na 2 O‐SiO 2 ‐ZrO 2 ‐P 2 O 5 ceramics offer wider compositional variability, the series Na 3 Zr 3‐x Si 2 P x O 11.5+x/2 with seven compositions (0 ≤ x ≤ 3) was selected from the quasi‐quaternary phase diagram in order to identify the predominant stability region of NaSICON within this series and to explore the full potential of such materials, including the original NaSICON composition of Na 3 Zr 2 Si 2 PO l2 as a reference. Several characterization techniques were used for the purpose of better understanding the relationships between processing and properties of the ceramics. X‐ray diffraction analysis revealed that the phase region of NaSICON materials is larger than expected. Moreover, new ceramic NaSICON materials were discovered in the system crystallizing with a monoclinic NaSICON structure (space group C2/c ). Impedance spectroscopy was utilized to investigate the ionic conductivity, giving clear evidence for a dependence on crystal symmetry. The monoclinic NaSICON structure showed the highest ionic conductivity with an optimum ionic conductivity of 1.22 × 10 −3 at 25 °C for the composition Na 3 Zr 2 Si 2 PO 12 .
... For this purpose, advanced powder X-ray or neutron diffraction experiments are required because they should identify phase separation and reveal all the crystalline phases that would eventually coexist in a given sample. Differential scanning calorimetry can also be used to identify the well-documented albeit weak rhombohedral-to-monoclinic phase transition, 9,40,88 but phase separation has not been observed so far in the rhombohedral phase. ...
Article
The replacement of the presently used liquid electrolytes by a non-flammable solid electrolyte is an important avenue to create safer batteries. The Natrium Superionic CONductor (NaSiCON) Na1+xZr2SixP3–xO12 (0 ≤ x ≤ 3) that displays high bulk ionic conductivity and good stability towards other NaSiCON-based electrodes is a good solid electrolyte in NaSiCON-based batteries. Despite the sizeable share of research on Na1+xZr2SixP3–xO12, the structural and thermodynamic properties of NaSiCON require better understanding for more efficient synthesis and optimization as a solid electrolyte, which often follows chemical intuition. Here, we analyze the thermodynamic proper- ties of the rhombohedral NaSiCON electrolyte by constructing the Na1+xZr2SixP3–xO12 phase diagram, based on density functional theory calculations, a cluster expansion framework, and Monte Carlo simulations. Specifically, we build the phase diagram as a function of temperature and composition (0 ≤ x ≤ 3) for the high-temperature rhom- bohedral structure, which has been also observed in several positive electrode materials, such as Na3Ti2(PO4)3, Na3V2(PO4)3, Na3Cr2(PO4)3, and Na3Fe2(PO4)3. Through the phase diagram, we identify the concentration domains providing the highest Na -ion conductivity and previously unreported phase-separation behavior across three different single-phase regions. Further, we note the similarities in the phase behavior between Na1+xZr2SixP3–xO12 and other NaSiCON-based mono-transition metal electrodes and discuss the potential competition between thermodynamics and kinetics in experimen- tally observed phase separation. Our work is an important addition in understanding the thermodynamics of NaSiCON-based materials and in the development of inexpen- sive Na-ion batteries. From our results we propose that the addition of SiO4– moieties 4 to single-transition metal NaSiCON-phosphate-based electrodes will slow significantly the kinetics toward phase separation.
... The differential thermal analysis (DTA)/TGA curves of the as-produced Na 3 Ce x Zr 2−x Si 2 PO 12 (x = 0, 0.1, 0.2, 0.3) NPs are shown in Figure 5a,b. As for Na 3 Zr 2 Si 2 PO 12 and Na 3 Ce 0.1 Zr 1.9 Si 2 PO 12 , the characteristic feature of this DTA/ TGA corresponds to published work, 32 an exotherm appears at 157°C for the monoclinic−rhombohedral transition. However, the peak intensity in Na 3 Ce 0.2 Zr 1.8 Si 2 PO 12 decreases and disappears completely in Na 3 Ce 0.3 Zr 1.7 Si 2 PO 12 , which can be concluded as Ce doping increase; the crystal structure changes slightly from monoclinic to rhombohedral at room temperature. ...
... The differential thermal analysis (DTA)/TGA curves of the as-produced Na 3 Ce x Zr 2−x Si 2 PO 12 (x = 0, 0.1, 0.2, 0.3) NPs are shown in Figure 5a,b. As for Na 3 Zr 2 Si 2 PO 12 and Na 3 Ce 0.1 Zr 1.9 Si 2 PO 12 , the characteristic feature of this DTA/ TGA corresponds to published work, 32 an exotherm appears at 157°C for the monoclinic−rhombohedral transition. However, the peak intensity in Na 3 Ce 0.2 Zr 1.8 Si 2 PO 12 decreases and disappears completely in Na 3 Ce 0.3 Zr 1.7 Si 2 PO 12 , which can be concluded as Ce doping increase; the crystal structure changes slightly from monoclinic to rhombohedral at room temperature. ...
Article
The urgent need for high-performance solid electrolytes has aroused considerable focus on NASICON ceramics. Optimization of processing routes to dense, defect-free materials has yet to receive sufficient attention to date. Although traditional solid-state reaction methods followed by repetitive ball milling and sintering up to 10 h above 1200 °C are common place, the resulting average particle sizes are usually too large to produce dense, robust structures because of excessive grain growth. In this study, nanopowders (NPs) are produced, which offer a superior opportunity to make dense, high-phase-purity sintered bodies. Here, we report on the effect of sintering conditions on the microstructures and phase of Ce4+-substituted NASICON samples, Na3Ce x Zr2-xSi2PO12 (x = 0, 0.1, 0.2, 0.3). NPs permit processing fine-grained solid-state electrolytes with 98% relative density at 1100 °C/5 h. In addition, Rietveld refinement was applied to evaluate 3-D Na-ion diffusion channels among different NASICON samples. Also, it is found that adding 5 at % Ce4+ does not change the phase structure but dramatically enlarges the Na+ diffusion "bottleneck" from 5.4 to 5.6 Å2. This may be one reason for these samples to exhibit conductivities of 2.4 × 10-2 S cm-1 at 140 °C.
... These are in agreement with TGA results reported by Savitha et al. [11] in the study of thermal analysis of Li 2 AlZr(PO 4 ) 3 . A similar trend was also reported [12] for Na 1+x Zr 2 Si x P 3−x O 12 prepared using co-precipitation method [13]. The results obtained in this study is quite different from that has already been reported [14] in which the substitutions of Hf 4+ involved Cr and Fe ions in the crystalline materials. ...
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Lithium ion conducting solid electrolytes, lithium aluminum hafnium phosphate (Li1+xHf2−xAlx(PO4)3, x = 0–0.75) are prepared via solid state synthesis technique. Thermo-gravimetric analysis indicates that the thermal decomposition and thermal stability of the reaction mixture is generally affected by a high content of x value substitution. It can be observed that as x content or aluminum substitution increases, the thermal decomposition and thermal stability increase which leads to the sample formation towards higher temperature. For X-ray diffraction analysis, the Rietveld refinement analysis indicates the presence of different types of secondary phases as aluminum content increases. Single phase of lithium hafnium phosphate (LiHf2(PO4)3) is only achievable in the absence of any aluminum substitution. Furthermore, for the lithium ionic conductivity, the findings indicate that conductivity increases with increase in x substitution in lithium aluminum hafnium phosphate. The highest AC conductivity is observable in the sample with composition x = 0.25 of about 2.5 × 10⁻³ Ω⁻¹m⁻¹ with low activation energy 0.36 eV. The present studies recommend the sample with composition x = 0.25 (Li1.25Hf1.75Al0.25(PO4)3) to be a future solid electrolyte material for battery applications.
... In comparison, other reported NASICONs have been extensively investigated by means of scanning electron-microscopy (SEM). 29,[34][35][36][37][38] They typically exhibit more severe cracks, poor contact between grains, and lower relative density due to the inappropriate processing technology. This explains why NASICONs have previously exhibited inferior s total and the value of s total scattered greatly even for the same composition at room temperature. ...
Article
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The lack of suitable candidate electrolyte materials for practical application limits development of all-solid-state Na-ion batteries. Na3+xZr2Si2+xP1-xO12 were the very first series of NASICONs discovered some 40 years ago; however, separation of bulk conductivity from total conductivity at room temperature is still problematic. It has been suggested that the effective Na-ion conductivity is ~10-4 S cm-1 at room temperature for Na3+xZr2Si2+xP1-xO12 ceramics; however using solution-assisted solid-state reaction for preparation of Na3+xZr2Si2+xP1-xO12, total conductivity of 5 × 10-3 S cm-1 was achieved for Na3.4Zr2Si2.4P0.6O12 at 25 °C, higher than previously reported for polycrystalline Na-ion conductors. Bulk conductivity of 1.5 × 10-2 S cm-1 was revealed by high frequency impedance spectroscopy (up to 3 GHz) and verified by low temperature impedance spectroscopy (down to -100 °C) for Na3.4Zr2Si2.4P0.6O12 at 25 °C, indicating further potential of increasing the related total conductivity. A Na/Na3.4Zr2Si2.4P0.6O12/Na symmetric cell showed low interface resistance and high cycling stability at room temperature. A full-ceramic cell was fabricated and tested at 28 °C with good cycling performance.
... The major percentage mass loss occurred in the region I to IV which is associated with the decomposition of NH4H2PO4, AlO2and Li2CO3to evolve water moisture (H2O), ammonia (NH3) and carbon dioxide (CO3).As temperature increases through the regions the rate of mass loss decreased and become constant along region V. The thermal stability was observed to vary in all the samples ranging from 482-400 o C depending on the stoichiometry of the mixtures as shown in Table1.Similar trend was reported by [7] and also in the preparation of Na1+xZr2SixP3-xO12 using co-precipitation method by [8]. Figure 2 indicates the derivative thermo-gravimetric (DTG) (-dm/dt) data the figure describes the rate of mass loss as temperature changes which has advantages of providing higher resolution and better specific temperature behavior. ...
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The compounds lithium aluminum titanium phosphates Li1+xTi2-xAlx(PO4)3(LATP) with various compositions 0 <x< 1have been synthesized using solid-state method. The as-prepared sample has been characterized using various techniques. From TGA result, it has been observed that as x-content increases into the reaction mixture the integral temperature of decomposition decreases. Similarly, the temperature at which the materials become stable also decreases this indicated that phase stability is affected by increasing x content into basic compound. For structural analysis; the samples were successfully synthesized with R-3c space group assuming a hexagonal crystal axis with ICSD database 98-006-9677. The finding showed that single phase is only observed with lower x-value substitution. As Al content increases the number of secondary phases were observed to increase with various aluminum phosphate(AlPO4).
... Nasicon is a solid solution of NaZr 2 P 3 O 12 and Na 4 Zr 2 Si 3 O 12 and is composed of corner-shared ZrO 6 T that forms three dimensional Na + -conducting channels. Nasicon compounds (Na 1+x Zr 2 Si x P 3-x O 12 , 0 ≤ x ≤ 3) have a rhombohedral phase (R3c), but a monoclinic phase (C2/c) can be stabilized at specific compositions (1.6 ≤ x ≤ 2.4) and temperature conditions (< ∼150°C) [20,22,23]. ...
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Molten sodium (Na) anode high temperature batteries, such as Na-NiCl2 and Na-S, draw attentions to be used in stationary electricity storage applications. Recent efforts are exerted to lower their operating temperatures down to below 200 °C in order to adopt ultra-low cost cell production, establish easier maintenance, pursue enhanced safety, and more. One of main challenges in lowering the operation temperature is radical decrease in ionic conductivity of their solid electrolytes. Na3Zr2Si2PO12 (Nasicon) is considered as a solid electrolyte for the lower temperature operation. Here we report Na ionic conductivity of Nasicon at 150 °C increases by adding Ge element. The ionic conductivity of Ge-added sample (Na3[Zr2-δGeδ]Si2PO12, δ = 0.1, 0.2) is measured as high as 1.4 × 10−2 S cm-1 at 150 °C which is about two times higher than those of the bare Nasicon. The phase transition temperature of the Ge-added samples is lowered, thereby the volume fraction of the rhombohedral phase, which is stable at higher temperatures and exhibits higher Na ion conductivities, increases. This finding provides a useful guideline to further increase the ionic conductivity of Nasicon solid electrolytes, which can advance materialization of lower temperature operating Na batteries.
... The formation of ZrO 2 during the densification of NZSP was also observed using other synthesis and processing methods. 8,11,13 This is due to an earlier crystallization of ZrO 2 prior to NASICON formation, resulting from the high thermodynamic stability of ZrO 2 and not due to the volatility of reagents (eg, sodium monoxide) at the sintering temperature. As demonstrated earlier, ZrO 2 starts to crystallize at 800°C for SA-SSR powders. ...
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The ionic conductivity of solid electrolytes is dependent on synthesis and processing conditions, i.e. powder properties, shaping parameters, sintering time (ts), and sintering temperature (Ts). In this study, Na3Zr2(SiO4)2(PO4) was sintered at 1200 °C and 1250 °C for 0–10 h and its microstructure and electrical performance were investigated by means of scanning electron microscopy and impedance spectroscopy. After sintering under all conditions, the NASICON‐type structure was formed along with ZrO2 as a secondary phase. The microstructure investigation revealed a bimodal particle size distribution and grain growth at both Ts. The density of samples increased from 60% at 1200 °C for 0 h to 93% at 1250 °C for 10 h. The ionic conductivity of the samples increased with ts due to densification and grain growth, ranging from 0.13 mS cm⁻¹ to 0.71 mS cm⁻¹, respectively. The corresponding equivalent circuit fitting for the impedance spectra revealed that grain boundary resistance is the prime factor contributing to the changing conductivity after sintering. The activation energy of the bulk conductivity (Ea,bulk) remained almost constant (0.26 eV) whereas the activation energy of the total conductivity (Ea) exhibited a decreasing trend from 0.37 eV to 0.30 eV for the samples with ts = 0 h and 10 h, respectively – both sintered at 1250 °C. In this study, the control of the grain boundaries improved the electrical conductivity by a factor of six. This article is protected by copyright. All rights reserved.
... The formation of ZrO 2 during densification of NASICON was also observed by others [25][26][27]. The ZrO 2 forms due to its high thermodynamic stability and lower crystallization temperature prior to the NASICON phase, and not due to the volatility of reagents (e.g. ...
... [20] Copyright 1967 Argonne National Laboratory. Besides the β″-Al 2 O 3 , other solid-state electrolytes, such as NASICON, [74] are being studied and showing good Na + conductivity under 200 °C. A battery employing the NASICON electrolyte will be discussed below. ...
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The increasing demands for integration of renewable energy into the grid and urgently needed devices for peak shaving and power rating of the grid both call for low-cost and large-scale energy storage technologies. The use of secondary batteries is considered one of the most effective approaches to solving the intermittency of renewables and smoothing the power fluctuations of the grid. In these batteries, the states of the electrode highly affect the performance and manufacturing process of the battery, and therefore leverage the price of the battery. A battery with liquid metal electrodes is easy to scale up and has a low cost and long cycle life. In this progress report, the state-of-the-art overview of liquid metal electrodes (LMEs) in batteries is reviewed, including the LMEs in liquid metal batteries (LMBs) and the liquid sodium electrode in sodium-sulfur (Na-S) and ZEBRA (Na-NiCl2) batteries. Besides the LMEs, the development of electrolytes for LMEs and the challenge of using LMEs in the batteries, and the future prospects of using LMEs are also discussed.
... For NZSP, one can hardly detect a reversible tiny thermal phenomenon at w155 C that corresponds to the well documented transition to the superionic state in NASICON compositions [13,26,27,33,34]. As reported by Boilot et al. [33], the material's preparation method and the sintering temperature in particular, impact greatly on temperature-dependent effects of such thermally activated transition. ...
... Carbon fibre [91] 0.5 m NaCF 3 SO 3 in DEGDME 700 mA h À1 g À1 at 45.2 mA g À1 Diamond-like carbon [93] 1 m NaPF 6 in EC/DMC 1884 mA h À1 g À1 at 0.1 C Graphene nanosheet [94] 0.25 m NaPF 6 in DME 6208 mA h À1 g À1 at 300 mA g À1 Super-P carbon [95] 1 m NaClO 4 in TEGDME, 0.75 m NaCF 3 SO 3 in EMImCF 3 SO 3 2882 mA h À1 g À1 , 3500 mA h À1 g À1 at 70 mA g À1 Carbon paste (Ketjen Black and Kynar 2801) [97] 1 m NaClO 4 in PC 2800 mA h À1 g À1 1 m NaClO 4 in TEGDME 6000 mA h À1 g À1 NaOH solution with graphite plate [98] (0.5 or 1 m) NaPF 6 in PC + NASICON (Na 3 Zr 2 Si 2 PO 12 ) 600 mA h À1 g À1 at 0.63 mA cm À2 monoclinic structure of Na 1 + x Zr 2 Si x P 3-x O 12 is reversibly transformed into a rhombohedral structure at a specific temperature; this phase transition temperature is dependent on both the value of x in Na 1 + x Zr 2 Si x P 3-x O 12 (1.8 < x < 2.2) and sintering temperature. [103] For example, Na 3 Zr 2 Si 2 PO 12 sintered at 1150 8C has a monoclinic structure at 25 8C, which transforms into a rhombohedral structure at 300 8C. The phase transition is attributed to the local lattice distortion caused by displacement of Zr 4 + ions from their proper sites and formation of additional interstitial sites for Na + between two Zr 4 + sites. ...
Article
Impressive developments have been made in the past a few years toward the establishment of Na-ion batteries as next-generation energy-storage devices and replacements for Li-ion batteries. Na-based cells have attracted increasing attention owing to low production costs due to abundant sodium resources. However, applications of Na-ion batteries are limited to large-scale energy-storage systems because of their lower energy density compared to Li-ion batteries and their potential safety problems. Recently, Na-metal cells such as Na–metal halide and Na–air batteries have been considered to be promising for use in electric vehicles owing to good safety and high energy density, although less attention is focused on Na-metal cells than on Na-ion cells. This Minireview provides an overview of the fundamentals and recent progress in the fields of Na–metal halide and Na–air batteries, with the aim of providing a better understanding of new electrochemical systems.
... Nasicon, LaOCl and 0.85Na 2 Ti 3 O 7 -0.15Na 2 Ti 6 O 13 powders were prepared by methods described elsewhere [10][11][12]. LaOCl was doped using Na 2 CO 3 by a solid-state reaction to obtain nominally La 1 − x Na x OCl 1 − 2x (x = 0.01, 0.05, 0.1, 0.2). The optimal calcination conditions (400°C/6 h) were determined by means of the differential thermal analysis (DTA) and thermogravimetry (TG). ...
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The prototype potentiometric chlorine gas sensor was constructed using Na3Zr2Si2PO12 (Nasicon) as a solid electrolyte, two-phase (1 – y)LaOCl–yNaCl as a sensing electrode, and 0.85Na2Ti3O7-0.15Na2Ti6O13 as a reference electrode. Nasicon, 0.85Na2Ti3O7–0.15Na2Ti6O13 two-phase system and LaOCl powders were prepared by solid‐state reaction method. Two-phase materials (1 – y)LaOCl–yNaCl of different compositions were obtained by doping LaOCl with Na2CO3. The best preparation conditions were determined based on differential thermal analysis and thermogravimetry (DTA and TG). All the samples were studied by X-ray diffraction (XRD) analysis. Electrical conductivity of (1 – y)LaOCl–yNaCl was measured using electrical impedance spectroscopy (EIS). The source voltage (SV) of the fabricated cell was measured as a function of temperature (400–600 °C), Cl2 partial pressure in the range 1–9 Pa and time. Constructed sensor shows the most effective performance at 500 °C and in Cl2 pressure range of 3–9 Pa.
... NASICON compounds have usually been synthesized by two methods: traditional ceramic route and sol-gel process (see ref. 78), but other synthetic strategies have also been used. [84][85][86][87] Porkodi et al. have proposed a new synthesis method for these phases based on a molecular precursor. 88 The conductivity value of the best sample was 2.2 Â 10 À3 S cm À1 . ...
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Energy production and storage have become key issues concerning our welfare in daily life. Present challenges for batteries are twofold. In the first place, the increasing demand for powering systems of portable electronic devices and zero-emission vehicles stimulates research towards high energy and high voltage systems. In the second place, low cost batteries are required in order to advance towards smart electric grids that integrate discontinuous energy flow from renewable sources, optimizing the performance of clean energy sources. Na-ion batteries can be the key for the second point, because of the huge availability of sodium, its low price and the similarity of both Li and Nainsertion chemistries. In spite of the lower energy density and voltage of Na-ion based technologies, they can be focused on applications where the weight and footprint requirement is less drastic, such as electrical grid storage. Much work has to be done in the field of Na-ion in order to catch up with Li-ion technology. Cathodic and anodic materials must be optimized, and new electrolytes will be the key point for Na-ion success. This review will gather the up-to-date knowledge about Na-ion battery materials, with the aim of providing a wide view of the systems that have already been explored and a starting point for the new research on this battery technology.
Article
Novel K5-xTlx(Mg0.5Hf1.5)(MoO4)6 (0 ≤ х ≤ 5) oxides were successfully synthesized by solid state reaction. The results indicate the formation of a continuous series of solid solutions with the NASICON-like structure (sp. gr. R3¯c) in the composition range 0 < x < 5. The unit-cell parameters of the solid solutions increase linearly with composition, as a consequence of thallium substitution for potassium. The cation conductivity of Tl5Mg0.5Hf1.5(MoO4)6 has been shown to exceed the conductivity of the parent potassium magnesium hafnium molybdate. The highest total conductivity of 2.49 × 10⁻³ S/cm was found at 831 K for Tl5Mg0.5Hf1.5(MoO4)6.
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We report on the solid-state reaction (SSR) synthesis protocols and post-synthesis processing parameters of NASICON Na3Zr2Si2PO12 ceramic membranes prepared from Na2CO3 , SiO2 , ZrO2 , and NH4H2PO4 precursors. Characterization was conducted by optical microscopy, granulometry (DLS), porosimetry (BET/BJH), and X-ray diffractometry (XRD); electrical properties, i.e. electrical (dc) and ionic (ac) conductivity, were evaluated by impedance spectroscopic methods over the temperature range of 100°C to -100°C. Apart from NASICON composition, particular attention was focused on monitoring the role of post-synthesis processing parameters, i.e. sintering temperature and pellet-forming cold isostatic pressure, on the derived electrical properties. In-lab prepared samples were compared with commercial NASICON pellets serving as reference for controlling the electrical properties. NASICON samples prepared by the SSR route at stoichiometric ratios of the precursors, sintered at 1100°C, and assembled into pellet form by cold-pressing at 3500 kgF, reached the same level of ionic conductivity as the commercial reference. This work serves as the initial step on our ongoing research into superionic ceramic conductors and their possible applications in energy conversion and storage.
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Lithium and sodium (Na) mixed polyanion solid electrolytes for all-solid-state batteries display some of the highest ionic conductivities reported to date. However, the effect of polyanion mixing on ion transport properties is still debated. Here, we focus on Na 1+x Zr 2 Si x P 3-x O 12 (0 ≤ x ≤ 3) NASICON electrolyte to elucidate the role of polyanion mixing on Na-transport properties. Although there is a large body of data available on this NASICON system, transport properties extracted from experiments or theory vary by orders of magnitude, signifying the need to bridge the gap between different studies. Here, more than 2,000 distinct ab initio-based kinetic Monte Carlo simulations have been used to map the statistically vast compositional space of NASICON over an unprecedented time range and spatial resolution and across a range of temperatures. We performed impedance spectroscopy of samples with varying Na compositions revealing that the highest ionic conductivity (~ 0.1 S cm –1 ) is achieved in Na 3.4 Zr 2 Si 2.4 P 0.6 O 12 , in line with our predictions (~0.2 S cm –1 ). Our predictions indicate that suitably doped NASICON compositions, especially with high silicon content, can achieve high Na ⁺ mobilities. Our findings are relevant for the optimization of mixed polyanion solid electrolytes and electrodes, including sulfide-based polyanion frameworks, which are known for their superior ionic conductivities.
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The global shift of energy resources from fossil fuel to renewable energy sources has already begun. The critical energy element of lithium (Li) plays an important role in this energy transition, which is demonstrated by the fast increase in its demand. Rapid and continuous detection of Li has become an important field, as the overexploitation of Li sites, mainly brines, could compromise the nearby aqueous resources that are less salty or contain freshwater. Spent Li‐ion batteries also pose deleterious effects on the environment and aqueous resources. Monitoring of lithium in blood during treating major depressive disorders is also crucial for decreasing the risk of potential lithium toxicity. Li selectivity and stability of membranes as an essential part of any Li sensor is the key to fabricate a high‐performance Li ion‐selective electrode (ISE). Here, the latest progress in Li‐ISEs is covered along with the advanced nanostructured materials that have been recently used for the preparation of Li ion‐selective membranes. The new concepts and technologies that have been created for the purpose of Li mining to be used for Li sensing development are also critically reviewed and highlighted. The most important components of ion‐selective electrodes are membranes and the transducer layer. Conducting polymers, carbon and noble metals nanomaterials, and intercalated compounds have been used as ion‐to‐electron transducers for lithium ion‐selective electrodes that are coated by a selective membrane. Recent advances in lithium selective membranes e.g., metal‐organic frameworks, carbon‐based, vermiculite, MXene, and modified polyethylene terephthalate are comprehensively studied.
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We report enhanced Na-ion conductivity of Na3+xScxZr2-xSi2PO12 (x=0.2–0.5), prepared through solid-state reaction method with optimized sintering temperature of 1220 °C for 15 h. Among four compositions, Na3.4Sc0.4Zr1.6Si2PO12 offers highest total ionic conductivity of 2.6 mS/cm at 25 °C which is much higher than that of parent material. The Rietveld analysis of XRD data reveals a phase mixture of monoclinic and rhombohedral NASICON phases. NMR results indicates local disordering and a fast exchange of Na-ion between the different Na-sites. SEM observation reveals microcrack-free grain boundaries. An understanding of the underlying causes of higher conductivity has been achieved.
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Owing to low cost, high energy density and reliable safety, all‐solid‐state sodium batteries have been regarded as one of the most promising candidates beyond lithium‐ion batteries. Sodium super ionic conductor (NASICON)‐structured solid‐state electrolytes, with good electrochemical stability and environmental friendliness, are the potential candidate for solid‐state electrolytes. In this review, we summarize the basic properties of NASICON compounds, including structural characteristics, preparation methods, ionic conductivity, and the strategies, substituting proper elements, optimizing preparation approaches, increasing packing density, etc., to improve the bulk and grain boundary conductivity. Additionally, we also analyze the challenges and approaches for interfacial modification between electrodes and SSEs in solid‐state sodium batteries. Finally, the future research directions for facilitating the development of all‐solid‐state sodium batteries are proposed.
Article
Na3Zr2Si2PO12 (NZSP) is considered to be one of the most promising solid electrolytes for solid-state sodium batteries. However, low ionic conductivity of NZSP is one of the main challenges for its practical application. Herein, an F- assisting strategy to improve the ionic conductivity of NZSP is proposed. The F- assisting in NZSP electrolyte promotes formation of microstructure with large grains, low grain boundary concentration and high relative density, which is favorable to obtain high ionic conductivity. Consequently, the F--assisted NZSP solid electrolyte exhibits a high ionic conductivity of 1.41×10-3 S cm-1 at 27 oC, which is about six times that of un-assisted NZSP electrolyte (2.32×10-4 S cm-1). Moreover, the Na/Na3V2(PO4)3 solid-state sodium battery with F--assisted NZSP electrolyte exhibits an excellent cyclability with 97.8% capacity retention (85.9 mAh g-1 ) after 100 cycles at 0.5 C at 40 oC. This F- assisting strategy provides a new way for the development of other classes of ceramic solid electrolytes for solid-state batteries.
Article
In this study, synthesis of NASICON powder by coprecipitation and sol-gel processes is described and effect of process conditions and calcination temperature on crystallinity is investigated. X-ray diffraction patterns show that the coprecipitation method leads to formation of NASICON pure phase with a negligible zirconia content and so the powder derived thorough coprecipitation is used for sintering. Sintering is carried out in two methods. In conventional method, NASICON pellets are sintered at different temperatures and holding time. Results reveal that the pellet sintered at 1000 °C for 10 h yields better electrochemical properties. Spark plasma sintering was also performed which results the highest conductivity of 1.7 × 10⁻³ S cm⁻¹ between all samples at 25 °C.
Article
Because of the poor sintering ability and low phase purity limit in the application of a Na3Zr2Si2PO12 solid electrolyte, it is important to find an effective way to obtain a pure and dense Na3Zr2Si2PO12 ceramic at reduced temperature. In this study, high conductive indium-tin oxide (ITO) was innovatively used as the sintering additive to improve the purity and density of the Na3Zr2Si2PO12 ceramic. The influence of ITO additive on density, phase, microstructure and conductivity of the Na3Zr2Si2PO12 ceramic was investigated. Archimedes method, x-ray diffraction, scanning electron microcopy and complex impedance spectroscopy were used as experimental techniques to evaluate the effect of the additive. The results show that the ITO sintering additive increases not only the purity and density but also the conductivity of the Na3Zr2Si2PO12 ceramic. The Na3Zr2Si2PO12 ceramic with 3 wt.% ITO additive sintered at 1150°C for 4 h possesses a high density of 3.15 g/cm³ and good conductivity of (3.95 ± 0.12) × 10⁻⁴ S/cm.
Article
Sodium zirconium silicon phosphorus with the composition of Na3Zr2Si2PO12 (NZSP) was prepared by a facile solid state reaction method. The effects of the calcination temperature and rare earth element substitution on the structure and ionic conductivity of the NZSP material were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and AC impedance measurement. The results show that the microstructure and ionic inductivity of the NZSP was strongly affected by the aliovalent substitution of Zr⁴⁺ ions in NZSP with rare earth metal of La³⁺, Nd³⁺ and Y³⁺. At room temperature, the optimum bulk and total ionic conductivity of the pure NZSP solid electrolyte sintered under different conditions were 6.77×10⁻⁴ and 4.56×10⁻⁴ S cm⁻¹, respectively. Substitution of La³⁺, Nd³⁺ and Y³⁺ in place of Zr⁴⁺ exhibited higher bulk conductivity compared with that of pure NZSP. Maximum bulk and ionic conductivity value of 1.43×10⁻³ and 1.10×10⁻³ S cm⁻¹ at room temperature were obtained by Na3+xZr1.9La0.1Si2PO12 sample. The charge imbalance created by aliovalent substitution improves the mobility of Na⁺ ions in the lattice, which leads to increase in the conductivity. AC impedance results indicated that the total ionic conductivity strongly depends on the substitution element and the feature of the grain boundary.
Article
The successful analysis on the microstructure of Hong-type Na superionic conducting (NASICON) ceramics revealed that it consists of several heterogeneous phases: NASICON grains with rectangular shapes, monoclinic round ZrO2 particles, grain boundaries, a SiO2-rich vitrified phase, Na-rich amorphous particles, and pores. A dramatic microstructural evolution of NASICON ceramics was demonstrated via an in situ analysis, which showed that NASICON grains sequentially lost their original morphology and were transformed into comminuted particles (as indicated by the immersion of bulk NASICON samples into seawater at a temperature of 80 °C). The consecutive X-ray diffraction analysis represented that the significant shear stress inside NASICON ceramics caused their structural decomposition, during which H3O⁺ ions occupied ceramic Na⁺ sites (predominantly along the (1̅11) and (1̅33) planes), while the original Na⁺ cations came out in the (020) plane of the NASICON ceramic crystalline structure. The results of time-of-flight secondary-ion mass spectrometry analysis confirmed that large concentrations of Cl– and Na⁺ ions were distributed across the surface of NASICON ceramics, leading to local densification of a 20 μm thick surface layer after treatment within seawater solution at a temperature of 80 °C.
Article
The Na superionic conductor (aka Nasicon, Na1+xZr2SixP3-xO12, where 0 ≤ x ≤ 3) is one of the promising solid electrolyte materials used in advanced molten Na-based secondary batteries that typically operate at high temperature (over ∼270 °C). Nasicon provides a 3D diffusion network allowing the transport of the active Na-ion species (i.e., ionic conductor) while blocking the conduction of electrons (i.e., electronic insulator) between the anode and cathode compartments of cells. In this work, the standard Nasicon (Na3Zr2Si2PO12, bare sample) and 10 at% Na-excess Nasicon (Na3.3Zr2Si2PO12, Na-excess sample) solid electrolytes were synthesized using a solid-state sintering technique to elucidate the Na diffusion mechanism (i.e., grain diffusion or grain boundary diffusion) and the impacts of adding excess Na at relatively low and high temperatures. The structural, thermal, and ionic transport characterizations were conducted using various experimental tools including X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS). In addition, an ab initio atomistic modeling study was carried out to computationally examine the detailed microstructures of Nasicon materials, as well as to support the experimental observations. Through this combination work comprising experimental and computational investigations, we show that the predominant mechanisms of Na-ion transport in the Nasicon structure are the grain boundary and the grain diffusion at low and high temperatures, respectively. Also, it was found that adding 10 at% excess Na could give rise to a substantial increase in the total conductivity (e.g., ∼1.2 × 10⁻¹ S/cm at 300 °C) of Nasicon electrolytes resulting from the enlargement of the bottleneck areas in the Na diffusion channels of polycrystalline grains.
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Polycrystalline Na3+xScxZr2-x(SiO4)2 (PO4) (NSZSPx, x = 0—0.6) are fabricated on a laboratory scale (10 g—1 kg) by precipitation from stoichiometric aqueous solutions of NaNO3, Sc2O3, ZrO(NO3)2, Si(O-Ac)4, and NH4H2PO4 followed by calcination (800 °C, 3 h), ball milling (2 d), and final sintering (1250—1300 °C, 5 h).
Article
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As possible electrolyte materials for all-solid-state Na-ion batteries (NIBs), scandium-substituted Na3Zr2(SiO4)2(PO4) in the structure of NASICONs (Na super-ionic conductors) have received hardly any attention so far, although among all the trivalent cations, Sc3+ might be the most suitable substitution ion for Na3Zr2(SiO4)2(PO4) because the ionic radius of Sc3+ (74.5 pm) is the closest to that of Zr4+ (72.0 pm). In this study, a solution-assisted solid-state reaction (SASSR) method is described and a series of scandium-substituted Na3Zr2(SiO4)2(PO4) with the formula of Na3+xScxZr2-x(SiO4)2(PO4) (NSZSPx, 0 ≤ x ≤ 0.6) have been prepared. This synthesis route can be applied for powder preparation on a large scale and at low cost. With increasing degrees of scandium substitution, the total conductivity of the samples also increases. An optimum total Na-ion conductivity of 4.0 × 10-3 S cm-1 at 25 °C is achieved by Na3.4Sc0.4Zr1.6(SiO4)2(PO4) (NSZSP0.4), which is the best value of all reported polycrystalline Na-ion conductors. The possible reasons for such high conductivity are discussed.
Article
Research and development efforts on sodium-ion batteries are gaining momentum due to their potential to accommodate high energy density coupled with relatively lower cost in comparison with lithium-ion batteries. In order for the sodium-ion batteries to be commercially viable, high performance electrolytes with acceptable ambient temperature ionic conductivity and wider electrochemical stability windows are being developed. A bibliometric analysis of the publications on various types of Na+ ion conducting electrolytes since 1990 shows a total of 200 + publications and reveals an exponential growth in the last few years, due to reasons that the sodium-ion systems promise great potential as the future large scale power sources for variety of applications. This review consolidates the status of liquid (non-aqueous, aqueous and ionic), polymer gel and solid (ceramics, glasses, and solid polymers) electrolytes and discusses their ionic conductivity, thermal characteristics, electrochemical stability and viscosity towards applications in sodium-ion batteries. Among various types available, the non-aqueous solvent based electrolyte is the most promising one in terms of ionic conductivity even though it is flammable.
Chapter
Sodium–sulfur (Na–S) battery technology has high potential for energy storage and load leveling in power systems, and it is one of the most developed types of high temperature battery. Owing to outstanding energy density, high efficiency of charge/discharge, low materials cost, and cycle life of up to 15 years, Na–S batteries are attractive for their use in relatively large-scale energy storage system applications. However, there are several challenges to overcome for the safe operation of Na–S batteries, mostly related to the high operation temperatures. In this sense, the development of new solid electrolytes that possess high ionic conductivities at intermediate or room temperature is crucial. β-Alumina and NASICON structure electrolytes are revised, and new alternatives, such as ceramic/polymer composites, are also gathered. There also exists novel focus on Na–S technology in order to increase the obtained capacity and cyclability consisting of using nanostructured carbon to host sulfur or to bind it to a polymer. In addition, hybrid technologies combining Na–S with ZEBRA or oxygen rocking-chair batteries are currently arising as alternative storage devices. As Na–S technology was introduced in the mid-1970s, a number of different patents have been developed. Trends observed in the new patents are twofold: on the one hand, they aim to integrate these batteries into the electrical grid in order to compensate the fluctuations of renewable energies; on the other hand, they show battery component improvements in order to obtain lower operating temperatures. Keywords: batteries; Na–S; Li–S; β-alumina; β″-alumina
Article
NASICON-structured Na3Zr2Si2PO12 was synthesized by a Sol-Gel approach. Phase-pure samples were successfully sintered at 1050°C when adding 10% excessive Na and P in the precursors, while a small amount of ZrO2 impurity was detected without adding excessive phosphorus. Electrochemical impedance spectrum tests indicate that the ionic conductivity of the former is as high as 5.4×10-4 S/cm at room temperature, which is higher than that of samples prepared from the precursors without adding excessive phosphorus (3.7×10-4 S/cm). Further analysis reveals that the evaporation of phosphorus at high temperature would cause the formation of ZrO2 impurity in the samples, leading to a lower ionic conductivity. Compared with solid state reaction approach, samples with enhanced ionic conductivity can be obtained at a rather lower temperature by Sol-Gel synthesis.
Article
The nanocrystalline NASICON powders have been synthesized by sol–gel route and structural and optical properties have been investigated. The effect of increase in sintering temperature (800 to 1000 °C) on crystallite size and band gap has been investigated which shows increase in crystallite size, shift in the band gap towards higher energy from to 3.90 to 5.25 eV for direct transition and from 3.58 to 4.90 eV in indirect transition. The XRD results show the presence of impurity phases along with NASICON phase and compositional variation with temperature. TEM results confirm the variation in particle size. Single phase of NASICON nanopowders were prepared by varying sintering time. XRD, TEM and transmittance results showed presence of single phase and nanocrystalline nature of the particles. The shift in band gap from 4.91 to 5.25 eV for direct transition and 4.30 to 4.90 eV for indirect transition towards higher energy side with decrease in particle size can be attributed to size effect. Results indicate that structural and optical properties can be easily modulated significantly by altering particle size and sintering temperature during synthesis.
Article
One important issue in future scenarios predominantly using renewable energy sources is the electrochemical storage of electricity in batteries. Among all rechargeable battery technologies, Li-ion cells have the largest energy density and output voltage today, but they have yet to be optimized in terms of capacity, safety and cost for use as stationary systems. Recently, sodium batteries have been attracting attention again because of the abundant availability of Na. However, much work is still required in the field of sodium batteries in order to mature this technology.Sodium superionic conductor (NASICON) materials are a thoroughly studied class of solid electrolytes. In this study, their crystal structure, compositional diversity and ionic conductivity are surveyed and analysed in order to correlate the lattice parameters and specific crystal structure data with sodium conductivity and activation energy using as much data sets as possible. Approximately 110 compositions with the general formula Na 1 + 2 w + x - y + z Mw(II)Mx(III)My(V) M2- w - x - y (IV) (SiO4)z(PO4) 3 - z were included in the data collection to determine an optimal size for the M cations. In addition, the impact of the amount of Na per formula unit on the conductivity and the substitution of P with Si are discussed. An extensive study of the size of the structural bottleneck for sodium conduction (formed by triangles of oxygen ions) was carried out to validate the influence of this geometrical parameter on sodium conductivity.
Article
The samples of tin (Sn) modified NASICON (Na3Zr2Si2PO12) type solid electrolyte are prepared and their electrical properties are investigated. The two modified compositions of NASICON in which zirconium (Zr) atoms are replaced by Sn atoms i.e., Na3ZrSnSi2PO12 (NASN) and Na3Sn2Si2PO12 (NASN2), are prepared by solid state reaction technique. The structural studies show variation in the lattice parameters a and c which enhance the bottle neck size. The FT-IR results also confirm structural modification (stretching of bond lengths) on addition of Sn. The electrical studies show when one atom of Zr is replaced by one atom of Sn (NASN), both DC and AC electrical conductivities increase as compared to unmodified NASICON material while for replacement of both the Zr atoms by Sn atoms (NASN2), the electrical conductivity decreases.
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The progress in the research and development of high temperature sodium batteries suggests that all-solid-state batteries with inorganic or polymer solid electrolytes are promising power sources for a wide range of applications due to their high thermal stability, reliability, long-cycle life and versatile geometries. The electrolytes play a fundamental role in terms of current (power) density, the time stability, and the safety of batteries and, as a result, their continuous improvement and innovation are indeed critical to success. In fact, inorganic solid electrolytes pave the way for improving the cost-effective development of rechargeable sodium batteries. This review describes a state-of-the-art overview of most of the Na+ conductors for use as electrolytes in sodium/sulphur and ZEBRA batteries. The emphasis of this article is on inorganic solid electrolytes, especially, ceramic and glass-ceramic electrolytes as promising alternatives applicable to all solid-state batteries. As part of a continuous effort to find new materials that operate at room temperature and moderate temperatures, NASICON electrolytes will also be considered. Polymer electrolytes based on poly(ethylene oxide) (PEO) are also very suitable for all solid-state batteries. Hence, the review focuses on ion transport based on the observed conductivity, electrolyte preparation, safety and environmental impact.
Article
Phosphosilicate molecular precursor for the synthesis of NASICON, natrium super ionic conductor, Na1+xZr2SixP3-xO12 (x ) 1 and 2) has been devised and prepared by the hydrolysis of tetraethoxysilane (TEOS) employing sodium phosphate solution. The molecular precursor was reacted with Zr(OC3H7)4 in ethanol under solvolytic condition to yield nano precursor material of NASICON. This material was annealed at high temperature to yield phase-pure NASICON. The molecular precursor was characterized using 31P NMR, FTIR spectral data, powder XRD pattern and TG/DTA studies. The structure of the molecular precursor was deduced from the powder XRD data, which indicates the presence of edge sharing tetrahedral arrangement of -O-Si-O-P-O-Si- chain. The NASICON precursor material was characterized using TG/DTA, FTIR, TEM, SEM, MAS 31P NMR and XRD. The conductivity of the synthesized NASICON material was measured using the pellet annealed at 900 °C and was found to be 5.5 x10-3 S cm-1. The details on the preliminary investigation are presented in this paper.
Article
Ti4+ ion substitution ranges for Zr4+ ion have been investigated in the Na1 + xZr2SixP3 − xO12 (NASICON) system synthesized by a conventional solid state reaction using inorganic compounds at the reaction temperatures of 1000, 1100 and 1200 °C. The Ti4− ion substitution rate was greater in the phosphate-rich region than in the silicate-rich region. In the silicate end member, the Ti4− ion substitution rate and the melting temperature decreased with increasing Ti4− ion content of the starting materials. In the narrow range around x ~ 2.5, at low Ti4− ion content and at low temperatures, the Na2ZrSi2O7 phase segregated. Essentially the same results, except for the Na2ZrSi2O7 phase, have been shown when the NASICON compounds were synthesized by a conventional sol-gel technique using metal alkoxides.
Article
The Na(2+x+y)Zr(1-y)Fe(II)(x)Fe(III)1-x+y(PO4)3 solid solution with NASICON-type structure (R3BARc) occurs for y = 0 (0 less-than-or-equal-to x less-than-or-equal-to 1) and x+y = 1 (0 less-than-or-equal-to y less-than-or-equal-to 0.5). Electrical conductivity reaches a maximum for Na2.3ZrFe(II)0.3Fe(III)0.7(PO4)3 (sigma-300-degrees-C = 4 x 10(-3) S cm-1, ionic transport number tau-i = 0.95) and for Na3Zr0.67Fe(II)0.67Fe(III)0.67(PO4)3 the ionic and electronic components are equal. For Na(2+x)ZrFe(II)(x)Fe(III)1-x(PO4)3 solid solution the nearness of ionic and electronic activation energies seems to be fortuitous.
Article
Crystal determinations of the rhombohedral phase (space group R3c), for different compositions (2 < x < 2.4) in the true NASICON solid solution Na1+xZr2SixP3-xO12, have been performed at different temperatures by X-ray diffraction. We observe, as a consequence of interionic repulsions, the partial occupation of a mid-Na interstitial site within the conduction path. The composition dependence of the mid-Na occupation factor, maximum at x = 2, explains the maximum of the c hexagonal parameter and of the Na(1)-oxygen average distance observed at about x = 2. Moreover, structural results clearly suggest that the enhanced conductivity at x = 2 arises from sodium interactions instead of geometry changes of the framework.
Article
Various compositions (x from 1 to 3) were obtained from chemically coprecipitated powders. The 1.6 < x < 2.2 compositions display a phase transformation, from monoclinic to rhombohedral around 200°C; this transformation leads to a singularity on the resistivity curves and on the thermal expansion graphs.
Article
A second order phase transition has been found in Na3Zr2Si2PO12 by three independent techniques 1. i. Electrochemical investigations including ac-impedance technique showed a reversible change in the activation energy for Na-ion conduction from 34.2 kJ mol-1 at temperatures below 425 K to 20 kJ mol-1 for higher temperatures. 2. ii. Specific heat measurements show a clear indication of a phase transition at 420 K with ΔH = 2.07 kJ mol-1. 3. iii. High temperature X-ray diffraction powder patterns reveal a change from the monoclinic into the rhombohedral phase at the transition point.
Article
Solid-electrolyte sensors using NASICON for detecting CO2 gas are prepared by the sol-gel method. Starting materials are the alkoxides Si(OC2H5)4, Zr(OC2H7)4 and NaOC2H5. Because of their fine powders, the sintering temperature can be low. The phase identification is carried out by X-ray diffractometry (XRD). E.m.f. cells are constructed by fixing the NASICON disk to the end of a quartz tube with an inorganic adhesive. The devices with (Li, Ba)CO3 as sensing electrode and air as reference electrode show high sensitivity to 300–5000 ppm CO2 gas and good stability for a sintering temperature of 1000 °C.
Article
Conductivity measurements have been performed on the solid solution series, Na(3)Zr(2 - x/4)Si(2 - x)P(1 + x)O(12), for 0 < x < 2. These materials are Zr-deficient nasicon. A monoclinic to rhombohedral phase transition occurs around x = 0.333. The variation of the ionic conductivity as a function of the composition x is investigated in the temperature range 150-600 K. It is shown that the bulk ionic conductivity decreases slightly from 6 x 10(-4) S cm(-1) for the Zr non-deficient nasicon (x = 0) to 6 x 10(-5) S cm(-1) for the Zr highest-deficient material (x = 1.667). The presence of the above mentioned structural change does not affect the ionic conductivity. The mobility of the Na(+) ions in these materials seems to be mostly influenced by the size of the bottlenecks through which the ions have to pass. The variations of both the ionic conductivity and the activation energy of the ionic motion process in the bulk of the material can be explained by structural considerations.
Article
The admittance spectra of NASICON samples, Na1+xZr2SixP3-xO12 (0<x<3), were investigated for compositions 1.2<x<2.2 in the frequency range from 1 Hz to 150 kHz. It was found that the spectra consist of three regions of dispersion independent of the composition of the sample. The low frequency semicircle of the admittance spectra is attributed to the dispersion on electrode double layers connected in series to the total dc electric resistance of the sample. The high frequency semicircle-like part of the spectra is composed of two dispersions. One is attributed to the partial blocking of ion carriers on grain-boundary phases and the other to dispersion on a glassy phase present in inter-grain regions of NASICON samples. The plausibility of such an assumption is confirmed by the results of an additional investigation of admittance spectra of Co-doped NASICON samples in which the glassy phase was found to be extremely strong and endurable. Although the investigated samples differ greatly in their composition (from x = 1.2 to x = 2.2) the electric conductivity of their glassy phase obeys the Meyer-Neldel rule. This seems to indicate that the composition of the glassy phase is quite homogeneous over a range of NASICON-like compounds.
Article
The crystal structure of the ionic conductor Na4Zr2Si3O12 was reinvestigated at room temperature (RT), 300 and 620°C. Very little change occurs in the rigid (Zr2Si3O12)4− framework, but enlargement of the diameter of one of the Na(2)-Na(2) diffusion pathways. Analysis of the thermal vibration components of the Na(1) and Na(2) sites clearly demonstrates that the two sites are not energetically equivalent. Electron density maps and difference Fourier analysis at RT, 300 and 620°C confirmed that the pathway between the Na(2) and Na(2) is the main diffusion path, and that exchange between the Na(1) and Na(2) sites remains moderate even at 620°C. In addition, a direct relationship between the value of the conductivity and the size of the c parameter (hexagonal cell) has clearly been established in the solid solution Na1+xZr2SixP3−xO12 (x=0–3).
Article
Mixed crystals of the Nasicon composition Na1+xZr2SixP3-xO120.4≤x≤2.8 cannot be prepared as pure monophases because free ZrO2 always occurs as an impurity. In this paper a new solid solution is presented which is defined by the end compounds NaZr2P3O12 and Na4ZrSi3O10. Mixed crystals of the composition Na1+xZr2-x 3SixP3-xO12-2x 3 exhibit a pure monoclinic symmetry for 1.55≤x≤3, these compounds are stable with molten sodium and have a sodium ion conductivity comparable to that of the best materials available today.
Article
Ti4+ ion substitution ranges for Zr4+ ion have been investigated in the Na1 + xZr2SixP3 − xO12 (NASICON) system synthesized by a conventional solid state reaction using inorganic compounds at the reaction temperatures of 1000, 1100 and 1200 °C. The Ti4− ion substitution rate was greater in the phosphate-rich region than in the silicate-rich region. In the silicate end member, the Ti4− ion substitution rate and the melting temperature decreased with increasing Ti4− ion content of the starting materials. In the narrow range around x ~ 2.5, at low Ti4− ion content and at low temperatures, the Na2ZrSi2O7 phase segregated. Essentially the same results, except for the Na2ZrSi2O7 phase, have been shown when the NASICON compounds were synthesized by a conventional sol-gel technique using metal alkoxides.
Article
The structure of several monoclinic crystals of true NASICON-type materials Na1+xZr2P3−xSixO12 are examined at room temperature and 400 K. Two types of ion-ion correlation are observed. Type I corresponds to an ideal composition x=2; it is closely related to the monoclinic modification of α-Na3Sc2(PO4)3; ferroelectric-type order with four kinds of occupied Na sites: Na(1), regular Na(2)′, displaced Na(3)′ and mid-Na. Disordering resulting from both P/Si substitution and from nonstoichiometry screening of the long-range order leads to a residual occupancy of the regular Na(1) site. Type II, present for x≥2.25, corresponds to an anti-ferroelectric local order with three types of occupied Na sites: Na(1), regular Na(3)′ and mid-Na. The Na(2)′ site is empty. There is again only a residual occupancy of the Na(1) site. The existence of an interstitial mid-Na site establishes that the ion-ion correlations provide an essential part to the site potentials and that the driving mechanism for the phase transition is principally due to the modification of the host-lattice polarization by the conducting ions.
Article
The ionic conductivity of ceramic samples of NASICON was investigated by the use of the complex admittance method. Measurements were made in the frequency range 5−5×105 Hz from room termparature (RT) up to 400°C. The existence of three activation energies for both the bulk and the grain boundary conductivities is reported. A diffusive Warburg-like behaviour of electrical conductivity was revealed at temperatures where the value of the bulk conductivity approaches that of the grain boundary.
Article
Single crystals of various compositions in the system Na1+xZr2P3-xSixO12 have been prepared by graingrowth in sol/gel ceramics. For all the single crystal determinations (X-ray diffraction), evidence of the total occupancy of the Zr octahedron is found, unambiguously demonstrating that our crystal belong to solid solutions in which only the Si/P non stoichiometry is present. In the range 2<x<2.4, the monoclinic-rhombohedral phase transition implies the destruction of a local ferroelectric order and enhances the thermal vibration amplitudes of Na(1) and mid-Na. Concerning the composition effect, structural determinations show competing effects of static lattice potential and ion interactions. The Coulomb forces shirt a part of Na(1) ions into mid-Na interstitial positions and the conductivity is directly related to the occupation factor of the mid-Na position (maximum at x=2).
Article
Nasicon and Titzicon compositions have been obtained as powders or monolithic, optically clear gels by sol-gel processes. Variations of the synthesis method have been explored by changing the proportion of metal organic reagents and the hydrolysis rate. The structural evolution as a function of temperature can be correlated with the specific area variations: the Nasicon phase is gradually formed between 800 and 1050°C. The target compositions were achieved with only a small Zr deficiency. The previously reported rhombohedral → monoclinic (R/M) transition is only observed in materials manufactured above 1100°C where traces of monoclinic zirconia also appear. Higher sintering temperatures give better defined R/M transitions, which shift to higher temperatures. Titzicon preparations, however, contain much vitreous phase (30%).Well-densified (>96%) Nasicon ceramics can be obtained by fast sintering (>200°C/h) at low temperatures (<900°C); thin specimens are optically translucent. However, it is necessary to establish a balance between lowering sintering temperatures and maintaining the target structural state (and properties).
Article
This work reports on the synthesis and characterization of NASICON obtained from solid state reaction between SiO2, Na3PO4·12H2O and two types of zirconia: monoclinic ZrO2 and yttria-doped tetragonal phase (ZrO2)0.97(Y2O3)0.03. Powders and dense samples were characterized by SEM, XRD and DTA. Electrical conductivity was measured by impedance spectroscopy. Results obtained with different NASICON samples showed a significant role of composition and processing conditions on the electrical properties. Dense yttria-doped samples were obtained at a lower temperature than the undoped material. The electrical conductivity, close to 2×10−3 S cm−1 at room temperature, is significantly higher than the value obtained with the material prepared from pure ZrO2. Attempts to compensate the charge unbalance due to replacement of Y3+ for Zr4+ with additions of Na+ failed. Instead, a drop in electrical conductivity due to an enhancement of the grain boundary impedance was observed. Formation of monoclinic zirconia and glassy phases along the grain boundary were responsible for this effect. Results suggest a major role of microstructure on electrical properties rather than composition.
Article
Thick films of NASICON (Na+ conductor, Na3Zr2Si2PO12) were prepared for the fabrication of a planar CO2 sensor. The powder of a precursor of NASICON, derived through a sol–gel process, was screen-printed on an alumina substrate and converted into a NASICON thick film by calcination. The formation of crystalline NASICON was almost complete after calcination at 900 and 1000°C, but the films remained rather poor in densification. On the other hand, the films were densified after calcination at 1100°C or above, but NASICON phase disappeared by decomposition. The planar CO2 sensor device was thus fabricated by using the NASICON thick film (30 μm thick) calcined at 1000°C. The device attached with a binary carbonate auxiliary phase (Li2CO3–BaCO3) showed fairly good CO2 sensing properties at 450–600°C, despite rather poor densification of the thick film used.
Article
High-conductivity and high-density samples with new compositions in the NASICON-type electrolyte series, i.e., the Na3Zr2−(x/4)Si2−xP1+xO12 system, with x=0(A), 0.667(B), and 1.333(C) were synthesized using a mixed inorganic–organic sol–gel process. The sinterability was improved with increasing the x value, but the conductivity decreased. Highly dense samples were obtained by sintering at 1100°C. The conductivity decreased with decreasing the c lattice parameter of the hexagonal structure. Nevertheless, the CO2 gas sensors using the highly dense B and C samples showed good EMF response which is very close to the theoretical value.
Article
A novel processing technique for the preparation of Na+ super ionic conductor (NASICON: Na3Zr2Si2PO12) thin films have been developed using an aqueous complex precursor derived from hydroxyacid-added aqueous solutions of all-inorganic materials. Spinnable viscous gel was obtained from a tartaric acid (TA)-added aqueous solution after holding the temperature at 2°C for 7 days . NASICON thin films could be fabricated onto alumina substrates by spin-coating the TA-based viscous gel, drying at 150°C, and sintering at 1000°C for 3 h.
  • D D Lee
  • S D Choi
  • K W Lee
D.D. Lee, S.D. Choi, K.W. Lee, Sens. Actuators B 24/25 (1995) 607-609.
  • J P Boilot
  • G Collin
[15] J.P. Boilot, G. Collin, Ph. Colomban, J. Solid State Chem. 73 (1988) 160–171.
  • Y Schimizu
  • T Ushijima
Y. Schimizu, T. Ushijima, Solid State Ionics 132 (2000) 143-148.
  • U Von Alpen
U. von Alpen, Mater. Res. Bull. 14 (1979) 1317-1322.
Solid State Ionics 28-30
  • J P Boilot
  • Ph
  • G Colomban
  • Collin
J.P. Boilot, Ph. Colomban, G. Collin, Solid State Ionics 28-30 (1988) 403-410.
  • U Von Alpen
  • M F Bell
  • H H Hőfer
U. von Alpen, M.F. Bell, H.H. Hőfer, Solid State Ionics 3/4 (1981) 215-218.