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INFLUENCE OF SILVER OXIDE ON STRUCTURAL, PHYSICAL, ELASTIC AND OPTICAL PROPERTIES OF ZINC TELLURITE GLASS SYSTEM FOR OPTICAL APPLICATION
Abstract
The research on several properties of erbium-doped zinc tellurite glass system is thoroughly investigated recently. However, the introduction of silver oxide as a dopant plays a role on the fabrication of new optical materials specifically in optical application. By conducting the investigation, the use of melt-quenching technique is one of the techniques to fabricate a series of silver-doped zinc tellurite glass systems with the chemical composition of [[(TeO 2) 0.7 (ZnO) 0.3 ] 0.96 (Er 2 O 3) 0.04 ]] 1-x (Ag 2 O) x at different molar fraction of x = 0.01, 0.02, 0.03, 0.04 and 0.05. The characterization of X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, density, elastic and optical measurements were investigated to analyse the prepared glass samples. The result of the XRD, FTIR, density, elastic and optical properties were all reported at the room temperature. The glass samples are proven as amorphous in nature which can be seen by the XRD spectra. Besides that, the presence of functional vibration of tellurite network can be clearly observed through the analysis of FTIR spectra. The density of the glass system is found to increase with the increase of silver oxide concentration. Anyhow, the value of molar volume is noticed to be inversely proportional to the density. Therefore, the inclination in the density value causes the decrement of the molar volume which can be associated with the inclusion of silver oxide in the glass system. Plus, this also follows the theoretical formula where the density is equivalent to molar mass per molar volume. In the meantime, the ultrasonic velocity was employed in order to specify the elastic moduli of the glass systems. The elastic moduli for instance longitudinal modulus, shear modulus, bulk modulus, Young's modulus as well as other parameters come out with a varying trend against the concentration of silver oxide. The increment of the elastic moduli can be attributed to the high connectivity and rigidity of the glass structure. Nonetheless, the decrement of the elastic moduli can be associated with the breakage of bonds within the zinc tellurite glass system which impair the structure of the glass sample. The UV-Vis analysis can determine the optical properties of the prepared glass samples. The optical absorption was reported at room temperature within the wavelength ranging from 200 to 2000 nm. The optical absorption spectra unveil the fundamental absorption edge shifts to longer wavelength as the content of silver oxide increases. The values of direct and indirect band gap and metallization criterion have been evaluated and noticed to have a decreasing trend with the increasing content of silver oxide whereas the Urbach energy, refractive index, molar refraction, molar polarizability, oxide ion polarizability and optical basicity are obviously increasing as the concentration is included into the glass system.
... The stretching vibration of the Te-O bond places the infrared properties of the two kinds of tellurium oxide structural units in the 600-700 cm -1 region. TeO4's trigonal bipyramidal structural unit band has a wavelength of 600-650 cm -1 [12], [21]- [23]. ...
Nanomaterials based on graphene have outstanding properties, particularly in terms of optical performance. Using melt-quenching and low-cost spray coating procedures, we effectively generated a series of reduced graphene oxide-coated tellurite glasses doped with neodymium nanoparticles, denoted as rGO-ZBTNd (NPs) glasses. An X-ray diffraction study of glass samples validated the glass system's amorphous structure. FESEM morphological analysis was used to evaluate the appearance of rGO on the glass substrate and revealed the dispersion of rGO. UV-Vis spectroscopy was used to determine different absorption bands. The refractive index value calculated using the Dimitrov and Sakka equation was found to be more than n > 2.000 and in the range of 2.339 to 2.657 when compared to uncoated samples. On the basis of these findings, a new method involving rGO deposited on tellurite glass has been developed to improve the tellurite glass currently utilised in laser applications.
... The stretching vibration of the Te-O bond places the infrared properties of the two kinds of tellurium oxide structural units in the 600-700 cm -1 region. TeO4's trigonal bipyramidal structural unit band has a wavelength of 600-650 cm -1 [12], [21]- [23]. ...
... The optical absorption spectra of GO coated TNd (NPs) glasses were presented in Figure 6. XRD analysis revealed that the absorption spectra edges in glass samples are not strongly defined, indicating a non-crystalline/amorphous structure [18]- [20]. There are several peaks that emerge from the ground state ( 4 I 9/2 ) to the excited state. ...
The versatility of graphene oxide (GO) as coating materials on the glass surface is a new revolution in the advanced glass era. In this work, GO liquid solution was prepared by using electrochemical exfoliation in an electrolyte solution assisted by different surfactants. Meanwhile, a glass series was prepared by using the conventional melt-quenched technique. A low-cost and simple spray deposition technique was used to deposit the GO on the glass sample. The obtained glass series was denoted as GO coated TNd (NPs), meanwhile, the uncoated glass was labelled as uncoated TNd (NPs). The linear optical properties of GO coated TNd (NPs) glass series was determined using UV-Vis spectrophotometer and utilizing the Lorentz-Lorentz equation to determine the value of polarizability. X-ray diffraction spectra revealed the amorphous structural characteristics of the glass series. The SEM morphological image revealed the variation of GO distribution on the glass surface due to the agglomeration and inhomogeneity of GO distribution on the glass surface. The homogeneity of GO distribution on the glass surface is negligible in this work as we focus solely on the effect of GO on glass properties. According to the observations, the value of GO-coated TNd (NPs) is in the range 3.4531-3.8549 Å and uncoated TNd (NPs) is in the range 2.709-2.774 Å. Meanwhile, the optical basicity value ranges from 1.220 to 1.262. These results demonstrate that the polarizability of oxide ions and optical basicity values of the GO coated TNd (NPs) glass series was higher than the uncoated TNd (NPs) glass. The metallization criterion for the GO-coated TNd (NPs) glass system is in the range of 0.3 < M < 0.4. Based on these results, the obtained glasses are promising in linear optical glass fibre.
... The incorporation of a huge molecular weight of erbium oxide (382.52 and silver oxide (231.74 g) will enhance the density of the glass system as compared to tellurium oxide (159.60 g) and zinc oxide (81.38 g) [74]. Besides that, the increased density is due to more oxygen, which diverts the trigonal pyramid into the trigonal bipyramid [75]. The presence of the trigonal pyramid and trigonal bipyramid is proven through FTIR and deconvolution result that can be strongly related to the formation of NBO and BO in the glass system. ...
Melt-quenching method was used to synthesize a series of zinc tellurite glasses doped with erbium oxide and silver oxide. At room temperature, X-ray diffraction (XRD) and density measurement were implemented to characterize the prepared glass samples. The amorphous nature of the glass samples is proven from the XRD spectra obtained in this work. The density of the glass showed an increment trend from 4.4673 to 4.9705 g/cm ³ when adding more silver oxide, which can prove that the glass strength is higher. For photoluminescence analysis, blue, green and red emissions were found in the glass series under 375 nm excitation wavelength. According to McCumber theory, higher emission cross-section and higher FWHM are efficient for both broadband amplifier and laser application. More extensive and flatter gain with a maximum gain difference has covered both C and L bands for optical communication, providing a few channels in the wavelength division multiplex network (WDM). The high efficiency of optical amplification is justified with a higher gain figure of merit and larger gain bandwidth. According to McCumber’s theory, all the results proved that 0.03 molar fraction of silver oxide is the most optimum concentration to be applied in the optical application. In Judd-Ofelt analysis, spectroscopic quality factor and shorter lifetime is a crucial parameter for obtaining intense laser transition, strong emission probabilities and encouraging the laser optical transition, which was successfully attained in all glass samples. The present glass system is also applicable for white light application since the standard equal energy point from all glass samples were located near the center of the CIE diagram (0.33, 0.33). In the meantime, higher values of CCT range from 6761 to 6937 K produce light with a better image as compared to lower CCT. Higher CCT is commercially used in LCD (liquid crystal display) and CRT (cathode ray tube) screens. The colour purity is a parameter for better white LED application, whereas low colour purity is for pure white light emission. Therefore, lower colour purity was found around 10.7 around 18.8% in all glass samples.
... The electronic transitions between the levels of 4f which are protected by two 5 s and six 5p particles are due to the Coulomb interaction between electrons, spin orbit coupling, and the local crystalline electric field and the splitting of these levels [43]. The optical absorption edges are not sharply defined in ZBTNd (NPs)-GO glasses which attributes to the noncrystalline/ amorphous nature as proved in XRD analysis [23][24][25]. The absorption peaks are centred at 432 nm ( 2 P1/2), 479 nm ( 4 G5/2 + 2 D3/2 + 2 K15/2), 515 nm ( 4 G9/2), 528 nm ( 2 K13/2 + 4 G7/2), 595 nm ( 2 G7/2 + 4 G7/2), 630 nm ( 2 H11/2), 683 nm ( 4 F9/2), 756 nm ( 4 S3/2 + 4 F7/2), 800 nm ( 4 F5/2 + 2 H9/2), and 881 nm ( 4 F3/2) [26][27][28]. ...
Carbon-based materials such as graphene oxide are known as attractive candidate to improve the current optoelectronic and laser devices. In this work, neodymium nanoparticles doped zinc-tellurite glass coated with graphene oxide (GO) denoted as ZBTNd (NPs)-GO was prepared via low-cost melt-quenching method and simple spray coating method. The structural properties of the glass system had been carried out by using X-ray diffraction (XRD) and confirmed its amorphous structural arrangement with non-existence of crystalline structure. The TeO3 and BO3 structural units were found dominant in tellurite glass network as determined by Fourier transforms infrared spectrometer (FTIR). High number of oxygen functional groups and stacked of graphene layers on the glass surface were revealed by field scanning electron microscopy (FESEM) and Raman spectroscopy. The optical band gap energy values were found to decrease in the range of 2.665–2.405 eV along with dopant concentration. In the meantime, the refractive index values were found more than n > 2.00 and fall in the range of 2.12 to 2.20. The electronic polarization was calculated by using Lorentz-Lorentz equation and found in the range of 6.516 to 7.211 Å ³. Based on these results, the improvements on optical properties of tellurite glass have been made to be used in laser application.
... The inclusion of erbium oxide in the glass sample play the crucial role of modifying oxide by altering the linkage of the tellurite (Te-O-Te) network. The alteration in the tellurium network includes the breaking of the pure tellurite network from TeO 4 (trigonal bipyramid) into TeO 3+1 polyhedral and then to the TeO 3 (trigonal pyramid) via the formation non-bridging oxygen atoms (NBOs) [32][33]36]. ...
Nowadays, active search for more efficient and improved glass material to be employed as laser host has been take place in order to have laser with enhanced performance. In this research, erbium oxide doped rice husk biosilicate zinc borotellurite glasses have been fabricated successfully via conventional melt quenching technique. XRD pattern reveals that the prepared glasses are amorphous in nature while FTIR spectra records the presence of Si-O-Si, TeO 3 , BO 4 as well as BO 3 vibrational groups in the fabricated glasses. Increasing density from 3.3505 g/cm 3 to 4.1852 g/cm 3 along with the rigidity of the glass as hinted in the values for elastic moduli from 55.0 GPa to 250.0 GPa is caused by the incorporation of erbium oxide that reduce the amount of non-bridging oxygen in the glass matrix. Three bands that are recorded in PL spectra correspond to the violet, blue and green emission.
A total of five zinc borotellurite glass samples containing with strontium oxide at various molar fractions of x = 0.01, 0.02, 0.03, 0.04 and 0.05 was prepared, utilizing the conventional melt-quenching technique. The chemical composition of the prepared glass samples can be presented using the formula of [(TeO2)0.7(B2O3)0.3)0.7(ZnO)0.3]1-x(SrO)x. The structural features of the samples were analysed by using the X-ray Diffraction (XRD) spectroscopy and Fourier Transform Infrared (FTIR) analysis. Amorphous nature of the glass samples was proven by the exhibited XRD spectra while results obtained from the FTIR analysis proved the presence of functional groups such as TeO4, BO4 and BO3. The results obtained show that the density increased simultaneously with molar fraction while the molar volume decreases with the inclination of molar fraction. The elastic moduli and other elastic parameters such as Poisson's ratio, microhardness, softening temperature and Debye temperature were derived from the ultrasonic velocities obtained through the ultrasonic pulse technique and were found to exhibit a fluctuating trend with the increase of SrO concentration. The results obtained proved that the addition of SrO as a dopant in the prepared zinc borotellurite glass system has affected the elastic properties of the glass. Photon and neutron shielding characteristics of SrO glasses were studied using theoretical and simulation techniques. The SrO content has the significant impact on the photon and neutron shielding properties. Photon and neutron shielding properties ascends with increment of SrO content. 0.05SrO possess the highest photon and fast neutron attenuation properties in the studied SrO glasses.
The investigation involves a comprehensive study on the mechanical and shielding features of the zinc erbium tellurite glasses as a function of doped Ag 2 O content. The mechanical features are estimated for the examined glasses by utilizing the Makishima-Makinzie model. The results showed the mechanical moduli of Young (E), bulk (B), Shear (K), and longitudinal (L) increased with the increment of the Ag 2 O substitution ratio. Besides, the radiation shielding properties were also studied and discussed. Among the shielding parameters, the linear attenuation coefficient (LAC), half-value layer (HVL), the lead equivalent and transmission rate (TR) were estimated. The linear attenuation coefficient results illustrated that the TZEAg glasses are better compared to the commercial marketing glasses, especially TZEAg5 glasses. Doping of Ag 2 O content in zinc erbium tellurite glass improves its ability to attenuate the gamma photons. Also, this study revealed the effectiveness of the examined glasses on the fast neutron, where the fast neutron mass removal cross-section ∑ R (cm ² /g) computed theoretically. The results offered the maximum value of ∑ R = 0.019 cm ² /g attained for TZEAg1 while the minimum value ∑ R = 0.01884 cm ² /g for TZEAg5 glass.
[(TeO 2 ) 0.7 (B 2 O 3 ) 0.3 ] 1-x (BaO) x , x = 0.00, 0.05, 0.10, 0.20, 0.25, 0.30 and 0.35 mol fraction glass series were successfully synthesized by conventional melt quenching method. Amorphous phase of all samples was confirmed through X-ray diffraction while optical properties were determined using UV-VIS spectrophotometer. Fourier Transform Infrared (FTIR) analysis showed that the glass structure consisted of TeO 3 , TeO 4 , TeO 6 , BO 3 and BO 4 structural units. The optical band gap energy, E opt which was calculated from Tauc’ plots decreased as the amount of BaO increases, whereas, the Urbach energy value increased. The increase in Urbach energy value was attributed to the increase of defects in glass structure. The refractive indices of glass were found to increase along with the increased amount of BaO, due to the high polarization and high density of host material and glass modifier. The molar polarizability, α m, oxide ion polarizability, α o ²⁻ and optical basicity, Λ of the glasses are calculated by Lorentz-Lorenz equation. The glasses were found to possess α m values between 8.106 – 8.489 Å ³ , and α o ²⁻ values between 3.303 to 4.772. Meanwhile, optical basicity increases from 0.115 to 0.893.
A series of zinc borotellurite glass containing erbium nanoparticles with composition of {[(TeO2)0.70(B2O3)0.30]0.7(ZnO)0.3}1– y (Er2O3) y , y = 0.005, 0.01, 0.02, 0.03, 0.04, 0.05 mole fraction were prepared by using conventional melt-quenching method. The optical properties of the prepared glass samples were measured by using high precision Elipsometer and UV-Vis spectrophotometer. The theoretical analysis for electronic polarizability, oxide ion polarizability and optical basicity were determined by using Lorentz–Lorenz equation on the basis of refractive index and optical band gap energy. It is observed that there is a linear increasing trend of electronic polarizability with increasing content of erbium nanoparticles. The oxide ion polarizability increases with refractive index and decreases with band gap energy. The optical basicity analysis shows that the glass samples possess high basicity.
One of the major driving forces for the development of new glasses is the demand for high optical non-linearity with reduced cost and a higher damage resistance. Oxide glasses with large non-linear refractive index and non-linear absorption coefficient are promising materials for fiber telecommunication and for non-linear optical devices such as ultrafast optical switches, power limiters, real time holography, self-focusing, white-light continuum generation and photonic applications. To get insight into the optical absorption in amorphous materials, studies are still needed for revealing the nature of photoelectronic excitations in these materials by comparison with that in crystals which have been understood firmly based on band theory. Although the IR absorption loss in oxide glasses is larger than of fluorides, low light scattering loss is expected in these oxide glasses because they have lower glass transition temperature. In addition, small concentration of dopant such as alkaline metal and alkaline earth metal elements gives rise to the structural relaxation of the frozen-in density fluctuations even below glass transition temperature Tg, adding to the reduction of Tg as well. A review of the fundamentals and recent research advances in optical properties of oxide glasses containing chromium or titanium is presented.
Tm3+ activated germanate-tellurite glasses with good thermal stability and anti-crystallization ability were prepared. Efficient 2 μm fluorescence was observed in the optimal concentration Tm3+ doped glass and the corresponding radiative properties were investigated. For Tm3+: 3F4 → 3H6 transition, high spontaneous radiative transition probability (260.75 s−1) and large emission cross section (7.66 × 10−21 cm2) were obtained from the prepared glass. According to Dexter's and Forster's theory, energy transfer microscopic parameters were computed to elucidate the observed 2 μm emissions in detail. Besides, the effect of hydroxy groups quenching was also quantificationally investigated based on simplified rate equations. Results demonstrate that the optimal concentration Tm3+ doped germanate-tellurite glass possessing excellent spectroscopic properties might be an attractive candidate for 2 μm laser or amplifier.
The metallic silver nanoparticles (NPs) was introduced into the Er3+/Ce3+/Yb3+ tri-doped tellurite glasses with composition TeO2–ZnO–La2O3 to improve the 1.53 μm band fluorescence. The UV/Vis/NIR absorption spectra, 1.53 μm band fluorescence spectra, fluorescence lifetimes, X-ray diffraction (XRD) curves, differential scanning calorimeter (DSC) curves and transmission electron microscopy (TEM) image of tri-doped tellurite glasses were measured, together with the Judd–Ofelt intensity parameters, emission cross-sections, absorption cross-sections and radiative quantum efficiencies were calculated to investigate the effects of silver NPs on the 1.53 μm band spectroscopic properties of Er3+ ions, structural nature and thermal stability of glass hosts. It is shown that Er3+/Ce3+/Yb3+ tri-doped tellurite glasses can emit intense 1.53 μm band fluorescence through the combined energy transfer (ET) processes from Yb3+ to Er3+ ions and Er3+ to Ce3+ ions under the 980 nm excitation. At the same time, the introduction of an appropriate amount of silver NPs can further improve the 1.53 μm band fluorescence owing to the enhanced local electric field effect induced by localized surface Plasmon resonance (LSPR) of silver NPs and the possible energy transfer from silver NPs to Er3+ ions, and an improvement by about 120% of fluorescence intensity is found in the studied Er3+/Ce3+/Yb3+ tri-doped tellurite glass containing 0.5 mol% amount of silver NPs with average diameter of ∼15 nm. The energy transfer mechanisms from Yb3+ to Er3+ ions and Er3+ to Ce3+ ions were also quantitatively investigated by calculating energy transfer microparameters and phonon contribution ratios. Furthermore, the thermal stability of glass host increases slightly with the introduction of silver NPs while the glass structure maintains the amorphous nature. The results indicate that the prepared Er3+/Ce3+/Yb3+ tri-doped tellurite glass with an appropriate amount of silver NPs is an excellent gain medium applied for 1.53 μm band EDFA pumped with a 980 nm laser diode (LD).
Infrared (IR) and optical absorption spectra were measured in order to study the structure of some tellurite glasses containing boric oxide. The compositions (mol%) were (100-X) TeO2,XB2O3 whereX=5, 10, 20, 25, 30. The optical spectra were measured at room temperature in the wavelength range 350–450 nm, and the results show that the fundamental absorption edge is a function of composition, with the optical absorption due to indirect transitions. The optical band gap increases with increasing B2O3 content. The validity of the Urbach rule was investigated. The IR results prove the distribution of the TeO4 polyhedra which determines the network and the basic oscillations of the building units in the tellurite glasses. The IR results also prove the distribution of the boroxal group. The electrical conductivity was measured as a function of temperature in the temperature range (300–573 K). Both the conductivity and activation energy were found to be a function of added oxide type.
The optical properties of the binary glass system {(100 − x)TeO2 + xWO3} with 5 ≤ x ≤ 50 mol % was studied using Fourier transform infrared spectroscopy in the spectral range 150–25,000 cm−1. The color of these glasses changes from yellow to light green, to dark green as WO3 concentration increases. These glasses are disordered versions of tetragonal TeO2 of D24 symmetry where the Te atom is 4-fold coordinated. The W ion coordination states change from 4 to 6 when WO3 increases beyond 31.5 mol %. The band tail energies are found to be between 0.103 and 0.112 eV, however these values do not show a monotonic behavior as WO3 concentration increases. The optical band gap (Eopt) was found to decrease from 3 to 2.93 eV as WO3 increases from 15 to 30 mol % while the refractive index (N) as a function of WO3 was found to change from 2.27 to 2.36 as WO3 concentration increases from 15 to 30 mol.
The Er3+ doped zinc tellurite glass containing Ag nanoparticles (NPs) were synthesized from high purity raw materials by melt quenching method and the influence of Ag NPs on the spectroscopic properties were investigated. The glasses are characterized using DTA, EDX, TEM, FTIR, UV–Vis–NIR and photoluminescence (PL) techniques. The DTA data reveal that the addition of silver chloride increased the thermal stability from 0.52 to 0.67 for samples without and with 2 mol% AgCl respectively. The sharp peaks in EDX spectra show the presence of Ag nanocrystallites. The TEM micrograph shows the distribution of NPs is Gaussian and the average size is estimated ∼10 nm. Seven absorption bands of erbium were evidenced in the UV–Vis–NIR measurements. Optical band gap and density were found to decrease with addition of AgCl concentration, while molar volume increased. The PL spectra exhibit four peaks corresponding to 2H11/2 → 4I15/2, 4S3/2 → 4I15/2, 4F9/2 → 4I15/2 and 4S3/2 → 4I13/2 transitions. An enhancement in the order of six times for 2 mol% of dopant and a subsequent quench in luminescence spectra of co-doped zinc tellurite glasses were observed. Such enhancements were attributed to silver nanoparticles with average size of 10 nm and absorption band centered at 552 nm. The studied glasses provide enormous scope to achieve the materials suitable for nanophotonics, solid state lasers and color displays.
Longitudinal and shear ultrasonic velocities were measured in different compositions of the glass system (TeO2)1-x- (V2O5)x at room temperature and at 4 MHz frequency. The velocity data, the calculated elastic moduli, and Debye temperature have been used to obtain quantitative details about the structure of these glasses. Bulk modulus has been calculated using the ring deformation model according to the cation-anion bond of each oxide present in the glass. Moreover, network bond per unit volume was calculated to obtain more information about the structure of these glasses. Composition dependence of ultrasonic velocities, calculated elastic moduli, Debye temperature, Poisson's ratio, and oxygen ion molar volume showed that the change in the structure of tellurite vanadate glasses occurs at 20 mol% V2O5 content.
The velocity of longitudinal and transverse ultrasonic waves in different compositions of the glass system 0.65TeO2–(0.35 − x)V2O5–xGd2O3 have been measured at room temperature using the ultrasonic pulse-echo technique at 4 MHz. The velocity data of the glass system have been used to find the elastic moduli, Poisson's ratio, and Debye temperature. Some physical parameters such as the glass transition temperature and the fugacity have been calculated. The results indicated that, all of these parameters depend upon the rare-earth content. The compositional dependence of these parameters on the Gd2O3 content has been explained in terms of the bond compression model and the ring diameter model. The structure of some tellurovanadate glasses doped with various oxides of transition metals, ferroelectric materials, heavy metals and rare earth have been evaluated and discussed in terms of these two models.
Since infrared spectroscopy and density are advantageous tools for the investigations of glasses, we have used them to obtain information concerning the local structure of xGd2O3·(100 − x)[4Bi2O3·GeO2] glass system, with 0 ≤ x ≤ 30 mol%. Gd2O3 play the network modifier role in the studied glasses and determines, by progressive addition, the increase of structural volume difference between the hypothetical crystalline compounds and the quenched samples. FTIR spectroscopy data show that the glass structure consists on the BiO6, GeO4 and GeO6 structural units, and the conversion among these units mainly depends on the Gd2O3 content.
The heat capacity (Cp) change in the glass transition region for the xNa2O ·(100−x)TeO2, mol%, glass forming melts with x=7.5, 11.1, 15.0, 20.0 and 25.0 was measured as a function of heating rate (2, 4, 6, 10 and 15 °C/min) using differential scanning calorimetry. The glass transition properties that have been measured and reported in this paper include the glass transition temperature (Tg), glass transition width (ΔTg), heat capacities in the glassy and liquid state (Cpg and Cpl) and the activation enthalpy for glass transition (). Tg for these sodium tellurite melts decreased and increased with increasing Na2O. Values of the ratio Cpl/Cpg ranged between 1.28 and 2.47, and the fragility parameter ranged between 100 and 130, suggesting that these glass forming melts may be classified as intermediate between typical strong and fragile liquids. The viscosity, η, calculated at a few selected temperatures near the glass transition region decreased with increasing Na2O at any given temperature, which is also expected.
Glasses in the system (1 − x) [29Na2O− 4Al2O3− 67B2O3]− xZnO (0 ≤ x ≤ 35 mol%), have been prepared by the melt quenching technique. Elastic properties, X-ray and FT-IR spectroscopic studies have been employed to study the role of ZnO on the structure of the investigated glass system. Elastic properties and Debye temperature have been investigated using sound wave velocity measurements at 4 MHz at room temperature. The results showed that the density increases and the molar volume decreases while both sound velocities and the determined glass transition temperatures decrease with increase in x. X-ray and infrared spectra of the glasses reveal that the borate network consists of diborate units and is affected by the increase in the concentration of ZnO content. These results are interpreted in terms of the decrease in the N4 values (fraction of tetrahedral coordinated boron atoms), and substitution of longer bond lengths of Zn–O in place of shorter B–O bond. The results indicate that Zinc ions have been substituted for boron ions as tetrahedral network former ions. The elastic moduli are observed to increase with the increase of ZnO content.
Glasses with the composition, (Sm2
O
3)
x
(ZnO)(40-x)(TeO
2)(60), were prepared by conventional melt quenching method. The density, molar volume, and optical energy band gap of these glasses
have been measured. The refractive index, molar refraction and polarizability of oxide ion have been calculated by using Lorentz-Lorentz
relations. Optical absorption spectra of these glasses were recorded in the range 300–700 nm at room temperature. The oxide
ion polarizabilities deduced from two different quantities, viz. refractive index and optical energy band gap, agree well
compared with other glasses. The nonlinear variation of the above optical parameters with respect to samarium dopant has been
explained.
The average electronic oxide polarizability α 0 <sup>2-</sup> of numerous single component oxides has been calculated on the basis of two different properties: linear refractive index n 0 and energy gap E g , which have demonstrated remarkable correlation. The optical basicity Λ of the oxides has been estimated on the basis of average electronic oxide polarizability calculated from the refractive index Λ(n 0 ) and the energy gap Λ(E g ). A good agreement has been observed between the optical basicity data obtained using independent initial quantities. The simple oxides have been separated into three groups according to the values of their oxide polarizability. The α 0 <sup>2-</sup> values (above 3 Å) obtained for PbO, Sb 2 O 3 , and Bi 2 O 3 have been attributed to the high cation polarizability and the presence of a lone pair in the valence shell of the cation. © 1996 American Institute of Physics.
The structure of MO1/2TeO2 (M = Li, Na, K, Rb, Cs and Tl) binary glasses has been studied by means of Raman spectroscopy. The glasses having low alkali content have a continuous network constructed by sharing corners of TeO4 trigonal bipyramids (tbp's) and TeO3 + 1 polyhedra having one non-bridging oxygen atom (NBO). In the glasses containing 20–30 mol% alkali oxide, TeO3 trigonal pyramids (tp's) having NBOs are formed in the continuous network. When alkali content exceeds 30 mol%, isolated structural units, such as Te2O2−5 ion, coexist in the continuous network. The fraction of TeO4 tbp's decreases with increasing alkali content. The glasses, which contain nearly 50 mol% alkali oxide, are composed of a continuous network constituted by TeO3 + 1 polyhedra and TeO3 tp's, and of isolated structural units, such as Te2O2−5 and TeO2−3 ions. The structure of thallium tellurite glasses having less than 30 mol% TlO1/2 is similar to that of alkali tellurite glasses containing equal amounts of MO1/2. The fraction of TeO3 tp's having NBOs in the thallium tellurite glasses, when TlO1/2 content is equal to or higher than 40 mol%, is larger than that in the corresponding alkali tellurite glasses. In the 66TlO1/2·34TeO2 glass, most of tellurium atoms are in a form of isolated TeO2−3 ion. A new hypothesis is also given for a mechanism for the basic structural changes in the tellurite glasses.
The structure of the glass system (75−x)B2O3–xBi2O3–25Li2O, where x=5, 10, 15, and 20 mol% was investigated by using pulse-echo technique. Elastic properties of the glass system have been calculated together with Poisson’s ratio and Debye temperature from the measured densities as well as longitudinal and shear ultrasonic velocities at room temperature. Ultrasonic velocity measurements were taken at 4 MHz. Estimated parameters based on Makishima–Mackenzie theory and bond compression model were calculated in order to analyse the experimental elastic moduli. Addition effect of Bi2O3 on the elastic moduli was investigated in terms of the number of network bonds and the mean cross-link density of the glass systems. The average atomic ring size of the network was also calculated and it was found that it depends on the concentration of the modifiers. Composition dependence of the elastic moduli and Poisson’s ratio from one hand and the trend of both the ring diameter and the packing density from the other hand showed structural change at x=15 mol%.
Amorphous powders of Al2O3x2014;37.5 mol% Y2O3 (yttrium aluminum garnet (YAG)) were prepared by coprecipitation, decomposed at 800xB0;C, and hot-pressed uniaxally at low temperature (600xB0;C) and a moderate pressure (750 MPa). Optimum conditions yielded microstructures with only 2% porosity and partial crystallization of YAG. Further processing using high quasi-hydrostatic pressure (1 GPa) at 1000xB0;C enabled the production of fully crystallized YAG with gt;96% relative density and a nanocrystalline grain size of x223C;70 nm. 13;
Bioactive glasses of the system SiO2-Na2O-CaO-P2O5 have been prepared by the normal melting and annealing technique. The elastic moduli, attenuation, Vickers hardness, fracture toughness and fracture surface energy have been obtained using the known method at room temperature. The temperature dependence of elastic moduli and attenuation measurements have been extended over a wide range of temperature from 150 to 500 K. The SiO2 content dependence of velocities, attenuation, elastic moduli, and other parameters show an interesting observation at 45 wt% of SiO2 by exhibiting an anomalous behaviour. A linear relation is developed for Tg, which explores the influence of Na2O on SiO2-Na2O-CaO-P2O5 bioactive glasses. The measured hardness, fracture toughness and fracture surface energy show a linear relation with Young's modulus. It is also interesting to note that the observed results are functions of polymerisation and the number of non-bridging oxygens (NBO) prevailing in the network with change in SiO2 content. The temperature dependence of velocities, attenuation and elastic moduli show the existence of softening in the glass network structure as temperature increases.
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