Maria Teresa Buscaglia

• Doctor of Philosophy
• Senior Researcher at Italian National Research Council

The paper reports an overview of the ROPEVEMI project aiming at the development, from laboratory to industrial scale, of an innovative and sustainable microwave-assisted rotational moulding (RM) process for manufacturing of polyethylene (PE) powders into medium-to-large-size hollow items. Based on a preliminary screening of MW-active materials whic...

In order to further improve the performance of 0.94[(Bi 0.5 Na 0.5 )TiO 3 ]‐0.06BaTiO 3 /polyvinylidene fluoride (NBT‐BT/PVDF) flexible composite films prepared by the hot‐pressing method, the effect of surface modification of the NBT‐BT particles on the structure and properties of the films was investigated. Two coupling agents, namely, (3‐aminopr...

Polymer-based nanocomposites containing inorganic ferroelectric inclusions, typically ABO3 perovskites, have emerged as innovative dielectric materials for energy storage and electric insulation, potentially coupling the high breakdown strength (BDS) and easy processing of polymers with the enhancement of dielectric constant provided by the ferroel...

Scheelite-type materials such as LaNbO4 are increasingly attracting attention as a possible alternative to the most common fluorite and perovskite structure as ion conductors. However, they are much less used and investigated. The introduction of tungsten in lanthanum orthoniobate leads to conduction properties that are compatible with oxygen ion c...

Pure perovskite Ba0.90Ca0.10TiO3 ceramics, with a relative density of between 79 and 98% and grain sizes larger than 1 µm, were prepared by solid-state reaction. The dielectric and electrocaloric properties were investigated and discussed considering the density and grain size of the samples. Room temperature impedance measurements show good dielec...

Pure perovskite 1%Eu – BaZryTi1-0.0025-yO3 ceramics with compositions y=0, 0.05, 0.15, and 0.30 prepared by solid-state reaction were investigated by impedance spectroscopy and high field measurements (P(E), dc-tunability). The ceramic samples present a nonlinear dielectric character and the dc-tunability reaches a maximum for y = 0.15 (nr = 85%) d...

Nonclassical light sources are highly sought-after as they are an integral part of quantum communication and quantum computation devices. Typical sources use bulk nonlinear crystals that rely on stringent phase-matching conditions, limiting the operating wavelength and bandwidth. In this work, we demonstrate the generation of photon pairs from a fr...

We demonstrate the generation of biphotons from a free-standing, bottom-up grown lithium niobate microcube at telecommunication wavelength through the spontaneous parametric down-conversion. The maximum biphoton rate obtained fromã4 µm microcube is ~80 Hz.

It is well known that disordered relaxor ferroelectrics exhibit local polar correlations. The origin of localized fields that disrupt long range polar order for different substitution types, however, is unclear. Currently, it is known that substituents of the same valence as Ti4+ at the B-site of barium titanate lattice produce random disruption of...

It is well known that disordered relaxor ferroelectrics exhibit local polar correlations. The origin of localized fields that disrupt long‐range polar order for different substitution types, however, is unclear. Currently, it is known that substituents of the same valence as Ti4+ at the B‐site of barium titanate lattice produce random disruption of...

Nonclassical light sources are highly sought after as they are an integral part of quantum communication and quantum computation devices. Typical sources rely on bulk crystals that are not compact and have limited bandwidth due to phase-matching conditions. In this work, we demonstrate the generation of photon pairs from a free-standing lithium nio...

Over the past few decades there has been an extraordinary progress in the field of photonics and optoelectronics, which has led to the development of various materials and devices capable of manipulating and controlling the generation, transmission and transduction of light. The phenomenon of luminescence is exploited for large scale applications s...

Composites of poly(vinylidene fluoride) (PVDF) and BaTiO3 nanoparticles (average diameter ca. 125 nm) are fabricated by a solvent‐free and industrially scalable technique, that is, melt blending, followed by compression molding. The effect of processing parameters on the spectroscopic, microstructural, thermal, mechanical and dielectric properties...

Scheelite-type materials such as LaNbO4 are increasingly attracting attention as a possible alternative to the most common fluorite and perovskite structure as ion conductors. However, they are much less used and investigated. The introduction of tungsten in lanthanum orthoniobate leads to conduction properties that are compatible with oxygen ion c...

Four different functional properties at room temperature were found in Ba12Fe28Ti15O84 quaternary ferrite ceramics: a thermoelectric character with a prominent Seebeck coefficient of -400 μV/K, a strong ferrimagnetic character and weak magnetoresistivity, non-linear dielectric character (tunability) and ferro/piezoelectric response. The complex cry...

An extensive broadband dielectric spectroscopy study of BaCe0.3Ti0.7O3 ceramics is presented. The distribution of relaxation times of the system derived from the frequency dependence of complex dielectric permittivity are similar to the ones observed in dipolar glasses. Therefore, it is demonstrated that the dipolar glass model, which is applied he...

In the present work, a magnetodielectric flexible thick film composite with a quaternary Ba12Fe28Ti15O84 ferrite filler (≤ 9 vol%) embedded into PVDF polymer matrix was investigated. The role of filler volume on the macroscopic dielectric, magnetic and ferroelectric properties as well as on the nanoscale magnetic and piezoelectric response was anal...

Barium titanate, BaTiO3, has been the first commercial ferroelectric and piezoelectric material. After more than 70 years from its discovery, it is still the most widely used functional ceramic in the electronic industry, mainly as a dielectric in multilayer ceramic capacitors. The commercial success of barium titanate has been largely determined b...

The dielectric behavior of the Ba(Ti0.8Ce0.2)O3 ceramics was studied by broadband dielectric spectroscopy in a temperature interval 140–500 K. The broad dielectric relaxation was analyzed by the Havriliak–Negami relationship and the distribution of relaxation times formalism. It was found that the Havriliak–Negami average relaxation time, longest a...

This poster summarises our papers: V. Buscaglia et al., J. Phys.: Condens. Matter 26 (2014) 065901 & G. Canu et al., Acta Mater. 152, 258 (2018). The high relative dielectric constant (εr = 2000-5000) and low losses (about 1%) of ferroelectric barium titanate, BaTiO3, has made it the most widely used dielectric ceramic material in the electronic in...

The amazing properties of ferroelectric perovskite BaTiO3 (BT) and its solid solutions make them indispensable for many technological applications (e.g. multilayer capacitors). Unfortunately, the so-called ‘size effect’ limits their use. Indeed, under a certain critical particle size, these materials show a suppression of the spontaneous polarizati...

BaTi5O11 has been extensively studied because of their microwave dielectrics properties. Traditionally, it is difficult to achieve this material as single-phase. Here, we report an effective method to obtain BaTi5O11 powder with nanometer-scale crystals, by solid-state reaction at moderate temperatures and using as precursors nanostructured particl...

This poster summarises our work: G. Canu et al., Structure-property correlations and origin of relaxor behaviour in BaCexTi1-xO3, Acta Materialia 152, 258–268 (2018). The incorporation of homovalent M4+ ions at the Ti site of BaTiO3 with formation of the BaMxTi1-xO3 solid solutions (M = Sn, Zr, Hf, Ce) determines significant modifications of the p...

The ability to tune and enhance the properties of luminescent materials is essential for enlarging their application potential. Recently, the modulation of the photoluminescence emission of lanthanide-doped ferroelectric perovskites by applying an electric field has been reported. Herein, we show that the ferroelectric order and, more generally the...

Many dielectric and semiconductor materials used for all-dielectric resonators or metasurfaces have low absorption in the near infrared to visible range, but they are lossy in the near ultraviolet (NUV) range due to their low energy band gap. Contrary to this, the ferroelectric lithium niobate (LiNbO3, LNO) has an energy band gap larger than 4 eV,...

In this work 0-3 connectivity composites based on poly(vinylidene fluoride) (PVDF) and containing 30 vol% of BaTiO3 nanoparticles were prepared by using two different processing methods: solvent casting and melt blending. In both cases, the ensuing composite materials were compression molded to obtain sheets suitable for the subsequent characteriza...

Macroscopic properties measurements, such as dielectric permittivity and ferroelectric hysteresis, differential scanning calorimetry, and average structure information are combined with complementary techniques sensitive to the local structure, i.e. Pair Distribution Function (PDF) and Raman spectroscopy, to gain comprehensive insight into the stru...

Skutterudites are interesting compounds for thermoelectric applications. The main drawback in the synthesis of skutterudites by solidification of the melt is the occurrence of two peritectic reactions requiring long annealing times to form a single phase. Aim of this work is to investigate an alternative route for synthesis, based on rapid solidifi...

The nano-structuring of matter opened the way for advanced applications from biology to photonics. Nanostructures of materials with high refractive index and nonlinear properties have already been demonstrated in the visible-to-near-infrared range. Here we propose a new material for photonic applications in the near-ultraviolet (UV) range. We show...

SrTiO3-BaTiO3 nanocomposites with tailored microstructure exhibit enhanced dielectric properties in comparison to homogeneous ceramics with the same overall composition, including stable permittivity (830±60) over a wide temperature range (-150 to 50°C), low losses (≤ 3% between -150 to 150°C)), small dc conductivity (<10-10 S/m) and reasonable tun...

In the present work, composite ceramics of BaTiO3 with La0.08Pb0.92Ti0.20Zr0.80O3 were prepared from powders synthesized by two different methods: (a) PLZT@BT ceramics from core-shell powders with PLZT-core and BaTiO3 shell and (b) PLZT-BT ceramic composites from mixed PLZT and BaTiO3powders. In core-shell ceramics, a thin conductive layer of BaPbO...

Particle stabilized liquid foams are used as templates to obtain carbon-based porous materials with open cell structure, high specific area and hierarchical porosity. This route relies on gel casting to strengthen the structure of the liquid foams, followed by high temperature treatment to eliminate organic components and obtain solid foams. The li...

The nanoscale coating of small particles with materials of different composition, resulting in the formation of core-shell structures, is a relatively new and active area of research. Core-shell particles can be used as building blocks for the fabrication of bulk composite multifunctional materials with 0-3 connectivity by means of appropriate dens...

Polar or pyroelectric materials have a non-centrosymmetric structure and possess an electrical dipole moment even in the absence of an external electric field. This chapter focuses on the synthesis methods developed for the preparation on nanowires (NWs) and nanotubes (NTs) either free-standing or grown on a substrate. It also describes the crystal...

The goal of this work is studying the evolution of thermoelectric transport across the members of the Ruddlesden-Popper series iridates Srn+1IrnO3n+1, where a metal-insulator transition driven by bandwidth change occurs, from the strongly insulating Sr2IrO4 to the metallic non Fermi liquid behavior of SrIrO3. Sr2IrO4 (n=1), Sr3Ir2O7 (n=2) and SrIrO...

The goal of this work is studying the evolution of thermoelectric transport across the members of the Ruddlesden-Popper series iridates Srn+1IrnO3n+1, where a metal-insulator transition driven by bandwidth change occurs, from the strongly insulating Sr2IrO4 to the metallic non Fermi liquid behavior of SrIrO3. Sr2IrO4 (n=1), Sr3Ir2O7 (n=2) and SrIrO...

The hydrothermal synthesis of SrTiO3 in a Sr(OH)(2)/NaOH solution by reaction of four different single crystalline titanium precursors (anatase, rutile, sodium titanate, and hydrogen titanate) having the same nanowire morphology was investigated under stagnant fluid conditions. Owing to the low solubility and dissolution rate of the parent phases,...

A structural study of Sm- and Gd-doped ceria was performed with the aim to clarify some unexplained structural features. (Ce1-xREx)O2-x/2 samples (RE ≡ Sm, Gd; x = 0, 0.1, ..., 1) were prepared by coprecipitation of mixed oxalates and subsequent thermal treatment at 1473, 1173, or 1073 K in air; they were then analyzed at room temperature both by s...

Permittivity, tunability, and ferroelectric properties can be tailored to meet specific requirements for applications by combining ferroelectric (BaTiO3-BT) and antiferroelectric (La0.04Pb0.96Ti0.1Zr0.9O3-PLZT) and by exploiting interdiffusion and grain size effects at nanoscale. The dielectric properties, dc-tunability, and P(E) loops of ferroelec...

In the present work, composite ceramics of ferroelectric BaTiO3 (BT) with magnetic αFe2O3 were prepared from powders synthesized by two different methods: (a) core-shell powders of Fe2O3@BT and (b) Fe2O3-BT composites from mixed powders with the same composition. The M(H) loops at room temperature show a “wasp-waisted” character, with multiple comp...

This paper reports on a method for estimating the average grain size of superconducting nanoparticles through their magnetic properties. The use of SQUID magnetometry to determine the average MgB2 particle size was investigated and the results were compared with those of several different techniques. In particular, the data obtained from zero field...

A series of La-doped (10 at.%) SrTiO3 ceramics with grain size ranging from 6 μm to 24 nm was prepared from nanocrystalline powders using high-pressure field assisted sintering (HP-FAST). A progressive reduction of thermal conductivity κ with decreasing grain size was observed. At room temperature, κ of the ceramic with grain size of 24 nm (1.2 W m...

An experimental study is here presented focused on the problem of tailoring of solid foams with controlled structural and chemical features produced by drying and/or sintering of liquid foams stabilized by nanosized materials. The aim of this study is a better understanding of the relation between the interfacial properties of mixed systems contain...

Anisotropic nanostructures such as nanowires (NWs)/nanotubes and nanometer-sized islands are the subject of intense research efforts due to several interesting phenomena observed to occur in confined geometries with a high aspect ratio and/or reduced size. Understanding and controlling the mechanical and electromechanical behaviors of these nanostr...

Ba–Fe–Ti oxides are nowadays attracting considerable interest for the production of permanent magnets and microwave devices, due to their high dielectric constant. Among these materials, recently the quaternary ferrite Ba12Fe28Ti15O84 (BFT) was discovered to possess ferrimagnetic properties at room temperature with a main magnetic transition at abo...

BaCe xTi1− xO3 (x = 0.06, 0.10, and 0.20) solid solutions were prepared via conventional the solid-state reaction and sintered at 1500°C for 4 h, resulting in dense single phase ceramics with homogeneous microstructures. The electric field dependence of permittivity of the BaCe xTi1− xO3 ceramics was investigated in detail, together with the ferroe...

We investigate the second-harmonic generation (SHG) signal from single BaTiO3 nanoparticles of diameters varying from 70 nm down to 22 nm with a far-field optical microscope coupled to an infrared femtosecond laser. An atomic force microscope is first used to localize the individual particles and to accurately determine their sizes. Power and polar...

The grain size influence on the dielectric relaxation and nonlinear dielectric properties of BaTiO3 ceramics with grain size in the range of (92÷936) nm densified by Spark Plasma Sintering (SPS) from ultrafine powders were investigated. The progressive reduction of the Curie temperature and of the effective permittivity results from a combination o...

In the present study, particles with different Bi2Fe4O9 micro/nanostructures with a few particular morphologies (flower-like nanoplatelets, hierarchical microstructures, perfectly square platelets single crystals, etc.) obtained under specific hydrothermal synthesis conditions were investigated. The role of the processing parameters (such as NaOH c...

The mechanisms driving the mutual crystallographic alignment of nanocrystals in mesocrystals are various and not yet fully understood. As discussed in this paper, formation of mesocrystals can result from a topochemical reaction between single crystal particles or templates suspended in a liquid phase and ionic/molecular species in solution. In suc...

Dielectric responses of ceramics from the lead-free isovalent BaZrO3-BaTiO3 (BZT) system were investigated from Hz frequencies up to the infrared in a broad temperature range, 10–700 K. Pure BaZrO3 is a displacive weak-incipient ferroelectric with a simple cubic perovskite structure down to low temperatures, whose dielectric response is fully deter...

The influence of the oxygen vacancies on the dielectric response of BaZr0.10Ti0.90O3 ceramics prepared by solid-state reaction and sintered at 1400 °C for 2 h was investigated. The as-sintered ceramic exhibits a giant relaxation with a shift of the transition temperature from ∼85 °C to above 170 °C in the frequency ranges of 1 Hz–100 kHz, with high...

In this study we report for the first time the magnetic and dielectric properties of the quaternary layered ferrite Ba12Fe28Ti15O84. Dense ferrite ceramics were prepared by conventional sintering using powders obtained by solid-state reaction and by coprecipitation. Only the latter powder resulted in nearly single phase ceramics, whereas larger amo...

Here we report on the piezoelectric and ferroelectric properties of individual one-dimensional objects made of Bi4Ti3O12 (BiT). The nanorods and nanowires investigated in this study were fabricated by a two-step process: (1) preparation of reactive templates using hydrothermal-like synthesis and colloidal chemistry and (2) transformation of the rea...

One-dimensional nanostructures are usually fabricated using liquid-phase chemical methods or growth from the vapor phase. A different approach is proposed in this investigation. Using two different kinds of reactive templates with core−shell structure obtained using colloidal chemistry methods, we fabricated for the first time Bi4Ti3O12 nanorods an...

The nonlinear dielectric properties of dense BaTiO ₃ ceramics with grain size of 1 μ m –90 nm were investigated. In the finest ceramics, the permittivity reduces below 1000 and a remarkable nonhysteretic linear dc-tunability [ε(E)] is obtained at high field, above 40 kV/cm. The observed behavior was explained by considering the nanostruc...

We report in the present paper some original results of a joint research performed in the framework of the COST Action 539 ELENA. In search of higher miniaturisation of electroceramic devices a new outlook seems to arise from ceramics with unusual morphology that might present a new kind of circular or toroidal ferro-electric ordering of dipoles. C...

Well-designed reactive precursors and templates allow for careful control of solid-state reactions at the nanoscale level, thus enabling the fabrication of materials with specific microstructures and properties. In this study, Fe2O3@BaTiO3 core shell particles have been used as precursors for the in situ fabrication of multifunctional composites co...

In the present work, diphasic ceramic composites with core-shell nanostructures formed by Ni _0.50 Zn _0.50 Fe ₂ O ₄ core and BaTiO ₃ shell were investigated. Their properties were compared with those of composites prepared by coprecipitation. The core-shell structure was confirmed by microstruct...

Nanocoatings (5–20 nm) of different com-pounds on fine BaTiO 3 particles were obtained by means of precipitation processes. Homogeneous and smooth shells of Y(OH)CO 3 and Dy(OH)CO 3 were grown from nitrate solutions in the presence of urea. An irregular coating consisting of zirconia nanoparti-cles was produced from zirconyl nitrate solution using...

Zinc oxide nanoparticles were produced by aqueous precipitation in mild hydrothermal conditions (90 °C). Well crystallized regular roundish particles were obtained, with a very narrow size distribution. The influence of soft templates (organic species) to control size and size distribution in the final product was investigated. No effect was observ...

Nanocoatings (5–20nm) of different compounds on fine BaTiO3 particles were obtained by means of precipitation processes. Homogeneous and smooth shells of Y(OH)CO3 and Dy(OH)CO3 were grown from nitrate solutions in the presence of urea. An irregular coating consisting of zirconia nanoparticles was produced from zirconyl nitrate solution using ammoni...

Due to the high permittivity and low losses, ferroelectric ceramics with perovskite structure are largely used in the electronics industry for many applications. Presently, miniaturization of the components is one of the main goal in the field of microelectronics and communication. Accordingly, the current trend in high-tech ceramics is to realize...

The possible existence of a new kind of ferroelectric order and the need to explore domain arrangement in ferroelectric nanostructures has stimulated an increasing activity on the growth of ferroelectric nanowires. In the present study, single crystal BaTiO3 nanowires with tetragonal structure were obtained by an original solid-state process using...

Time-domain THz transmission and FTIR reflectivity spectra of dense core–shell composites of the BaZr0.2Ti0.8O3, BaZr0.4Ti0.6O3, Ba0.66Sr0.34TiO3 and Ba0.45Sr0.55TiO3 compositions were studied in a broad temperature range of 10–900 K. The spectra were evaluated to obtain the complex dielectric functions and at room temperature they were compared wi...

Yb-modified CaTiO3 ceramics sintered for 24 h at 1450 °C exhibit a giant apparent permittivity of about 104 with a remarkable temperature (30–300 K) and frequency (101–106 Hz) stability (maximum variation: ±20%). After a post-annealing treatment of 48 h at 1100 °C, the dielectric response is strongly modified, with a high frequency, low temperature...

First Ba(ZrxTi1-x)O3 (BZT) ceramics with various compositions prepared by solid state, with high density, ho- mogeneous microstructures and grain sizes in the range (0.7-4) μm were studied. Besides the dielectric and ferroelectric investigations, First Order Reversal Curves method was employed to describe the changes of the switching properties ind...

Powders of BaYxCe1−xO3−δ (x=0, 0.1 and 0.15) with specific surface area of 6–8 m2g−1 (BET equivalent particle size of 130–160 nm) were prepared by a modified solid-state route using nanocrystalline BaCO3 and CeO2 raw materials. These powders showed excellent densification at relatively low temperatures. Dense (96–97% relative density) ceramics with...

Polymers with different hydrophilic groups [polyvinylpyrrolidone (PVP), ammonium polyacrylate (APA), and hydroxypropylmethyl cellulose (HPMC)] and surfactants [cetyltrimethylammonium bromide (CTAB) and sodium dodecylbenzensulfonate (SDBS)] were used as additives to modify the crystallization of β-Ni(OH)2 in hydrothermal conditions. Marked morpholog...

Ba(ZrxTi1-x)O3 ceramics with various compositions x =0, 0.10, 0.15 and 0.18 have been prepared by solid state reaction using nanometric precursors of BaCO3, TiO2, and ZrO2. The processing parameters were optimized to obtain pure perovskite phase and homogeneous microstructures and densities higher than 90% for all the samples. The dielectric data s...

The solid solutions of (1-x)BiFeO3 - xBaTiO3 with x=0.20 and x=0.30 have been prepared via solid state, by sintering in air or in oxygen atmosphere. Optimum calcination and sintering strategy for obtaining pure perovskite phase, dense ceramics (>97% relative density) and homogeneous microstructures have been determined. Rhombohedral structure for x...

The formation of BaTiO3 nanoparticles by a solid-state reaction between nanocrystalline raw materials BaCO3 and TiO2 was studied as a function of temperature (400°–800°C), time (1–24 h), and titania particle size (15 and 30 nm). The reaction starts at 500°C and a high reaction rate is already observed at 600°C for the finest titania, with up to 90%...

Understanding the loss of ferroelectricity in submicron-and nano-sized perovskites is an issue that has been debated for decades. Here we report results from a high-energy x-ray diffraction XRD study on a prime example of the perovskite's family, BaTiO 3 ceramics with a grain size ranging from 1200 to 5 nm. We find that the loss of ferroelectricity...

Well-defined and stoichiometric spherical particles of BaTiO3 of narrow size distribution were produced at 82° and 92°3C by precipitation from chloride solutions in a strong alkaline environment. The size of the particles can be tailored in the range from ≅103 to 70–80 nm by increasing the barium concentration from ≅0.07 to 0.7 mol/L. The particles...

Hollow particles of barium titanate were obtained by a two-step process combining colloidal chemistry and solid-state reaction. BaCO(3) crystals (size ≈1 µm) suspended in a peroxy-Ti(IV) aqueous solution were coated with an amorphous TiO(2) shell using a precipitation process. Calcination of the BaCO(3)@TiO(2) core-shell particles at 700 °C resulte...

The defect chemistry of Yb3+:CaTiO3 solid solutions has been investigated both theoretically and experimentally. Three different incorporation mechanisms with similar solution energy were predicted for Yb3+ by atomistic simulation: (i) Ca site substitution with Ca vacancy compensation; (ii) Ti site substitution with O vacancy compensation; (iii) si...

Ba(ZrxTi1−x)O3 ceramics with x = 0.10, 0.15 and 0.18 were prepared via solid state reaction. For the composition x = 0.10, ceramics with various grain sizes in the range 0.75–3.20 μm were obtained by sintering at various temperatures 1350–1500 °C. High permittivity (above 14,000 at the transition temperature) and losses smaller than 7% for temperat...

Compositionally graded self-standing thick films (0.4mm) have been fabricated using the airflow deposition method. Films were made of five layers with different composition Ba(1−x)SrxTiO3 (BST, x=0, 0.1, 0.2, 0.3 and 0.4). The layers of different thicknesses, ranging from 80 to 30μm, presented similar Vickers microhardness of about 0.25GPa. The ave...

Di-phase ceramic composites 0.50BaTiO3–0.50Ni0.5Zn0.5Fe2O4 with limited reaction at interfaces prepared by two methods: (i) mixing BaTiO3 and Ni0.5Zn0.5Fe2O4 powders and (ii) co-precipitation of Fe, Ni, Zn salts in solutions containing BaTiO3 powders, are comparatively analysed. Homogeneous microstructures with higher density and better mixing of t...

The fabrication of the very thin (<1 μm) dielectric layers for the next generation of miniaturized multilayer ceramic capacitors will require barium titanate, BaTiO3, particles of 100−200 nm with narrow particle size distributions, high density, and high tetragonality. Composite particles, consisting of a BaCO3 core and a TiO2 shell, can be efficie...

The changes induced by the different stoichiometries in Ba0.9Sr0.1TiO3 solid solutions, with (Ba,Sr)/Ti = 1 and (Ba,Sr)/Ti > 1, on the dielectric, ferroelectric and ac tunability characteristics are investigated. A small difference in the (Ba,Sr)/Ti ratio causes a shift of the Curie and Curie–Weiss temperatures of 16 and 19 °C, respectively, but do...

Fine powders (particle size of 100–200 nm) of BaYxZr1 − xO3 − x/2 (x = 0, 0.08, 0.16) were produced by solid-state reaction at 1000–1050 °C using nanocrystalline ZrO2 and BaCO3 raw materials. The powders were densified by means of the spark plasma sintering process resulting in dense and homogeneous submicron microstructures. Near full density cera...

Dense nanocrystalline BaTiO3 ceramics with grain size (GS) down to 50 nm were studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC), impedance spectroscopy and Raman spectroscopy. A continuous reduction of the tetragonal distortion towards the pseudo-cubic state was obtained when the GS was reduced. Therefore, even the finest...

The solid solutions of BiFeO3–BaTiO3 have been prepared via solid state with a view to obtaining magnetoelectric properties, i.e. ferroelectric and magnetic activity in the same range of temperatures. Optimum calcination and sintering strategy for obtaining pure perovskite phase, dense ceramics (>97% relative density) and homogeneous microstructure...

Magneto-electric coupling in ceramic composites formed by ferroelectric and ferromagnetic phases can be obtained via an adequate mechanical coupling between the individual piezoelectric and magnetostrictive phases (product property). In the present work, the possibility of forming diphase ferroelectric–ferromagnetic ceramics has been investigated....

The coating of BaTiO3 particles with a different perovskite and the subsequent consolidation to dense ceramics retaining a radial composition gradient within the single grains are presented and discussed. A shell of SrTiO3 or BaZrO3 was directly grown on the surface of BaTiO3 spherical templates suspended in aqueous solution by means of a precipita...

p>BaZr0.1Ti0.9O3 ceramics with grain sizes of 0.75 and 2.60∈μm have been prepared via solid-state reaction. Optimum parameters for calcination and sintering have been found in order to obtain pure perovskite phase, high density ceramics and homogeneous microstructures. The dielectric data show a diffuse phase transition with a mixed ferroelectric-r...

BaZr x Ti 1-x O 3 is a possible candidate as environmental friendly electroceramic material (Pb-free ferroelectric) due to its high dielectric and piezoelectric constants and ferroelectric properties in a temperature range which can be tuned by the composition. Its properties change from full ferroelectric behavior (x=0; BaTiO 3) with a sharp ferro...

Cubic SrTiO3 particles are obtained by precipitation from an aqueous gel suspension. The gel suspension is prepared by hydrolyzing a TiOCl2 solution with NaOH and adding SrCl2. The addition of citric acid leads to spherical particles. The particle size can be tailored in the range 80−1400 nm by varying the temperature and the concentration. A caref...

Theoretical models for small ferroelectric particles predict a progressive decrease of the Curie temperature, spontaneous lattice strain, and polarization until the critical size corresponding to transition to the cubic phase and disappearance of ferroelectricity is reached. In contrast, the behavior of nanocrystalline BaTiO3 ceramics with a grain...

Dense nanocrystalline BaTiO3 (BT) ceramics with grain sizes (GSs) below 100 nm obtained by spark plasma sintering (SPS), were investigated by micro-Raman spectroscopy in order to obtain information about the changes in the local order induced by size effects. The obtained spectra in the range 80–700 K showed the presence of all the crystalline phas...

A rigorous kinetic model for the solution precipitation and hydrothermal synthesis of BaTiO3 particles is proposed. Three elementary kinetic processes are considered: primary nucleation, secondary nucleation, and diffusion-controlled growth. Secondary nucleation accounts for the acceleration of the formation kinetics after an initial slow crystalli...

Barium titanate has been prepared by solid-state reaction of nanocrystalline TiO2 (70 nm) with BaCO3 of different particle size (650, 140, and 50 nm). The results give evidence of a strong effect of the size of BaCO3 in the solid-state synthesis of barium titanate. The use of nanocrystalline BaCO3 already leads to formation of the single-phase BaTi...