Phase Transition In Ceramics Research Articles

Enhanced photostrictive properties in ternary (1-x)(0.7BiFe1-yMnyO3-0.3BaTiO3)-xKTaO3 ceramics

A novel ternary compound (1-x)(0.7BiFe1-yMnyO3-0.3BaTiO3)-xKTaO3 (BFMBT-xKT) is fabricated by solid-state synthesis technique. A systematic investigation of the crystal symmetry, ferroelectric properties, light absorption, and photostrictive properties was carried out with various Mn and KTaO3 doping content. The phase transition behavior induced by the addition of KTaO3 is investigated using X-ray diffraction and Rietveld refinement. The addition of KTaO3 leads to the appearance of the tetragonal phase and the coexistence of pseudo-cubic and tetragonal phases. Furthermore, a high fraction of the tetragonal phase is obtained due to the increased KTaO3 content. The solid solution BFMBT-0.02 KT exhibits strong ferroelectricity (Pr ≈ 42 μC/cm2) as well as a narrow bandgap (Eg ≈ 1.91 eV). Moreover, the largest photostriction of 1.68 × 10−3 has been achieved in BFMBT-0.02 KT under 405 nm laser irradiation. These improvements are strongly associated with the contribution of KTaO3-induced phase transition in ceramics. The power-dependent Raman spectroscopy reveals a redshift of phonon modes associated with B–O bond vibrations, indicating microscopic lattice expansion under illumination. As a result, the ternary BFMBT-xKT solid solutions with excellent photostriction will be a promising candidate for wireless optomechanical applications.

Crystal structures, dielectric properties, and phase transitions in Sr2ScGaO5-based brownmillerite ceramics

In the present work, the crystal structures and dielectric properties of the Sr2Sc1-xInxGaO5 (x = 0.0, 0.1, 0.2, 0.3) ceramics with the brownmillerite structures were investigated. The ceramics belong to the I2mb polar phases with fully ordered oxygen tetrahedral chains based on the X-ray diffraction and transmission electron microscope results. A typical second-order phase transition from the polar I2mb to non-polar Imma phase is identified by the dielectric properties and Raman analysis. The phase transition temperature increases linearly with the x value in Sr2Sc1-xInxGaO5 ceramics, which is induced by the increased ordering degree of GaO4 tetrahedral chains. The fact that no thermal hysteresis was found in dielectric response during the heating and cooling process along with the Curie-Weiss fitting result confirmed the second-order phase transition in the ceramics. The present work identifies the phase transition temperature in Sr2ScGaO5-based brownmillerite ceramics, and it can be easily adjusted by substituting the cations at the octahedral center in the brownmillerite ceramics.

Investigation of the system AgBr-AgI optical materials volt-ampere characteristics

IR light guides based on crystals and ceramics of the AgBr-AgI system are transparent in the mid-infrared range from 2 to 25 μm, which is in demand for thermal imaging, laser technology and spectroscopy. High photo- and radiation resistance makes these materials particularly attractive. For the design of optical equipment, information is needed on the electrical properties of the material, which are most fully characterized by the current-voltage characteristic (VAC). In this work, the dependence of VAC of the studied materials in the range of compositions from 5 to 80 mol.% AgI in the system AgBr-AgI on the composition of the material and temperature in the range of 298-453 K. It has been established that an increase in the iodine content for crystalline materials of AgBr-AgI systems leads to a decrease in electrical conductivity. The values of specific conductivity under equal conditions (the same temperature and the same applied voltage) for ceramics of the AgBr-AgI system are two to three orders of magnitude higher than for crystals. The values of specific conductivity for ceramics are at the level of conductivity of solid electrolytes. At the temperature of the β-AgI-α-AgI phase transition in ceramics of the AgBr-AgI systems, a jump in conductivity is observed, which is explained by the β-AgI-α-AgI phase transition. Keywords: Solid solutions of the AgBr-AgI system, current-voltage characteristic, specific conductivity

Исследование вольт-амперных характеристик оптических материалов системы AgBr-AgI

IR light guides based on crystals and ceramics of the AgBr-AgI system are transparent in the mid-infrared range from 2 to 25 μm, which is in demand for thermal imaging, laser technology and spectroscopy. High photo- and radiation resistance makes these materials particularly attractive. For the design of optical equipment, information is needed on the electrical properties of the material, which are most fully characterized by the current-voltage characteristic (VAC). In this work, the dependence of VAC of the studied materials in the range of compositions from 5 to 80 mol. % AgI in the system AgBr-AgI on the composition of the material and temperature in the range of 298-453 K. It has been established that an increase in the iodine content for crystalline materials of AgBr-AgI systems leads to a decrease in electrical conductivity. The values of specific conductivity under equal conditions (the same temperature and the same applied voltage) for ceramics of the AgBr-AgI system are two to three orders of magnitude higher than for crystals. The values of specific conductivity for ceramics are at the level of conductivity of solid electrolytes. At the temperature of the β-AgI – α-AgI phase transition in ceramics of the AgBr-AgI systems, a jump in conductivity is observed, which is explained by the β-AgI – α-AgI phase transition.

Energy Storage Ceramics: A Bibliometric Review of Literature.

Energy storage ceramics is among the most discussed topics in the field of energy research. A bibliometric analysis was carried out to evaluate energy storage ceramic publications between 2000 and 2020, based on the Web of Science (WOS) databases. This paper presents a detailed overview of energy storage ceramics research from aspects of document types, paper citations, h-indices, publish time, publications, institutions, countries/regions, research areas, highly cited papers, and keywords. A total of 3177 publications were identified after retrieval in WOS. The results show that China takes the leading position in this research field, followed by the USA and India. Xi An Jiao Tong Univ has the most publications, with the highest h-index. J.W. Zhai is the most productive author in energy storage ceramics research. Ceramics International, Journal of Materials Science-Materials in Electronics, and the Journal of Alloys and Compounds are the most productive journals in this field, and materials science—multidisciplinary is the most frequently used subject category. Keywords, highly cited papers, and the analysis of popular papers indicate that, in recent years, lead-free ceramics are prevalent, and researchers focus on fields such as the microstructure, thin films, and phase transition of ceramics.

High piezoelectric activity in lead-free BaTiO3-BaZrO3-CaTiO3 ceramics with near polymorphic phase boundary

Lead-free 0.88BaTiO3–(0.12-x)BaZrO3–xCaTiO3 (BT-BZ-xCT) ceramics were fabricated via solid state reaction. The effect of CaTiO3 content on crystal structure, phase transition, and electrical properties was investigated systematically. The crystal structure and phase transition of ceramics were characterized by X-ray diffraction (XRD), Raman spectra and dielectric measurement. Results show that ceramic in the composition, x = 0.02, exhibits a rhombohedral structure. Ceramics with increasing CT content transformed from a rhombohedral to orthorhombic structure in the composition, x = 0.04, and eventually became a tetragonal structure at the composition, x ≥ 0.08. The polymorphic phase boundary (PPB) was observed at the composition, x = 0.06, with coexistence of orthorhombic and tetragonal phases showing at almost room temperature. This PPB composition exhibited a high piezoelectric response (d33*) of 1,150 pm/V at 10 kV/cm as an electric field was applied. These results indicate that the materials studied have potential as candidates for lead-free piezoelectric ceramics.

Dielectric, Ferroelectric and Piezoelectric Properties of the Lead Free 0.9BaTiO3-(0.1-x)Bi0.5Na0.5TiO3-xBi(Mg0.5Ti0.5)O3 Solid Solution

Solid solution of 0.9BaTiO3-(0.1-x)Bi0.5Na0.5TiO3-xBi(Mg0.5Ti0.5)O3 (BT-BNT-xBMT) system, where x = 0.00, 0.02, 0.04, 0.06, 0.08, 0.10, was synthesized by the solid state reaction. Dense BT-BNT-xBMT ceramics were obtained by sintering at 1,150–1,250˚C for 4 h. The effect of BMT on crystal structure and electrical property of BT-BNT ceramics was investigated as a function of composition, x, using X-ray diffraction, dielectric spectroscopy, hysteresis and strain measurements. The crystal structure of solid solution BT-BNT-xBMT, where x = 0.00-0.10, successively transforms from tetragonal to pseudocubic symmetry, with increased BMT concentration. Temperature dependence of dielectric constant (ϵr) and dielectric loss (tanδ) for BT-BNT-xBMT at various frequencies showed that phase transition of ceramics changed from ferroelectric to relaxor-like behavior as BMT content increased. Furthermore, remanent polarization (Pr), coercive field (Ec) and the normalized strain (d33*) of BT-BNT-xBMT ceramics tend to decrease with increasing BMT concentration.

Phase Transition Experimental and Theoretical Study of Micro Power Generator Supplying Source for CMOS Chip Based on Ferroelectric Ceramic Nano-Porous Material.

We demonstrated both experimentally and in theory analysis and calculation that the tin-modified lead zirconate titanate nanoporous ferroelectric generator system can perform as a micro-power supplying source for CMOS chip. The ferroelectric ceramic phase transition under transverse shock wave compression can charge external storage capacitor. The nanoporous microstructure ferro-electric ceramic micro-pulsed-power system is capable of generating low output voltage pulses and supplying CMOS chip with micro power sources. We developed the methodology for theory analysis and experimental operation of the ferroelectric generator. Analysis of the porous ferroelectric ceramic material was carried out by X-ray diffractometry and X-ray photoelectron spectroscopy. Microstructures and surface morphology of porous ferroelectric ceramics samples were examined by using scanning electron microscopy. The planar shock wave experiments were conducted on a compressed-gas gun. The experimental results were in good agreement with the theory analysis. Keywords: PSZT Ferroelectric Ceramic, Shock Wave, Phase Transition, Depolarization, Micro-Power-Generator.

Dielectric spectroscopy of lead-free Bi0.5(Na0.75K0.25)0.5TiO3–BiAlO3 ceramics

The electrical properties of (1−x)Bi0.5(Na0.75K0.25)0.5TiO3–xBiAlO3 (BNKT–xBA, x=0–0.100) ceramics were investigated by AC impedance spectroscopy over a wide range of frequency (10−2–105Hz). X-ray diffraction studies confirmed the formation of a single-phase compound up to x=0.050 and a second phase developed for x=0.075 and 0.100. The diffusive factors, γ, of BNKT–xBA ceramics were found to be in the range 1.66–1.95, which signifies the diffuse phase transition in ceramics. The appearance of a single semicircular arc in the impedance spectrum shows the main contribution of the bulk resistance (Rb) due to grain effects. Rb was found to decrease with increasing temperature, but increase with increasing BiAlO3 (BA) concentration. The conductivity of the ceramics increased with increasing temperature and decreased as BA doping ratios increased. The activation energies obtained from DC conductivity were found to be in the range 0.48–0.65eV. A typical negative temperature coefficient of resistance (NTCR) behavior like that of semiconductor was observed in the BNKT–xBA ceramics.

Diffused AFE/RFE/PE phase transitions in (Pb0.88Ba0.1La0.02)(Zr0.6Sn0.4− x Ti x )0.995O3 ceramics obtained from oxides and carbonates

We present the results of preparation and investigation of antiferroelectric/relaxor/paraelectric (AFE/RFE/PE) phase transitions in ceramics, (Pb0.88Ba0.1La0.02)(Zr0.6Sn0.4− x Ti x )0.995O3 with x = 0.05, 0.055, 0.06, and 0.065, obtained from oxides and carbonates using a conventional ceramic technology. Such compositions can be good candidates for energy storage in pulse capacitors. For such application, the critical field should be appropriate, i.e., neither too high nor too low, since the transition from AFE to FE/RFE properties should take place in fields close to electric breakdown, since in such situation the stored energy is the biggest. We present the results of investigations of the microstructure, dielectric permittivity, and P–E hysteresis loops at various temperatures. It has been stated that some of the investigated materials exhibit field-induced AFE/FE or AFE/RF transition appropriate for application in pulse capacitors.

Phase Transformation Experimental and Theoretical Study of Micro-power Generator Supplying Source for IC Chip Based on Ferroelectric Ceramic

We demonstrated both experimentally and in theory analysis and calculation that the PSZT ferroelectric ceramic generator system can perform as a micro power supplying source for IC chip. The ceramic phase transition under transverse shock wave compression can charge external storage capacitor. The ferroelectric micro pulsed power system is capable of generating low output voltage pulses with amplitudes 50.3 V and with transferred energy 1.12 mJ, and supplying IC chip with micro power sources. We developed the methodology for theory analysis and experimental operation of the ferroelectric generator. The experimental results were in good agreement with the theory analysis.

SYNTHESIS OF LEAD FREE SODIUM BISMUTH TITANATE (NBT) CERAMIC BY CONVENTIONAL AND MICROWAVE SINTERING METHODS

Dielectric studies were carried out on a lead free Sodium Bismuth Titanate, NBT, ( Na 0.5 Bi 0.5 TiO 3) composition. The material was synthesized by conventional ceramic method (CS) and microwave sintering (MS). The presence of single phase has been confirmed by X-ray diffraction and scanning electron microscopy of NBT ceramic. The later technique (MS) resulted in material with high density, dielectric properties and improved microstructure. The transition temperature was observed slightly higher for microwave sintered (MS) material. Longitudinal modulus measurements are very sensitive property to identify the phase transitions in ceramics. Longitudinal modulus (L) measurements were also employed on these samples in the frequency 136 kHz and can be studied in the wide temperature range 30°C to 400°C. The elastic behavior (L) showed a break at two temperatures (~200°C and 350°C) in both the conventional and microwave sintered ceramics. In NBT ceramics, permittivity anomalies are connected to modulus anomalies. The results are correlated with the dielectric measurements. This behavior explained in the light of structural phase transitions in the ferroelectric ceramics.

Theoretical and Experimental Study of CMOS Chip Energy Basing on PSZT Ferroelectric Ceramic Phase Transition

We have demonstrated the feasibility of ferroelectric ceramics micro power generator (MPG) supplying low power dissipation integrate circuit (IC) chip basing on Pb(Zr,Sn,Ti)O3 (tin-modified and niobium-modified PZT95/5) phase transition under shock wave compression. MPG provided micro-pulse-power with transferred energy up to 1.60mJ and with low voltage pulse amplitude 51.8V. We demonstrated experimentally that the MPG-capacitor system can perform as an IC-chip micro-power-sources supplying circuit. A methodology was developed for theory analysis of the MPG-capacitor system. The experimental results were in a good agreement with the theory analysis results.

Investigating phase transitions and strength in single-crystal sapphire using shock–reshock loading techniques

This paper focuses on developing a technique that can probe phase transitions in ceramics and evaluating strength properties of single-crystal sapphire. High strength ceramics that undergo solid-to-solid polymorphic phase transitions can display a wide range of volume changes. Materials with large volumetric changes can be easily detected; however, materials demonstrating small volume changes, pose a different experimental problem. Because of the variety of diagnostics tools (for acquiring data), and differing interpretation of the data, materials that undergo small volume changes, make detection of transformation quite challenging. Different experimental test methods are needed to potentially allow detection and characterization of materials undergoing phase transitions with small volume changes. In addition, these results show that single-crystal sapphire has considerable strength loss at approximately 56 GPa on the Hugoniot. In this study, we report loading profile measurements in the form of particle velocity histories for single-crystal sapphire that is shocked to a given stress level directly or through multiple steps from a shocked state of 56 GPa. We probe the region of suggested phase transformations utilizing the simplest type of off-Hugoniot reshock loading. This also allows an assessment of shear strength in the shocked state of single-crystal c-axis sapphire. The present measurements show no evidence of a phase transition, but do suggest considerable strength loss in sapphire.

Magnetic study of phase separation and charge ordering in La 1− xSr xMnO 3 near x=0.5

We have investigated the magnetic phase diagram of polycrystalline and single-crystal La 1− x Sr x MnO 3 near 0.46≤ x≤0.50. It turns out that for x<0.48, the polycrystalline material is ferromagnetic (FM), but for x≥0.48, incipient charge ordering takes place along with antiferromagnetism. At x=0.48, the ferromagnetic–antiferromagnetic phase transition in ceramics occurs at less than 85 kOe but requires significantly larger field for increasing x. These observations are in contrast to what is found in the single crystals, which are all FM.

Morse Stretch Potential Charge Equilibrium Force Field for Ceramics: Application to the Quartz-Stishovite Phase Transition and to Silica Glass

To predict phase transitions in ceramics and minerals from molecular dynamics simulations, we have developed a force field in which the charges are allowed to readjust instantaneously to the atomic configurations. These charges are calculated using the charge equilibration (QEq) method. In addition to electrostatics, a two-body Morse stretch potential is included to account for short-range nonelectrostatic interactions. This MS-Q potential is applied herein to SiO_2, where we find that it describes well the fourfold coordinated and sixfold coordinated systems (such as quartz and stishovite), silica glass, and the pressure-induced phase transition from quartz to stishovite.

Landau theory-based analysis of grain-size dependence of ferroelectric-to-paraelectric phase transition and its thermal hysteresis in barium titanate ceramics

Ferroelectric barium titanate ceramics with grain sizes in the range (0.5, 20) µm were used for a comparative study of grain-size influence on the ferro-para phase transition and its thermal hysteresis. The investigations were performed by recording the temperature dependence of the dielectric constant, heat capacity and pyrocharge. The experimental results have been analysed in the framework of Landau-Devonshire theory. The grain-size dependent Landau coefficients of the free energy have been derived from our experimental data and used to compute the grain-size dependence of the theoretical transition interval related to the thermal hysteresis. The good qualitative agreement between theory and experiment recommends the size dependent Landau coefficients as a way to improve the modelling of the size dependent ferro-para phase transition in ceramics.

Finite-size effects in ferroelectric solid solution

We studied the effect of grain size on the ferroelectric phase transitions in ceramics (x = 0.3, 0.5 and 0.7) prepared by a sol-gel method. The samples were observed and analysed by SEM, TEM and x-ray diffraction. The phase transitions were investigated by means of dielectric measurements. With the decrease of grain size, the Curie temperature decreases and the Curie peak becomes lower and broader and eventually disappears. The diffuseness of the dielectric response is understood on the basis of a diffuse phase transition model. The size dependence of can be described by , where is the for bulk , D is the grain size, and C and are two constants. This equation gives three ferroelectric critical sizes of 317 nm, 246 nm and 176 nm for x = 0.3, 0.5 and 0.7 respectively.

衝撃圧力 セラミックスの衝撃圧縮挙動の計測

In shock-compression measruement on solids, it is important to use controlled, high-quality specimens and to use high-capability measurement apppratuses. We have been investigating the shock-yielding property, high-pressure phase transition, equation of state, etc. of ceramics, minerals, semiconductors, etc., through shock-wave measurements. In this report, at first, the improved measruement methods combined with the keyed-powder gun used in our studies are described. In the next, the recent studies on selected good quality ceramics (ZrO2, Si3N4, AIN, B4C) are reviewed. The typical effects of shock compression on yielding property and phase transition of ceramics are shown, and the yielding mechanism and the correlation with material charcterizations are discussed.

Photoacoustic Study on Phase Transition in FE Ceramics

The phase transitions in FE ceramics, such as Pb(Zr,Ti,Sn)O3 (PSZT), transparent PLZT and Li1-xNaxNbO3(LNN), were studied with the photoacoustic technique. The features of the differences in phase transition in these ceramics are revealed. The photoacoustic technique is confirmed to be very sensitive to phase transition. The results could be explained thermoelastically.