Ferroelectric Glass-ceramics Research Articles

Physical properties and energy storage performance of TeO2-based ferroelectric glass-ceramics

xBaO–xTiO2–(100–2x)TeO2 (BTT) glass-ceramics were prepared through a melt-quenching synthesis method. Structural and optical properties, analyzed from Raman spectroscopy and absorption (OA) measurements, revealed that the increase in the TiO2 content promoted a loss in the network connectivity because of the formation of the non-bridging oxygen atoms (NBO’s) as well as the Te–O–Te bonds’ deformation. X-ray diffraction analysis confirmed the formation of ferroelectric nanocrystals (FeNCs) with tetragonal symmetry, related to the BaTiO3 phase, in the studied compositions, whose crystallinity seems to be intensified as the TiO2 concentration increases. The room temperature energy storage performance of these BTT samples, assessed using P-E hysteresis loops, confirmed excellent energy storage response and reveals the potential of the study glass-ceramics for practical applications.

Crystallization-temperature controlled alkali-free niobate glass-ceramics with high energy storage density and actual discharge energy density

The niobate-based alkali-free ferroelectric glass-ceramics were realized through the synthesis of mother glass by way of melt-annealing technique, followed by temperature-controlled crystallization. As the crystallization temperature raised, the ratio of the ferroelectric crystal phase precipitated in the mother glass enhanced continuously, resulting in the enlargement of the permittivity. Attribute to the rise of grain size, pores and cracks tend to appear in the microstructure of glass-ceramics with high crystallization temperature, leading to lower breakdown strength. The theoretical simulation was applied to reveal the internal mechanism, exploring the outcome of heat treatment temperature on the breakdown electric field. The maximum theoretical energy storage density reaches to 18.44 J/cm3 at the crystallization temperature of 800 °C. The single-layer capacitor made from the G800 sample exhibited extremely high power density (230 MW/cm3) and superior actual discharge energy density (1.5 J/cm3) at 600 kV/cm. These results indicate that alkali-free niobate-based glass-ceramics is a kind of encouraging candidate material for pulse capacitors.

Pulse discharge characterization of perovskite dielectric ceramics

The pulse discharge characterization of perovskite dielectric ceramics, which has confronted a barrier between research and application, has the problems of inconsistent test standards and lack of comparability. To mitigate this issue and further advance the application process, we suggest an extrinsic standard (for convenience of comparison) for energy dielectric ceramics of thickness (0.2 mm), electrode area (4 mm2) and operation voltage (2 kV). We report the pulse discharge performance parameters of three typical dielectric materials: relaxor ferroelectric (Na0.5Bi0.5)0.9Li0.1Ti0.9Ta0.1O3 (NBLTT), paraelectric Ca0.6Sr0.4TiO3 (CST) and linear dielectric K0.5Na0.5NbO3 (KNN) glass ceramics through computer simulation and fitting of pulse discharge curves based on the resistance-inductance-capacitor pulse discharge circuit. The NBLTT ceramics exhibited higher peak current (16 A under 100 kV/cm) and stability with minimal variation less than 15% from 20 to 150 °C during pulse discharge compared with linear dielectric and ferroelectric glass ceramics. In addition, the NBLTT system holds the fast discharge time (90% of the discharge energy density released in about 100 ns) and good fatigue resistance. The short discharge time, high thermal stability and low medium voltage (500–5000 V) make the NBLTT ceramics promising for pulse capacitor in large current and low electric operation voltage conditions. An operable comparison standard and the research frontiers of pulsed dielectric materials are prospected.

Transparent ferroelectric glass\u2013ceramics for wastewater treatment by piezocatalysis

In piezocatalysis the polarization field found in piezoelectric materials enables and enhances catalytic redox reactions. Here, we explore piezocatalytic dye degradation through transparent glass–ceramics containing piezoelectric crystals. 30SiO2–35Li2O–35Nb2O5 (in mol%) glass–ceramics containing varying amounts of LiNbO3 crystallites were fabricated by melt-quenching, followed by heat-treatment at a crystallization temperature of 650 °C for 2, 3 and 6 hours. During piezocatalysis, the 2 hour heat-treated sample showed up to 90% degradation of methylene blue dye within 150 min of ultrasonication, with no significant change in performance after three piezocatalysis cycles. This sample showed promising activity for degrading cationic and neutral dyes, and is optically transparent. This work demonstrates that transparent ferroelectric glass–ceramics are promising for water-cleaning applications by piezocatalysis.

Structure of glasses and composites in As<sub>2</sub>S<sub>3</sub>–Sb<sub>2</sub>S<sub>3</sub>–SbI<sub>3</sub> system

Purpose. Composites on the basis x (As 2 S 3 ) y (Sb 2 S 3 ) z (SbI 3 ) glasses are suitable for creation of ferroelectric glassceramics, nonlinear dielectrics, memory media, elements for infrared and nonlinear optics, various sensors. This paper presents the results of thermal, X-ray diffraction and Raman studies of the conditions of formation and nature of crystalline inclusions in the glass matrix of the As 2 S 3 -Sb 2 S 3 -SbI 3 system during their thermal treatment. Methods. Differential thermal analysis (DTA), Raman and X-Ray diffraction spectroscopy. DTA curves were carried out in the temperature interval of 293–700 K. Heating rate was equal 3 K/min. Results. Danoheterogenous structure of glasses in As 2 S 3 -Sb 2 S 3 -SbI 3 system established on the basis of Raman spectra investigations. Their structural network is formed by only binary structural groups with heteropolar bonds (AsS 3/2 , SbS 3/2 , SbI 3 , AsI 3 ) and contains a certain amount molecular fragments with homopolar As-As and S-S bonds (As 4 S 4 , S 8 ). It has been established that the crystallization of glasses takes place in several stages. DTA curves of glasses recorded at 3 K/min revealed three exothermic effects. For example, for 40(As 2 S 3 )30(Sb 2 S 3 )30(SbI 3 ) glass temperatures maxima of these effects are equal 341, 398 and 530 K. The first and second effects are less pronounced due to nucleus formation and the formation of nanocrystals in glass matrix. The structure of the phase that arises in the glass matrix at annealing (348 and 398 K) corresponds to the structure of the crystalline SbSI. The formation of triple units SbS 2/2 I occurs as a result of the glass structural relaxation during its softening, which is accompanied by breaking and switching of homopolar and heteropolar chemical bonds in the binary groups that form the structural network of glasses. This process is accompanied by the diffusion of atoms in a distances of interatomic order. The sizes of antimony sulfoiodsde crystalline inclusions increase with annealing temperature and annealing time. The matrixes of the annealed As 2 S 3 -Sb 2 S 3 -SbI 3 system glasses, in which crystalline SbSI inclusions of different dimensions are formed, are determined mainly by As 4 S 4 structural groups linked together by fragments of chains or rings of sulfur atoms. Conclusions. DTA curves, X–ray powder diffraction patterns and Raman spectra of glasses in As 2 S 3 -Sb 2 S 3 -SbI 3 were investigated. The nanoheterogeneous structure of glasses was established. The crystallization of glasses takes place in several stages. The structure of the phase that arises in the glass matrix at annealing corresponds to the structure of crystalline antimony sulfoiodide. The sizes of SbSI crystalline inclusions are dependent on the heat treatment regimes.

Structural, elelectrical and energy storage properties of BaO–Na2O–Nb2O5–WO3–P2O5 glass–ceramics system

Ferroelectric glass-ceramics are promising composite materials with dual properties, of high dielectric permittivity and high dielectric breakdown strength. In this context, new phosphate glass-ceramics 2BaO-0.5Na2O–2.5[(1 − x)Nb2O5–xWO3]-1P2O5 (x = 0, 0.1, 0.2, 0.3 and 0.4) designated as B0, B1, B2, B3, B4 respectively, were prepared by the controlled crystallization technology and then crystallized at high temperature of 760 °C for 10 hours. Subsequently, the obtained glass-ceramics were studied by Differential Scanning Calorimetry (DSC), x-ray powder diffraction (XRD), Raman, impedance spectroscopy, and the P-E hysteresis loops. All of these techniques allowed the identification of Ba2Na4W2Nb8O30 phase with tungsten bronze structure embedded in the glassy matrix. The density of glass-ceramics was found to increase with increasing tungsten content to reach a maximum at x = 0.3 and then decreases. Dielectric and conductivity parameters were found to be governed by the presence of oxygen vacancies. Room temperature energy storage property which depends on the composition X, was performed using P-E hysteresis loops of the glass-ceramics. The optimum discharge density was obtained for B3 with an energy efficiency of 73.77%.

BaBi2Ta2O9 based glass-ceramics: Influence of ZrO2 on crystallization kinetics, microstructure and dielectric properties

BaBi2Ta2O9 (BBT) based ferroelectric glass-ceramics (GCs) with different zirconium oxide (ZrO2) content used as nucleating agent are synthesized via glass melt-quenching technique followed by temperature controlled crystallization. The effect of ZrO2 as a nucleating agent on the crystallization mechanism, microstructure and dielectric properties of BBT based GCs has been studied for the first time. Crystallization kinetics studies facilitated successful controlled crystallization of ZrO2 doped BBT based GCs around the exothermic peak temperature using double stage and single-stage heat-treatments, which was otherwise difficult in the undoped glass. The dielectric constant increased while the loss and dissipation factors decreased with increase in zirconia content in the GCs. The dielectric properties obtained from single-stage and double-stage heat-treated GCs have been compared and correlated to the corresponding microstructures of the GCs. With 5 mol % ZrO2, dielectric constant of 181 with loss of 0.04 has been obtained for the sample fabricated by single-stage ceramization around the 2nd crystallization peak temperature.

Electrical properties of bismuth germanate (Bi2GeO5) ferroelectric glass-ceramics prepared by two different methods

Ferroelectric Bi2GeO5 glass-ceramics were fabricated using conventional and incorporation method. Glasses have been prepared from BiO1.5-GeO2-BO1.5 ternary glass system by focusing on the region of 59 mol%BiO1.5: 23 mol%GeO2: 18 mol%BO1.5. The resulting glass was analyzed by using differential thermal analysis (DTA) for determining the crystallization temperature (Tp). Then, the prepared glass pieces were heat treated at Tp. Effects of different fabrication methods on structure and electrical of the glass-ceramics were investigated. X-ray diffraction result of all glass-ceramics suggested that the main peak of glass-ceramics matched the orthorhombic structure of the pure Bi2GeO5 phase. Microstructures of the prepared glass-ceramics have been found to change from rod-like crystallites to bulk crystallites on modifying the fabrication method. The Bi2GeO5 glass-ceramics prepared by incorporation method presented higher dielectric constant than those of the Bi2GeO5 glass-ceramics prepared by conventional method. Moreover, the Bi2GeO5 glass-ceramic prepared by incorporation method possesses a large value of Pmax (0.94 µC/cm2) comparing to that of the glass-ceramics prepared by conventional method (Pmax = 0.73 µC/cm2). Thus, this study suggests that the incorporation method can effectively modify the microstructure of Bi2GeO5 glass-ceramics, resulting in the improvement of dielectric and ferroelectric properties.

Effect of surface treatment on microstructure of ferroelectric glass-ceramics containing NN and BNN

Abstract Ferroelectric properties of the glass-ceramics are correlated with the active crystals and the glass matrix which may exhibit complicated dielectric respond. It is interesting to find a method that can reduce the effect of glass matrix. The attempt of this work is to use surface treatment method. Glass-ceramic samples with and without Nd3+ doping were employed for the surface treatment process. After treatment by submersing glass-ceramic specimens into the diluted HF solution, phase variation and microstructural development of the samples were checked. XRD results of the treated glass-ceramic revealed a portion dissolution of NN and BNN to form sodium fluorosilicate (Na2SiF6) and barium fluorosilicate (BaSiF6). This observation is more pronounced in the sample with Nd3+ doping. Formations of the fluorosilicate type crystals indicate that F- reacted not only with [SiO4]4- silicate units in the glass matrix but also with the main crystalline phases. These observations are confirmed by SEM micrographs. Microstructural developments are clearly seen as the growths of the rod shape of sodium fluorosilicate and barium fluorosilicate crystallites.

Enhanced upconversion emissions in Er3+ doped perovskite BaTiO3 glass-ceramics via electric-stimulated polarization technique

In this work, Er3+ doped ferroelectric glass ceramics containing high-content BaTiO3 nanoperovskite have been prepared successfully. Optical behaviors with structural dependence indicate that the perturbation of ligand field by tunable thermal condition in glass-ceramics is beneficial to boost upconversion efficiency, that is, the emission intensity possesses multifold improvement in both green band (2H11/2, 4S3/2 → 4I15/2) and red band (4F9/2 → 4I15/2). And adding voltage to stimulate polarization reversal of ferroelectric domains has been investigated as a physical mode to broaden luminescence emissions in visible range. Compared with the unpolarized glass-ceramics, over 1.5 folds higher luminescence intensity can be obtained by polarizing the samples. The multiple mechanisms to achieve upconversion enhancement in ferroelectric materials will stimulate and expand the use of innovative optoelectronic devices.

Effect of phase structures on dielectric properties and energy storage performances in Na2O-BaO-PbO-Nb2O5-SiO2-Al2O3 glass-ceramics

Compared with ferroelectric ceramics, antiferroelectric ceramics, ferroelectric thin film and polymer-based composites, ferroelectric glass-ceramics have the advantages of high energy storage density, fast discharge speed and high power density. The effects of phase structures on dielectric properties, electric breakdown strength, energy-storage and charge-discharge performances have been systematically investigated in Na2O-BaO-PbO-Nb2O5-SiO2-Al2O3 glass-ceramics. The content of SiO2 and Nb2O5 affected the dielectric energy storage performances of the glass-ceramics by changing their ferroelectric phase proportions and crystallinity. By XRD analysis and Rietveld refinements, it was found the dielectric constant of the glass-ceramics was positively correlated with the relative proportions of M2NaNb5O15 (M = Ba or Pb) and NaNbO3 phases. The electric breakdown strength was negatively correlated with crystallinity and grain boundary activation energy. The maximum energy storage density 17.9 J cm−3 was obtained in these glass-ceramics. When the content of Nb2O5 was 30 mol%, under the charge electric field 300 kV cm−1 in overdamped discharge circuit, the instantaneous power density of glass-ceramics capacitors reached 75 MW cm−3. The discharge time for all glass-ceramics capacitors was less than 50 ns.

Effect of SiO2/B2O3 Ratio on the Crystallization Behavior and Dielectric Properties of Barium Strontium Titanate Glass–Ceramics Prepared by Sol–Gel Process

Ferroelectric glass–ceramics, with a basic composition 90 wt.% (Ba0.65Sr0.35)TiO3−10 wt.% (B2O3−nSiO2) (n = 0.5, 1, 3, 5) were synthesized by the sol–gel method and their phase development and dielectric properties were investigated by differential thermal analysis, x-ray diffraction, field emission scanning electron microscopy, dielectric temperature curves and impedance spectroscopy. From the differential thermal analysis, glass transition and crystallization behavior can be observed. From the x-ray diffraction study, two crystalline phases (Ba,Sr)TiO3 and Ba2TiSi2O8 were formed over the entire composition range of the glass–ceramics. In addition, the main crystal phase has undergone a transformation from (Ba,Sr)TiO3 to Ba2TiSi2O8 with the increase of n. A typical structure in which the crystal phase was surrounded by a glassy matrix has been observed in the scanning electron microscope images. As a result of temperature dependent dielectric property measurements, the dielectric constant increased obviously with the increase of n from 0.5 to 1. Further increasing n led to a reduction of the dielectric constant, which is in coincidence with the variation of the intensity of (Ba,Sr)TiO3 phase with n. According to the impedance spectroscopy analysis and the activation energy calculation, the relaxation peak in both Z″ and M″ data should be attributed to the crystal–glass interface, and the change of conduction mechanism with the increase of SiO2/B2O3 ratio may be attributed to the corresponding transition of the main crystal phase.

Dielectric Properties and Microstructural Studies of Er<sub>2</sub>O<sub>3</sub> Doped Potassium Sodium Niobate Silicate Glass-Ceramics

In this work, electrical and structural properties of ferroelectric glasses and glass-ceramics from K0.5Na0.5NbO3-SiO2 doped with 0.5-1.0 mol%Er2O3 system have been investigated. The influent of Er2O3 dopant was also compared with the original glass. The K0.5Na0.5NbO3 (KNN) powder was mixed with SiO2 in composition of 75KNN-25SiO2 and doped with Er2O3. Well-mixed powder was subsequently melted at 1300°C for 15 min in a platinum crucible using an electric furnace. The quenched glasses were then subjected to heat treatment at various temperatures for 4 h. From the study, KNN single phase in transparent glass was successfully prepared via incorporation method. The maximum Ԑr of about 360 at 10 kHz with a low tanδ of 0.07 could be obtained from the glass-ceramic sample of 75KNN–25SiO2 doped 0.5 mol% Er2O3 and heat treated at 600°C. It can be seen that the higher percent of Er2O3 can lower the dielectric loss of KNN glass-ceramics. This interesting value suggesting the opportunity of using them in electronic applications in the future.

Ferroelectric glass-ceramics

Abstract

Dielectric Properties of Niobate Glass Ceramics of PbO-SrO-Na2O-Nb2O5-SiO2 System with Partial Substitution of K+ for Na+

Substitution of K2O for Na2O content was performed for ferroelectric glass ceramics in the PbO-SrO-Na2O-Nb2O5-SiO2 system, in which a conventional melt quenching method was adopted for the parent glass production in order to investigate its effect on the crystallization process and associated dielectric properties. Phase identification combined with differential thermal analysis results show that the crystalline phase was compressed by the substitution of potassium ions. The hysteresis loop results demonstrate that by increasing the substitution of K+ for Na+, the maximal polarization was decreased while both the remanent polarization and coercive electric field increase. It is also noted that increasing the content of K+ could also reduce the dielectric constant of the glass ceramic system; the dielectric constant demonstrated a decrease from 775 to 299, meanwhile, the dielectric loss increased from 0.013 to 0.021 when 50 mol.% Na+ was replaced by K+. Additionally, leakage current results show that as more sodium ions are replaced by potassium ions, the leakage current increased and the resistivity decreased.

Preparation of Ferroelectric KNbO3 Based Borate Glass System.

The incorporation method was employed to produce ferroelectric glass ceramics from the K2O-Nb2O5-B2O3 glass system. The nanocrystalline potassium niobate (KNbO3) was first prepared using a simple mixed oxide method, where the B2O3 was initially mixed and then melted to form glass. The successfully produced optically transparent glass was then subjected to a heat treatment schedule for further crystallization at temperatures ranging from 500 to 650 degrees C, which resulted in the precipitation of the KNbO3 phase, together with the K3B2Nb3O12 phase. Scanning electron microscopy (SEM) showed the presence of randomly oriented KNbO3 crystals dispersed in a continuous glass matrix. It was found that the glass ceramics subjected to the heat treatment at temperatures higher than 545 degrees C were opaque, while the lower gave a highly transparent glass ceramics. The crystal size and crystallinity were found to increase with increasing heat treatment temperature, which in turn plays an important role in controlling the properties of the glass ceramics, including physical, optical, and dielectric properties.

Comparative properties of Sr x Ba1−x TiO3 ferroelectric glass–ceramics prepared by powder sintering and melt casting

A series of strontium barium titanate ferroelectric glass–ceramics were prepared by both powder sintering and melt casting. The effects of composition and preparation method on the structure, phase development, dielectric behavior, breakdown strength and energy storage properties were investigated. For the glass–ceramic prepared by powder sintering, there is an increase in dielectric breakdown strength as well as energy storage density with the increasing Sr content. The average breakdown strength and energy storage density of the BST glass–ceramic prepared by melt casting were improved remarkably as compared with those of the sample prepared by powder sintering. The sample with Ba/Sr ratio of 40/60 prepared by melt casting showed an average breakdown strength of 588 kV/cm and an energy storage density of 2.08 J/cm3.

Crystallization and optical properties of Nd3+ doped ferroelectric glass-ceramics in the barium sodium niobosilicate system

Ferroelectric glass-ceramics of the Na2O–BaO–Nb2O5–SiO2 system were obtained from a controlled crystallization process performed on the parent glass of composition 20Na2O–10BaO–30Nb2O5–40SiO2. Nd2O3 doping content was varied in the range 0, 0.1 and 0.5mol%. Thermal properties of the as-quenched sample were studied by DTA technique and the results of DTA showed a possible crystallization peak at 740°C and this was selected as the treatment temperature. The obtained glass-ceramics were investigated in terms of crystalline phase formation by XRD technique, microstructure by SEM and optical property using UV–visible spectroscopy. Fluorescence spectra of the glass-ceramics were also recorded at RT. The results of XRD revealed that NaNbO3 and Ba2NaNb5O15 were the dominant crystalline phases. The microstructures of the glass-ceramics reveal randomly distributions of small crystallites with the size in the range 0.17–0.19µm. At low Nd3+ content, the glass-ceramics were transparent material. With a yellow light excitation at 580nm, the glass-ceramic shows possible emissions in the ultraviolet, blue and green light region.

Influence of different nucleating agent additives on phase structure and ferroelectric properties of SrO–BaO–Nb2O5–CaO–SiO2–B2O3 glass-ceramics

Ferroelectric glass-ceramics of the SrO–BaO–Nb2O5–CaO–SiO2–B2O3 system with different nucleating agents Cr2O3, BaF2, ZrO2, CaF2 and CeO2, have been prepared by conventional melt casting followed by controlled crystallization processing. The effect of different nucleating agent additions on crystallization mechanism, crystallization behaviors, microstructures and dielectric properties of the glass-ceramics are studied using DTA, XRD techniques, SEM and LCR analyzer. The results show that the addition of different nucleating to the glass-ceramics decreases the crystallization temperatures, accelerates the secondary phase elimination and promotes the uniform distribution of grain size. The well development of microstructure promoted by the nucleating agents can result in the improvement of the dielectric constant as well as energy storage density remarkably. The sample with CeO2 as the optimum nucleating agent achieves the dielectric constant of 301, breakdown strength of 622 kV/cm and the highest energy storage density of 5.15 J/cm3.

The Effect of Nd3+Addition on Crystallization Behavior and Related Properties of the Ferroelectric Glass-Ceramics Na2O-BaO-Nb2O5-SiO2 Based Composition

Ferroelectric glass-ceramics of the Na2O-BaO-Nb2O5-SiO2 system were prepared from parent glass of composition 20Na2O-4BaO-26Nb2O5-50SiO2. Nd2O3 was systematically added in the range 0–3 mol% to the glass compositions as to study its effect on crystallization behavior of the glass and the dielectric properties of the associated glass-ceramics. Heat treatments of the as-quenched samples were performed at the selected temperatures referring to thermal properties that described by the differential thermal analysis. X-ray diffraction studies indicated that NaNbO3 and NaBa2Nb5O15 crystals formed as two main crystalline phases. Involvement of Nd3+ ions in the glass network suppressed precipitation of the NaBa2Nb5O15 phase. The dielectric constant measured at room temperature for glass-ceramic samples were found to sensitive to presence of NaBa2Nb5O15 phase. The present work showed that introduction of Nd3+ into the Na2O-BaO-Nb2O5-SiO2 glass-ceramics system induce slightly change of the dielectric properties.