BT-based Ceramics Research Articles

CaTiO3 nanoparticles as functional additives for the BaTiO3-based X8R type dielectric ceramics

This research investigates the potential of Calcium titanate (CaTiO3 or CT) nanoparticles as functional additives to enhance the dielectric properties of Barium titanate (BaTiO3 or BT)-based ceramic dielectrics. To address the need for high-temperature stability in MLCC (multilayer ceramic capacitor) applications, especially within the automotive and aerospace sectors, we have explored BT-based complex perovskite solid solutions comprising various cation substitutions, including Ca2+ and Yb3+, into barium titanate (BT) as a method to suppress the dielectric property anomaly near the Curie temperature effectively. The focus is on the impact of the application of CT nanoparticles as additive materials on phase formation, microstructure development, and dielectric behavior of the resulting ceramics to align with the Extended 'Temperature Coefficient of Capacitance (TCC)' criteria defined by the EIA X8R specification. When the hydrothermally synthesized CT nanopowder was applied in the Ca-doped BT ceramics fabrications as source material of the Ca dopants, it was beneficial to achieve both temperature stability and high dielectric constant. The CT nanoparticles are believed to play multiple roles during the solid-state reaction with BT and rare earth dopant (Yb). Since the Yb3+ ions can be more easily dissolved into the CT lattice than BT with their amphoteric character, the CT nanoparticles in the BT-CT-Yb2O3 mixture can act as an intermediary, dissolving the Yb3+ first in its A- or B-site before the final solid-solution formation with the BT. The sequential substitutions of the Yb3+ and Ca2+ into BT via CT nanoparticles could affect the site occupancy of Ca2+ in the BT lattice, which is very important in determining the dielectric properties of the Ca-doped BT processed in reducing atmospheres. Through a comprehensive experimental approach, including phase composition analysis via X-ray diffraction (XRD) and microstructural examination using Field Emission Scanning Electron Microscopy (FE-SEM) and Transmission Electron Microscopy (TEM), this work reveals the significance of synthetic methodology and dopant incorporation strategy on achieving a desired core-shell microstructure and improved dielectric performance. This research underscores the efficacy of CT nanoparticles as a promising route towards the development of BT-based dielectric ceramics with superior temperature stability, offering valuable insights for the advancement of MLCC technology to cater to high-temperature applications.

Electrocaloric response enhancement over a broad temperature range in lead-free BT-based ceramics

The electrocaloric effect (ECE) capabilities of environmentally sustainable BaTiO3 systems have garnered extensive scrutiny for their potential applications, owing to their intricate phase transition characteristics, facile miniaturization, heightened efficacy, and low cost. Nevertheless, persistent challenges loom in the quest for a substantial trade-off between significant temperature change (ΔT) and a wide operating temperature range (Tspan). In this study, we synthesized the Ba(1–1.5x)LaxTi0.9Zr0.1O3 (abbreviated as BLZT100x, x = 0, 0.005, 0.01, and 0.015) ferroelectric system and conducted thorough characterizations encompassing phase structure, electrical attributes, and electrocaloric properties. The results reveal a reduction in the phase transition temperature to lower regimes and an augmentation in the diffuse phase transition characteristics upon the incorporation of La3+ into the Ba(Zr, Ti)O3 matrix. This enhancement significantly bolsters the electrocaloric performance while expanding the viable operating temperature ranges. Notably, in the BLZT0.5 sample, an exceptional ΔT of 1.22 K under a moderate electric field of 50 kV/cm is observed, accompanied by an extraordinarily broad Tspan of 80 °C spanning from 60 °C to 140 °C, as determined through direct measurement method. These findings impeccably align with the prerequisites of practical refrigeration applications.

(Sb0.5Li0.5)TiO3-Doping Effect and Sintering Condition Tailoring in BaTiO3-Based Ceramics.

(1-x)(Ba0.75Sr0.1Bi0.1)(Ti0.9Zr0.1)O3-x(Sb0.5Li0.5)TiO3 (abbreviated as BSBiTZ-xSLT, x = 0.025, 0.05, 0.075, 0.1) ceramics were prepared via a conventional solid-state sintering method under different sintering temperatures. All BSBiTZ-xSLT ceramics have predominantly perovskite phase structures with the coexistence of tetragonal, rhombohedral and orthogonal phases, and present mainly spherical-like shaped grains relating to a liquid-phase sintering mechanism due to adding SLT and Bi2O3. By adjusting the sintering temperature, all compositions obtain the highest relative density and present densified micro-morphology, and doping SLT tends to promote the growth of grain size and the grain size distribution becomes nonuniform gradually. Due to the addition of heterovalent ions and SLT, typical relaxor ferroelectric characteristic is realized, dielectric performance stability is broadened to ~120 °C with variation less than 10%, and very long and slim hysteresis loops are obtained, which is especially beneficial for energy storage application. All samples show extremely fast discharge performance where the discharge time t0.9 (time for 90% discharge energy density) is less than 160 ns and the largest discharge current occurs at around 30 ns. The 1155 °C sintered BSBiTZ-0.025SLT ceramics exhibit rather large energy storage density, very high energy storage efficiency and excellent pulse charge-discharge performance, providing the possibility to develop novel BT-based dielectric ceramics for pulse energy storage applications.

Synthesis and Characterization of the Electrical and Energy Storage Properties of New Barium Titanate - Europium Titanate Solid Solution

In the present work, the investigation of the structural, dielectric, ferroelectric and energy storage properties of polycrystalline samples of (1-x)BaTiO3 – xEuTiO3 (BT-ET) solid solution materials prepared by conventional solid-state reaction method has been carried out. X-ray diffraction analyses have revealed the formation of a single-phase tetragonal structure with the P4mm space group. Furthermore, the temperature dependence of the dielectric constants marked the presence of the following sequence of structural phase transitions, namely from rhombohedral to orthorhombic, from orthorhombic to tetragonal and from tetragonal to cubic phase transitions with the increase of temperature. A diffuse phase transition has been observed from the dielectric permittivity peak and has been analyzed using the modified Curie-Weiss law and the degree of diffuseness is found to be in the range of 1.16 - 1.76 due to the existence of different states of polarization. A phase diagram has been established based on the temperature-dependent dielectric permittivity studies. The room temperature ferroelectric properties point to a coercive field larger than that of BaTiO3 ceramics. Broad dielectric peaks associated with diffuse phase transition appear in a wide temperature range (40 - 100 °C) with the highest dielectric permittivity ε’ = 6498 found in the x = 0.05 ceramics. Moreover, an improved energy storage performance is obtained in the 0.95BaTiO3-0.05EuTiO3 ceramic with a recoverable energy density of Wrec = 0.797 J/cm3, coupled with an efficiency η = 73% at 170 kV/cm and the highest storage energy density of Wst = 1.571 J/cm3 is obtained for 0.90BaTiO3-0.10EuTiO3, which is superior to other lead-free BT-based ceramics. All these features demonstrate that the BT-ET ceramics can be widely used in energy storage applications and also in high-temperature multilayer capacitors for automotive, aerospace and related industries.

Study on the phase structure and electrical properties of lead-free Barium titanate-based piezoelectric ceramic

Excessive Sr-doping has been observed to lead to a deterioration in the piezoelectric properties of BT-based ceramics. In response to this issue, this study introduces a solution through the development of lead-free piezoceramics using the composition (1-2x)Ba0.86Sr0.14Ti0.90Sn0.10O3-2xBa0.86Ca0.14Ti0.90Sn0.10O3 (BSTS-xBCTS), prepared through the conventional solid-state method. The rhombohedral, orthorhombic, and tetragonal phase coexistence is determined in the ceramic with 0.2≤x≤0.04. with x=0.3, the BSTS-xBCTS ceramic shows a sizeable piezoelectric property (d 33∼ 540 pC/N) and high ε r value (∼ 10280), superior or comparable to the other BT-based or lead-based ceramics. These results demonstrate that the electrical property of the BSTS-xBCTS ceramic exceeds those of some lead-based ceramics or equivalent and holds significant potential in various technological applications that require electrical materials.

Optimization of an indirect method for electrocaloric effect in BT-based ceramics validated through the Rayleigh relationship and direct method

Efforts to enhance refrigeration efficiency and environmental friendliness are underway, focusing on the electrocaloric effect (ECE) as an alternative to traditional compression methods.

Improving energy storage performance of barium titanate-based ceramics by doping MnO2

MnO2 was used as a sintering additive to reduce sintering temperature of the 0.92(Ba0.94Li0.02La0.04)(Mg0.04Ti0.96)O3-0.08Bi(Zn1/2Ti1/2)O3 (0.92BLLMT-0.08BZT) ceramic thick film and promote sintering process. At the same time, MnO2 doping is beneficial for reducing dielectric loss and leakage current, and improving insulation performance, thus, breakdown field strength (BDS) of ceramics is increased. In addition, MnO2 doping introduces defect energy levels, and increases lattice distortion and polarization intensity, thereby changing the crystal structure and microstructure morphology, and improving energy storage density and thermal stability. The BDS reaches 650 kV/cm electric field with 0.5 mol% MnO2 doping, where the ceramic thick film achieves a discharge density (Wdis) of 5.51 J/cm3, ultra-high power density (PD = 443.87 MW/cm3) and current density (CD = 1365.74 A/cm2). The ceramic thick film exhibits good thermal stability with Wdis change rate of only 16.47 % within room temperature to 170 °C under 200 kV/cm. Such excellent comprehensive performance can be attributed to the decrease of grain size, defect concentration, and leakage current, and the formation of polar nano regions in the BT-based ceramics caused by MnO2 doping and cations substitution at A-site and B-site of the perovskite structure. This study provides valuable insights for the research of lead-free dielectric ceramic capacitors, and the 0.92BLLMT-0.08BZT-0.5 mol% Mn ceramic thick film presents good development prospect in high-power pulse energy storage system.

Achieving high energy storage density and excellent stability in BiScO3 modified BaTiO3-based ceramics

High-performance dielectric energy storage ceramics has been brought to the fore by data as a result of the rapid rise in new energy development. The dielectric energy storage materials that can withstand harsh environments while having excellent energy storage performance, large breakdown strength, and maximum polarization is highly demanding. Herein, we fabricated the BiScO3 (BS) modified 0.88(Ba0.6Ca0.4)TiO3-0.12Bi[Mg2/3(Nb0.85Ta0.15)1/3O3] (BCT-BMNT) ceramics with excellent energy storage performance. The experimental results revealed that the breakdown strength of BCT-BMNT-xBS ceramics can be substantially increased by careful engineering of the grain uniformity induced by the incorporation of the BS. The BCT-BMNT-0.2BS ceramic exhibited a considerably optimal recoverable energy storage density of 5.75 J/cm3 along with a high energy efficiency of 89.63 % at 650 kV/cm. Moreover, this sample showed good stability in the temperature range of 20–160 °C and frequency range of 1–500 Hz and excellent fatigue resistance up to 105 cycles. Regarding the pulsed performance, as-prepared sample exhibited excellent power density of 145.30 MW/cm3 and current density of 937.43 A/cm2. Meanwhile, it showed a fast discharge time (t0.9) of 50.20 ns under the electric field of 460 kV/cm. This study demonstrates the crucial role that BS doping plays in improving the energy storage capabilities of BT-based lead-free ceramics, which pave the way for the use of BT-based ceramics in the field of energy storage.

Significant improvement in energy storage for BT ceramics via NBT composition regulation

Dielectric ceramic capacitors play an important part in modern electronics, but the adoption of environmentally friendly lead-free ceramics is often limited by their inferior energy storage efficiency (η) and density (Wrec). One novel ceramic composition, (1-x)(Ba0.7Sr0.3)(Zr0.2Ti0.8)O3-xNa0.5Bi0.5TiO3 (BSZT-NBT, x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) was designed to achieve large max polarization (Pmax) and outstanding energy storage performance (ESP). Structural analyses indicate that BSZT-NBT ceramics form stable perovskite solid solutions. Dielectric properties testing confirms the enhanced relaxor behavior. Remarkably, the BSZT-NBT (x = 0.5) ceramics exhibit superb ESP, including ultrahigh η of 94.9%, elevated Wrec of 4.45 J·cm–3, large Pmax of 38.01 μC·cm–2. Furthermore, these ceramics demonstrate excellent temperature and frequency stability for ESP. Charge-discharge performance at room temperature and 120 kV·cm–1 showcases excellent Wdis, t0.9 and PD of 0.64 J·cm–3, 69.8 ns and 48 MW·cm–3, respectively. Our results indicate that the introduction of NBT effectively improves the Pmax and ESP of BT-based ceramics. The BSZT-NBT ceramics hold promise for addressing the limitations of lead-free ceramic capacitors and advancing their practical applications in electronic devices.

Relaxor ferroelectric ceramics with excellent energy storage density obtained from BT-based ceramics

Lead-free energy storage ceramic capacitors which have high-power density and ultrafast discharge time are widely used in electronic systems. However, lead-free energy storage ceramic materials still suffer from low energy storage density and poor stability. In this study, the synergistic optimization of polarization and electric field breakdown strength (Eb) is realized by doping with highly polarized Bi0.5Na0.5TiO3 (Ps > 42 μC/cm2) in BaTiO3-based ceramics, thereby optimizing the energy storage density. 0.15BNT ceramics have a large ΔP (Pmax-Pr) of 29 μC/cm2 under Eb of 525 kV/cm, resulting in excellent total energy storage density (Wtotal = 5.4 J/cm3), large recoverable energy storage density (Wrec = 4.8 J/cm3) and high energy storage efficiency (η = 89%). In particular, 0.15BNT ceramics also exhibit a high-power density (PD = 80 MW/cm3), a large discharge density (Wdis = 1.9 J/cm3), and an ultrafast discharge time (t0.9 = 37 ns). In addition, 0.15BNT ceramics also show excellent frequency stability (1–120 Hz) and temperature stability (25–200 °C). These excellent properties establish that 0.15BNT ceramics are promising material candidates for applications.

Improved energy storage performance of lead-free BaTi0.96Li0.04O2.94 ceramics via domain structure engineering

BaTiO3 (BT) ceramics with excellent energy storage performance (ESP) are in great demand in the power electronics industry due to their high power density. However, the traditional BT-based ceramics cannot simultaneously achieve high breakdown strength and high maximum polarization. Here, we bring forth ideas of design strategy to promote the ESP of the BaTi0.96Li0.04O2.94 ceramics by domain structure engineering to construct the special crossover region between ferroelectric and relaxor ferroelectric state, which possesses ferroelectric domains of different scales. The Bi(Mg2/3Ta1/3)O3-doped ceramic shows high energy storage density of 3.28 J/cm3 with slim hysteresis loop at large BDS of 380 kV/cm, and accompany with high efficiency of 88.52%. The ESP are less than 3% at the temperature range of 20∼200 °C, and the ceramic exhibits outstanding temperature stability. Our work demonstrates that the crossover region in BT ceramics is conducive to obtaining excellent ESPs, providing a reference for the structural optimization of high-performance BaTiO3 ceramics.

Dielectric and anti-reduction properties of BaTiO3-based ceramics for MLCC application

BaTiO3 ceramics doped with different contents of Co2O3(abbreviated as (1-x) BT-xCo2O3) and (1-x) BaTiO3-xBiCoO3(abbreviated as (1-x) BT-xBC) ceramics were prepared via conventional solid-state process and sintered in reducing atmosphere. The main crystal phase of both ceramic samples was characterized by X-ray diffraction (XRD), which was perovskite structure. Compared with (1-x) BT-xCo2O3, (1-x) BT-xBC ceramic samples were dense with uniform microstructure confirmed by scanning electron microscopy (SEM). The 0.95BT-0.05BC ceramics had good dielectric properties, with ε25°C = 2670, tanδ = 0.012, and resistivity was 1.71 × 1011 Ω cm at 25°C, meeting the X7S standard for multilayer ceramic capacitor (MLCC) applications. The mechanism of improved anti-reduction property of (1-x) BT-xBC ceramics was studied by X-ray photoelectron spectroscopy (XPS) and thermally stimulated depolarization current (TSDC) techniques. The XPS results showed that there were two valence states of Co in 0.95BT-0.05BC and 0.95BT-0.05Co2O3 ceramics, indicating that the introduction of Co can improve anti-reduction property of BT-based ceramics. The TSDC revealed the formation of defect dipoles [2CoTi’−Vo▪▪], which was considered to be the cause for the improvement in anti-reduction property.

Synergic and competitive effect of A-site substitution on structure and electric property in BaTiO3-based ceramics

Sites engineering has been extensively investigated in BaTiO3-based lead-free materials. Although the effect of A or B site substitution on structure and electric properties have been researched adequately, the synergic and competitive impacts of doping element have received little attention, which has become an urgent issue for further optimizing performance. Here, three groups BT-based ceramics [0.6(Ba0.9Ca0.1)TiO3-0.4Ba(Sn0.2Ti0.8)O3, B(Ca)TS, 0.6(Ba0.9Ca0.05Sr0.05)TiO3-0.4Ba(Sn0.2Ti0.8)O3, B(Ca,Sr)TS, and 0.6(Ba0.9Sr0.1)TiO3-0.4Ba(Sn0.2Ti0.8)O3, B(Sr)TS] are synthesized by normal sintering, revealing the synergic and competitive mechanism of A site doping on structure and properties. The effect of Ca2+ and Sr2+ are quite different on the structure, especially the phase structure and grain size, and the evolution of electric properties (e.g., d33, Strain, and Temperature stability) results from structure caused by the synergic and competitive effect of Ca2+ and Sr2+. For example, a large d33 (∼950 pC/N) is obtained in B(Sr)TS due to its closer R-O-T phase structure compared to B(Ca)TS and B(Ca,Sr)TS ceramics, which is superior to some previous BT-based studies. Therefore, exploring of doping mechanism can further tune the microscopic structure and thus enhance electric properties, accelerating the practical process of lead-free ceramics.

Regulating ferroelectric polarization and dielectric properties of BT-based lead-free ceramics

The ternary system of BaTiO3 (BT) -based lead-free ceramics ((1-x)BaTiO3-x(0.94 Sr0.7Bi0.2TiO3-0.06BiMg0.5Ti0.5O3) are investigated on their structural, dielectric and ferroelectric properties. The structural evolution is identified from the tetragonal phase (P4mm) to the pseudocubic phase with increasing the dopant concentration x. The gradually diffusive dielectric peak and highly dispersive relaxor behaviors are recognized, indicating the transformation from ferroelectric to relaxor state. Meanwhile, the ceramics are characterized by the slim polarization hysteresis loops associated with polar nano-sized cluster formation. Complex impedance spectroscopy reveals the electrical inhomogeneities with enhanced boundary effect caused by the excessive addition, leading to the abnormally degraded electric breakdown strength. Combined with the X-ray photoelectron spectroscopy, the oxygen vacancy hopping mechanism is proposed for the high dopant concentration, contributing to the diffuse dielectric response. As a result, optimized energy-storage density and efficiency are simultaneously obtained at a relatively low electric field. All these features demonstrate an effective route in the composition modulation of BT-based dielectric capacitor ceramics that not only the formation of polar nano regions but also the electrical homogeneities can greatly influence the comprehensive dielectric performance.

Tuning the electrocaloric effect by tailoring phase fraction in BaTiO3-based ferroelectrics

The giant electrocaloric effect (ECE) in ferroelectrics arouses enthusiasm on the electrocaloric refrigeration for its zero global-warming-potential. Previous studies have observed that large ECE response occurs around ferroelectric-paraelectric phase transition in BaTiO3-based ferroelectrics. However, few attention is paid to the effect of phase fraction on ECE performance. In this work, Ba1-xSrxTi0.95Sn0.05O3 ceramics which display varied phase fraction of orthorhombic and tetragonal (O and T) phase at room temperature, are developed to reveal the influence of phase fraction on the electric properties, especially ECE performance. The electrocaloric temperature change (ΔT) is enhanced in composition with equal phase fraction of O and T, which also shows excellent piezoelectric property. Intrinsically, a number of nanodomains are formed due to the incorporation of Sr2+, greatly benefiting the invertibility of domains under the electric field. It is believed that this study opens a new way for designing and understanding of ECE in BT-based ceramics.

Multiscale Structure Engineering for High-Performance Pb-Free Piezoceramics

ConspectusThe increasing world energy crisis drives humans to harvest the energy in nature as much as possible without heavily damaging the environment. However, most of the energy in nature cannot be used directly. Therefore, pursuing technologies or matter that can directly interconvert different energies has been one of the most cutting-edge fields in science and technology. Such a magic ability exists in true-life piezoelectric materials that generate charge when being given a force and vice versa, rendering them highly promising for energy harvesting and conversion because of the tremendous mechanical energy on the earth, such as tide energy. Thus, piezoelectric materials, represented by the lead zirconate titanate (Pb(Zr, Ti)O3, PZT) family, have been largely used in various traditional and burgeoning fields, such as electronic information, biomedical treatment, and wearable flexible electronic devices, and are one of the most important favorites in multidisciplinary fields. However, Pb is highly toxic. Driven by environmental protection and concern for human health, Pb-free piezoceramics are rapidly being developed to hopefully replace Pb-based ones. In particular, the renewal of Restriction of the use of certain Hazardous Substances (e.g., RoHS 2), issued by the European Union, declared that replacement of PZT “...may be scientifically and technologically practical to a certain degree...”. Therefore, developing high-performance Pb-free piezoceramics has become more urgent than ever. In this context, some Pb-free piezoceramics, represented by potassium sodium niobate ((K, Na)NbO3, KNN), barium titanate (BaTiO3, BT), bismuth barium titanate ((Bi, Na)TiO3, BNT), and bismuth ferrite (BiFeO3, BFO), stand out because of their unique or similar traits. However, several key challenges, including an inferior overall performance compared to Pb-based counterparts and an unclear structure–property relationship from multiscale viewpoints, have severely hindered the development of Pb-free piezoceramics for a long time.Pb-based piezoceramics possess decent performance due to the strategy of phase boundary engineering, which inspired the researchers to pursue it in Pb-free counterparts. In the last 10 years, our group has been aiming at the new phase boundary (NPB) and new physical phenomenon in Pb-free piezoceramics. This Account presents our recent contributions to the development of Pb-free piezoceramics concerning the good performance and emerging phenomenon. First, we introduce the construction of the NPB in KNN-based piezoceramics by emphasizing the role of some key elements (i.e., Bi, Sb, Zr, and Hf). Then, we summarize the effects of the NPB on KNN- and BT-based ceramics and the new physical phenomenon in BNT-based ceramics. The NPB boosts the piezoelectric properties and temperature stability of KNN- and BT-based piezoceramics, comparable to some Pb-based piezoceramics. Combining the NPB and the multilayer ceramics substantially enhances the temperature stability of the piezoelectric constant. A new physical phenomenon of the nanoscale bubble domains with polar topologies is for the first time revealed in BNT-based ceramics, showing potential applications for nonconventional and high-density nonvolatile memories. In particular, we emphasize structure engineering from multiscale viewpoints including the local, microscopic, mesoscopic, and macroscopic structure (e.g., lattice structure, ferroelectric domains, and phase structure). Finally, we provide perspectives on the future developments of Pb-free piezoceramics toward practical applications.

The effect of rare-earth oxides on the energy storage performances in BaTiO3 based ceramics

In this work, 0.7BaTiO3-0.3Sr0.2Bi0.7TiO3 (0.7BT-0.3SBT) ceramics with 0.15 mol% various rare-earth oxides doped are designed and synthesized by the conventional solid-state route. All prepared samples exhibited a single perovskite phase and dense microstructure with fine grain size (0.2–0.5 μm) after sintering at 1180 °C. Especially, the Gd-doped 0.7BT-0.3SBT ceramics exhibited excellent energy storage performances; the corresponding recoverable energy density and efficiency were 3.2 J/cm3 and 91.5% under an electric field of 330 kV/cm, respectively. Meanwhile, doping with Gd caused the BT-based ceramics to possess excellent temperature (30–150 °C) and outstanding frequency stabilities (10–1000 Hz). Moreover, the pulsed charge-discharge experiments revealed that a high power density of 59 MW/cm3 and a fast discharge speed of 110 ns with outstanding temperature stability could be synchronously obtained in the Gd-doped composition. All these features are attractive for pulsed power applications.

Investigation of the effect of Sr-substitution on the structural, morphological, dielectric, and energy storage properties of BaTiO3-based perovskite ceramics

In this work, Ba1-xSrxTiO3 (x = 0 and x = 0.3) samples, abbreviated respectively BT and BST, have been prepared by conventional solid state reaction. The pure phase formation and crystal structure were approved by X-ray powder diffraction analysis. The morphology of these samples were inspected by the transmission electron microscopy. The structural and morphological findings were confirmed by Raman measurements. The effect of the substitution of barium by strontium on the dielectric properties and on the energy storage of these compounds which has been discussed. In this issue, the results indicate the improvement of the dielectric properties of BT-based ceramics by substitution of Ba by Sr due to the decrease in dielectric losses and especially to the appearance of a relaxor behavior for the BST compound in the vicinity of room temperature. However, the P–E loops have proven a degradation of energy storage properties by Sr-substitution in BT ceramics.

Structure and Electrical Properties of Microwave Sintered BTS-BCT-xBF Lead-Free Piezoelectric Ceramics.

Barium titanate (BT)-based ceramics are one of the promising piezoelectric materials for environment-friendly electro-mechanical transformation. However, high performance materials are often sintered at high temperatures, resulting in volatile components and increased energy consumption. Here, 0.82Ba(Ti0.89Sn0.11)O3-(0.18-x)(Ba0.7Ca0.3)TiO3-xBiFeO3 (BTS-BCT-xBF) piezoelectric ceramics were prepared by microwave sintering (MWS) method, and the structure and properties were emphatically studied, aiming to reveal the regulatory mechanism of MWS on the structure and properties. Compared with conventional solid sintering (CS), the phase structure presents a similar evolution in MWS ceramics as a function of BF, while the more refined grain size and the denser structure are observed in MWS ceramics. The electrical properties (e.g., d33, εr, tan δ, etc.) of MWS ceramics are superior to the CS ceramics owing to the refined grain size and denser microstructure. It is worth noting that the energy storage performance (e.g., energy storage density, energy storage efficiency) significantly outperformed expectations due to the slender hysteresis loop resulting from the smaller grain and high cubic phase. Therefore, the MWS sintering mechanism can further drive practical application of BT-based ceramics.

Charge compensation mechanisms of BaTiO3 ceramics co-doped with La2O3 and Bi2O3

Doping modification is commonly used to improve the electrical properties of BaTiO 3 (BT). In this study, the ((1- x )BT- x (Bi 2 O 3 –La 2 O 3 )) ceramics were synthesised to investigate the charge balance compensation mechanisms of BT ceramics co-doped with La 2 O 3 and Bi 2 O 3 as donors at A-site. The XRD results showed that a pseudo-cubic phase was formed by intruding dopants. The Raman spectroscopy revealed that the samples, which x = 0.10 and 0.16, had relatively more oxygen and titanium vacancies. After heat-treatment the samples in oxygen atmosphere, the dielectric constant of the sample with x = 0.10 was higher than that of the untreated, but for x = 0.16, it was almost no changed. These results indicated that the different charge balance compensation mechanism was exist in the samples with x = 0.10 and 0.16. Impedance measurements showed that the resistance tendency exhibited initial decrease and subsequent increase, leading to the electronic and ionic compensation mechanisms with x = 0.10 and 0.16, respectively. Ferroelectric properties also implied charge balance compensation mechanism transition, due to P s and P r were higher for x = 0.10 than for x = 0.16, respectively. This work provides a new strategy for modulating the electric properties of BT-based ceramics.