BaTiO3-based Ceramics Research Articles

Realising high comprehensive energy storage performance of BaTiO3-based perovskite ceramics via La(Zn1/2Hf1/2)O3 modification

Novel Pb-free (1-x)BaTiO3-xLa(Zn1/2Hf1/2)O3 (BT-xLZH, 0 ≤ x ≤ 0.12) ceramics were ingeniously designed and synthesized through the conventional solid-phase technology. Slim unipolar P-E ferroelectric loops, higher polarisation difference (ΔP, ΔP = Pm–Pr), and breakdown strength were obtained in the LZH-modified BT ceramics. Excellent energy storage efficiency (η = ∼90.22%) and recoverable energy storage density (Wrec = ∼3.27 J/cm3) for the 0.92BaTiO3-0.08La(Zn1/2Hf1/2)O3 ceramics were achieved under 480 kV/cm. The BT-xLZH (x = 0.08) ceramics show good frequency stability at 1–200 Hz and thermal stability at −25 °C to 60 °C. Charge/discharge experiments indicate that BT-0.08LZH ceramics can release high energy density and have a short discharge time (t0.9 = 4.4 μs). Therefore, it is potential to develop a new generation of energy-saving and environment-friendly dielectric capacitors.

Microstructure and electrical performance of Sm2O3-doped BCTSG lead-free ceramics

This work aims to upgrade the comprehensive electrical properties of BaTiO3-based ceramics (1-x)[(Ba0.94Ca0.06)(Ti0.92Sn0.08)]-xSm2O3-0.06 mol% GeO2 [abbreviated as (1-x)BCTS-xSm-0.06G]. First, piezoceramics were synthesized via a conventional solid-state method. Next, the phase structures, surface topographies, ferroelectric domains were evaluated using XRD, XRD Rietveld refinements, SEM, OP-PFM, TEM. The results demonstrate that all the ceramics possess an orthorhombic-tetragonal (O-T) phase when at room temperature. Significantly, optimized piezoelectricity is gained at x = 0.03 mol% (piezoelectric constant of d33 = 630 ± 20 pC/N and planar electromechanical coupling factor of kp = 61%). The ferroelectric domains of ceramics were examined using OP-PFM and TEM, which ulteriorly indicate that the favorable piezoelectricity is attributed to the coexistence of the O-T phase boundary and the subdued energy density of the domain wall. Furthermore, all the ceramics are confirmed to be relaxor ferroelectrics, with the relaxor degree increasing with the increasing content of Sm2O3.

The interaction of oxygen with manganese and its effect on surface state properties in PTCR BaTiO3

Semiconducting BaTiO3-based ceramics with varying manganese (Mn) acceptor concentrations (0.048–0.112 mol%) are systematically examined. By optimizing the Mn content, ceramics with electrical breakdown field strengths as high as 600 V/mm with simultaneous low decrease of resistance below phase transition (Rmin/R25 = 0.78) temperature are achieved. The observed differences in electrical properties are ascribed to modifications in grain boundary surface state properties. 18O tracer experiments at 800 °C reveal a clear enhancement of oxygen diffusivity with increasing Mn concentration. The comparison with resistance–temperature (R–T) characteristics indicates the simultaneous presence of various acceptors (e.g., adsorbed gases, Mn4+/3+, Mn3+/2+) with different energy levels and suggests a direct correlation between surface trap formation and oxygen diffusivity. We propose that the interaction of Mn with oxygen determines the number of surface states but also the depth of their energy level within bandgap, defining the resulting form of the R–T characteristic.

Reduced leakage current and excellent thermal stability in lead-free BiFeO3–BaTiO3-based piezoelectric ceramics

Reduced leakage current and excellent thermal stability in lead-free BiFeO3–BaTiO3-based piezoelectric ceramics

Large piezoelectricity in NaNbO3-based lead-free ceramics via tuning oxygen octahedral tilt.

The development of high-performance lead-free piezoceramics for replacing Pb-based perovskites has attracted lots of attention, and comparable room-temperature piezoresponse has been realized in (Na,K)NbO3 and BaTiO3-based ceramics with local structure heterogeneity via adjusting polymorphic phase boundary. In this work, a new method of oxygen octahedron tilt design is used in NaNbO3-based lead-free ceramics, which usually shows complex oxygen octahedron tilt information inherited from NaNbO3. The substitution of Ba(Fe0.5Nb0.5)O3 and BaTiO3 with high tolerance factor into NaNbO3 leads to a gradual elimination of anti-parallel cation displacement and anti-phase tilt along the three axes; as a result, a single tetragonal phase with P4bm space group and only in-phase tilt along c axis is achieved in 0.88NaNbO3-0.04Ba(Fe0.5Nb0.5)O3-0.08BaTiO3 ceramic. Accompanying the decreased oxygen octahedral tilt degree, a drastically improved d33 up to 367 pC N-1 (over ten times that of NaNbO3 ceramic) is obtained, reaching a record high in NaNbO3-based lead-free ceramics. Together with temperature insensitive piezoresponse originating from thermally stable oxygen octahedral tilt structure, the studied NaNbO3-based materials show large potential for replacing Pb-based ceramics in some electronic devices. The oxygen octahedron tilt engineering would be used for designing more high-performance lead-free ceramics with high piezoresponse and excellent thermal stability simultaneously.

Abnormal Grain Growth and Electrical Properties of Batio3-Based Ptcr Ceramics Prepared from Nanopowder by Reduction-Reoxidation Method

Abnormal Grain Growth and Electrical Properties of Batio3-Based Ptcr Ceramics Prepared from Nanopowder by Reduction-Reoxidation Method

Effects of Zn2+/Mg2+ ratio on dielectric properties of BaTiO3-based ceramics with excellent temperature stability: Experiments and the first-principle calculations

To satisfy the development of MLCC devices, the dielectric properties and temperature stability of ceramic materials urgently needs to be improved. In our work, the 0.9BaTiO3-0.1Bi(ZnxMg0.5-xY0.5)O2.75 ceramics with x=0.0–0.5 are successfully prepared based on a traditional solid-state method. Meanwhile, the ceramic sample (core-shell structure) with x = 0.1 exhibits excellent dielectric properties and temperature stability (εr: 1207, tanδ: 0.009 and εr/ε25 ≤±15% within −80 to 200 °C), which satisfies the Electronic Industries Association (EIA) X9R (-55–150 °C, Δεr/ε25 ≤±15%) specification. In addition, the physical mechanism behind dielectric properties and temperature stability is systematic investigated based on experimental characterization and the first-principle calculations. The interface polarization is regarded as the primary cause affecting the dielectric properties, and has a close relationship with shell structure of ceramic samples. The lattice deformation of shell structure is caused by the introduction of heterovalent ions and non-equivalent substitution. Dielectric constant may be advance as content of Zn2+ ions increases due to the electronic enrichment around the zinc site in distorted lattice matrix. However, the weaken force between atom and electron results in the poor temperature stability.

Effects of sintering temperature and Bi2O3, Y2O3 and MgO co-doping on the dielectric properties of X8R BaTiO3-based ceramics

Bi 2 O 3 , Y 2 O 3 and MgO co-doped BaTiO 3 (BT)-based X8R ceramics were synthesized successfully for the first time. The effects of the sintering temperature and Bi 2 O 3 , Y 2 O 3 and MgO dopants on the dielectric properties were investigated systematically. Bi 2 O 3 doping can increase the Curie temperature ( T c ), but reduces the overall dielectric permittivity. On the other hand, Y 2 O 3 doping is beneficial to the formation of core-shell microstructure and the increase of T c , whereas MgO can prevent excessive Y 2 O 3 from diffusing into grain core, and thereby further contributes to the generation of the core–shell microstructure. The generation of the typical core-shell microstructure was confirmed and investigated in detail by using transmission electron microscopy (TEM). It is argued that the synergistic effects of Bi 2 O 3 , Y 2 O 3 and MgO co-doping in terms of the formation of the core-shell structure and the increase of T c , can help improve the temperature stability of the dielectric permittivity effectively. Increasing the sintering temperature leads to an increase in the grain size, which in turn leads to an increase in the overall dielectric permittivity due to the grain size effect.

Effects of Hf4+ substitute on the enhanced electrostrain properties of 0.7BiFeO3-0.3BaTiO3-based lead-free piezoelectric ceramics

The 0.7Bi1.05FeO3-0.3BaHfxTi(1−x)O3 (BF-BHT-x) ceramics are prepared by using conventional method. The mechanism of large electric-induced strain is studied in detail through Rietveld refinement, transmission electron microscopy (TEM), and piezoelectric force microscopy (PFM). The BF-BHT-0.05 ceramics, which possess the coexistence of cubic (Pm-3m) and rhombohedral (R3c) phase proved by Rietveld refinement and TEM measurement, have the maximum electric-induced strain of Smax = 0.58% at 130 kV/cm (1 Hz). The reduced potential barrier is beneficial to the switching and reorientation of domain under an external electric field due to the coexistence of cubic and rhombohedral phase. A mass of nanodomains embedded into the microdomains, which is conducive to domain switching, are observed obviously through PFM. Therefore, the findings show that the large strain is because the external electric field drives the conversion mixed phase into the major rhombohedral phase, the reduced potential barrier, and the nanodomain in macrodomain.

Machine-Learning-Enabled Prediction of Adiabatic Temperature Change in Lead-Free BaTiO3-Based Electrocaloric Ceramics.

In this paper, we develop a data-driven machine learning (ML) approach to predict the adiabatic temperature change (ΔT) in BaTiO3-based ceramics as a function of chemical composition, temperature, and applied electric field. The data set was curated from a survey of published electrocaloric measurements. Each chemical composition was represented by elemental descriptors of A-site and B-site elements. Pair-wise statistical correlation analysis was used to remove linearly correlated descriptors. We trained two separate regression-based ML models for indirect and direct measurements and found that both are capable of capturing the general trend of the temperature vs ΔT curve for various applied electric fields. We then complemented the regression models with a classification learning model that predicts the expected phase as a function of chemical composition and temperature. The combined regression and classification learning ML models predict a global maxima in ΔT near rhombohedral to cubic or tetragonal to cubic phase transition regions. An interactive, open source web application is developed to enable interested users to query our trained models and accelerate the design of novel BaTiO3-based ceramics with targeted phase and ΔT properties for electrocaloric applications.

Modification of grain boundary potential barriers by annealing treatments of PTCR ceramics with identical microstructure and room-temperature resistivity

Semiconducting BaTiO3-based ceramics originating from the same starting powder batch were subjected to different oxidative post-sintering treatments at temperatures between 800 °C and 1200 °C. The annealing profiles were chosen in a way to result in ceramics with same room-temperature and microstructure. However, the different annealing procedures clearly affected the resulting PTCR characteristics above and below the phase transition temperature. Observed changes in electrical properties were investigated by capacitance-voltage measurements and x-ray diffraction. It was found that annealing treatments influence the grain boundary potential barrier height and width by modifying the equilibrium concentration of cation and oxygen vacancies. Moreover, oxidative annealing at 1100 °C appears to influence the temperature development of spontaneous polarization by filling up oxygen vacancies within the grain bulk. These findings not only extent existing knowledge about defect equilibria in barium titanate but also emphasize the strong impact of process parameters on electrical properties of electroceramics.

Dielectric properties, microstructure and charge compensation of MnO2-doped BaTiO3-based ceramics in a reducing atmosphere

Based on the relationship of dipole formation and charge compensation, we prepared BaTiO3-based (x%MnO2-0.05%Nb2O5–BaTiO3, x%Mn–Nb-BT) ceramics using a solid-phase reaction in air and a reducing atmosphere. The influences of MnO2 doping and sintering atmospheres on crystal structure, charge compensation and dielectric properties were comprehensively studied. The ion substitution mechanism, solid solubility, and crystallinity of x%Mn–Nb-BT ceramics in different atmospheres were resolved by X-ray diffraction (XRD) and electron paramagnetic resonance (EPR) spectroscopy. X-ray photoelectron spectroscopy (XPS) showed that the percentages of oxygen vacancy and Ti3+ in this system were both affected by MnO2 doping and the atmosphere due to the reducibility of Mn4+ and the reducing atmosphere. Thus, the influence of doped MnO2 and the atmosphere on dipole formation and charge compensation was deeply discussed. These results provide further insight into the important role of MnO2 in improving the anti-reduction performance of BT-based ceramics.

Polymorphic Phase Transition and Piezoelectric Performance of BaTiO3-CaSnO3 Solid Solutions

BaTiO3-based piezoelectric ceramics have attracted considerable attention in recent years due to their tunable phase structures and good piezoelectric properties. In this work, the (1 − x)BaTiO3−xCaSnO3 (0.00 ≤ x ≤ 0.16, abbreviated as BT−xCS) solid solutions, were prepared by traditional solid-state reaction methods. The phase transitions, microstructure, dielectric, piezoelectric, and ferroelectric properties of BT-xCS have been investigated in detail. The coexistence of rhombohedral, orthorhombic, and tetragonal phases near room temperature, i.e., polymorphic phase transition (PPT), has been confirmed by X-ray diffraction and temperature-dependent dielectric measurements in the compositions range of 0.06 ≤ x ≤ 0.10. The multiphase coexistence near room temperature provides more spontaneous polarization vectors and facilitates the process of polarization rotation and extension by an external electric field, which is conducive to the enhancement of piezoelectric response. Remarkably, the composition of BT-0.08CS exhibits optimized piezoelectric properties with a piezoelectric coefficient d33 of 620 pC/N, electromechanical coupling factors kp of 58%, kt of 40%, and a piezoelectric strain coefficient d33* of 950 pm/V.

The role of SiO2 in semiconducting BaTiO3-based ceramics: Extension of the Jonker model and effect on the electrical properties

BaTiO3-based ceramics with positive temperature coefficient of resistance (PTCR) recently gained in significance due to their application as cabin heaters in electrical vehicles. Although used as a sintering aid in BaTiO3 ceramics for decades, the effect of SiO2 on the electrical properties as well as the underlying physical mechanisms have not been investigated in detail. Here, we systematically study the influence of SiO2 on PTCR properties, but also on the resistance development at temperatures below the PTC regime, which has hardly been given attention to so far. Using capacitance-voltage measurements, we determine temperature dependent grain boundary potential barrier parameters. By combining these results with x-ray diffraction measurements and resistance-temperature properties, we propose a model describing the resistance evolution throughout the whole temperature range from room-temperature up to the PTCR regime. Further, we show that electrical field strength increases with higher SiO2 content, accompanied by a reduced voltage sensitivity of resistance.

Effect of Bi2O3 and Ho2O3 co-doping on the dielectric properties and temperature reliability of X8R BaTiO3-based ceramics

Bi2O3 and Ho2O3 co-doped BaTiO3 (BT)-based X8R ceramics were successfully synthesized by the conventional solid-state reaction route. The synergistic effects of Bi3+ and Ho3+ co-doping on the dielectric performance and microstructures of BT-based ceramics were studied. The results show that by carefully adjusting the Bi2O3 and Ho2O3 doping concentrations, the temperature stability of the dielectric permittivity in BT-based ceramics can be significantly improved. Co-doped samples with 0.75%–1.5 mol% Bi2O3 and Ho2O3 meet the X8R specification. In particular, the 0.75 mol% Bi2O3 and 0.75 mol% Ho2O3 co-doped BT-based ceramics exhibit an optimum dielectric permittivity and a satisfactory temperature coefficient of capacitance (TCC) stability: the dielectric permittivity and dielectric losses are 2668 and 1.35% respectively at room temperature, the TCC at −55 °C and 150 °C is −0.92% and −9.56%, respectively. Transmission electron microscopy (TEM) analysis confirmed the formation of a core-shell microstructure in Bi2O3 and Ho2O3 co-doped BT-based ceramics. The synergistic effect of Bi3+ and Ho3+ co-doping plays a vital role in the production of the core–shell microstructure, which in turn is the main reason for the effective improvement of the TCC stability of BT-based ceramics.

Large electromechanical strain response in BiFeO3–BaTiO3-based ceramics at elevated temperature

An approach of composition modification in (Bi,Na,Ba,Sr)(Ti,Nb,Zr)O3 (BNSTNZ)–modified 0.65Bi1.05FeO3–0.35BaTiO3 (BF35BT) piezoelectric materials was investigated. Introducing BNSTNZ into BF35BT ceramics led from the normal-ferroelectric to relaxor-ferroelectric- phase. At the optimum composition, large dynamic piezoelectric coefficient (d33*) of 583 pm/V under the applied field of 5 kV/mm and relatively high static piezoelectric coefficient (d33) of 135 pC/N with high maximum temperature (Tm ≤ 400 °C) were obtained. The unipolar strain and d33* of BNSTNZ into BF35BT ceramics with x = 0.005 increased up to 0.251% and 718 pm/V at 90 °C. The remarkably enhanced field-induced strain response of BF35BT-based compositions is believed to be attributed to the optimum grain size, high tetragonality and the ferroelectric-relaxor phase coexistence. It is noted that this composition can be a favorable lead-free candidate for high-temperature piezoelectric applications.

Optimized energy storage properties of BaTiO3-based ceramics with enhanced grain boundary effect

Optimized energy storage properties of BaTiO3-based ceramics with enhanced grain boundary effect

Hybrid inks for 3D printing of tall BaTiO3-based ceramics

Ink formulation is one of the main challenges with ceramic 3D printing. Here, we present a new, reactive-colloidal hybrid ink for 3D printing by robocasting of BaTiO3-based ceramics. The hybrid ink combines a titanium isopropoxide-based sol-gel base with a colloidal dispersion of powder, here demonstrated with BaTiO3 both as the sol-gel (by reaction of titanium isopropoxide and barium oxide) and colloidal (by addition of BaTiO3 powder) parts. Addition of glycerol was necessary to avoid fast precipitation and poor dispersion of BaTiO3 from the reaction of BaO and Ti-isopropoxide. With a solid loading of 40 ​vol% BaTiO3, 10 ​mm tall structures could be printed with minimal deformation from slumping. The BaTiO3 shows good piezo-, ferro- and dielectric properties after sintering, with a piezoelectric charge coefficient (d33 ​= ​159 ​pC/N) in the range commonly reported for BaTiO3. The hybrid inks developed in this work are therefore suitable for robocasting of BaTiO3-based electroceramics.

Effects of NiO addition on structure and dielectric properties of BaTiO3-based ceramics

The phase structure, microstructure, ferroelectric and dielectric properties of NiO-modified BaTiO3-4.0 mol%Nb2O5 ceramics (BT-Nb-Ni) were systematically investigated. All the specimens revealed cubic perovskite structure along with Ba3Nb3.2Ti5O21 second phase by XRD analysis. Small amount of NiO addition (x ≤ 0.5) had the effect of inhibiting grain growth, while a further increase of NiO content (x ≥ 1.0) led to relatively large grains with an average grain size of ~ 0.40 μm. From P-E hysteresis loops and modified Curie–Weiss fitting, NiO addition first reduced and then enhanced the relaxor behaviour of the system. The er-T curves of BT-Nb-Ni ceramics were significantly flattened, leading to greatly optimized dielectric temperature stability. The optimum property was achieved in the composition BT-Nb-2.0%Ni with er = 1380 and △C/C25 °C ≤ ± 15% in the temperature range of − 65–170 °C.

Energy storage performance of BaTiO3-based relaxor ferroelectric ceramics prepared through a two-step process

As the industrial pillar of electronic ceramics, BaTiO3 ceramic is difficult to achieve large energy storing performance due to its high Pr and low dielectric breakdown field strength, making it difficult to satisfy their development requirements of miniaturization and lightweight of power electronic equipment. Therefore, a two-step strategy including adjusting the ratio of chemical elements to modify the microstructures and optimizing the preparation process to enhance electric breakdown strength has been proposed to greatly enhance the energy storing performance of lead-free ferroelectric ceramics, whose effectiveness has been proved within this investigation. Especially, the (Ba0.65Sr0.245Bi0.07)0.99Nd0.01TiO3 (BT-SBT-NdVPP) ceramic prepared by this strategy obtains a superhigh energy storage density of 4.2 J/cm3 under 460 kV/cm, and its temperature (30 ~ 100 °C) and frequency (10 ~ 400 Hz) stabilities under 300 kV/cm are pretty good. In addition, this ceramic has excellent pulse performance under 350 kV/cm between 30 and 150 °C. Therefore, this two-step strategy put forward within this investigation not only significantly improves the energy storage performance of BT-based ceramics but also provides a reference for the preparation of dielectric ceramics with high quality, which could has great potential for the practical industrial application.