Complex Perovskite Solid Solutions 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.

Wrapping Assembly of BaTiO3 Nanoparticles with (Bi0.5Na0.5)TiO3 Nanosheets: A Novel Processing for Nanograined BT–BNT Complex Perovskite Relaxors

Hydrothermal syntheses of BaTiO3 (BT) nanoparticles and (Bi0.5Na0.5)TiO3 (BNT) nanosheets are explored to maximize the uniform distributions of the components in BT–BNT complex perovskite solid solution preparation. By introducing a “wrapping process,” which is a 2D nanosheet‐based process for preparing core–shell‐type assembly of the BT and BNT powder mixture, the solid solution formation and densification are accelerated effectively resulting in lowering the sintering temperature and homogeneous nanograined microstructure. The improved microstructure of the BT–BNT solid solution ceramics contributes to the enhancement in dielectric polarizations over a wide temperature range. Relaxor characteristics of the solid solutions, i.e., diffusivity of the ferroelectric–paraelectric transition, frequency dispersion of ε r′, and shift of T m with frequency deviation from the Curie–Weiss law, are determined. It is also confirmed that the BT–BNT samples prepared by the wrapping process exhibit stronger relaxor behavior compared to the conventionally prepared BT–BNT samples even in the identical chemical composition. These hydrothermal reaction‐based novel processing routes for the complex perovskite compositions are very effective to improve microstructure, sinterability, and dielectric properties.

Growth, Structure, and characterization of new High-TC Piezo-/Ferroelectric Bi(Zn2/3Ta1/3)O3-PbTiO3 single crystals

In this work, new bismuth-based complex perovskite piezo-/ferroelectric single crystals of the (1-x)PbTiO3-xBi(Zn2/3Ta1/3)O3 solid solution have been successfully grown by the high temperature solution method (HTSG). The crystal structure was found to be tetragonal at room temperature by means of structural analysis by X-ray diffraction and domain examination by polarized light microscopy (PLM). High Curie temperature (TC = 470 °C) was determined by dielectric measurements and PLM observations. Band-like domain structures were observed in the (001)-oriented single crystal with a width of 100–200 µm. Good piezoelectric performance (d33 = 251 pC/N) and high coercive field (EC = 30 kV/cm) were found by the piezoelectric and ferroelectric characterizations. Detailed crystal structural refinement was performed to establish the structure–property relationship in this system. Comparative studies of current bismuth-based complex perovskite solid solution single crystals point to the advantages of the Bi(Zn2/3Ta1/3)O3-PbTiO3 single crystals in terms of high TC, good piezoelectric performance, and high coercive field. These advantages make this piezo-crystal system a favourable candidate for potential high-temperature and high-power electromechanical applications.

Dielectric and piezoelectric properties of lead-free Na0.5Bi0.5TiO3-SrTiO3-BiFeO3 ternary system

This work focuses on the synthesis and characterization of a Pb-free (0.8-x)Na0.5Bi0.5TiO3-0.2SrTiO3-xBiFeO3, 0.00 ≤ x ≤ 0.10 perovskite. The ceramics exhibit significant improvement in some of the key parameters like Tc, dielectric constant, temperature stability, TCε values, etc. XRD patterns suggest 100% perovskite structure (Pseudocubic phase) without any trace of secondary phases. The temperature-dependent dielectric constant of doped ceramics exhibits peculiar response particularly at lower frequencies with εr increasing drastically to extraordinarily large values (˃ 50,000 at 1 kHz, and ˃ 12,000 at 10 kHz). Such an abnormal behavior probably arises due to the interfacial polarization caused by the formation of defect dipoles. Further, successive dielectric anomalies appeared around 200–250 °C and 350–450 °C in the BFO doped samples giving rise to temperature-insensitive dielectric constant over a broad temperature span. The composition (x = 0.05) showed a permittivity of ~4000 at 100 kHz at 250 °C with a normalized permittivity Δε/ε250 varying not more than± 15% from 200 °C to beyond 500 °C. In addition, the same composition yields a TCε value as low as −194 ppm/°C which is promising from the application point of view. Analysis of P-E, J-E and S-E loops predict a probable destabilization of the ferroelectric phase by introduction of relaxor state with the incorporation of BFO in the complex perovskite solid solution. Based on the current results, the NBT-ST-BFO ceramics can be designed to minimize loss via compositional engineering for high-temperature capacitor applications.

Effects of antiferroelectric substitution on the structure and ferroelectric properties of a complex perovskite solid solution

Novel ferro-/piezoelectric solid solutions between bismuth-based perovskite and antiferroelectric material are designed and synthesized and their crystal structure, phase transitions, ferro-/piezoelectric properties and local polar structure are investigated.

Synthesis, structure, and dielectric properties of a new binary antiferroelectric solid solution: (1−x)Pb(Mg1/2W1/2)O3–xPbHfO3

AbstractDielectric ceramics are one of the most important electrical insulators because of their excellent electrical stability and nonconducting properties. In this work, new complex perovskite solid solutions, (1−x)Pb(Mg1/2W1/2)O3–xPbHfO3 [(1−x) PMW–xPHf] (0.00 ≤ x ≤ 0.04), were successfully synthesized in the form of ceramics by the solid‐state reaction method and sintering process. The X‐ray diffraction results indicate that a single perovskite phase with antiferroelectric (AFE) orthorhombic Pmcn symmetry is formed for x < 0.04 which corresponds to the PMW‐type solid solution (SS‐PMW). For the composition x = 0.04, however, a small amount (about 1%) of ferroelectric orthorhombic C2mm phase that arises from the PHf‐type solid solution (SS‐PHf) was found to coexist with the Pmcn phase (99%). The dielectric measurements show that the AFE‐paraelectric phase transition temperature TC of the (1−x)PMW–xPHf ceramics increases from 38.2°C (x = 0) to 40.1°C (x = 0.03) with the increasing PHf content, indicating a slightly enhanced AFE ordering degree. The studied materials show a relatively low dielectric constant (~102), a low dielectric loss (~10−2), a high breakdown field strength (~140 kV/cm), and a linear electric field dependence of polarization at room temperature, which make them a new candidate for potential applications as ceramic insulators.

Complex morphotropic phase transformations and high piezoelectric properties in new ternary perovskite single crystals

In order to understand the complex phase symmetry and phase transitions, and to illustrate the microscopic mechanisms of high piezoelectricity, single crystals of a new ternary complex perovskite system, Pb(Mg1/3Nb2/3)O3-Bi(Zn2/3Nb1/3)O3-PbTiO3, are grown by the high temperature solution growth method and their domain structure, dielectric and ferro-/piezoelectric properties, and phase transformation behavior are investigated by various techniques. Different phase symmetries including the rhombohedral, tetragonal and monoclinic are found in these crystals, indicating that the composition of the crystals is close to the morphotropic phase boundary (MPB) region. Most interestingly, unusual phase transformation sequences of rhombohedral → monoclinic → cubic, and monoclinic → cubic are directly observed by polarized light microscopy and confirmed by the dielectric and birefringence results. Moreover, an ultrahigh piezoelectric coefficient d33 ≈ 2000 pC/N is obtained in these crystals, making these crystals useful for applications as electromechanical transducers. The unusual phase transformation sequences and the high piezoelectric response are explained from the polarization rotation mechanism, which has been evidenced in this work. Based on these results, a temperature-composition phase diagram is established, which illustrates the complex phases present and their transformation behavior. These studies provide new insights into the intricate morphotropic phase symmetry and phase components in complex perovskite solid solutions, and a better understanding of the microscopic mechanisms of high piezoelectric response in relaxor-based piezocrystals, which in turn will be helpful for designing better piezoelectric single crystals.

High Curie-temperature (TC) piezo-/ferroelectric single crystals with bismuth-based complex perovskites: Growth, structures and properties

Complex perovskite solid solutions based on Bi(B′B″)O3-PbTiO3 are potentially interesting ferroelectric and piezoelectric materials with high Curie temperature (TC). In this work, large-size (1-x)Bi(Zn1/2Ti1/2)O3-xPbTiO3 (BZT-PT), and (1-x)Bi(Zn2/3Nb1/3)O3-xPbTiO3 (BZN-PT) single crystals have been successfully grown by the high-temperature solution growth method and the top-cooled solution growth method. A comparative study of the (001)-oriented BZT-PT and BZN-PT crystals is carried out and significant differences are found in their structures and physical properties which are characterized by various techniques. The crystal structures of both crystals are refined to be of tetragonal symmetry by means of powder X-ray diffraction, but their local structures exhibit remarkable differences in terms of cationic displacements. The TC is determined to be around 572 °C and 424 °C for the BZT-PT and BZN-PT single crystals, respectively. The ferroic domain structures examined by polarized light microscopy based on optical crystallography are found to be different in the BZT-PT and BZN-PT crystals. The effects of domain structures on the different ferroelectric behaviors are investigated. The high TC and large coercive electric field, as well as the high remanent polarization of the BZT-PT and BZN-PT single crystals make them promising candidates for applications in high-power electromechanical transducers that can be operated in a wide temperature range.

Combined theoretical and nanoscale experimental study of Pb(Ca,Ba)TiO3, Pb(Sr,Ba)TiO3, and Pb(Sr,Ca)TiO3 complex perovskite structures: An investigation of the ferroelectric and electronic properties

Combined experimental and first-principles studies have been conducted to obtain a fundamental understanding of the effect of A-site chemical doping on the electronic structure and ferroelectric behavior of Pb(Ca,Ba)TiO3, Pb(Sr,Ba)TiO3, and Pb(Sr,Ca)TiO3 perovskite complex solid solutions. Rietveld refinement of powder X-ray diffraction data shows that the crystal structure of all the three compounds is distorted from the ideal cubic perovskite structure. At the nanoscale, piezoresponse force microscopy (PFM) studies show low-performance ferroelectric properties of Pb(Sr,Ca)TiO3 thin films when compared to Pb(Ca,Ba)TiO3 and Pb(Sr,Ba)TiO3 films. Theoretical analysis of the electronic band structure performed on the basis of density functional theory (DFT) allows to elucidate the origin of the different ferroelectric behaviors observed in Pb(Ca,Ba)TiO3, Pb(Sr,Ba)TiO3, and Pb(Sr,Ca)TiO3 thin films. DFT-based computational calculations reveal that there is a strong correlation between the effects of Ti 3d non-bonding orbitals (responsible for π TiO bonding) and the ferroelectric polarization behavior of A(A′A″)BO3 complex perovskite solid solutions. In our study, very low Ti 3dxy, dxz, and dyz non-bonding electronic density state contributions were observed and the presence of mainly ionic CaO and SrO bonds. These effects are the reason for the unusually weak polarization, low tetragonality, and poor ferroelectricity of Pb(Sr,Ca)TiO3 thin films. This is in contrast to the observed behaviors of Pb(Ca,Ba)TiO3 and Pb(Sr,Ba)TiO3 thin films. However, our first-principles calculations agree well with the PFM-based experimental results obtained in the nanometer scale.

Synthesis, structure and piezo-/ferroelectric properties of a novel bismuth-containing ternary complex perovskite solid solution

A novel ternary solid solution has been synthesized by solid state reaction in the form of ceramics with compositions across the morphotropic phase boundary (MPB). It exhibits high-performance piezo-/ferroelectric properties whose underlying physical and chemical mechanisms are investigated.

Growth and properties of (1−x)Pb(Zn1/3Nb2/3)O3–xPbTiO3 (x=0.07–0.11) ferroelectric single crystals by a top-seeded solution growth method

The relaxor-based single crystals of complex perovskite solid solutions, Pb(Mg1/3Nb2/3)O3–PbTiO3 [PMN–PT] and Pb(Zn1/3Nb2/3)O3–PbTiO3 [PZN–PT], exhibit extraordinary piezoelectric performance: displaying extremely high piezoelectric coefficients, very large electromechanical coupling factors, and exceptionally high strain. These materials outperform the currently used Pb(Zr1−xTix)O3 [PZT] ceramics, making them the materials of choice for the next generation of electromechanical transducers for a broad range of advanced applications. In this article, the PZN–xPT (x=0.07–0.11) single crystals near the morphotropic phase boundary were prepared using the top-seeded solution growth technique. Ferro-/dielectric and piezoelectric properties, crystal chemistry, domain structure, and electromechanical coupling properties were systematically characterized. It is showed that the top-seeded solution growth method is an effective alternative technique for preparing the high quality PZN–xPT ferroelectric crystals, which is effective in controlling nucleation/growth of the PZN–xPT single crystals and suppressing the undesired Pb deficient pyrochlore phase by providing a Pb rich environment.

Crystal Structure and electrical properties of complex perovskite solid solutions based on (1-x) NaNbO3-xBi (Zn0.5Ti0.5) O3

Ceramics based on the perovskite solid solution (1-x) NaNbO3-xBi (Zn0.5Ti0.5) O3 were prepared using conventional solid state synthesis. The crystal structure, electrical, and optical properties were examined. According to diffraction data, a single perovskite phase could be identified up to the composition x = 0.09. As the Bi (Zn0.5Ti0.5) O3 content increased the crystal structure transitioned from orthorhombic to pseudocubic symmetry. Furthermore, dielectric data showed that the dielectric maximum shifted to lower temperatures with the addition of Bi (Zn0.5Ti0.5) O3. Polarization hysteresis data revealed a slim linear loop across the whole range of solid solutions. Optical data also showed a decrease in the optical band gap from 3.4 eV for pure NaNbO3 to 2.9 eV for the x = 0.09 composition. Using impedance spectroscopy, an electrically inhomogeneous microstructure was observed for compositions with increased Bi (Zn0.5Ti0.5) O3 content. Finally, the substitution of Ta on the B-site was shown to shift the dielectric maximum to temperatures as low as 100 K.

Softening of antiferroelectricity in PbZrO3-Pb(Mn1/2W1/2)O3 complex perovskite solid solution

A new solid solution of complex perovksite structure, (1-x)PbZrO3-xPb(Mn1/2W1/2)O3 (PZ-xPMnW, with x = 0–0.1), is prepared by solid state reaction method. Its crystal structure, dielectric properties, and antiferroelectricity are investigated. It is found that the crystal structure of the solid solution remains in the orthorhombic Pbam symmetry with x ≤ 0.1. The induced ferroelectric polarization (PInd) is enhanced, whereas the critical field (ECr) is decreased, with increasing PMnW concentration, indicating the softening of antiferroelectricity in PZ. The Curie temperature (TC) is also decreased with the substitution of PMnW for PZ. The grain size is significantly enlarged, which could be attributed to the presence of a transient liquid phase during the sintering process. Measurements of the magnetization by means of SQUID confirm that the Mn ion exists in a high spin state with a 2+ oxidation state. The softening of antiferroelectric order and the improvement in induced polarization make the PZ-PMnW ceramics an interesting material system for such applications as energy storage devices.

Band gap engineering strategy via polarization rotation in perovskite ferroelectrics

We propose a strategy to engineer the band gaps of perovskite oxide ferroelectrics, supported by first principles calculations. We find that the band gaps of perovskites can be substantially reduced by as much as 1.2 eV through local rhombohedral-to-tetragonal structural transition. Furthermore, the strong polarization of the rhombohedral perovskite is largely preserved by its tetragonal counterpart. The B-cation off-center displacements and the resulting enhancement of the antibonding character in the conduction band give rise to the wider band gaps of the rhombohedral perovskites. The correlation between the structure, polarization orientation, and electronic structure lays a good foundation for understanding the physics of more complex perovskite solid solutions and provides a route for the design of photovoltaic perovskite ferroelectrics.

Radiation defects in complex perovskite solid solutions

First principles density functional theory (DFT) based modeling is performed to explore formation energies of a series of point cation and oxygen defects, Frenkel and Schottky disorder, as well as structural disorder in Ba1−xSrxCo1−yFeyO3−δ (BSCF) perovskite solid solutions. The results are compared with previous studies on a prototype SrTiO3 perovskite. It is shown that BSCF permits accommodation of a high concentration of defects and cation clusters but not antisite defects.

Effects of Mg Substitution on Order/disorder Transition, Microstructure, and Microwave Dielectric Characteristics of Ba((Co0.6Zn0.4)1/3Nb2/3)O3 Complex Perovskite Ceramics

Effects of Mg substitution on order/disorder transition, microstructure, and microwave dielectric characteristics of Ba((Co0.6Zn0.4)1/3Nb2/3)O3 complex perovskite ceramics have been investigated. The ordered complex perovskite solid solutions are obtained in Ba((Co0.6−x/2Zn0.4−x/2Mgx)1/3Nb2/3)O3 ceramics (x = 0, 0.1, 0.2, and 0.3), and the ordering degree in the as‐sintered dense ceramics increases with increasing Mg‐substitution amount. The significantly improved Qf value is obtained in the present ceramics with increasing x, whereas the dielectric constant decreases slightly together with some increase of temperature coefficient of resonant frequency. The best combination of microwave dielectric characteristics is obtained in the composition of x = 0.3: εr = 33.7, Qf = 93 800 GHz, and τf = 9.6 ppm/°C. In the Mg‐substituted compositions, clear domain boundaries are obtained and the domain size increases as x increases, the highest Qf value is obtained when the domain size is about 40–60 nm in the ceramics with x = 0.3. The increased ordering degree and the fine ordering domain structure are considered to primarily contribute to the significant increase of Qf value in the Mg‐substituted Ba((Co0.6Zn0.4)1/3Nb2/3)O3 complex perovskite ceramics.

First-principles calculations of 17O nuclear magnetic resonance chemical shielding in Pb(Zr1/2Ti1/2)O3 and Pb(Mg1/3Nb2/3)O3: Linear dependence on transition-metal/oxygen bond lengths

First-principles density functional theory oxygen chemical shift tensors were calculated for A(B,B′)O3 perovskite alloys Pb(Zr1/2Ti1/2)O3 (PZT) and Pb(Mg1/3Nb2/3)O3 (PMN). Quantum chemistry methods for embedded clusters and the gauge including projector augmented waves (GIPAW) method [C. J. Pickard and F. Mauri, Phys. Rev. B 63, 245101 (2001)]10.1103/PhysRevB.63.245101 for periodic boundary conditions were used. Results from both methods are in good agreement for PZT and prototypical perovskites. PMN results were obtained using only GIPAW. Both isotropic δiso and axial δax chemical shifts were found to vary approximately linearly as a function of the nearest-distance transition-metal/oxygen bond length, rs. Using these results, we argue against Ti clustering in PZT, as conjectured from recent 17O NMR magic-angle-spinning measurements. Our findings indicate that 17O NMR measurements, coupled with first-principles calculations, can be an important probe of local structure in complex perovskite solid solutions.

Structural Ordering and Magnetic Property of Complex Perovskite Solid Solution (1-x)Pb(Fe<SUB>2/3</SUB>W<SUB>1/3</SUB>)O<SUB>3</SUB>-xPb(Mg<SUB>1/2</SUB>W<SUB>1/2</SUB>)O<SUB>3</SUB>

以无机盐为前驱体, 利用溶胶?凝胶法固溶合成了(1- x )Pb(Fe 2/3 W 1/3 )O 3 - x Pb(Mg 1/2 W 1/2 )O 3 多铁性固溶体. XRD分析表明, 在0≤ x ≤1.0的掺杂范围内, 700℃煅烧所得产物都具有钙钛矿结构; x =0时得到的纯Pb(Fe 2/3 W 1/3 )O 3 为长程无序结构, x =1.0时可获得完全有序的纯Pb(Mg 1/2 W 1/2 )O 3 相, 其单胞为Pb(Fe 2/3 W 1/3 )O 3 单胞的2倍; 当0 x x )Pb(Fe 2/3 W 1/3 )O 3 - x Pb(Mg 1/2 W 1/2 )O 3 固溶体也为有序结构, 出现1/2 (111)及1/2 (311) XRD衍射峰, 且强度随掺杂系数x的升高逐渐增大. TEM分析证实, 煅烧产物为具有钙钛矿结构的单相固溶体, 而非两相复合物; 固溶相形貌以立方颗粒为主, 随掺杂量增加其晶胞常数线性增大, 而晶粒尺寸先减小后变大. 性能测试发现, 固溶相的磁学性能随x的增加而逐渐下降, 起因于抗磁性的Pb(Mg 1/2 W 1/2 )O 3 破坏了Pb(Fe 2/3 W 1/3 )O 3 原有的价键结构所致.

High-Performance Piezoelectric Single Crystals of Complex Perovskite Solid Solutions

AbstractRelaxor-based single crystals of complex perovskite solid solutions, Pb(Mg1/3Nb2/3)O3–PbTiO3[PMN–PT] and Pb(Zn1/3Nb2/3)O3–PbTiO3[PZN–PT], exhibit extraordinary piezoelectric performance, with extremely high piezoelectric coefficients, very large electromechanical coupling factors, and exceptionally high strain levels. These materials outperform the currently used Pb(Zr1–xTix)O3[PZT] ceramics, making them the materials of choice for the next generation of electromechanical transducers for a broad range of advanced applications. In this article, recent major advances in the development of piezocrystals are reviewed in terms of crystal growth, piezoelectric properties, crystal chemistry, domain structure, and device applications.

Crystal structure of microwave dielectric ceramics Ba[(Mg1−xCdx)0.33Nb0.67]O3

A series of complex perovskite solid solutions of Ba[(Mg1−xCdx)0.33Nb0.67]O3 have been synthesized by the columbite method. Detailed Rietveld refinement of their X-ray diffraction data show that Ba[(Mg1−xCdx)0.33Nb0.67]O3 has an order trigonal structure. The ordering degree as determined by the B-site occupancies increases with the partial substitution of Cd for Mg. However, a decrease in the ordering degree in the Ba(Cd0.33Nb0.67)O3 sample is observed, which can be attributed to a relatively lower synthesis temperature. All the impurity phases are successfully identified by X-ray quantitative phase analysis. Dielectrics properties at low frequencies for all the Ba[(Mg1−xCdx)0.33Nb0.67]O3 compounds have been measured successfully.