The dielectric properties of complex titanate perovskites are highly sensitive to the composition, which influences the stability of the ferroelectric state. This work examines the role of Zr4+ and (Mg1/3Nb2/3)4+ doping on the B-site in a high entropy composition based on (Na0.2Bi0.2Ba0.2Ca0.2Sr0.2)TiO3. In particular, (Na0.2Bi0.2Ba0.2Ca0.2Sr0.2)(Ti1-xMex)O3 (Me = Zr4+, (Mg1/3Nb2/3)4+, x = 0.00-0.15) ceramics are synthesized by solid-state reaction method. All ceramics form a single-phase cubic structure as demonstrated by X-ray diffraction. The difference in ionic radius between Zr4+ and (Mg1/3Nb2/3)4+ ions contributes to changes in lattice parameter and microstructure. The Zr4+ doping generally causes lattice expansion, whereas low concentrations of (Mg1/3Nb2/3)4+ doping lead to lattice contraction, resulting in distinct microstructural modifications. For the doped samples, the relative permittivity decreases due to the influence of the dopants when compared with the undoped sample. Furthermore, the dielectric loss decreases substantially to a value below 0.001 across a broad temperature range and the temperature stability of capacitance is enhanced at elevated temperatures. Furthermore, all ceramics with higher Zr4+ and (Mg1/3Nb2/3)4+ concentrations show linear dielectric behavior with evidence of significant change of electrical characteristics revealed by impedance and modulus analysis. Consequently, the addition of Zr4+ and (Mg1/3Nb2/3)4+ to the composition (Na0.2Bi0.2Ba0.2Ca0.2Sr0.2)TiO3 shows great promise for high temperature, temperature stable capacitor applications.

Different outcomes have been presented on the preparation of high‐temperature ceramic AnB2O2n+5 (A = Hf, Zr and B = Nb, Ta). Considering the importance of these materials as refractories, the stability range of the A = Hf and B = Nb compound is experimentally determined by preparing ceramics via solid‐state synthesis and analyzing their phase compositions. Then, the density functional theory was used to study the stability of the homologous series versus decomposition to the parent compounds of HfO2 and Nb2O5. A good agreement with the experimental values is found. In order to improve the theoretical data further, an interatomic potential based on the first‐principle calculations is developed and applied to larger supercell structures. These force‐field calculations confirm the stability of the homologous series versus a solid solution. The calculations also allow us to study cation order and periodic compositional modulation.

Different combinations of monovalent and trivalent A-cations in high-entropy perovskite oxides (HEPOs) were investigated. The multicomponent (A′0.2A″0.2Ba0.2Sr0.2Ca0.2)TiO3 (A′ = Na+, K+, A″ = Bi3+, La3+) perovskite compounds were successfully synthesized by solid-state reaction method persisting average cubic perovskite phase. The trivalent cation exhibited distinct effects on local structure, dielectric properties and relaxor ferroelectric behavior. Highly dense ceramics (> 95%), high dielectric constant (~ 3000), low dielectric loss (~ 0.1), and relaxor ferroelectric characteristics were obtained in the compound containing Bi3+. The La3+ containing compounds revealed lower dielectric constant, higher dielectric loss and linear dielectric behavior. The effect of monovalent cation on the dielectric properties was minimal. However, it affected relaxor ferroelectric behavior at elevated temperatures and conduction behavior at high temperatures. The (K0.2Bi0.2Ba0.2Sr0.2Ca0.2)TiO3 ceramic maintained the relaxor ferroelectric behavior with low PREM at high temperatures suggesting more stable relaxor ferroelectric characteristics than that of the (Na0.2Bi0.2Ba0.2Sr0.2Ca0.2)TiO3. Moreover, between these two compounds, the homogeneous electrical characteristics could be obtained from the compound consisting of K + and Bi + at A-site. This study suggests that tuning the chemical composition, particularly choosing appropriate combination of mono/trivalent cations in high entropy perovskite oxides, could be the effective approach to develop high-performance relaxor ferroelectrics with the desired properties.

The introduction to that first volume included a dedication from the Royal Society addressed to their patron, the king.They had hoped that their "undertakings to extend the knowledge of nature…" had "contributed, so eminently, to the progress of Science and of Taste in Europe."From these humble beginnings to today, peer-reviewed articles have been held up as the gold standard of publishing-serving as a de facto vehicle for disseminating invaluable, indisputable, verifiable scientific findings.Today, from my perspective as a scientific editor and researcher, journal articles have taken on an even higher profile.In the midst of emerging crises (e.g., disease, climate, artificial intelligence, weapons of mass destruction, natural disasters), government policy makers, journalists, business owners, and almost everyone else are looking to journal articles to help illuminate all sides of an issue.The public has fundamental questions about the crisis, including understanding its cause, the impact of the crisis on their daily life, predictions about the future course of events, and many,

Tellurium oxides of the ATeO3 form typically do not crystallize in perovskite structures. Here, we show that perovskite-like ATeO3 (A = Ca, Sr, Ba) thin films can be grown on perovskite single-crystal substrates via epitaxial stabilization. These films are stable with high optical bandgaps, low dielectric losses, and a high electric breakdown strength. Hysteretic dielectric behavior found in SrTeO3 and BaTeO3 strongly suggests the presence of antiferroelectricity and ferroelectricity, respectively. These properties make perovskite tellurium oxides possibly appealing candidates for thin film coating or insulator materials in advanced microelectronics. Tellurium oxides constitute a largely unexplored class of materials that might show new and interesting functionalities in epitaxial thin-films. Our work encourages new work within this field.

High quality data on the high temperature electrical properties of ceramics, particularly oxides, is of great value for material selection, design, and modeling for a broad range of emerging applications. Utilizing the mismatch in the coefficient of thermal expansion between two materials, a purely mechanical method for establishing electrical contact in the van der Pauw geometry to measure the bulk resistivity of ceramic disks at high temperatures is presented. Measurements of a reference material, 20 mol. % Gd-doped cerium oxide, are presented up to 1000 °C. The viability of electrical measurements up to a maximum temperature of 1600 °C is also considered. Measurements are performed using multiple techniques and compared to literature values finding excellent agreement. The approach described in this work enables the van der Pauw method to be applied to many ceramic materials over a wide range of temperatures and environments.

Abstract Sodium niobate (NaNbO3)-based antiferroelectric (AFE) ceramics have received significant attention for energy storage applications because of their good performance, low cost, and nontoxicity. However, the existence of the antiferroelectric P phase at room temperature causes large hysteresis, resulting in reduced energy storage efficiency. In this study, 0.88NaNbO3–0.12Sr0.7Bi0.2TiO3 ceramics doped with Nd3+ (i.e., 0.88Na1-3 x Nd x NbO3-0.12Sr0.7Bi0.2TiO3) at x = 0.0 − 0.025 were prepared via conventional solid-state mixed oxide route. The XRD data showed that all samples exhibited an orthorhombic structure. With increasing Nd3+ doping content, the antiferroelectric P (Pbma) phase to R (Pnma) phase transition temperature (T P-R) shifted to lower temperatures. Consistent with the dielectric properties, a transition to a relaxor-like slim P-E loop indicative of an AFE R phase was observed at the composition x ≥ 0.01. This led to an increase in both the recoverable energy-storage density (W rec) and efficiency (η) with an increasing amount of Nd3+ doping level. The maximum recoverable energy storage density (W rec = 0.54 J/cm3) and high energy storage efficiency (η = 93%) were observed at x = 0.025 under an applied electric field of 100 kV/cm. In addition, the optimum composition at x = 0.025 also exhibited excellent temperature stability from 25 °C to 150 °C. This research demonstrates that the NN–SBT–xNd system has the potential for use for high-energy-density pulsed power capacitor applications.

Here we demonstrate a theory-driven, novel dual-shell coating system of Li2SrSiO4 and Al2O3, achieved via a facile and scalable sol-gel technique on LiCoO2 electrode particles. The optimal thickness of each coating can lead to increased specific capacity (∼185 mAh/g at 0.5C-rate) at a cut-off potential of 4.5 V, and greater cycling stability at very high C rates (up to 10C) in half-cells with lithium metal. The mechanism of this superior performance was investigated using a combination of X-ray and electron characterization methods. It shows that the results of this investigation can inform future studies to identify still better dual-shell coating schemes, achieved by such industrially feasible techniques, for application on similar, nickel-rich cathode materials.

At its core, materials science is the study of the structure and properties of the materials we use. Understanding the relationship between the structure and properties is central to the discipline of materials science. In one way or another, it is weaved into almost every academic course in materials science, and I introduce the concept in the very first lecture of my Introduction to Materials Science course. Outside the classroom, these relationships are used to synthesize the materials we use every day, to understand why they sometimes unexpectedly fail in operation, and most all we use those relationships to develop brand-new materials that bring advanced technologies to life. Structure–property relationships are ubiquitous across all material classes. In polymers, changing the structure of the side groups can result in dramatic changes in properties (e.g., polyethylene to polyvinylchloride). In ceramics, small changes in structure can have a significant impact on properties. For example, subtle changes in the symmetry of the perovskite structure underpin the piezoelectric effect. Similar examples could be made for semiconductors, composites, biological materials, and other classes of materials. However, of all material classes, structure– property relationships are most apparent in metallic materials. I, myself, am a ceramic scientist, but my academic training in materials science started by learning the fundamental structure–property relationships in metals. Thus, there is no better way to understand, on a deeply fundamental level, the intricate linkages between the properties of the materials we observe (hardness, elastic modulus, density, plasticity, and fracture) and the chemical and

High-performance ceramics with chemical formula (Ni1/3Ta2/3)(x)Ti1- xO2 with excellent dielectric properties are demonstrated. The dopants of Ni2+ and Ta5+ in TiO2 caused the formation of oxygen vacancies and free electrons. The (Ni1/3Ta2/3)(x)Ti1-xO2 exhibited low loss tangent of 0.046 and a high dielectric permittivity of 3.5-4.5 x 10(4) with a very weak dependence on temperature (-60 to 200 ?). Broadband dielectric spectroscopy shows at least four dominant sources in the dielectric relaxation response in the temperature range of - 253-210 ?. DFT calculations indicate the formation of defect clusters, which are the largest contributors to the dielectric response, and these are found to be dominant even at temperatures down to - 253 ?. Both grain boundary and surface layer mechanisms in the ceramics contribute to the dielectric response at the relatively high temperatures. The sample-electrode contact effect associated with oxygen vacancy diffusion is dominant at high temperatures above 150 ?.

Corrosion by alkali metals and their compounds poses a significant challenge to the long-term material stability and service life for both metal alloys and ceramics at high operating temperatures. Chemical reactivity between alkali metals and materials underlie numerous industry challenges ranging from fireside corrosion in biomass-fired boilers to reaction with silica-based refractory ceramics in glass furnaces. The problem is particularly significant in magnetohydrodynamic (MHD) generators, where potassium or cesium compounds are introduced to improve the electrical conductivity of the working fluid. Thus, resistance to attack by alkali metal vapor is an important consideration in the selection and fabrication of ceramic electrodes and insulators for MHD generators. We evaluated several refractory ceramics to assess phase stability and known reactions with potassium and its compounds at high temperatures (T >1,200 degrees C). Refractory ceramics were tested for potassium vapor corrosion using a modified ASTM standard test method with in situ monitoring of gas composition. Unlike other materials, the magnesia (MgO) and ceria (CeO2) samples did not exhibit corrosion, and no phase or mass changes were observed. This indicates that CeO2 and MgO could exhibit long lifetimes as plasma facing components in MHD generators. Ultimately, this development provides valuable data in evaluating critical materials performance issues that can attest to the viability of high temperature direct fired MHD generator applications.

The solid solution (1 - x)[Bi-1/2(Na1/2K1/2)(1/2)TiO3]-xPbZrO(3), (0.00 <= x <= 0.12) was investigated to examine the phase equilibria, dielectric and electromechanical properties. The composition corresponding to x = 0.00 exhibits tetragonal symmetry with the expected classical ferroelectric (FE) behavior. The system exhibited FE to relaxor crossover with the addition of lead zirconate at the composition x = 0.05. This is indicated by typical relaxor characteristics such as a transition to the global pseudocubic phase, a constriction in the FE hysteresis loop, and a sudden decrease in the negative strain accompanied by an increase in maximum strain. Most notably, with a further increase in x (>0.05), there is evidence for a return to a FE phase that exhibits classical FE characteristics. The combined results demonstrate that there exists a narrow FE-relaxor boundary near x = 0.05, where FE and relaxor phases coexist. At the critical composition, enhancement in the piezoelectric properties, including an increase in the effective d33* (350 pm/V) was observed. This transition in the electromechanical properties is consistent with changes observed in the phase equilibria for this solid solution. The crystal structure transitions from tetragonal symmetry for x = 0.00, to pseudocubic symmetry for the relaxor compositions (x = 0.05), and finally to a lower symmetry perovskite phase for the re-entrant FE phase (x> 0.05). This composition-induced transition from FE to relaxor to a re-entrant FE state in the (1 - x)[Bi-1/2(Na1/2K1/2)(1/2)TiO3]-xPbZrO(3) system is unusual among relaxor FE systems and thus is of great scientific and technological interest.

The effects of sintering time on the ferroelectric to relaxor crossover were systematically investigated for Sr(Hf0.5Zr0.5)O3-modified Bi0.5(Na0.8K0.2)TiO3 ceramics, prepared using the conventional solid-state mixed-oxide route. Scanning electron microscopy indicated a modest increase in grain size from 1.0 ± 0.2 to 2.0 ± 0.5 μm when the sintering time increased from 2 to 24 h. Furthermore, it was observed that the sintering time does not affect the long-range average crystal structure, as x-ray diffraction data suggest the presence of a single pseudocubic phase for all the samples, irrespective of the sintering time. Interestingly, ferroelectric and piezoelectric characterization showed evidence of a ferroelectric to relaxor transition when the sintering time increased from 2 to 6 h. This transition was marked by a sudden decrease in remanent polarization, a loss in negative strain along with a drastic increase in the maximum electromechanical strain. This was further exemplified in the unipolar strain data, which showed a transition from linear to non-linear dependence with electric field when the sintering time increased from 2 to 6 h. The piezoelectric properties were enhanced with further increase in sintering time up to 12 h, with the corresponding normalized strain value (Smax/Emax) d33∗=647pm/V. However, the d33∗ decreased with further increase in sintering time to 24 h. As the sintering time increased, temperature-dependent dielectric data show a decrease in the maximum permittivity along with the slight shift of the Tmax (temperature of maximum permittivity) to a higher temperature. In addition, results from impedance spectroscopy indicate that the DC resistivity increased by approximately two orders of magnitude when the sintering time increased from 2 to 12 h. These results suggest that while sintering time has a minimal impact on either the microstructure or the long-range average structure, it has a strong influence on the ferroelectric to relaxor crossover, which is often associated with enhanced electromechanical properties. This work presents further evidence that the crossover phenomenon is closely tied to the local structure, where disruption of the long-range dipole order results in stabilization of the relaxor state.

Phase pure perovskite (1-x)Bi 1/2 Na 1/2 TiO 3 – xBi 1/2 K 1/2 TiO 3 (BNKT) thin films were successfully prepared via an inverse mixing order chemical solution deposition method and the impact of process conditions on film properties were observed. Process conditions evaluated included crystallization temperature and time, ramp rate, pyrolysis temperature, and cation excess. Properties measured included crystal structure, dielectric constant, dielectric loss, piezoelectric response, and ferroelectric response. A few notable trends were observed. A subtle impact on piezoelectric response was observed in films prepared using different ramp rates: 100 C per second films (d 33,f = 60 ± 5 pm/V at 1 kHz), 75 °C per second films (d 33,f = 55 ± 5 pm/V) and 150 C per second films (d 33,f = 50 ± 5 pm/V). Films prepared using a 75 °C per second ramp rate displayed slightly higher dielectric loss (tan δ = 0.09 at 1 kHz) than films prepared using a 100 °C per second ramp rate (tan δ = 0.07 at 1 kHz) or 150 °C per second ramp rate (tan δ = 0.05 at 1 kHz). Pyrolysis temperatures greater than 350 °C are necessary to burn off organics and maximize film dielectric constant. Dielectric constant increased from 450 ± 50 at 1 kHz to 600 ± 50 at 1 kHz by increasing pyrolysis temperature from 300 to 400 °C. Excess cation amounts (for compositional control) were also evaluated and it was found films with higher amounts of Na and K excess compared to bismuth excess displayed an increase in d 33,f of about 10 pm/V compared to films prepared with equivalent Bi and Na and K excess amounts. Article highlights Impact of processing conditions on inverse mixing order chemical solution deposited bismuth based thin films. Dielectric, piezoelectric, and ferroelectric properties of thin film bismuth sodium titanate-bismuth potassium titanate thin films. Developing lead-free piezoelectric actuator materials.

This study focused on the synthesis and electrical property measurements of the lead zirconate titanate (PZT)-bismuth indate (BI) perovskite solid solution system. As the PZT binary system is a very well-developed and integrated materials system, identifying new ternary systems based on PZT would allow for a new dimension of control into the exploration and improvement of its electrical properties, which could enable enhancements in the performance of current technology and devices. Here, the solid solution of BiInO3-PbZrO3-PbTiO3 (xBI-(1-x) PZT 52/48) was explored. Through calcination studies, stable solid solutions were obtained, and compositions up to a maximum of 15-mol% BI were synthesized. With increasing BI content, the symmetry transitioned from a tetragonal P4mm phase toward a rhombohedral R3m phase. The Curie temperature of these samples decreased with increasing mol% BI from similar to 390 degrees C in pure PZT 52/48 to 322 degrees C in 10% BI. Ferroelectric and piezoelectric studies of the 2.5% BI sample showed a coercive field of 14.4 kV/cm, P-max = 38 mu C/cm(2), P-r = 29 mu C/cm(2), and a d(33)* = 280 pC/N under a maximum applied field of 70 kV/cm at 1 Hz.

Effect of Na non-stoichiometry in Sr(Hf 0.5 Zr 0.5 )O 3 -modified Bi 0.5 (Na (0.8+x) K 0.2 ) 0.5 TiO 3 ceramics was examined in the range of − 0.04 ≤ x ≤ 0.04. The effect of Na non-stoichiometry on microstructure, ferroelectric, piezoelectric, dielectric properties and high-temperature impedance was explored. Compared to the stoichiometric compositions, Na excess and deficiency exhibit the same effect as observed for the acceptor and donor doping, respectively. All non-stoichiometric and stoichiometric compositions exhibit a pure ABO 3 perovskite phase with pseudocubic symmetry. The deficiency of Na in ceramics decreases the grain size and drives the system towards ergodic relaxor as evident by pinched ferroelectric loop and the negligible negative strain along with an increase in maximum strain (S m ). The corresponding normalized strain (S m /E max. ) increased from 275 to 800 pm/V when Na content decreased from x = + 0.04 to − 0.04. In contrast, excess Na exhibits the converse effect and drives the system towards ferroelectricity. Composition with deficient Na also exhibits lower dielectric loss and increase in resistivity by an order of magnitude compared to excess Na as observed from the high-temperature dielectric and impedance measurements. The results of this study demonstrate that Na non-stoichiometry significantly affects the electric properties of the studied system and thus can be effectively modulated to achieve improved electromechanical properties for materials having actuator-based applications.

Effect of Na non-stoichiometry in Sr(Hf0.5Zr0.5)O3-modified Bi0.5(Na(0.8+x)K0.2)0.5TiO3 ceramics was examined in the range of − 0.04 ≤ x ≤ 0.04. The effect of Na non-stoichiometry on microstructure, ferroelectric, piezoelectric, dielectric properties and high-temperature impedance was explored. Compared to the stoichiometric compositions, Na excess and deficiency exhibit the same effect as observed for the acceptor and donor doping, respectively. All non-stoichiometric and stoichiometric compositions exhibit a pure ABO3 perovskite phase with pseudocubic symmetry. The deficiency of Na in ceramics decreases the grain size and drives the system towards ergodic relaxor as evident by pinched ferroelectric loop and the negligible negative strain along with an increase in maximum strain (Sm). The corresponding normalized strain (Sm/Emax.) increased from 275 to 800 pm/V when Na content decreased from x =  + 0.04 to − 0.04. In contrast, excess Na exhibits the converse effect and drives the system towards ferroelectricity. Composition with deficient Na also exhibits lower dielectric loss and increase in resistivity by an order of magnitude compared to excess Na as observed from the high-temperature dielectric and impedance measurements. The results of this study demonstrate that Na non-stoichiometry significantly affects the electric properties of the studied system and thus can be effectively modulated to achieve improved electromechanical properties for materials having actuator-based applications.