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As one of the important electronic components, the dielectric capacitors for energy storage applications have been extensively studied in recent years. Among various dielectric materials, the perovskite oxide Bi0.5Na0.5TiO3‐based ceramics have become promising candidates due to their high polarization, dielectric tunability, environment‐friendly composition, and so forth. Herein, the relaxor ferroelectric ceramics of Bi0.5Na0.5TiO3–SrTiO3–Bi(Mg0.5Zr0.5)O3 were prepared via solid‐state reaction method. The sample with optimal composition not only retains the high polarization by introducing Bi3+ ions, but also achieves the reduced remanent polarization by enhancing relaxor behavior and the promoted electric breakdown strength by the grain size refinement. Accordingly, a high recoverable energy density of 8.3 J/cm3 under 450 kV/cm and the superb charge/discharge properties (current density CD = 1200 A/cm2, power density PD = 150 MW/cm3, charge/discharge time t0.9 = 0.15 µs) are achieved, revealing great prospect in energy storage applications. [ABSTRACT FROM AUTHOR]

Bismuth sodium titanate (Bi0.5Na0.5TiO3)-based relaxor ferroelectric ceramics have received ever-increasing interest for their potential application in dielectric capacitors owing to their sterling energy storage capability. Herein, the perovskite end-member Ba(Fe0.5Nb0.5)O3 (BFN) was incorporated into 0.7Bi0.5Na0.5TiO3-0.3SrTiO3 (0.7BNT-0.3ST) ceramics to improve the relaxor characteristics and refine the grain, leading to slim polarization–electric field (P–E) hysteresis loops and enhanced electric breakdown strength. Particularly, the 0.85(0.7BNT-0.3ST)-0.15BFN ceramics achieved a high recoverable energy density of 5.7 J/cm3 and a high energy storage efficiency of 86.4% under a moderate electric field of 390 kV/cm. Additionally, remarkable stability in frequency, cycling, and temperature and excellent charge/discharge behavior were achieved at the same time. The above findings reveal that BFN-modified BNT-ST ceramics display greatly improved comprehensive energy storage properties, making them promising candidates in the field of electrostatic energy storage. [ABSTRACT FROM AUTHOR]

The crystal structures of Bi1−xNdxFeO3 and Bi1−xGdxFeO3 solid solutions (0 ≤ x ≤ 0.2) with chemical compositions across structural transformations from the polar rhombohedral phase to the orthorhombic phase with an antipolar distortion and then to the nonpolar orthorhombic phase have been investigated using X-ray diffraction and infrared reflective spectrometry. The obtained results clarify details of the structural transitions assuming the changes that occurred in the crystal lattice dynamics of the compounds. Increase in the dopant content causes a notable change in the intensity and position of the reflectance lines at 18.2 μm and 22.6 μm (550 cm−1 and 440 cm−1) ascribed to the transverse optical phonon modes associated with Bi (Nd, Gd)–O and Fe–O bonds. In the concentration region attributed to the dominant rhombohedral phase, the chemical substitution leads to an increase in intensity of the modes A1 for solid solutions of both systems. Meanwhile, in the case of Gd doping, the mode A1 shifts towards the red side of the spectrum, but there is an opposite tendency in the case of Nd doping; the intensity of the modes E decrease regardless of both the dopant-ion type and concentration. This behavior is discussed assuming the change in mass for the chain of chemical bonds caused by different dopant ions and the structural transformations occurring in the compounds upon chemical doping. [ABSTRACT FROM AUTHOR]

The compound BiFe0.7Mn0.3O3 consisting at room temperature of coexistent anti-polar orthorhombic and polar rhombohedral phases has a metastable structural state, which has been studied by laboratory X-ray, synchrotron and neutron diffraction, magnetometry, differential thermal analysis, and differential scanning calorimetry. Thermal annealing of the sample at temperatures above the temperature-driven phase transition into the single phase rhombohedral structure (~700 K) causes an increase of the volume fraction of the rhombohedral phase at room temperature from ~10% up to ~30%, which is accompanied by the modification of the magnetic state, leading to strengthening of a ferromagnetic component. A strong external magnetic field (~5 T) applied to the sample notably changes its magnetic properties, as well as provides a reinforcement of the ferromagnetic component, thus leading to an interaction between two magnetic subsystems formed by the antiferromagnetic matrix with non-collinear alignment of magnetic moments and the nanoscale ferromagnetic clusters coexisting within it. The modification of the structural state and magnetic properties of the compounds and a correlation between different structural and magnetic phases are discussed focusing on the effect of thermal annealing and the impact of an external magnetic field. [ABSTRACT FROM AUTHOR]

The crystal structure and magnetic state of the (1 − x)BiFeO3-(x)BiMnO3 solid solution has been analyzed by X-ray diffraction using lab-based and synchrotron radiation facilities, magnetization measurements, differential thermal analysis, and differential scanning calorimetry. Dopant concentration increases lead to the room-temperature structural transitions from the polar-active rhombohedral phase to the antipolar orthorhombic phase, and then to the monoclinic phase accompanied by the formation of two-phase regions consisting of the adjacent structural phases in the concentration ranges 0.25 < x1 < 0.30 and 0.50 ≤ x2 < 0.65, respectively. The accompanied changes in the magnetic structure refer to the magnetic transitions from the modulated antiferromagnetic structure to the non-colinear antiferromagnetic structure, and then to the orbitally ordered ferromagnetic structure. The compounds with a two-phase structural state at room temperature are characterized by irreversible temperature-driven structural transitions, which favor the stabilization of high-temperature structural phases. The magnetic structure of the compounds also exhibits an irreversible temperature-induced transition, resulting in an increase of the contribution from the magnetic phase associated with the high-temperature structural phase. The relationship between the structural parameters and the magnetic state of the compounds with a metastable structure is studied and discussed depending on the chemical composition and heating prehistory. [ABSTRACT FROM AUTHOR]

As one of the important electronic components, the dielectric capacitors for energy storage applications have been extensively studied in recent years. Among various dielectric materials, the perovskite oxide Bi0.5Na0.5TiO3‐based ceramics have become promising candidates due to their high polarization, dielectric tunability, environment‐friendly composition, and so forth. Herein, the relaxor ferroelectric ceramics of Bi0.5Na0.5TiO3–SrTiO3–Bi(Mg0.5Zr0.5)O3 were prepared via solid‐state reaction method. The sample with optimal composition not only retains the high polarization by introducing Bi3+ ions, but also achieves the reduced remanent polarization by enhancing relaxor behavior and the promoted electric breakdown strength by the grain size refinement. Accordingly, a high recoverable energy density of 8.3 J/cm3 under 450 kV/cm and the superb charge/discharge properties (current density CD = 1200 A/cm2, power density PD = 150 MW/cm3, charge/discharge time t0.9 = 0.15 µs) are achieved, revealing great prospect in energy storage applications. [ABSTRACT FROM AUTHOR]

Bi1− x La x FeO3 and Bi1− x Pr x FeO3 ceramics of the compositions near the morphotropic phase boundary have been studied by X-ray and neutron diffraction techniques and differential thermal analysis. The structural phases characterized by the long-range polar, antipolar, and nonpolar ordering as well as the phase coexistence regions have been identified using the diffraction data depending on the dopant concentration and temperature. As a result of these studies the three phase region has been observed for the Pr -doped compounds and the phase diagrams have been constructed. The detailed evolution of the structural parameters permitted to itemize the factors affecting the structural phase transitions and clarify the origin of the enhanced electromechanical properties in these materials. The performed structural analysis disclosed different character of the chemical bonds in the La - and Pr -doped BiFeO3 compounds. Further, the role of the rare-earth ions in the covalency of the chemical bonds is discussed. [ABSTRACT FROM AUTHOR]

The structural state and crystal structure of Lu(1−x)ScxFeO3 (0 ≤ x ≤ 1) compounds prepared by a chemical route based on a modified sol–gel method were investigated using X-ray diffraction, Raman spectroscopy, as well as scanning electron microscopy. It was observed that chemical doping with Sc ions led to a structural phase transition from the orthorhombic structure to the hexagonal structure via a wide two-phase concentration region of 0.1 < x < 0.45. An increase in scandium content above 80 mole% led to the stabilization of the non-perovskite bixbyite phase specific for the compound ScFeO3. The concentration stability of the different structural phases, as well as grain morphology, were studied depending on the chemical composition and synthesis conditions. Based on the data obtained for the analyzed samples, a composition-dependent phase diagram was constructed. [ABSTRACT FROM AUTHOR]

The concentration range of the stability of polar ( R3 c) and antipolar phases in the Bi1− x RE x FeO3 (RE-La - Dy) solid solutions has been determined by X-ray study of the polycrystalline samples. Both polar and antipolar phases become less stable with a decrease of the rare earth ionic radii. It is stimulated by a reduction of the rare-earth ions polarizability with a decrease in ionic radii. The antipolar phase is characterized by a weak ferromagnetic state, whereas the polar one exhibits dominantly antiferromagnetic behavior near the polar-antipolar morphotropic boundary. The local piezoelectric response decreases with increase in antipolar phase content in the mixed polar-antipolar structural state. It is suggested that the piezoelectric activity is associated with polar ( R3 c) phase. [ABSTRACT FROM AUTHOR]

The crystal structure of BiMnO3+δ ceramics has been studied as a function of nominal oxygen excess and temperature using synchrotron and neutron powder diffraction, magnetometry and differential scanning calorimetry. Increase in oxygen excess leads to the structural transformations from the monoclinic structure (C2/c) to another monoclinic (P21/c), and then to the orthorhombic (Pnma) structure through the two-phase regions. The sequence of the structural transformations is accompanied by a modification of the orbital ordering followed by its disruption. Modification of the orbital order leads to a rearrangement of the magnetic structure of the compounds from the long-range ferromagnetic to a mixed magnetic state with antiferromagnetic clusters coexistent in a ferromagnetic matrix followed by a frustration of the long-range magnetic order. Temperature increase causes the structural transition to the nonpolar orthorhombic phase regardless of the structural state at room temperature; the orbital order is destroyed in compounds BiMnO3+δ (δ ≤ 0.14) at temperatures above 470 °C. [ABSTRACT FROM AUTHOR]

The paper describes preparation features of functional composites based on ferrites, such as "Ba(Fe1−xGax)12O19/epoxy," and the results of studying their systems; namely, the correlation between structure, magnetic properties and electromagnetic absorption characteristics. We demonstrated the strong mutual influence of the chemical compositions of magnetic fillers (Ba(Fe1−xGax)12O19 0.01 < x < 0.1 solid solutions), and the main magnetic (coercivity, magnetization, anisotropy field and the first anisotropy constant) and microwave (resonant frequency and amplitude) characteristics of functional composites with 30 wt.% of hexaferrite. The paper presents a correlation between the chemical compositions of composites and amplitude–frequency characteristics. Increase of Ga-content from x = 0 to 0.1 in Ba(Fe1−xGax)12O19/epoxy composites leads to increase of the resonant frequency from 51 to 54 GHz and absorption amplitude from −1.5 to −10.5 dB/mm. The ability to control the electromagnetic properties in these types of composites opens great prospects for their practical applications due to high absorption efficiency, and lower cost in comparison with pure ceramics oxides. [ABSTRACT FROM AUTHOR]

We studied magnetostatic response of the Bi0.9La0.1FeO3– KBr composites (BLFO-KBr) consisting of nanosized (≈100 nm) ferrite Bi0.9La0.1FeO3 (BLFO) conjugated with fine grinded ionic conducting KBr. When the fraction of KBr is rather small (less than 15 wt%) the magnetic response of the composite is very weak and similar to that observed for the BLFO (pure KBr matrix without Bi1-xLaxFeO3 has no magnetic response as anticipated). However, when the fraction of KBr increases above 15%, the magnetic response of the composite changes substantially and the field dependence of magnetization reveals ferromagnetic-like hysteresis loop with a remanent magnetization about 0.14 emu/g and coercive field about 1.8 Tesla (at room temperature). Nothing similar to the ferromagnetic-like hysteresis loop can be observed in Bi1-zLazFeO3 ceramics with z ≤ 0.15, which magnetization quasi-linearly increases with magnetic field. Different physical mechanisms were considered to explain the unusual experimental results for BLFO-KBr nanocomposites, but only those among them, which are highly sensitive to the interaction of antiferromagnetic Bi0.9La0.1FeO3 with ionic conductor KBr, can be relevant. [ABSTRACT FROM AUTHOR]