Single Perovskite Phase Research Articles

Substitution of Ce4+ for ionic at both A/B sites greatly improves the microwave responses of (Sr0.9Ca0.1)1/2La1/2Al1/2Ti1/2O3 perovskite ceramics

In this paper, (Sr0.9Ca0.1)1/2La1/2Al1/2Ti1/2O3-x wt.% CeO2 (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) ceramics were synthesized via solid state reaction. The effects of Ce4+ doping on microstructure and microwave dielectric properties were studied. All samples crystallized as perovskite single-phase. Ce4+ substitution for La3+ occurred at the A site for 0 < x ≤ 0.4, and for Ti4+ at the B site for 0.4 ≤ x ≤ 0.5. Oxygen vacancy concentration was linked to substitution sites, decreasing for x ≤ 0.3 and increasing for x ≥ 0.4, as shown by XPS analysis. The quality factor was influenced by oxygen vacancies, grain size, and packing fraction. Bonding valence and oxygen octahedral distortion affected the temperature coefficient of resonant frequency. At x = 0.4 and sintered at 1570 °C, the ceramics showed excellent properties: εr = 38.83, Q×f = 54058 GHz, τf = 2.137 ppm/°C, making it a promising low-loss dielectric ceramic for microwave communication applications.

Different enhancement of Ni doping on La0.3Sr0.7Fe0.9Ti0.1O3-δ electrodes in symmetrical solid oxide cell

Poor catalytic activity is a significant challenge that needs to be addressed to enable the effective use of perovskite electrodes in symmetrical solid oxide cell (SOC). In this study, high-activity Ni ions were doped into the La0.3Sr0.7Fe0.9Ti0.1O3-δ (LSFTi91) perovskite lattice, which endowed the materials with different facilitation effects in different atmospheres. In an oxidizing atmosphere, the introduction of Ni ions enables La0.3Sr0.7Fe0.8Ti0.1Ni0.1O3-δ (LSFTNi811) to exhibit higher conductivity and oxygen vacancy content, which enhances the adsorption and dissociation of gases. When used as symmetrical electrodes in a solid oxide electrolysis cell, the LSFTNi811 symmetric cell presents higher electrolysis performance than LSFTi91 (1.78 A cm−2 vs. 1.57 A cm−2) at 1.5 V and 800 °C. This is the highest level reported for a single-phase perovskite electrode, underlining its excellent catalytic activity. In a reducing atmosphere, although Ni doping weakens the structural stability of the material, a large number of NiFe nanoparticles precipitate the H2 reaction after material decomposition. In this situation, LSFTNi811 achieves better performance than LSFTi91 as a symmetrical electrode for the solid oxide fuel cell both before and after decomposition. Therefore, LSFTNi811 is a promising symmetrical electrode material for SOCs.

Structural and Electrochemical Characterisation of NBZFO Cobalt-Free Cathode Material for Intermediate-Temperature Solid Oxide Fuel Cells: An Experimental Investigation

Compared to other energy-generating technologies and energy conversion devices, intermediate-temperature solid oxide fuel cells (IT-SOFCs) have gained significant attention from energy experts due to its high energy density, moderate operating temperature (600–800°C), low emissions and reliability. Enhancing the performance of IT-SOFCs requires suitable and excellent cathode materials. Thus, a perovskite-type Nd0.5Ba0.5Zr0.8Fe0.2O3+δ (NBZFO) material was synthesised via traditional solid-state reaction technique and analysed as a potential cathode material for IT-SOFCs. Analysis of X-ray diffraction data (XRD) revealed a single-phase perovskite material that crystallises in cubic space group (pm-3m). The thermal and electrochemical properties were analysed with the aid of thermogravimetric analysis (TGA) and electrochemical impedance spectroscopy (EIS). NBZFO has an electrical conductivity in air of 80 S cm−1 at 400°C and a polarisation resistance (Rp) of 0.106 Ω cm2 at 800°C. TGA reveals a slight loss in weight of about 0.58%, thereby suggesting a highly stable cathode material for IT-SOFC. Electrochemical investigation shows that NBZFO has good electronic and ionic conductivity and excellent oxygen stichometry. Further studies are required to understand the effects of varying B-site composition of the cathode material.

(Ba0.5Sr0.5)(Ti0.25Zr0.25Hf0.25Sn0.25)O3: A novel thermal barrier material with low thermal conductivity and excellent resistance to CMAS corrosion

High entropy ceramics are considered as promising materials for thermal barrier coatings due to phonon scattering caused by lattice distortion. In this study, perovskite high-entropy ceramics (Ba0.5Sr0.5)(Ti0.25Zr0.25Hf0.25Sn0.25)O3 (BSTZHS) were successfully prepared by dramatically increasing the conformational entropy of ceramics with complex crystal structures. The results showed that the sample exhibits a single-phase perovskite crystal structure with a dense surface, each element of the sample was uniformly distributed. Moreover, the thermal conductivity of (Ba0.5Sr0.5)(Ti0.25Zr0.25Hf0.25Sn0.25)O3 decreased significantly compared to SrZrO3 and BaZrO3 (the minimum thermal conductivity is 1.37 W/(m·K) at 273–1273 K). This study also identified descriptors for predicting the decrease in thermal conductivity of perovskite high-entropy ceramics. As well, the samples not only exhibit outstanding mechanical properties (Young’s modulus E = 255.7 ± 8.6 GPa、flexural strength Fb = 142.1 ± 4.8 MPa), but also good resistance to CMAS corrosion. Various results support that (Ba0.5Sr0.5)(Ti0.25Zr0.25Hf0.25Sn0.25)O3 is potential to be used for thermal barrier coatings.

Enhanced Electrochemical Performance of Double Perovskites as Cathodes in Reversible Ceramic Electrochemical Cells through Nb Doping

Efficient and cost-effective generation of electricity and hydrogen holds promise through reversible protonic ceramic electrochemical cells (R-PCECs). However, the successful commercialization of R-PCECs depends on the advancement of air electrodes that are both highly active and durable. Here, we made an air electrode material with two phases of double perovskite and single perovskite by doping Nb into B-site of the traditional PrBaCo2O6 double perovskite. The coexistence of the mixed double perovskite and single perovskite phases demonstrates superior electrochemical performance and durability compared to pristine double perovskite and single perovskite materials when employed as cathode materials. X-ray photoelectron spectroscopy (XPS), synchrotron radiation X-ray absorption spectroscopy (XAS) and neutron diffraction analysis reveal that this enhancement is primarily attributed to the introduction of high-valence Nb5+, resulting in an increased number of oxygen vacancies and structural stability. The findings presented in this study contribute valuable insights into the design and development of advanced cathode materials for solid oxide fuel cells and electrolyzers, with the potential for applications in sustainable energy conversion and storage technologies.

Long-Term Comparisons of Photoluminescence Affected by Organic Cations of Formamidinium and Methylammonium in Monophasic Lead Iodide Perovskite Quantum Dots.

This study compared the photoluminescence (PL) stabilities of formamidinium (FA) and methylammonium (MA) in lead iodide perovskite quantum dots (QDs). To exclude other factors, such as size and purity, that may affect stability, MAPbI3 and FAPbI3 QDs with nearly identical sizes (~10.0 nm) were synthesized by controlling the ligand concentration and synthesis temperature. Transmission electron microscopy images and X-ray diffraction patterns confirmed homogeneous single-phase perovskite structures. Additionally, the bandgaps and sizes of the synthesized QDs closely matched those of the infinite quantum well model, which guaranteed that the photostability was solely caused by the different organic molecules in the two QDs. We analyzed the PL peak centers and full-width at half maximum of the QDs for 32 days. The enhanced stability of FAPbI3 was found to be caused by the nearly zero redshift (1.615 eV) of its PL peak, in contrast to the redshift (1.685→1.670 eV) of MAPbI3.

Application of the electrospinning technique in the preparation of selected electrode materials for solid oxide fuel cells

Abstract The electrospinning technique was applied to prepare cathode materials for solid oxide fuel cells (SOFCs). The research aimed to determine the influence of the Poly(vinylpyrrolidone) (PVP) content in the solution of a Sm0.5Ba0.25Sr0.25Co0.5Cu0.5O3-d perovskite oxide on the properties of the spun material, and consequently, on the performance of the fuel cell. The chosen material, commonly used as a cathode material for SOFCs, has been altered by the replacement of toxic barium and cobalt with less harmful strontium in the A-site and copper in the B-site. A single-phase perovskite structure was obtained after annealing at 900°C for two hours. The research included a process of preparing the precursor solution and obtaining samples by the electrospinning technique, followed by a series of studies to determine the morphology and phase composition, electrode and cell fabrication, and characterization of their electrochemical properties. The results indicated that material derived from a precursor with the addition of 15 wt.% PVP had the lowest polarization resistance values (e.g. 0,865 Ω cm−2 at 800 °C) between 600°C - 900°C temperature range. This material was then screen-printed on a commercial anode-supported fuel cell as a cathode layer, which allowed to achieve a promising power density value close to 300 mW cm−2 at 800 °C.

Enhanced dielectric response and non-Ohmic properties of Cd-doped Na1/3Ca1/3Bi1/3Cu3Ti4O12 ceramics

In this study, Na1/3(Ca1−xCdx)1/3Bi1/3Cu3Ti4O12 (x = 0, 0.2, 0.4, 0.8, and 1.0) ceramics were prepared via solid-state method. Effects of substitution of Ca2+ with Cd2+ on the microstructure, dielectric response, and non-Ohmic properties of Na1/3Ca1/3Bi1/3Cu3Ti4O12 ceramics were studied systematically. Results showed that all samples possessed single perovskite phase, in which grain size increased with the increase in Cd2+ doping content. Energy band gaps and activation energy first increased and then decreased, achieving their maxima (4.22 and 0.642 eV, respectively) at x = 0.2. Besides, dielectric constant of doped samples increased with the decrease in dielectric loss in frequency range of 40–106 Hz. Moreover, improvement in non-Ohmic properties was also observed with Cd2+ doping. The optimal dielectric properties (dielectric constant of ∼12,500, dielectric loss of ∼0.032 at 10 kHz, nonlinear coefficient of ∼3.42, and breakdown strength of ∼2.7 kV·cm−1) were achieved at x = 0.2. Dielectric response mechanism of ceramics followed internal barrier layer capacitor model while nonlinear ohmic properties were derived from Schottky barrier structure. Dielectric relaxation peaks at high temperatures (120 °C–220 °C) were associated with grain boundaries. Therefore, partial substitution of Ca2+ with Cd2+ can improve simultaneously dielectric and non-Ohmic properties of Na1/3Ca1/3Bi1/3Cu3Ti4O12 ceramics, which is conducive to their application in high-energy-density storage capacitors and varistors.

Synthesis of B-site high-entropy BaTi0.2Hf0.2Zr0.2Y0.2Nb0.2O3 with water sensing properties

A barium-based perovskite structured ceramic with five different B-site cations was prepared by a solid-state synthesis method. The phase and chemical homogeneity of the synthesised material was verified using x-ray diffraction and energy dispersive x-ray spectroscopy, showing the successful synthesis of a single-phase perovskite structure with Ba A-site and Ti, Hf, Zr, Y, Nb, B-site cations. Ultra-high vacuum x-ray photoelectron spectroscopy was used to reveal the valence states of the constituent elements. Conventional, two-step and spark plasma sintering were used to form dense pellets with limited grain growth. The room temperature electrical characteristics of the sintered pellets were investigated by electrochemical impedance spectroscopy where a conductivity increase of two orders of magnitude was observed in a water-bearing atmosphere. Synchrotron-based ambient-pressure x-ray photoelectron spectroscopy performed under water-bearing and dry conditions suggest that the conductivity increase is related to the incorporation of hydroxyl groups into the perovskite structure.

Metal-oxide nanocomposites by low temperature exsolution from perovskite-like La nickelates: Synthesis, morphology, and catalytic properties in CO2 hydrogenation

Thermal decomposition of the citrate-gel precursors with La/Ni = 1/1 and La/Ni = 3/2 results in the formation at T ≥ 700 °C the single phase perovskite LaNiO3 and the disordered perovskite-like phase La3Ni2O6+x. A reduction of both compounds during thermal processing in a 5 % H2/Ar gas mixture proceeds in two definite steps. The first stage of LaNiO3 reduction at 250 - 350 °C results in the formation of an O-deficient La2Ni2O5 compound. A similar process during the reduction of La3Ni2O6+x occurs at 300–400 °C with the lack of significant changes in the XRD pattern. An unusual feature of these processes deals with the formation of Ni0 nanoparticles on the surface of both reduction intermediates at 350–400 °C while similar processes are usually observed during redox exsolution of metals from several complex oxides at T > 700 °C only. As-obtained Ni/LaxNiOy nanocomposites demonstrated significant catalytic activity and excellent selectivity and stability in the Sabatier reaction.

Relaxation and energy storage properties of NaNb0.98Ta0.02O3 modulated (Na0.5Bi0.5)0.935Sr0.065TiO3 ceramics

Dielectric capacitors with excellent power density and rapid charge-discharge rates have received significant attention in the field of pulsed power. In this study, anti-ferroelectric NaNb0.98Ta0.02O3 was doped into (Na0.5Bi0.5)0.935Sr0.065TiO3 ceramics, resulting in a substantial improvement of the integrated energy storage performance of the ceramics. Multiscale testing confirmed that the ceramic system formed a dense solid solution with a single-phase perovskite structure. Increasing the content of NaNb0.98Ta0.02O3 effectively enhances the relaxation and energy storage properties of the ceramics, while reducing average grain size improves their breakdown field strength, leading to excellent electrical properties at 30 kV/mm field strength when x = 0.2 for this ceramic system - exhibiting recoverable energy storage density Wrec = 7.98 J/cm3 and energy storage efficiency η = 90 %. Furthermore, it demonstrates excellent stability over a wide frequency range (5–90 Hz): Wrec = 7.97 ± 2 % J/cm3, η = 89 ± 1 %; as well as stability over a wide temperature range (30–200 °C): Wrec = 7 ± 2 % J/cm3, η = 89 ± 1 %, along with a rapid charging-discharging rate t0.9 = 0.32 μs. These outstanding properties indicate great prospects for future applications of this ceramic system in the field of energy storage capacitors.

Unraveling Halogen Role in Two-Step Solution Growth of Organic-Inorganic Hybrid Mixed-Halide Perovskites: Guidelines of Fabricating Single-Phase Perovskites with Predictable Stoichiometry.

The challenge faced in optoelectronic applications of halide perovskites is their degradation. Minimizing material imperfections is critical to averting cascade degradation processes. Identifying causes of such imperfections is, however, hindered by mystified growth processes and is particularly urgent for mixed-halide perovskites because of inhomogeneity in growth and phase segregation under stresses. To unravel two-step solution growth of MAPbBr x I3-x , we monitored the evolution of Br composition and found that the construction of perovskite lattice is contributed by iodine from PbI2 substrate and Br from MABr solution with a 1:1 ratio rather than a 2:1 ratio originally thought. Kinetic analysis based on a derived three-stage model extracted activation energies of perovskite construction and anion exchange. This model is applicable to the growth of PbI2 reacting with a mixed solution of MABr and MAI. Two guidelines of fabricating single-phase MAPbBr x I3-x with predictable stoichiometry thus developed help strategizing protocols to reproducibly fabricate mixed-halide perovskite films tailored to specific optoelectronic applications.

Low temperature sintering and enhanced piezoelectric properties of BiFeO3–BaTiO3 ceramics by homogeneous calcination

The effect of calcination process on a phase evolution, a microstructure development and the piezoelectric properties were investigated in 0.75BiFeO3-0.25BaTiO3 (0.75BF-0.25BT) ceramics. At the relatively low calcination temperatures of 600 °C–650 °C, a Bi25FeO40 impurity phase was formed in addition to some unreacted raw materials and a perovskite phase. As the calcination temperature increased to the range of 700–900 °C, other intermediate phase BaBi4Ti4O15 was formed concurrently with small amounts of unreacted BaCO3 and perovskite matrix phase. At 950 °C a pure single perovskite phase of 0.75BF-0.25BT solid solution was observed. The sintered samples produced by using the raw powder calcined at a relatively low temperature of 600–900 °C showed a large fraction of pseudo-cubic relaxor phase (0.54–0.71 mass fraction) with the rest of a rhombohedral ferroelectric phase. They showed poor piezoelectric properties at sintering temperature below 1000 °C due to the nonuniform compositional distribution of the calcined powder. The homogeneous calcination at 950 °C for 2 h reduced greatly the optimum sintering temperature and significantly enhanced piezoelectric properties in the BF-BT ceramics. High Curie temperature as well as high piezoelectric properties were obtained at the sintering temperature as low as 920 °C: kp = 0.361, d33 = 123 pC/N and TC = 653 °C in the 0.75BF-0.25BT ceramics and kp = 0.337, d33 = 183 pC/N and TC = 525 °C in the 0.7BF-0.3BT ceramics. This low temperature sintering of the BF-BT ceramics by a homogeneous calcination could be applied to the fabrication of the lead-free multi-layer piezoelectric devices with inexpensive internal electrodes.

Unveiling high resistivity mechanism in (0.8-x)BaTiO3-0.2BiScO3-x(Bi0.5Li0.5)TiO3 ceramics with good dielectric temperature-stability

Focusing on the high resistivity together with low intrinsic conduction in BaTiO3–BiMeO3 materials, it can contribute to the development of reliable high-temperature capacitor materials. In this work, x(Bi0·5Li0.5)TiO3-(0.8-x)BaTiO3-0.2BiScO3 (where x ranges from 0 to 0.2) ceramics were fabricated by a solid reaction method. The temperature stability of dielectric permittivity and resistance are improved significantly by the introduce of (Bi0·5Li0.5)TiO3 (referred to as BL) compared to BaTiO3–BiMeO3. The composition discrepancy due to chemical inhomogeneity can be determined by SEM and EDS mapping although XRD exhibit a single perovskite phase. The characteristics of distinct conductivity behaviors in micro-regions was measured by kelvin probe force microscopy (KPFM). The non-stoichiometry gives rise to two kinds of defects for charge compensation: an ionic compensation and oxygen-vacancy compensation in different grains. The increase of the hopping activation energy of charged carries enhances the high-temperature resistance of the system. The sample of x = 0.15 shows very good temperature stability of dielectric permittivity in the temperature range from 200 °C to 400 °C, and that of x = 0.1 exhibits the highest resistivity of 3.6 MΩ cm at 570 °C. The proposed method gives an efficient strategy for improving the dielectric temperature stability and insulation by the special defect compensation in the perovskite oxides.

Fabrication and performance investigation of high entropy perovskite (Sr0.2Ba0.2Bi0.2La0.2Pr0.2)FeO3 IT-SOFC cathode material

The high-entropy oxide (HEO) concept expands the design space of solid oxide fuel cell (SOFC) cathode materials. There is great potential for the development of HEO cathode materials that has not been fully explored, and the relationship between their chemical composition, grain size, and electrochemical performance is not yet fully understood. This experimental design involved the preparation of single-phase perovskite (Sr0.2Ba0.2Bi0.2La0.2Pr0.2)FeO3 HEO SOFC cathode materials, and we systematically studied the effects of synthesis temperature and microstructure on their electrochemical performance. The results show that as the synthesis temperature increases, structural transformations from multiphase to single-phase perovskite HEO can be observed. It exhibits excellent conductivity and electrochemical performance (the minimum polarization resistance reaches 0.033 Ω∙cm2, and the maximum power density is 664 mW∙cm−2). The single-phase perovskite HEO sample exhibits higher electrochemical performances compared to those of multiphase perovskite. Furthermore, it exhibits outstanding ability to suppress Sr segregation, chemical compatibility with Ce0.8Sm0.2O1.9(SDC), and CO2 tolerance performance. The Distribution of relaxation time(DRT) analysis shows that as the synthesis temperature (1000–1150 ℃) increase, HEO single-phase formed and the oxygen atom reduction ability of the SBBLP samples was improved; and the adsorption of gas oxygen on the electrode surface is limited with porosity decreases. The work shows it is interesting and valuable to optimize the performance of SOFC cathode materials using a high entropy design.

High inverse piezoelectric coefficient achieved in Sr2+‐doped KNN‐based lead‐free piezoceramics

AbstractHigh inverse piezoelectric coefficients are crucial for the effective use of piezoelectric ceramics as actuators. In this study, we focused on the design and preparation of (K0.5−xNa0.5−xSrx) (Nb0.8Ta0.2)O3 (x = 0, 0.01, 0.02, 0.03) by defect engineering and investigated the effect of Sr2+ doping on its electrical properties. The results showed that a single perovskite phase can be achieved when Sr2+ doping is less than 3 mol%. Furthermore, Sr2+ doping was found to cause a linear decrease in both the Curie temperature (TC) and the orthorhombic–tetragonal phase transition temperature (TO‐T). The ceramic with x = 1% showed optimal piezoelectric properties, exhibiting an electric field‐induced strain of 0.124% under a low driving electric field of 20 kV/cm. This corresponds to an inverse piezoelectric coefficient () of 620 pm/V, which is comparable to that of commercial PZT piezoelectric ceramics. This study not only provides potential piezoelectric ceramics for actuators but also serves as a reference for developing high‐performance piezoelectric ceramics.

Reactive templated grain growth of Pb(Mg1/3Nb2/3)O3–PbTiO3 ceramics using MgO-doped (Na,Bi)0.4Pb0.6TiO3 template

Textured Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN-PT) piezoelectric ceramics with an anisotropic crystal structure were fabricated by reactive templated grain growth (RTGG) using MgO-doped (Na1/2Bi1/2)TiO3–PbTiO3 (MNBT-PT) seed. The crystal growth of MNBT-PT seed was stimulated by the addition of MgO, resulting in a rectangular single-crystal template with a width of 5∼20 μm and a thickness of 3∼5 μm. These rectangular MNBT-PT seeds effectively reduced the sintering temperature of the PMN-PT matrix, and the reaction occurred through in-situ topochemical conversion, leading to a single perovskite phase with an oriented texture. Because the MNBT-PT seeds with tetragonal structure altered the crystal structure matrix phase to be tetragonal-rich, the matrix phase of PMN-PT had to be optimized by adjusting the PMN/PT ratio to achieve optimal piezoelectric properties. The textured PMN-PT piezoelectric ceramic created using the reactive MNBT-PT seeds demonstrated superior piezoelectric/ferroelectric properties (d33 of 951 pC/N, kp of 0.64 and Pr of 24.9 μC/cm2) compared to ceramics with BaTiO3 (BT) seed made under the same conditions. This improvement is likely due to the formation of a textured single phase crystal structure.

Evidence of a Large Refrigerant Capacity in Nb-Modified La1.4Sr1.6Mn2−xNbxO7 (0.0 ≤ x ≤ 0.15) Layered Perovskites

In this work, evidence of isothermal magnetic entropy change (∆SM) over a broad temperature region is presented in a series of La1.4Sr1.6Mn2−xNbxO7 Ruddlesden–Popper compounds with niobium modification (Nb) (0.0 ≤ x ≤ 0.15) at the manganese (Mn) site. The ceramic samples were obtained through a solid-state sintering method in optimized conditions. All compounds predominantly possessed Ruddlesden–Popper phase while a few additional reflections were resolved in Nb-doped compounds which indicates the separation of structural phases. These peaks are assigned to a separate layered perovskite and single perovskite with tetragonal symmetry and hexagonal symmetry, respectively. The microstructure of the pure sample reveals uniform grain morphology but in Nb-doped specimens chiefly three types of grains were found. It was assumed that the inter-connected large particles were of R-P phase which is dominant in both parent and x = 0.05 compounds, while the hexagonal and polygonal morphology of grains in higher concentrations of dopants directly corroborates with the symmetry of single perovskite and additional layered perovskite phases, respectively. The parent compound exhibits a single ∆SM curve, whereas all Nb-substituted samples display bifurcated ∆SM curves. This indicated two transition regions with multiple magnetic components, attributed to distinct structural phases. The highest ∆SM values obtained for components corresponding to the R-P phase are 2.32 Jkg−1k−1, 0.75 Jkg−1k−1, 0.58 Jkg−1k−1 and 0.43 Jkg−1k−1 and for the second component located around room temperature are 0.0 Jkg−1k−1, 0.2 Jkg−1k−1, 0.28 Jkg−1k−1 and 0.35 Jkg−1k−1 for x = 0.0, 0.05, 0.10 and 0.15 compositions, respectively, at 2.5 T. Due to the collective participation of both components the ∆SM was expanded through a broad temperature range upon Nb doping.

Dielectric properties and excellent energy storage density under low electric fields for high entropy relaxor ferroelectric (Li0.2Ca0.2Sr0.2Ba0.2La0.2)TiO3 ceramic

High entropy relaxor ferroelectrics, are a representative type of dielectric with exceptional properties and play an indispensable role in the next-generation pulsed power capacitor market. In this paper, a high-entropy relaxor ferroelectric ceramic (Li0.2Ca0.2Sr0.2Ba0.2La0.2)TiO3 successfully designed and synthesized using the traditional solid-state reaction method. The microstructure, dielectric properties, and energy storage characteristics of the ceramics were systematically investigated. The ceramic exhibited a dense microstructure with a single-phase perovskite structure and small grain size. The unique microstructure and high insulation not only wides the band gap, but also minimizes residual polarization and resulting in higher energy density (Eb) 1.51 J/cm3 and efficiency (η) of 89.6% at a low field strength of 260 kV/cm. Furthermore, the observed anomalous behavior in dielectric relaxation was explained within the context of high entropy ceramics. The material also exhibited excellent temperature/frequency stability and fast charging-discharging speed (∼35 ns). These results demonstrate the effectiveness of high entropy strategy to develop high-performance energy storage capacitors.

Spin-reorientation and exchange bias in perovskite YbCr0.5Fe0.5O3

Magnetic properties of single-phase perovskite YbCr0.5Fe0.5O3 are investigated in this manuscript. The single-phase perovskite YbCr0.5Fe0.5O3 exhibits spin reorientation between 25 and 50 K and exchange bias phenomenon between 50 K and Néel temperature (TN). It is proposed that the exchange bias effect mechanism in single-phase perovskite YbFe0.5Cr0.5O3 compound is due to the ferromagnetic (FM) coupling between the Yb3+ and Fe3+/Cr3+. The Yb3+ has a tendency to rotate with the external field during the demagnetization of the hysteresis loop, and the FM coupling between the Yb3+ and Fe3+/Cr3+ has a pinning effect on it, hindering its rotation. Thus, the exchange bias phenomenon occurs. According to exchange bias field of the training effect in single-phase perovskite YbFe0.5Cr0.5O3 compound, the exchange bias field can maintain a stable state after several field cycles.