Cation Disorder Research Articles

Effect of local chemical disordering on magnetic properties in high entropy manganite of variable hole concentration

A series of high entropy manganite perovskites (La0.2Pr0.2Nd0.2Bi0·2Ba0.2)MnO3, (La1/6Pr1/6Gd1/6Bi1/6Sr1/6Ba1/6)MnO3, (La0.2Nd0.2Gd0.2Sr0·2Ba0.2)MnO3 and (La1/6Pr1/6Nd1/6Ca1/6Sr1/6Ba1/6)MnO3 with variable hole concentration at fixed A-site ionic radius (<rA> = 1.253 Å) have prepared by sol-gel technique. Single phase samples were characterized by the powder X-ray diffraction (PXRD), Field Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive X-ray (EDX) analysis and elemental mapping which confirm the phase purity of the samples, surface morphology, elemental ratio and chemical homogeneity. X-ray photoelectron spectroscopic (XPS) studies reveal the increase of Mn4+ ions systematically with the substitution of hole concentration at A-site. Magnetization study in this high entropy sample with variable hole concentration at fixed <rA> = 1.253 Å exhibits several contrasting behaviour compare to the conventional hole doped samples. In these high entropy manganites the variation in critical temperature (TC) does not follow expected trend neither with the hole concentration nor to the cationic size disorder parameter, σ2. Though the <rA> is fixed, there is a slight increase in tolerance factor (f) due to hole variation in B-site. Interestingly, TC variation with f shows similar trend to the hole concentration, which is expected to be increased linearly. The effect of f on TC is rather weaker in comparison to σ2. The large drop in TC for high entropy system with respect to the conventional manganite is related to the local structural distortion which severely hampers the Mn3+—O—Mn4+ double exchange interaction. The competing magnetic interactions lead to magnetic phase separation as well as Griffith like phase. Spin pinning is noticed for the samples containing six elements in A-site which is independent on hole concentration. Possible spin clustering is also realized above ferromagnetic TC. Careful analysis of the magnetization data suggests that observed anomaly in magnetic behaviour can be ascribed to the local chemical disordering apart from the size disorder parameter. The possible role on magnetic properties of the number of elements occupying in a crystallographic site is emphasized.

X-ray absorption near-edge, terahertz and Raman spectroscopies evidence growth-orientation dependent cation order, phase transitions and spin–phonon coupling in half-metallic Ca2FeMoO6 thin films

The disorder due to anti-site cation distribution is intrinsic to the double perovskites wherein the crystal orientations of the substrate template are predicted to offer different degrees of cation order in thin film form. To demonstrate this effect, epitaxial thin films of half-metallic double perovskite Ca2FeMoO6 (CFMO) were prepared on (100) and (111) oriented LaAlO3 substrates in vacuum and nitrogen atmospheres. The findings using X-ray absorption near-edge structure, Terahertz (THz) and Raman spectroscopies, in combination with magnetization show that (111) epitaxial template effectively restricts the Fe–Mo anti-site cation disorder. A resultantly enhanced cation order in (111) films induces dramatic transformations in its properties as follows: (i) significantly enhanced ferromagnetic exchange interactions and saturation magnetization, (ii) a significant increase in the Curie temperatures, (iii) a metallic behavior down to much lower temperature (∼75 K) compared to that down to 200 K for (100) film, (iv) an enhanced spin–phonon coupling. The complex THz optical conductivity spectra evaluated in the framework of Drude and Drude–Smith phenomenological models and the temperature-dependent Raman data fitted to the Balkanski model corroborate well to indicate an enhanced cation order in (111) films. While this study establishes a dominant role of crystallographic orientation in the much-desired control of cation order in double perovskites, a demonstration of the same in room temperature half-metallic CFMO system could reinforce its technological utility both as active and passive components in emergent spintronic functionalities.

Revealing performance limiting factors in Cu2BaSnS4 thin film solar cells

Cation disorder in Cu2ZnSnS4 (CZTS) thin films has been a critical issue in realizing high efficiency solar cells. Recently, Ba substitution in CZTS that yields Cu2BaSnS4 (CBTS) has been suggested to improve the cation ordering and hence, the device performance. Although CBTS solar cells have shown very promising results in a short span of time, their performance is still inferior to that of the CZTS devices. In this work, the performance limiting factors in the CBTS solar cells have been systematically investigated and a pathway to improve it beyond the reported maximum efficiency has been suggested. In particular, the decisive role of defect densities at back and top interfaces (i.e., MoS2/CBTS and CBTS/CdS) and in the bulk CBTS, coefficients of various recombinations, and thickness of layers has been established. The effect of bulk defect density was found to be more profound compared to that due to the defects at the interfaces. Considerable improvement in efficiency was achieved by optimizing coefficients of Auger and radiative recombinations, carrier density of CBTS and CdS layers and facilitating current transport by tailoring the band alignment at the CBTS/CdS junction. The proposed recipe yielded the highest efficiency of ∼11%, which is significantly higher than that of the current experimental champion cell (∼6.2%).

Ab Initio Molecular Dynamics Study of Electron Excitation Effects on UO2 and U3Si.

In this study, an ab initio molecular dynamics method is employed to investigate how the microstructures of UO2 and U3Si evolve under electron excitation. It is found that the U3Si is more resistant to electron excitation than UO2 at room temperature. UO2 undergoes a crystalline-to-amorphous structural transition with an electronic excitation concentration of 3.6%, whereas U3Si maintains a crystalline structure until an electronic excitation concentration reaches up to 6%. Such discrepancy is mainly due to their different electronic structures. For insulator UO2, once valence U 5f electrons receive enough energy, they are excited to the conduction bands, which induces charge redistribution. Anion disordering is then driven by cation disordering, eventually resulting in structural amorphization. As for metallic U3Si, the U 5f electrons are relatively more difficult to excite, and the electron excitation leads to cation disordering, which eventually drives the crystalline-to-amorphous phase transition. This study reveals that U3Si is more resistant to electron excitation than UO2 under an irradiation environment, which may advance the understanding of related experimental and theoretical investigations to design radiation-resistant nuclear fuel uranium materials.

Cation-Disorder Engineering Promotes Efficient Charge-Carrier Transport in AgBiS2 Nanocrystal Films.

Efficient charge-carrier transport is critical to the success of emergent semiconductors in photovoltaic applications. So far, disorder has been considered detrimental for charge-carrier transport, lowering mobilities, and causing fast recombination. This work demonstrates that, when properly engineered, cation disorder in a multinary chalcogenide semiconductor can considerably enhance the charge-carrier mobility and extend the charge-carrier lifetime. Here, the properties of AgBiS2 nanocrystals (NCs) are explored as a function of Ag and Bi cation-ordering, which can be modified via thermal-annealing. Local Ag-rich and Bi-rich domains formed during hot-injection synthesis are transformed to induce homogeneous disorder (random Ag-Bi distribution). Such cation-disorder engineering results in a sixfold increase in the charge-carrier mobility, reaching ≈2.7 cm2 V-1 s-1 in AgBiS2 NC thin films. It is further demonstrated that homogeneous cation disorder reduces charge-carrier localization, a hallmark of charge-carrier transport recently observed in silver-bismuth semiconductors. This work proposes that cation-disorder engineering flattens the disordered electronic landscape, removing tail states that would otherwise exacerbate Anderson localization of small polaronic states. Together, these findings unravel how cation-disorder engineering in multinary semiconductors can enhance the efficiency of renewable energy applications.

Dynamic Lone Pairs and Fluoride-Ion Disorder in Cubic-BaSnF4.

Introducing compositional or structural disorder within crystalline solid electrolytes is a common strategy for increasing their ionic conductivity. (M,Sn)F2 fluorites have previously been proposed to exhibit two forms of disorder within their cationic host frameworks: occupational disorder from randomly distributed M and Sn cations and orientational disorder from Sn(II) stereoactive lone pairs. Here, we characterize the structure and fluoride-ion dynamics of cubic BaSnF4, using a combination of experimental and computational techniques. Rietveld refinement of the X-ray diffraction (XRD) data confirms an average fluorite structure with {Ba,Sn} cation disorder, and the 119Sn Mössbauer spectrum demonstrates the presence of stereoactive Sn(II) lone pairs. X-ray total-scattering PDF analysis and ab initio molecular dynamics simulations reveal a complex local structure with a high degree of intrinsic fluoride-ion disorder, where 1/3 of fluoride ions occupy octahedral "interstitial" sites: this fluoride-ion disorder is a consequence of repulsion between Sn lone pairs and fluoride ions that destabilizes Sn-coordinated tetrahedral fluoride-ion sites. Variable-temperature 19F NMR experiments and analysis of our molecular dynamics simulations reveal highly inhomogeneous fluoride-ion dynamics, with fluoride ions in Sn-rich local environments significantly more mobile than those in Ba-rich environments. Our simulations also reveal dynamical reorientation of the Sn lone pairs that is biased by the local cation configuration and coupled to the local fluoride-ion dynamics. We end by discussing the effect of host-framework disorder on long-range diffusion pathways in cubic BaSnF4.

Chemical conversion of parasitic residual lithium compounds into beneficial artificial interface for cycle life improvement of LiNi0.8Mn0.1Co0.1O2 cathodes

LiNi0.8Mn0.1Co0.1O2 (NMC811) is the suitable cathode material for 300 Wh kg−1 lithium-ion battery packs due to their high specific capacity and operating potential of ∼3.7 V. The major bottleneck in the commercialization of NMC811 arises from the formation of residual lithium compounds (RLCs) on the surface during synthesis, its accumulation during storage, and the bulk/interfacial degradation when cycled using conventional electrolytes. Removing RLCs and ceasing their reformation complicate the material production line. Herein, we propose a single-step solution of converting parasitic RLCs into beneficial artificial interfaces by reacting RLCs with LiPF6 and Lithium Bis(oxalate)borate salts in tandem. It results in a bilayer arrangement of multiple components having LiF and Li3PO4 in the inner layer and LixBOyFz in the outer layer. The interface-modified material retains 90 % of initial capacity over 200 cycles, whereas the pristine NMC811 loses ∼50% capacity. The surface modification improves coulombic efficiency, reduces voltage polarization, lowers the growth of resistances with the progression of cycling, regulates the composition of cathode-electrolyte interphase, restricts cationic disorder, and provides interfacial stability during long-term cycling. In short, the applied methodology not only mitigates the issue of detrimental RLCs but also boosts the electrochemical performances of Ni-rich cathodes significantly.

Negative magnetization in the medium-entropy Pr1/3Dy1/3Ho1/3CrO3 and PrCrO3 ceramics: comparative crystal structure, optic, dielectric and magnetic properties

In recent years, raising investigation activity in entropy-stabilized ceramic oxides has been driven by their innovative approach to designing a thermodynamically stable multi-element system, which provides a new focus on investigating complex functional materials. Especially, complex and singular physical properties of orthochromite have generated rising research in recent years. Of this family, the PrCrO3, DyCrO3, and HoCrO3 systems are particularly interesting since, below Néel temperature (TN), they present negative magnetization in the ZFC mode. Here, we have employed this approach and designed a medium-entropy (MECs) Pr1/3Dy1/3Ho1/3CrO3 (PDH) ceramic to study not only whether the magnetic characteristics prevail, but also the state of optical and dielectric properties of this new compound. In addition, the physical properties studied were compared with the single PrCrO3 (PC) compound. These compounds were synthesized through a facile combustion synthesis route. The X-ray diffraction analysis, energy-dispersive X-ray spectroscopy (EDS), and surface scanning elemental mapping reveal that a single phase is stabilized and equimolar cations are homogeneously distributed in the PDH-MECs. We found that the disorder of cations in the A-site of the structure has no significant effect on the optical transition in the visible electromagnetic region and dielectric properties with respect to the simple compound PC. In contrast, the magnetic properties are strongly affected in the MECs-PDH compound. We found that the TN is tuned through the O–Cr–O angles and below the antiferromagnetic transition. The results suggest that the negative magnetization in the ZFC mode is an intrinsic feature in these compounds since the negative ZFC susceptibility below TN predominates despite the cationic disorder. Furthermore, their negative magnetic mechanism in both the MECs-PDH and PC compounds are discussed in terms of the Γ2(FxCyGz) magnetic configuration.Graphical abstract

A-Site Cation Disorder in SrxBa1-xNb2O6 (x = 0.25, 0.33, 0.50, 0.61) Studied by High-Resolution Resonant X-ray Powder Diffraction.

The dielectric and ferroelectric properties of SrxBa1-xNb2O6 (SBN, 0.2 < x < 0.8) are known to be affected by the Sr fraction and can be further controlled by various quenching schemes. Changes in A-site cation configuration are believed to be linked to these changes in properties. In this work, we study the A-site cation disorder in SBN by the use of high-resolution resonant X-ray powder diffraction. The experimental results show that the larger Ba2+ is found exclusively on the larger A2 site, while Sr2+ is found on both the A1 and A2 sites, with an increasing amount on A2 with an increasing Sr fraction. At elevated temperatures, a small migration of Sr2+ from A1 to A2 is observed for SBN50 and SBN61. Linking this change in occupancies to changes in the average cation size on the A1 and A2 sites allows for rationalization of the property changes observed for quenched samples. Furthermore, SBN25 is shown to deviate from the tetragonal P4bm structure and is found to be orthorhombic with a Cmm2 structure.

Electronic and Thermal Properties of the Cation Substitution-Derived Quaternary Chalcogenide CuInSnSe4.

Quaternary chalcogenides continue to be of interest for a variety of technological applications, with physical properties stemming from their structural complexity and stoichiometric variation. In certain structure types, partial vacancies on specific lattice positions present an opportunity to investigate electrical and thermal properties in light of these lattice defects. In this work, we investigated the structural, thermal, and electronic properties of CuInSnSe4, a material that belongs to a relatively unexplored class of quaternary chalcogenides with a defect adamantine crystal structure. First-principles calculations together with experimental measurements revealed a chalcopyrite-like structure with inherent vacancies and characteristic s-p and p-d orbital hybridizations in the electronic structure of the material. Cation disorder and lattice anharmonicity result in very low thermal conductivity with values significantly lower than those for related compositions. This work reveals the fundamental physical properties of a previously uninvestigated quaternary chalcogenide and may aid investigations of similar as well as other quaternary chalcogenide compositions.

Decoupling the Capacity Fading in Ni‐Rich Layered Materials during High‐Temperature Cycling in the Full‐Cell System

AbstractThe performance of commercial lithium‐ion batteries (LIBs) tends to degrade over time owing to the deterioration of key components, including cathode, anode, and electrolyte. To enhance performance, it is crucial to gain insights into the actual deterioration state of each element. Here, the high‐temperature deterioration of a Ni‐rich layered cathode is investigated, which is widely used in electric vehicles. In the refresh process after a prolonged cycle, a significant recovery of the lattice structure predominantly occurs in the discharge region. This pseudo‐deterioration of the Ni‐rich cathode within the full‐cell system is mainly due to the consumption of the Li‐ion forming the solid electrolyte interphase layer at the graphite anode during the cycle. Moreover, irreversible deteriorations that are not restored through the refresh process are observed in both charge and discharge regions. Structure analyses reveal that the long‐term cycling at the high temperature leads to a mixed fading of charge and discharge via various deterioration such as the formation of NiO‐like rock salt phase on the cathode surface and increased cation disorder in the bulk. These findings deepen the understanding of the deterioration behavior of Ni‐rich cathodes in full‐cell systems, providing insights for enhancing the performance of high‐temperature cycling.

Magnetic properties of quasi-one-dimensional Ising-chain compounds FexCo1−xNb2O6 at very low temperatures

Combining very low-temperature experiments such as neutron diffraction, magnetometry, and specific-heat measurements, we report on the magnetic properties of the FexCo1−xNb2O6 series of compounds. This investigation demonstrates that the ground state for x = 0.2, 0.4, and 0.6, previously reported as totally frustrated, is composed of Ising-like ferromagnetic chains that are antiferromagnetically ordered. Ordering at these compositions is observed to occur below 2 K. The magnetic structure is obtained from neutron diffraction, and susceptibility measurements allow us to estimate the values of intra- and interchain exchange constants, the former being clearly dominant. Fe/Co cation disorder reduces the average exchange strength within and between chains, reflecting the tendency to suppress long-range magnetic order. The diffuse magnetic signal observed by neutron diffraction slightly above the Néel temperature is analyzed to extract information on short-range magnetic correlations. Magnetization curves at 80 mK and specific-heat measurements reveal that an external magnetic field easily breaks the antiferromagnetic order, leading to a high magnetization due to the alignment of the ferromagnetic Ising chains.

In Situ Generation of Pseudorutile Oxide as the Cathode for Direct Electrolysis of CO2.

The conversion of CO2 into CO in high-temperature solid oxide electrolysis cells (SOECs) is an attractive route for the CO2 utilization using the intermittent renewables. The low-cost and highly catalytic cathode is important for the direct electrolysis of pure CO2. In this study, non-perovskite Fe0.5Mg0.25+0.5xTi0.25-0.5xNb1-xMoxO4 oxides (denoted as Mo-x when x is equal to 0, 0.1, and 0.2) are evaluated as the cathode of an SOEC for the direct electrolysis of CO2. Mo6+ doping converted the wolframite Mo-0 into an α-PbO2-type with cation disordering, while further doping to Mo-0.2 showed a wolframite with cation ordering again. The SOEC with Mo-0.2 as the cathode exhibits the best electrochemical performance for the direct electrolysis of CO2 as a large portion of the oxide converted into oxygen-deficient pseudorutile-type oxide with a nominal formula of M5O9 (M = cation). The pseudorutile, a crystallographic shear phase of rutile, can be obtained after 60 h of direct electrolysis in CO2 at a 1.3 V bias rather than a reduction under 5% H2. The SOEC with Mo-0.2 as the cathode imparted a stable current density of 0.45 A cm-2, which could be related to the production of pseudorutile decorated with nanoparticles of MoO2. These results show that molybdenum doping is an effective strategy for developing oxygen-deficient rutile (pseudorutile) for the electrolysis of CO2.

Lithium-Ion Diffusivity Increases with Block Size in Niobium Tungsten Oxide Shear Structures

Nb16W5O55 emerged as a high-rate anode material for Li-ion batteries in 2018 (Griffith et al.,Nature 2018, 559 (7715), 556–563). This exciting discovery ignited research in Wadsley-Roth (W-R) compounds, but systematic experimental studies have not focused on how to tune material chemistry and structure to achieve desirable properties for energy storage applications. In this work, we systematically investigate how structure and composition influences capacity, Li-ion diffusivity, charge-discharge profiles, and capacity loss in a series of niobium tungsten oxide W-R compounds: (3×4)-Nb12WO33, (4×4)-Nb14W3O44, and (4×5)-Nb16W5O55. Potentiostatic intermittent titration (PITT) data confirmed that Li-ion diffusivity increases with block size, which can be attributed to an increasing number of tunnels for Li-ion diffusion. The small (3×4)-Nb12WO33 block size compound with preferential W ordering on tetrahedral sites exhibits single electron redox and, therefore, the smallest measured capacity despite having the largest theoretical capacity. This observation signals that introducing cation disorder (W occupancy at the octahedral sites in the block center) is a viable strategy to access multi-electron redox behavior in (3×4) Nb12WO33. The asymmetric block size compounds (i.e., (3×4) and (4×5) blocks) exhibit the greatest capacity loss after the first cycle, possibly due to Li-ion trapping at a unique low energy pocket site along the shear plane. Finally, the slope of the charge-discharge profile increases with increasing block size, likely because the total number of energy-equivalent Li-ion binding sites also increases. This unfavorable characteristic prohibits the large block sizes from delivering constant power at a fixed C-rate more so than the smaller block sizes. Based on these findings, we discuss design principles for Li-ion insertion hosts made from W-R materials.

Removing the Two-Phase Region in Spinel LiMn2O4 Towards High-Rate, High-Energy Density Partially Disordered Spinels

Resource constraints have become critical for the Li-ion industry. Spinel LiMn2O4 presents a cheaper, more sustainable alternative to traditional layered Li-ion cathodes, but its capacity is constrained by a two-phase transition at ~3V associated with a large, inhomogeneous volume change that leads to particle cracking and poor cycling stability. In contrast, the partially disordered spinels (PDS) have more sloping, solid-solution-like behavior, resulting in better rate capability and more homogeneous volume change. In this talk, we demonstrate that PDS achieves this by introducing cation disorder, which can shrink, and even fully remove, the two-phase region. By analyzing samples from cluster expansion-based Monte Carlo simulations, we identify the mechanisms that increase Li solubility in the LiMn2O4 phase and lead to this shortened ~3V plateau. These results provide guidance on the optimal level of disorder in spinels to achieve both solid-solution behavior and good Li mobility and also highlight more generally how disorder can be utilized to reduce the effects of problematic phase transformations in ordered frameworks.

Preparation of low cobalt-doped LiNiO2 materials by the spray pyrolysis method

LiNiO2 (LNO) is recognized as the most promising cathode material for next-generation lithium-ion batteries owing to its highest energy density and economic benefit in the layered oxide cathode materials systems. However, severe cation disordering, multiple phase transformations and poor lithium-ion diffusion kinetics, which result in rapid degradation of cycling stabilities and rate properties, hinder its further practical applications. Cobalt doping is an effective strategy to address such issues, but the influences of cobalt on LNO materials have not been figured out completely yet. Hence, a systematical investigation of cobalt doping for LiNiO2 cathode materials prepared by spray pyrolysis is conducted. The addition of cobalt enhances the stabilities of layered structures and suppresses the cation disordering effectively. The multiple-phase transformations during cycling are also alleviated significantly. Furthermore, cobalt doping can decrease charge transfer resistances and improve lithium-ion diffusion kinetics, especially at high de-lithiation states. As a result, the electrochemical performances are improved comprehensively after cobalt doping. The LNO with optimal doping amount exhibits an improved capacity retention of 78.0% after 100 cycles as compared with 64.9% for pristine LNO, and an outstanding rate performance of 167.2 ​mA ​h ​g−1 with the current density of 5 ​C (1 ​C ​= ​200 ​mA ​g−1).

Solar reflective brick brown stable iron doped magnesium aluminate: Combustion synthesis, structure and chromatic properties

Spinel oxide host MgAl2O4 was chemically engineered to derive solar reflective colored pigments. The spinel oxides of the formula MgAl2-xFexO4 (x = 0.5–2.0) and Mg1-xMxAl₂O₄ (x = 0.1–0.5, M = Cu, Ni, Mn) were synthesized by combustion route. Cationic disorder in the parent MgAl2O4 was noted to transform into ordered arrangement with Fe3+ and Mn2+ ionic substitution. Fe3+ ion substitution imparted brick brown color of varied hue. Whereas, substitution of Mg2+ ion by Mn2+ and Ni2+ (x = 0.1) ions resulted in coffee brown color of light and dark shades and cyan color respectively. The optical band gap of the host (3.9 eV) decreased to 2.6–2.0 eV with Fe3+ substitution, 2.5–2.0 eV with Mn2+ ion substitution and with Ni2+ ion substitution showed slight decrease to 3.8 eV. The % solar reflectance of the phases MgAl2-xFexO4 was determined to be 73–80% with 80% in the case of MgAl1·0Fe1·0O4.

Cation inversion in slag magnetite: Energy loss measurements of Fe-L3 edge shift between atom columns

Determination of cation disorder in inverse spinels like magnetite, Fe3O4, is of broad interest for applications in green technologies, storage devices, and nuclear waste management since cation distributions govern magnetic and electrical properties. Magnetite is a main component of slags produced by smelting of copper ores and contains potentially valuable trace elements. We address cation disorder as a factor controlling the behavior of these elements during atmospheric cooling from 1300 °C. To estimate cation disorder, we combine atomic-scale scanning transmission electron microscopy with electron energy loss spectroscopy. The inversion parameter (0.72) indicates minor partial ordering due to fast cooling from high temperature, resulting in skeletal textures. Trace element incorporation into magnetite, instead of exsolution of discrete nanoparticle phases is promoted. Our findings provide insights into the cooling behavior of spinels and facilitate robust thermodynamic modeling that addresses the stability of structures during cooling from melts. Findings carry implications for critical element recovery and prospects for transforming industrial waste into future resources.

Pressure-induced structural transition of pyrochlore Tm2Sn2O7

The geometrically frustrated pyrochlore Tm2Sn2O7 is an insulator with a slight trigonal lattice distortion at ambient conditions. High pressure was applied to this system to investigate the responses of structural evolution. In-situ angle-dispersive synchrotron X-ray diffraction and Raman spectroscopy analyses have been performed on Tm2Sn2O7 up to 52.6(1) GPa and 62.1(1) GPa, respectively. It was found that Tm2Sn2O7 transformed from the cubic (Fd3̅m) structure to the orthorhombic (Pnma) structure around 36.7(1) GPa. The phase transition was mainly induced by the increased cation disorder upon compression, which efficiently modified its surrounding coordination environment. After releasing pressure, both experimental results revealed that the structural phase transition was reversible.

Structural, dielectric, and morphological properties of (1-x)Ba0.65Sr0.35TiO3-xBi(Mg2/3Nb1/3)O3

Compared to other electrical energy storage devices, dielectric capacitors provide advantages like high power density, fast charge and discharge times, thermal stability, excellent mechanical strength, and a long cycling lifetime. Amongst the various dielectric materials, relaxor ferroelectric materials offer low remanent polarization and high energy efficiency. Previous research has shown that (i) doping Bi3+ ions into perovskite material can achieve improved results because its valence electronic configuration is close to that of Pb2+ and its ionic radius is also comparable to that of Ba2+, and (ii) introducing complex ions at the B-site can reduce the long-range ferroelectric order and result in the occurrence of polar nano regions.The present work aims at (i) incorporating both these strategies for the synthesis of the dielectric ceramic material and (ii) studying the structural, morphological, and dielectric properties of the prepared material. We have successfully synthesized (1-x) Ba0.65Sr0.35TiO3 – x BiMg2/3Nb1/3O3 with the help of a conventional solid-state reaction technique. The XRD analysis demonstrates the formation of cubic perovskite structure with space group Pm3m. The diffraction peaks shift towards lower 2θ angles with an increasing concentration of BMN, indicating a regular increase in unit cell volumes owing to the substitution of the smaller Ti4+ ions with bigger Mg2+ and Nb5+ ions. FESEM images illustrate the development of a homogeneous and dense microstructure. Element mapping analysis confirms the uniform distribution of all the elements within the prepared sample. From the dielectric measurements, we found that with the increase in doping, the dielectric peak broadens, and the frequency dispersion increases, indicating a rise in the relaxor behavior, which may be attributed to the increase in cation disorder due to the substitution of Bi3+ and [Mg2/3Nb1/3]4+ at the A- and B-site, respectively. The excellent dielectric properties indicate that (1-x)BST-xBMN is a promising ceramic material for use as a dielectric in capacitors for advanced pulsed power applications and consumer electronic devices.