Cationic Oxide Research Articles

Speciation and diffusive dynamics in hydrated grain boundaries of complex oxide Gd2Ti2O7

Grain boundaries in polycrystalline materials significantly affect their properties, such as ionic transport, corrosion, and chemical durability. The pyrochlore compound (Gd2Ti2O7) is employed as a model for complex oxides and is known for its diverse applications, including nuclear waste immobilization. Density functional theory-based first-principles molecular dynamics simulations were performed at different temperatures on the hydrated grain boundary system. The results show extensive transformations within the grain boundaries among hydrous water species (OH−, H2O, and H3O+). The temperature dependence of self-diffusion coefficients follows Arrhenius behavior, with an activation energy of 35.9 kJ/mol for hydrogen and 46.3 kJ/mol for oxygen. The lifetime of OH− is about three to four times longer than that of H2O at temperatures from 800 to 2100 K, suggesting the greater stability of OH− over H2O, a unique characteristic of the grain boundaries. The estimated lifetime of the hydrous species decreases as the temperature increases, with an activation energy of 9.9 kJ/mol for OH− and 13.4 kJ/mol for H2O. While Gd3+ is more mobile than Ti4+, both the Gd3+ and Ti4+ cations are orders of magnitude less mobile than the water species. The results suggest that water species are much more mobile within grain boundaries than in the bulk crystal and have the potential to penetrate deep into polycrystalline materials through grain boundaries, leading to grain boundary degradation and dissolution. The different mobilities of cations in complex oxides can lead to leaching of certain cations and incongruent dissolution during the chemical weathering of Earth and industrial materials.

High‐Performing Perovskite/Ruddlesden‐Popper Fuel Electrode for High‐Temperature Steam Electrolysis

AbstractRuddlesden‐Popper (RP) oxides have emerged as a promising alternative to Ni cermet electrodes for high‐temperature steam electrolysis due to their superior oxide ion mobility and conductivity. Combining RP with perovskite (P) can provide superior electrocatalytic activity toward hydroxide oxidation and reduction reaction, driving higher efficiency in solid oxide cells (SOC). This work provides a novel approach to enhancing SOC performance by employing A‐site Ce‐substituted Sr0.6Pr0.4‐xCexMnO3 (x = 0.1‐0.3) electrodes, investigating their phase evolution, crystal properties, and cation oxidation states under oxidizing and reducing atmospheres. X‐ray diffraction analysis of heat‐treated powder in a reducing atmosphere revealed forming mixed P and RP structures at 600–800 °C for x = 0.1 and 0.2, which provides excellent conductivity and electrocatalytic activity. Consequently, outstanding cell performance is achieved, with low polarization resistances of 0.053 ± 0.004 Ω cm2 at 800 °C. The voltage response at different current densities in an electrolyte‐supported cell revealed a high power density of 1.084 W cm−2 in fuel cell operation and a current density of 1.00 A cm−2 at the thermoneutral voltage at 850 °C in steam electrolysis. Moreover, a low overpotential degradation rate of 45 mV kh−1 demonstrated the remarkable potential of the SPCM electrode as a promising Ni‐free candidate for SOC application.

Physicochemical properties of La0.5Ba0.5Co1-xFexO3-δ (0 ≤ x ≤ 1) as positrode for proton ceramic electrochemical cells

We report on essential properties of materials in the series La0.5Ba0.5Co1-xFexO3-δ as positrodes for proton ceramic electrochemical cells (PCECs). The unit cell and thermochemical expansion coefficient (TCEC) of these cubic perovskites decrease with iron content x, the TCEC of La0.5Ba0.5FeO3-δ going as low as 11·10-6 1/K. The materials behave as LaMO3 perovskites with small band gaps and Ba acting as acceptors compensated by electron holes and oxygen vacancies. The electrical properties are dominated by p-type conduction with high large polaron mobilities for the Co-rich compositions at low temperatures, shifting towards small polaron mobilities with increasing Fe content. X-ray absorption spectroscopy (XAS) shows that Co is in a high spin state and takes on the main part of the cation oxidation state changes, and that hole states are in orbitals overlapping with the O 2p states, confirming the large polaronic behaviour, while holes on Fe are more localised at the cation. Hydration is more pronounced in inert atmospheres, as hydration of oxygen vacancies is easier than hydrogenation and increases with Fe content, in line with the commonly accepted finding that delocalization of holes disfavours protonation. Fe-rich compositions benefit from lower TCEC and higher hydration and hence expected proton permeability, at the cost of lower electronic conductivity. The surfaces are hydrophobic irrespective of Fe content, suggesting weak chemisorption of the underlaying water layer, possibly giving relatively many available surface sites for oxygen adsorption, but limited surface proton conductance – both of importance to positrodes for operando PCECs.

Layer Resolved Cr Oxidation State Modulation in Epitaxial SrFe0.67Cr0.33O3-δ Thin Films.

Understanding how doping influences physicochemical properties of ABO3 perovskite oxides is critical for tailoring their functionalities. In this study, SrFe0.67Cr0.33O3-δ epitaxial thin films were used to examine the effects of Fe and Cr competition on structure and B-site cation oxidation states. The films exhibit a perovskite-like structure near the film/substrate interface, while a brownmillerite-like structure with horizontal oxygen vacancy channels predominates near the surface. Electron energy loss spectroscopy shows Fe remains Fe3+, while Cr varies from ∼Cr3+ (tetrahedral layers) to ∼Cr4+ (octahedral layers) within brownmillerite phases and becomes ∼Cr4.5+ in perovskite-like phases. Theoretical simulations indicate that Cr-O bond arrangements and the way oxygen vacancies interact with Cr and Fe drive Cr charge disproportionation. High-valent Cr cations introduce additional densities of states near the Fermi level, reducing the optical bandgap from ∼2.0 eV (SrFeO2.5) to ∼1.7 eV (SrFe0.67Cr0.33O3-δ). These findings offer insights into B-site cation doping in the perovskite oxide framework.

An Approach to Estimate the Refractive Index and the Electronic Polarizability of the Ternary Ag2O-B2O3-TeO2 Glasses.

Each of the static properties such as refractive index (n0), cation ( ), and anion ( ) oxide polarizabilities for the ternary 30Ag2O⋅xB2O3⋅(70 - x)TeO2 (30AgBTe) glasses has been predicted theoretically from those of the binary 30Ag2O-70B2O3 and 30Ag2O-70TeO2 glasses. This can be done based on two assumptions: that each of these static properties (n0, , and ) can be considered as an additive property and that ternary 30AgBTe glasses can be treated as a mixture of two binary 30Ag2O-70B2O3 and 30Ag2O-70TeO2 glasses. In addition, n0 values for the ternary 30AgBTe glasses can be predicted in terms of and values for the ternary 30AgBTe glasses, and these later properties can be predicted from that of two binaries like as n0 at first stage. The n0 values obtained by using two methods are exactly the same for the corresponding compositions in the studied glasses, confirming the validity of the two assumptions and the procedure described in the present work. This conclusion is valid for the ternary glasses with a fixed content of either basic former/or modifier oxides for all compositions such as xPbO⋅(40 - x)Sb2O3⋅60B2O3 and 30Ag2O⋅xB2O3⋅(70 - x)TeO2 glasses, respectively.

Enhancing Ballistic Transport and C3–C4 Alcohol Dehydration through Machine Learning-Designed Cationic Graphene Oxide Membranes

Enhancing Ballistic Transport and C₃–C₄ Alcohol Dehydration through Machine Learning-Designed Cationic Graphene Oxide Membranes

Enthalpy of the Cerium (Ce) Chemi-Ionization Reaction and CeO+, CeC+, and CeCO+ Bond Energies Determined by Energy-Resolved Guided Ion Beam Mass Spectrometry Experiments.

Cerium (Ce) oxide, carbide, and carbonyl cation bond energies and the exothermicity of the Ce chemi-ionization (CI) reaction with atomic oxygen were investigated using guided-ion beam tandem mass spectrometry (GIBMS). The kinetic energy dependent product cross sections for reactions of Ce+ with O2, CO, and CO2 and CeO+ with O2, CO, Xe, and Ar were measured using GIBMS. For the reactions of Ce+ with O2 and CO2, CeO+ is formed through an exothermic reaction, whereas CeO+ formation is endothermic in the reaction with CO. This reaction also forms CeC+ and CeCO+ is formed in the reaction of Ce+ with CO2, both in endothermic processes. Reactions of CeO+ with all four gases led to endothermic collision-induced dissociation as well as exchange reactions to form CeO2+ for the O2 and CO reactants. Bond dissociation energies (BDEs) at 0 K were determined through analyses of the kinetic energy dependent cross sections for all endothermic reactions. We determined that the BDEs of CeO+, CeC+, and CeCO+ are 8.46 ± 0.15, 3.93 ± 0.16, and ≥0.25 ± 0.07 eV, respectively, where the CeO+ BDE is a weighted average of 6 independent 0 K threshold measurements. The CeO+ BDE is combined with the ionization energy (IE) of Ce to determine an exothermicity of 2.91 ± 0.15 eV for the Ce + O → CeO+ + e- chemi-ionization reaction. Combined with neutral BDEs from the literature, the thermochemistry determined here also provides IE(CeO) = 5.03 ± 0.12 eV and IE(CeC) = 6.50 ± 0.16 eV. Theoretical calculations for ground and some excited states were performed for CeO+, CeC+, and CeCO+ to provide insight into the bonding and a comparison with the experimentally determined BDEs for each molecule.

Reduction of a two-dimensional crystalline MoO3 monolayer

The atomic structure of MoOx films formed upon a gradual thermal reduction of an ordered MoO3 monolayer on the Pd(100) substrate was explored via surface science characterization techniques and density functional theory (DFT) calculations. Two main reduction stages were identified. First, the initial oxygen excess was gradually eliminated by altering the domain boundary length, orientation, and atomic structure. The films nevertheless remained O-rich, with numerous terminal oxygen atoms (formation of MoO groups), and an elevated work function. Second, multiple ordered O-lean phases were formed, characterized by either very few or no terminal oxygen atoms, and a much smaller surface work function. According to calculations, the positive charging of the Pd substrate stabilizes the oxygen excess during the first stage, but during the second reduction stage, the substrate becomes negatively charged, stabilizing enhanced cation oxidation states. On their basis, the mechanisms underlying the oxygen release from the initial c(2 × 2) domains were disclosed. The experiments showed that the film reduction is perfectly reversible, which highlights the very promising properties of the MoO3/Pd system for heterogeneous catalysis.

Large Scale Production of Lithium and Sodium Based NMC Oxide Cathodes

The ongoing embrace of innovative renewable energy conversion methods, couple with diverse and dynamic energy storage applications, necessitates the adoption of new adaptable process lines in industrial settings [1]. The adopting process line and methods are chosen based on various factors like overall cost, sustainable process, adaptable infrastructure, and pollution standards. Interestingly recent developments in lithium containing high energy dense battery for electric mobility solutions require varied industrial solutions in every other step for adopting the transition ahead. For example, high temperature treatment during large-scale production of lithium like volatile elements containing multi cation oxide battery materials suffer inconsistency in the nominal composition of its final product[2]. Currently, industries producing lithium-based battery materials use scalable techniques like sol-gel / coprecipitation based batch processing[3]. To offset lithium losses or incorporate lithium content, conventional approaches involve the use of complex precursors, excess lithium addition, and subsequent post-processing techniques. However, the conventional two-step process leads to uncontrollable lithium content during large scale production. Hence, in this study, we propose a new methodology based on thermal plasma spray pyrolysis and its optimization for large scale production of lithium and sodium based multi-cation oxide materials. Spray pyrolysis is a robust large scale production process utilized in multitude industries. Conventionally, spray pyrolysis-based techniques are used in industry to achieve relatively simple compound or two step procedures to achieve desired uniform, phase purity, and structures[4-7]. Herein, thermal plasma-based spray pyrolysis utilizes the plasma environment to pyrolyze the precursors of multiple cationic elements before depositing at a shorter distance. Optimization of spray pyrolysis parameters is made such that, lithium content is maintained and multi-cation oxide with phase purity, uniformity, and narrow size distribution is achieved. The advantage of the proposed method lies in adaptability of simpler precursors, cost, and time effectiveness. Thermal plasma-based spray pyrolysis mediated synthesis of uniform Lithium and Manganese rich NMC (Li-NMC) Li1.2MO2 (M = Ni (0.1), Mn (0.6), Co (0.1)) cathode material is attempted and achieved the reported rock salt pattern αNaFeO2 structure without cation mixing in the layered structure. X-ray diffraction results confirm that both Lithium NMC oxide and Sodium NMC oxides resulted in high phase purity. The layered nature of the samples identified from distinct hexagonal doublet (018) / (110) around 65º 2θ. Li-NMC resulted in a capacity of 160 mAh g-1. Optimized synthesis parameters of the thermal plasma spray pyrolysis method resulted in a production yield rate of 5 g min-1. Microscopic examination reveals cuboid shape of nanostructures with an average size of approximately 200 nm and narrow size distribution. Similarly, optimization of production scale parameters for Na-NMC oxide is being carried out.

Induced Anion Redox before Full Oxidation of Ru4+/Ru5+ through Local Configuration Modulation in P2-Na0.67[Mg0.33Ru0.67]O2

The study of anionic redox in layered-oxide cathodes for Na-ion batteries (NIBs) has been extensive, aiming to attain high-energy density. The involvement of Mn4+ or Ru5+ oxidation states is known to be crucial for the anionic O2 −/O− reaction during Na+ de/intercalation. Nevertheless, our findings indicate that anionic redox can activate in Ru-based layered-oxide cathodes prior to complete Ru4+/Ru5+ oxidation. By employing first-principles calculation and experimental techniques, we disclose that additional Na+ deintercalation from P2-Na0.33[Mg0.33Ru0.67]O2 relies on anionic oxidation after extracting 0.33 mol Na+ from P2-Na0.67[Mg0.33Ru0.67]O2, concomitant with cationic oxidation of Ru4+/Ru4.5+. Specifically, only the oxygen adjacent to 2Mg/1Ru is implicated in anionic redox during Na+ de/intercalation, indicating that the Na–O–Mg arrangement in the P2-Na0.33[Mg0.33Ru0.67]O2 structure significantly reduces the thermodynamic stability of anionic redox compared to cationic redox. Through O anionic and Ru cationic reactions, P2-Na0.67[Mg0.33Ru0.67]O2 demonstrates a substantial specific capacity of ∼172 mA h g− 1 and exceptional power capability, facilitated by facile Na+ diffusion and reversible structural changes during charge/discharge. These findings propose an innovative strategy to enhance anionic redox activity by modifying the local oxygen environment, paving the way for high-energy-density cathode materials in NIBs.

Revealing Detailed Cartilage Function Through Nanoparticle Diffusion Imaging: A Computed Tomography & Finite Element Study

The ability of articular cartilage to withstand significant mechanical stresses during activities, such as walking or running, relies on its distinctive structure. Integrating detailed tissue properties into subject-specific biomechanical models is challenging due to the complexity of analyzing these characteristics. This limitation compromises the accuracy of models in replicating cartilage function and impacts predictive capabilities. To address this, methods revealing cartilage function at the constituent-specific level are essential. In this study, we demonstrated that computational modeling derived individual constituent-specific biomechanical properties could be predicted by a novel nanoparticle contrast-enhanced computer tomography (CECT) method. We imaged articular cartilage samples collected from the equine stifle joint (n = 60) using contrast-enhanced micro-computed tomography (µCECT) to determine contrast agents’ intake within the samples, and compared those to cartilage functional properties, derived from a fibril-reinforced poroelastic finite element model. Two distinct imaging techniques were investigated: conventional energy-integrating µCECT employing a cationic tantalum oxide nanoparticle (Ta2O5-cNP) contrast agent and novel photon-counting µCECT utilizing a dual-contrast agent, comprising Ta2O5-cNP and neutral iodixanol. The results demonstrate the capacity to evaluate fibrillar and non-fibrillar functionality of cartilage, along with permeability-affected fluid flow in cartilage. This finding indicates the feasibility of incorporating these specific functional properties into biomechanical computational models, holding potential for personalized approaches to cartilage diagnostics and treatment.

Surface atomic bidirectional migration modulated electrocatalytic activity in Co2MnO4 nanoparticles

Polymetallic cationic spinel-type oxides are increasingly being used as catalysts for oxygen reduction/oxygen evolution reactions (ORR/OER). Here, we have modified the anti-spinel Co2MnO4 using a quenching strategy (CMO-Q) and demonstrated that the bidirectional migration of Co and Mn cations at the tetrahedral/octahedral positions is the essential reason for enhancing the ORR/OER performance. Electrochemical test results show that CMO-Q is better than Co2MnO4, OER initial potential decreased by 100 mV, and ORR current density increased from 4.2 to 7.3 mA cm−2 at 1600 rpm, with more stable CMO-Q-based zinc–air battery performance. Meanwhile, density functional theory calculations confirm that the primary factor contributing to the reduction of distance from the d-band center of Co and Mn to the Fermi level is the conductivity enhancement. This study offers insight into regulating the surface atomic migration and catalytic performance of spinel without compromising its stable structure.

Laser-assembled conductive 3D nanozyme film-based nitrocellulose sensor for real-time detection of H2O2 released from cancer cells

In this work, a nanostructured conductive film possessing nanozyme features was straightforwardly produced via laser-assembling and integrated into complete nitrocellulose sensors; the cellulosic substrate allows to host live cells, while the nanostructured film nanozyme activity ensures the enzyme-free real-time detection of hydrogen peroxide (H2O2) released by the sames. In detail, a highly exfoliated reduced graphene oxide 3D film decorated with naked platinum nanocubes was produced using a CO2-laser plotter via the simultaneous reduction and patterning of graphene oxide and platinum cations; the nanostructured film was integrated into a nitrocellulose substrate and the complete sensor was manufactured using an affordable semi-automatic printing approach. The linear range for the direct H2O2 determination was 0.5–80 μM (R2 = 0.9943), with a limit of detection of 0.2 μM. Live cell measurements were achieved by placing the sensor in the culture medium, ensuring their adhesion on the sensors' surface; two cell lines were used as non-tumorigenic (Vero cells) and tumorigenic (SKBR3 cells) models, respectively. Real-time detection of H2O2 released by cells upon stimulation with phorbol ester was carried out; the nitrocellulose sensor returned on-site and real-time quantitative information on the H2O2 released proving useful sensitivity and selectivity, allowing to distinguish tumorigenic cells. The proposed strategy allows low-cost in-series semi-automatic production of paper-based point-of-care devices using simple benchtop instrumentation, paving the way for the easy and affordable monitoring of the cytopathology state of cancer cells.

High-pressure synthesis of Ruddlesden-Popper nitrides.

Layered perovskites with Ruddlesden-Popper-type structures are fundamentally important for low-dimensional properties, for example, photovoltaic hybrid iodides and superconducting copper oxides. Many such halides and oxides are known, but analogous nitrides are difficult to stabilize due to the high cation oxidation states required to balance the anion charges. Here we report the high-pressure synthesis of three single-layer Ruddlesden-Popper (K2NiF4 type) nitrides-Pr2ReN4, Nd2ReN4 and Ce2TaN4-along with their structural characterization and properties. The R2ReN4 materials (R = Pr and Nd) are metallic, and Nd2ReN4 has a ferromagnetic Nd3+ spin order below 15 K. Thermal decomposition gives R2ReN3 with a Peierls-type distortion and chains of Re-Re multiply bonded dimers. Ce2TaN4 has a structural transition driven by octahedral tilting, with local distortions and canted magnetic Ce3+ order evidencing two-dimensional Ce3+/Ce4+ charge ordering correlations. Our work demonstrates that Ruddlesden-Popper nitrides with varied structural, electronic and magnetic properties can be prepared from high-pressure synthesis, opening the door to related layered nitride materials.

Tunability of domain structure in partially inverse spinels NiAl2O4

Re-arrangement of cationic distribution in partially inverse spinel NiAl2O4 by using chemical pressure perturbation is studied. Structural, impedance and magnetic analysis suggest presence of regions/domains inside the grain/bulk with same lattice arrangement but varying in cationic oxidation state. Perturbing the cationic distribution in the grain via low concentrations of ambivalence substituent rearranges the cationic distribution across these domains within the partially inverse spinel lattice without disturbing the crystal structure. A comprehensive explanation on the origin & tunability of cationic distribution within the partially-inverse lattice is proposed.

Fabrication and mechanical properties of multi-principal cation (Mg,Ti,Cr,Zr,Al,Si) mullite ceramic

Milti-principal cation oxide ceramics with excellent mechanical properties for potential applications in coating materials. A Multi-principal cation mullite (MPCM) ceramic is synthesized with MgO, TiO2, Cr2O3, ZrCl2O·8H2O and Al2O3, SiO2 via solid state reaction at 1600 °C. It is determined that 96.9 % of the sample composition is mullite. MPCM ceramic exhibits higher compressive strength (981 ± 19 MPa) and fracture toughness (3.37 ± 0.05 MPa∙m1/2), the compressive strength has raised by 453 MPa, and the added value of solution strengthening (452 MPa) is gained by using solid-solution strengthening theory. The improvement of compressive strength is mainly due to the solution strengthening effect of the four oxides(Mg, Ti, Zr, Cr), and the improvement of fracture toughness is caused by the grain hindrance during crack propagation. Moreover, its application at the high-temperature resistant coating is verified through experimentation. The interfacial binding force, as an important mechanical property index for ceramics, is researched. In this study, pure mullite powder and MPCM powder are coated onto the refractory TaWNbV alloy matrix by slurry coating method, and the interfacial toughness of the two coatings mingled with the matrix is calculated to be 72.9 and 62.6 J·m−2, respectively. The “shrinking cylinder” model is introduced to interpret the oxidative weight gain mechanism of the two coatings.

An interpretation for the components of 2p 3/2 core level x-ray photoelectron spectra of the cations in some inverse spinel oxides

In an effort to reconcile the various interpretations for the cation components of the 2p 3/2 observed in x-ray photoelectron spectroscopy (XPS) of several spinel oxide materials, the XPS spectra of both spinel alloy nanoparticles and crystalline thin films are compared. We observed that different components of the 2p 3/2 core level XPS spectra, of these inverse spinel thin films, are distinctly surface and bulk weighted, indicating surface-to-bulk core level shifts in the binding energies. Surface-to-bulk core level shifts in binding energies of Ni and Fe 2p 3/2 core levels of NiFe2O4 thin film are observed in angle-resolved XPS. The ratio between surface-weighted components and bulk-weighted components of the Ni and Fe core levels shows appreciable dependency on photoemission angle, with respect to surface normal. XPS showed that the ferrite nanoparticles Ni x Co1−x Fe2O4 (x = 0.2, 0.5, 0.8, 1) resemble the surface of the NiFe2O4 thin film. Surface-to-bulk core level shifts are also observed in CoFe2O4 and NiCo2O4 thin films but not as significantly as in NiFe2O4 thin film. Estimates of surface stoichiometry of some spinel oxide nanoparticles and thin films suggested that the apportionment between cationic species present could be farther from expectations for thin films as compared to what is seen with nanoparticles.

Synergetic effect of both cation and anion doping cobalt oxides on V2C MXene boosting oxygen evolution reaction

In order to enhance the conductivity and catalytic efficiency of non-noble electrocatalyst, an electrocatalysts consisting of ZnCo metallic double oxide with S doping embedded on V2C MXene for oxygen evolution reaction (OER) is synthesized. Cobalt serves as the primary active site, while zinc contributes to improve conductivity owing to its high electronegativity. Sulfur doping plays a crucial role in reducing the energy barrier of rate determining step of OER. The V2C MXene as a substrate can promote conductivity as well, resulting in synergistic effect. The electrocatalyst exhibits a low overpotential of 240 mV at 10 mA cm−2 in alkaline electrolyte, surpassing that of IrO2 commercial electrocatalyst. The potential shows only a minimal ∼5 mV day after 72-h stability test at 20 mA cm−2. The current density at 1.6 V vs RHE is 2 times that of commercial IrO2. Both theoretical calculation and experimental result demonstrate the advantage brought by the incorporation of zinc and sulfur. This work introduces a new idea of synergetic effect in non-noble metallic electrocatalysis.

Revealing the role of calcium ion intercalation of hydrated vanadium oxides for aqueous zinc-ion batteries

Exploring suitable high-capacity V2O5-based cathode materials is essential for the rapid advancement of aqueous zinc ion batteries (ZIBs). However, the typical problem of slow Zn2+ diffusion kinetics has severely limited the feasibility of such materials. In this work, unique hydrated vanadates (CaVO, BaVO) were obtained by intercalation of Ca2+ or Ba2+ into hydrated vanadium pentoxide. In the CaVO//Zn and BaVO//Zn batteries systems, the former delivered up to a 489.8 mAh g−1 discharge specific capacity at 0.1 A g−1. Moreover, the remarkable energy density of 370.07 Wh kg−1 and favorable cycling stability yard outperform BaVO, pure V2O5, and many reported cathodes of similar ionic intercalation compounds. In addition, pseudocapacitance analysis, galvanostatic intermittent titration (GITT) tests, and Trasatti analysis revealed the high capacitance contribution and Zn2+ diffusion coefficient of CaVO, while an in-depth investigation based on EIS elucidated the reasons for the better electrochemical performance of CaVO. Notably, ex-situ XRD, XPS, and TEM tests further demonstrated the Zn2+ insertion/extraction and Zn-storage mechanism that occurred during the cycle in the CaVO//Zn battery system. This work provides new insights into the intercalation of similar divalent cations in vanadium oxides and offers new solutions for designing cathodes for high-capacity aqueous ZIBs.

Titanate-based high-entropy perovskite oxides relaxor ferroelectrics

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.