ABO3 Structure Research Articles

Study of the physical properties of BiFeO3 films obtained by RF sputtering using a homemade target

Ferroelectric materials have attracted significant attention in recent decades because they can be used in various electronic devices. BiFeO3 (BFO) has a perovskite-type ABO3 structure with antiferromagnetic and ferroelectric properties and a band gap within the visible light range, making it a promising candidate for use in sensors and solar cells. In this study, BiFeO3 thin films were grown by radio frequency (RF) sputtering using a homemade target and sintered at different times to evaluate the influence of sintering time on their physical properties. Its physical properties were evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. These results revealed that all films maintained a perovskite-like structure with rhombohedral and bismuth-rich secondary phases (Bi2O2.33). Atomic force microscopy (AFM) and piezoresponse force micrography (PFM) images depicted the impact of sintering time on surface roughness and ferroelectric domain reorientation. The optical properties, such as n, k, and the band gap of all samples, were obtained using reflection-transmission spectroscopy. The photoresponse under dark, visible and UV illumination were evaluated on BFO films grown over glass-FTO substrate.

Defect Control of Donor Doping on Dielectric Ceramics to Improve the Colossal Permittivity and Temperature Stability

As the demand for miniaturization of electronic devices increases, ceramics with an ABO3 structure require further improvement of the dielectric constant with high permittivity. In the present work, Ba1−1.5xBixTiO3 (BB100xT, x = 0.0025, 0.005, 0.0075, 0.01) ceramics were prepared via a solid-state reaction process. The effect of Bi doping on dielectric properties of lead-free relaxor ferroelectric BaTiO3-based ceramics was studied. The results showed that both colossal permittivity (37,174) and a temperature stability of TCC ≤ ±15% (−27–141 °C) were achieved in BB100xT ceramics at x = 0.5%. The A-site donor doping produces A-site vacancies, a larger space for Ti4+, and fluctuation of the component, which is partially responsible for the high permittivity and responsible for the temperature stability. Meanwhile, the contribution of defect dipoles, and IBLC and SBLC effects to polarization leads to the colossal permittivity. The formation of a liquid phase during sintering promotes mass transfer when the doping content is higher than 0.5%. This work benefits the exploration of novel multilayer ceramic capacitors with colossal permittivity and temperature stability via defect engineering.

Porous hollow sphere structure PrFeO3 as an efficient sensing material for n-butanol detection

N-butanol is a harmful volatile gas, so creating an appropriate n-butanol sensor is critical for preserving human health and the manufacturing environment. In contrast to single metal oxide semiconductors, multicomponent metal oxides, especially perovskite ternary metal oxides with the ABO3 structure, exhibit significant potential for development owing to their precise structures and diverse physicochemical properties. In this paper, three-dimensional porous hollow spheres PrFeO3 were synthesized by combining air annealing and hydrothermal techniques. The crystal structure, surface composition, chemical state, and morphology of PrFeO3 materials were evaluated using several kinds of characterization approaches. The gas sensitivity of PrFeO3 materials was also thoroughly explored. The results show that at the optimal working temperature of 280 ℃, the PrFeO3 material excels in n-butanol gas sensing, with a response of 85 for 100 ppm n-butanol. Additionally, the sensor demonstrates high selectivity for n-butanol gases, low concentration detection capability, outstanding repeatability, rapid reaction recovery time (18 s/13 s), long-term stability, and exceptional reproducibility. The unique morphology and high oxygen vacancy content of PrFeO3 provide numerous active sites on its surface, promoting the adsorption and desorption of n-butanol gas molecules and enhancing its gas-sensitive properties.

Enhanced electromagnetic wave absorption of La0.8Ca0.2Fe1-xMnxO3 boosted by lattice distortion and double-exchange

Perovskite LaFeO3 with ABO3 structure is regarded as a potential candidate in electromagnetic wave absorption, considering its unique dielectric-magnetic coupling loss mechanism. However, the limited attenuation ability of pristine LaFeO3 restricts its further application. In this work, the dual doping strategy is carried out to improve the dielectric and magnetic loss capacity. Ca and Mn dual doped La0.8Ca0.2Fe1-xMnxO3 are prepared by spray pyrolysis method. The minimum reflection loss (RLmin) of La0.8Ca0.2Fe0.2Mn0.8O3 reaches −52.3 dB with an effective absorption bandwidth (EAB) of 3.92 GHz at the fitting thickness of 2.08 mm. The enhancement of the dielectric loss mainly originates from strengthened dipole polarization induced by the Jahn-Teller distortion which is caused by Ca and Mn double doping. The magnetic loss can be attributed to the improvement of double-exchange between Fe3+ –O2- -Mn3+ and Mn3+ –O2- -Mn4+ owing to the introduction of Mn. This work provides new insights into regulating the electromagnetic wave absorption performance of perovskite.

Surface ferromagnetism of lead-free ferroelectric bismuth sodium titanate materials

The role of complex surface defect on the magnetic at the (110) surface of bismuth sodium titanate (Bi0.5Na0.5TiO3) was discussed based on the first-principles calculation. The first-principle calculations for various types of surface defects exhibited the existence of magnetic moments for selected chemical and position defects. Specifically, Na and Bi vacancies induced large magnetic moments of 0.52 µB/f.u and 0.50 µB/f.u, respectively, which were larger than that of Ti vacancies of 0.01 µB/f.u. Interestingly, oxygen vacancies did not induce local magnetic moments. Furthermore, significant magnetic moments of 0.50 µB/f.u and 0.49 µB/f.u were obtained for Na and Bi interstitial defects, while the local magnetic moments were slightly achieved around 0.03 µB/f.u and 0.04 µB/f.u for Ti and O interstitial defects, respectively. Anti-site defects between Bi and Na at A-site in perovskite ABO3 structure exhibited magnetic moments of 0.55 µB/f.u for Na anti-site at Bi-site and 0.39 µB/f.u for Bi anti-site at Na-site. Interestingly, anti-site defects between the A-site and B-site in perovskite ABO3 structure resulted in larger magnetic moments, with values of 0.57 µB/f.u and 0.53 µB/f.u obtained for Ti anti-site defects at the Bi-site and Na-site, respectively. Additionally, magnetic moments of 0.50 µB/f.u and 0.54 µB/f.u were achieved for Bi and Na anti-site defects at the Ti-site, respectively. We expected that our work further contributed to the understanding of the role of surface defects in the magnetism of Bi0.5Na0.5TiO3 materials in integrating ferromagnetic properties into lead-free ferroelectric materials for smart electronic device applications.

All-Perovskite Multicomponent Nanocrystal Superlattices.

Nanocrystal superlattices (NC SLs) have long been sought as promising metamaterials, with nanoscale-engineered properties arising from collective and synergistic effects among the constituent building blocks. Lead halide perovskite (LHP) NCs come across as outstanding candidates for SL design, as they demonstrate collective light emission, known as superfluorescence, in single- and multicomponent SLs. Thus far, LHP NCs have only been assembled in single-component SLs or coassembled with dielectric NC building blocks acting solely as spacers between luminescent NCs. Here, we report the formation of multicomponent LHP NC-only SLs, i.e., using only CsPbBr3 NCs of different sizes as building blocks. The structural diversity of the obtained SLs encompasses the ABO6, ABO3, and NaCl structure types, all of which contain orientationally and positionally locked NCs. For the selected model system, the ABO6-type SL, we observed efficient NC coupling and Förster-like energy transfer from strongly confined 5.3 nm CsPbBr3 NCs to weakly confined 17.6 nm CsPbBr3 NCs, along with characteristic superfluorescence features at cryogenic temperatures. Spatiotemporal exciton dynamics measurements reveal that binary SLs exhibit enhanced exciton diffusivity compared to single-component NC assemblies across the entire temperature range (from 5 to 298 K). The observed coherent and incoherent NC coupling and controllable excitonic transport within the solid NC SLs hold promise for applications in quantum optoelectronic devices.

Metal Oxides Derived from Perovskite or Spinel for the Selective Hydrogenation of α,β‐Unsaturated Aldehydes: A Mini–Review

AbstractMixed metal oxides with perovskite ABO3 or spinel AB2O4 structure can provide uniformly and highly dispersed metal oxides, which can be adopted as catalyst supports, as catalysts directly or as catalysts after reduction. When they are used as catalyst supports, the spatial isolation of A‐site ions with B‐site ions not only makes these ions highly dispersed, but also enhances the intimate contact with the active components supported on them, leading to electron transfer or synergistic effect to promote the catalytic ability. After reduction, highly dispersed A/B nanoparticles supported on BOx/AOx can be achieved for the relevant applications. Herein, recent developments in the liquid–phase selective hydrogenation of α,β‐unsaturated aldehydes, with metal oxides derived from perovskite or spinel as supports or catalyst precursors, were summarized.

Flame Spray Pyrolysis Synthesis of Vo-Rich Nano-SrTiO3-x.

Engineering of oxygen vacancies (Vo) in nanomaterials allows diligent control of their physicochemical properties. SrTiO3 possesses the typical ABO3 structure and has attracted considerable attention among the titanates due to its chemical stability and its high conduction band energy. This has resulted in its extensive use in photocatalytic energy-related processes, among others. Herein, we introduce the use of Flame Spray Pyrolysis (FSP); an industrial and scalable process to produce Vo-rich SrTiO3 perovskites. We present two types of Anoxic Flame Spray Pyrolysis (A-FSP) technologies using CH4 gas as a reducing source: Radial A-FSP (RA-FSP); and Axial A-FSP (AA-FSP). These are used for the control engineering of oxygen vacancies in the SrTiO3-x nanolattice. Based on X-ray photoelectron spectroscopy, Raman and thermogravimetry-differential thermal analysis, we discuss the role and the amount of the Vos in the so-produced nano-SrTiO3-x, correlating the properties of the nanolattice and energy-band structure of the SrTiO3-x. The present work further corroborates the versatility of FSP as a synthetic process and the potential future application of this process to engineer photocatalysts with oxygen vacancies in quantities that can be measured in kilograms.

Investigating the Photovoltaic Performance in ABO3 Structures via the Nonlinear Bond Model for an Arbitrary Incoming Light Polarization.

ABO3 structures commonly known as perovskite are of high importance in advanced material science due to their interesting optical properties. Applications range from tunable band gaps, high absorption coefficients, and versatile electronic properties, making them ideal for solar cells to light-emitting diodes and even photodetectors. In this work, we present, for the first time, a nonlinear phenomenological bond model analysis of second harmonic generation (SHG) in tetragonal ABO3 with arbitrary input light polarization. We study the material symmetry and explore the strength of the nonlinear generalized third-rank tensorial elements, which can be exploited to produce a high SHG response if the incoming light polarization is correctly selected. We found that the calculated SHG intensity profile aligns well with existing experimental data. Additionally, as the incoming light polarization varies, we observed a smooth shift in the SHG intensity peak along with changes in the number of peaks. These observations confirm the results from existing rotational anisotropy SHG experiments. In addition, we show how spatial dispersion can contribute to the total SHG intensity. Our work highlights the possibility of studying relatively complex structures, such as ABO3, with minimal fitting parameters due to the power of the effective bond vector structure, enabling the introduction of an effective SHG hyperpolarizability rather than a full evaluation of the irreducible SHG tensor by group theoretical analysis. Such a simplification may well lead to a better understanding of the nonlinear properties in these classes of material and, in turn, can improve our understanding of the photovoltaic performance in ABO3 structures.

Visualizing sintering process and electrical properties of SnO2 doped K0.48Na0.52NbO3 piezoelectric ceramics

In this study, the conventional solid-state sintering of lead-free (1−x)K0.48Na0.52NbO3-xSnO2 piezoelectric green bodies was analysed using thermal imaging and longitudinal/transverse shrinking. The phase structure, fracture morphology, densification, permittivity, ferroelectricity, piezoelectricity, and domain-switching activation energy were investigated with increasing SnO2 content (x). Sn4+ first occupied the A site in the ABO3 structure and then substituted the B site with increasing x. This resulted in various contents of defect dipoles and oxygen vacancies, which were mainly responsible for the different ferroelectricity and piezoelectricity values. The permittivity and domain-switching activation energy were significantly affected by the local compositional disorder or fluctuation. Moreover, the influences of phase, densification, fine grain size, and domain wall on the electrical properties are also discussed. The optimum electrical properties, with Pr = 34.7 μC/cm2, d33 = 294 pC/N, and TC = 337 °C were determined for x = 0.30 mol%. This study provides a specific explanation and reference for the various electrical properties of lead-free piezoelectric ceramics.

Photoluminescence properties of Ba0.7Sr0.3TiO3:Sm3+ modified K0.5Na0.5NbO3 perovskite oxide ceramics

Ba0.7Sr0.3TiO3:Sm3+ modified KxNa(1-x)NbO3 ceramics with perovskite-type structure were synthesized via solid state sintering method. Sm3+ ions doping was designed for substituting both A and B sites in the ABO3 structure, Sm3+ doped Ba0.7Sr0.3TiO3 (Ba0.7Sr0.3TiO3:Sm3+) oxide precursor powders with the chemical formula of Ba0.7Sr0.3-xSmx(Ti1-xSmx)O3 (x=0.005 ， 0.015 ， 0.025) were synthesized. Combined Ba0.7Sr0.3TiO3:Sm3+ with K0.5Na0.5NbO3, the perovskite-type solid solution composite ceramics were fabricated via solid phase sintering method. X-Ray diffraction was used for investigating the phase structure of the precursor powders and luminescent composite ceramics. The photoluminescence properties of the Sm3+ ions in the Ba0.7Sr0.3TiO3-K0.5Na0.5NbO3 composite ceramic materials were systematically investigated by exploring the effects of composition of the composites, excitation wavelength and temperature on photoluminescence.

Electron beam-induced brownmillerite–perovskite phase transition in La0.6Sr0.4CoO3− δ

The electron beam, during high-resolution transmission electron microscopy, was employed to induce a phase transition in La0.6Sr0.4CoO2.5 (LSC) from a brownmillerite ordering to an oxygen deficient perovskite structure. Prior to irradiation, a strongly alternating out-of-plane lattice parameter was observed, reflecting electrostatic interactions between AO and BO/BO2 planes in the brownmillerite ordering. During electron beam irradiation for one hour, the oxygen vacancy ordering vanished gradually, and a uniform cubic perovskite structure prevailed. To exclude beam-induced heating effects, in situ heating experiments were performed, revealing a stable brownmillerite ordering in the relevant temperature range (up to at least 500 °C). Thus, we conclude that the phase transition is caused by knock-on processes that affect oxygen vacancies in terms of a transition from structural vacancies toward extremely high concentrations of randomly distributed point defects in the ABO3 structure.

Novel co-doped protonic conductors BaLa1.9Sr0.1In1.95M0.05O6.925 with layered perovskite structure

Active development of electrochemical devices such as proton-conducting fuel cells and electrolyzers should ensure sustainable environmental development. An electrolyte material of a hydrogen-powered electrochemical device must satisfy a number of requirements, including high proton conductivity. Layered perovskites are a promising class of proton-conducting electrolytes. The cationic co-doping method has been successfully applied to well-known proton conductors with the classical perovskite structure ABO3. However, the data on the application of this method to layered perovskites are limited. In this work, the bilayer perovskites BaLa1.9Sr0.1In1.95M0.05O6.925 (M = Mg2+, Ca2+) were obtained and investigated for the first time. Cationic co-doping increases oxygen-ion and proton conductivity values.

PbZrO3‐Based Anti‐Ferroelectric Thin Films for High‐Performance Energy Storage: A Review

AbstractEnergy storage capacitors occupy a large proportion in the pulse power equipment, and they play an important role nowadays. In recent years, anti‐ferroelectric materials have attracted increasing attention of researchers due to their high energy storage density. Compared with the lead‐free anti‐ferroelectric materials, PbZrO3 (PZ)‐based anti‐ferroelectric films are defined as promising electrical energy storage devices for pulsed power systems due to their ultrahigh energy storage density. During the past decade, numerous studies have been reported to develop high‐performance PZ‐based anti‐ferroelectric thin films for electrical energy storage applications. This review focuses on the recent progress of PZ‐based anti‐ferroelectric films for energy storage, and provides various ways, such as element modification (replacing of one element in the ABO3 structure by another element), composite materials (adding secondary phase into PZ films to form composite films), and process improvement (such as the tuning of different bottom electrodes), to improve their energy storage density. Finally, the problems and future development directions of the PZ‐based films are raised.

B-site cation synergy in Mn doped LaCoO3 for enhanced electrocatalysts for electrochemical reduction of nitrate

Electroreduction of nitrate is a promising strategy that has gained more attention in current years. Perovskites are promising catalysts for electroreduction of nitrate due to its special ABO3 structure, which makes it possible to regulate its physical and chemical properties to achieve better nitrate removal efficiency. In this study, we doped Mn cation into the B-site of LaCoO3 and evaluated its performance for electroreduction of nitrate. After appropriate portion of Mn was doped in LaCoO3, optimized Co2+/Co3+ ratio as well as larger surface area and pore structures were acquired. The optimized doped materials LaMn0.6Co0.4O3, which achieved 41.92 % higher nitrate removal efficiency than that of LaCoO3, was in good function under different operating conditions of initial NO3– concentration, cathode potential and pH value and remained outstanding stability after ten consecutive cycles of reaction. Depending on the valence change of Co and Mn of cathode before and after electrocatalysis, we deduced that doped Mn cation not only affected the valence of Co cation but also activated adsorbed oxygen to offer electron and accelerated electron transfer. Generally, this study provided a novel thread to reveal synergism of doped metal cations of perovskites in electroreduction of nitrate.

Magnetic and electrical properties of LaCoO3 - LaNiO3 epitaxial thin films on LaAlO3 substrate

The mixed transition metal oxide thin films having ABO3 structure noticed numerous applications due to their robust electrical and magnetic properties. Among them, Lanthanum cobalt oxide considered as promising material since it exhibits excellent properties as catalyst and mixed ionic-electronic conductors. In this manuscript, we successfully deposited the epitaxial lanthanum cobalt oxide (LaCoO3) and lanthanum nickel oxide (LaNiO3) thin films on single crystal lanthanum aluminate (LAO) substrate. Individual and bilayer thin films are grown by pulsed laser deposition (PLD). X-ray diffraction pattern reveals the epitaxial nature and phase purity of the deposited thin films. Morphological images has been captured using field-emission scanning electron microscopy (FE-SEM). The electrical and magnetic properties of individual and bilayer LaCoO3/LaNiO3 thin films are measured using four-probe and physical property measurement system (PPMS) respectively. There is a clear ferromagnetic transition in LaCoO3 thin film observed at 85 K. Surprisingly, the bilayer of LaNiO3/LaCoO3 thin films exhibited enhanced magnetic properties compared with individual LaCoO3 or LaNiO3 thin films. The bilayer films revealed the high magnetization and less coercive filed (3.76 emu/cm3, 2215H) respectively. These results given an idea that bilayer LaCoO3/LaNiO3 thin films are capable to exhibit enhanced multifunctional properties.

Advancements in Liquid Jet Technology and X-ray Spectroscopy for Understanding Energy Conversion Materials during Operation.

ConspectusWater splitting is intensively studied for sustainable and effective energy storage in green/alternative energy harvesting-storage-release cycles. In this work, we present our recent developments for combining liquid jet microtechnology with different types of soft X-ray spectroscopy at high-flux X-ray sources, in particular developed for studying the oxygen evolution reaction (OER). We are particularly interested in the development of in situ photon-in/photon-out techniques, such as in situ resonant inelastic X-ray scattering (RIXS) techniques at high-repetition-frequency X-ray sources, pointing toward operando capabilities. The pilot catalytic systems we use are perovskites having the general structure ABO3 with lanthanides or group II elements at the A sites and transition metals at the B sites. Depending on the chemical substitutions of ABO3, their catalytic activity for OER can be tuned by varying the composition.In this work, we present our in situ RIXS studies of the manganese L-edge of perovskites during OER. We have developed various X-ray spectroscopy approaches like transmission zone plate-, reflection zone plate-, and grating-based emission spectroscopy techniques. Combined with tunable incident X-ray energies, we yield complementary information about changing (inverse) X-ray absorption features of the perovskites, allowing us to deduce element- and oxidation-state-specific chemical monitoring of the catalyst. Adding liquid jet technology, we monitor element- and oxidation-state-specific interactions of the catalyst with water adsorbate during OER. By comparing the different technical spectroscopy approaches combined with high-repetition-frequency experiments at synchrotrons and free-electron lasers, we conclude that the combination of liquid jet with low-resolution zone-plate-based X-ray spectroscopy is sufficient for element- and oxidation-state-specific chemical monitoring during OER and easy to handle.For an in-depth study of OER mechanisms, however, including the characterization of catalyst-water adsorbate in terms of their charge transfer properties and especially valence intermediates formed during OER, high-resolution spectroscopy tools based on a combination of liquid jets with gratings bear bigger potential since they allow resolution of otherwise-overlapping X-ray spectroscopy transitions. Common for all of these experimental approaches is the conclusion that without the versatile developments of liquid jets and liquid beam technologies, elaborate experiments such as high-repetition experiments at high-flux X-ray sources (like synchrotrons or free-electron lasers) would hardly be possible. Such experiments allow sample refreshment for every single X-ray shot for repetition frequencies of up to 5 MHz, so that it is possible (a) to study X-ray-radiation-sensitive samples and also (b) to utilize novel types of flux-hungry X-ray spectroscopy tools like photon-in/photon-out X-ray spectroscopy to study the OER.

Machine-learning prediction of thermal expansion coefficient for perovskite oxides with experimental validation.

Perovskite oxides have been of high-interest and relatively well studied over the last 20 years due to their various applications, specifically for solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs). One of the key properties for a perovskite to perform well as a component in SOFCs, SOECs, and other high-temperature applications is its thermal expansion coefficient (TEC). The use of machine learning (ML) to predict material properties has greatly increased over the years and has proven to be a very useful tool for materials screening. The process of synthesizing and testing perovskite oxides is laborious and costly, and the use of physics-based models is often highly computationally expensive. Due to the amount of elements able to be accommodated in the ABO3 structure and the ability for crystallographic mixing in both the A and B-sites, there are a massive amount of possible ABO3 perovskites. In this paper, a ML model for the prediction of the TECs of AA'BB'O3 perovskites is produced and applied to millions of potential compositions resulting in reliable TEC predictions for 150 451 of the compositions.

LaCo1-x-yCuxTiyO3/KIT-6 perovskites: synthesis and catalytic behavior in syngas conversion to higher alcohols.

Highly dispersed LaCo1-x-yCuxTiyO3/KIT-6 perovskites were synthesized by the citrate method with inert mesoporous KIT-6 addition. The KIT-6 matrix was removed by dissolution in 7% NaOH aqueous solution. The dispersity of perovskites probably varies depending on the largest cation and its content at the B position of the perovskite ABO3 structure. The CoS=23+/CoS=03+ ratio increases with the increase in copper content and in the presence of Ti4+. It may be explained by the compensation of the distortion of the perovskite structure. The maximum syngas conversion is achieved at nCo/nCu = 7/3. At a higher copper content, the activity of the samples decreases due to the formation of large copper particles (up to 40 nm) in the course of the reduction. The selectivity for alcohols increases with an increase in the proportion of copper and reaches maximum values at a ratio of nCo/nCu close to 1. The distribution of alcohols is the same for all samples, except for LaCo0.35Cu0.35Ti0.3O3/KIT-6. It can be assumed that the synthesis of alcohols proceeds on bimetallic CoCu particles 3 nm in size and cobalt particles 4-6 nm in size, most likely enriched with copper on the surface.

Revealing Resistive Switching Mechanism in CaFeOx Perovskite System with Electroforming-Free and Reset Voltage-Controlled Multilevel Resistance Characteristics.

Recently, perovskite (PV) oxides with ABO3 structures have attracted considerable interest from scientists owing to their functionality. In this study, CaFeOx is introduced to reveal the resistive switching properties and mechanism of oxygen vacancy transition in PV and brownmillerite (BM) structures. BM-CaFeO2.5 is grown on an Nb-STO conductive substrate epitaxially. CaFeOx exhibits excellent endurance and reliability. In addition, the CaFeOx also demonstrates an electroforming-free characteristic and multilevel resistance properties. To construct the switching mechanism, high-resolution transmission electron microscopy is used to observe the topotactic phase change in CaFeOx . In addition, scanning TEM and electron energy loss spectroscopy show the structural evolution and valence state variation of CaFeOx after the switching behavior. This study not only reveals the switching mechanism of CaFeOx , but also providesa PV oxide option for the dielectric material in resistive random-access memory (RRAM) devices.