Perovskite Oxide Materials Research Articles

Nanoscale Design of High-Quality Epitaxial Aurivillius Thin Films

Efforts for the integration of ferroelectric materials in nonvolatile, low energy consuming memories have so far been focused on perovskite oxide materials. Their down-scaling for nanodevices is, h...

Electrical properties of high permittivity epitaxial SrCaTiO3 grown on AlGaN/GaN heterostructures

Epitaxial integration of perovskite oxide materials with GaN has unlocked the potential to improve functionality and performance in high-power RF and power-switching applications. In this work, we demonstrate structural and electrical properties of high dielectric constant Sr1−xCaxTiO3 epitaxial layers grown on AlGaN/GaN/4H-SiC high-electron-mobility transistor structures with compositions ranging from x = 0 to x = 0.53 and oxide film thicknesses ranging from 7 to 126 nm. We show (111) orientation in the SrCaTiO3 (SCTO) thin films using a 1 nm (100) TiO2 buffer layer grown by RF-plasma-assisted oxide molecular beam epitaxy. Current–voltage measurements show up to 5 orders of magnitude reduced leakage with SCTO films when compared to Schottky contacted samples. Capacitance–voltage measurements show minimal hysteresis, an extracted dielectric constant (κ) as high as 290, and a fixed positive interface charge density of 2.38 × 1013 cm−2 at the SCTO/AlGaN interface. The direct integration of the SCTO layer does not significantly affect the two-dimensional electron gas (2DEG) density or the channel mobility with the 2DEG density as a function of SCTO thickness having good agreement with 1D Poisson–Schrödinger simulations. RF characterization of interdigitated capacitors using the SCTO films on unintentionally doped GaN/SiC shows that the films maintain their high κ into microwave frequencies and only exhibit a slight reduction in κ with increased lateral electric fields. These results demonstrate that the integration of a high-κ oxide with GaN can potentially improve electric field management in RF high-electron-mobility transistors and increase the device breakdown voltage without significant degradation to channel transport properties.

Design of Materials for Energy Storage and Conversion in High Temperature Environment

The kinetics and thermodynamics of electrochemical energy storage and conversion technologies such as fuel cells and electrolyzers often times benefit from high temperature operation. For example, the thermodynamic electrical energy requirements for water electrolysis decrease substantially from 1.23 to below 1 volt by increasing the process temperature from ambient conditions to 850 °C. Unfortunately, materials degradation via sintering, crystal structure disproportion to thermodynamically more stable phases, and interfacial reactions also increases exponentially with increasing temperature. Lifetime requirements for energy conversion technologies often times exceed 10 years of usage with no more than 20% degradation.[1] The requirement of high gas/electrode/solid electrolyte interfacial area for large areal current densities repeatedly necessitates the usage of nano to micro structured materials, further acerbating materials degradation. Oftentimes it is much easier to synthesize a promising new electrode or electrolyte material than it is to characterize the long-term stability of a material in the extremely reducing or oxidizing high temperature environments.[2] We have developed experimental methods in conjunction with thermochemical modeling to evaluate the stability of important classes of perovskite and fluorite oxide materials.[3] We have performed thermogravimetric, FT-IR and electrochemical linear sweep voltammetry methods to rapidly determine oxide materials stability under operationally relevant conditions and these results are compared to stability calculations. Generalizations can be made to predict expected materials redox stability based on relatively straightforward chemical bonding principles, known cation coordination environments and more sophisticated computational chemistry methods. Stability determinations of perovskite oxide electrocatalysts for electrochemical oxidative coupling of methane offer an excellent examples of our approach towards evaluation of materials durability under challenging temperature and reducing conditions.[1] A. Hauch, S. D. Ebbesen, S. H. Jensen, and M. Mogensen, “Highly efficient high temperature electrolysis,” J. Mater. Chem., vol. 18, no. 20, pp. 2331–2340, 2008, doi: 10.1039/B718822F.[2] C. Zhu, S. Hou, X. Hu, J. Lu, F. Chen, and K. Xie, “Electrochemical conversion of methane to ethylene in a solid oxide electrolyzer,” Nat. Commun., vol. 10, no. 1, p. 1173, 2019, doi: 10.1038/s41467-019-09083-3.[3] F. H. G. Kannan P. Ramaiyan, Luke H. Denoyer, Angelica Benavidez, “Electrochemical oxidative coupling of methane to produce higher hydrocarbons using Sr2Fe1.5Mo0.5O6-d electrocatalysts,” Submitt. Commun. Chem., 2021.

Electric-field modulated photovoltaic effect of ferroelectric double-perovskite Bi2FeMnO6 films

Ferroelectric perovskite oxide materials for photovoltaics (PV) have received considerable attention for their switchable PV responses and above-bandgap photovoltages as a type of new-generation PV device. Relatively large bandgap and low photocurrent remain major problems for their PV applications. Herein, we report the PV response of ferroelectric double-perovskite Bi2FeMnO6 (BFMO) thin films. It was found that the photocurrent density (Jsc) of a Sn:In2O3 (ITO)/BFMO/SrRuO3 (SRO) thin film device is two orders of magnitude higher than that of BiFeO3, and its power conversion efficiency is about 430 times larger than that of BiFeO3 under AM 1.5G illumination. The built-in electric field near the BFMO/SRO interface, which represents the Schottky contact, leads to the separation of photon-generated carriers. More importantly, the electric poling treatment on the BFMO device can manipulate significantly the magnitude of Jsc, which is independent of the polarization direction. This electric-field modulated PV effect in the poled BFMO device originates from the modulation of the Schottky barrier height at the BFMO/SRO interface. The redistribution of oxygen vacancies after electric poling treatment is mainly responsible for the modulation of the Schottky barrier height.

Surface Defect Engineering on Perovskite Oxides as Efficient Bifunctional Electrocatalysts for Water Splitting.

The design of high-performance and cost-effective electrocatalysts for water splitting is of prime importance for efficient and sustainable hydrogen production. In this work, a surface defect engineering method is developed for optimizing the electrocatalytic activity of perovskite oxides for water electrolysis. A typical ferrite-based perovskite oxide material La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) is used and regulated by selective acid etching. The optimal parameters for the surface treatment are identified. An efficient bifunctional perovskite oxide, denoted LSCF-30, is prepared by selectively corroding the A-site Sr element in the surface region, which is found to not only increase the exposure and decrease the coordination of B-site metals but also effectively modulate the electronic structure of these metals. The crystal lattice of the perovskite bulk is kept constant during surface engineering, which ensures the structural stability of the perovskite catalyst. The findings demonstrate an effective strategy of surface defect engineering in enhancing the performance of perovskite oxide electrocatalysts for water splitting.

Chemical Stability and CO2 Electrolysis Performance of La0.3Sr0.7Fe0.7Cr0.3O3- δ in CO2/CO Environments

LMFCr (M = Sr, Ca) has emerged as a highly promising class of perovskite oxide materials for use as symmetrical electrodes in reversible solid oxide fuel cells (RSOFCs).1 While there are numerous studies on the efficacy of these materials as symmetrical electrodes for SOFCs,1-5 a detailed study on their chemical stability and electrochemical performance as fuel electrodes in CO2/CO environments has not yet been reported. This work aims to address the stability of the Sr analogue of LMFCr, namely, La0.3Sr0.7Fe0.7CrO3-δ (LSFCr), in low pO2 environments consisting of CO2/CO gas mixtures (10-11-10-18 atm) to establish the range of pO2 over which the electrode material is structurally and electrochemically stable. This is relevant under CO2 reduction conditions as the stability limit will define the allowable CO2 utilization in these cells in practice.The chemical and phase stability was studied on LSFCr powders and pellets via XRD, TGA, and SEM in different pO2 atmospheres ranging from pure CO2, CO (balance N2), and 90-70% CO2:10-30% CO containing mixtures. Powdered LSFCr remains structurally stable in 20-100% CO2 (balance N2, pO2 = 10-11 – 10-12 atm) from room temperature to 800 oC without any decomposition. On the other extreme, a reversible decomposition occurs at 800 oC in 30% CO (balance N2, pO2 ~ 10-26 atm) resulting in the formation of a Ruddlesden-Popper phase, Fe nanoparticles (NPs), and some carbon fibers, originating from the Fe NPs. However, this decomposition can be reversed by heat treatment in air at 800 oC. While no evidence for coke formation is obtained in 90-70% CO2:10-30% CO (pO2 = 10-17 – 10-18 atm) mixtures at 800 oC, in 70CO2:30CO, minor impurities of SrCO3 and Fe NPs are observed, with the latter potentially being beneficial to the electrochemical activity of the perovskite.Electrochemical characterization was carried out on symmetrical cells prepared by printing ~25 µm single phase LSFCr electrode layers, with an area of ca. 0.5 cm2, on both sides of a 1” diameter SDC buffered YSZ electrolyte, followed by painting on Au paste as the current collectors. The cells were mounted in an open flanges cell testing setup (Fiaxell, Switzerland) and supplied with 50 mL/min air at the oxygen electrode and 50 mL/min CO2:CO mixtures at the fuel electrode. The performance of full cells was determined in various CO2:CO ratios (Pure CO2, 90:10, and 70:30) at 800 oC via electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and chronoamperometry. Consistent with prior work, symmetrical 2-electrode full cells showed very good electrochemical performance at 800 oC, both in the SOFC and SOEC modes. Furthermore, LSFCr full cells exhibited excellent short-term stability in 15-min potentiostatic stability tests at 1.2-1.5 V, while medium-term potentiostatic tests at 1.1 and 1.2 V showed that LSFCr exhibits exceptional stability during CO2 electrolysis in all gas atmospheres over several 100 hours, with the oxygen electrode facilitating the oxygen evolution reaction (OER) at the same time. These results suggest that LSFCr has the potential to be a very efficient and stable electrode material for symmetrical SOC applications. References (1) Chen, M.; Paulson, S.; Thangadurai, V.; Birss, V. Journal of Power Sources 2013, 236, 68-79.(2) Chen, M.; Paulson, S.; Thangadurai, V.; Birss, V. ECS Transactions 2012, 45, 343-348.(3) Chen, M.; Paulson, S.; Kan, W. H.; Thangadurai, V.; Birss, V. Journal of Materials Chemistry A 2015, 3, 22614-22626.(4) Molero-Sanchez, B.; Addo, P.; Buyukaksoy, A.; Paulson, S.; Birss, V. Faraday Discussions 2015, 182, 159-175.(5) Addo, P. K.; Molero-Sanchez, B.; Chen, M.; Paulson, S.; Birss, V. Fuel Cells 2015, 15, 689-696.

Proton-Assisted Reconstruction of Perovskite Oxides: Toward Improved Electrocatalytic Activity.

Electrocatalysis is indispensable to various emerging energy conversion and storage devices such as fuel cells and water electrolyzers. Owing to their unique physicochemical properties, perovskite oxide materials are one of the most promising water oxidation (OER) catalysts solely comprising earth-abundant elements. Nonetheless, many perovskite oxide catalysts suffer from a number of inherent problems such as the A-site cation segregation on the surface, coarse particles due to agglomeration/sintering, and surface decomposition during catalytic reactions. Besides, the catalytic activity is often incomparable with those of the state-of-the-art catalysts. In this work, we developed a proton-assisted approach to mitigate these common challenges. The protonation via the interaction of oxygen vacancies and water molecules induced the formation of protonic defects and the lattice expansion of the perovskite, leading to the fracture of big particles to yield small nanoparticles. This hydration in an acidic solution also selectively removed the A-site cation segregates and generated a spinel/perovskite heterostructure on the surface. We verified this approach using three typical perovskite OER catalysts including Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF), La0.6Sr0.4Co0.8Fe0.2O3 (LSCF), and La0.75Sr0.25MnO3 (LSM). The processed catalysts showed much improved activity while maintaining their excellent stability, surpassing most of today's OER catalysts based on complex oxides.

Lanthanide based double perovskites: Bifunctional catalysts for oxygen evolution/reduction reactions

In this work, we are reporting the facile synthesis of double perovskite oxide materials LnBa0.5Sr0·5Co1·5Fe0·5O6 (LnBSCF, Ln = Pr, Nd, Sm, and Gd) using citrate-nitrate based sol-gel method. These double perovskite oxide materials exhibit bifunctional catalytic activity for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). The phase formation and structure of the prepared oxides have been determined by powder X-ray diffraction, SEM analysis. Presence of various phases is analyzed and quantified by mean of Le-Bail refinement of XRD profiles. SEM analyses confirm the morphology and composition of prepared catalysts. Electrochemical measurements, e.g. Linear Sweep Voltammetry, Cyclic Voltammetry and Electrochemical Impedance spectroscopy were used to study catalytic performance of prepared catalyst towards both oxygen evolution and oxidation reduction reactions in alkaline solution. Better catalytic performance was obtained in case of double perovskites as compared to parent perovskite for both reactions. Best catalytic performance was observed for Gd based double perovskite.

Reversible Phase Transformations in Novel Ce‐Substituted Perovskite Oxide Composites for Solar Thermochemical Redox Splitting of CO2

AbstractThermochemical splitting of CO2 and H2O via two‐step metal oxide redox cycles offers a promising approach to produce solar fuels. Perovskite‐type oxides with the general formula ABO3 have recently gained attention as an attractive redox material alternative to the state‐of‐the‐art ceria, due to their high structural and thermodynamic tunability. A novel Ce‐substituted lanthanum strontium manganite perovskite‐oxide composite, La3+0.48Sr2+0.52(Ce4+0.06Mn3+0.79)O2.55 (LSC25M75) is introduced, aiming to bridge the gap between ceria and perovskite oxide‐based materials by overcoming their individual thermodynamic constraints. Thermochemical CO2 splitting redox cyclability of LSC25M75 evaluated with a thermogravimetric analyzer and an infrared furnace reactor over 100 consecutive redox cycles demonstrates a twofold higher conversion extent to CO than one of the best Mn‐based perovskite oxides, La0.60Sr0.40MnO3. Based on complementary in situ high temperature neutron, synchrotron X‐ray, and electron diffraction experiments, unprecedented structural and mechanistic insight is obtained into thermochemical perovskite oxide materials. A novel CO2 splitting reaction mechanism is presented, involving reversible temperature induced phase transitions from the n = 1 Ruddlesden–Popper phase (Sr1.10La0.64Ce0.26)MnO3.88 (I4/mmm, K2NiF4‐type) at reduction temperature (1350 °C) to the n = 2 Ruddlesden–Popper phase (Sr2.60La0.22Ce0.18)Mn2O6.6 (I4/mmm, Sr3Ti2O7‐type) at re‐oxidation temperature (1000 °C) after the CO2 splitting step.

Machine learning aided design of perovskite oxide materials for photocatalytic water splitting

Suffering from the inefficient traditional trial-and-error methods and the huge searching space filled by millions of candidates, discovering new perovskite visible photocatalysts with higher hydrogen production rate (RH2) still remains a challenge in the field of photocatalytic water splitting (PWS). Herein, we established structural-property models targeted to RH2 and the proper bandgap (Eg) via machine learning (ML) technology to accelerate the discovery of efficient perovskite photocatalysts for PWS. The Pearson correlation coefficients (R) of leave-one-out cross validation (LOOCV) were adopted to compare the performances of different algorithms including gradient boosting regression (GBR), support vector regression (SVR), backpropagation artificial neural network (BPANN), and random forest (RF). It was found that the BPANN model showed the highest R values from LOOCV and testing data of 0.9897 and 0.9740 for RH2, while the GBR model had the best values of 0.9290 and 0.9207 for Eg. Furtherly, 14 potential PWS perovskite candidates were screened out from 30,000 ABO3-type perovskite structures under the criteria of structural stability, Eg, conduction band energy, valence band energy and RH2. The average RH2 of these 14 perovskites is 6.4% higher than the highest value in the training data set. Moreover, the online web servers were developed to share our prediction models, which could be accessible in http://materials-data-mining.com/ocpmdm/material_api/ahfga3d9puqlknig (Eg prediction) and http://materials-data-mining.com/ocpmdm/material_api/i0ucuyn3wsd14940 (RH2 prediction).

Synthesis and characterization of single pervoskite Ba(Ni1/3Mn1/3W1/3)O3

Single perovskite oxide materials have very attractive behaviors like multiferroics, piezoelectricity as well as dielectric and ferromagnetic properties. Owing to these properties, perovskites can be used widely in many applications, such as ferroelectric and magnetic random access memories, transducers, sensors, actuators and also in magneto-electric spintronic devices. In this research, a novel and lead-free multiferroic material Ba(Ni1/3Mn1/3W1/3)O3 pervoskite is chemically prepared by cost effectual solid-state reaction method by taking oxides of Ba, Ni, Mn and W. X-ray diffraction, SEM, EDAX and the dielectric behaviors (like dielectric_permittivity, tanδ, dielectric_modulus, impedance and electrical_conductivity) of the above composites are analyzed.

Matching conflicting oxidation conditions and strain accommodation in perovskite epitaxial thin-film ferroelectric varactors

Perovskite oxide materials of the general chemical formula ABO3 are a rich playground for epitaxial stacks of different functional layers for novel device applications. In the example of a tunable metal–insulator–metal ferroelectric varactor (tunable capacitor) made from the highest conducting perovskite SrMoO3 as an electrode and the tunable dielectric Ba0.5Sr0.5TiO3 (BST), we show how the extremely conflicting oxidation potentials can be conciliated in a fully functional heterostructure. Controlling the growth kinetics by the substrate temperature, oxygen pressure, and oxidation time, the formation of the non-conducting Mo6+ states can be effectively suppressed and the BST cation stoichiometry can be tuned. The cumulative impact of the cation nonstoichiometry, epitaxial strain, and oxygen deficiency in the BST films leads to the expansion of their c-axis lattice parameter via the formation of point defects. The dielectric permittivity of 440, the high tunability of 3.5, and the quality factor of 50 are achieved for the varactors at the frequency of 1 GHz. It turns out that the varactor performance is anti-correlated to the tetragonal lattice distortion of BST, which itself is interrelated to the oxidation conditions. The mechanism of the leakage current through oxygen deficient BST layers of the varactors is analyzed within the combined scenarios of the space-charge limited current and Poole–Frenkel field-assisted emission from traps. The achieved high capacitance per unit area of 0.04 pF/μm2 and moderate leakage currents of 0.025 μA/pF make these varactors suitable for applications in microwave microelectronic devices.

Electrochemical performance of ANiO3 (A= La, Ce) perovskite oxide material and its device performance for supercapattery application

The novel CeNiO3 (CNO) nanobelts are synthesized via co-precipitation method for supercapattery application and the performance of CeNiO3 is compared with distorted sphere like LaNiO3 (LNO). Crystal structural, morphological and surface chemical analysis of CNO electrodes are characterized using XRD, FESEM, HRTEM and XPS analysis. Possessing higher surface area of CNO over LNO enables the superior electrochemical performance of CNO as a supercapattery electrode material. Cyclic voltammetry (CV), Galvanostatic charge discharge (GCD) and electrochemical impedance spectroscopy (EIS) are used to determine the electrochemical performance of the electroactive material. The CeNiO3 as both anode and cathode materials is used for fabricating a symmetric two electrode supercapattery system to examine its real-life application. The cell delivered a maximum energy density of 27 Wh kg−1 at a power density of 826 W kg−1. Furthermore, the CNO materials exhibit an excellent cyclic stability of 92% for 5000 cycles at current density of 10 Ag−1, demanded the new material evolution in the energy field.

Effect of bismuth (Bi3+) substitution on structural, optical, dielectric and magnetic nature of La2CoMnO6 double perovskite

Double perovskite oxide materials represented as A2BB′O6 have attracted a great attention due to their diverse electrical, magnetic and structural properties. In this report, we discuss synthesis, structural, optical, magnetic and electric nature of the double perovskite manganites of the type La2−xBixCoMnO6 [x = 0.0, 0.1, 0.2]. These solid-state reaction route products with x = 0.0, 0.1 were found monoclinic structured (P 1 21 / n 1) confirmed from the X-ray diffraction data analysis, whereas the sample with x = 0.2 has acquired a new structure confirmed to be cubic (Fm-3 m) with another phase corresponding to Bi2O3 crystallized in monoclinic structure acquiring space groups P 1 21 / c 1. The results of XRD data analysis were re-verified via Rietveld refinement. The phase formation was further verified via Raman and FTIR spectral studies. The samples were investigated for composition and morphology also. The optical bandgap was determined (≈ 1 eV) from the diffuse reflectance UV–Vis spectra. Temperature-dependent dielectric constant and dielectric loss was investigated in the temperature range of 320–90 K at various constant values of applied ac field and the results were exceptionally good. Electrical (dc) resistivity exploiting four-probe technique with and without magnetic field infer the samples are semiconducting in nature. Room temperature magnetic measurement reveals the samples exhibit low magnetic moment which shows linear behaviour in both forward and reverse field values.

Fe–O terminated LaFeO3 perovskite oxide surface for low temperature toluene oxidation

The surface termination of catalyst is vital to heterogeneous catalytic reaction process. Inactive A-site cations exposed over the perovskite oxide materials would limit the surface activity of studied samples. In this work, the surface composed of more Fe–O termination was synthesized over the LaFeO3 perovskite oxide and it shows performance superiority than more La–O exposed samples. Combined with the characterization results, exposure of more Fe–O termination would help boost the oxygen mobility and enhance the reducibility of LaFeO3 perovskite with higher hydrogen consumption (0.088 mmol/g) than that of untreated LaFeO3 sample (0.033 mmol/g). Based on the DFT calculation and XPS analyzation, exposure of the Fe–O termination surface would decrease the formation energy of oxygen vacancy and hence boost the oxygen cycle process, which would accelerate the redox process in return. Furthermore, more Fe–O exposed surfaces would cause the effective performance enhancement for the catalytic oxidation of toluene. After 5 h surface treatment, T50 and T90 of LFO-5 are 255.9 °C and 277.3 °C, much lower than that of untreated sample, which are 309.7 °C and 332.8 °C, correspondingly. In the meantime, the surface treated sample possess relative good stability under 20 h test. This work would benefit for the practical application and provide a better understanding to the potential of perovskite oxides.

UV-Stable and Highly Efficient Perovskite Solar Cells by Employing Wide Band gap NaTaO3 as an Electron-Transporting Layer.

Organic-inorganic halide perovskite solar cells (PSCs) still suffer from stability issues which are caused by possible erosions from moisture, ultraviolet (UV) light, heat, and so forth. An electron-transporting layer (ETL), that is, TiO2, is a key component for state-of-the-art PSCs. However, UV-caused desorption of O2- in TiO2 would accelerate the degradation of PSCs. Herein, we explored perovskite oxide, NaTaO3, for the first time as an alternative ETL in PSCs. NaTaO3 as an ETL can effectively avoid the damage from UV irradiation, inhibit the degradation of the perovskite layer, and improve the overall stability of the PSC. PSCs fabricated with NaTaO3 yielded a power conversion efficiency (PCE) of 21.07% with a retention of more than 80% of this initial PCE after 240 min UV irradiation in air while the reference device with a PCE of 20.16% can only retain about 53% of its initial PCE after the same testing condition. The developed stable perovskite oxide material of NaTaO3 provides the diversification of electron-selective contact for highly efficient and stable PSCs.

Anomalous magnetic behaviors of double perovskite R2CrFeO6 (R = rare earth elements) predicted by first-principles calculations

Double perovskite oxide materials have been attracting people’s attention for they are good candidates to present large magnetization by either ferromagnetic or ferrimagnetic interactions. Recently, the long debated magnetic ground state of double perovskite La2CrFeO6 is confirmed by experiments to be ferrimagnetic, which is different from the predictions of the Goodenough-Kanamori rules. In order to gain a fundamental understanding of these anomalous magnetic behaviors of double perovskites R2CrFeO6 (R = La, Ce, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, Tm and Y), systematic researches are in need. In this paper, we calculated the structural and magnetic behaviors of double perovskites R2CrFeO6 by first-principles calculations. The effect of the rare-earth ionic radius on crystal structural parameters (e.g., lattice parameters, monoclinic angles, rhombohedral angles, Cr–O–Fe bond angles and tilting angles) and magnetic ordering temperature are obtained.Our calculations indicate that the magnetic moments of Fe and Cr in R2CrFeO6 oxides present anti-parallel alignment, i.e., R2CrFeO6 are ferrimagnetic. For all the studied R2CrFeO6 oxides except La2CrFeO6 and Y2CrFeO6, the magnetic ordering temperature decrease linearly with the increase of the rare earth ionic radius, which is different from the previously-observed “general” magnetic behaviors in various rare earth based perovskites such as R2NiMnO6 and R2CoMnO6. Moreover, it is worth noting that besides generating tilting angles and thus affecting magnetic properties, rare earth ions can also affect the magnetic exchange coupling of the double perovskite R2CrFeO6 systems in other ways. Our work can provide comprehensive information for understanding the anomalous magnetic properties of double perovskite R2CrFeO6 and would be helpful for the development of new multiferroic materials.

Transfer of Epitaxial SrTiO3 Nanothick Layers Using Water-Soluble Sacrificial Perovskite Oxides.

The integration of functional thin film materials with adaptable properties is essential for the development of new paradigms in information technology. Among them, complex oxides with perovskite structures have huge potential based on the particularly vast diversity of physical properties. Here, we demonstrate the possibility of transferring perovskite oxide materials like SrTiO3 onto a silicon substrate using an environmentally friendly process at the nanoscale by means of a water-soluble perovskite sacrificial layer, SrVO3. Based on in situ monitoring atomic force microscopy and photoemission studies, we reveal that the dissolution is initiated from a strontium-rich phase at the extreme surface of SrVO3. The nanothick SrTiO3-transferred layer onto silicon presents appropriate morphology and monocrystalline quality, providing a proof of concept for the integration and development of all-perovskite-oxide electronics or "oxitronics" onto any Si-based substrate.

Insight of novel layered perovskite PrSrMn2O5+δ: A neutron powder diffraction study

Neutron diffraction is very important to characterizing complex oxide materials, especially for the light element position and occupancy. In this study, a new layered perovskite oxide material, PrSrMn2O5+δ, was prepared by the solid-state reaction method and characterized by using X-ray and neutron powder diffraction, scanning electron microscopy and thermogravimetric analysis. X-ray diffraction data showed that the material adopted orthorhombic symmetry and Rietveld refinement of the neutron diffraction data gave accurate unit cell parameters (a = 3.8907 (1) Å, b = 3.8227 (1) Å, and c = 7.6846 (2) Å, atomic positions and space group (Pmmm)). Scanning electron microscopy showed a porous and interlinked microstructure. Thermogravimetric analysis exhibited two-stage weight losses up to 1000 °C from room temperature, indicating a good amount of oxygen losses and high material stability.

Cationic Vacancy Mediated Conductivity and Charge Transport in Non‐Stoichiometric Epitaxial BaTi0.75Nb0.25O3 Films

High‐quality epitaxial BaTi0.75Nb0.25O3 (BNTO) films with controllable Ba/(Nb + Ti) ratio are fabricated by pulsed laser deposition, and a systematic investigation on their conductivity and charge transport behaviors is carried out. The Ba/(Nb + Ti) ratio can be significantly regulated from 0.96 to 0.53 when the laser fluence varies from 0.5 to 2.0 J cm−2. Resistivity–temperature measurements indicate that all the BNTO films exhibit semiconductor transport behaviors at temperatures from 50 to 400 K. Their conductivity increases monotonically with the decrease in the Ba/(Nb + Ti) ratio. For films with a high Ba/(Nb + Ti) ratio of 0.96, the small polaron (SP) hopping dominates in the temperature range from 200 to 400 K. Nevertheless, the SP hopping can only be observed at temperatures ranging from 285 to 400 K for the films with a Ba/(Nb + Ti) ratio of 0.53, implying that the reduction of Ba vacancy is favorable for SP hopping transport in BNTO films, especially at low temperature. Hall effect measurements indicate a higher carrier mobility observed in the films with lower Ba/(Nb + Ti) ratio, revealing the promotion of carrier mobility by Ba vacancy. The work reveals that cationic vacancy plays an important role in the conductivity and charge transport mechanisms in perovskite oxide materials, such as BNTO films.