In this work, we conducted a detailed analysis of the types of mechanisms by which vortex lines interact with pinning centers generated in YBa2Cu3O7-d (Y123) single crystals by annealing in high oxygen pressure and Mo-substitution. Our analysis is based on the properties of these centers influencing the pinning force. Based on the previously obtained results on the dependence of the critical current density, jc, on the magnetic field, jc(H), we determined jc as a function of temperature, jc(T), for different H, which we used to answer the question of which pinning mechanism, Sl or STc, dominates in Y123 single crystals. Our results differ both quantitatively and qualitatively from those previously reported, which we explain by understanding the types of pinning centers generated in studied materials. Our results provide a better understanding of the phenomena leading to significant increases in critical currents in Y123 and thus allow for better prediction of pinning centers that operate effectively under desired magnetic fields and temperatures.

We assessed four exchange-correlation functionals (LDA CA-PZ, GGA parametrized by PBE, PBEsol, and WC) in predicting the lattice parameters of SrTi1-xMnxO3 perovskites, assuming cubic structures. Predictions were verified using X-ray diffraction (XRD) for Mn content of x = 0.0, 0.1, 0.2, 0.3, 0.5, 1.0, confirming cubic symmetry and a linear decrease in lattice parameters with increasing Mn. PBEsol, and WC demonstrated the highest precision (deviations <0.20 %). Additionally, bulk moduli were calculated using the same functionals and verified with the experimental bulk modulus of SrTiO3 (183 +/- 2 GPa, Pulse-Echo method). The predicted bulk moduli exhibited a slow, linear increase with increasing Mn. The best correspondence with the experimental bulk modulus was achieved by PBEsol and WC (deviations <0.7 %). These findings highlight the reliability of PBEsol and WC functionals for accurately modeling structural properties of SrTi1-xMnxO3 perovskites, having better precision than commonly employed LDA and PBE functionals.

Specific heat studies of the Sr_1-xBa_xMn_1-yTi_yO_3 polycrystalline samples performed by the relaxation and DSC methods over the temperature range 2 - 450 K are reported. Anomalies accompanying the antiferromagnetic-paramagnetic and ferroelectric-paraelectric phase transitions were measured and analyzed. The system studied is a promising multiferroic material of the 2^nd type, in which a strong coupling between the magnetic and electric systems can be related to the fact that the same Mn^4+ ions are responsible for the two orderings. Analysis of the anomaly at the magnetic transition was done by using the advanced theory of the continuous transitions, in which the presence of higher order terms in the free energy is considered, and the parameters of the critical behavior of the system were estimated. It was found that, despite of earlier predictions, the transition loses the continuous character and can become the 1^st order process for the Ti-containing samples. The anomalies accompanying the 1^st order high-temperature ferroelectric transition were found to be hardly visible by using both techniques, which was ascribed to a wide temperature range of coexistence of the dielectric and ferroelectric phases.

The synthesis and structural properties of polycrystallinecubicand hexagonal Sr0.4Ba0.6Mn0.94Ti0.06O3-& delta; have been investigated usinga combination of in situ neutron diffraction and thermogravimetricanalysis. The experiments were conceived to replicate and explainkey synthesis processes involving switching between different reducingand oxidizing atmospheres designed to transform a hexagonal phaseinto an oxygen-deficient cubic perovskite phase in which Mn ions arein their trivalent oxidation state. Hydrogen reduction of the hexagonalphase first produces a heavily oxygen-deficient hexagonal phase precedingto full decomposition of the material. Remarkable reversible propertiesof the parent hexagonal structure are observed with the phase recoveredwithin minutes by reoxidation of the material after it was decomposedin hydrogen-containing atmospheres. The partial substitution of largeBa ions at the Sr sites enhances the strains and creates wide channels,enabling the rapid oxidation of the oxygen-deficient cubic phase.The fast oxygen intake results in a phase separation between oxygen-richand oxygen-poor phases with no evidence for any vacancy-ordered superstructuresas those previously seen in the parent Ba- and Ti-free SrMnO3-& delta; system.

La1.5Ba1.5Cu3O7 +/-delta (LBCu) complex oxide is evaluated as a Co-free candidate air electrode material for reversible Solid Oxide Cells (rSOC). LBCu is structurally and thermomechanically compatible with La0.8Sr0.2Ga0.8Mg0.2O3-delta (LSGM) electrolyte, maintains the layered (tripled along the c-axis) perovskite-related crystal structure at high temperatures, and shows reduced chemical expansion with the faster elongation ongoing perpendicular to the a-b plane. Its total thermal expansion is found to be moderate comparing to the Co-based perovskites. The onset temperature of the oxygen release from the material is low, ca. 300 degrees C in air, however, up to 800 degrees C the average oxidation state of copper remains above +2 in the oxidative atmospheres. The total electrical conductivity of LBCu correlates with the oxygen content, with the maximum of about 55-75 S cm(-1) at ca. 350 degrees C in air. Functional LBCu air electrodes can be manufactured at temperatures as low as 750-800 degrees C, with exceptionally low (for Co-free material) polarization resistance values of 0.019 Omega cm(2) at 750 degrees C, 0.041 Omega cm(2) at 700 degrees C, and 0.090 Omega cm(2) at 650 degrees C. Relatively high power output, ca. 162 mW cm(-2) at 600 degrees C, and above 458 mW cm(-2) at 750 degrees C is obtained for the laboratory-scale LSGM-supported cell.

It is documented that the mean radius (r) over bar of rare-earth cations occupying Y1-xRx sublattice in Y1-xRxMnO3+delta hexagonal oxides plays a decisive role in terms of thermodynamics and kinetics of reactivity of the materials with oxygen, and consequently, influences strongly the oxygen storage performance in thermal swing processes conducted in oxygen and air. Y1-xRxMnO3+delta samples with designed (r) over bar being close to the critical one, at the border of stability between hexagonal- and perovskite-type phases, can reversibly incorporate/release significant amounts of oxygen in pure O 2 or air atmospheres, at the moderate temperatures on the order of 200-300 degrees C. Characteristic temperatures of oxidation and reduction are dependent on (r) over bar, therefore, it is possible to adjust conditions of the temperature swing operation by the chemical doping in Y1-xRxMnO3+delta with larger rare-earth elements. Crucial from a practical point of view, an increase of the oxidation temperature in such compounds greatly enhances the speed of the oxidation process (20 degrees C increase can reduce half-time of oxidation twice), which is found to be the limiting factor concerning the performance. Based on the comprehensive studies of the physicochemical properties of Y1-xRxMnO3+delta, the optimized Y0.95Pr0.05MnO3+delta composition is proposed, doped only with a small amount of more expensive praseodymium. The material exhibits excellent oxygen storage-related properties and is able for the effective production of oxygen in air by the thermal swing process, utilizing medium-/low-temperature industrial waste heat. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Combinatorial substrate epitaxy (CSE) was used to study the orientation relationships (ORs) and polytypic stability of AEMnO(3) (AE = Ca, Sr) thin films grown on polycrystalline SrMnO3 and SrTiO3 substrates. SrMnO3 films with the stable four-layered hexagonal (4H) and metastable three-layered cubic (3C) structures were also grown on (111) and (100) SrTiO3 single crystal substrates, respectively. Electron backscatter diffraction data were used to determine the following ORs, which hold true regardless of the substrate surface orientation: (001)[100]4HSrMnO3||(001)[100]4HSrMnO3, (111)[11 over bar 0]3CCaMnO3||(001)[100]4HSrMnO3, and (001)[100]4HSrMnO3||(111)[11 over bar 0]3CSrTiO3. These are all simply the eutactic OR, which aligns the eutactic planes and directions; its ubiquity indicates that the interface energy is generally lower for the eutactic OR than for all other possible ORs. 3C SrMnO3 was found to grow only on very near (100) 3C SrTiO3 grains. This narrow range of epitaxial stabilization suggests that the penalties of higher interfacial and/or strain energies between polytypic perovskites adopting the eutactic OR are not significant enough to overcome the volumetric formation energy of the stable phase in these growth conditions, except for very special orientations.

Hexagonal Y 1− x R x MnO 3+ δ (R: other than Y rare earth elements) oxides have been recently introduced as promising oxygen storage materials that can be utilized in the temperature swing processes for the oxygen separation and air enrichment. In the present work, the average and local structures of Tb- and Ce-substituted Y 0.7 Tb 0.15 Ce 0.15 MnO 3+ δ and Y 0.6 Tb 0.2 Ce 0.2 MnO 3+ δ materials were studied, and their oxygen storage-related properties have been evaluated. The fully oxidized samples show the presence of a significant amount of the highly oxygen-loaded the so-called Hex3 phase, attaining an average oxygen content of δ ≈ 0.41 for both compositions. Extensive studies of the temperature swing process conducted in air and N 2 over the temperature range of 180–360 °C revealed large and reversible oxygen content changes taking place with only a small temperature differences and the high dependence on the oxygen partial pressure. Significant for practical performance, the highest reported for this class of compounds, oxygen storage capacity of 1900 μmol O g −1 in air was obtained for the optimized materials and swing process. In the combined temperature–oxygen partial pressure swing process, the oxygen storage capacity of 1200 μmol O g −1 was achieved.

High Cu content perovskite-type LaNi1-xCuxO3-delta oxides are evaluated as alternative air electrode materials for Solid Oxide Cells. Auto-combustion synthesis allowed to obtain fine oxide powders up to a Cu content of x = 0.75 under ambient pressure. Investigations of the crystal structure, oxygen deficiency, chemical and thermal stability, as well as transport properties reveal satisfactory characteristics, with high total electrical conductivity and high concentration of oxygen vacancies at elevated temperatures. LaNi1-xCuxO3-delta-based electrode layers show low polarization resistance values in La0.8Sr0.2Ga0.8Mg0.2O3-delta-based symmetrical cells. The lowest values for Cu-rich compositions at 800 degrees C are 0.056 U cm(-2) for LaNi0.5Cu0.5O3-delta and 0.054 U cm(-2) for LaNi0.25Cu0.75O3-delta with La0.2Ce0.8O3-delta buffer layer. For the reversible cell with LaNi0.5Cu0.5O3-delta air electrode, approx. 870 mW cm(-2) power density output at 900 degrees C is obtained when fueled with wet H-2, as well as over 3 A cm(-2) current density at 2 V in the electrolysis mode. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Muliferroic materials are characterized by two or more primary ferroic orders: ferroelectric, ferromagnetic and ferroelastic. In multiferroics the coupling occurs between the magnetic (ferromagnetic or antiferromagnetic) and electric (ferroelectric) subsystems. This enables control of the dielectric polarization P by a magnetic field H and the manipulation of magnetization M by an electric field E, allowing design of a wide range of novel electronic devices for various sensing, memory, logical, energy, biomedical and other applications. I describe here our efforts to develop new class of single-phase muliferroic materials where a single element, the manganese, is responsible for both the ferroelectric and magnetic properties, which guarantees strong coupling which is necessary for practical applications.

Responding to the rapidly increasing demand for efficient energy usage and increased speed and functionality of electronic and spintronic devices, multiferroic oxides have recently emerged as key materials capable of tackling this multifaceted challenge. In this paper, we describe the development of single-site manganese-based multiferroic perovskite materials with modest amounts of nonmagnetic Ti substituted at the magnetic Mn site in Sr1- x Ba x Mn1- y Ti y O3 (SBMTO). Significantly enhanced properties were achieved with ferroelectric-type structural transition temperatures boosted to ∼430K. Ferroelectric distortions with large spontaneous polarization values of ∼30μC/cm2, derived from a point charge model, are similar in magnitude to those of the prototypical nonmagnetic BaTiO3. Temperature dependence of the system's properties was investigated by synchrotron x-ray powder diffraction and neutron powder diffraction at ambient and high pressures. Various relationships were determined between the structural and magnetic properties, Ba and Ti contents, and T N and T C. Most importantly, our results demonstrate the large coupling between the magnetic and ferroelectric order parameters and the wide tunability of this coupling by slight variations of the material's stoichiometry.

Belonging to the not fully explored REBaCo2-xMnxO5+delta system, a series of REBaCoMnO5+delta (RE: selected rare earth elements) oxides having perovskite-type structure is synthesized and studied in terms of their structural properties, oxygen content, stability, thermal expansion, and transport properties. Impact of RE3+ on physicochemical properties of the compounds is derived, with smaller cations causing a decrease of the unit cell volume, lowering of the total oxygen content and thermal expansion, but also suppressing electrical conductivity. It is shown that a proper chemical modification enables to successfully utilize REBaCoMnO5+delta in applications, in which redox processes associated with oxygen reduction/oxidation and transport determine the effectiveness of the working material. In particular, NdBaCoMnO5+delta (with larger Nd3+) shows good chemical stability in relation to Ce0.8Gd0.2O2-delta and La0.8Sr0.2Ga0.8Mg0.2O3-delta solid electrolytes and moderate thermal expansion, 20.04(4).10(-6) K-1 in 300-900 degrees C. In symmetrical configuration with La0.8Sr0.2Ga0.8Mg0.2O3-delta electrolyte its cathodic polarization resistance is found to be only 0.036 Omega cm(2) at 900 degrees C, making it an excellent candidate cathode for solid oxide fuel cells. At the same time, YBaCoMnO5+delta (with small and cheap Y3+) delivers reversible oxygen storage capacity surpassing 3.4 wt % during the oxygen partial pressure swing process between air and 5 vol % H-2 in Ar at 500 degrees C.

SmBaCo0.5Mn1.5O5+delta oxide with Sm-Ba cation-ordered perovskite-type structure is synthesized and examined in relation to whole RBaCo0.5Mn1.5O5+delta series (R: selected rare earth elements). Presence of Sm and 3:1 ratio of Mn to Co allows to balance physicochemical properties of the composition, with moderate thermal expansion coefficient value of 18.70(1).10(-6) K-1 in 300-900 degrees C range, high concentration of disordered oxygen vacancies in 600-900 degrees C range (delta = 0.16 at 900 degrees C), and good transport properties with electrical conductivity reaching 33 S cm(-1) at 900 degrees C in air. Consequently, the compound enables to manufacture catalytically-active cathode, with good electrochemical performance measured for the electrolyte-supported laboratory-scale solid oxide fuel cell with Ni-Gd1.9Ce0.1O2-delta vertical bar La0.4Ce0.6O2-delta vertical bar La0.8Sr0.2Ga0.8Mg0.2O3-delta vertical bar SmBaCo0.5Mn1.5O5+delta configuration, for which 1060 mW cm(-2) power density is observed at 900 degrees C. Furthermore, the tested symmetrical SmBaCo0.5Mn1.5O5+delta vertical bar La0.8Sr0.2Ga0.8Mg0.2O3-delta vertical bar SmBaCo0.5Mn1.5O5+delta cell delivers 377 mW cm(-2) power density at 850 degrees C, which is a promising result. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

The oxygen storage capacity, oxygen exchange kinetics, structure and thermodynamic stability were studied for hexagonal Y0.7Tb0.3MnO3+δ in oxygen and air to assess its applicability for oxygen separation from air by a temperature-swing adsorption process.

It is shown that appropriately doped Cu-based perovskite-type oxides exhibit high catalytic activity toward the oxygen reduction reaction at high temperatures, making them suitable candidates for the air electrodes for solid oxide fuel cells.

Kamal Chapagain ,1,* Dennis E. Brown,1 Stanislaw Kolesnik,1 Saul Lapidus,2 Bianca Haberl,3 Jamie Molaison,3 Chuanlong Lin,4,† Curtis Kenney-Benson,5 Changyong Park,5 Jaroslaw Pietosa,6 Ewa Markiewicz,7 Bartlomiej Andrzejewski,7 Jeffrey W. Lynn,8 Stephan Rosenkranz,9 Bogdan Dabrowski,6 and Omar Chmaissem1,9 1Department of Physics, Northern Illinois University, DeKalb, Illinois 60115, USA 2X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, USA 3Neutron Scattering Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA 4Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015, USA 5HPCAT, X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, USA 6Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02668 Warsaw, Poland 7Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, PL-60179 Poznań, Poland 8NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102, USA 9Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, USA

Due to outstanding room temperature electron mobility, the wide-gap perovskite semiconductor BaSnO3 is of high current interest. Although n doping with Sb and O vacancies has been reported, most work has focused solely on La doping. Here we report bulk single crystals of Ba1-xRxSnO3_(delta) with R = La, Pr, and Nd, as well as unintentionally doped BaSn0(3)_(delta), thus exploring new rare earth (magnetic) dopants in addition to O vacancy doping. Consistent with recent results on epitaxial films, O vacancies are shown capable of generating mid-10(19) cm(-3) Hall electron densities, with single crystal mobilities similar to 100-150 cm(2) V-1 s(-1). Despite apparent solubility limits below similar to 0.5 at. %, Pr and Nd are also shown to be effective n dopants, yielding Hall electron densities >1 x 10(20) cm(-3), and ambient and low temperature mobilities up to 175 and 430 cm(2) V-1 s(-1), respectively. In contrast to the La-doped case, clear paramagnetism occurs with Pr and Nd doping, allowing for direct estimates of dopant concentrations for quantitative comparison with Hall densities. We show that dopant and Hall densities can be approximately reconciled, but only after accounting for O vacancy doping. Specific heat measurements were also performed, confirming the BaSnO3 Debye temperature, and revealing electronic contributions roughly consistent with reported effective masses. Interestingly, and likely related to crystalline electric field effects, Pr-doped BaSnO3 exhibits large deviations from simple Curie-Weiss susceptibility, and a pronounced Schottky anomaly, which we analyze in detail. These results provide significant insight into doping in BaSnO3, establishing new rare earth magnetic dopants, clarifying the role of O vacancies, and determining dopant concentrations and solubility limits.