HIGH-TEMPERATURE REDOX BEHAVIOUR OF DOUBLE PEROVSKITE Ba2CuWO6

The rock-salt ordered double perovskite Ba2CuWO6 phase was synthesized and unit cell parameters were calculated by the Rietveld method in the frameworks of tetragonal structure with I4/mmm space group. The equilibrium oxygen content was measured by TG in the air and the reducing atmosphere.The authors appreciate the support of this work within the government assignment № AAAA-A19-119110190048-7

Defect equilibrium in PrBaCo2O5+δ at elevated temperatures

A defect equilibrium model for PrBaCo2O5+δ is suggested based on oxygen non-stoichiometry data. The model includes reactions of oxygen exchange and charge disproportionation of Co3+ cations. The respective equilibrium constants, enthalpies and entropies for the reactions entering the model are obtained from the fitting of the experimental data for oxygen non-stoichiometry. The enthalpies of oxidation Co2+→ Co3+ and Co3+→Co4+ are found to be equal to 115±9 kJ mol-1 and 45±4 kJ mol-1, respectively. The obtained equilibrium constants were used in order to calculate variations in concentration of cobalt species with non-stoichiometry, temperature and oxygen pressure. © 2013 Elsevier Inc

The effect of processing conditions on the dielectric properties of doped calcium lanthanum nickelate

The influence of thermal and thermobaric (TBT) effects on the structure, microstructure, and dielectric properties of ceramics based on solid solutions of the La1.8Ca0.2Ni0.8M0.2O4+δ (M = Co, Cu) composition was studied. TBT treatment of the samples leads to a change in the grain morphology of ceramics and an increase in the dielectric constant compared to its value only after heat treatment. The change in the anisotropy of the coordination (La,Ca)O9 and (Ni,M)O6 polyhedra after TBT contributed to interlayer polarization in the crystal structure of La1.8Ca0.2Ni0.8M0.2O4+δ

SYNTHESIS FEATURES AND DETERMINATION OF OXYGEN CONTENT IN DOUBLE PEROVSKITE-LIKE MANGANITES OF COMPOSITION LnBaMn2O6-Δ (LN = Nd, Sm)

The complex oxides were synthesized by precursor combustion in 3 steps. The oxygen content and the value of the oxygen capacity were determined by a conjunction of teragravim-etry with coulometric and iodometric titration methods. The ordered manganites were found to possess highest oxygen capacity.Работа выполнена при финансовой поддержке РНФ №19-79-10147

AB Initio Estimations of Transport Properties of Solid Oxide Molybdates

This work is aimed at comprehensive theoretical study of Sr2MMoO6 molybdates with M = Ti, V, Cr, Mn, Fe, Co, Ni. It is shown that the experimentally observed variations of electronic conductivity in these compounds can be reasonably explained with the help of DFT calculations.Работа выполнена при поддержке Российского фонда фундаментальных исследований (РФФИ) в рамках проекта №19-79-10147

Influence of the Cationic Distribution of the B-Site of La(MnFeCoNiCu)O3-δ High-Entropy Oxides on the Crystal Structure and Properties

High-entropy perovskites La(MnFeCoNiCu)O3–δ are obtained via combustion of glyc-erol-nitrate precursors and consequent annealing at 1100 °C. Most of the samples are single-phase with different symmetric types within the perovskite-like crystal structure. The cationic distribution over sintered sample

Nonlinear optics and light localization in periodic photonic lattices

We review the recent developments in the field of photonic lattices emphasizing their unique properties for controlling linear and nonlinear propagation of light. We draw some important links between optical lattices and photonic crystals pointing towards practical applications in optical communications and computing, beam shaping, and bio-sensing.Comment: to appear in Journal of Nonlinear Optical Physics & Materials (JNOPM

ION TRANSPORT IN HIGHLY NONSTOICHIOMETRIC OXIDES WITH PEROVSKITE-LIKE STRUCTURE

Solid solutions with nominal composition Pr1-xYxBaCo2-yAlyO6-δ where x = 0, 0.1 and y = 0, 0.1 were synthesized, phase purity of the samples obtained was confirmed by XRD analysis. Cobaltites’ equilibrium oxygen content was determined via combination of coulometric titration and thermogravimetry. Thermal expansion of Pr1-xYxBaCo2-yAlyO6-δ oxides was studied with the help of dilatometry. Oxygen permeability was measured in a specially equipped device. Theoretical model was proposed and used for explanation of the data obtained

Phase Instability, Oxygen Desorption and Related Properties in Cu-Based Perovskites Modified by Highly Charged Cations

The rock-salt ordered A2CuWO6 (A = Sr, Ba) with I4/m space group and disordered SrCu0.5M0.5O3−δ (M = Ta, Nb) with Pm3m space group perovskites were successfully obtained via a solid-state reaction route. Heat treatment of Ba2CuWO6 over 900 °C in air leads to phase decomposition to the barium tungstate and copper oxide. Thermogravimetric measurements reveal the strong stoichiometric oxygen content and specific oxygen capacity (ΔWo) exceeding 2.5% for Ba2CuWO6. At the same time, oxygen content reveals Cu3+ content in SrCu0.5Ta0.5O3−δ. Under the following reoxidation of Ba2CuWO6, step-like behavior in weight changes was observed, corresponding to possible Cu+ ion formation at 900 °C; in contrast, no similar effect was detected for M5+ cations. The yellow color of Ba2CuWO6 enables to measure the band gap 2.59 eV. SrCu0.5Ta0.5O3−δ due to high oxygen valance concentration has a low thermal conductivity 1.28 W·m−1·K−1 in the temperature range 25–400 °C

Reassessment of thermochemical energy storage in perovskite-like manganites at comparative studies of RP SrCa3Mn3O10-d vs. orthorhombic Sr0.25Ca0.75MnO3-d

The structural stability, thermal expansion, oxygen exchange thermodynamics, and thermochemical storage (TCS) capacity of perovskite-like Sr0.25Ca0.75MnO3-δ and Ruddlesden-Popper SrCa3Mn3O10-δ manganites are studied by the combined use of experimental techniques, thermodynamic modeling of the defect formation reactions, and energy calculations utilizing density functional theory (DFT). It is argued that conservative estimates of the storage capacity can be made by the use of the Dulong-Petit limit for high-temperature heat capacity and oxygen partial enthalpy independent of both temperature and oxygen content. The respectively recalculated literature data and the obtained results show that the thermodynamic limit for the TCS capacity (~800 kJ/kg) of Sr0.25Ca0.75MnO3-δ is one of the highest at thermal cycling within the oxygen partial pressure range of 10 −4–0.21 atm. At the same time, the storage capacity of SrCa3Mn3O10-δ achieves only about 600 kJ/kg. The TCS cycling tests demonstrate the stability of SrCa3Mn3O10-δ while a decline in the energy storage capacity is observed for Sr0.25Ca0.75MnO3-δ. According to the EDX analysis, this effect may reflect surface degradation of Sr0.25Ca0.75MnO3-δ. The energy storage capacities of SrCa3Mn3O10-δ and Sr0.25Ca0.75MnO3-δ decrease to 510 and 560 kJ/kg, respectively, because of the rather sluggish reduction kinetics. It is concluded that further improvement of manganites as energy storage materials can be achieved using new doping strategies.This work was carried out under support of the state programs № АААА-А19-119031890026-6 and № АААА-А19-119110190048-7. Part of the DFT calculations were performed on the URAN cluster at the Institute of Mathematics and Mechanics, UB RAS.Peer reviewe