Dual nature of high-temperature electronic transport in layered perovskite-like cobaltites: exhaustive consideration of experimental features observed

Consistent interpretation of isotope and chemical oxygen exchange relaxation kinetics in SrFe0.85Mo0.15O3-δ ferrite

This paper is devoted to the study of phase composition and kinetic and thermodynamic characteristics of Mo-doped strontium ferrite SrFe0.85Mo0.15O3-δ (SFM15) under oxygen-conducting membrane working conditions. Single-phase SFM15 with a cubic Pm3̄m structure was synthesized using a ceramic method. It was shown that the molybdenum introduction stabilizes the perovskite cubic structure over a wide range of oxygen pressures and temperatures, preventing the bulk phase transition at high temperatures. Oxygen exchange constants, diffusion coefficients and activation energy of oxygen exchange were obtained using oxygen relaxation and isotopic exchange techniques, and the obtained values are consistent with known literature data. It was shown that the surface reaction rates obtained using chemical and tracer relaxation methods are quantitatively comparable with each other, despite significantly different experimental conditions. This result not only confirms the reliability of the data obtained by independent methods, but also allows one to expand the area of physical conditions for studying the kinetics of oxygen transfer where another method has technical or methodological limitations.

Unusual enhancement of high-temperature electronic transport in PrBaCo2O6-δ under Ga doping: reasons and consequences

Solid oxide PrBaCo_1.8Ga_0.2O_6-δ (PBCG) is synthesized using a glycerol-nitrate route. XRD and SEM techniques are utilized in order to confirm the structural and microstructural composition of the attained ceramics. The high-temperature electrical conductivity and thermopower of the sintered PBCG sample are measured in a wide range of external conditions. It is shown that Ga doping results in ∼30% increase of conduction properties. The observed peculiarity is interpreted in terms of a recently proposed electronic transport model. It is argued that the respective enhancement of conductivity originates from the combined increase of polaron hopping frequencies along with a decline of carriers' effective mass in the metallic subsystem of PBCG.