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An A-site deficient perovskite with metallic Ni in exsolution, Ni–Sr0.9Mo0.9O3−δ, has been prepared, characterized and tested as an anode material in intermediate-temperature solid-oxide fuel cells (IT-SOFCs). It was obtained by reduction of a Ni-containing scheelite oxide, from which Ni is segregated to the surface as metal nanoparticles with average size of 30–35 nm, as demonstrated by high-resolution transmission electron microscopy (HR-TEM). An in situ neutron powder diffraction (NPD) study of the Sr0.9Mo0.9O3−δ matrix shows an oxygen deficient cubic perovskite, defined in the Pm3¯m space group; no crystalline transitions were detected in the tested temperature range up to 850 °C. Morphological observations using a scanning electron microscope (SEM) and pore size determinations by Hg porosimetry showed a highly porous material with macropores. The electrical conductivity gave a maximum value of 215 S cm−1 at 850 °C. A suitable thermal expansion coefficient, with values close to that of the electrolyte, showed no abrupt changes in its slope. Polarization curves and electrochemical impedance spectra (EIS) under open circuit were investigated. In single-cell tests, the materials generated outstanding output powers close to 1025 mW cm−2 at 850 °C using pure H2 as fuel. All these features make this novel A-deficient perovskite with exsolved Ni particles a perfect candidate as anode material in intermediate-temperature SOFCs (IT-SOFCs). [ABSTRACT FROM AUTHOR]

This work presents the results of the structural characterization of LaSrGa1−xMgxO4−δ oxides with x = 0.0–0.2 (LSGM'); these oxides with layered K2NiF4-type structure are potential electrolytes of oxygen ions with applications in solid oxide fuel cells (SOFCs). Neutron powder diffraction (NPD), in complement with electrical characterization by AC impedance spectroscopy, enabled the determination of the pathways and mechanisms for diffusion of oxygen ions within the crystalline structure. It was found that the presence of Mg in the structure promotes a non-stoichiometry of oxygen vacancies, which significantly improves the ionic conduction properties by three orders of magnitude. Structural refinements from NPD data in complement with Fourier maps and bond-valence energy landscape (BVEL) calculations, revealed that the oxygen diffusion occurs through the NaCl layer using the 16n crystallographic site of the I4/mmm space group. The oxygen vacancies are concentrated in the 4c sites (O2 oxygen atoms) with (δ) of 0.008 and 0.08 for x = 0.1 and x = 0.2, respectively. The dominant oxygen-ion electrical conductivity increased from order μS cm−1 to mS cm−1 at 900 °C. [ABSTRACT FROM AUTHOR]