Recently, we have described SrMo
1-xMg
xO
3-δ perovskites (x = 0.1, 0.2) as excellent anode materials for solid oxide fuel cells (SOFCs), with mixed ionic and electronic conduction (MIEC) properties. After depositing on the solid electrolyte, they were annealed for
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Recently, we have described SrMo
1-xMg
xO
3-δ perovskites (x = 0.1, 0.2) as excellent anode materials for solid oxide fuel cells (SOFCs), with mixed ionic and electronic conduction (MIEC) properties. After depositing on the solid electrolyte, they were annealed for sintering at high temperatures (typically 1000 °C), giving rise to oxidized scheelite-type phases, with SrMo
1-xMg
xO
4-δ (x = 0.1, 0.2) stoichiometry. To obtain the active perovskite phases, they were reduced again in the working anode conditions, under H
2 atmosphere. Therefore, there must be an excellent reversibility between the oxidized Sr(Mo, Mg)O
4-δ scheelite and the reduced Sr(Mo, Mg)O
3-δ perovskite phases. This work describes the topotactical oxidation, by annealing at 400 °C in air, of the SrMo
0.9Mg
0.1O
3-δ perovskite oxide. The characterization by X-ray diffraction (XRD) and neutron powder diffraction (NPD) was carried out in order to determine the crystal structure features. The scheelite oxides are tetragonal, space group
I41/a (No. 88), whereas the perovskites are cubic, s.g.
Pm-3m (No. 221). The Rietveld refinement of the scheelite phase from NPD data after annealing the perovskite at 400 °C and cooling it down slowly to RT evidences the absence of intermediate phases between perovskite and scheelite oxides, as well as the presence of oxygen vacancies in both oxidized and reduced phases, essential for their performance as MIEC oxides. The topotactical relationship between both crystal structures is discussed.
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