An investigation of the Fe and Mo oxidation states in Sr2Fe2−xMoxO6 (0.25⩽x⩽1.0) double perovskites by X-ray absorption spectroscopy

Wide‐Range Tuning of the Mo Oxidation State in La1–xSrxFe2/3Mo1/3O3 Perovskites

“…All of the pre‐edges show only one feature at ca. 7114 eV, which is ascribed to the Fe III state, and further features at a lower energy for Fe II are absent . This concurs with the small δ value estimated above and suggests that the Fe oxidation states of all La 1– x Sr x Fe 2/3 Mo 1/3 O 3 samples in Figure are very close to +3.…”

“…For the oxidation states of Fe and Mo shown in Figures and , δ ≤ 0.08 for all samples. This δ value is much smaller than δ = 0.3 for SrFe 1.75/2 Mo 0.25/2 O 3– δ , as reported in ref …”

“…Furthermore, the pre‐edges of the x = 1 and 0.8 samples are intriguingly more significant than those of the others (especially for x = 1). In general, an increase in the pre‐edge intensity can be caused by a smaller coordination number for the Fe ion or enhanced distortion of the local octahedral structure , . In the present case, considering the absence of Fe II features, the significantly enhanced Fe K pre‐edge more likely manifests a unique octahedral distortion of the Fe environment for the end compounds.…”

Sr2Fe2−Mo O6− perovskite as an anode in a solid oxide fuel cell: Effect of the substitution ratio

“…A tiny expansion of unit cells is observed with the increase of Mo content as listed in Table 1. Since the ionic radii of Fe 2+ (0.78Å) and Fe 3+ (0.65Å) are larger than those of Mo 5+ (0.61Å) and Mo 6+ (0.59Å) [18], the expansion of the unit cell is most likely attributed to the transition of the cell structure driven by the variation of the metal centers [21].…”

Challenges in Sr2FeMoO6−δ Thin Film Deposition

“…Mo 5+ appears simultaneously with Fe 2+ . Both reduced ions possess larger ion radii and form the driving force for a cubic to tetragonal lattice transformation between x = 0.35 and 0.50 . Experimentally, this phase transition was obtained already at x = 0.20 in ref.…”