Abstract
Compounds Sr3−xPrxFe1.25Ni0.75O7−δ with 0 ≤ x ≤ 0.4 and Ruddlesden–Popper n = 2 type structures were synthesized and investigated by X-ray and neutron powder diffraction, thermogravimetry, and Mössbauer spectroscopy. Both samples, prepared at 1300 °C under N2(g) flow and samples subsequently air-annealed at 900 °C, were studied. The structures contained oxygen vacancies in the perovskite layers, and the Fe/Ni cations had an average coordination number less than six. The oxygen content was considerably higher for air-annealed samples than for samples prepared under N2, 7 − δ = ~6.6 and ~5.6 per formula unit, respectively. Mössbauer data collected at 7 K, below magnetic ordering temperatures, were consistent with X-ray powder diffraction (XRD) and neutron powder diffraction (NPD) results. The electrical conductivity was considerably higher for the air-annealed samples and was for x = 0.1~30 S·cm−1 at 500 °C. The thermal expansion coefficients were measured in air between room temperature and 900 °C and was found to be 20–24 ppm·K−1 overall.
Highlights
Layered oxides with Ruddlesden–Popper (RP) type structures with general compositionAn+1 Bn O3n+1 [1] have represented so-called bifunctional materials, since they contain intergrowth of a rock-salt (AO) slab responsible for oxide-ion conductivity, and perovskite slabs (n·ABO3 ) which provide electronic conductivity
We have shown that Sr3−xYxFe1.25Ni0.75O7−δ RP phases have a comparatively low the match commonly expansion coefficients (TECs) of 14.4
We have shown that Sr3−x Yx Fe1.25 Ni0.75 O7−δ RP phases have a comparatively low TEC of ppm·K−1 [14] (x = 0.75)
Summary
Layered oxides with Ruddlesden–Popper (RP) type structures with general composition. An+1 Bn O3n+1 [1] have represented so-called bifunctional materials, since they contain intergrowth of a rock-salt (AO) slab responsible for oxide-ion conductivity, and perovskite slabs (n·ABO3 ) which provide electronic conductivity. The thermal (TECs) for these compounds, do not match thosedo of not the match commonly expansion coefficients (TECs) for these compounds, those used of theelectrolytes commonly for One reason for this is the change in oxygen content, leading to a strong used electrolytes for SOFC. We have shown that Sr3−x Yx Fe1.25 Ni0.75 O7−δ RP phases have a comparatively low TEC of ppm·K−1 [14] (x = 0.75). This may be attributed to the higher strength of the Y–O bond, as compared.
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