Oxygen Nonstoichiometry, Electrical Conductivity, Chemical Expansion and Electrode Properties of Perovskite-Type...

X-ray diffraction analysis of the pseudo-binary SrFe_1-VO_3-δ system showed that the solid solution formation limit at atmospheric oxygen pressure corresponds to x ≈ 0.1. SrFe_0.9V_0.1O_3-δ has a cubic perovskite-type structure with the Pm3¯m space group. The oxygen nonstoichiometry variations in SrFe_0.9V_0.1O_3-δ, measured by coulometric titration in the oxygen partial pressure range of 10^-21 to 0.5 atm at 1023-1223 K, can be adequately described using an ideal solution approximation with V⁵⁺ as the main oxidation state of vanadium cations. This approach was additionally validated by statistical thermodynamic modeling. The incorporation of vanadium decreases both oxygen deficiency and the average iron oxidation state with respect to undoped SrFeO_3-δ. As a result, the electrical conductivity, thermal expansion and chemical expansivity associated with the oxygen vacancy formation all become lower compared to strontium ferrite. At 923 K, the conductivity of SrFe_0.9V_0.1O_3-δ is 14% lower than that of SrFeO_3-δ but 21% higher compared to SrFe_0.9Ta_0.1O_3-δ. The area-specific polarization resistance of the porous SrFe_0.9V_0.1O_3-δ electrode deposited onto 10 mol.% scandia- and 1 mol.% yttria-co-stabilized zirconia solid electrolyte with a protective Ce_0.9Gd_0.1O_2-δ interlayer, was 0.34 Ohm×cm² under open-circuit conditions at 1173 K in air.