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Abstract  Mixed ionic–electronic conducting $$La_{0.5} Sr_{0.5} Fe_{1 - x} B_x O_{3 - \delta } $$ (B: Al, Cr, Zr, Ga, Ti, Sn, Ta, V, Mg, and In with x = 0, 0.1, 0.2) perovskite materials were produced via solid-state synthesis. In order to study the effect of B-site substitution on the expansion behavior of these materials, their thermal expansion in air up to 900°C and isothermal expansion at the same temperature from air to Ar were measured by dilatometry. Ti and Ta were found to be the most effective substitutions in suppressing the isothermal expansion. The isothermal expansion at 900°C from air to Ar was reduced by 50% by substitution of 20% Ti or 10% Ta. Therefore, these compositions were further characterized by 4-probe total DC conductivity and permeation measurements under air/Ar gradient. The total conductivity of $$La_{0.5} Sr_{0.5} FeO_{3 - \delta } $$ was decreased by more than one order of magnitude at low temperatures and from 430 S/cm, which is the maximum, to around 100 S/cm at 500°C with the addition of Ti and Ta. The normalized oxygen permeation of LSF at 900°C decreased from 0.18 to 0.05 μmol/cm2s and 0.07 μmol/cm2s with the substitution of 20% Ti and 10% Ta, respectively. [ABSTRACT FROM AUTHOR]

The influence of partial substitution of Fe with Ti on the oxygen transport properties of La1−xSrxFeO3 membranes was investigated in view of their application for oxygen separation. Samples of composition (y=0, 0.2) were prepared and their oxygen transport properties characterised by potential step relaxation and by oxygen permeation measurement in an air/argon gradient. With the first technique, chemical diffusion and surface exchange (kS) coefficients were obtained by fitting of the current relaxation data to a single expression valid over the complete time range. The Ti-substituted composition gave slightly larger values of and kS. The trend was opposite for the measured oxygen permeation flux. In the latter experience, ordering of oxygen vacancies was observed at lower temperature, reducing significantly the performance of the material. [ABSTRACT FROM AUTHOR]