High‐Temperature Creep Behavior of Mixed Conducting La _0.5 Sr _0.5 Fe _{1− x} Co _x O _3‐δ (0.5≤ x ≤1) Materials

Steady‐state compressive creep rate of La _0.5 Sr _0.5 Fe _0.5 Co _0.5 O _3−δ (LSFC) and La _0.5 Sr _0.5 CoO _3−δ (LSC) is reported in the temperature region 900°–1050°C and stress range 5–28 MPa. The stress exponents for the two materials were 1.71±0.18 and 1.24±0.15, respectively. The activation energy for creep was considerably higher for LSC (619±56 kJ/mol) than for LSFC (392±28 kJ/mol). The grain size exponent for LSC was 1.28±0.14. Considerably higher creep rates were observed for both materials in N ₂ compared with air. Relaxation by creep of chemical‐induced stresses in oxygen‐permeable membranes is addressed, especially at low partial pressure of oxygen.