Stability and oxygen transport property of La0.8Sr0.2Cr0.5Fe0.5O3-δ

The stability of La0.8Sr0.2Cr0.5Fe0.5O3-delta (LSCrF) in reducing atmosphere was investigated by examining the extent of its reaction with hydrogen at elevated temperature. LSCrF powder exposed to diluted hydrogen was found to loss a weight of only -0.5%, corresponding to the formation of oxygen vacancies in the lattice. LSCrF powder exposed to flowing concentrated hydrogen for 30 h was found to decompose partially. The decomposition oxygen partial pressure of LSCrF at 950 degrees C was estimated to be 63 x 10(-28) atm from thermodynamic calculations. The stability of LSCrF under an oxygen chemical potential gradient was also examined by exposing a disk-shaped dense sample to air at one side and to reducing atmosphere (CO) at the other side at elevated temperatures. A thin, porous layer was found to form on the CO side surface. An oxygen permeation flux of 2.5 x 10(-7) mol cm(-2) s(-1) was observed at 950 degrees C under given air/CO gradient. The occurrence of oxygen permeation revealed the presence of mixed oxygen ionic and electronic conductivity. The oxygen ionic conductivity was estimated to be similar to 0.01 S/cm at 950 degrees C. 2014 Elsevier B.V. All rights reserved.