Oxygen isotope exchange in the LSM-YSZ composite under the conditions of long-term tests

The stability of the properties of the composite 40 vol % La0.6Sr0.4MnO3 − δ-60 vol % Zr0.83Y0.17O1.92 (LSM-YSZ) held for 1000 h at a temperature of 800°C and an oxygen pressure of 1.01 kPa and changes in its microstructure were studied by isotope exchange and gas-phase analysis. The oxygen exchange was found to occur by the dissociative adsorption mechanism involving the adsorption forms of oxygen on the triple-phase LSM-YSZ-O2 boundary. The rate-determining step of the oxygen exchange of the composite did not change with time. The rate of oxygen exchange decreased by 22%, which is comparable to the decrease in the length of the LSM-YSZ-O2 triple-phase boundary (∼20%), on which oxygen exchange is dominant. The conductivity of the LSM-YSZ composite increased due to the connectivity of the material.