Thermal stability, oxygen non-stoichiometry and transport properties of LaNi0.6Fe0.4O3

Thermal stability, oxygen non-stoichiometry and electrical conductivity of LaNi0.6Fe0.4O3−δ were investigated in the temperature region of 20–1000 °C in Ar/O2 gas flows at oxygen partial pressures between 0.5 and 21,000 Pa. Diffusion mobility was measured in Ar/O2 gas flow at pO2 = 18 Pa. Crystal structure of this compound was found to be stable at the mentioned experimental conditions. LaNi0.6Fe0.4O3−δ is a p-type semiconductor with metallic type conductivity above 150 °C at the investigated pO2 range. Two different (fast and slow) oxygen exchange areas on the temperature-pO2 diagram were established, which are due to two different oxygen anion positions in the double B-site mixed perovskite structure. Oxygen non-stoichiometry in the fast oxygen exchange region reaches about 0.005 of oxygen atomic index. Chemical diffusion and oxygen surface exchange coefficients do not vary at 600–800 °C, but show visible increase above 800–850 °C.