The conductivity of Ca-doped chromites was determined as a function of composition, temperature, and O2 partial pressure. It was found that the conductivity was independent of the O2 partial pressure, and was proportional to the dopant concentration at high partial pressures. The activation energy for conduction was between 0.12 and 0.14eV, and the mobility was between 0.066 to 0.075cm2/Vs, at temperatures ranging from 900 to 1050C. Under reducing conditions, the conductivity decreased exponentially with decreasing O2 partial pressure, and asymptotically approached a ¼-power relationship. A simple point-defect model, in which CaLa', h• and Vo•• were assumed to be the predominant defect species, was proposed in order to explain the conductivity variation as a function of O2 partial pressure. The O non-stoichiometry which was calculated on the basis of this defect model was consistent with reported thermogravimetric data.

I.Yasuda, T.Hikita: Journal of the Electrochemical Society, 1993, 140[6], 1699-704