The O non-stoichiometry was determined, as a function of the O partial pressure and temperature, by using a high-temperature coulometric titration cell. It was found that, for each value of the O chemical potential, the O non-stoichiometry was almost independent of the temperature. The equilibrium partial energy and entropy which were associated with O incorporation were determined as a function of the O non-stoichiometry and temperature. The results were explained in terms of a model which assumed that conduction electrons, which were created during vacancy formation, gradually filled the electron states in a wide electron band. A new relationship between vacancy concentration, temperature, and O partial pressure was derived which did not exhibit the usual features of a mass action type of equation.

M.H.R.Lankhorst, H.J.M.Bouwmeester: Journal of the Electrochemical Society, 1997, 144[4], 1268-74