Point defect concentrations in barium titanate revisited

An analytic link between the oxygen partial pressure and the concentrations of the point defects for given temperatures and A/B conditions is presente d for perovskites. A clear distinction between three different conditions i s made. These are the sintering conditions, an intermediate metastable stat e, and a low-temperature metastable state. The analytical solution for a me tastable state resulting from nonequilibrated metal vacancies permits a mor e accurate and self-consistent approach to calculating the equilibrium cons tants from conductivity-O(O-2) data. One of the reasons for the higher accu racy is that there is no need to divide the existence regime into subregime s with different approximations to the electroneutrality equation (Brouwer approximation). An excellent fit of the experimental conductivity data to a single function with only two adjustable parameters over all conductivity- P(O-2) space is obtained. The relative importance of frozen-in metal vacanc ies and foreign acceptors is discussed for BaTiO3.