Bulk Conductivity and Defect Chemistry of Acceptor-Doped Strontium Titanate in the Quenched State

The grain bulk conductivity of acceptor-doped SrTiO₃ ceramics was investigated by the impedance analysis method after quenching from high-temperature equilibria. The influence of the oxygen partial pressure during equilibration, P ^Eq_O2, is described in terms of a defect model for titanates. From a comparison between the experimental results and the predictions of this model, a predominant ionic conductivity is concluded for a wide P ^Eq_O2 range (approximately 10⁻¹¹ to 10⁵ Pa). The influence of the ionization energy of the acceptors and of possible defect association is discussed.