Nonstoichiometry in Acceptor‐Doped BaTiO ₃

Abstract

The effect of added Al, as an acceptor impurity, on the equilibrium electrical conductivity of large‐grained, polycrystalline BaTiO 3 , is consistent with a previously proposed defect model which involves only doubly ionized oxygen vacancies, electrons, holes, and acceptor impurities. The behavior is an extension of that of undoped BaTiO 3 , in which an accidental net acceptor excess already plays an important role. Comparison of the derived active acceptor content with the amount of added Al indicates that Al is <50% effective in creating acceptor levels. The magnitude of a small Po 2 ‐independent conductivity component, necessary to fit the observed conductivity minima, increases with added Al content. This is consistent with a contribution from extrinsic oxygen vacancy conduction.