Defect chemistry of Er-doped BaTiO3

Equilibrium electrical conductivity of Er-doped BaTiO3 was studied in terms of Er substitution for Ba and/or Ti sites. When Er3+ ion was substituted for the normal Ti site, the equilibrium conductivity showed a strong evidence of acceptor-doped behavior, while the Er replacement for the Ba site made the material semiconducting. In the case, excess Er was added to the stoichiometric BaTiO3 up to 2.0 mol%, the conductivity profiles were similar to undoped BaTiO3. However, the presence of Er greater than 3.0 mol% resulted in a gradual shift of the conductivity minimum toward low Po2. This behavior is due to the acceptor type impurities, where Er acts as an effective acceptor. It was, thus, confirmed that the solubility of Er in the Ti site is greater than that in the Ba site.