Effect of Acceptor (Mg) concentration on the resistance degradation behavior in acceptor (Mg)-doped BaTiO₃ bulk ceramics: II. Thermally stimulated depolarization current analysis

Thermally stimulated depolarization current (TSDC) of acceptor (Mg)-doped BaTiO₃ ceramics was analyzed with different acceptor concentrations for coarse-grained specimens with uniform grain sizes. In all specimens, the increase of the polarization temperature (T_P) for a fixed condition of polarization field (E_P) and polarization time (t_P) increased TSDC peak associated with an oxygen vacancy (V_O ^••) relaxation. When the acceptor concentration is increased, both T_P to generate same magnitude of TSDC and the relaxation temperature (T_m) of the TSDC peak systematically decreased. On the other hand, the activation energy of the oxygen vacancy relaxation showed roughly constant values of ∼0.9 eV, irrespective of acceptor concentration. Such behavior can be explained by a decrease in the relaxation time constant (τ₀), which is in turn associated with the shape of oxygen vacancy profile in the specmen after polarization. The decrease of T_P, T_m, τ₀, and the little change of activation energy from the TSDC data with the increase of acceptor concentration implies an increase in the oxygen vacancy concentration C(V _O^••). The experimentally observed behavior of C(V_O^••) vs acceptor concentration could be explained by the defect chemical model, and from these results, the acceptor ionization energy E_A was estimated to be about 1.0 eV.