Effect of oxygen partial pressure during firing on the high AC field response of BaTiO₃ dielectrics

The effect of oxygen partial pressure during firing on the high field dielectric response of formulated and undoped BaTiO₃ ceramics was investigated. For formulated ceramics, the dielectric constant of both oxygen- and air-fired samples increased almost linearly with the amplitude of the ac-driving field. Formulated BaTiO₃ samples sintered in a reducing atmosphere produced a sublinear increase in the permittivity with the ac field amplitude. For undoped BaTiO₃ ceramics, the dielectric constant increased sublinearly over a wide range of oxygen partial pressures during firing. It is proposed for the formulated ceramics that the dopant-oxygen vacancy defect dipoles in the shell region accounted for the curvature in the field dependence of the permittivity. These defects appear to add a concentration of weak pinning centers to the potential energy profile through which domain walls move.