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.