Temperature dependence of dielectric nonlinearity of BaTiO₃ ceramics

In many commercially utilized ferroelectric materials, the motion of domain walls is an important contributor to the functional dielectric and piezoelectric responses. This paper compares the temperature dependence of domain wall motion for BaTiO₃ ceramics with different grain sizes, point defect concentrations, and formulations. The grain boundaries act as significant pinning points for domain wall motion such that fine-grained materials show smaller extrinsic contributions to the properties below the Curie temperature and lower residual ferroelectric contributions immediately above the Curie temperature. Oxygen vacancy point defects make a modest change in the extrinsic contributions of undoped BaTiO₃ ceramics. In formulated BaTiO₃, extrinsic contributions to the dielectric response were suppressed over a wide temperature range. It is believed this is due to a combination of reduced grain size, the existence of a core-shell microstructure, and a reduction in domain wall continuity over the grain boundaries.