Effects of Uniaxial Compaction Pressure on the Dielectric Properties of B a T i O₃/Polyvinylidene Fluoride Composites

In this study, the formation of internal stress, domain switching, phase transition, and dielectric property variations of BaTiO₃ particles in the BaTiO₃-PVDF composites are investigated. It is found that the characteristics of the composite are highly affected by the magnitude of the compaction pressure employed. The internal stress may change from a state of compressive to tensile as the pressure increases. This is characterized by domain switching, in which the c axis rotates 90°, leaning from perpendicular to the sample surface to parallel. Meanwhile, a larger compaction pressure favors the formation of orthorhombic (o-) BaTiO₃, which can result from the effects of internal stress and crystallite size. Composites made of BaTiO₃ crystallites with higher internal stress and o-BaTiO₃ contents may have higher values of the dielectric constant.