Field and temperature dependence of dielectric properties in BaTiO3-based piezoceramics

The high-field dielectric properties of a commercial cobalt-doped BaTiO3 piezoceramic were determined by analysis of P-E (polarization-electric field) hysteresis loops. Measurements recorded under a continuous high AC field (amplitude E0 = 2 kV mm-1) established that the material underwent a diffuse ferroelectric phase transformation at a temperature of approximately 100°C. Gradual increases in the dielectric coefficients ε′r and ε″r were observed on increasing the field amplitude from 0.1 to 0.4 kV mm-1, which were attributed to increased contributions from reversible ferrroelectric domain wall vibration. Beyond a certain threshold field level (typically in the range 0.4 to 0.8 kV mm-1), sharp increases in ε′r and ε″r were evident, corresponding to the onset of ferroelectric domain switching. The appearance of a significant internal bias field Ei could also be correlated with the onset of domain switching. A procedure was proposed for determination of the intrinsic (ionic), the ferroelectric domain wall vibration and the domain switching contributions to the dielectric coefficients by analysis of the linear reversible and nonlinear hysteretic components of the measured P-E loops.