Dielectric properties of fine-grained BaTiO₃ ceramics under high pressure

We investigate the temperature dependence of the dielectric constant of BaTiO₃ ceramic with coarse to nano-grain size under different hydrostatic high pressures up to 5000bar in the range between room temperature and 200°C. The ferroelectric-to-paraelectric phase transition temperatures T_c are determined from the peak of dielectric constant versus temperature. The values of average grain-size are estimated from the SEM images. It is found that the magnitude of dT_c/dp varies considerably from sample to sample depending on grain size. The Curie point T_c of the sample with small grain size decreases more sharply than that of samples with larger one.