Absence of the heat capacity anomaly in the Pb-free relaxor BaTi0.65Zr0.35O3

A relaxor ferroelectrics, BaTi0.65Zr0.35O3 (BTZ35), which was free from lead, was synthesized and the physicothermal properties were measured. The heat capacity was measured using a homemade adiabatic calorimeter at temperatures from 13 K to 420 K, and the dielectric constant measurements were carried out between 1 kHz and 1 MHz at temperatures from 20 K to 420 K. No anomaly was detected in the heat capacity curve for the whole temperature range covered in the present experiments, while a large and broad peak was observed in the dielectric constant curve. The dielectric constant showed the relaxor type frequency dependence. The results of the present experiments were compared with our previous studies on a typical relaxor of lead-based complex perovskite oxide, PbMg1/3Nb2/3O3 (PMN), which showed a large heat capacity anomaly as well as a large broad peak of dielectric constant due to formation of ferroelectric polar nanoregion in the crystal. Some differences between the two compounds, BTZ35 and PMN, were compared and the mechanism was discussed.