Effects of sintering temperature and poling conditions on the electrical properties of Ba_0.70Ca_0.30TiO₃ diphasic piezoelectric ceramics

The effects of sintering temperature and poling conditions on the electrical properties of tetragonal and orthorhombic diphasic Ba _0.70Ca_0.30TiO₃ (BCT) lead-free ceramics have been systematically investigated. On the one hand, with increasing sintering temperature from 1270 °C to 1400 °C, the bulk density increases monotonically and the Curie temperature keeps almost constant with the value of ∼120 °C, whereas the grain size, the maximum relative dielectric constant, room temperature polarization reach the maximum values for samples sintered at 1340 °C. On the other hand, it is found that the piezoelectric property depends on poling electric field and poling temperature significantly. An enhanced piezoelectric behavior of d₃₃=126 pC/N, k _p=0.29, and Q_m=588 is obtained for the BCT ceramics poled at 100 °C with 30 kV/cm field for 20 min. The aging behavior of the piezoelectric property is also investigated.