High pyroelectricity in lead-free 0.5Ba(Zr 0.2Ti 0.8)O 30.5(Ba 0.7Ca 0.3)TiO 3 ceramics

We report high pyroelectricity in lead-free 0.5Ba(Zr0.2Ti0.8) O-3-0.5(Ba0.7Ca0.3) TiO3 (BZT-50BCT) ceramics which were previously reported to exhibit high piezoelectricity. The pyroelectric coefficient measured by the Byer-Roundy method upon heating for dc-poled samples shows a high value of 5.84 x 10(-4) C m(-2) K-1 at 300 K, comparable to those of PZT-based ceramics and significantly higher than many other lead-free pyroelectric materials. The pyroelectric coefficient calculated from the remanent polarization versus temperature relationship obtained during a cooling process is 17.17 x 10(-4) C m(-2) K-1 at 300 K, which is considerably larger than the value obtained by the Byer-Roundy method. This difference is attributed to the thermal hysteresis of the rhombohedral-tetragonal phase transition between the heating and cooling processes.