Linking large piezoelectric coefficients to highly flexible polarization of lead free BaTiO 3 -CaTiO 3 -BaZrO 3 ceramics

We report a large d 31 piezoelectric coefficient and corresponding electromechanical coupling factor, K p , of 0.5Ba(Zr 0.2 Ti 0.8 )O 3 -0.5(Ba 0.7 Ca 0.3 )TiO 3 (BCTZ50) and 0.68Ba(Zr 0.2 Ti 0.8 )O 3 -0.32(Ba 0.7 Ca 0.3 )TiO 3 (BCTZ32) lead-free piezoceramics. The piezoelectric coefficient, d 31 , reaches a high value of 200 pC/N for BCTZ50 at room temperature which is comparable to the one of the soft PZT. This confirms the previously reported d 33 for the same material. A useful way to achieve such performances at the expense of a smaller thermal budget is suggested, enabling better control of the ceramics composition and microstructure. Based on pyroelectric and ferroelectric hysteresis loops measurements, we show that such outstanding properties are likely due to the high flexibility of polarization under thermal and electric stresses.