Linking large piezoelectric coefficients to highly flexible polarization of lead free BaTiO3-CaTiO3-BaZrO3 ceramics

Abstract

We report a large d31 piezoelectric coefficient and corresponding electromechanical coupling factor, Kp, of 0.5Ba(Zr0.2Ti0.8)O3–0.5(Ba0.7Ca0.3)TiO3 (BCTZ50) and 0.68Ba(Zr0.2Ti0.8)O3–0.32(Ba0.7Ca0.3)TiO3 (BCTZ32) lead-free piezoceramics. The piezoelectric coefficient, d31, 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 d33 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.