Triple-point-type morphotropic phase boundary based large piezoelectric Pb-free material-Ba(Ti0.8Hf0.2)O3-(Ba0.7Ca0.3)TiO3

We report a large piezoelectric Pb-free system-Ba(Ti0.8Hf0.2)O-3-(Ba0.7Ca0.3)TiO3, designed upon a triple-point morphotropic phase boundary (TMPB) idea. The system shows anomalies of both ac (dielectric and piezoelectric) and dc (P-E hysteresis) properties around TMPB, especially the d(33) achieving similar to 550 pC/N at room temperature. Moreover, the detected non-zero thermal hysteresis around triple point shows a first order transition nature and non-isotropic polarization state, as well as verified by our theoretical Landau-type deduction, thus being considered as an important factor to influence the piezoelectricity along TMPB. Our work may stimulate the study on triple-point-related critical phenomena in other ferroic systems. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4724216]