Elastic, piezoelectric, and dielectric properties of Ba(Zr0.2Ti0.8)O3-50(Ba0.7Ca0.3)TiO3 Pb-free ceramic at the morphotropic phase boundary

There is an urgent demand for high performance Pb-free piezoelectrics to substitute for the current workhorse, the lead zirconate titanate (PZT) family. Recently, a triple point (also tricritical point) type morphotropic phase boundary (MPB) in Pb-free Ba(Zr0.2Ti0.8)O-3-x(Ba0.7Ca0.3)TiO3 system has been reported that shows equally as excellent piezoelectricity as soft PZT at room temperature (Liu and Ren(6)). In the present study, we measured a full set of elastic, piezoelectric, and dielectric properties for the MPB composition, Ba(Zr0.2Ti0.8)O-3-50(Ba0.7Ca0.3)TiO3 (BZT-50BCT), by using a resonance method. The resonant method gives piezoelectric properties d(33)=546 pC/N, g(33)=15.3 x 10(-3) Vm/N, electromechanical coupling factor k(33)=65%, and the elastic constant s(33)(E)=19.7 x 10(-12) m(2)/N, c(33)(E)=11.3 x 10(10) N/m(2), which are close to the properties of soft PZT (PZT-5A). Furthermore, the piezoelectric coefficients (k(33), d(33)), the ferroelectric properties (coercive field, remnant polarization), and the elastic constants (s(33)(D), s(33)(E), c(33)(D), c(33)(E)) were also determined as a function of temperature ranging from -50 to 60 degrees C. Our results show that the properties are optimal around MPB temperature (room temperature) and decrease with deviations from the MPB temperature. Nevertheless, the piezoelectric coefficient d(33) can maintain an appreciable level of 93 pC/N even at -50 degrees C. The high piezoelectric properties can be ascribed to the low polarization anisotropy as well as the elastic softening at MPB. (C) 2011 American Institute of Physics. [doi:10.1063/1.3549173]