Phase coexistence and ferroelastic texture in high strain (1-x)Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3 piezoceramics

Dielectric permittivity and x-ray diffraction measurements were used to identify a region of phase coexistence between the rhombohedral and tetragonal phases near the morphotropic phase boundary in (1-x)Ba(Zr0.2Ti0.8)O-3-x(Ba0.7Ca0.3)TiO3 (BZT-BCT). This phase coexistence prevails over a considerable composition and temperature range and is bounded by single rhombohedral or tetragonal phases. The maximum piezoelectric response measured in terms of maximum strain divided by maximum electric field, S-max/E-max, is extraordinarily high, with the largest value of 1310 pm/V for x = 0.45. Electrical poling induces ferroelastic domain textures in both the rhombohedral and tetragonal phases simultaneously, which increases the piezoelectric performance significantly. The stability of that ferroelastic texture is limited by the phase transition at the morphotropic phase boundary, suggesting coupling between both coexisting phases and limiting potential applications. The results were confirmed using in situ temperature dependent synchrotron x-ray diffraction. The findings indicate that the BZT-BCT system is considerably more complex than discussed in initial reports and that this complexity is likely related to the impressive properties that have been previously reported. VC 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4730342]