Polarization dynamics variation across the temperature- and composition-driven phase transitions in the lead-free Ba(Zr0.2Ti0.8)O3−x(Ba0.7Ca0.3)TiO3 ferroelectrics

The method of thermally stimulated depolarization currents (TSDC) and polarization switching experiments over a large field, time, and temperature regime are used to refine the controversial phase diagram of Ba(Zr0.2Ti0.8)O3−x(Ba0.7Ca0.3)TiO3 and comprehend its relation to ferroelectric and piezoelectric properties. TSDC results suggest the existence of three ferroelectric phases for the composition range of 0.30 ≤ x ≤ 0.60, which can be assigned to the rhombohedral (R), presumably orthorhombic (O), and tetragonal (T) symmetries. Spontaneous polarization is maximal all over the entire intermediate phase region, where the activation barrier for polarization switching is small, not just at R-O or O-T boundaries as might be deduced from previous observations