Plausible domain configurations and phase contents in two- and three-phase BaTiO₃-based lead-free ferroelectrics

Abstract

We have carried out a comparative study of plausible non-180° domain configurations in the two- and three-phase states of lead-free ferroelectrics Ba(Ti1−xZrx)O3 (0.02 ⩽ x ⩽ 0.08) and (Ba0.85Ca0.15)(Ti0.90Zr0.10)O3, respectively, using the elastic matching approach. The phase contents and stress-relief conditions in Ba(Ti0.93Zr0.07)O3 and (Ba0.85Ca0.15)(Ti0.90Zr0.10)O3 strongly depend on domain types in the rhombohedral R3m phase, whereas domains of the orthorhombic Amm2 phase influence two-phase states in Ba(Ti0.98Zr0.02)O3. Changes in unit-cell parameters of (Ba0.85Ca0.15)(Ti0.90Zr0.10)O3 at poling lead to the complete stress relief in three-phase (P4mm + Amm2 + R3m) structures by increasing the volume fraction of the R3m phase. A link between the heterophase/domain structures and high piezoelectric activity in (Ba0.85Ca0.15)(Ti0.90Zr0.10)O3 is discussed. Based on our results, we state that equal or almost equal volume fractions of the domain types at the three-phase coexistence in (Ba0.85Ca0.15)..(Ti0.90Zr0.10)O3 can lead to an enhanced contribution from domain-wall displacements and therefore, to the large piezoelectric response in this important lead-free ferroelectric compound.

Interplay of domain structure and phase transitions: theory, experiment and functionality

“…A consistent model for twinning at the FE phase front was proposed by Metrat [330] and has been modified and extensively applied to PZT, PMN-PT, BaTiO 3 -based materials by Topolov in the last decades [9,331,332]. The model is based on minimizing interface stress and charges, cf equations ( 1) and ( 2), by the ideal fractions of elastic domains in both phases and the ideal interface directions resulting in complex domain patterns at FE-FE transitions.…”