Actuation mechanisms in mixed-phase K0.5Bi0.5TiO3-BiFeO3-PbTiO3 ceramics

We report an in-situ synchrotron X-ray diffraction study of K0.5Bi0.5TiO3-BiFeO3-PbTiO3 ceramics, which exhibit a T-c of around 450 degrees C. The electromechanical actuation mechanisms comprise contributions from coexisting tetragonal and rhombohedral phases. The tetragonal {200} grain family exhibited the highest effective lattice strain, up to 8.2 x 10(-3) at 5 kV/mm. Strong strain anisotropy in the tetragonal phase and field-induced inter granular stresses facilitate a partial transformation from tetragonal (high strain anisotropy) to rhombohedral (low strain anisotropy) at high electric field levels, with an average linear transformation strain of -1.54 x 10(-3). The domain switching behavior was effectively enhanced in both tetragonal and rhombohedral phases after the phase transformation, due to the release of intergranular stress. This observed self-adapting mechanism in tuning intergranular stress through partial phase switching in the morphotropic KBT-BF-PT composition with large lattice distortion could also be exploited in other perovskite systems in order to achieve high performance high temperature piezoelectric ceramics.

Automated summary

In-situ synchrotron X-ray diffraction was used to study K0.5Bi0.5TiO3-BiFeO3-PbTiO3 ceramics with a Curie temperature around 450 degrees C. The study revealed a self-adapting mechanism in tuning intergranular stress through partial phase switching, which enhanced domain switching behavior in both tetragonal and rhombohedral phases. This mechanism could be exploited in other perovskite systems for high performance high temperature piezoelectric ceramics.