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

•Domain switching and lattice strain in polycrystalline K0.5Bi0.5TiO3-BiFeO3-PbTiO3 is evaluated by in-situ high energy synchrotron XRD.•The tetragonal {200} grain family exhibited the highest effective lattice strain up to 8.2 × 10−3 at an electric field of 5 kV/mm.•A partial phase transformation from tetragonal to rhombohedral occurred at high electric field levels, with an average strain of −1.54 × 10−3.•Relaxation of intergranular stress gives rise to enhanced domain switching in KBT-BF-PT ceramics.•The observed self-adapting mechanism could also be exploited in other high performance, high temperature piezoelectric ceramics.