Stabilization of the Fatigue-Resistant Phase by CuO Addition in (Bi1/2Na1/2)TiO3-BaTiO3

Bipolar electric fatigue in the lead‐free material 0.94(Bi1/2Na1/2)TiO3–0.06BaTiO3 (BNT‐BT) is investigated throughout the first 100 cycles in which a strong degradation of macroscopic electromechanical properties is observed. The addition of 1 mol% CuO successfully stabilizes the fatigue‐resistant phase and retains the initial electromechanical properties. In order to explain the underlying mechanisms, two models are proposed: degradation takes place either due to (1) pinning of the domain walls by defect charges or (2) an electric field‐induced symmetry change that reduces the amount of rhombohedral phase that dominates the macroscopic properties. This different approach based on symmetry considerations to explain the fatigue behavior has an impact on future fatigue studies that are concerned with novel lead‐free materials on the basis of BNT‐BT.