Decoding the Atomic-Scale Structural Origin of Large Strain Performance in BNT-6BT Based Relaxor Ferroelectrics

The relationship between matter properties and their atomic-scale structures is a challenging investigation. For relaxor ferroelectrics, correlating the relaxor mechanisms on the atomic scale to properties is still ambiguous. Here, the correlation between the atomic-scale structure and strain performance of 0.94 Bi_0.5Na_0.5TiO₃-0.06BaTiO₃ (94BNT-6BT) and 0.93 Bi_0.5Na_0.5TiO₃-0.06BaTiO₃-0.01BaZrO₃ (93BNT-6BT-1BZ) is reported. The δ_Ti-Bi/Na displacement vector map based on the annular dark field (ADF) scanning transmission electron microscopy (STEM) image demonstrates the coexistence of tetragonal (T) and rhombohedral (R) phases of the resulting ceramics, and BZ doping increases the proportion of the T phase. Furthermore, the enhanced annular bright field (eABF) STEM image demonstrates that BZ doped ceramics exhibit obvious oxygen octahedral tilt. The oxygen octahedral tilt increased gradually from the domain wall to the inner place of the nanodomain, indicating a regional consistency, which results in enhancement of the relaxor performance and stain property. This study opens exciting opportunities to the design of relaxor ferroelectrics with large strain for high-displacement actuator applications.