Optimized strain performance in <001>-textured Bi0.5Na0.5TiO3-based ceramics with ergodic relaxor state and core—shell microstructure

Abstract

Herein, a high strain of ∼0.3% with a small hysteresis of 43% is achieved at a low electric field of 4 kV/mm in the highly <001>-textured 0.97(0.76Bi0.5Na0.5TiO3−0.24SrTiO3)−0.03NaNbO3 (BNT−ST−0.03NN) ceramics with an ergodic relaxor (ER) state, leading to a large normalized strain (d33*) of 720 pm/V. The introduction of NN templates into BNT−ST induces the grain orientation growth and enhances the ergodicity. The highly <001>-textured BNT−ST−0.03NN ceramics display a pure ergodic relaxor state with coexisted ferroelectric R3 ¯ c and antiferroelectric P4bm polar nanoregions (PNRs) on nanoscale. Moreover, due to the incomplete interdiffusion between the NN template and BNT−ST matrix, the textured ceramics present a core-shell structure with the antiferroelectric NN core, and thus the BNT-based matrix owns more R3 ¯ c PNRs relative to the homogeneous nontextured samples. The high <001> crystallographic texture and more R3 ¯ c PNRs both facilitate the relaxor-to-ferroelectric transition, leading to the low-field-driven high strain, while the ergodic relaxor state ensures a small hysteresis. Furthermore, the d33* value remains high up to 518 pm/V at 100 °C with an ultra-low hysteresis of 6%.[Figure not available: see fulltext.].