Optimized strain performance in <001>-textured Bi0.5Na0.5TiO3-based ceramics with ergodic relaxor state and core—shell microstructure
Xuefan Zhou, Huiping Yang, Guoliang Xue, Hang Luo, Dou Zhang
Abstract
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(0.76Bi 0.5 Na 0.5 TiO 3 −0.24SrTiO 3 )−0.03NaNbO 3 (BNT−ST−0.03NN) ceramics with an ergodic relaxor (ER) state, leading to a large normalized strain ( d 33 *) 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 $$R\bar 3c$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>R</mml:mi> <mml:mover> <mml:mn>3</mml:mn> <mml:mo>¯</mml:mo> </mml:mover> <mml:mi>c</mml:mi> </mml:mrow> </mml:math> 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 $$R\bar 3c$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>R</mml:mi> <mml:mover> <mml:mn>3</mml:mn> <mml:mo>¯</mml:mo> </mml:mover> <mml:mi>c</mml:mi> </mml:mrow> </mml:math> PNRs relative to the homogeneous nontextured samples. The high <001> crystallographic texture and more $$R\bar 3c$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>R</mml:mi> <mml:mover> <mml:mn>3</mml:mn> <mml:mo>¯</mml:mo> </mml:mover> <mml:mi>c</mml:mi> </mml:mrow> </mml:math> 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 d 33 * value remains high up to 518 pm/V at 100 °C with an ultra-low hysteresis of 6%.