Material softening by cation off-centering in Bi-based lead-free piezoelectric ceramics

• Published in: Japanese Journal of Applied Physics Vol. 60; no. SF; p. SFFD01
• Main Authors: Kim, Sangwook, Nam, Hyunwook, Fujii, Ichiro, Ueno, Shintaro, Moriyoshi, Chikako, Kuroiwa, Yoshihiro, Wada, Satoshi
• Format: Journal Article
• Language: English
• Published: Tokyo IOP Publishing 01.11.2021; Japanese Journal of Applied Physics
• Subjects: Barium titanates; Bi ion off-centering; BiFeOamp;amp;lt;subamp;amp;gt;3amp;amp;lt;/subamp;amp;gt;-BaTiOamp;amp;lt;subamp;amp;gt;3amp;amp;lt;/subamp;amp;gt; Crystal structure; Displacement; Lead free; Material softening; Parameters; Piezoelectric ceramics; Softening; Stability; Synchrotron radiation; Synchrotrons
• ISSN: 0021-4922; 1347-4065
• DOI: 10.35848/1347-4065/ac0fb5

The origin of material softening in BiFeO3–BaTiO3 ceramics was assessed by studying the crystal structure and structural parameters. The crystal structure was investigated at 950 K by synchrotron radiation X-ray diffraction using structure refinement; structural parameters were calculated from the final structure refinement results. The crystal structure was cubic, with Bi3+ ions off-centering into six equivalent neighboring sites along the 〈100〉 direction. We suggested that the stability of the Bi off-centering position and Bi off-centering displacement affects the material softening. The maximum material softening occurred in 0.70BiFeO3–0.30BaTiO3 ceramics with the largest Bi ion off-centering displacement and smallest Bi–O bond length, which provided the stable Bi ion off-centering position. Therefore, the material softening is attributed to the stability of the Bi ion off-centering position and the Bi ion off-centering displacement. The suggested model of material softening can provide essential information for the design and development of next-generation lead-free piezoelectric materials.