Zhang Hangfeng, Krynski Marcin, Fortes A Dominic, Saunders Theo Graves, Palma Matteo, Hao Yang, Krok Franciszek, Yan Haixue, Abrahams Isaac
Department of Chemistry, Queen Mary University of London, Mile End Road, London E1 4NS, U.K.
School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, U.K.
J Am Chem Soc. 2024 Feb 28;146(8):5569-5579. doi: 10.1021/jacs.3c13927. Epub 2024 Feb 14.
The classical view of the structural changes that occur at the ferroelectric transition in perovskite-structured systems, such as BaTiO, is that polarization occurs due to the off-center displacement of the B-site cations. Here, we show that in the bismuth sodium titanate (BNT)-based composition 0.2(BaSrTiO)-0.8(BiNaTiO), this model does not accurately describe the structural situation. Such BNT-based systems are of interest as lead-free alternatives to currently used materials in a variety of piezo-/ferroelectric applications. A combination of high-resolution powder neutron diffraction, impedance spectroscopy, and ab initio calculations reveals that Ti contributes less than a third in magnitude to the overall polarization and that the displacements of the O ions and the A-site cations, particularly Bi, are very significant. The detailed examination of the ferroelectric transition in this system offers insights applicable to the understanding of such transitions in other ferroelectric perovskites, particularly those containing lone pair elements.
在钙钛矿结构体系（如钛酸钡）中，铁电转变时发生的结构变化的传统观点是，极化是由于B位阳离子的偏心位移而产生的。在此，我们表明，在基于钛酸铋钠（BNT）的成分0.2（BaSrTiO）-0.8（BiNaTiO）中，该模型不能准确描述结构情况。这种基于BNT的体系作为目前各种压电/铁电应用中所用材料的无铅替代品而备受关注。高分辨率粉末中子衍射、阻抗谱和从头算计算相结合表明，Ti对总极化的贡献在量级上不到三分之一，并且O离子和A位阳离子（特别是Bi）的位移非常显著。对该体系中铁电转变的详细研究为理解其他铁电钙钛矿中的此类转变提供了见解，特别是那些含有孤对元素的钙钛矿。
