R&D Headquarters, Canon Inc., Ohta, Tokyo 146-8501, Japan.
Reaction Dynamics Research Center, Japan Atomic Energy Agency (JAEA), Sayo-cho, Hyogo 679-5148, Japan.
Sci Rep. 2017 Apr 3;7:45842. doi: 10.1038/srep45842.
To stabilise ferroelectric-tetragonal phase of BaTiO, the double-doping of Bi and Mn up to 0.5 mol% was studied. Upon increasing the Bi content in BaTiO:Mn:Bi, the tetragonal crystal-lattice-constants a and c shrank and elongated, respectively, resulting in an enhancement of tetragonal anisotropy, and the temperature-range of the ferroelectric tetragonal phase expanded. X-ray absorption fine structure measurements confirmed that Bi and Mn were located at the A(Ba)-site and B(Ti)-site, respectively, and Bi was markedly displaced from the centrosymmetric position in the BiO cluster. This A-site substitution of Bi also caused fluctuations of B-site atoms. Magnetic susceptibility measurements revealed a change in the Mn valence from +4 to +3 upon addition of the same molar amount of Bi as Mn, probably resulting from a compensating behaviour of the Mn at Ti sites for donor doping of Bi into the Ba site. Because addition of La instead of Bi showed neither the enhancement of the tetragonal anisotropy nor the stabilisation of the tetragonal phase, these phenomena in BaTiO:Mn:Bi were not caused by the Jahn-Teller effect of Mn in the MnO octahedron, but caused by the Bi-displacement, probably resulting from the effect of the 6 s lone-pair electrons in Bi.
为了稳定 BaTiO 的铁电四方相，研究了 Bi 和 Mn 的双掺杂，最高可达 0.5 mol%。随着 BaTiO:Mn:Bi 中 Bi 含量的增加，四方晶胞常数 a 和 c 分别收缩和伸长，导致四方各向异性增强，铁电四方相的温度范围扩大。X 射线吸收精细结构测量证实，Bi 和 Mn 分别位于 A(Ba)位和 B(Ti)位，并且 Bi 在 BiO 簇中明显偏离对称中心位置。这种 Bi 的 A 位取代也导致了 B 位原子的波动。磁敏度测量表明，在添加与 Mn 等摩尔量的 Bi 时，Mn 的价态从+4 变为+3，可能是由于 Ti 位 Mn 的补偿行为，用于补偿 Bi 对 Ba 位的施主掺杂。因为用 La 代替 Bi 既没有增强四方各向异性，也没有稳定四方相，所以 BaTiO:Mn:Bi 中的这些现象不是 MnO 八面体中 Mn 的 Jahn-Teller 效应引起的，而是由 Bi 位移引起的，可能是由于 Bi 中的 6s 孤对电子的影响。
