Local structure of the lead-free relaxor ferroelectric (KxNa1-x)0.5Bi0.5TiO3
Local structure of the lead-free relaxor ferroelectric (KxNa1-x)0.5Bi0.5TiO3
复制标题
DOI：
10.1103/physrevb.71.174114
复制
发表时间：
2005-05
影响因子：
3.7
通讯作者：
V. Shuvaeva;D. Zekria;A. Glazer;Q. Jiang;S. Weber;P. Bhattacharya;P. Thomas
中科院分区：
文献类型：
--
作者：
V. Shuvaeva;D. Zekria;A. Glazer;Q. Jiang;S. Weber;P. Bhattacharya;P. Thomas
通过 X 射线吸收精细结构 (XAFS) 研究了无铅弛豫铁电固溶体 (K{sub x}Na{sub 1-x}){sub 0.5}Bi{sub 0.5}TiO{sub 3} 中 Bi 和 Ti 原子的局部环境作为 K 浓度的函数以及 x=0 端元温度的函数。研究发现Bi的局部环境比传统衍射实验确定的环境更加扭曲。最短的 Bi-O 距离确定为 2.22 A，比根据晶体学数据计算的距离短 0.3 A。提出了几种可能的 Bi 配位环境模型，这些模型与 XAFS 数据一致，并提供了更接近理论值的 Bi 键价和。 Ti 从氧八面体中心的位移随着 K 浓度的增加而增加，而最短的 Bi-O 距离显示出不存在成分依赖性。在 K{sub 0.5}Bi{sub 0.5}TiO{sub 3} 中，Ti 位移值为 0.18 A。Na{sub 0.5}Bi{sub 0.5}TiO{sub 3} 中相变点宏观对称性的变化不会导致 Ti 周围径向原子分布的变化，Ti 周围的径向原子分布在整个温度范围内都偏离中心，包括 那么» 顺电立方相。结果可以通过假设存在结构紊乱来解释。« less
The local environment of Bi and Ti atoms in the lead-free relaxor ferroelectric solid-solution (K{sub x}Na{sub 1-x}){sub 0.5}Bi{sub 0.5}TiO{sub 3} has been studied as a function of K concentration and as a function of temperature for the x=0 end member by x-ray absorption fine structure (XAFS). It is found that the local environment of Bi is much more distorted than that determined from conventional diffraction experiments. The shortest Bi-O distances are determined to be 2.22 A, and are 0.3 A shorter than those calculated from the crystallographic data. Several possible models of the Bi coordination environment, which are consistent with the XAFS data and provide bond-valence sums for Bi that are closer to the theoretical values, are proposed. The Ti displacement from the center of the oxygen octahedron increases with K concentration while the shortest Bi-O distance shows no compositional dependence. In K{sub 0.5}Bi{sub 0.5}TiO{sub 3} the value of the Ti displacement is determined to be 0.18 A. The changes of the macroscopic symmetry at the phase transition points in Na{sub 0.5}Bi{sub 0.5}TiO{sub 3} do not lead to changes of the radial atomic distribution around Ti, which is well off-center over the whole temperature range up to and including themore » paraelectric cubic phase. The results can be explained by assuming the presence of structural disorder.« less