The ISIS Facility, STFC Rutherford Appleton Laboratory, Didcot, Oxfordshire, UK OX11 0QX.
Dalton Trans. 2009 Oct 28(40):8737-45. doi: 10.1039/b910484b. Epub 2009 Aug 28.
The highly disordered structure of the delta phase of Bi2O3, which possesses the highest known oxide-ion conductivity, has been studied using neutron powder diffraction. A detailed analysis of data collected at 1033(3) K using Rietveld refinement indicates that the time-averaged structure of delta-Bi2O3 can be described using the accepted model of a disordered, anion-deficient fluorite structure in space group Fm3m. However, reverse Monte Carlo modelling of the total (Bragg plus diffuse) scattering demonstrates that the local anion environment around the Bi3+ resembles the distorted square pyramidal arrangement found within the stable alpha and metastable beta phases at ambient temperature, which is characteristic of the cation's 6s2 lone-pair configuration. Similarities between the structures of the highly disordered delta phase and the ambient temperature metastable beta phase are used to support this assignment and assess the validity of previous structural models based on short-range ordering of vacancies within the cubic lattice of delta-Bi2O3.
使用中子粉末衍射研究了具有已知最高氧化离子电导率的 Bi2O3 的 delta 相的高度无序结构。使用 Rietveld 精修对在 1033(3) K 收集的数据进行的详细分析表明，delta-Bi2O3 的时均结构可以用无序的、阴离子不足的萤石结构的公认模型来描述，空间群为 Fm3m。然而，对总（布拉格加漫散射）散射的逆蒙特卡罗建模表明，Bi3+ 周围的局部阴离子环境类似于在环境温度下稳定的 alpha 和亚稳 beta 相中发现的扭曲的四方锥排列，这是阳离子的 6s2 孤对构型的特征。高度无序的 delta 相和环境温度亚稳 beta 相之间结构的相似性用于支持这一分配，并评估基于 delta-Bi2O3 立方晶格中空位短程有序的先前结构模型的有效性。
