LUNAM Université, Université du Maine, UMR CNRS 6283, Institut des Molécules et Matériaux du Mans (IMMM), Olivier Messiaen, F-72085 Le Mans Cedex, France.
Dalton Trans. 2012 May 14;41(18):5696-703. doi: 10.1039/c2dt12389d. Epub 2012 Mar 22.
The effect of partial substitution of molybdenum by phosphorus on the global and local structural arrangement of the fast oxide-ion conductor La(2)Mo(2)O(9) (LAMOX) has been studied by X-ray powder diffraction as well as (139)La and (31)P solid state NMR. The diffraction patterns show that La(2)Mo(2-y)P(y)O(9-y/2) forms a solid solution at low phosphorus concentrations, and that there is a structural phase transition upon increasing phosphorus concentration. This phase transition is also reflected in (139)La and (31)P NMR spectra. The possibility to excite (31)P multiple-quantum coherences of one of the (31)P NMR signals gives evidence of an accumulation of phosphorus atoms on neighbouring Mo-type sites already before formation of three-dimensional precipitates. On the basis of our X-ray and NMR results we propose a possible structural arrangement of the compound La(2)Mo(2-y)P(y)O(9-y/2) that explains the experimental observations by crystal twinning.
通过 X 射线粉末衍射以及 (139)La 和 (31)P 固态 NMR，研究了磷部分取代钼对快氧离子导体 La(2)Mo(2)O(9)（LAMOX）整体和局部结构排列的影响。衍射图谱表明，La(2)Mo(2-y)P(y)O(9-y/2)在低磷浓度下形成固溶体，并且随着磷浓度的增加存在结构相变。这种相变也反映在 (139)La 和 (31)P NMR 光谱中。可以激发其中一个 (31)P NMR 信号的 (31)P 多量子相干性的可能性表明，在形成三维沉淀物之前，磷原子已经在邻近的 Mo 型位上积累。基于我们的 X 射线和 NMR 结果，我们提出了化合物 La(2)Mo(2-y)P(y)O(9-y/2)的可能结构排列，该排列通过晶体重构解释了实验观察结果。
