一种新型的固溶体——Mgx/2Li1-xIO3晶体结构随成分的变化

本文用室温、高温X射线衍射和差热分析等方法,研究了Mg_x/2Li_1-xIO₃晶体结构及其随成份和温度的变化。Mg(IO₃)₂·LiIO₃二元系形成一种新型的连续固溶体。在室温对于富LiIO₃的固溶体,晶体点阵沿x-y,平面产生畸变,其畸变开始随Mg(IO₃)₂含量的增加而加大,晶体的空间群从P6_{3关键词：}

A NEW TYPE OF CONTINUOUS SOLID SOLUTIONS ——THE VARIATION OF CRYSTAL STRUCTURE TYPES OF Mgx/2Li1-xIO3 WITH COMPOSITION

The variation of crystal structure types of Mg_x/2Li_1-xIO₃ with composition and temperature has been investigated by the methods of DTA and X-ray powder diffraction both at high and room temperatures. A new type of continuous solid solutions has been found in the entire region of the binary system Mg(IIO₃)₂·LiIO₃.For the solid solutions rich in LilO₃, the crystal lattice is distorted in the x-y plane with the increasing concentration of Mg(IO₃)₂, While the space group changes from P6₃ to P112₁. At the composition 3Mg(IO₃)₂·7LiIO₃, the lattice distortion reaches a maximum,γ=120o22′. With further increasing of the concentration of Mg(IO₃)₂, the lattice distortion is reduced, and at the composition Mg(IO₃)₂·LiIO₃) the space group turns back again to P6₃.For the solid solution rich in Mg(IO₃)₂, the lattice is distorted along the z axis, and has been found to be made of unit cells of heterogeneous parameters c (the effect is most prominent at the composition about 20-30mol% LiIO₃). But with increasing temperature, the crystal lattice gradually changes back to unit cells with a uniform parameter.It seems probable that the lattice distortions in the solid solutions are caused by vacancies. The heterogeneous distribution of vacancies results in inhomogeneous parameters c, and it is also due to the presence of vacancies that alters the crystal fields around the anion group, causing the displacement and rotation of IO₃^- with the result that the lattice is distorted along x-y plane.