SYNTHESIS AND STRUCTURE OF HYDRATED LANTHANUM CARBONATE

以碳酸氢铵为沉淀剂合成了碳酸镧晶体。经Ｘ射线衍射测定，晶体属正交晶系，晶胞参数ａ＝０．８４８７ｎｍ，ｂ＝０．９５６４ｎｍ，ｃ＝０．４４８６ｎｍ。其结构与文献中提到的镧石型稀土碳酸盐的结构相接近。碳酸镧的红外光谱说明其内部存在着非等价的碳酸盐群。碳酸镧在热分解过程中，存在着稳定的中间产物Ｌａ２Ｏ３·ＣＯ２。

Crystalline lanthanum carbonate was synthesized using ammonium bicarbonate as the precipitant.The X-ray diffraction data were indexed in the orthorhombic system with cell parameters a=0.8487nm,b=0.9564nm and c=0.4486nm.The structure is closely related to those of the lanthanite type rare earth carbonates in the literature.The IR data for lanthanum carbonate show the presence of two different carbonate groups.In the process of thermal decomposition of lanthanum carbonate to oxide,an intermediate La2O...