Abstract The dehydration of the large pore aluminophosphate AlPO4-54•xH2O was studied in situ as a function of vacuum pressure at room temperature by infrared spectroscopy and x-ray diffraction. On polycrystalline samples, under primary vacuum, the adsorbed water is removed very rapidly. The structural water in the AlO6 octahedra is then removed slowly with the quantity of the fully dehydrated form gradually increasing from 43 to 65% of the total material. This results in a two-phase mixture of fully dehydrated and a distinct partially dehydrated AlPO4-54•1/2H2O phase containing structural water. These phases have almost identical a cell parameters and very close c parameters. Secondary vacuum increases the amount of fully dehydrated material to more than 76%. Prolonged heating under vacuum increases the amount of fully dehydrated material to 90%. On single crystal samples, removal of adsorbed water is slower and results in a reduction in crystal quality, however prolonged exposure to primary vacuum yielded fully dehydrated material without the need for heating. The monoclinic structure of anhydrous AlPO4-54, space group Cm, with a doubled unit cell was confirmed using single crystal synchrotron x-ray diffraction data.

中文翻译：

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AlPO4-54脱水的原位X射线衍射和红外光谱研究

摘要 通过红外光谱和X 射线衍射在室温下原位研究了大孔磷酸铝AlPO4-54•xH2O 的脱水与真空压力的关系。在多晶样品上，在初级真空下，吸附的水被非常迅速地去除。随着完全脱水形式的数量从总材料的 43% 逐渐增加到 65%，AlO6 八面体中的结构水被缓慢去除。这导致完全脱水和不同的部分脱水的 AlPO4-54•1/2H2O 相的两相混合物，其中含有结构水。这些相具有几乎相同的 a 单元参数和非常接近的 c 参数。二次真空将完全脱水的材料量增加到 76% 以上。在真空下长时间加热可将完全脱水的材料量增加到 90%。在单晶样品上，吸附水的去除速度较慢，导致晶体质量下降，但长时间暴露在初级真空下会产生完全脱水的材料，而无需加热。使用单晶同步加速器 X 射线衍射数据证实了具有双晶胞的无水 AlPO4-54 空间群 Cm 的单斜结构。