The Structure of CaF_2-Al_2O_3-SiO_2 System Glass

The structure of CaF2-A12O3-SiO2 system glass was investigated by using the methods ofDTA, IR, Raman, XPS, XRD, SEM and EDAX. It was found that the structure units, [SiO4] and[AlO4], were linked to form the basic network by means of angle connection and the ions Ca2+ werelocated as the network modifiers. Some ions F- entered as the network formers through replacingO2-, and other ions F- were located as the network modifiers. There were also some ions A13+staying as the network modifiers. Because the F- entered as the network formers, the structureof network became more loose and phase separation of glass took place. Two ldnds of differentphase regions were formed in the glass, and one region contained more Ca2+ and F--, whereasanother region contained more St4+ and A13+. When the above glass with phase sepajration washeat-treated, the crystals of CaF2 firstly came out from the regions containing more Ca2+ and F--.