Raman Spectroscopic Study on the Structure of Oxide Melts containing Fluoride

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In order to elucidate the structure of oxide melts containing fluorine, the quantitative informations are necessary concerning the structure of silicates and aluminates. In this study, at first, a Raman spectral study has been carried out on the structure of the glassy binary silicates containing alkali or alkaline earth oxides and ternary silicates with <Al_2O_3> or <TiO_2> , where an argon-ion laser beam of 4880 A has been used as an exciting light. The obtained Raman spectra were deconvoluted with the Gaussian function and the fraction of each silicate anion was evaluated relating to the number of non-bridging oxygens per each silicon atom. And the effects of anions on the Si-O bondings and behavior of <Al^(3+)> and <Ti^(4+)> were discussed. On the basis of the results described above, Raman measurements of the glassy CaO- <SiO_2> - <CaF_2> and CaO- <Al_2O_3> - <CaF_2> samples melted in the closed crucible and deconvolution of the spectra have been made and the following conclusions were obtained.(1) <CaF_2> in the CaO- <SiO_2> binary basic slags behaves as a diluent and diluent and does not have any effect on the structure of silicates, in which the basicity is larger than unity. On the other hand, a part of <CaF_2> added breaks the silicate networks at the acid slags. (2) The fraction of <CaF_2> which acts as a modifier increases with decrease in the basicity and three dimensional network is broken to chains of silicates. (3) The existence of the silicon-fluorine bonding in the CaO- <SiO_2> - <CaF_2> system with the basicity below 1 was confirmed, and the Raman band caused by the Si-F bonding was asigned. (4) Addition of <CaF_2> to the CaO- <Al_2O_3> binary slags has no effects on the structure of aluminates. <CaF_2> behaves only as a diluent to the CaO- <Al_2O_3> system.