The viscosity of the CaO-SiO2-MnO(-CaF2) slags (CaO/SiO2 = 1.0, MnO = 10, 40 mass%) was measured to clarify the effect of CaF2 on the viscous flow of molten slags at high temperatures. Furthermore, the Raman spectra of the quenched glass samples were quantitatively analyzed to investigate the structural role of CaF2 in a depolymerization of silicate networks. The critical temperature of the slags abruptly increased at 15 mass% CaF2, which was confirmed to originate from a crystallization of cuspidine using XRD analysis. The viscosity of the slags continuously decreased by CaF2 addition in the 10 mass% MnO system, whereas the viscosity of the 40 mass% MnO system was not significantly affected by CaF2 addition. The activation energy for the viscous flow of silicate melts decreased by CaF2 addition and its tendency became less significant in the more basic composition, i.e. in the 40 mass% MnO system. The effect of CaF2 on the viscosity of the slags was quantitatively analyzed using micro-Raman spectra of quenched glass samples accompanying with a concept of silicate polymerization index, Q 3 /Q 2 ratio. A polymerization index continuously decreased with increasing content of CaF2 in the 10 mass% MnO system, whereas it was not affected by CaF2 in the 40 mass% MnO system. Consequently, the bulk thermophysical property of the CaO-SiO2-MnO-CaF2 slags was quantitatively correlated to the structural information.

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The solubility of indium in a molten CaO-SiO 2 -Al 2 O 3 system was measured at 1773 K (1500°C) to establish the dissolution mechanism of indium under a highly reducing atmosphere. The solubility of indium increases with increasing oxygen potential, whereas it decreases with increased activity of basic oxide. Therefore, a dissolution mechanism of indium can be constructed according to the following equation:The relationship between indium capacity and sulfide capacity shows a good correlation that is consistent with theoretical expectations. The enthalpy change of the indium dissolution reaction is negative, which indicates that the dissolution is an exothermic reaction. The heat of dissolution into high-silica melts is greater than that into low-silica melts. The solubility of indium is strongly dependent on the silica content. The activity coefficient, and thus the excess free energy of In 2 O, decreases linearly with increasing silica content, indicating that the In 2 O is believed to behave as a weak basic oxide in the current CaO-SiO 2 -Al 2 O 3 ternary system under reducing conditions.

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