MeO (Me=Ca, Mg, Na)-SiO₂-Ga₂O₃系溶融珪酸塩の粘度測定

抄録

The viscosities of CaO, MgO and Na₂O-SiO₂ systems containing Ga₂O₃ were measured and an ionic form of Ga³⁺ ions was discussed on the basis of the effect of Ga₂O₃ on the viscosities of the melts. For example, the viscosity changes with increasing additions of Ga₂O₃ in Na₂O-SiO₂ melts were almost same as those of Al₂O₃ in CaO-SiO₂ melts. The results indicate that Ga₂O₃ plays as an amphoteric oxide as Al₂O₃ in silicate melts. The viscosities measured in this study were well arranged and the ratio of the number of tetrahedrally coordinated Ga³⁺ ions to that of total Ga³⁺ ions could be calculated using a following parameter (P_η) which corresponds to the ratio of n_O⁰⁄n_Si in the binary silicate melts.
The parameter P_η is expressed by
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\ oindentwhere Z_Me is the electric charge of Me ion, n_i is the ion fraction of i ion and X_Ga, is the ratio of tetrahedrally coordinated Ga³⁺ ions to total Ga³⁺ ions.
The X_Ga values of CaO, MgO and Na₂O systems were calculated as 0.481, 0.341 and 0.666 respectively. It is considered that the difference in these values between each system is due to the basicity of the basic oxides consisting of the silicate melts. Ga₂O₃ is founded to play as more basic oxide than Al₂O₃ since the values of X_Ga in this study have about 70% of those of X_Al obtained in the same silicate systems.