Effect of RE2O3 (RE=Y, Gd, Nd and La) Additions on Liquidus Temperatures and Viscosities of MgO-SiO2 Melts

The effect of adding RE2O3 (RE=Y, Gd, Nd and La) on the liquidus temperature of 45.2MgO-54.8SiO2 (mol%) system has been measured by the hot-thermocouple method. Moreover, The effect of adding RE2O3 (RE=Y, Gd, Nd and La) on the viscosity of 45.2MgO-54.8SiO2 (mol%) melt has been measured with a rotating crucible viscometer. In addition, structural characterization of the quench vitreous samples was investigated by using IR spectra. Liquidus temperature and viscosity decreased with increasing of RE2O3 content, depending on the ionic radius of adding rare-earth elements. A marked change was observed in the order of ionic radius from La to Y. These results indicate that RE2O3 behaves as a network modifier in RE2O3- (45.2MgO-54.8SiO2) melts. It is very likely that the RE2O3 with the larger ionic radius will modify the silicate networks more strongly. The IR spectra indicated that the degree of polymerization of silicate anions in RE2O3-(45.2MgO-54.8SiO2) melts decreased with increasing RE2O3 content.