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

Abstract

  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.