Viscosity and surface tension measurements of RE2O3–MgO–SiO2 (RE=Y, Gd, Nd and La) melts

The effect of RE2O3 (RE=Y, Gd, Nd and La) on the viscosity and the surface tension of 45.2MgO–54.8SiO2 (mol%) melts have been investigated with rotating crucible viscometer and ring method, respectively. Additionally, structural characterizations of these quenched vitreous samples have been investigated with Infra-Red spectrometer.The viscosities of RE2O3–MgO–SiO2 melts were found to decrease with increasing the content of any rare-earth additions, which suggests that rare-earth oxide behaves as a network modifier of complex silicate anions in high temperature melts. The viscosities decreased in the order of cationic radius of rare-earth; from Y2O3, Gd2O3, Nd2O3 to La2O3.The surface tension of MgO–SiO2 binary melts were found to increase with increasing the content of any rare-earth additions. The surface tensions obviously increased in the order of cationic radius of rare-earth, which the change of with rare-earth addition is direct antithesis of that of viscosities.The decrease of the absorption band of RE2O3–MgO–SiO2 glasses at 1 060 cm−1 (Si4nO9n2n−) with the attendant increase of the absorption band at 930 cm−1 (Si2O76−). These variations with rare-earth oxides content means that the degree of polymerization of complex silicate anions become smaller with rare-earth oxide additions.The viscosity of rare-earth containing silicate melts linearly increases with cationic field strength of RE3+. The surface tension of rare-earth containing silicate melts linearly decreases with cationic field strength, except Y2O3 additives.