Free volume and structure of Gd2O3 and Y2O3 co-doped silicate glasses

Viscosity and melting temperature of soda lime silicate glasses co-doped with Gd2O3 and Y2O3 measured using the rotating crucible viscometer, and derived on the basis of the Arrhenius Equation have been reported in our previous paper. To reveal the effect of substituting Y2O3 for Gd2O3 on the performance of soda lime silicate glass at high temperature, the free volume fraction and structure of soda lime silicate glass co-doped with Y2O3 and Gd2O3 were investigated. The results show that a small amount of Gd2O3 decrease the fraction of free volume of soda lime silicate melt, and then increase when the content above 0.5 mol%, while Y2O3 addition decrease the fraction of free volume. For FTIR spectra, doping of Gd2O3 and Y2O3 into glass causes the peak position of bands assigned to Si–O–Si asymmetric and symmetric stretching vibration move to lower wavenumber, and broadens the distribution of structural units. Raman spectra results show that Gd2O3 and Y2O3 result in the structural units with more bridging oxygen depolymerize to species with more non-bridging oxygen, consequently provide with more non-bridging oxygen and decrease the rigidity of glass structure. The behavior of soda lime silicate glasses doped with Gd2O3 and Y2O3 at high temperature can be elucidated by the change of the free volume and structure.