Physical properties of pseudo quaternary Na2B4O7 - SiO2 - MoO3 - Dy2O3 glasses

Pseudo quaternary Na2B4O7-SiO2-MoO3-Dy2O3 glasses with various concentrations of Dy2O3 were synthesized and characterized by ultrasound, DTA and X-ray diffraction (XRD). It was found that, the density, the molar volume and the elastic moduli increased while the ultrasonic velocities and the packing density decreased with increasing of Dy2O3 concentration. The lower values of the radii and the bond length of B2O3, compared to those of Dy2O3, decreased the interatomic forces between the reactant glass forming cations and oxygens inside the glassy network. Accordingly, this will increase the molar volume and in the same time will decrease the average cross-link density, the ultrasonic velocities, the glass transition temperature and the thermal stability. Also, this may result in a high density glass sample which will increase the elastic moduli. Based on Lasocka's model, a good correlation between the temperature of both glass transition (T-gl) and crystallization peak (T-pc)was observed.