Effect of B2O3 addition on the thermal properties and density of barium phosphate glasses

Variations in glass transition temperature, onset of crystallization, thermal expansion coefficient, density and molar volume with B2O3 concentration were studied in a series of xB2O3–(100 − x)Ba(PO3)2 glasses with 0–10 mol% B2O3. DTA analysis and isothermal treatments for powdered glass samples reveal that ⩾7.5 mol% B2O3 addition suppresses surface crystallization during softening process. Raman spectroscopy suggests that the properties are related to the glass structure consisting of PO4 Q2 units with diborate and PO4–BO4 groups.