HIGH THERMAL-EXPANSION PHOSPHATE-GLASSES .2.

The chemical durability of phosphate glasses can be improved by adding oxides such as Al2O3 or PbO. The general compositions investigated were M2O-MO-M2O3-P2O5, where M2O = Ag2O, Na2O, or K2O, MO = BaO or PbO, and M2O3 = Al2O3 or Fe2O3. Ag2O and PbO resulted in important improvements in chemical durability while maintaining high thermal expansion. Many glass compositions in the system had a thermal expansion coefficient of 180 to 210 x 10(-7)/deg C and a dissolution rate in deionised water at 70-degrees-C of < 10(-7) g/cm2 min. Some of these compositions appeared to be good candidates for sealing glasses.