The effect of substitution of Bi2O3 for alkali oxides on thermal properties, structure and wetting behavior of the borosilicate glass

The effect of substitution of Bi₂O₃ for alkali oxides in the borosilicate sealing glass on thermal properties, structure and wetting behavior of the borosilicate glass was studied. The thermal expansion coefficient (TEC) decreased with the substitution, however, the TEC varied little while the alkali oxides were completely consumed. The variation in glass transition temperature (T_g) and the FTIR results of the glasses indicated significant effect of Bi₂O₃ substitution on the glass structure, which caused a progressive conversion of BO₃ to BO₄ unit in the glass. The appropriate amount of Bi₂O₃ obviously improved the wetting performance of the borosilicate glass on Al₂O₃ substrate due to the high polarizability of Bi³⁺ ion.