Effects of Alkali Ratios on Alkali Barium Glasses for Compression Sealing

Alkali barium glasses of the system SiO2, Al2O3, LiO2, K2O, Na2O, and BaO were produced using high-purity powders by the melt-quench technique to evaluate the suitability of these glasses for hermetic sealing. Six different glasses with varying Na2O and K2O content were produced. Although both Na and K are alkali elements, their different ionic radii and densities result in different effects on the glass network structure. As a result, they have caused changes in the properties of the glass, leading to alterations in the glass-metal interface as well. Although the total Na2O + K2O content of the glasses was maintained at 15 wt%, the Na2O/K2O ratio was varied to see the effect of compositional variation on the properties of the glasses produced. In this study, it was observed that as the Na2O/K2O ratio increases, properties such as density, Tg, and chemical durability of the alkali barium glass decrease, while CTE increases. Glass pellets, prepared from the glass powders, were used for sealing with 304 stainless steels at different sealing profiles under argon gas. The results revealed that the sealing profile and the alkali ratios (Na2O/K2O) of the glass have a profound effect in the microstructure and the interface characteristics of the compression sealing developed between the alkali barium glass and 304 stainless steels.