In this study, we explored the thermal and mechanical properties of a SiO₂-B₂O₃-ZnO-K₂O-Na₂O (SBZKN) glass composition for potential use in vacuum insulated glass windows. The glass's physical properties were controlled through the mixed alkali effect, with K₂O and Na₂O serving as network modifiers, maintaining a fixed total of 20%. The SBZKN composition powder vitrified below 1000 °C. Varying the K₂O content from 0% to 20% resulted in reduced density and hardness of the glass specimen. DTA analysis indicated decreasing glass transition temperature (Tg) and crystallization temperature (Tp) with higher K₂O content, reaching a minimum at 10%. The coefficient of thermal expansion peaked at 10% K₂O content, and thermal conductivity was lowest with 15% K₂O content. Heating a cube-shaped glass specimen (700 to 800 ℃) caused semicircular spreading due to glass viscosity. Contact angle between spread glass and substrate decreased with temperature but generally increased with K₂O content. At 800 ℃, all specimens showed excellent wetting with contact angles of 44° to 72°. This study provides evidence of alkali mixing effects on thermal and mechanical properties, contributing vital data for future vacuum insulated glass window design and development.

Keywords: Vacuum-insulated-glass, Spacer, SBZKN-glass, Mixed-alkali-effect.