Stable phosphate-based glass for low-temperature sealing applications: Effect of Si3N4 dopant

Phosphate glass is advantageous as a low temperature sealing material, especially in solar cells, micro-motor systems, vacuum engineering and the like, but the poor chemical stability restricts its wide application, especially in humid environments. To overcome this shortcoming, a certain proportion of silicon nitride is added to tailor the structural, chemical and thermal properties of phosphate glass. The results show that the addition of silicon nitride improves the water resistance and remarkably reduces the mass loss in humid environments from 60 to 3 wt% after 120 h. With the addition of silicon nitride, the softening temperature of glass is in the range of 330–372 °C. In particular, the coefficient of thermal expansion of phosphate glass can be tailored ranging from 14.9 × 10−6 K−1 to 17.4 × 10−6 K−1 by adjusting the content of silicon nitride, making it thermally compatible with various substrates. These findings provide useful information on the development of reliable low-temperature sealing glass.