Characterization of thermal conductivity of SiO2–Al2O3–Y2O3 glasses

• SiO2–Al2O3–Y2O3 glasses for sintering additive in ceramics.
• The glasses shows increase in thermal conductivity at high temperature.
• Glass system of SiO2–Al2O3–Y2O3 could be improved with the overall thermal conductivity of ceramics at high temperature.

The thermal properties of SiO2–Al2O3–Y2O3 glasses were investigated within a temperature range of 25–800 °C. This found that glass with a composition of 24Y2O3·21Al2O3·55SiO2 exhibits a thermal conductivity of 1.04 W/m K at room temperature, and thermal conductivity increases with temperature due to an increase in the amount of bridging oxygen. The thermal conductivity of glasses with a composition of xY2O3·21Al2O3·(79-x)SiO2, on the other hand, decreased with an increase in either the Y2O3 content or Al2O3/SiO2 ratio. This decrease in thermal conductivity was analyzed with respect to the decrease in phonon mean free path resulting from the increased non-bridging oxygen content, which revealed 24Y2O3·21Al2O3·55SiO2 to have the maximum thermal conductivity of 1.7 W/m K at 800 °C. Glass systems incorporating yttria can therefore be considered suitable sintering additives for highly thermally conducting ceramics such as silicon nitride.