The thermal properties of SiO2-Al2O3-Y2O3 glasses were investigated within a temperature range of 25-800 degrees C. This found that glass with a composition of 24Y(2)O(3)center dot 21Al(2)O(3)center dot 55SiO(2) 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 xY(2)O(3)center dot 21Al(2)O(3)center dot(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 24Y(2)O center dot(3)21Al(2)O(3)center dot 55SiO(2) to have the maximum thermal conductivity of 1.7 W/m K at 800 degrees C. Glass systems incorporating yttria can therefore be considered suitable sintering additives for highly thermally conducting ceramics such as silicon nitride. (C) 2015 Elsevier B.V. All rights reserved.