Characterization of oxide-incorporated n-type Mg2Si prepared by a spark plasma sintering method

Mg₂Si and Mg₂Si incorporating oxides such as Al₂O₃, ZrO₂, SnO₂, ZnO, B ₂O₃ and CuO were formed by using a spark-plasma sintering (SPS) technique. The "oxide-incorporated" Mg₂Si samples exhibited the formation of voids and also clusters of oxide materials. The effects of oxide incorporation into Mg₂Si were investigated in an attempt to identify oxides that exhibit lower thermal conductivity but an equal power factor and figure-of-merit when compared with pure Mg₂Si. In the cases of the samples of Mg₂Si that incorporated SnO₂, ZnO, ZrO₂ and Al₂O₃, the observed power factors showed no significant temperature dependence, with values comparable to those observed for pure Mg₂Si at about 2 times 10^-5 W/cmK². The incorporation of SnO₂ or ZnO improved the lattice thermal conductivity over the whole measured temperature range when compared with a pure Mg₂Si sample. The observed deviations in the values of the figures-of-merit between the SnO₂ or ZnO-incorporated Mg₂Si and the pure Mg₂Si (without the oxide) were observed as being rather small, with no remarkable dissidence in the measured values. It was realized that the SnO₂- and the ZnO-incorporated Mg₂Si samples exhibited thermal conductivity values that were more than 20 % lower than that of pure Mg₂Si at around 773 K