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

Mg
₂
Si and Mg
₂
Si incorporating oxides such as Al
₂
O
₃
, ZrO
₂
, SnO
₂
, ZnO, B
₂
O
₃
and CuO were formed by using a spark-plasma sintering (SPS) technique. The "oxide-incorporated" Mg
₂
Si samples exhibited the formation of voids and also clusters of oxide materials. The effects of oxide incorporation into Mg
₂
Si 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 Mg
₂
Si. In the cases of the samples of Mg
₂
Si that incorporated SnO
₂
, ZnO, ZrO
₂
and Al
₂
O
₃
, the observed power factors showed no significant temperature dependence, with values comparable to those observed for pure Mg
₂
Si at about 2 times 10
^-5
W/cmK
²
. The incorporation of SnO
₂
or ZnO improved the lattice thermal conductivity over the whole measured temperature range when compared with a pure Mg
₂
Si sample. The observed deviations in the values of the figures-of-merit between the SnO
₂
or ZnO-incorporated Mg
₂
Si and the pure Mg
₂
Si (without the oxide) were observed as being rather small, with no remarkable dissidence in the measured values. It was realized that the SnO
₂
- and the ZnO-incorporated Mg
₂
Si samples exhibited thermal conductivity values that were more than 20 % lower than that of pure Mg
₂
Si at around 773 K