Synthesis of p-type Mg2Si1-xSnx with x=0-1 and optimization of the synthesis parameters

Mg2Si is a promising thermoelectric material in the mid-temperature region 500 - 800 K. Development of Mg2Si based thermoelectric generators requires both good n-and p-type materials. While the thermoelectric properties ntype Mg-2(Si, Sn) materials are good, those of the corresponding p-type are not as much. Therefore, optimizing p-type solid solution of magnesium silicide and magnesium stannide is highly desired. We employ high energy ball milling for efficient synthesis of p-type Mg-2(Si, Sn) and investigate the effect of milling time, sintering temperature, and holding time on the thermoelectric properties of p-type Mg2Si1-xSnx with x = 0-1. We can show the synthesis of ptype Mg-2(Si, Sn) for the whole compositions using Li as a dopant. We have also studied the effect of the synthesis parameters (milling time, sintering temperature, and holding time) on the phase purity, functional homogeneity and thermoelectric properties. The phase purity increases with longer milling time. The functional homogeneity decreases with higher sintering temperature and longer holding time. The optimum synthesis condition for x = 0.6 leads to zT(max) similar to 0.6 at 700 K, which is one of the highest value reported for p-type Mg-2(Si, Sn).