Thermoelectric Properties of p- and n-Type Si-Ge Dense Bodies Formed by Pulse-Current Sintering of Their Gas-Atomized and Pulverized Powders

Abstract

Both p- and n-type Si0.8Ge0.2 powders were prepared by gas atomization of a mixture of Si and Ge with the addition of B or P. A part of the gas-atomized powders was further pulverized by ball-milling for 10h in Ar. Then, dense bodies were formed from both the as-atomized and pulverized powders by pulse-current sintering. The thermoelectric properties such as the thermal conductivity, electric resistivity and Seebeck coefficient of the dense bodies were determined from room temperature to 1073K, followed by the evaluation of the figure of merit (ZT). The thermal conductivities of p- and n-type fine-grained Si-Ge from pulverized powders were 8 and 10% lower on average in the temperature range of 300-1073K, respectively, than those of the as-atomized powders. However, this phenomenon was accompanied with an increase in electric resistivity due to the reduced grain size and increased oxygen content, resulting in the decrease in ZT by 13 and 8% for p- and n-type Si-Ge, respectively. The ZT of n-type Si-Ge exceeded that of p-type because of the high Seebeck coefficient of n-type samples. Finally, the largest ZT value of 0.66 was obtained for the Si-Ge dense body from n-type gas-atomized powder. It was found that the application of the gas-atomized powder for fabricating Si-Ge sintered body has the advantage of the reduction in oxygen content and resistivity compared to the case of the pulverized powders.