Abstract
Si is a very promising thermoelectric conversion material because it is inexpensive, non-toxic, and exists in large quantities on the earth. However, the ZT values are low due to the very high thermal conductivity. Previously, Y. Ashida et al. achieved a maximum ZT of 0.43 at 973 K in an excessively P-doped Si system with reduced thermal conductivity due to localized Si–P nanoprecipitates and defects. Alloying Si and Ge is known to cause a ignificant decrease in thermal conductivity due to alloy scattering. Therefore, in this study, we aimed to further improve the performance by adding Ge to this Si–P system. Excessively P-doped Si-Ge samples were prepared by arc melting, ball milling, and SPS procedures to evaluate thermoelectric properties. In the system with 5% Ge, ZT increased significantly to 0.67 at 973 K, but there was little change after 10%. The fact that ZT did not increase significantly with the addition of more than 10% Ge is thought to be due to the fact that electron transport is hindered by alloy cattering and the lower solid solution limit of P in Si-Ge.
