Effects of Ag-Doping on Thermoelectric Properties of Ca(2−x)AgxSi Alloys

Ca (2−x) Ag x Si (0 ≤ x ≤ 0.1) with 47.5% excess of Ca alloys were fabricated by melting in a tantalum tube and hot pressing technique. Phase structures of the samples were studied by means of x-ray diffraction. The electrical conductivity and Seebeck coefficient of Ca (2−x) Ag x Si alloys were studied in the temperature range of 300–873 K. The electrical conductivity of the Ag-doped samples increases within the whole test temperature range. All samples show p -type semiconductor behavior. The electrical conductivity decreases with increasing temperature from 300 K to 873 K, which is typically observed for a degenerate semiconductor. Compared with the undoped samples, Ag-doping ( x = 0.04–0.1) results in decreases of Seebeck coefficient, especially Ca (2−x) Ag x Si with x = 0.1. The thermal conductivity of the doped samples gradually increases with increasing the Ag-doping content. The Ca (2−x) Ag x Si with x = 0.02 sample exhibits the lowest thermal conductivity within the whole test temperature range. The ZT values of Ca (2−x) Ag x Si with x = 0.02 sample have an enhancement in the temperature range of 300–873 K by contrast with those of the Ca 2 Si sample. The maximum ZT value is 0.16 at 837 k, which is observed for the Ca (2−x) Ag x Si with x = 0.04 sample.