Thermoelectric efficiency of intermetallic compound ZnSb

Two effects of an additional increase in the Hall density are revealed in the intermetallic semiconductor ZnSb doped with elements of groups I (copper, silver) and IV (lead, tin, germanium). The first effect is observed in the temperature range of 500–600 K in samples doped with impurities of both these groups. Additional doping is provided using a small additive of a Group-I element; it can be accompanied by the formation of acceptor states inside the band gap, the filling of which becomes efficient at high temperatures. The second effect occurs in doped samples at a temperature of about 600 K, independent of the acceptor additive composition and the hole density; in undoped samples it starts at approximately 400 K. This effect precedes the generation of intrinsic carriers. The intrinsic defects of the material can form localized states near the conduction-band bottom inside the band gap. Materials with optimal thermoelectric properties in a wide temperature range are obtained via double doping. The thermoelectric efficiency ZT of the samples with a low Cu concentration is not lower than 0.8 at 600 K and decreases by only 10% in the range of 575–725 K. In the Ag-doped samples this parameter exceeds 0.9 at 635 K.