Effects of Bi and Sb doping on the thermoelectric performance of n-type quaternary Mg2.18Ge0.1Si0.3Sn0.6 materials

Mg2.18(Si0.3Ge0.1Sn0.6)1-yXy (X = Bi, Sb; y = 0, 0.02, 0.06) quaternary solid solutions were synthesized via solid state reaction after ball milling followed by hot-pressing. The influences of Bi and Sb doping on its thermoelectric (TE) properties, such as thermal conductivity, Seebeck coefficient, and electrical conductivity were discussed in the temperature range of 300-800 K. Our results show that Bi and Sb are effective in n-type doping. The results illustrate that the Seebeck coefficient decreases, whereas electrical conductivity increases with increasing tem-perature for undoped compositions. However, the electrical conductivity decreases in a metal-like behavior for the doped sample. Additionally, the samples doped with Bi0.02 and Sb0.02 show enhanced TE properties as compared to those doped with Bi0.06 and Sb0.06, respectively. A maximum ZT of 1.28 is achieved in the sample doped with Sb0.02.