Optimized nanostructure and thermoelectric performances of Mg2(Si0.4Sn0.6)Sbx solid solutions by in situ nanophase generation

The Mg2Si-based materials have been regarded as the promising and environment-friendly thermoelectric materials at the middle temperature. In this paper, the n-type Mg2(Si0.4Sn0.6)Sbx (0 ≤ x ≤ 0.02) solid solutions were successfully obtained by twice mechanical alloying (MA) and spark plasma sintering (SPS) process, namely the method twice MA + SPS. This work revealed that the dimensionless figure of merit ZT was significantly enhanced due to the nanophase uniformly dispersed in the fine-grained and the increase of the grain boundaries reducing the lattice thermal conductivities. Meanwhile, the nanostructuring and Sb-doping improved electrical performance for Mg2(Si0.4Sn0.6)Sbx (0 ≤ x ≤ 0.02) samples. The highest ZT value up to 1.40 at 673 K was obtained for Mg2(Si0.4Sn0.6)Sb0.018 sample.