Preparation of Mg2Si based thermoelectric nanomaterials by low-temperature reaction

High-purity Mg2Si nanopowders were prepared from MgH2 powder and Si powder by low-temperature reaction at 623K in a tube furnace. The mole ratio of MgH2 and Si was 1.95:1 and the dwelling time was 20h. This process decreased the oxidation and volatilizing of Mg significantly. The detrimental MgO to the thermoelectric performance was reduced, and Mg2Si with fine grain about 50nm was obtained. The synchronous densification of Pr-doped Mg2Si0.8Sn0.2 was achieved in a Field-activated and Pressure-assisted Synthesis (FAPAS) apparatus at 973K and 80MPa for 15min. With increasing Pr content, the electric conductivities of Mg2Si0.8Sn0.2 appeared to have a declining trend after an initial ascent. For the Mg2Si0.8Sn0.2 doped with 0.002mol Pr, the maximum values of the electric conductivity and power factor were 2.4×103 S m-1 and 1.38×10-3 Wm-1K-2, respectively, which were about 2.5 and 1.53 times of that of the un-doped Mg2Si0.8Sn0.2, respectively.