Composition dependent thermoelectric properties of sintered Mg 2Si 1− xGe x ( x = 0 to 1) initiated from a melt-grown polycrystalline source

Abstract

Fabrication of Mg 2Si 1− x Ge x ( x = 0–1.0) was carried out using a spark plasma sintering technique initiated from melt-grown polycrystalline Mg 2Si 1− x Ge x powder. The thermoelectric properties were evaluated from RT to 873 K. The power factor of Mg 2Si 1− x Ge x with higher Ge content ( x = 0.6–1.0) tends to decrease at higher temperatures, and the maximum value of about 2.2 × 10 − 5 Wcm − 1 K − 2 was observed at 420 K for Mg 2Si and Mg 2Si 0.6Ge 0.4. The coexistence of Si and Ge gave rise to a decrease in the thermal conductivity in the Mg 2Si 1− x Ge x . The values close to 0.02 Wcm − 1 K − 1 were obtained for Mg 2Si 1− x Ge x ( x = 0.4–0.6) over the temperature range from 573 to 773 K, with the minimum value being about 0.018 Wcm − 1 K − 1 at 773 K for Mg 2Si 0.4Ge 0.6. The maximum dimensionless figure of merit was estimated to be 0.67 at 750 K for samples of Mg 2Si 0.6Ge 0.4.