Conducting grain boundaries enhancing thermoelectric performance in doped Mg2Si

Abstract

The thermoelectric properties of Pb doped Mg2Si, synthesized using reactive sintering employing spark plasma sintering, are investigated and are compared with other dopants reported in literature. While a moderate decrease in Seebeck coefficient and thermal conductivity is observed for 2 at. % of Pb doping in Mg2Si, a substantial enhancement in the material's thermoelectric figure-of-merit is observed, which is due to an enormous increase in its electrical conductivity. A brick-layer model is proposed to explain these results, wherein the inter-granular electronic conductivity is facilitated by Pb (or Mg2Pb) phases at grain boundaries, which is supported by microstructural evidences. This work was supported by CSIR-TAPSUN (Network Project NWP-54) programme entitled “Novel approaches for solar energy conversion under technologies and products for solar energy utilization through networking.” The authors are grateful to Radhey Shyam and N. K. Upadhyay for their technical and experimental support.