Synthesis of Magnesium Silicide Compounds by a Liquid-solid Phase Reaction Method and their Thermoelectric Properties

Abstract

Dimagnesium silicide (Mg₂Si) is a promising thermoelectric material for energy conversion over intermediate temperature range (300 to 600°C). This material has advantages of the constituent elements in abundance in the earth's crust and of the nontoxicity of its processing by-products as an environmental symbiosis thermoelectric semiconductor. However, there are few research reports about this material for improving thermoelectric performance because of difficulty of its synthesis. In this study, Mg₂Si was synthesized from Mg and Si powders by a liquid-solid phase reaction (LSPR) method, which is effective in synthesizing a compound from the two elements having sufficiently different melting points. The powder synthesized by LSPR method was compacted and then sintered by a pulse discharge sintering (PDS) process. Influence of sintering conditions on thermoelectric properties of Mg₂Si was investigated. The thermoelectric properties of each sintered sample were measured at temperature of RT to 600°C. The thermoelectric properties of the sintered sample were, however, strongly affected by the sintering temperature and/or the sample density. The sample sintered at 730°C for 30 min under 60 MPa had the maximum dimensionless figure of merit of 0.27 at 516°C. This value is higher than the previous report.