Thermoelectric figure of merit of impurity doped and hot-pressed magnesium silicide elements

Intermetallic magnesium compounds and their solid solutions have been known as potentially promising thermoelectric materials for the middle temperature power generation application. Spark plasma sintering and subsequent hot-pressing were used to make the impurity doped Mg₂Si thermoelectric elements. The temperature dependence of thermoelectric properties such as the Seebeck coefficient, electrical conductivity and thermal conductivity was measured to clarify the optimum performance of sintered Mg₂Si elements. Moreover, the semiconducting properties such as Hall mobility and carrier concentration were measured by the van der Pauw method. In the case of 0.6 at%Sb doped n-type sintered elements the maximum power factor was obtained 3.0×10^-3 W/mK² at 773 K and the figure of merit was 0.87×10^-3 K^-1 and dimensionless figure of merit ZT was 0.67. Concerning p-type Mg₂ Si elements, silver doped, sintered Mg₂Si was made by the same procedure as n-type antimony doped sintered elements. The junction of a Mg₂Si element with the electrode was also studied to check the junction resistance between the thermoelectric element and the electrode. It was found that Fe was suitable as an electrode