SAE International Development of Mg 2 (SiSn) Thermoelectric Material for Automobile 2015-01-1695

As an appropriate material for automotive thermoelectric generators, which directly convert waste heat of exhaust gas into electricity, we have developed Mg 2 (Si 1-x Sn x ) thermoelectric materials with high thermoelectric performance. The performance is evaluated with the dimensionless figure of merit (ZT) , and the ZT has been improved through the development of the fabrication process and the investigation of the optimum composition and dopant element. A novel liquid-solid reaction synthesis method incorporating hotpressing for the sample fabrication was effective in reducing the thermal conductivity. The n-type Mg 2 (Si 0.50 Sn 0.50 ) doped with Sb attained a high ZT of 1.1 at 620 K. The p-type Mg 2 (Si 0.25 Sn 0.75 ) doped with Li and Ag simultaneously achieved a ZT of 0.3 at 600 K. The effective maximum power of n-type thermoelectric element and that of p-type were calculated with the thermoelectromotive force and the mean resistivity. The calculated power generation showed the possibility of improving fuel consumption in automobiles.