Development of Mg ₂ (SiSn) Thermoelectric Material for Automobile

As an appropriate material for automotive thermoelectric generators, which directly convert waste heat of exhaust gas into electricity, we have developed Mg₂(Si_1-xSn_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 Mg₂(Si_0.50Sn_0.50) doped with Sb attained a high ZT of 1.1 at 620 K. The p-type Mg₂(Si_0.25Sn_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.