Thermoelectric properties of Sc- and Y-doped Mg_2Si prepared by field-activated and pressure-assisted reactive sintering

摘要

Sc- and Y-doped-Mg_2Si samples were reactively sintered by the field-activated and pressure-assisted synthesis (FAPAS) method. The incorporation of these rare-earth elements in this silicide resulted in an n-type semiconductor. The addition of Sc and Y had no discernable effect on the lattice constant of Mg_2Si. The average grain size of the Y-doped Mg_2Si was about 2 μm, which was smaller than that of the sintered pure Mg_2Si. The power factor of samples doped with 2500 ppm Sc was consistently higher than that of pure Mg_2Si in the temperature range of 300-550 K. Similarly, the power factor of 2000 ppm Y doped Mg_2Si samples was higher than that of pure Mg_2Si over the temperature range of 300-675 K; the highest value being about 2.2 x 10~(-3) W m~(-1) k~(-2) at 468 K. This value is about two times that of the undoped Mg_2Si at the same temperature. The thermal conductivity of Mg_2Si doped with 2000 ppm Y was 80% of that of pure Mg_2Si. The highest figure of merit (ZT) for the Y doped (2000 ppm) samples was 0.23 at 600 K which was higher by a factor of 1.6 than the corresponding value of pure Mg_2Si at the same temperature. The results demonstrate the benefits of doping of Mg_2Si with Sc and Y in enhancing its thermoelectric properties.