Thermoelectric Properties of Na-doped Mg₂Si_0.25Sn_0.75

Abstract

We have investigated the thermoelectric properties of Na-doped Mg 2 Si 0.25 Sn 0.75 solid solutions prepared by liquid-solid reaction and hot-pressing methods.Na doping was carried out by mixing sodium acetate (CH 3 COONa) into the starting materials Mg (nominal purity: 99.9 %), Sn (99.999 %) granules, and Si powder (99.9999 %).The Na-doped samples had p-type conductivity with positive signs of Seebeck and Hall coefficients.Furthermore, hole concentrations increased rapidly with an increase in the amount of Na doping.These results revealed that the Na atoms acted as acceptors in Mg 2 Si 0.25 Sn 0.75 .The Seebeck coefficient of Na-doped samples showed positive values between 300 and 750 K.A maximum power factor of 0.88 × 10 -3 WmK -2 was observed for the Mg 2 Na 0.020 Si 0.25 Sn 0.75 sample at 500 K. The dimensionless figure of merit ZT reached 0.17 at 450 K for all Na-doped samples.