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

抄録

  We have investigated the thermoelectric properties of Na-doped Mg₂Si_0.25Sn_0.75 solid solutions prepared by liquid-solid reaction and hot-pressing methods. Na doping was carried out by mixing sodium acetate (CH₃COONa) 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 Mg₂Si_0.25Sn_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 Mg₂Na_0.020Si_0.25Sn_0.75 sample at 500 K. The dimensionless figure of merit ZT reached 0.17 at 450 K for all Na-doped samples.