Effect of Composition Adjustment on the Thermoelectric Properties of Mg₃Bi₂-Based Thermoelectric Materials

Thermoelectric materials are widely used in refrigeration chips, thermal power generation, catalysis and other fields. Mg₃Bi₂-based thermoelectric material is one of the most promising thermoelectric materials. Herein, the Mg₃Bi₂-based samples were prepared by high temperature synthesis, and the influence of Mg/Sb content on the electrical transport properties and semi-conductivity/semi-metallicity of the materials has been studied. The results indicate that the efficiency of introducing electrons from excess Mg prepared by high temperature synthesis is lower than that introduced by ball milling, due to the high vapor pressure of Mg. The doping of Sb/Te at the Bi site would make it easier for the material to change from p-type conduction to n-type conduction. With the increase in Mg content, the semi-conductivity of the material becomes weaker, the semi-metallicity becomes stronger, and the corresponding conductivity increases. With the increase in Sb content, the samples exhibit the opposite changes. The highest power factor of ~1.98 mWm^-1K^-2 is obtained from the Mg_3.55Bi_1.27Sb_0.7Te_0.03 sample.