Thermoelectric properties of Zintl compound Ca_{1- x}Na_xMg₂Bi_1.98

Motivated by good thermoelectric performance of Bi-based Zintl compounds Ca_{1- x}Yb_xMg₂Bi_y, we further studied the thermoelectric properties of Zintl compound CaMg₂Bi_1.98 by doping Na into Ca as Ca_{1- x}Na_xMg₂Bi_1.98 via mechanical alloying and hot pressing. We found that the electrical conductivity, Seebeck coefficient, power factor, and carrier concentration can be effectively adjusted by tuning the Na concentration. Transport measurement and calculations revealed that an optimal doping of 0.5 at. % Na achieved better average ZT and efficiency. The enhancement in thermoelectric performance is attributed to the increased carrier concentration and power factor. The low cost and nontoxicity of Ca_1-xNa_xMg₂Bi_1.98 makes it a potentially promising thermoelectric material for power generation in the mid-temperature range.