Electrical property enhancement and lattice thermal conductivity reduction of n-type Mg₃Sb_1.5Bi_0.5-based Zintl compound by In&Se co-doping

Mg₃Sb_1.5Bi_0.5-based Zintl compounds have attracted extensive attention as potential thermoelectric materials due to their earth-abundant elements. However, pure and intrinsic Mg₃Sb_1.5Bi_0.5 manifests a poor thermoelectric performance because of its low electrical conductivity of about 3 × 10² S/m at room temperature. In this work, In and Se co-doping was carried out to optimize the thermoelectric performance of n-type Mg₃Sb_1.5Bi_0.5-based material. The experimental results revealed that the carrier concentration and mobility of Mg₃Sb_1.5Bi_0.5 significantly increased after In and Se co-doping, leading to an improvement of power factor. Simultaneously, lattice thermal conductivity was significantly reduced due to the large mass difference between In and Mg. A maximum zT of 1.64 at 723 K was obtained for the Mg_3.17In_0.03Sb_1.5Bi_0.49Se_0.01 sample. And an average zT value of about 1.1 between 300 and 723 K was achieved, which insures its possible application at medium temperature range as a non-toxic and low-cost TE material.