Isotropic Conduction Network and Defect Chemistry in Mg3+δSb2-Based Layered Zintl Compounds with High Thermoelectric Performance

Thermoelectric performance in the layered Zintl phase n-type Mg3+delta(Sb,Bi)(2) is reported. Insertion of the excess Mg into the compounds is crucial for realizing n-type carrier transport with multivalley and isotropic character. An excellent ZT of 1.51 +/- 0.06 at 716 K is achieved in the sintered polycrystals at the composition of Mg3.2Sb1.5Bi0.49Te0.01.