The equivalent and aliovalent dopants boosting the thermoelectric properties of YbMg2Sb2

Antimony-based Zintl compounds AM 2 Sb 2 (A=Ca, Sr, Ba, Yb, Eu; M=Mg, Zn, Cd, Mn), which enable a broad range of manipulation on electrical and thermal transport properties, are considered as an important class of thermoelectric materials. Phonon and carrier transport engineering were realized in YbMg 2 Sb 2 via equivalent and alio-valent substitution of Zn and Ag, respectively. The room-temperature thermal conductivity reduces from 1.96 to 1.15 W m −1 K −1 for YbMg 2- x Zn x Sb 2 due to the mass and strain fluctuation through the formation of the absolute solid solution of YbMg 2 Sb 2 -YbZn 2 Sb 2 . Furthermore, the carrier concentration has been further optimized by Ag doping (from 0.42×10 19 to 7.72×10 19 cm −3 at room temperature), and thus the electrical conductivity and the power factor are enhanced effectively. The integrated aspects make the dimensionless figure of merit ( zT ) reach 0.48 at 703 K, which is 60% higher than the pristine YbMgZnSb 2 sample.