Probing Efficient N-Type Lanthanide Dopants for MgSb Thermoelectrics.

The recent discovery of n-type MgSb thermoelectrics has ignited intensive research activities on searching for potential n-type dopants for this material. Using first-principles defect calculations, here, a systematic computational screening of potential efficient n-type lanthanide dopants is conducted for MgSb. In addition to La, Ce, Pr, and Tm, it is found that high electron concentration (≳10 cm at the growth temperature of 900 K) can be achieved by doping on the Mg sites with Nd, Gd, Ho, and Lu, which are generally more efficient than other lanthanide dopants and the anion-site dopant Te. Experimentally, Nd and Tm are confirmed as effective n-type dopants for MgSb since doping with Nd and Tm shows higher electron concentration and thermoelectric figure of merit than doping with Te. Through codoping with Nd (Tm) and Te, simultaneous power factor improvement and thermal conductivity reduction are achieved. As a result, high values of ≈1.65 and ≈1.75 at 775 K are obtained in n-type MgNdSbTe and MgTmSbTe, respectively, which are among the highest values for n-type MgSb without alloying with MgBi. This work sheds light on exploring promising n-type dopants for the design of MgSb thermoelectrics.