Achieving n-type Conduction in AMg2Sb2 (A = Yb, Eu, Ca, Sr, Ba) Zintl Phases

Zintl phases have been theoretically predicted to be promising n-type thermoelectric materials, which, however, are very difficult to achieve experimentally, owing to the existence of intrinsic negatively charged defects. Here, taking the representative AMg ₂Sb ₂ ( A= Yb, Eu, Ca, Sr, Ba) as the examples, we theoretically found that the defect formation energy of negatively charged A and Mg vacancies near the conduction band minimum are lower than other types of defects, playing as the vital role in hindering the experimental realization of n-type conduction. Experimentally, by suppressing the formation of A and Mg vacancies, n-type conduction can be successfully achieved in all the studied AMg ₂Sb ₂ Zintl phases. Moreover, taking EuMg ₂Sb ₂ as an example, its n-type thermoelectric performance can be significantly improved through further isoelectronic alloying and donor doping. This work highlights the importance of understanding intrinsic defects as a guide for the development of n-type thermoelectric Zintl phases.