A Simple Chemical Guide for Finding Novel n-type Dopable Zintl Pnictide Thermoelectric Materials

Computations have predicted good thermoelectric performance for a number of Zintl phases when doped n -type. Combined with the successful experimental realization of n -type KGaSb 4 , KAlSb 4 , and Mg 3 Sb 2 with zT>1, this has fueled efforts to discover novel n -type dopable Zintl phases. However, a majority of Zintl phases exhibit strong proclivity toward p -type doping and prior successes in finding n -type dopable Zintls were largely serendipitous. Herein we use modern first-principles defect calculations to study trends in the dopability of Zintl pnictides and find that the average oxidation state of the anion is a useful chemical guide to identify novel n -type dopable phases. Specifically, we observe that Zintl pnictides with average oxidation of the anion near -1 are n -type dopable. The trend is mainly a consequence of the high formation energy of native acceptor defects ( e.g. cation vacancies) and the resulting absence of charge (electron) compensation. Using the oxidation state guide in conjunction with a descriptor of thermoelectric performance, we conduct a large-scale materials search and identify promising candidates that are n -type dopable.