Thermoelectric Performance and Defect Chemistry in n-Type Zintl KGaSb4

The rise of high-throughput calculations has accelerated the discovery of promising classes of thermoelectric materials. In prior work, we identified the n-type Zintl pnictides as one such material class. To date, however, a lack of detailed defect calculations and chemical intuition has led the community to investigate p-type Zintls almost exclusively. Here, we investigate the synthesis, thermoelectric properties, and defect structure of the complex Zintl KGaSb4. We find that KGaSb4 is successfully doped n-type with Ba and has the potential for p-type doping with Zn. Our calculations reveal the fundamental defect structure in KGaSb4 that enables n-type and p-type doping. We find that Ba doped KGaSb4 exhibits high electronic mobility (~50 cm2V-1s-1) and near minimum lattice thermal conductivity (<0.5 Wm-1K-1) at 400 degrees C. Samples doped with 1.5% Ba achieve zT > 0.9 at 400 degrees C, promising for a previously unstudied material. We also briefly investigate the series of alloys between KGaSb4 and KAlSb4, finding that a full solid solution exists. Altogether our work reinforces motivation for the exploration of n-type Zintl materials, especially in tandem with high-throughput defect calculations to inform selection of effective dopants and systems amenable to n-type transport.