Promising thermoelectric performance in CaAgP with intrinsic Ag vacancies
Robert J. Quinn, Jan‐Willem G. Bos
Abstract
Semimetals have recently emerged at the forefront of contemporary thermoelectrics research. In this paper, we show that the candidate Dirac semimetal CaAgP forms with a stable CaAg0.9P composition. Intentionally, Ag-deficient CaAg0.9P shows a promising thermoelectric figure of merit, achieving zT = 0.43 at 660 K. This derives from moderate power factors, S2/ρ = 1.25 mW m−1 K−2, and a low lattice thermal conductivity, κlat = 1.2 W m−1 K−1. The thermoelectric properties of CaAg0.9P are consistent with that of a small bandgap semiconductor. High levels of doping are key to suppressing bipolar transport, enabling promising zT values, despite the low ∼0.2 eV bandgap. Unusually, the onset of bipolar transport coincides with a transition to a more electrically resistive state, indicating a fundamental change in electronic properties at high temperature.