SrCuP and SrCuSb Zintl phases as potential thermoelectric materials

Abstract

We report the investigation of the thermoelectric properties of SrCuX (X = P or Sb), combining experiments and DFT calculations, for the first time for SrCuP. These two compounds were recently highlighted by our high-throughput calculations for screening new thermoelectric materials. These calculations showed that these compounds are stable and non-metallic, and so suitable for thermoelectric applications. They were synthesized in the present work and our experimental results confirm the non-metallic character of these two compounds, which is favorable for thermoelectricity. The crystal structure of the materials is depicted within the Zintl model, showing graphene-like CuX layers promoting the electronic transport. High charge carriers mobilities (μ=30 cm2 V−1.s−1 in SrCuP, μ=200 cm2 V−1.s−1 in SrCuSb at room temperature) and low effective density of states masses (m*=0.7me for SrCuP, m*=0.4me for SrCuSb) were therefore determined. Moreover, despite a quite simple crystal structures, low lattice thermal conductivities were measured (λph<3.3 W.m−1. K−1 for both compound), which is favorable for thermoelectricity. Explanations of this result are provided by first-principles calculations of the vibrational properties. Promising values of the thermoelectric figure of merit ZT = 0.20 (X = P) at 600 K and ZT = 0.14 (X = Sb) at 650 K were finally measured in the pristine compounds. These values could probably be improved by doping.