Manipulation of hole and band for thermoelectric enhancements in SrCd2Sb2 Zintl compound

Abstract Exploration of novel thermoelectric materials is of great significance for thermoelectric development. AB2X2 Zintl compounds with rich chemical constitute, have been frequently demonstrated as promising thermoelectric materials because of their low lattice thermal conductivity and tunable band structure. This motivates the current work to focus on the experimental evaluation of thermoelectric potential on SrCd2Sb2, a new member of Zintl compounds. Na-substitution at Sr site leads to an effective increase in Hall carrier concentration from ~ 2.6 × 1018 to ~ 1.1 × 1020 cm−3, enabling a well estimation of transport properties by a single parabolic band (SPB) model with acoustic scattering. This reveals a multi-band transporting behavior in SrCd2Sb2 thermoelectrics with heavy-doping or elevated-temperature, ensuring a 150%-improvement in thermoelectric figure of merit (zT). On the basis of model, a peak zT of ~ 1.4 is achievable by minimizing lattice thermal conductivity, which not only demonstrates this compound as a promising thermoelectric material, but also provides a guidance for further advancements.