Room temperature high thermoelectric performance of Bi-based full-Heusler compounds CsxRb[formula omitted]Bi with strong anharmonicity

Abstract

Bismuth-based compounds have been identified as a class of promising candidates for the realization of high-performance thermoelectrics, derived from their exceptional electrical conductivity and intrinsic low lattice thermal conductivity κL. Here, we employed first-principles calculations, self-consistent phonon theory, and compressive sensing technique in conjunction with the Boltzmann transport equation to investigate the anharmonic thermoelectric properties of full-heusler bismuth compounds CsxRb3−xBi. As the Cs content increases, the κL of CsxRb3−xBi decreases due to impurity scattering effects, and then increases. Among them, at 300 K, Rb3Bi has the largest κL of 0.69 Wm−1K−1, while Cs2RbBi has the smallest κL of 0.45 Wm−1K−1, both of which are lower than the κL of traditional bismuth-based thermoelectric materials. The ultralow κL originates from the strong lattice anharmonicity. In addition, the coexistence of high dispersion and flat band edges leads to high thermoelectric power factor at optimal doping concentration. As a result, the largest thermoelectric figure of merit ZT values of 2.59 (4.19) at 300 (500) K were obtained for CsRb2Bi at optimal hole doping level. These findings suggest that CsxRb3−xBi compounds are superior for thermal management and thermoelectric applications.