Quartic anharmonicity and ultra‐low lattice thermal conductivity of alkali antimonide compounds M 3 Sb ( M = K, Rb and Cs)

Abstract

We investigate the role of the quartic anharmonicity in lattice dynamics and the thermal transport properties of the alkali antimonide compounds M3Sb (M = K, Rb and Cs) by using the self-consistent phonon theory combined with compressive sensing techniques. We found that the alkali-metal atoms in K3Sb, Rb3Sb and Cs3Sb have a strong quartic anharmonicity and play a crucial role in the lattice dynamic stability. Based on the above results, the thermal transport properties are estimated with the relaxation time approximation of Boltzmann transport equation, the calculated lattice thermal conductivity κL shows a remarkably low value at 300 K, which is 1.26, 0.63 and 0.52 Wm−1 K−1 for K3Sb, Rb3Sb and Cs3Sb, respectively. We have demonstrated the quartic anharmonicity of alkali antimonide compounds M3Sb (M = K, Rb and Cs) and studied their thermal transport properties, which has never been reported before, the ultra-low lattice thermal conductivity indicates that K3Sb, Rb3Sb and Cs3Sb are potential thermoelectric materials.