Unravelling the Ultralow Thermal Conductivity of Ternary Antimonide Zintl Phase RbGaSb2: A First-principles Study

Abstract

The recent discovery of antimonide based Zintl phase compounds has sparked the research in finding high-performance thermoelectric materials. In present study, a ternary antimonide Zintl phase RbGaSb₂ is investigated using First-principles calculations. A good agreement observed between our computed results, such as lattice parameter and thermal conductivity, with the experimental report validating our theoretical framework. A direct band gap of 1.17 eV is obtained using Tran Blaha modified Becke Johnson approach. The negative value of Seebeck coefficient indicates its n-type character. We purpose a strategy for enhancing power factor via carrier concentration optimization. The calculated results reveal the anisotropic transport properties. The intrinsic ultralow lattice thermal conductivity about 0.094 Wm^-1K^-1 along the x-direction, and 0.019 Wm^-1K^-1 along z-direction at room temperature is obtained. The ZT value can reach 0.90 (in x-direction) and 0.85 (in z-direction) for n-type doping at 900 K, indicating RbGaSb₂ as promising thermoelectric material.