Strong quartic anharmonicity, ultralow thermal conductivity, high band degeneracy and good thermoelectric performance in Na2TlSb
Tongcai Yue, Yinchang Zhao, Jun Ni, Sheng Meng, Zhenhong Dai
Abstract
Abstract We employ first-principles calculations combined with self-consistent phonon theory and Boltzmann transport equations to investigate the thermal transport and thermoelectric properties of full-Heusler compound Na 2 TlSb. Our findings exhibit that the strong quartic anharmonicity and temperature dependence of the Tl atom with rattling behavior plays an important role in the lattice stability of Na 2 TlSb. We find that soft Tl-Sb bonding and resonant bonding in the pseudocage composed of the Na and Sb atoms interaction is responsible for ultralow κ L . Meanwhile, the multi-valley band structure increases the band degeneracy, results in a high power factor in p-type Na 2 TlSb. The coexistence of ultralow κ L and high power factor presents that Na 2 TlSb is a potential candidate for thermoelectric applications. Moreover, these findings help to understand the origin of ultralow κ L of full-Heusler compounds with strong quartic anharmonicity, leading to the rational design of full-Heusler compounds with high thermoelectric performance.