Triaxial strain enhanced thermoelectric performance and conversion efficiency in Tl3TaSe4

Abstract

Thermoelectric (TE) materials have garnered significant attention due to their potential in converting waste heat into useful electrical energy. Strain engineering has emerged as a promising strategy for tailoring the properties of materials, offering opportunities to optimize TE performance. In this study, we employ first-principles calculations to investigate the electronic and thermal transport properties of cubic Tl3TaSe4 under triaxial strain. Our results demonstrate that tensile strain can reduce the effective mass of carriers and contribute to high carrier mobility. The phonon calculation and AIMD simulation reveal excellent dynamic stability and thermal stability of Tl3TaSe4 both with and without strain. The red shift phenomenon of phonon vibration modes and the higher portion of phonon DOS in the low frequency region indicate that tensile strain enhances the anharmonicity of Tl3TaSe4. In addition, triaxial tensile strain can effectively reduce the heat capacity, group velocity, and phonon lifetime, while enhancing the anharmonicity of Tl3TaSe4, which contributes to the lower κl. Compared to the condition without strain, the room temperature κl of Tl3TaSe4 under 1 % and 2 % tensile strain is reduced by about 43 % and 79 %, respectively. Furthermore, the tensile strain exhibits a positive enhancement effect on the ZT value of Tl3TaSe4. At 700 K, the optimal ZT values of p-type and n-type Tl3TaSe4 under 2 % tensile strain are 1.31 and 0.94, respectively, which are three times higher than that of 0.4 and 0.33 without strain. Finally, the TE conversion efficiency of Tl3TaSe4 under 2 % tensile strain is 6.8 %, which is higher than BiCuSeO and α-Cu2+xSe, and comparable to SnSe. Our results demonstrate the effectiveness of triaxial tensile strain in enhancing the phonon scattering, reducing the κl, and improving the TE properties of Tl3TaSe4.