Influence of biaxial and isotropic strain on the thermoelectric performance of PbSnTeSe high-entropy alloy: A density-functional theory study

Strain engineering is an effective method to improve materials thermoelectric (TE) performance. In this study, both biaxial and isotropic strains ranging from −3% to +3 % and from −3% to −1%, respectively, were applied to improve the TE properties of PbSnTeSe high entropy alloy (HEA). The effects of strain on the TE transport properties of PbSnTeSe HEA were investigated using first-principles calculations combined with Boltzmann transport theory. Under biaxial strain, n-type doped PbSnTeSe HEA shows an increase in the optimal power factor ($PF$) with both compressive and tensile strains. For p-type doping, compressive strain enhances the $PF$, whereas tensile strain reduces it. Within a strain range of −3% to +3 %, the optimal $PF$ are 7.8–9.5 mW/mK² for n-type and 0.85–1.3 mW/mK² for p-type doped PbSnTeSe HEA. The maximum figure of merit ($ZT$) value of 1.63 for n-type doped PbSnTeSe HEA at 300 K under 3 % tensile strain is 61 % higher than the $ZT$ value of 1.1 without strain. Under isotropic strain ranging from 0 % to −3%, the $PF$ increases from 7.8 to 14 mW/mK² for n-type and from 1.1 to 3.4 mW/mK² for p-type doped PbSnTeSe HEA. Additionally, isotropic strain boosts the maximum $ZT$ value for p-type doped PbSnTeSe HEA at 300 K from 0.3 to 0.85 under −3% strain. This study confirms that strain engineering is an effective strategy to enhance the thermoelectric properties of PbSnTeSe HEA.