First-principles prediction of structural stability and thermoelectric properties of SrGaSnH

Abstract

Thermoelectric (TE) materials based on earth-abundant and non-toxic elements are very useful in cost-effective and eco-friendly waste heat management systems. The constituents of SrGaSnH are earth-abundant and non-toxic, thus we have chosen SrGaSnH to study its structural stability and thermoelectric properties by using density functional theory (DFT), density functional perturbation theory (DFPT), and semi-classical Boltzmann transport theory. Our elastic and phonons calculations show that the compound has good structural stability. The electronic structure calculation discloses that it is an indirect bandgap (0.63 eV by mBJ potential including spin–orbit coupling (SOC) effect) semiconductor. Light band hole effective mass leads to higher electrical conductivity along the x-axis than that of along the z-axis. On the other side, the weak phonon scattering leads to high lattice thermal conductivity ∼ 6.7 W m⁻¹ K⁻¹ at 300 K. Although the power factor (PF) is very high along the x-axis (above 10 mW m⁻¹ K⁻² at 300 K), such large κ_l dramatically reduces ZT. The maximum values of in-plane and cross-plane ZT are ∼1 (n-type), 0.8 (p-type) and 0.6 (n-type), (0.2 p-type) at 700 K, respectively. The present study has revealed that this compound has strong potential in eco-friendly TE applications.