Suppressed lattice thermal conductivity due to K+ ion vibration results in high thermoelectric performance in K4ZnAs2

Abstract

By using density functional theory and the Boltzmann transport equation, we herein explored the electronic structure and thermoelectric transport behavior of K₄ZnAs₂. K₄ZnAs₂ exhibits significantly low lattice thermal conductivities (κ_l) of 0.282 and 0.138 W m⁻¹ K⁻¹ along the x(y)- and z-directions, respectively, at 300 K. The rattling behavior of K atoms causes substantial anharmonicity in K₄ZnAs₂, and this leads to high phonon scattering rates. The low group velocity and high scattering rates of the heat-carrying phonons suppress the lattice thermal conductivity. Our study suggests that for both p-type and n-type K₄ZnAs₂, the suppression of lattice thermal conductivity, along with a high to moderate Seebeck coefficient and electrical conductivity, makes it a viable material for thermoelectric applications.