Tuning the bonding environment of Se atom in Cu2MnSnSe4-based alloys for raised thermoelectric performance

Abstract

The intrinsic low lattice thermal conductivities originates from the complex anion bonding environment make quaternary chalcogenides potential thermoelectric materials. Here, the bonding environment of Se atom in Cu_2.1Mn_0.9SnSe₄ is further regulated by substituting Mn²⁺ with equimolar pairing elements (Ag⁺ and In³⁺). The increase in both bond length and angle, together with the reduction in bond strength of Ag–Se and In–Se bonds, cause the doped samples to display strong anharmonicities (γ ∼ 1.84–2.04). And the weakened bond strength also lower the sound velocities. Consequently, the κ_L of the doped samples is effectively constrained, achieving a minimum value of 0.55 W⸱m^–1⸱K^–1 at 673 K in x = 0.10 sample. Ultimately, a zT value of 0.53 at 673 K is attained in x = 0.10 sample. The modification of bonding environment around anion is considered as an effective mean to optimize the thermoelectric performance of quaternary chalcogenides.