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

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 2.1 Mn 0.9 SnSe 4 is further regulated by substituting Mn 2+ with equimolar pairing elements (Ag + and In 3+ ). 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.