Equivalent doping of Te leads to optimized electrical and thermal transport properties in thermoelectric Cu₂MnSnSe₄ alloys

Quaternary chalcogenides have garnered considerable interest within the field of thermoelectric due to their intrinsic low thermal conductivity, wide band gap and high element enrichment advantages. In this work, the thermoelectric performance of Cu₂MnSnSe₄ was enhanced by co-optimizing the carrier concentration and lattice thermal conductivity through self-doping with Cu and doping with Te. A series of Cu₂MnSnSe₄ and Cu_2.1Mn_0.9SnSe_4-xTe_x (x = 0, 0.01, 0.05, 0.10) samples were prepared by ball-milling and hot-pressing methods. The carrier concentration of the samples was significantly increased after Cu self-doping, leading to optimized electrical transport performance. The notable reduction in lattice thermal conductivity was attributed to the scattering effect caused by Te substitutional -induced point defects. At 673K, the lattice thermal conductivity of Cu_2.1Mn_0.9SnSe_3.9Te_0.1 sample obtained the lowest value of 0.62 W m^-1K^-1. Finally, it achieved a maximum zT ~ 0.5 at 673 K in Cu_2.1Mn_0.9SnSe_3.9Te_0.1 sample, roughly twice that of the Cu₂MnSnSe₄ sample.