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 bandgap 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 Cu2.1Mn0.9SnSe4-x Tex (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 substitution-induced point defects. At 673 K, the lattice thermal conductivity of the Cu2.1Mn0.9SnSe3.9Te0.1 sample obtained the lowest value of 0.62 W m-1K-1. Finally, it achieved a maximum zT ~ 0.5 at 673 K in the Cu2.1Mn0.9SnSe3.9Te0.1 sample, roughly twice that of the Cu2MnSnSe4 sample.