Tin doped Cu3SbSe4: A stable thermoelectric analogue for the mid-temperature applications

Here, we report a thermoelectric material, Sn-doped Cu₃SbSe₄, with a figure-of-merit (ZT) of unity, which is stable up to 623 K. The Cu₃SbSe₄ samples, individually doped with Bi, Pb and Sn, were synthesized using conventional vacuum melting followed by the spark plasma sintering. The first-principle density functional theory (DFT) based calculations suggest that these doped Cu₃SbSe₄ compounds have negative formation energy throughout the temperature range, suggesting their chemical/thermal stability. The current study is to support the synchronization of theoretical and experimental study and pre-screening of the dopant which ensures stability and the TE performance. Among all the dopants studied, we realized a ZT_max ∼1 at 623 K with Sn doping for the optimized composition Cu₃Sb_0.985Sn_0.015Se₄ owing to the favourable optimization of the electrical and thermal transport properties. This is also supported by the DFT calculations, which suggests that Sn-doping leads to a decrease in lattice thermal conductivity.