The effects of Sn-substitution on thermoelectric properties of In4−xSnxSe3 ceramic

In this work, In4−xSnxSe3 (x=0, 0.02, 0.04, 0.06, 0.08 and 0.1) ceramic samples were synthesized by high energy ball milling and subsequent hot pressing. The formation energies of In15SnSe12 were estimated at each possible Indium (In) site, in order to find the most favorable site for Sn substitution. With increasing the Sn content, a significant increase was observed in the carrier concentration, higher than that of the pure one, which was due to the Sn donor activity for In4Se3. According to the obtained results, in addition to the carrier concentration, the carrier effective mass was also a very effective agent for controlling thermopower. Besides, the nanostructuring injected a large density of interfaces in which the phonons over a large mean free path range could be scattered more effectively than electrons and hence reducing the lattice thermal conductivity. Increasing the Sn content also led to a further reduction in the grain size, and therefore more phonon scattering as a strategy to decrease the thermal conductivity and increase the efficiency, ZT. For the sample of x=0.08, the ZT value of 0.78 is achieved at 700 K, 60% higher than that of the un-substituted sample.