Nonmagnetic in substituted CuFe_{1 x}In_xS₂ solid solution thermoelectric

CuFeS₂ is an environmentally friendly n-type thermoelectric material composed of earth-abundant, inexpensive and nontoxic elements. However, its rather undistinguished electronic properties combined with a high thermal conductivity lead to a low thermoelectric performance. In this work, an attempt is made to reduce the lattice thermal conductivity of CuFeS₂ by In substituting on the Fe site. A series of CuFe_1-xIn_xS₂ (x = 0-0.08) compounds was synthesized by vacuum melting combined with the plasma activated sintering (PAS) process, and the effect of substituting In atoms on the band structure and thermoelectric properties of CuFeS₂ has been investigated. The results show that the solubility limit of In in CuFeS₂ is more than 8%. For the In content of 0.08, the lattice thermal conductivity of room temperature and at 630 K was reduced by 60% and 37%, respectively, indicating that substituting In for Fe is an effective method to reduce the lattice thermal conductivity of CuFeS₂. A single parabolic band model was used to calculate the effective mass of all samples, and the data indicate that small amounts of In do not change the band structure of CuFeS₂. Finally, the thermoelectric performance has been enhanced due to the large decrease in lattice thermal conductivity.