Integration of Multi-scale Defects for Optimizing Thermoelectric Properties of N-Type Cu1-xCdxFeS2 (x=0-0.1)

The performance of thermoelectric (TE) materials is strongly influenced by the multi-scale defects. Some defects can improve the TE performance but some are unfavorable. Therefore, the multi-scale defects need to be integrated rationally to enhance the TE properties. Here, the defects including atomic-scale point defects, high-density grain boundaries as well as nano precipitates were integrated in CuFeS2, an n-type and earth-abundant TE material. Primitively, Cd dopant with high scattering factor was introduced to form Cd_Cu^∙ point defects in the Cu1-xCdxFeS2 (x=0-0.1) according to the calculated scattering parameters. Further, the process of quenching, annealing, high-energy ball milling (QAH) and sintering were carried out to integrate the multi-scale defects in the Cu1-xCdxFeS2. The results suggested that the Cd_Cu^∙ point defects and Fe_Cu^(∙∙) antisite defects were achieved and the unfavorable Cd_Fe^, defects were suppressed effectively, leading to the higher electrical conductivity. Moreover, the CdS nano precipitates played a vital role in filtrating carriers to increase Seebeck coefficient. Meanwhile, the high-density grain boundaries suppressed the lattice thermal conductivity. As a result, a peak ZT value of 0.39 at 723 K was obtained in Cu0.92Cd0.08FeS2, which is the highest value reported so far in the CuFeS2 family.