Substantial role of doping in the thermoelectric and hardness properties of nanostructured bornite, Cu5FeS4

To improve current solid state thermoelectric devices, high performance materials based on safe and abundant elements is required. Here, Cu5-xZnxFeS4 (0 <= x <= 0.1) and Cu4.96Co0.04Fe1-xZnxS4 (0 <= x <= 0.06) nanostructured solid solutions, based on very abundant elements, were synthesized by high energy ball milling and hot pressing. X-ray diffraction (XRD) data showed the crystal structure of the materials to be consistent with a pure bornite phase in the entire substitution level for Cu5-xZnxFeS4 and Cu4.96Co0.04Fe1-xZnxS4 solid solutions. A Vickers microhardness of 167 Hv was obtained for pristine bornite which increased to around 250 Hv upon doping. Zn-substitution led to a slight increase in the power factor form 0.25 mWm(-1)K(-2) for pristine bornite to 0.27 mWm(-1)K(-2) for Cu4.9Zn0.1FeS4 at 590 K. Substituting Co for Cu and Zn for Fe, on the other hand, led to a significantly high power factor of 0.37 mWm(-1)K(-2) for Cu4.96Co0.04Fe0.96Zn0.04S4 at 590 K. Extremely low thermal conductivities of k < 0.75 Wm(-1)K(-1) were obtained for all samples. A high ZT of 0.6 at 590 K was attained for Cu4.96Co0.04Fe0.96Zn0.04S4 solid solution which is among the highest reported values for bornite at 590 K. (C) 2018 Elsevier B.V. All rights reserved.