Experimental Team

The experimental effort at Reading is principally directed at the laboratory synthesis and evaluation of thermoelectric properties of materials derived from the key target minerals. Using a combination of high-energy ball milling and high-temperature synthesis in sealed glass tubes, we are exploring the impact of chemical substitution on the thermoelectric properties of synthetic analogues of copper sulphide minerals, particularly chalcopyrite and bornite. Initial structural characterization is carried out in house, using powder X-ray diffraction, coupled with Rietveld refinement. Additional materials characterization is provided by instruments within the University of Reading Chemical Analysis Facility. These measurements are complemented by more specialized spectroscopic and structural investigations at large-scale central facilities. Materials for property measurements are consolidated by hot-pressing, enabling electrical transport properties to be investigated over the relevant temperature range of 300 ≤ T/K ≤ 750, using a Linseis LSR3-800 instrument. Complementary Hall coefficient measurements are performed with an Ecopia HMS-3000 system, which allows changes in charge-carrier concentration on substitution to be established. Thermal diffusivity is measured using a Netzsch LFA 447 Nanoflash and an Anter Flashline 3000 instrument.

The primary contributions of the Manchester team are in ceramic and composite fabrication, detailed electron microscopy and thermoelectric property measurement. The work includes preparation of chalcopyrite and chalcocite by Mechanical Alloying followed by Spark Plasma Sintering. Here the role of stoichiometry and additives on thermoelectric properties will be investigated. High performance graphene nano-composites will be fabricated. The microstructure and crystal structure of these materials plus pristine and doped chalcopyrite compositions prepared by the University of Reading will be investigated by electron microscopy techniques. The full range of thermoelectric properties will be determined for ceramics and composites.

We are currently synthesizing chalcopyrite mineral, CuFeS2 using solution-based approaches, mainly by the solvothermal or hydrothermal method as an alternative to high-temperature solid-state synthetic methods. Our primary focus is to synthesize nanoparticles of CuFeS2 with a greater degree of control on the microstructure of the synthesized material and, therefore, to minimize the thermal conductivity. Interestingly after our initial finding, we have obtained ntype conduction behavior in CuFeS2. Subsequently, we have started different doping in this material to optimize electrical and thermal transport and enhance thermoelectric performance.