Oxide-Graphene Thermoelectrics Composites: Power Generation from Waste Heat

Traditional thermoelectric (TE) materials, such as Bi2Te3, operate at low-to-modest temperatures and have very narrow operating windows. In addition, they degrade at high temperatures and rely on rare, expensive, and toxic elements. By contrast, oxide TE materials are based on earth-friendly elements and stable to high temperatures. A current limitation of most oxide TE materials is the modest performance, described in terms of the thermoelectric figure of merit (ZT). We have demonstrated for La–doped SrTiO3 thermoelectrics that by incorporating less than 1% graphene the electrical conductivity of the composite is enhanced by several orders of magnitude, and the thermal conductivity reduced, to significantly increase TE performance over an exceptionally wide operating window of at least 600 °C (Lin et al. ACS Applied Materials Interfaces 7, 15898, 2015). However, the mechanisms by which graphene enhances thermoelectric performance in oxides are not understood except at a very superficial level. Recent work suggests that the performance of oxide-graphene composites could be increased considerably if grain-boundary processes can be controlled.

The underlying objective is to understand the critical aspects of graphene-oxide composites that give rise to enhanced thermoelectric performance. The work will involve preparing a range of oxide-graphene thermoelectric composites and determining the thermal and electrical characteristics and how they depend on processing conditions. Detailed electron microscopy of the samples will be required to understand the impact of microstructural features on thermoelectric performance. There will be opportunities to work on high resolution electron microscopes and use other state-of-the-art instruments.