Utilizing Magnetism and Nanostructures to Enhance Performance of Thermoelectric Materials

New principles and strategies are desired to overcome the traditional tradeoff between thermoelectric (TE) properties, i.e. electrical conductivity σ and thermal conductivity κ, and Seebeck coefficient α. We have been trying to develop TE enhancement principles which can be relatively easily implemented and applied to a wide range of materials [1]. Porosity had been considered detrimental for TE materials, with the penalty for σ usually being similar or larger than the κ reduction. Introducing a moderate volume of nano-micropores with size distribution by simple evaporation of a secondary phase, has led to effective phonon selective scattering, and 100% enhancement to figure of merit σα²/κ =ZT~1.6 in rare earth-free (“empty”) skutterudites [2]. This strategy has also led to ZT enhancement in other materials which will be presented. We have proposed to utilize magnetic interactions between carriers and magnetic moments to enhance the power factor σα² [3]. Unlike magnon drag, TE enhancement via magnetic interaction is not solely dependent on ordering, and is effective at higher temperatures also. Magnetic ion doping for example, has led to TE enhancement for a variety of cases, CuGaTe₂, BiCuSeO, Bi₂Te₃, SnTe, etc., if effective coupling is created. We have also demonstrated significant enhancement of the Seebeck coefficient via spin fluctuation. CREST project members are acknowledged.
[1] Small 13 (2017) 1702013, [2] Nano Energy 31 (2017) 152, [3] Angew. Chem. 54 (2015) 12909, J. Mater. Chem. A 5 (2017) 7545, J. Mater. Chem. C 6 (2018) 6489, Mater. Today Phys. 3 (2017) 85.