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Thermoelectrics: Direct Thermal to Electrical Energy Conversion

Thermoelectric effect is the direct conversion of thermal temperature gradient into electrical energy. Since about 40% of the total energy in any thermal or mechanical machines is wasted as heat, thermoelectricity provides an effective way to recover some of these wasted energies and convert those into some usable form. Currently the efficiency of the thermoelectric materials represented by dimentionless figure of merit ZT are extremely small. We must develop materials that has ZT of about 3-4 to be competitive with conventional power generators, and for that we must simultaniously increase the Seebeck coefficient and electrical conductivity of the material while reducing the thermal conductivity.

Our approcah is to use nitride semiconductors and metal/semiconductor superlattices to improve the efficiency of the thermoelectric materials. The Schottky barrier at the metal/semiconductor interface gives us an way to increase the Seebeck coefficient with out reducing the electrical conductivity; while the interface also acts as a barrier for the phonon transport reducing the thermal conductivity. Please find the details of our approach in using the nitride materials and metamaterials to improve the thermoelectric eficiency.

(Image Courtesy: Jeff Snyder et. al. Nature Material)



1. High mobility and high thermoelectric power factor in epitaxial ScN films deposited by reactive magnetron sputtering onto MgO(001) substrate. Polina V. Burmistrova, Jesse Maassen, Tela Favaloro, Bivas Saha, Shuaib Salamat, Yee Rui Koh, Mark S. Lundstrom, Ali Shakouri, and Timothy D. Sands. Journal of Applied Physics 113, 153704 (2013).

2. First-principles analysis of thermoelectric ZrN/ScN metal/semiconductor superlattices. Bivas Saha, Timothy D. Sands and Umesh V. Waghmare. Journal of Applied Physics 109, 073720 (2011).

3. Electronic Structure, Vibrational spectra and Thermal Properties of HfN/ScN Metal/semiconductor superlattices:  A first-principles Study: Bivas Saha, Timothy D. Sands and Umesh V. Waghmare. Journal of Physics: Condensed Matter, 24 415303, (2012).

Collaborators: Polina Burmistrovs (Brookhaven National Lab.), Ali Shakouri (Purdue)