Shakouri / Kauzlarich Intellectual Merit: Novel thermoelectric materials will be developed based on abundant and non-toxic Zintl phase magnesium silicide alloys. A synthesis method is proposed that naturally provides embedded nanoparticles within a magnesium silicide alloy matrix, providing uniform mixing with minimal aggregation. With the use of embedded nanoparticles of appropriate concentration and diameter, thermal conductivity will be reduced by scattering of mid-long-wavelength phonons. Controlling the heterostructure band offset and the potential barrier of nanoparticles with respect to the matrix, the power factor will be increased by selective scattering of hot carriers. Preliminary transport calculations show that ZT>1.8 at 800K could be achieved. Extensive characterization of the material thermoelectric properties will be performed and the results will be benched marked with collaborators at NASA JPL and BSST.
Broader Impact: This proposal seeks to provide fundamental knowledge which can have a major impact on waste heat recovery. Benefiting from the careful optimization of the electron and phonon transport achieved in eptiaxially grown nanoparticle in alloy material and focusing on scalable bulk material synthesis and spark plasma sintering, the plan is to develop a low cost, high performance thermoelectric material.
The close collaboration between co-PIs with background in chemistry and engineering will provide a great learning opportunity for graduate students working on the project. Students will present their research at national and international meetings and will develop an appreciation for the complexity of materials development. The PIs have a history of participation in underrepresented minority outreach programs, supervising minority students and trainees, and participating in a broad array of activities.
We have developed novel composite materials based on abundant and non-toxic alloys that can convert waste heat into electricity. Atomic scale inclusions are used to reduce heat conduction in the material. This is similar to the clouds in the sky that scatter sunlight and reduce the amount of solar radiation coming to the Earth. However the material should have reasonably regular atomic arrangement so that electricity can flow through it. We are able to show proof-of-concept for one composite system and developed several others that can be further optimized. We were also able to show via modeling that high efficiency could be reached if the optimal composition and the doping of the composite could be achieved. This project involved a team of chemists and electrical engineers working together with scientists from the Jet Propulsion Laboratory. The project involved different aspects of the material synthesis, characterization and modeling of heat and current transport. Several undergraduate students were also involved in the research projects, including one who is a co-author on a publication. Training included oral and written presentations at national and international meetings. During the three year cycle of funding, one system was explored in detailed and several others showed great promise.
