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Place Holder Thermoelectrics at Northwestern!

The Snyder Group at Northwestern MSE continues to specialize in Thermoelectric Materials and Devices as well as expand into other Materials for Energy fields. Interested students are encouraged to apply to the top ranked MSE department at Northwestern University wtih many groups studying thermoelectrics. Close collaboration with NASA-Jet Propulsion Laboratory will contiune.

Place Holder Stephen Kang wins 2017 ITS Student Award

For his work on understanding the electronic transport using the generalized transport function, combining seebeck and conductivity experiments. Now a postdoc at Stanford U.

Place Holder Yinglu Tang wins 2016 ITS Goldsmid Award

For her work on understanding the electronic structure and phase relations for optimizing Skutterdite thermoelectric materials. Yinglu is now at ABB formerly postdoc at EMPA in Switzerland.

Place Holder Sabah Bux (JPL) wins 2015 ITS Young Investigator Award

For her work on novel and nanostructured thermoelectric materials.

Place Holder Heng Wang wins 2014 ITS Goldsmid Award

For his Ph.D. work on Band Engineering and PbSe. Now an assistant professor at Illinois Institute of Technology

 

Place Holder Alex Zevalkink wins 2013 ITS Goldsmid Award

For her Ph.D. work on new Zintl phase thermoelectric materials. Alex is now an assistant professor at Michigan State University.

 

Place Holder Yanzhong Pei wins 2013 ITS Young Investigator Award

For his work on band engineering of thermoelectric materials. Former Posdoc Yanzhong Pei (裴艳中) is Professor of Materials Science at Tonji University in Shanghai China.

 

Place Holder Curiosity Rover Powered by Thermoelectrics Lands on Mars

The newest Mars rover from NASA JPL uses PbTe-based thermoelectrics for power. News and Video

 



Highlights

Complex Zintl Compounds and Phase Boundary Mapping

Place Holder The rich solid-state chemistry of Zintl phases enables a directed search and optimization of new complex thermoelectric materials. Several new Zintl Compounds have been found with inherently low thermal conductivity and can be doped to have high zT. Phase Boundary Mapping is often needed to explore the full range of properties.

 

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Thermal Conductivity due to Dislocations and Grain Boundaries

Place HolderExceptionally low thermal conductivity good Peltier cooling performance was found in Bi2Te3-Sb2Te3 alloys hot pressed with liquid Te. The reduced thermal conductivity with only a small reduction in electron mobility can be explained by low energy grain boundaries consisting of dislocation arrays.

 

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Charge Transport Model for Complex Conductors: Conducting Polymers, Correlated Electron Oxides and Grain Boundaries

Cu2SeA two parameter mathematical model that can explain the experimentally observed relationship between thermopower (Seebeck coefficient) and electrical conductivity can identify the charge transport mechanism. For example itinerant band conduction in SrTiO3 or hopping, narrow band conduction in CeO2. Thermally activated conductivity in polycrystalline materials may arise from grain boundary polarization effects. The model clearly identifies a different mechanism for conducting polymers, that may be an indication of percolation transport between conducting ordered regions (figure).

 

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Liquid-Like Thermoelectric Materials

Cu2Se Because a liquid does not propagate shear vibrations the thermal conductivity can be less than that of a solid. Using the liquid-like behaviour of superionic conductors and related highly disordered materials extends the phonon-glass electron-crystal concept for the search for new thermoelectrics.

 

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Triboelectric Materials and Devices

Cu2Se When different materials are rubbed together there is a transfer of static electric charge known as Triboelectricity. Because of the charge separation and movement large voltages are produced, enough to cause sparking (static electricity discharge). The power produced from such Triboelectric Generatoris comes not from the rubbing but from the movement of electric charges from electric induction, resulting in direct conversion of mechanical energy to electrical energy.

 

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Band Structure Engineering Thermoelectrics

Place HolderAlloys of PbTe and Bi2Te3 have been used to generate electricity from heat on NASA space missions for 50 years and now are being considered for use on Earth for automotive waste heat recovery. Our group has recently demonstrated that the zT of PbTe and PbSe alloys can be tuned to be much better than previously thought possible due, in part, to the exceptionally high valley degeneracy.

 

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Half Heusler

Many Half Heusler compunds are semiconductors despite their seemingly intermetallic constituants. This can be rationalized using Zintl chemistry, to show that Half Heusler thermoelectris are based on valence balenced semicondutors. These Zintl chemistry principels can be used then to understand p- and n-type doping as well as defects such as the role of Nb-vacancies in Nb0.8+xCoSb. It also explains that interstitial Ni easily forms in (Ti,Zr)Ni1+xSn adding filled electronic states in the band gap.