materials science and engineering, northwestern university
g. jeffrey snyder obtained his b.s. degree in physics, chemistry and mathematics at cornell university (1991) focusing on solid state chemistry which he continued during a two year stay at the max planck institut fkf (festkörperforschung) in stuttgart, germany. he received his ph.d. in applied physics from stanford university (1997) where he studied magnetic and magneto-electrical transport properties of metallic perovskites as a hertz fellow. he was a senior member of the technical staff in the thermoelectrics group at nasa’s jet propulsion laboratory for 9 years (1997-2006) and as a faculty associate in materials science at the california institute of technology (caltech) 2006-2014 where he focused on thermoelectric materials and devices. his interests include the discovery of new zintl phase thermoelectric materials and nanostructured thermoelectric composites using bulk processing, band structure engineering and thermoelectric performance optimization. dr. snyder has published over 400 articles, book chapters and patents. he served as treasurer of the international thermoelectric society and vice president of the international thermoelectric academy.
Dr. Snyder is one of the world’s most prominent and highly cited (Clarivate Analytics highly cited researcher each year since 2016 to 2019) scientists particularly in the rapidly growing field of thermoelectrics. His 2008 review article in Nature Materials, is used internationally to instruct many new students, and introduce the essentials of thermoelectricity to a multi-disciplinary audience and is the most cited article in thermoelectrics.
Bi2Te3 alloys are the most widely used thermoelectric, because they have had the highest efficiency in the 250-500K temperature range relevant for cooling and low-grade waste-heat recovery. The new Mg3Sb2 based Zintl thermoelectric materials have achieved remarkable zT > 1 performance at high temperatures that has lead to many new discoveries in several laboratories worldwide. Recently, through the use of alloying, band structure engineering and grain boundary engineering we have shown that n-type Mg3Sb0.6Bi1.4, with a thermoelectric figure-of-merit zT of 1.0-1.2 at 400-500K, finally surpasses n-type Bi2Te3.
In this talk I will review the lengthy, step-wise achievements in materials processing and physical understanding that lead to this breakthrough. From the realization that chemical phase equilibria is a dominant factor determining dopability we explain the unexpected discovery of n-type Mg3Sb2 based Zintl thermoelectric materials and show that the principles of Phase Boundary Mapping幸运赛车官网 can be applied to most other thermoelectric systems to optimize and control doping, explaining and predicting how processing affects thermoelectric properties. Despite the simple crystal structure, the peculiar bonding of Mg leads to the high valley degeneracy in the conduction band as well as soft phonon modes that both lead to its exceptional thermoelectric performance. With this careful understanding of the electronic structure, the band structure can be engineered to maximize performance in the low temperature region.
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