Development of Instrumentation, Measurement Protocols, and Standard Reference Materials for Thermoelectric Applications

Abstract

Applications using thermoelectric materials, materials that interconvert thermal and electrical energy, include waste heat recovery in engines for automotive, aerospace, and military applications, and solid-state refrigeration for consumer products and microelectronics. The Seebeck coefficient is an essential indicator of the conversion efficiency and the most widely measured property specific to these materials. However, the intra- and inter-laboratory comparison of Seebeck coefficient measurements has highlighted conflicting data, due to the diversity of instrumentation and the lack of standardized measurement protocols and certified reference materials. Certified Reference Materials (CRMs) and Standard Reference Materials (SRMs®) provide unchanging and accessible starting points that can support the development, production and reliability of materials and devices. We have recently introduced the National Institute of Standards and Technology (NIST) SRM® 3451 “Low Temperature Seebeck Coefficient Standard” to enable instrument validation, interlaboratory comparisons, and protocol studies between 10 K and 390 K. A complementary standard for high temperature (300 K to 900 K) is now in the final stages of production. This talk will describe the synthesis and preparation of boron-doped polycrystalline silicon germanium for use as a high temperature Seebeck coefficient SRM®, including preview certified reference material data and uncertainty analysis. I will also describe the development of our custom high temperature thermoelectric measurement apparatus, which is uniquely capable of in situ comparison of commonly applied probe arrangements and measurement techniques. This has allowed us to identify standard testing protocols for the measurement of the Seebeck coefficient. In this talk, I will demonstrate that thermal contact errors for different probe arrangements are the primary influence on measurement accuracy at high temperature.

About the Speaker

Joshua Martin is a Florida native and was graduated from the University of South Florida with a Ph.D. in Applied Physics in 2008. His research focused on the synthesis, physics, and metrology of clathrate, skutterudite, and novel nanocomposite materials for thermoelectric applications. Joshua has been a research physicist at the National Institute of Standards and Technology (NIST) for over 10 years, beginning with a National Research Council (NRC) Research Fellowship. He is currently leading the project “Measurements, Standards, and Data for Energy Conversion Materials.” In his career, he has designed and constructed a number of novel instruments to increase the accuracy of transport property measurements and to identify optimal metrology protocols. He has also worked on several projects to develop Standard Reference Materials (SRMs), enabling researchers to calibrate measurement instrumentation and to reliably compare data. In his free time, Joshua composes piano music, writes poetry, and designs 2D visual art, sculpture, and jewelry that promote science and engineering education to a broader audience through the perspective of art.