Condensed-Matter Physics & Materials Science Seminar

"High-Throughput Combinatorial Thermoelectrics Research Using Sputtering"

Presented by Evan Thomas, National Institute of Standards and Technology

Thursday, June 28, 2007, 2:45 pm — Bldg. 480 - conference room

For decades, there has been a vast search for improved thermoelectric (TE) materials, which have the potential for wide-spread use in environmentally friendly devices capable of the efficient conversion of thermal energy to electrical energy. Researchers in this field are greatly interested in increasing the dimensionless figure of merit, ZT, which is a measure for the efficiency of a TE material and is defined as ZT = (2/, where  is the Seebeck coefficient,  is the electrical conductivity,  is the thermal conductivity, and T is the absolute temperature. High-throughput combinatorial mapping is a state-of-the-art screening technique for accelerating the selection and introduction of TE materials into the manufacturing process. The combinatorial method can eliminate some of the effort associated with the trial-and-error syntheses of inorganic solid-state materials such as intermetallics and ceramics, and can quickly and cost-effectively produce libraries of binaries, ternaries, quaternaries, etc. Using the sputtering technique, precursors are deposited successively through physical masks to vary the elemental compositions, after which, the power factor (2) of the fabricated films may be measured using a screening system developed at NIST. Some promising candidates for use in this high-throughput screening method, particularly intermetallic compounds such as R14MnX11 and R3Co4 Sn13 with open cage-like structures, will be presented. These structurally similar compounds have shown enhanced TE behavior due to the relationship between the rattling motion of guest atoms and the phonon thermal conductivity, i.e., they have “phonon-glass/electron-crystal” (PGEC) qualities, or behave electronically like a crystalline material and have the thermal properties of an amorphous material.

Hosted by: Qiang Lli

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