NDLI: Thermoelectric properties of /spl beta/-FeSi/sub 2/-TiB/sub 2/ composites

Content Provider	IEEE Xplore Digital Library
Author	Cai, K.F. Muller, E. Drasar, C.
Copyright Year	2002
Description	Author affiliation: Inst. of Mater. Res., German Aerosp. Center, Cologne, Germany (Cai, K.F.; Muller, E.; Drasar, C.)
Abstract	Composite media are under consideration with respect to their capability to possibly increase the thermoelectric power factor or even the figure of merit compared with homogeneous phases they are composed of. Series of /spl beta/-FeSi/sub 2/-TiB/sub 2/, composites with composition near the percolation threshold were prepared on different routes. Co-doped /spl beta/-FeSi/sub 2/ powders (5 at% Co) with various amount of TiB/sub 2/ powder added were ball milled. On the other hand, powders of both materials were simply mixed. Both of these precursors were hot pressed after drying and the compacts were annealed. SEM observations show that for the milled powders the FeSi/sub 2/ particles are smaller than those of TiB/sub 2/, while after simply mixing this is vice versa, according to the initial powder grade. The percolation threshold was found at a volume fraction of TiB/sub 2/ of 0.255 (milled) and 0.145 (mixed), respectively. The electrical and thermal conductivity, and the Seebeck coefficient were measured in dependence on temperature. The results show different transport behavior for these two series of composites. The figure of merit Z for both routes is always lower than that of FeSi/sub 2/ without addition of TiB/sub 2/. Whereas the milling route shows better Z values for given TiB/sub 2/ content and a much higher critical volume fraction (percolation threshold) than simple mixing, the latter reaches the percolation threshold at much lower addition of the highly-conducting phase TiB/sub 2/ and at much higher Z. As a peculiarity when milling hard materials like silicides and borides, the modification of the composites by introduction of iron from the milling set has to be considered.
Starting Page	85
Ending Page	89
File Size	516973
Page Count	5
File Format	PDF
ISBN	0780376838
DOI	10.1109/ICT.2002.1190271
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2002-08-29
Publisher Place	USA
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Thermoelectricity Powders Thermal conductivity Reactive power Ball milling Annealing Conductivity measurement Electric variables measurement Temperature dependence Composite materials
Content Type	Text
Resource Type	Article

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