Date of Award

8-2009

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Physics

Advisor

Tritt, Terry M

Committee Member

He , Jian

Committee Member

Marinescu , Catalina

Committee Member

Skove , Malcolm

Abstract

This study explores the possibility of somewhat decoupling the electrical and thermal conduction, thereby being able to limit the thermal conduction while minimizing the effect on the electrical conduction. The approach is using a nanoparticle layer with a slight compositional mismatch as compared to the bulk skutterudite. A hydrothermal nanoparticle-plating technique has been employed to grow a layer of CoSb3 nanoparticles on the surface of skutterudite bulk matrix grains. Skutterudites of various forms were fabricated and studied in order to assess the effect of this nano-plated layer as a viable method in the improvement of thermoelectric properties of CoSb3 nanocomposites. The skutterudite materials studied include Ni doped, rare earth(La, Ce, or Yb) filled, and Yb and Ce double filled skutterudites. The nanoparticles have a typical size of 30-40 nm while the nano-layer can be up to several hundred nm thick. The nanoparticle layer, which is at the grain boundary after hotpressing, provides an extra scattering channel for phonons, in addition to the 'rattler' atoms, grain boundary scattering and mass fluctuation mechanisms found within the bulk matrix grain.
The electrical resistivity, thermopower, thermal conductivity, and Hall coefficient have been investigated as a function of temperature and the weight percentage (%) of nanoparticles and will be reported with respect to their potential as thermoelectric materials. Improvement in the ZT can be seen in the filled skutterudite series, though the mechanisms providing this improvement are not identical. This nano-plating process shows itself to be a viable method that can be used in conjunction with other techniques, such as doping and void filling, to improve the thermoelectric properties of skutterudites.

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