Alexandria Digital Research Library

Alternative Approaches to Group IV Thermoelectric Materials

Author:
Snedaker, Matthew Loren
Degree Grantor:
University of California, Santa Barbara. Chemistry and Biochemistry
Degree Supervisor:
Galen D. Stucky
Place of Publication:
[Santa Barbara, Calif.]
Publisher:
University of California, Santa Barbara
Creation Date:
2015
Issued Date:
2015
Topics:
Engineering, Materials Science and Chemistry, Physical
Keywords:
Thermoelectrics
Electronic
Semiconductors
Thermal
Genres:
Online resources and Dissertations, Academic
Dissertation:
Ph.D.--University of California, Santa Barbara, 2015
Description:

In the pursuit of energy efficiency, there is a demand for systems capable of recovering waste heat. A temperature gradient across a thermoelectric material results in the thermal diffusion of charge carriers from the hot side to the cold side, giving rise to a voltage that can be used to convert waste heat to electricity. Silicon germanium (SiGe) alloys are the standard materials used for thermoelectric generators at high temperatures.

We report an alternative method for preparing p-type Si1- xGex alloys from a boron-doped silica-germania nanocomposite. This is the first demonstration of the thermoelectric properties of SiGe-based thermoelectrics prepared at temperatures below the alloy's melting point through a magnesiothermic reduction of the (SiO 2)1-x(GeO2) x. We observe a thermoelectric power factor that is competitive with the literature record for the conventionally prepared SiGe. The large grain size in our hot pressed SiGe limits the thermoelectric figure of merit to 0.5 at 800° for an optimally doped p-type Si80Ge 20 alloy.

A phosphorus-doped oxide can yield n-type Si1- xGex; however, the current processing method introduces a background boron content that compensates ~10% of the donor impurities and limits the thermoelectric power factor.

Spark plasma sintering of the nano-Si1-xGe x yields a heterogeneous alloy with thermal conductivity lower than that of the hot pressed homogeneous alloy due to a reduction in the average crystallite size. Magnesiothermic reduction in the presence of molten salts allows some control over crystallite growth and the extent of Si-Ge alloying.

Physical Description:
1 online resource (193 pages)
Format:
Text
Collection(s):
UCSB electronic theses and dissertations
ARK:
ark:/48907/f3mg7mp8
ISBN:
9781321696936
Catalog System Number:
990045119660203776
Rights:
Inc.icon only.dark In Copyright
Copyright Holder:
Matthew Snedaker
File Description
Access: Public access
Snedaker_ucsb_0035D_12498.pdf pdf (Portable Document Format)