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Materials
and Microstructures for Thermoelectric
Devices (Seed Project)
Development of efficient thermoelectric
devices requires the discovery of
materials with a high thermoelectric
figure of merit, ZT,
defined as S2T/ ,
where S
is the Seebeck coefficient, 
the electrical conductivity and the
thermal conductivity. The theoretical
and empirical relationships between
these three parameters has limited
ZT
<1. Materials investigated and
optimized over the past 50 years have
been conventional simple semiconductors
(e.g., bismuth telluride alloys, lead
telluride alloys and silicon germanium
alloys). In the present work we examine
entirely new materials-complex Zintl
semiconductors. We focus primarily
on ternary antimonides of zinc and
cobalt because (1) they will likely
be narrow band gap semiconductors;
and (2) complex crystal structures
are anticipated, which minimize phonon
contributions to thermal conductivity
and, more significantly, yield several
degrees of chemical freedom for the
optimization of ZT.
We build on two binary compounds,
Zn4Sb3
and CoSb3 (extensively
studied at JPL), that have high values
of ZT
(> 1). To date, few ternary antimonides
have been examined as possible thermoelectrics
and thus the potential for major breakthroughs
is high. In addition, nanostructured
composites will be synthesized via
rapid solidification of eutectic compositions
to search for potential quantum confinement
effects, increasing S,
and/or enhanced phonon scattering,
decreasing .
It is anticipated that this work will
yield several new compounds and nanostructured
composites, some of which could have
ZT
values as high as 3 or greater. This,
in turn, would have a tremendous impact
on the refrigeration and power generation
industries as well as on future NASA/JPL
missions, for which reliable, unattended
power sources are critical. Success
in this endeavor will seed future
examinations of even more complex
compounds, and build a Caltech-JPL
collaboration that will rapidly translate
new materials into new devices.
Faculty
Sossina
M. Haile (Principal Investigator)
G.
Jeffrey Snyder (Co-Investigator)
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