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MATERIALS
SCIENCE
AND
ENGINEERING
SEMINAR
“Using
the Traveling
Heater Method to Process
a Type I
and VIII
Clathrate Intermetallic Compound for Higher Efficiency
Thermoelectric Materials”
By
Kyungjean Min
Purdue MSE Preliminary
Exam
Advisors:
Professor David R. Johnson and Kevin
P. Trumble
ABSTRACT
For semiconducting
applications,
intermetallic clathrates have been developed during
last
the few decades.
Intermetallic clathrates are
divided into several
different types based on
their crystalline structure
and
chemical
composition. Among intermetallic
clathrates, the type
I and
VIII clathrate
intermetallic compound,
Ba8Ga16Sn30,
has
been in the limelight
as an effective
thermoelectric material
with
higher
figure of
merit that is
proportional to the ratio of electric
conductivity
and
thermal conductivity.
Type
VIII
Ba8Ga16Sn30
is the dimorphic structure
of Type
I Ba8Ga16Sn30
and
both can be obtained in
different
growth conditions.
Moreover, the large
size single crystal of Ba8Ga16Sn30
is
preferred to
characterize thermoelectric properties.
To grow
type VIII clathrate intermetallics
the flux
growth
and Bridgman
methods have
been utilized until now.
However,
there are disadvantages in
that
flux growth
method is
able to grow small
single crystal in size
or polycrystal
and Bridgman
method
has a
difficulty
to grow
incongruent melting
compound.
The crystal grown
by
both methods has a
necessarily deviated
stoichiometric ratio
because of stoichiometric
range in
congruent melting
line. Traveling
heater
method is
being proposed to
grow a large
single crystal of
type VIII clathrate intermetallics.
For the single crystal
growth,
magnetic stirring in the zone will be employed.
This
method will
be effective in
obtaining
higher
figure of merit
by
lowering thermal conductivity
and increasing
electric
conductivity.
By
investigating
produced
Ba8Ga16Sn30
using
differential
thermal analysis,
XRD and
microstructure characterization,
phase diagram for Ba8Ga16Sn30
will
be determined.
Date:
Monday,
October 19, 2015
Time:
10:30
A.M.
Place:
ARMS 1028
PURDUE
MSE
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