U.S. patent application number 14/493037 was filed with the patent office on 2015-11-19 for high temperature thermoelectrics.
The applicant listed for this patent is Marlow Industries, Inc.. Invention is credited to James L. Bierschenk, Joshua E. Moczygemba, Jeffrey W. Sharp.
Application Number | 20150333243 14/493037 |
Document ID | / |
Family ID | 47626158 |
Filed Date | 2015-11-19 |
United States Patent
Application |
20150333243 |
Kind Code |
A1 |
Moczygemba; Joshua E. ; et
al. |
November 19, 2015 |
High Temperature Thermoelectrics
Abstract
In accordance with one embodiment of the present disclosure, a
thermoelectric device includes a plurality of thermoelectric
elements that each include a diffusion barrier. The diffusion
barrier includes a refractory metal. The thermoelectric device also
includes a plurality of conductors coupled to the plurality of
thermoelectric elements. The plurality of conductors include
aluminum. In addition, the thermoelectric device includes at least
one plate coupled to the plurality of thermoelectric elements using
a braze. The braze includes aluminum.
Inventors: |
Moczygemba; Joshua E.;
(Wylie, TX) ; Bierschenk; James L.; (Rowlett,
TX) ; Sharp; Jeffrey W.; (Murphy, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Marlow Industries, Inc. |
Dallas |
TX |
US |
|
|
Family ID: |
47626158 |
Appl. No.: |
14/493037 |
Filed: |
September 22, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13197260 |
Aug 3, 2011 |
8841540 |
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14493037 |
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Current U.S.
Class: |
136/203 ;
136/201; 136/212; 438/54 |
Current CPC
Class: |
B23K 1/0008 20130101;
B23K 2101/40 20180801; B23K 1/00 20130101; H01L 35/20 20130101;
H01L 35/08 20130101; B23K 2101/38 20180801; H01L 35/32 20130101;
B23K 11/115 20130101; B23K 11/16 20130101; H01L 35/34 20130101;
B23K 1/0016 20130101; H01L 35/04 20130101; H01L 35/18 20130101;
B23K 26/22 20130101 |
International
Class: |
H01L 35/08 20060101
H01L035/08; H01L 35/20 20060101 H01L035/20; H01L 35/34 20060101
H01L035/34; H01L 35/32 20060101 H01L035/32 |
Goverment Interests
GOVERNMENT RIGHTS
[0001] A portion or all of this disclosure may have been made with
Government support under government contract number TCS-236-36
awarded by the United States Department of Energy, and under
government contract number W909MY09C0061 awarded by the United
States Army of the United States Department of Defense. The
Government may have certain rights in this disclosure.
Claims
1-20. (canceled)
21. A thermoelectric device comprising: a first set of plates
comprising a first plurality of conductors directly bonded to the
first set of plates, the first plurality of conductors consisting
essentially of aluminum, the first set of plates being electrically
insulative; a second set of plates comprising a second plurality of
conductors directly bonded to the second set of plates, the second
plurality of conductors consisting essentially of aluminum, the
first set of plates being electrically insulative; a plurality of
thermoelectric elements situated between the first set of plates
and the second set of plates, the plurality of thermoelectric
elements coupled to the first plurality of conductors and the
second plurality of conductors; and a plurality of brazes
comprising aluminum, the plurality of brazes situated at interfaces
between the plurality of thermoelectric elements and the first
plurality of conductors.
22. The thermoelectric device of claim 21 wherein the plurality of
thermoelectric elements comprises a diffusion barrier.
23. The thermoelectric device of claim 22 wherein the diffusion
barrier comprises a refractory metal.
24. The thermoelectric device of claim 22 wherein the diffusion
barrier comprises titanium.
25. The thermoelectric device of claim 21 wherein the first set of
plates plate and the second set of plates comprise a material
selected from the group consisting of: aluminum oxide and aluminum
nitride.
26. The thermoelectric device of claim 21 wherein the plurality of
brazes comprise aluminum silicon.
27. The thermoelectric device of claim 21 further comprising
solder, the solder situated at interfaces between the plurality of
thermoelectric elements and the second plurality of conductors; and
wherein the second set of plates consists of one plate.
28. A method of forming a thermoelectric device, comprising:
directly bonding a first plurality of conductors on a first set of
plates, the first plurality of conductors consisting essentially of
aluminum, the first set of plates being electrically insulative;
directly bonding a second plurality of conductors on a second set
of plates, the second plurality of conductors consisting
essentially of aluminum, the first set of plates being electrically
insulative; applying a plurality of brazes on the first plurality
of conductors, the plurality of brazes comprising aluminum;
situating a plurality of thermoelectric elements between the first
set of plates and the second set of plates, the plurality of brazes
situated at interfaces between the plurality of thermoelectric
elements and the first plurality of conductors; and coupling the
first plurality of conductors and the second plurality of
conductors to the plurality of thermoelectric elements.
29. The method of claim 28 further comprising applying a diffusion
barrier to the plurality of thermoelectric elements.
30. The method of claim 29 wherein the diffusion barrier comprises
a refractory metal.
31. The method of claim 29 wherein the diffusion barrier comprises
titanium.
32. The method of claim 28 wherein the first set of plates and the
second set of plates comprise a material selected from the group
consisting of: aluminum oxide and aluminum nitride.
33. The method of claim 28 wherein the plurality of brazes comprise
aluminum silicon.
34. The method of claim 28 further comprising adding solder to
interfaces between the plurality of thermoelectric elements and the
second plurality of conductors; and wherein the second set of
plates consists of one plate.
35. A thermoelectric generator comprising: a first set of plates
comprising a first plurality of conductors directly bonded to the
first set of plates, the first plurality of conductors consisting
essentially of aluminum, the first set of plates being electrically
insulative; a second set of plates comprising a second plurality of
conductors directly bonded to the second set of plates, the second
plurality of conductors consisting essentially of aluminum, the
first set of elates being electrically insulative; a plurality of
P-type and N-type thermoelectric elements situated between the
first set of plates and the second set of plates, the plurality of
thermoelectric elements coupled to the first plurality of
conductors and the second plurality of conductors; a plurality of
brazes comprising aluminum, the plurality of brazes situated at
interfaces between the plurality of thermoelectric elements and the
first plurality of conductors; and wherein the thermoelectric
generator is configured to operate while the first set of plates is
at a temperature above 300 degrees Celsius.
36. The thermoelectric generator of claim 35 wherein the plurality
of thermoelectric elements comprises a diffusion barrier.
37. The thermoelectric generator of claim 36 wherein the diffusion
barrier comprises a refractory metal.
38. The thermoelectric generator of claim 36 wherein the diffusion
barrier comprises titanium.
39. The thermoelectric generator of claim 35 wherein the first set
of plates and the second set of plates comprise a material selected
from the group consisting of: aluminum oxide and aluminum
nitride.
40. The thermoelectric generator of claim 35 wherein the plurality
of brazes comprises aluminum silicon.
41. The thermoelectric generator of claim 35, wherein the
thermoelectric generator is configured to operate while the first
set of plates is at a temperature above 500 degrees Celsius and
wherein the second set of plates consists of one plate.
Description
TECHNICAL FIELD
[0002] This disclosure relates in general to thermoelectric
devices, and more particularly to high temperature
thermoelectrics.
BACKGROUND OF THE DISCLOSURE
[0003] The basic theory and operation of thermoelectric devices has
been developed for many years. Presently available thermoelectric
devices used for cooling typically include an array of
thermocouples which operate in accordance with the Peltier effect.
Thermoelectric devices may also be used for heating, power
generation and temperature sensing.
[0004] Thermoelectric devices may be described as essentially small
heat pumps which follow the laws of thermodynamics in the same
manner as mechanical heat pumps, refrigerators, or any other
apparatus used to transfer heat energy. A principal difference is
that thermoelectric devices function with solid state electrical
components (thermoelectric elements or thermocouples) as compared
to more traditional mechanical/fluid heating and cooling
components.
[0005] Thermoelectric materials such as alloys of Bi.sub.2Te.sub.3,
PbTe and BiSb were developed thirty to forty years ago. More
recently, semiconductor alloys such as SiGe have been used in the
fabrication of thermoelectric devices. Typically, a thermoelectric
device incorporates both a P-type semiconductor and an N-type
semiconductor alloy as the thermoelectric materials.
[0006] As cooling applications progressively require thermoelectric
devices to operate at higher temperatures, existing techniques have
been unable to produce effective solutions.
SUMMARY OF THE DISCLOSURE
[0007] In some embodiments, certain disadvantages and problems
associated with using thermoelectric devices in high temperature
environments have been substantially reduced or eliminated.
[0008] In accordance with one embodiment of the present disclosure,
a thermoelectric device includes at least one plate and a plurality
of conductors formed on the at least one plate. The plurality of
conductors includes aluminum. The thermoelectric device includes a
plurality of thermoelectric elements that each include a diffusion
barrier coupled to the plurality of conductors using a braze. The
diffusion barrier includes a refractory metal. The braze includes
aluminum.
[0009] In some embodiments, the refractory metal may include
molybdenum. The at least one plate may include aluminum oxide or
aluminum nitride. The braze may include aluminum silicon. The
thermoelectric device may also include a lead. The lead may be
resistance welded to the at least one plate.
[0010] In accordance with another embodiment of the present
disclosure, a method of forming a thermoelectric generator includes
applying a diffusion barrier to a plurality of thermoelectric
elements. The diffusion barrier includes a refractory metal. The
method also includes forming a plurality of conductors on at least
one plate. The plurality of conductors include aluminum. In
addition, the method includes coupling the plurality of conductors
to the plurality of thermoelectric elements using a braze. The
braze includes aluminum.
[0011] Technical advantages of certain embodiments of the present
disclosure include enabling extended temperature operation superior
to existing techniques. Some existing thermoelectric devices
experience rapid degradation due to thermal stresses. Certain
embodiments of the present disclosure provide for the accommodation
of thermal expansion during operation.
[0012] Other technical advantages of the present disclosure will be
readily apparent to one skilled in the art from the following
figures, descriptions, and claims. Moreover, while specific
advantages have been enumerated above, various embodiments may
include all, some, or none of the enumerated advantages.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] For a more complete understanding of the present disclosure
and its advantages, reference is now made to the following
description, taken in conjunction with the accompanying drawings,
in which:
[0014] FIG. 1 illustrates one embodiment of a thermoelectric device
including a plurality of thermoelectric elements disposed between a
cold plate and a hot plate;
[0015] FIG. 2 illustrates one embodiment of a thermoelectric device
capable of operating in high temperatures; and
[0016] FIG. 3 is a flowchart illustrating one embodiment of forming
a thermoelectric device.
DETAILED DESCRIPTION OF THE DISCLOSURE
[0017] FIG. 1 illustrates one embodiment of a thermoelectric device
20 including a plurality of thermoelectric elements 22 disposed
between a cold plate 24 and a hot plate 26. Electrical connections
28 and 30 are provided to allow thermoelectric device 20 to be
electrically coupled with an appropriate source of DC electrical
power or to allow thermoelectric device 20 to be electrically
coupled to one or more devices that use, transform, or store power
when thermoelectric device 20 operates as a generator.
[0018] Thermoelectric device 20 may be used as a heater, cooler,
electrical power generator, and/or temperature sensor. If
thermoelectric device 20 were designed to function as an electrical
power generator, electrical connections 28 and 30 would represent
the output terminals from such a power generator operating between
hot and cold temperature sources.
[0019] FIG. 2 illustrates one embodiment of thermoelectric device
200 capable of operating in high temperatures. This may be an
example of how thermoelectric device 20 may be implemented.
Thermoelectric device 200 may include thermoelectric elements 202
fabricated from dissimilar semiconductor materials such as N-type
thermoelectric elements 202a and P-type thermoelectric elements
202b. Thermoelectric elements 202 are typically configured in a
generally alternating N-type element to P-type element arrangement
and typically include an air gap 204 disposed between adjacent
N-type and P-type elements. In many thermoelectric devices,
thermoelectric materials with dissimilar characteristics are
connected electrically in series and thermally in parallel.
[0020] Examples of thermoelectric devices and methods of
fabrication are shown in U.S. Pat. No. 5,064,476 titled
Thermoelectric Cooler and Fabrication Method; U.S. Pat. No.
5,171,372 titled Thermoelectric Cooler and Fabrication Method; and
U.S. Pat. No. 5,576,512 entitled Thermoelectric Apparatus for Use
With Multiple Power Sources and Method of Operation.
[0021] N-type semiconductor materials generally have more electrons
than necessary to complete the associated crystal lattice
structure. P-type semiconductor materials generally have fewer
electrons than necessary to complete the associated crystal lattice
structure. The "missing electrons" are sometimes referred to as
"holes." The extra electrons and extra holes are sometimes referred
to as "carriers." The extra electrons in N-type semiconductor
materials and the extra holes in P-type semiconductor materials are
the agents or carriers which transport or move heat energy between
cold side or cold plate 206 and hot side or hot plate 208 through
thermoelectric elements 200 when subject to a DC voltage potential.
These same agents or carriers may generate electrical power when an
appropriate temperature difference is present between cold side 206
and hot side 208. Leads 214 may be coupled to plate 208 in a manner
that withstands high temperature environments, such as resistance
welding, tungsten inert gas (TIG) welding, and laser welding.
[0022] In some embodiments, thermoelectric elements 202 may include
high temperature thermoelectric material. Examples of high
temperature thermoelectric materials include lead telluride (PbTe),
lead germanium telluride (PbGeTe), TAGS alloys (such as
(GeTe).sub.0.85(AgSbTe2).sub.0.15), bismuth telluride
(Bi.sub.2Te.sub.3), and skutterudites.
[0023] In some embodiments, thermoelectric elements 202 may include
a diffusion barrier that includes refractory metals (e.g., a metal
with a melting point above 1,850.degree. C.). Suitable refractory
metals may include those that are metallurgically compatible with
high temperature thermoelectric materials and metallurgically
compatible with other components of thermoelectric device 200. For
example, a molybdenum diffusion barrier may be used. This may be
advantageous in that molybdenum may be metallurgically compatible
with various aspects of thermoelectric device 200. For example, as
further discussed below, thermoelectric device 200 may include an
aluminum braze that is metallurgically compatible with a molybdenum
diffusion barrier. Such a diffusion barrier may prevent or reduce
the chance or occurrence of Kirkendall voiding in thermoelectric
device 200. Other suitable examples of a diffusion barrier that has
similar properties to molybdenum include tungsten and titanium.
[0024] In some embodiments, alternating thermoelectric elements 202
of N-type and P-type semiconductor materials may have their ends
connected by electrical conductors 210. Conductors 210 may be
metallizations formed on thermoelectric elements 202 and/or on the
interior surfaces of plates 206 and 208. Conductors 210 may include
aluminum. Ceramic materials may be included in plates 206 and 208
which define in part the cold side and hot side, respectively, of
thermoelectric device 200. In some embodiments, the ceramic
materials may provide electrical isolation from hot and cold side
sources. Aluminum metallized ceramics may accommodate thermal
stresses (i.e., due to high temperature exposure) of the
ceramic/aluminum bond. Examples of suitable ceramic materials
include aluminum oxide, aluminum nitride, and beryllium oxide.
[0025] In some embodiments, thermoelectric elements 202 may be
coupled to plates 206 and 208 using medium 212. Medium 212 may
include brazes and/or solders. For example, aluminum-based brazes
and/or solders may be used, such as aluminum silicon (AlSi) braze
family and/or zinc-aluminum (ZnAl) solder. In some embodiments,
using such brazes and/or solders may provide for high temperature
operation and allow for flexible joints. Kirkendall voiding may be
prevented or reduced.
[0026] In some embodiments, using one or more of the configurations
discussed above, thermoelectric device 200 may be suitable as a
fixed-joint, high temperature thermoelectric generator that is
capable of being used in high temperature applications. For
example, a thermoelectric generator built using skutterudite
thermoelectric elements that include a molybdenum diffusion
barrier, conductors formed by aluminum metallizations, and aluminum
based brazes may result in a device that can operate with at least
one of its plates (such as plates 206 or 208) at a temperature
greater than 500 degrees Celsius. As another example, a
thermoelectric generator built using bismuth telluride
thermoelectric elements that include a molybdenum diffusion
barrier, conductors formed by aluminum metallization, and
zinc-aluminum (ZnAl) solder may result in a device that can operate
with at least one of its plates (such as plates 206 or 208) at a
temperature greater than 300 degrees Celsius.
[0027] FIG. 3 is a flowchart illustrating one embodiment of forming
an thermoelectric device. For example, the steps illustrated in
FIG. 3 may be used to form a thermoelectric generator. In general,
the steps illustrated in FIG. 3 may be combined, modified, or
deleted where appropriate, and additional steps may also be added
to the example operation. Furthermore, the described steps may be
performed in any suitable order.
[0028] At step 310, in some embodiments, a diffusion barrier may be
applied to one or more thermoelectric elements. The diffusion
barrier may be or include refractory metals, such as molybdenum,
tungsten, and titanium. For example, a molybdenum diffusion barrier
metallization may be applied at this step.
[0029] At step 320, in some embodiments, conductors may be formed.
The conductors may be metallizations formed on the thermoelectric
elements and/or formed on plates (e.g., on the interior surfaces of
the plates). The plates may be ceramic plates. The conductors may
be formed of aluminum.
[0030] At step 330, in some embodiments, plates may be coupled to
the thermoelectric elements. For example, the thermoelectric
elements may be coupled to the interior surfaces of two plates
where conductors have been formed (e.g., at step 320) such that the
thermoelectric elements may be disposed between the two plates. The
thermoelectric elements may be coupled to conductors on the plates
such that an N-type thermoelectric element is coupled to a P-type
thermoelectric element. The plates may be coupled to the
thermoelectric elements using brazes and/or solders. For example,
aluminum-based brazes and/or solders may be used, such as aluminum
silicon (AlSi) braze family and/or zinc-aluminum (ZnAl) solder.
[0031] At step 340, in some embodiments, leads may be coupled to at
least one of the plates. This may be performed using resistance
welding, tungsten inert gas (TIG) welding, or laser welding. The
leads may be coupled such that electricity generated by the
thermoelectric device may be sent through the leads to another
device. As another example, the leads may be coupled such that
electricity may be applied to the thermoelectric device.
[0032] Although the present disclosure has been described with
several embodiments, a myriad of changes, variations, alterations,
transformations, and modifications may be suggested to one skilled
in the art, and it is intended that the present disclosure
encompass such changes, variations, alterations, transformations,
and modifications as fall within the scope of the appended
claims.
* * * * *