U.S. patent application number 16/623262 was filed with the patent office on 2021-10-28 for thermoelectric material and thermoelectric device including the same.
This patent application is currently assigned to LG CHEM, LTD.. The applicant listed for this patent is LG CHEM, LTD.. Invention is credited to Jaehyun KIM, Sujeong LEE, Yeseul LEE, Cheol Hee PARK.
Application Number | 20210336117 16/623262 |
Document ID | / |
Family ID | 1000005895414 |
Filed Date | 2021-10-28 |
United States Patent
Application |
20210336117 |
Kind Code |
A1 |
KIM; Jaehyun ; et
al. |
October 28, 2021 |
THERMOELECTRIC MATERIAL AND THERMOELECTRIC DEVICE INCLUDING THE
SAME
Abstract
A thermoelectric material which minimize the content of
components that degrade thermoelectric performance and thus can be
usefully used in thermoelectric devices including the same.
Inventors: |
KIM; Jaehyun; (Daejeon,
KR) ; LEE; Sujeong; (Daejeon, KR) ; LEE;
Yeseul; (Daejeon, KR) ; PARK; Cheol Hee;
(Daejeon, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LG CHEM, LTD. |
Seoul |
|
KR |
|
|
Assignee: |
LG CHEM, LTD.
Seoul
KR
|
Family ID: |
1000005895414 |
Appl. No.: |
16/623262 |
Filed: |
May 8, 2019 |
PCT Filed: |
May 8, 2019 |
PCT NO: |
PCT/KR2019/005996 |
371 Date: |
December 16, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 35/18 20130101;
C22C 12/00 20130101; H01L 35/34 20130101 |
International
Class: |
H01L 35/18 20060101
H01L035/18; H01L 35/34 20060101 H01L035/34; C22C 12/00 20060101
C22C012/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 11, 2018 |
KR |
10-2018-0066825 |
Claims
1. A thermoelectric material comprising: a p-type skutterudite
material of the following Chemical Formula 1, AlSb in an amount
greater than 0 wt % and 7.5 wt % or less relative to a total amount
of the thermoelectric material, and FeSb.sub.2 in an amount greater
than 0 wt % and 20 wt % or less relative to the total amount of the
thermoelectric material: [Chemical Formula 1]
(M).sub.m(Fe).sub.x(A').sub.a'(Co).sub.b(B').sub.b'(Sb).sub.c(C').sub.c'
wherein, in Chemical Formula 1, M is at least one element selected
from the group consisting of S, In, Nd, Pr, Ce, Yb, La, Sr, Ba, Ca,
Sm, Eu, and Gd, 0<m<1.5, A' is at least one element selected
from the group consisting of Ni, Mn, Tc, and Pd,
1<(a+a').ltoreq.4, and 0.ltoreq.a'<1, B' is at least one
element selected from the group consisting of Ni, Ru, Os, Ir, and
Pt, 0<(b+b')<3, and 0.ltoreq.b'<1, C' is at least one
element selected from the group consisting of Sn and Te, and
11<(c+c')<13.5, and 0.ltoreq.c'<1.
2. The thermoelectric material according to claim 1, wherein the m
is 0.5 to 1.0.
3. The thermoelectric material according to claim 1, wherein the
amount of AlSb is 1 wt % to 5 wt % relative to the total amount of
the thermoelectric material.
4. The thermoelectric material according to claim 1, wherein the
amount of FeSb.sub.2 is 5 wt % to 15 wt % relative to the total
amount of the thermoelectric material.
5. A method for producing the thermoelectric material of claim 1,
the method comprising the steps of: 1) mixing M, Fe, A', Co, B',
Sb, and C' at a molar ratio of m:a:a':b:b':c:c', and then heating
and heat-treating the mixture to produce an ingot; 2) pulverizing
the ingot produced above to produce a pulverized powder; and 3)
mixing the pulverized powder with an Al powder wherein an amount of
the Al powder is greater than 0 wt % and 1.5 wt % or less relative
to a total weight of the pulverized powder and then sintering the
resulting mixture: wherein M, A', B', C', m, a, a', b, b', c and c'
are as defined in claim 1.
6. The method of claim 5, wherein a temperature of the heating of
step 1 is 600.degree. C. to 1400.degree. C.
7. The method of claim 5, wherein a temperature of the heating of
step 1 is 500.degree. C. to 800.degree. C.
8. The method of claim 5, wherein the amount of Al powder in the
step 3 is 0.5 wt % to 1.0 wt % relative to the total weight of the
pulverized powder.
9. The method of claim 5, wherein the sintering is cared out at a
temperature 500.degree. C. to 900.degree. C.
10. A thermoelectric device comprising the thermoelectric material
of claim 1.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application claims the benefit of the filing date of
Korean Patent Application No. 10-2018-0066825 filed with the Korean
Intellectual Property Office on Jun. 11, 2018, the entire content
of which is incorporated herein by reference.
TECHNICAL FIELD
[0002] The present invention relates to a thermoelectric material
minimizing the content of components that degrade thermoelectric
performance, and a thermoelectric device including the same.
BACKGROUND ART
[0003] Recently, with interest in the development and saving of
alternative energy being heightened, investigation and research on
efficient energy conversion materials are actively conducted. In
particular, research on thermoelectric materials, which are
thermoelectric energy conversion materials, is being
accelerated.
[0004] These thermoelectric materials are metal or ceramic
materials having a function to directly convert heat to electricity
or inversely convert electricity to heat, and have the advantage
that power can be generated even in the absence of moving parts
when a temperature difference is applied. After the discovery of
their thermoelectric phenomena, namely Seebeck effect, Peltier
effect, and Thomson effect at the beginning of the 19th century,
these thermoelectric materials have been developed so as to have a
high thermoelectric performance index as semiconductors have
progressed since the late 1930s.
[0005] Meanwhile, as next-generation materials having
thermoelectric energy conversion characteristics, skutterudite
compounds are researched. Skutterudite compounds have abundant
potential as materials that are expected to improve their
thermoelectric energy conversion characteristics by the decrease of
lattice thermal conductivity.
[0006] Meanwhile, a method for producing a thermoelectric material
containing skutterudite generally includes three stages, wherein a
raw material is first heated under various conditions in accordance
with the chemical composition of the target thermoelectric
material, and subjected to heat treatment to synthesize an
ingot-shaped material. This is pulverized and classified to produce
a powder, which is then sintered at high temperature and high
pressure to produce a thermoelectric material.
[0007] By the way, the production method including the synthesis,
pulverization, classification and sintering as described above is
expensive to apply in a continuous process, and therefore, in the
industrial production, in consideration of economic efficiency, the
thermoelectric material powder is first mass-produced as described
above, and subsequently, the powder is sintered to produce the
thermoelectric material. In other words, the production process of
the powder is more economical as mass production becomes possible,
and the sintering process of the powder has a long process time due
to the high temperature process characteristics. Thus, it takes a
considerable amount of time between the powder mass production
process and the sintering process and therefore inevitably stores
the powder for a long time.
[0008] Meanwhile, the present inventors have found that the
performance of the thermoelectric material finally produced greatly
depends on the storage conditions of the skutterudite powder
produced by the above-mentioned method. In particular, as described
in detail below, it has been confirmed that materials that degrade
the performance of the thermoelectric material are found in the
thermoelectric material produced while the skutterudite powder is
stored for a long time.
[0009] In this regard, the present inventors have conducted an
intensive research on a method for preventing the performance of
the thermoelectric material from degrading even when producing the
thermoelectric material after the powder is stored for a long time
as described above, and as a result, have found that when using the
thermoelectric material and the production method thereof as
described below, the above-mentioned problems are solved, thereby
completing the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Technical Problem
[0010] It is an object of the present invention to provide a
thermoelectric material minimizing the content of components that
degrade thermoelectric performance, and a thermoelectric element
including the thermoelectric material.
Technical Solution
[0011] In order to achieve that above objects, one embodiment of
the present invention provides a thermoelectric material comprising
a p-type skutterudite material of the following Chemical Formula 1,
AlSb in an amount greater than 0 wt % and 7.5 wt % or less relative
to a total amount of the thermoelectric material, and FeSb.sub.2 in
an amount greater than 0 wt % and 20 wt % or less of relative to a
total amount of the thermoelectric material:
[Chemical Formula 1]
(M).sub.m(Fe).sub.a(A').sub.a'(Co).sub.b(B').sub.b'(Sb).sub.c(C').sub.c'
[0012] wherein, in Chemical Formula 1,
[0013] M is at least one of element selected from the group
consisting of S, In, Nd, Pr, Ce, Yb, La, Sr, Ba, Ca, Sm, Eu, and
Gd,
[0014] 0<m<1.5,
[0015] A' is at least one of element selected from the group
consisting of Ni, Mn, Tc, and Pd,
[0016] 1<(a+a').ltoreq.4, and 0.ltoreq.a'<1,
[0017] B' is at least one of element selected from the group
consisting of Ni, Ru, Os, Ir, and Pt,
[0018] 0<(b+b')<3, and 0.ltoreq.b'<1,
[0019] C' is at least one of element selected from the group
consisting of Sn and Te, and
[0020] 11<(c+c')<13.5, and 0.ltoreq.c'<1.
[0021] As used herein, the term `p-type skutterudite material`
refers to a compound represented by Chemical Formula 1 as defined
above, and corresponds to a main component of a thermoelectric
material in the present invention.
[0022] The p-type skutterudite-based thermoelectric materials as
described above is generally produced by a method for producing the
thermoelectric materials including the steps of heating raw
materials under various conditions in accordance with the chemical
composition, subjecting them to heat treatment to produce an
ingot-shaped material, pulverizing and classifying the resultant
material to produce a powder, and then sintering the powder at high
temperature and high pressure. In industrial production, the
skutterudite material is produced by mass-producing the powder and
then sintering it for economic reasons. In this process, sintering
is proceeded after the powder is stored for a long time. The
long-term storage causes a problem that the performance of the
thermoelectric material is greatly deteriorated.
[0023] In particular, the "p-type skutterudite" of the present
invention contains Fe and Sb elements. Although not theoretically
limited, the performance degradation of the thermoelectric material
as described above is attributable to the generation of FeSb.sub.2
due to long-term storage, as in the Examples and Comparative
Examples of the present invention. In addition, the "p-type
skutterudite" of the present invention also contains Co element,
and thus the FeSb.sub.2 may also exist in the form of
(Fe/Co)Sb.sub.2. Therefore, FeSb.sub.2 described herein means also
including (Fe/Co)Sb.sub.2.
[0024] Therefore, according to the present invention, in the
production of the thermoelectric material, a small amount of Ai is
added and sintered together during the sintering of p-type
skutterudite powder, and thereby a small amount of AlSb is
generated in the thermoelectric material. As a result, it is
possible to reduce the generation of FeSb.sub.2 which degrades the
performance of a thermoelectric material.
[0025] Preferably, m is 0.5 to 1.0. Also, preferably, the M is
Nd.
[0026] The a is preferably 2.ltoreq.a.ltoreq.4, and most preferably
3.
[0027] The b is preferably 0.5.ltoreq.b.ltoreq.2, and most
preferably 1.
[0028] The c is preferably 11.5.ltoreq.c.ltoreq.12.5, and most
preferably 12.
[0029] The a', b', and c' mean the amounts of elements that are
substituted and entered into Fe, Co, and Sb sites, respectively.
The a', b', and c' are each less than 1, and when a', b', and c'
are 0, it means that there is no element substituted.
[0030] Meanwhile, the content of the AlSb and FeSb.sub.2 mean being
based on the total mass of the thermoelectric material described
above. For example, when AlSb and FeSb.sub.2 are respectively
included at 5 wt %, it means that the thermoelectric material
contains 5 wt % of AlSb, 5 wt % of FeSb.sub.2, and 90 wt % of the
p-type skutterudite material. In one embodiment, the AlSb is
contained in an amount of 1 wt % to 5 wt %. In one embodiment, the
FeSb.sub.2 is contained in an amount of 5 wt % to 15 wt %.
[0031] As described below, the AlSb is generated by adding Ai
during the production of the thermoelectric material, and is
contained in an amount of greater than 0 wt % and 7.5 wt % or less
in the thermoelectric material of the present invention. Although
not theoretically limited, as Al is sintered together, Al and Sb
are combined to form AlSb, and thereby, the generation of
FeSb.sub.2 is suppressed and as a result, it is possible to prevent
the performance of the thermoelectric material from
deteriorating.
[0032] As the generation of AlSb increases, the generation of
FeSb.sub.2 lowers, and as the generation amount of AlSb increases,
the performance of the thermoelectric material is improved.
However, when the generation amount of AlSb is excessively large,
the performance of the thermoelectric material is deteriorated.
Therefore, preferably, the generation amount of AlSb is preferably
7.0 wt % or less, 6.5 wt % or less, 5.0 wt % or less, 4.5 wt % or
less, or 4.0 wt % or less in the thermoelectric material. Further,
preferably, the generation amount of AlSb is 0.5 wt % or more, 1.0
wt % or more, or 1.5 wt % or more in the thermoelectric
material.
[0033] As AlSb is generated, the generation amount of FeSb.sub.2
decreases. Preferably, it is 20 wt % or less, 19 wt % or less, 18
wt % or less, 17 wt % or less, 16 wt % or less, 15 wt % or less, 14
wt % or less, 13 wt % or less, or 12 wt % or less in the
thermoelectric material.
[0034] Another embodiment of the present invention provides a
method for producing the thermoelectric material described above,
comprising the steps of:
[0035] 1) mixing M, Fe, A', Co, B', Sb, and C' at a molar ratio of
m:a:a':b:b':c:c, and then heating and heat-treating the mixture to
produce an ingot;
[0036] 2) pulverizing the ingot produced above to produce a
pulverized powder; and
[0037] 3) mixing the pulverized powder with an Ai powder, wherein
an amount of the Al powder is greater than 0 wt % and 1.5 wt % or
less relative to a total weight of the pulverized powder and then
sintering the resulting mixture:
[0038] wherein M, A', B', C', m, a, a', b, b', c and c' are as
defined above.
[0039] Step 1 is a step of mixing the components of the
thermoelectric material and heating and heat-treating the mixture
to produce an ingot.
[0040] Preferably, the heating temperature is 600 to 1400.degree.
C. Preferably, the heating time is 10 to 200 hours. Preferably, the
heat treatment temperature is 500 to 800.degree. C. Preferably, the
heat treatment time is 10 to 200 hours. Thereby, the components of
the thermoelectric material are finally melted to prepare an
ingot-shaped material.
[0041] Step 2 is a step of pulverizing the ingot produced in step 1
to produce a powder.
[0042] The powder may be pulverized so as to have a particle size
of 100 .mu.m or less, and a classification step may be added as
necessary. As the pulverization/classification method and apparatus
therefor, the methods and apparatuses used in the field of
inorganic materials can be applied without limitation.
[0043] Step 3 is a step of sintering the pulverized powder produced
in step 2.
[0044] As described above, step 2 and step 3 are difficult to apply
in a continuous process, in industrial production, and therefore, a
thermoelectric material is produced by mass-producing a powder as
in steps 1 and 2, and then sintering the powder as in step 3. This
greatly affects the performance of the thermoelectric material
depending on the conditions under which the powder is stored
between step 2 and step 3.
[0045] However, in the present invention, by adding Ai to the
powder and sintering together as in step 3, it is possible to
minimize the content of components that degrade performance in the
thermoelectric material.
[0046] The addition amount of Ai is a factor for determining the
content of AlSb and FeSb.sub.2 in the above-mentioned
thermoelectric material. Therefore, by adjusting the addition
amount of Ai, it is possible to adjust the content of AlSb and
FeSb.sub.2. Preferably, the addition amount of Ai is 0.1 wt % or
more, 0.2 wt % or more, 0.3 wt % or more, 0.4 wt % or more, or 0.5
wt % or more, and 1.4 wt % or less, 1.3 wt % or less, 1.2 wt % or
less, 1.1 wt % or less, or 1.0 wt % or less, relative to the powder
produced in step 2. In one embodiment, the addition amount of Al is
0.5 wt % to 1.0 wt % relative to the pulverized powder.
[0047] The sintering may be carried out at a temperature of about
500 to 900.degree. C. using a spark plasma sintering. Preferably
the sintering temperature is 600 to 680.degree. C. In addition, the
sintering time is preferably 1 minute to 600 minutes at a pressure
of 0.1 to 100 MPa.
[0048] Still another embodiment of the present invention provides a
thermoelectric device comprising the above-mentioned thermoelectric
material.
Advantageous Effects
[0049] As described above, the thermoelectric material according to
the present invention minimizes the content of components that
degrade thermoelectric performance and thus can be usefully used
for thermoelectric devices including the same.
BRIEF DESCRIPTION OF THE DRAWINGS
[0050] The FIGURE shows an XRD graph of thermoelectric materials
produced in Examples and Comparative Examples according to the
present disclosure.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0051] Hereinafter, preferred examples are provided to facilitate
understanding of the present invention. However, the following
examples are merely provided for a better understanding of the
present invention, and the scope of the present invention is not
limited thereto.
Comparative Example 1
[0052] (Step 1)
[0053] High purity raw materials, Nd, Fe, Co and Sb were weighed in
a glove box at a molar ratio of 0.9:3.0:1.0:12.1, put into a
graphite crucible and then charged into a quartz tube. In the case
of Sb, it was added by a molar ratio of 0.1 for volatilization. The
inside of the quartz tube was sealed in a vacuum state. Then, the
raw material was heated at 1000 to 1200.degree. C. and kept
constant temperature state in the furnace for 24 hours. Next, the
quartz tube was naturally cooled to room temperature to form an
ingot, which was then again kept constant temperature state in a
furnace at 600 to 750.degree. C. for 120 hours and subjected to
heat treatment. The heat-treated ingot material was pulverized and
classified into a powder having a particle size of 75 .mu.m or
less.
[0054] (Step 2) The powder produced in step 1 was stored in a glove
box with an oxygen concentration of 1 ppm or less for 6 months.
[0055] (Step 3)
[0056] 7 g of the powder produced in step 2 was put into a 0.5-inch
SUS mold and cold-pressed at a pressure of 0.5 to 1 ton to prepare
a pSKD pellet. The prepared pellet was put into a 0.5-inch carbon
mold and subjected to a high-temperature pressurization at
650.degree. C. and 50 MPa for 10 minutes through a spark plasma
sintering (SPS) device to prepare a 0.5-inch pSKD sintered
body.
Example 1
[0057] Powders were prepared in the same manner as in steps 1 and 2
of Comparative Example 1. 0.5 wt % of Al was mixed with 7 g of the
powder. This was put into 0.5-inch sus-mold and cold-pressed at 0.5
to 1 ton to prepare a pSKD pellet. The prepared pellet was put into
a 0.5-inch carbon mold and subjected to a high-temperature
pressurization at 650.degree. C. and 50 Mpa for 10 minutes through
a Spark plasma sintering (SPS) device to produce a 0.5-inch pSKD
sintered body.
Example 2
[0058] The pSKD sintered body was produced in the same method as in
Example 1, except that 1.0 wt % of Al was used instead of 0.5 wt %
of A.
Comparative Example 2
[0059] The pSKD sintered body was produced in the same method as in
Example 1, except that 2.0 wt % of Ai is used instead of 0.5 wt %
of Al in step 3 of Example 1.
Experimental Example 1: XRD Analysis
[0060] The phases of the P-type skutterudite thermoelectric
materials prepared in Examples and Comparative Examples were
analyzed by an X-ray diffractometer (XRD) and the results are shown
in the FIGURE.
[0061] As shown in the FIGURE, AlSb was not observed in the case of
Comparative Example 1 in which Ai was not added. Further, it was
confirmed that the degree of generation of FeSb.sub.2 was lowered
depending on the degree of addition of Al.
[0062] Meanwhile, after XRD measurement, the composition and
content of the chemical materials included were calculated through
Rietveld refinement (RWP<10), and the results are shown in Table
1 below.
Experimental Example 2: Performance Evaluation of Thermoelectric
Materials
[0063] The sintered bodies produced in the Examples and Comparative
Examples were processed into right-angled columns having a size of
3 mm.times.3 mm.times.12 mmH, and then electrical conductivity (EC)
and Seebeck coefficient (S) were measured using ZEM3 (Ulbac) and
LSR3 (Linseis) instruments. For comparison of the representative
values of electrical characteristics, the comparative evaluation
was performed by calculating the average values of the measurement
evaluations at 100, 200, 300, 400, and 500.degree. C.
[0064] In addition, the sintered bodies produced in the Examples
and Comparative Examples were processed into a round column with a
size of 2 mmT.times.0.5 inch D, and the thermal diffusivity was
evaluated using a LFA457 (Netzsch) instrument. The thermal
conductivity (TC) was calculated from the measured thermal
diffusivity, the apparent density of each sintered body, and the
specific heat calculated by Dulong-Petit law. For comparison of the
representative values of the heat transfer characteristics, a
comparative evaluation was performed by calculating the average
value of the thermal conductivity measurement evaluations at 100,
200, 300, 400, and 500.degree. C.
[0065] The measurement results are shown in Table 1 below.
TABLE-US-00001 TABLE 1 Addition EC S PF TC amount of Al Composition
(Scm.sup.-1) (.mu.VK.sup.-1) (.mu.Wcm.sup.-1K.sup.-2)
(Wm.sup.-1K.sup.-1) ZT Comparative (Not added)
Nd.sub.0.9Fe.sub.3.0Co.sub.1.0Sb.sub.12 1162 112.3 14.58 2.76 0.306
Ex. 1 FeSb.sub.2 19.8 wt % AlSb 0 wt % Ex. 1 0.5 wt %
Nd.sub.0.9Fe.sub.3.0Co.sub.1.0Sb.sub.12 1090 125.7 17.13 2.51 0.394
FeSb.sub.2 12 wt % AlSb 1.8 wt % Ex. 2 1.0 wt %
Nd.sub.0.9Fe.sub.3.0Co.sub.1.0Sb.sub.12 1063 128.1 17.35 2.46 0.410
FeSb.sub.2 10 wt % AlSb 4.0 wt % Comparative 2.0 wt %
Nd.sub.0.9Fe.sub.3.0Co.sub.1.0Sb.sub.12 1224 118.5 17.03 2.81 0.355
Ex. 2 FeSb.sub.2 3.7 wt % AlSb 9.7 wt %
[0066] As shown in Table 1, as the addition amount of Al increased,
the generation amount of FeSb.sub.2 showed a decreasing tendency
and the generation amount of AlSb showed an increasing
tendency.
[0067] In addition, as shown in Examples 1 and 2, when the addition
amount of Al was 0.5 wt % and 1.0 wt %, the thermoelectric material
performance showed an increasing tendency. However, when the
addition amount of Al was 2.0 wt % as in Comparative Example 2, the
thermoelectric material performance was reduced, such as a decrease
in the ZT coefficient. This is not limited in theory, but it is
believed that the generation of AlSb increases which thus adversely
affects the thermoelectric material.
* * * * *