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.

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:
(M).sub.m(Fe).sub.a(A′).sub.a′(Co).sub.b(B′).sub.b′(Sb).sub.c(C′).sub.c′  [Chemical Formula 1] 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′)≤4, and 0≤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≤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≤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° C. to 1400° C.

7. The method of claim 5, wherein a temperature of the heat-treating of step 1 is 500° C. to 800° 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 of 500° C. to 900° C.

10. A thermoelectric device comprising the thermoelectric material of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) 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

(2) 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

(3) (Step 1)

(4) 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° 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° 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 μm or less.

(5) (Step 2)

(6) The powder produced in step 1 was stored in a glove box with an oxygen concentration of 1 ppm or less for 6 months.

(7) (Step 3)

(8) 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° 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

(9) 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° 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

(10) 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 Al.

Comparative Example 2

(11) The pSKD sintered body was produced in the same method as in Example 1, except that 2.0 wt % of Al is used instead of 0.5 wt % of Al in step 3 of Example 1.

Experimental Example 1: XRD Analysis

(12) 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.

(13) As shown in the FIGURE, AlSb was not observed in the case of Comparative Example 1 in which Al 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.

(14) 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

(15) The sintered bodies produced in the Examples and Comparative Examples were processed into right-angled columns having a size of 3 mm×3 mm×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° C.

(16) In addition, the sintered bodies produced in the Examples and Comparative Examples were processed into a round column with a size of 2 mmT×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° C.

(17) The measurement results are shown in Table 1 below.

(18) TABLE-US-00001 TABLE 1 Addition amount EC S PF TC of Al Composition (Scm.sup.−1) (μVK.sup.−1) (μWcm.sup.−1K.sup.−2) (Wm.sup.−1K.sup.−1) ZT Com- (Not Nd.sub.0.9Fe.sub.3.0Co.sub.1.0Sb.sub.12 1162 112.3 14.58 2.76 0.306 parative added) FeSb.sub.2 19.8 wt % Ex. 1 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 % Com- 2.0 wt % Nd.sub.0.9Fe.sub.3.0Co.sub.1.0Sb.sub.12 1224 118.5 17.03 2.81 0.355 parative FeSb.sub.2 3.7 wt % Ex. 2 AlSb 9.7 wt %

(19) As shown in Table 1, as the addition amount of Al increased, the generation amount of FeSb2 showed a decreasing tendency and the generation amount of AlSb showed an increasing tendency.

(20) 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.