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US-12622172-B2 - Thermoelectric material, method for producing same, and thermoelectric power generation element

US12622172B2US 12622172 B2US12622172 B2US 12622172B2US-12622172-B2

Abstract

Provided are a thermoelectric material having excellent thermoelectric characteristics at room temperature; a method for producing same; and a thermoelectric power generation element. In an embodiment of the present invention, the thermoelectric material contains an inorganic compound containing magnesium (Mg), silver (Ag), antimony (Sb) and copper (Cu), and is represented by the formula Mg 1−a Cu a Ag b Sb c , and the parameters a, b and c satisfy: 0<a≤0.1, 0.95≤b≤1.05 and 0.95≤c≤1.05. The inorganic compound may be an α phase of a half-Heusler structure and have the symmetry of the space group I-4c2.

Inventors

  • Takao Mori
  • Zihang LIU

Assignees

  • NATIONAL INSTITUTE FOR MATERIALS SCIENCE

Dates

Publication Date
20260505
Application Date
20210825
Priority Date
20200916

Claims (17)

  1. 1 . A thermoelectric material comprising an inorganic compound comprising: magnesium (Mg), silver (Ag), antimony (Sb), and copper (Cu), wherein the inorganic compound is represented by Mg 1-a Cu a Ag b Sb c , wherein the parameters a, b and c satisfy: 0<a<0.1, 0.95≤b≤1.05, and 0.95<c<1.05 wherein the inorganic compound comprises α-phase of a half-Heusler structure, in which Mg sites are partially replaced with Cu, and a symmetry of space group I-4c2.
  2. 2 . The thermoelectric material according to claim 1 wherein the parameter a satisfies: 0.005≤a≤0.05.
  3. 3 . The thermoelectric material according to claim 2 wherein the parameter a satisfies: 0.005≤a≤0.02.
  4. 4 . The thermoelectric material according to claim 3 wherein the thermoelectric material comprises p-type.
  5. 5 . The thermoelectric material according to claim 2 wherein the thermoelectric material comprises p-type.
  6. 6 . The thermoelectric material according to claim 2 wherein the thermoelectric material comprises a form selected from a group consisting of a powder, a sintered body and a film.
  7. 7 . The thermoelectric material according to claim 1 wherein the thermoelectric material comprises p-type.
  8. 8 . The thermoelectric material according to claim 1 wherein the thermoelectric material comprises a form selected from a group consisting of a powder, a sintered body and a film.
  9. 9 . The thermoelectric material according to claim 1 wherein the thermoelectric material comprises a thin film and an organic material.
  10. 10 . A method of manufacturing a thermoelectric material as defined in claim 1 comprising the steps of: blending a raw material comprising magnesium (Mg), a raw material comprising silver (Ag), a raw material comprising antimony (Sb), and a raw material comprising copper (Cu) and preparing a mixture thereof, and sintering the mixture.
  11. 11 . The method according to claim 10 wherein the preparing the mixture comprises: mechanical alloying the raw material comprising magnesium (Mg), the raw material comprising silver (Ag), and the raw material comprising copper (Cu); and mechanical alloying the raw material comprising Sb and a Mg—Ag—Cu alloy obtained by the previous mechanical alloying.
  12. 12 . The method according to claim 10 wherein the sintering comprises spark plasma sintering.
  13. 13 . The method according to claim 12 wherein the spark plasma sintering comprises sintering in a temperature range of at least 473 K and not exceeding 773 K, under a pressure of at least 50 MPa and not exceeding 100 MPa, for a duration of at least 1 minute and not exceeding 10 minutes.
  14. 14 . The method according to claim 10 , comprising pulverizing a sintered body obtained by the sintering.
  15. 15 . The method according to claim 14 , comprising mixing a powder obtained by the pulverizing with an organic material.
  16. 16 . The method according to claim 10 , comprising performing a physical vapor deposition method using, as a target, a sintered body having been obtained by the sintering.
  17. 17 . A thermoelectric power generation element comprising p-type and n-type thermoelectric materials connected in series alternately, wherein the p-type thermoelectric material comprises a thermoelectric material as defined in claim 1 .

Description

TECHNICAL FIELD This invention relates to a thermoelectric material, a method for producing the same, and a thermoelectric power generation element and specifically relates to a thermoelectric material containing a MgAgSb-based thermoelectric material, a method for producing the same, and a thermoelectric power generation element thereof. BACKGROUND ART It is a current situation that about three-fourths of the primary supply energy are disposed of as thermal energy in the waste heat recovery in our country where energy conservation is particularly advanced in the world. Under such a circumstance, a thermoelectric power generation element is attracting attention as a solid-state element that can recover the thermal energy and directly convert the thermal energy into the electric energy. Since the thermoelectric power generation element is a direct conversion element into the electrical energy, it has an advantage in the easy maintenance such as ease of maintenance and scalability due to the absence of movable parts. Therefore, an active material research has been conducted with respect to thermoelectric semiconductors as an IoT operating power supply. For IoT operation power supply applications, a thermoelectric material is expected to be used practically near room temperature and the thermoelectric material with the highest performance near room temperature is typically a Bi2Te3-based material, which has a disadvantage in a wide range of practical application due to the scarcity of Te. While only few materials having relatively high performance at room temperature other than the Te compounds were recognized, a MgAgSb-based material, however, has been proposed as a candidate (for example, Patent References 1 and 2). According to Patent Reference 1, the formula Ax−wBy+wCz−wDw (A is one or more elements selected from the group consisting of Mg, Ca, Sr, Ba, Eu, Yb, Ti, Mn, Fe, Ni, Cu, Zn, Cd, Hg and a combination thereof; B is one or more elements selected from the group consisting of Na, K, Rb, Cs, Cu, Ag, Au and a combination thereof; C is one or more elements selected from the group consisting of As, Sb, Bi and a combination thereof; and D is one or more elements selected from the group consisting of Se, Te and a combination thereof; and w is from about 0 to about 1; x is from about 0.9 to about 1.1; y is from about 0.9 to about 1.1; and z is from about 0.9 to about 1.1) material is disclosed. According to Patent Reference 2, the X1−nAnY1−mBmZ1−qCq (X, Y and Z are Mg, Ag and Sb, respectively; and n, m and q are from about 0.0001 to about 0.5000, respectively) material is disclosed. As an important characteristic factor of the thermoelectric material, there is the dimensionless thermoelectric figure of merit ZT, which is represented by the following equation. ZT=S2T/(ρ·k) Here, S is a Seebeck coefficient, ρ is an electric resistivity, T is an absolute temperature, and k is a thermal conductivity. Furthermore, S2/ρ is a power factor (also called electrical output factor), which corresponds to the power generated per unit temperature. That is, in order to improve ZT, it is effective to improve the power factor and reduce the thermal conductivity k. The thermal conductivity k can be selectively reduced by controlling the morphology of the material, but it is necessary to modify the material in order to improve the power factor. Even in the above mentioned Patent References 1 and 2, the power factor is not sufficient at room temperature. To considering IoT power generation applications, it is expected that a thermoelectric material having a high power factor exceeding 25 μWcm−1 K−2 at room temperature will be developed. PRIOR ART REFERENCE Patent Reference [Patent Reference 1] US Patent Application Publication No. 2009/0211619, specification. [Patent Reference 2] US Patent Application Publication No. 2016/0326615, specification. SUMMARY OF THE INVENTION Problem to be Solved by the Invention From the above, in an embodiment of the present invention, it is an issue to provide a thermoelectric material with excellent thermoelectric properties at room temperature, a manufacturing method thereof, and a thermoelectric power generation element thereof. Means to Solve the Problem In an embodiment of the present invention, the thermoelectric material includes an inorganic compound containing magnesium (Mg), silver (Ag), antimony (Sb), and copper (Cu), and the inorganic compound is represented by Mg1−aCuaAgbSbc, where the parameters a, b and c satisfy: 0<a≤0.1, 0.95≤b≤1.05, and 0.95≤c≤1.05. The above-mentioned issue is solved. The parameter a may satisfy: 0.005≤a≤0.05. The parameter a may satisfy: 0.005≤a≤0.02. The inorganic compound may be an alpha (α) phase of a half-Heusler structure and have the symmetry of the space group I-4c2. The thermoelectric material may be p-type. The thermoelectric material may be in a form selected from the group consisting of a powder, a sintered body and a thin film. The thermoelectr