Method for manufacturing magnesium-based thermoelectric conversion material, method for manufacturing magnesium-based thermoelectric conversion element, magnesium-based thermoelectric conversion material, magnesium-based thermoelectric conversion element, and thermoelectric conversion device

Patent metadata

Field	Value
Publication number	US-10468577-B2
Application number	US-201716076868-A
Country	US
Kind code	B2
Filing date	Feb 22, 2017
Priority date	Feb 24, 2016
Publication date	Nov 5, 2019
Grant date	Nov 5, 2019

Abstract

A method for manufacturing a magnesium-based thermoelectric conversion material of the present invention includes a raw material-forming step of forming a raw material for sintering by adding silicon oxide in an amount within a range equal to or greater than 0.5 mol % and equal to or smaller than 13.0 mol % to a magnesium-based compound, and a sintering step of heating the raw material for sintering at a temperature within a range equal to or higher than 750° C. and equal to or lower than 950° C. while applying pressure equal to or higher than 10 MPa to the raw material for sintering so as to form a sintered substance.

First claim

The invention claimed is:

1. A method for manufacturing a magnesium-based thermoelectric conversion material, comprising:
a raw material-forming step of forming a raw material for sintering by adding silicon oxide in an amount within a range equal to or greater than 0.5 mol % and equal to or smaller than 13.0 mol % to a magnesium-based compound; and
a sintering step of heating the raw material for sintering at a temperature within a range equal to or higher than 750° C. and equal to or lower than 950° C. while applying pressure equal to or higher than 10 MPa to the raw material for sintering so as to form a sintered substance.

2. The method for manufacturing a magnesium-based thermoelectric conversion material according to claim 1 ,
wherein the magnesium-based compound is any one of Mg x Si y , Mg 2 Si 1-x Ge x , and Mg 2 Si 1-x Sn x .

3. The method for manufacturing a magnesium-based thermoelectric conversion material according to claim 1 ,
wherein the raw material for sintering further contains, as a dopant, at least one kind of element among Li, Na, K, B, Al, Ga, In, N, P, As, Sb, Bi, Ag, Cu, and Y.

4. The method for manufacturing a magnesium-based thermoelectric conversion material according to claim 1 ,
wherein the sintering step is performed by any of a hot pressing method, a hot isostatic pressing method, a discharge plasma sintering method, an energizing sintering method, a hot rolling method, a hot extrusion method, and a hot forging method.

5. The method for manufacturing a magnesium-based thermoelectric conversion material according to claim 1 ,
wherein the sintering step is performed in a vacuum atmosphere under a pressure equal to or lower than 5 Pa or in an inert gas atmosphere.

6. A method for manufacturing a magnesium-based thermoelectric conversion element, comprising:
an electrode-forming step of joining electrodes to one surface and the other surface, facing the one surface, of the sintered substance obtained by the method for manufacturing a magnesium-based thermoelectric conversion material according to claim 1 respectively.

7. A magnesium-based thermoelectric conversion material, comprising:
a sintered substance of a magnesium-based compound,
wherein grains of a reaction product are present in the sintered substance,
each of the grains of the reaction product is constituted with a modified product and a high-concentration silicon region formed on the periphery of the modified product,
the modified product contains magnesium at a concentration within a range equal to or higher than 30 at % and equal to or lower than 50 at %, silicon at a concentration within a range equal to or higher than 0 at % and equal to or lower than 20 at %, and oxygen at a concentration within a range equal to or higher than 40 at % and equal to or lower than 55 at %, and
a number density of the grains of the reaction product is equal to or higher than 50 grains/mm 2 and equal to or lower than 700 grains/mm 2 .

8. The magnesium-based thermoelectric conversion material according to claim 7 ,
wherein a average grain size of the grains of the reaction product is equal to or greater than 0.5 μm and equal to or smaller than 100 μm.

9. The magnesium-based thermoelectric conversion material according to claim 7 ,
wherein on a grain boundary of grain of the magnesium-based compound, a Si-rich phase having a Si concentration higher than that in the grain of the magnesium-based compound is formed.

10. The magnesium-based thermoelectric conversion material according to claim 7 ,
wherein a lattice constant difference obtained by subtracting a lattice constant of raw material powder formed of the magnesium-based compound from a lattice constant of the magnesium-based thermoelectric conversion material (lattice constant of magnesium-based thermoelectric conversion material—lattice constant of raw material powder formed of magnesium-based compound) is equal to or greater than 0.0005 angstrom (Å).

11. A magnesium-based thermoelectric conversion element, comprising:
the magnesium-based thermoelectric conversion material according to claim 7 ; and
electrodes joined to one surface and the other surface, facing the one surface, of the magnesium-based thermoelectric conversion material respectively.

12. The magnesium-based thermoelectric conversion element according to claim 11 ,
wherein the magnesium-based thermoelectric conversion element is a Seebeck element in which the one surface or the other surface of the magnesium-based thermoelectric conversion material is heated such that a potential difference is caused between the electrodes.

13. The magnesium-based thermoelectric conversion element according to claim 11 ,
wherein the magnesium-based thermoelectric conversion element is a Peltier element in which voltage is applied between the electrodes such that the one surface or the other surface of the magnesium-based thermoelectric conversion material is cooled.

14. A thermoelectric conversion device, comprising:
a plurality of the magnesium-based thermoelectric conversion elements according to claim 11 ,
wherein the magnesium-based thermoelectric conversion elements are arranged and electrically connected to each other in series through the electrodes.

15. The thermoelectric conversion device according to claim 14 ,
wherein the magnesium-based thermoelectric conversion elements include p-type thermoelectric conversion elements and n-type thermoelectric conversion elements including the magnesium-based thermoelectric conversion material containing a donor, and
the n-type thermoelectric conversion elements and the p-type thermoelectric conversion elements are alternately connected to each other in series.

16. The thermoelectric conversion device according to claim 14 ,
wherein the magnesium-based thermoelectric conversion elements are formed of n-type thermoelectric conversion elements including the magnesium-based thermoelectric conversion material containing a donor or p-type thermoelectric conversion elements including the magnesium-based thermoelectric conversion material containing an acceptor, and
the n-type thermoelectric conversion elements or the p-type thermoelectric conversion elements are connected to each other in series.

Assignees

• Mitsubishi Materials Corp

Inventors

• Nakada Yoshinobu

Classifications

• C04B2235/40

  Metallic constituents or additives not added as binding phase · CPC title

• B22F2003/208

  Warm or hot extruding · CPC title

• C04B2235/80

  Phases present in the sintered or melt-cast ceramic products other than the main phase · CPC title

• B22F3/1039

  by reaction (B22F3/001, B22F3/23 take precedence) · CPC title

• C04B2235/407

  Copper · CPC title