Thermoelectric conversion element and thermoelectric conversion module
The thermoelectric conversion element according to the present disclosure comprises a first electrode, a second electrode, a first intermediate layer, a second intermediate layer, and a thermoelectric conversion layer. The first intermediate layer is provided between the thermoelectric conversion layer and the first electrode. The first intermediate layer is in contact with the thermoelectric conversion layer. The first electrode is in contact with the first intermediate layer. The second intermediate layer is provided between the thermoelectric conversion layer and the second electrode. The second intermediate layer is in contact with the thermoelectric conversion layer. The second electrode is in contact with the second intermediate layer. The first electrode and the second electrode are composed of a CuZn alloy. The thermoelectric conversion layer is composed of a thermoelectric conversion material containing Mg. The thermoelectric conversion material contains at least one kind of element selected from the group consisting of Sb and Bi. The thermoelectric conversion material contains at least one kind of element selected from the group consisting of Se and Te. The thermoelectric conversion material has a La 2 O 3 -type crystalline structure. A composition of the first intermediate layer is different from both a composition of the first electrode and a composition of the thermoelectric conversion layer. A composition of the second intermediate layer is different from both a composition of the second electrode and a composition of the thermoelectric conversion layer.
1. A thermoelectric conversion element, comprising:
a first electrode;
a second electrode;
a first intermediate layer;
a second intermediate layer;
a first external electrode connected to the first electrode via a first joint layer;
a second external electrode connected to the second electrode via a second joint layer; and
a thermoelectric conversion layer, wherein:
the first intermediate layer is provided between the thermoelectric conversion layer and the first electrode,
the first intermediate layer is in contact with the thermoelectric conversion layer,
the first electrode is in contact with the first intermediate layer,
the second intermediate layer is provided between the thermoelectric conversion layer and the second electrode,
the second intermediate layer is in contact with the thermoelectric conversion layer,
the second electrode is in contact with the second intermediate layer,
the first electrode and the second electrode contain at least Cu,
the thermoelectric conversion layer is composed of a thermoelectric conversion material containing Mg,
the thermoelectric conversion material contains at least one kind of element selected from the group consisting of Sb and Bi,
the thermoelectric conversion material contains at least one kind of element selected from the group consisting of Se and Te,
the thermoelectric conversion material has a La 2 O 3 -type crystalline structure,
the first intermediate layer and the second intermediate layer contain Cu, Mg, and at least one element selected from the group consisting of Sb and Bi,
the thermoelectric conversion layer, the first intermediate layer and the first electrode are continuous,
the thermoelectric conversion layer, the second intermediate layer and the second electrode are continuous,
the Mg is continuously present in the thermoelectric conversion layer and the first intermediate layer,
the Mg is continuously present in the thermoelectric conversion layer and the second intermediate layer,
a content of Cu in the first intermediate layer is not less than 50 weight percent,
a content of Cu in the second intermediate layer is not less than 50 weight percent,
a content of Mg in the first intermediate layer is smaller than the content of Cu in the first intermediate layer, and
a content of Mg in the second intermediate layer is smaller than the content of Cu in the second intermediate layer.
2. The thermoelectric conversion element according to claim 1 , wherein
the thermoelectric conversion material has a composition represented by a formula (I): Mg 3+m A a B b D 2-e E e , and is of n-type,
where:
A in the formula (I) is at least one kind of element selected from the group consisting of Ca, Sr, Ba, and Yb,
B is at least one kind of element selected from the group consisting of Mn and Zn,
D is at least one kind of element selected from the group consisting of Sb and Bi,
E is at least one kind of element selected from the group consisting of Se and Te,
the value of m in the formula (I) falls within a range of not less than −0.39 and not more than 0.42,
the value of a falls within a range of not less than 0 and not more than 0.12,
the value of b falls within a range of not less than 0 and not more than 0.48, and
the value of e falls within a range of not less than 0.001 and not more than 0.06.
3. The thermoelectric conversion element according to claim 2 , wherein the value of e in the formula (I) falls within a range of not less than 0.004 and not more than 0.020.
4. The thermoelectric conversion element according to claim 2 , wherein m, a, and b in the formula (I) satisfies a formula (II): m=m′−a−b,
where:
the value of m′ in the formula (II) falls within a range of not less than 0 and not more than 0.21, and
at least one value selected from the group consisting of the values a and b is more than 0.
5. The thermoelectric conversion element according to claim 2 , wherein
the values of a and b in the formula (I) are 0.
6. The thermoelectric conversion element according to claim 2 , wherein
D in the formula (I) is Sb and Bi; and E is Te.
7. A thermoelectric conversion module, comprising:
the thermoelectric conversion element according to claim 1 , wherein the thermoelectric conversion element is an n-type thermoelectric conversion element with an n-type thermoelectric conversion part being the thermoelectric conversion layer; and
a p-type thermoelectric conversion element, wherein:
the p-type thermoelectric conversion element comprises:
a third electrode;
a fourth electrode; and
a p-type thermoelectric conversion part,
the p-type thermoelectric conversion part is provided between the third electrode and the fourth electrode,
the third electrode and the fourth electrode are in contact with the p-type thermoelectric conversion part, and
the first electrode or the second electrode in the n-type thermoelectric conversion element and the third electrode or the fourth electrode in the p-type thermoelectric conversion element are electrically connected to each other by one of the first external electrode or the second external electrode.
8. The thermoelectric conversion element according to claim 1 , wherein
the content of Mg in the first intermediate layer is not less than 0.1 weight percent, and
the content of Mg in the second intermediate layer is not less than 0.1 weight percent.
9. The thermoelectric conversion element according to claim 8 , wherein
the content of Mg in the first intermediate layer is not more than 25 weight percent, and
the content of Mg in the second intermediate layer is not more than 25 weight percent.
10. The thermoelectric conversion element according to claim 1 , wherein the first electrode and the second electrode include a CuZn alloy consisting of Cu and Zn.
11. The thermoelectric conversion element according to claim 10 , wherein
a weight ratio of Cu to Zn in the CuZn alloy is in a range of 99:1 to 57:43.
12. The thermoelectric conversion module according to claim 7 , wherein the first electrode and the third electrode are connected to each other via the first joint layer.
13. The thermoelectric conversion element according to claim 1 , wherein
at least one kind of element selected from the group consisting of Sb and Bi is present in the thermoelectric conversion layer and the first intermediate layer, and
at least one kind of element selected from the group consisting of Sb and Bi is present in the thermoelectric conversion layer and the second intermediate layer.
14. The thermoelectric conversion element according to claim 10 , wherein
the Cu and Zn are continuously present in the first intermediate layer and the first electrode, and
the Cu and Zn are continuously present in the second intermediate layer and the second electrode.