Reference thermoelectric conversion module for thermoelectric power generation tests

Abstract

To provide a reference thermoelectric conversion module for thermoelectric power generation tests having long-term reliability of which the bondability with an electrode part is excellent and which is improved in chemical and mechanical characteristics even in a case where it is used under a high temperature condition.SOLUTION: A reference thermoelectric conversion module 10 for thermoelectric power generation tests used for a thermoelectric power generation test device, which evaluates a thermoelectric power generation module, comprises: a P type thermoelectric conversion element 11P and an N type thermoelectric conversion element 11N which are alternately erected while being spaced from each other; a first electrode part 25 which is disposed in a first end in an erection direction of the P type thermoelectric conversion element 11P and the N type thermoelectric conversion element 11N; and a second electrode part 35 which is disposed in a second end in the erection direction. The P type thermoelectric conversion element 11P and the N type thermoelectric conversion element 11N are electrically connected via the first electrode part 25 and the second electrode part 35, and the P type thermoelectric conversion element 11P and the N type thermoelectric conversion element 11N consist of an alloy containing Ni and Si as main components.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a reference thermoelectric conversion module for thermoelectric power generation testing used in a thermoelectric power generation testing device for evaluating thermoelectric power generation modules. [Background technology]

[0002] A thermoelectric conversion element is an electronic element capable of converting thermal energy into electrical energy and vice versa by the Seebeck effect or the Peltier effect. The Seebeck effect is a phenomenon in which an electromotive force is generated when a temperature difference is created across a thermoelectric conversion element, and converts thermal energy into electrical energy. The electromotive force generated by the Seebeck effect is determined by the characteristics of the thermoelectric conversion element. In recent years, there has been active development of thermoelectric power generation that utilizes this effect. The Peltier effect is a phenomenon in which a temperature difference occurs across a thermoelectric conversion element when electrodes are formed on both ends of the element and a potential difference is generated between the electrodes, converting electrical energy into thermal energy. Elements with this effect are called Peltier elements, and are used for cooling and temperature control in precision instruments and small refrigerators. As a thermoelectric conversion module using the above-mentioned thermoelectric conversion elements, for example, one having a structure in which P-type thermoelectric conversion elements and N-type thermoelectric conversion elements are alternately connected in series has been proposed.

[0003] When evaluating the thermoelectric properties of the above-mentioned thermoelectric conversion modules, a thermoelectric power generation test device is used. However, since the evaluation methods for thermoelectric conversion modules are not internationally standardized, the difficulty of comparative evaluation is considered a problem, and the development of a standard reference thermoelectric conversion module is desired. Therefore, a standard reference thermoelectric conversion module is required for this thermoelectric power generation test device. Conventionally, the use of existing thermoelectric materials with high material performance (ZT value) (e.g., Bi-Te, Mg-Si, Si-Ge, etc.) has been considered as standard reference thermoelectric conversion modules.

[0004] However, the Bi-Te thermoelectric conversion element has problems in that it is a brittle material and has poor mechanical strength, and the output power becomes unstable at high temperatures of 300° C. or higher, making it difficult to use. Furthermore, Mg-Si thermoelectric conversion elements have issues with the durability of the elements themselves due to the effects of oxidation, and there are issues with stable power output over long periods of time, making them difficult to use as reference thermoelectric conversion elements. Furthermore, although Si-Ge thermoelectric conversion elements can be used at 500°C, there is a large difference in the thermal expansion coefficient between them and the metal electrodes, which raises concerns about the possibility of the joint between the thermoelectric conversion element and the metal electrodes peeling off or the element itself being damaged, posing a problem with its durability as a thermoelectric power generation module.

[0005] Therefore, for example, Patent Documents 1 and 2 propose a reference thermoelectric conversion module for thermoelectric power generation tests that uses a Cu-Ni alloy (constantan) whose main component is copper, and a Ni-Cr alloy (chromel) whose main component is Ni, which are thermocouple materials that are chemically stable and have excellent mechanical properties. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-078351 [Patent Document 2] Patent No. 6858379 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the reference thermoelectric conversion module for thermoelectric power generation testing using Cu-Ni alloy (constantan) and Ni-Cr alloy (chromel) shown in Patent Documents 1 and 2, there was a large difference in thermal expansion coefficient between the Cu-Ni alloy (constantan) and the Ni-Cr alloy (chromel), and there was a risk of cracks occurring between the electrode parts. In particular, when the temperature of the high-temperature part reached a high temperature condition of 500°C or higher, there was a risk of it not being possible to use it stably.

[0008] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a reference thermoelectric conversion module for thermoelectric power generation testing, which has good bonding with the electrode parts even when used under high temperature conditions, excellent chemical and mechanical properties, and stable thermoelectric power generation characteristics and long-term reliability. [Means for solving the problem]

[0009] In order to solve the above problems, a reference thermoelectric conversion module for thermoelectric power generation tests of a first aspect of the present invention is a reference thermoelectric conversion module for thermoelectric power generation tests used in a thermoelectric power generation test device for evaluating thermoelectric power generation modules, and is characterized in that it has P-type thermoelectric conversion elements and N-type thermoelectric conversion elements arranged alternately and at a distance from each other, a first electrode portion arranged at a first end in the standing direction of the P-type thermoelectric conversion elements and the N-type thermoelectric conversion elements, and a second electrode portion arranged at a second end in the standing direction, wherein the P-type thermoelectric conversion elements and the N-type thermoelectric conversion elements are electrically connected via the first electrode portion and the second electrode portion, and the P-type thermoelectric conversion elements and the N-type thermoelectric conversion elements are made of an alloy mainly composed of Ni and Si.

[0010] According to the reference thermoelectric conversion module for thermoelectric power generation tests of the first aspect of the present invention, the P-type thermoelectric conversion elements and the N-type thermoelectric conversion elements arranged alternately are made of alloys mainly composed of Ni and Si, respectively, and therefore have excellent chemical and mechanical properties, and these properties are stable even when used under high temperature conditions. Furthermore, the difference in thermal expansion coefficient between the P-type thermoelectric conversion element and the N-type thermoelectric conversion element becomes small, and even when the thermoelectric conversion module is used under high temperature conditions where the temperature on the high-temperature side is, for example, 500°C or higher, the bonding with the electrode portion becomes good, and a stable power generation output of the reference thermoelectric conversion module can be obtained.

[0011] A reference thermoelectric conversion module for thermoelectric power generation test according to a second aspect of the present invention is the reference thermoelectric conversion module for thermoelectric power generation test according to the first aspect of the present invention, wherein the difference in thermal expansion coefficient between the P-type thermoelectric conversion element and the N-type thermoelectric conversion element at 50° C. to 500° C. is 2×10 -6 K -1 It is characterized by being less than

[0012] According to the reference thermoelectric conversion module for thermoelectric power generation test of the second aspect of the present invention, the difference in thermal expansion coefficient between the P-type thermoelectric conversion elements and the N-type thermoelectric conversion elements arranged alternately at 50° C. to 500° C. is 2×10 -6 K -1 Even when the high-temperature side of the thermoelectric conversion module is used under high-temperature conditions, for example, at 500°C or higher, the bonding with the electrode part is good and a stable power generation output of the reference thermoelectric conversion module can be obtained.

[0013] A reference thermoelectric conversion module for thermoelectric power generation tests of a third aspect of the present invention is characterized in that, in the reference thermoelectric conversion module for thermoelectric power generation tests of the first or second aspect of the present invention, the P-type thermoelectric conversion element is made of a Ni-Si-Cr alloy, and the N-type thermoelectric conversion element is made of a Ni-Si alloy.

[0014] According to the reference thermoelectric conversion module for thermoelectric power generation test of the third aspect of the present invention, the P-type thermoelectric conversion element is made of a Ni-Si-Cr alloy, and the N-type thermoelectric conversion element is made of a Ni-Si alloy, so that the chemical and mechanical properties are excellent and the properties are stable even when used under high temperature conditions. In particular, the Ni-Si-Cr alloy element and the Ni-Si alloy element are characterized in that they can provide stable thermoelectric power generation output even when used under very high temperature conditions of about 500°C. In addition, the difference in thermal expansion coefficient between the P-type thermoelectric conversion element and the N-type thermoelectric conversion element is small, resulting in good bonding with the electrodes even when used under high-temperature conditions, enabling the module to obtain stable power generation output as a reference thermoelectric conversion module.

[0015] A reference thermoelectric conversion module for thermoelectric power generation tests of a fourth aspect of the present invention is characterized in that, in a reference thermoelectric conversion module for thermoelectric power generation tests of any one of the first to third aspects of the present invention, an Ag contact layer is formed on the first end and the second end of the P-type thermoelectric conversion element and the N-type thermoelectric conversion element.

[0016] According to the reference thermoelectric conversion module for thermoelectric power generation test of the fourth aspect of the present invention, since an Ag contact layer is formed on the first end and the second end of the P-type thermoelectric conversion element and the N-type thermoelectric conversion element, the bonding with the first electrode part and the second electrode part is excellent. In addition, since it is made of Ag, it has little effect on the properties of an alloy mainly composed of Ni and Si, and even when used under high temperature conditions of, for example, 500°C or higher, it is possible to suppress the properties of the P-type thermoelectric conversion element and the N-type thermoelectric conversion element from changing. As a result, even when used under high temperature conditions where the temperature of the high temperature side of the thermoelectric conversion module is, for example, 500°C or higher, a stable power generation output of the reference thermoelectric conversion module can be obtained.

[0017] A reference thermoelectric conversion module for thermoelectric power generation tests of a fifth aspect of the present invention is characterized in that, in the reference thermoelectric conversion module for thermoelectric power generation tests of the fourth aspect of the present invention, an Ag layer is formed on the joint surfaces of the first electrode portion and the second electrode portion.

[0018] According to the reference thermoelectric conversion module for thermoelectric power generation test of the fifth aspect of the present invention, an Ag layer is formed on the joint surfaces of the first electrode portion and the second electrode portion, which improves the joint between the Ag contact layers formed on the first ends and the second ends of the P-type thermoelectric conversion elements and the N-type thermoelectric conversion elements, and provides particularly excellent joint reliability between the first electrode portion and the second electrode portion and the P-type thermoelectric conversion elements and the N-type thermoelectric conversion elements. As a result, even when the thermoelectric conversion module is used under high-temperature conditions where the temperature on the high-temperature side is, for example, 500° C. or higher, a stable power generation output of the reference thermoelectric conversion module can be obtained.

[0019] A reference thermoelectric conversion module for thermoelectric power generation testing of a sixth aspect of the present invention is characterized in that, in the reference thermoelectric conversion module for thermoelectric power generation testing of any one of the first to fifth aspects of the present invention, a first insulating substrate having a first ceramic substrate and the first electrode portion formed on one surface of the first ceramic substrate is arranged at the first ends of the P-type thermoelectric conversion element and the N-type thermoelectric conversion element, and a second insulating substrate having a second ceramic substrate, an aluminum layer stacked on one surface of the second ceramic substrate, and the second electrode portion formed on one surface of the aluminum layer is arranged at the second ends of the P-type thermoelectric conversion element and the N-type thermoelectric conversion element.

[0020] According to the sixth aspect of the reference thermoelectric conversion module for thermoelectric power generation test of the present invention, a second insulating substrate is arranged at the second ends of the P-type thermoelectric conversion element and the N-type thermoelectric conversion element, the second insulating substrate including a second ceramic substrate, an aluminum layer laminated on one surface of the second ceramic substrate, and the first electrode portion formed on one surface of the aluminum layer, so that the aluminum layer has excellent stress relaxation properties and can relieve stress due to thermal expansion differences. Furthermore, by placing this second insulating substrate on the low temperature side and placing a first insulating substrate having a first ceramic substrate and the first electrode portion formed on one surface of the first ceramic substrate on the high temperature side, diffusion of aluminum into the P-type thermoelectric conversion element and the N-type thermoelectric conversion element can be suppressed, and the characteristics of the P-type thermoelectric conversion element and the N-type thermoelectric conversion element can be stabilized.

[0021] A reference thermoelectric conversion module for thermoelectric power generation tests of a seventh aspect of the present invention is characterized in that, in a reference thermoelectric conversion module for thermoelectric power generation tests of any one of the first to sixth aspects of the present invention, a through hole is formed on the side of the P-type thermoelectric conversion element and the N-type thermoelectric conversion element.

[0022] According to the seventh aspect of the reference thermoelectric conversion module for thermoelectric power generation tests of the present invention, through holes are formed on the side surfaces of the P-type thermoelectric conversion element and the N-type thermoelectric conversion element, thereby reducing the thermal conductivity in the vertical direction of the P-type thermoelectric conversion element and the N-type thermoelectric conversion element and ensuring a temperature difference between the high-temperature side and the low-temperature side of the reference thermoelectric conversion module, thereby improving the thermoelectric power generation characteristics and enabling stable thermoelectric power generation output. Effect of the Invention

[0023] According to the present invention, it is possible to provide a reference thermoelectric conversion module for thermoelectric power generation testing that has good bonding with the electrode parts even when used under high temperature conditions, has excellent chemical and mechanical properties, and has stable thermoelectric power generation characteristics and long-term reliability. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a schematic explanatory diagram of a reference thermoelectric conversion module for thermoelectric power generation test according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic explanatory diagram of a P-type thermoelectric conversion element and an N-type thermoelectric conversion element in a reference thermoelectric conversion module for thermoelectric power generation test according to an embodiment of the present invention. [Diagram 3] FIG. 3 is a flow diagram showing a method for manufacturing a P-type thermoelectric conversion element and an N-type thermoelectric conversion element in the present embodiment. [Figure 4] FIG. 2 is a flow diagram showing a method for producing a reference thermoelectric conversion module for thermoelectric power generation test according to an embodiment of the present invention. [Diagram 5] 1 is a graph showing the results of a thermal cycle test of a reference thermoelectric conversion module for a thermoelectric power generation test of an example of the present invention in an embodiment, in which (a) shows the thermoelectromotive force, (b) shows the internal resistance value, and (c) shows the power generation output, and values ​​normalized by the initial value are displayed. [Figure 6] 1 is a graph showing the results of a thermal cycle test of a reference thermoelectric conversion module for a thermoelectric power generation test of a comparative example in an embodiment, where (a) shows the thermoelectromotive force, (b) shows the internal resistance, and (c) shows the power generation output, and values ​​normalized by the initial value are shown. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, embodiments of the present invention will be described with reference to the attached drawings. Note that the following embodiments are specifically described to better understand the gist of the invention, and do not limit the present invention unless otherwise specified. In addition, the drawings used in the following description may show essential parts in an enlarged scale for the sake of convenience in order to make the features of the present invention easier to understand, and the dimensional ratios of each component may not necessarily be the same as the actual ones.

[0026] As shown in FIG. 1, the reference thermoelectric conversion module 10 for thermoelectric power generation testing according to this embodiment includes P-type thermoelectric conversion elements 11P and N-type thermoelectric conversion elements 11N arranged alternately and with a gap between them, a first insulating substrate 20 arranged at a first end (upper end in FIG. 1) in the vertical direction of the P-type thermoelectric conversion elements 11P and N-type thermoelectric conversion elements 11N, and a second insulating substrate 30 arranged at a second end (lower end in FIG. 1) in the vertical direction of the P-type thermoelectric conversion elements 11P and N-type thermoelectric conversion elements 11N.

[0027] Here, as shown in FIG. 1, a first electrode portion 25 is formed on a first insulating substrate 20 arranged at a first end of the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N, and a second electrode portion 35 is formed on a second insulating substrate 30 arranged at a second end of the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N, and the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N are electrically connected in series by these first electrode portion 25 and second electrode portion 35.

[0028] In this embodiment, the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N are each made of an alloy mainly composed of Ni and Si. In this embodiment, the alloy mainly composed of Ni and Si is an alloy containing Ni and Si at a total of 80 at% or more. As elements other than Ni and Si, for example, Cr, Fe, Mg, etc. may be contained as additive elements. In addition, other elements may be contained as impurities. In this embodiment, it is preferable that the P-type thermoelectric conversion elements 11P are made of a Ni-Si-Cr alloy (Nicrosil), and the N-type thermoelectric conversion elements 11N are made of a Ni-Si alloy (Nisil).

[0029] In this embodiment, the difference in thermal expansion coefficient between the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N at 50° C. to 500° C. is 2×10 -6 K -1 It is preferable that it is less than 1000 .mu.m. The difference in thermal expansion coefficient between the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N at 50° C. to 500° C. is 1.5×10 -6 K -1 More preferably, it is less than 1.0×10 -6 K -1 It is even more preferable that it is less than 1000 .mu.m.

[0030] In this embodiment, it is preferable that through holes 15 are formed on the side surfaces of the P-type thermoelectric conversion elements 11P and the N-type thermoelectric conversion elements 11N. The P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N, which are made of an alloy mainly composed of Ni and Si, have a higher thermal conductivity than other thermoelectric materials. Therefore, by forming the through-holes 15 on the side surfaces of the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N, the thermal conductivity in the vertical direction of the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N is reduced. Specifically, the thermal conductivity is reduced to about 1 / 3, and the electrical resistance is reduced to about 2.7 times. Although there is no particular limitation on the shape and number of the through holes 15, in this embodiment, a plurality of through holes 15 are formed so as to intersect with each other as shown in FIG.

[0031] In this embodiment, it is preferable that an Ag contact layer 18 is formed on each of the first and second ends in the erecting direction of the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N. Here, the lower limit of the thickness of the Ag contact layer 18 is preferably 0.05 μm or more, and more preferably 0.1 μm or more. The upper limit of the thickness of the Ag contact layer 18 is preferably less than 1000 μm, and more preferably less than 500 μm.

[0032] The first insulating substrate 20 arranged on the first end side of the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N includes a first ceramic substrate 21 and a first electrode portion 25 formed on one surface (the upper surface in Figure 1) of the first ceramic substrate 21. Here, the first ceramic substrate 21 of the first insulating substrate 20 is made of ceramics. The ceramics constituting the first ceramic substrate 21 may be, for example, aluminum oxide, aluminum nitride, silicon nitride, or the like. The thickness of the first ceramic substrate 21 is preferably within a range of 100 μm to 2000 μm.

[0033] An Ag layer is formed on the bonding surface between the first electrode portion 25 and the first ends of the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N. In this embodiment, the first electrode portion 25 is made of a fired Ag body, and the entire first electrode portion 25 is made of the Ag layer. The first electrode portion 25 is formed in a pattern on one surface (the lower surface in FIG. 1) of the first ceramic substrate 21.

[0034] The second insulating substrate 30 arranged on the second end side of the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N includes a second ceramic substrate 31, an aluminum layer 34 formed on one surface (the upper surface in FIG. 1) of the second ceramic substrate 31, and a second electrode portion 35 formed on one surface of the aluminum layer 34. In this embodiment, as shown in FIG. 1, the second insulating substrate 30 has a heat dissipation layer 37 formed on the other surface (the upper surface in FIG. 1) of the second ceramic substrate 31.

[0035] The second ceramic substrate 31 is made of, for example, aluminum nitride (AlN) or silicon nitride (Si 3 N 4 ), Alumina (Al 2 O 3 The second ceramic substrate 31 is made of a highly insulating ceramic material such as aluminum nitride (AlN), or an insulating resin. In this embodiment, the second ceramic substrate 31 is made of aluminum nitride (AlN). The thickness of the second ceramic substrate 31 made of aluminum nitride is set to be within a range of 100 μm to 2000 μm.

[0036] In this embodiment, the aluminum layer 34 is made of aluminum with a purity of 99 mass % or more, or aluminum with a purity of 99.99 mass % or more. In this embodiment, the thickness of the aluminum layer 34 is preferably within the range of 50 μm to 2000 μm.

[0037] An Ag layer is formed on the bonding surface between the second electrode portion 35 and the second ends of the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N. In this embodiment, the second electrode portion 35 is made of a fired Ag body, and the entire second electrode portion 35 is made of the Ag layer. As shown in FIG. 1, the aluminum layer 34 and the second electrode portion 35 are formed in a pattern on one surface (the upper surface in FIG. 1) of the second ceramic substrate 31.

[0038] The heat dissipation layer 37 is made of aluminum. In this embodiment, like the aluminum layer 34, the heat dissipation layer 37 is made of aluminum with a purity of 99 mass % or more or aluminum with a purity of 99.99 mass % or more.

[0039] Here, in the reference thermoelectric conversion module 10 for thermoelectric power generation testing of this embodiment, the first insulating substrate 20 is disposed on the high temperature side, and the second insulating substrate 30 is disposed on the low temperature side for use. The high temperature side can be used as long as it is higher than the low temperature side, and can be used even at 400°C or higher. The low temperature side is within the range of 30°C or higher and 100°C or lower. The high temperature side may be 500°C or higher.

[0040] Next, a method for manufacturing the above-mentioned P-type thermoelectric conversion elements 11P and N-type thermoelectric conversion elements 11N will be described with reference to FIG.

[0041] (Raw material powder preparation process S01) First, raw material powder is prepared according to the composition of the alloy containing Ni and Si as main components that constitutes the P-type thermoelectric conversion elements 11P and the N-type thermoelectric conversion elements 11N. In this embodiment, since the P-type thermoelectric conversion element 11P is made of a Ni-Si-Cr alloy, Ni powder, Cr powder, and Si powder are prepared when manufacturing the P-type thermoelectric conversion element 11P. On the other hand, since the N-type thermoelectric conversion element 11N is made of a Ni-Si alloy, Ni powder and Si powder are prepared when manufacturing the N-type thermoelectric conversion element 11N. Here, the Ni powder preferably has a purity of 99.9 mass % or more and an average particle size in the range of 1 μm to 10 μm. The Si powder preferably has a purity of 99.9 mass % or more and an average particle size of 1 μm or more and 5 μm or less. The Cr powder preferably has a purity of 98 mass% or more and an average particle size of 1 μm or more and 50 μm or less.

[0042] (Raw material powder mixing process S02) The above-mentioned various metal powders are weighed and mixed to obtain a predetermined composition, to obtain a raw material powder for sintering. Here, the mixing method is not particularly limited, but it is preferable to use a ball mill device. In this case, it is preferable to use ball media made of cemented carbide such as WC in an inert gas atmosphere.

[0043] (Sintering raw material powder filling process S03) Next, the above-mentioned sintering raw material powder is filled into the mold. At this time, Ag foil is disposed on both ends of the filled sintering raw material powder. The thickness of the Ag foil is preferably within the range of 1 μm to 1000 μm.

[0044] (Sintering process S04) Next, the sintering raw material powder and Ag foil filled in the mold are heated while being pressurized to obtain a sintered body. At this time, Ag contact layers 18 are formed on both ends of the sintered body. In this embodiment, the sintering conditions in the sintering step S04 are preferably a sintering temperature in the range of 550° C. to 650° C., a holding time at this sintering temperature in the range of 5 minutes to 100 minutes, a pressurizing load in the range of 5 MPa to 100 MPa, and an inert gas atmosphere or a vacuum atmosphere.

[0045] (Through hole formation step S05) Next, if necessary, through holes 15 are formed in the side surface of the sintered body. There are no particular limitations on the processing method, and mechanical processing, laser processing, etc. may be appropriately selected and applied.

[0046] Through the steps described above, the P-type thermoelectric conversion elements 11P and the N-type thermoelectric conversion elements 11N of this embodiment are manufactured.

[0047] Next, a method for manufacturing the reference thermoelectric conversion module 10 for thermoelectric power generation test according to the present embodiment will be described with reference to FIG.

[0048] (First insulating substrate and second insulating substrate preparation step S11) First, a first insulating substrate 20 is prepared, which is disposed at a first end in the vertical direction of the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N, which are arranged at a distance from each other, and a second insulating substrate 30 is prepared, which is disposed at a second end in the vertical direction of the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N.

[0049] (Installation process S12) Next, a first insulating substrate 20 is disposed on first ends of the P-type thermoelectric conversion elements 11P and the N-type thermoelectric conversion elements 11N, and a second insulating substrate 30 is disposed on second ends of the P-type thermoelectric conversion elements 11P and the N-type thermoelectric conversion elements 11N.

[0050] (First electrode portion bonding process S13 and second electrode portion bonding process S14) Next, the first insulating substrate 20, the P-type thermoelectric conversion elements 11P and the N-type thermoelectric conversion elements 11N, and the second insulating substrate 30 are pressed in the stacking direction and heated to bond the P-type thermoelectric conversion elements 11P and the N-type thermoelectric conversion elements 11N to the first electrode portions 25, and the P-type thermoelectric conversion elements 11P and the N-type thermoelectric conversion elements 11N to the second electrode portions 35. That is, in this embodiment, the first ends of the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N are joined to the first electrode portion 25 of the first insulating substrate 20, and the second ends of the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N are joined to the second electrode portion 35 of the second insulating substrate 30 simultaneously.

[0051] Here, in this embodiment, the first electrode portion 25 and the second electrode portion 35 are made of Ag, and Ag contact layers 18 are formed on the first and second ends of the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N, respectively, so that the junction between the first ends of the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N and the first electrode portion 25 of the first insulating substrate 20, and the junction between the second ends of the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N and the second electrode portion 35 of the second insulating substrate 30 are diffusion junctions between Ag.

[0052] In the first electrode portion joining process S13 and the second electrode portion joining process S14, it is preferable that the pressure load is in the range of 5 MPa or more and 30 MPa or less, the heating temperature is in the range of 300°C or more and 450°C or less, the holding time at the above-mentioned heating temperature is in the range of 30 minutes or more and 300 minutes or less, and the atmosphere is an inert gas atmosphere or a vacuum atmosphere.

[0053] In this manner, the reference thermoelectric conversion module 10 for thermoelectric power generation test according to this embodiment is manufactured.

[0054] According to the reference thermoelectric conversion module 10 for thermoelectric power generation tests, which is this embodiment configured as described above, the P-type thermoelectric conversion elements 11P and the N-type thermoelectric conversion elements 11N arranged alternately are made of alloys mainly composed of Ni and Si, respectively, and therefore have excellent chemical and mechanical properties. In addition, these thermoelectric power generation characteristics are stable even when used under high-temperature conditions where the temperature on the high-temperature side of the reference thermoelectric conversion module is, for example, 500°C or higher. Furthermore, since the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N are made of an alloy mainly composed of Ni and Si, the difference in their thermal expansion coefficients is small, and even when used under high temperature conditions, the bonding with the first electrode portion 25 and the second electrode portion 35 is good, a stable power generation output of the reference thermoelectric conversion module can be obtained, and it can be used stably for a long time.

[0055] In this embodiment, the difference in thermal expansion coefficient between the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N at 50° C. to 500° C. is 2×10 -6 K -1 When the temperature is less than this, even when used under high temperature conditions, there is little difference in the amount of deformation due to thermal expansion between the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N, the bonding between the first electrode portion 25 and the second electrode portion 35 is even better, a stable power generation output of the reference thermoelectric conversion module can be obtained, and it can be used stably for a long period of time.

[0056] In this embodiment, when the P-type thermoelectric conversion element 11P is made of a Ni-Si-Cr alloy and the N-type thermoelectric conversion element 11N is made of a Ni-Si alloy, the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N have sufficiently excellent chemical and mechanical properties, and these properties are stable even when used under high temperature conditions. Furthermore, the difference in thermal expansion coefficient between the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N is reliably reduced, and even when used under high temperature conditions, the bonding between the first electrode portion 25 and the second electrode portion 35 is even better, resulting in a stable power generation output of the reference thermoelectric conversion module, which can be used stably for a long period of time.

[0057] In this embodiment, when an Ag contact layer 18 is formed on the first end and the second end of the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N, respectively, the bonding strength with the first electrode portion 25 and the second electrode portion 35 is excellent. In addition, since the Ag contact layer 18 is made of Ag, it has little effect on the properties of an alloy primarily composed of Ni and Si, and even when used under high temperature conditions, the effect on the properties of the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N can be suppressed.

[0058] In this embodiment, when an Ag layer is formed on the bonding surfaces of the first electrode portion 25 and the second electrode portion 35, the bonding with the Ag contact layer 18 formed on the first and second ends of the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N becomes even better, and the bonding reliability between the first electrode portion 25 and the second electrode portion 35 and the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N is particularly excellent.

[0059] In this embodiment, a second insulating substrate 30 including a second ceramic substrate 31, an aluminum layer 34, and a second electrode portion 35 is disposed at the second ends of the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N, so that the aluminum layer 34, which has excellent stress relaxation properties, can relieve stress caused by differences in thermal expansion. Furthermore, by placing this second insulating substrate 30 on the low temperature side and placing the first insulating substrate 20 having the first ceramic substrate 21 and the first electrode portion 25 on the high temperature side, the diffusion of aluminum into the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N can be suppressed, and the impact on the characteristics of the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N can be reliably suppressed, resulting in stable characteristics.

[0060] In this embodiment, since through holes 15 are formed on the side surfaces of the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N, the thermal conductivity in the vertical direction of the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N is reduced, a temperature difference between the high-temperature side and the low-temperature side can be secured, and the thermoelectric power generation characteristics become further stabilized.

[0061] Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and can be modified as appropriate without departing from the technical concept of the invention. For example, in the present embodiment, as shown in Fig. 2, a plurality of through holes 15 are formed on the side surfaces of the P-type thermoelectric conversion element 11P and the N-type thermoelectric conversion element 11N so as to intersect with each other, but this is not limited thereto, and the through holes do not necessarily have to be formed. Also, only one through hole 15 may be formed, or a plurality of through holes 15 may be formed. EXAMPLES

[0062] The results of experiments carried out to confirm the effects of the present invention will be described below.

[0063] (Example of the present invention) The P-type thermoelectric conversion element was made of a Ni-Si-Cr alloy (Nicrosil), and the N-type thermoelectric conversion element was made of a Ni-Si alloy (Nisil), and an Ag contact layer (thickness 500 μm) was formed on the first end and second end of the P-type thermoelectric conversion element and the N-type thermoelectric conversion element. In this embodiment, the composition ratio of the Ni-Si-Cr alloy exhibiting P-type thermoelectric properties is 81.3:15.7:2.6 (Ni 81.3 Cr 15.7 S 2.6 ), and the composition ratio of Ni-Si alloy showing N-type thermoelectric properties is 90.5:9.5 (Ni 90.5 S 9.5 ) was decided.

[0064] Ni powder (manufactured by High Purity Chemical Laboratory, purity 99.9 mass% or more, average particle size 3 to 5 μm), Cr powder (manufactured by High Purity Chemical Laboratory, purity 98 mass% or more, average particle size 10 μm), and Si powder (manufactured by High Purity Chemical Laboratory, purity 99.9 mass%, average particle size 5 μm) were prepared. These raw powders were weighed and mixed and ground in a ball mill. The conditions for the ball mill (Fritsch Planetary Ball Mill PL-7) were as follows: for Ni-Si-Cr alloy (Nicrosil), the pot and balls of the ball mill were made of WC, the atmosphere was argon, the rotation speed was 250 rpm, and 20 cycles were performed with 40 minutes of grinding time and 20 minutes of interval time as one cycle. For Ni-Si alloy (Nisil), the pot and balls of the ball mill were made of WC, the atmosphere was argon, the rotation speed was 250 rpm, and 6 cycles were performed with 40 minutes of grinding time and 20 minutes of interval time as one cycle. In this way, raw powder for sintering was obtained.

[0065] The raw material powder for sintering was packed into a graphite mold having a diameter of 15 mm, and Ag foil (manufactured by Furuuchi Chemical Co., Ltd., purity 99.99 mass% or more, thickness 0.5 mm) was placed on both ends of the packed raw material powder for sintering. Then, in a sintering machine (Fuji Electric Machinery Co., Ltd. SPS-622A), the temperature was increased from room temperature to 600°C in 5 minutes, and from 600°C to 850°C in 20 minutes, and the temperature was held at 850°C for 1 hour, with a sintering pressure of 30 MPa. In this way, a P-type thermoelectric conversion element and an N-type thermoelectric conversion element having Ag contact layers at the first and second ends were manufactured.

[0066] In addition, through holes were formed on the side surfaces of the P-type and N-type thermoelectric conversion elements as shown in Figure 2. By forming the through holes, the amount of heat flowing through the elements in the vertical direction of the P-type and N-type thermoelectric conversion elements was reduced to about 1 / 4, and the electrical resistance increased by about 3.5 times.

[0067] As described in the embodiment, a first ceramic substrate having a first electrode portion made of sintered Ag formed thereon was prepared as a first insulating substrate disposed on the first end side. Furthermore, as the second insulating substrate disposed on the second end side, a second ceramic substrate having a second electrode portion formed thereon, made of an aluminum layer and a sintered Ag body, was prepared as described in the embodiment. The bonding conditions for the P-type and N-type thermoelectric conversion elements to the first and second insulating substrates were a vacuum atmosphere (1 Pa or less), a load of 20 MPa, a heating temperature of 380° C., and a holding time at the heating temperature of 90 minutes.

[0068] (Comparative Example) The P-type thermoelectric conversion element was made of a Ni-Cr alloy (chromel), and the N-type thermoelectric conversion element was made of a Cu-Ni alloy (constantan), and an Ag contact layer (thickness 500 μm) was formed on the first and second ends of the P-type thermoelectric conversion element and the N-type thermoelectric conversion element. In addition, through holes were formed on the side surfaces of the P-type thermoelectric conversion element and the N-type thermoelectric conversion element as shown in Figure 2. By forming the through holes, the amount of heat flowing into the element was reduced to about one-third, as in the example, and the electrical resistance value increased by about four times.

[0069] As described in the embodiment, a first ceramic substrate having a first electrode portion made of sintered Ag formed thereon was prepared as a first insulating substrate disposed on the first end side. Furthermore, as the second insulating substrate disposed on the second end side, a second ceramic substrate having a second electrode portion formed thereon, made of an aluminum layer and a sintered Ag body, was prepared as described in the embodiment. The bonding conditions for the P-type and N-type thermoelectric conversion elements to the first and second insulating substrates were a vacuum atmosphere (1 Pa or less), a load of 15 MPa, a heating temperature of 380° C., and a holding time at the heating temperature of 90 minutes.

[0070] The obtained reference thermoelectric conversion modules for thermoelectric power generation tests of the present invention and comparative examples were cooled on the low-temperature side with 20°C cooling water, and a thermal cycle (100 times) from 500°C to 150°C was applied on the high-temperature side using a power generation efficiency characteristic evaluation device (PEM-2 manufactured by Advance Riko Co., Ltd.). The temperature profile was a heating rate of 40.0°C / min, and the holding time at the maximum temperature was about 20 minutes. The cooling was performed by stopping the heating of the high-temperature side, and holding the low-temperature side until it was cooled to 150°C by cooling. The cooling time was about 30 minutes, and the holding time after cooling to 150°C was about 5 minutes. The test was performed in a vacuum atmosphere. The number of thermal cycles and the changes in electromotive force, internal resistance, and power output at that time were evaluated. The evaluation results are shown in Figures 5 and 6. The test results for electromotive force, internal resistance, and power output are shown as normalized values ​​for the initial characteristics.

[0071] In the comparative example, as shown in FIG. 5, as the number of thermal cycles increased, the electromotive force increased, the internal resistance decreased, and the output increased, and the characteristics were unstable. In addition, cracks were found between the P-type and N-type thermoelectric conversion elements and the electrodes. This was because the difference in thermal expansion coefficient between the P-type and N-type thermoelectric conversion elements was 2×10 -6 K -1 It comes from being bigger.

[0072] In contrast, in the example of the present invention, even when the thermal cycle was applied 100 times, there was almost no change in the electromotive force, internal resistance, and output, and the characteristics were stable, as shown in Fig. 6. Specifically, the rate of change in the electromotive force, internal resistance, and power output before and after the 100-cycle test was within 1%, confirming that a stable power output was obtained from the reference thermoelectric conversion module. Furthermore, no cracks were generated between the P-type and N-type thermoelectric conversion elements and the electrodes, and the joint reliability was excellent.

[0073] From the above, it was confirmed that the present invention can provide a reference thermoelectric conversion module for thermoelectric power generation testing that has good bonding with the electrode parts even when used under high temperature conditions, has excellent chemical and mechanical properties, and has stable thermoelectric power generation characteristics and long-term reliability. [Explanation of symbols]

[0074] 10 Reference thermoelectric conversion module for thermoelectric power generation testing 11P P-type thermoelectric conversion element 11N N-type thermoelectric conversion element 15 Through hole 18 Ag contact layer 20 First insulating substrate 21 First ceramic substrate 25 1st electrode part 30 Second insulating substrate 31 Second ceramic substrate 34 Aluminum layer 35 Second electrode part

Claims

1. A reference thermoelectric conversion module for thermoelectric power generation testing used in a thermoelectric power generation testing device for evaluating a thermoelectric power generation module, a first electrode portion disposed at a first end in the standing direction of the P-type thermoelectric conversion elements and the N-type thermoelectric conversion elements; and a second electrode portion disposed at a second end in the standing direction, the P-type thermoelectric conversion elements and the N-type thermoelectric conversion elements being electrically connected to each other via the first electrode portion and the second electrode portion; A reference thermoelectric conversion module for thermoelectric power generation testing, characterized in that the P-type thermoelectric conversion element and the N-type thermoelectric conversion element are made of an alloy containing Ni and Si as main components.

2. The difference in thermal expansion coefficient between the P-type thermoelectric conversion element and the N-type thermoelectric conversion element at 50° C. to 500° C. is 2×10 －６ K －１ The reference thermoelectric conversion module for thermoelectric power generation test according to claim 1, characterized in that the reference thermoelectric conversion module for thermoelectric power generation test is less than 10 ...

3. A reference thermoelectric conversion module for thermoelectric power generation testing as described in claim 1 or claim 2, characterized in that the P-type thermoelectric conversion element is made of a Ni-Si-Cr alloy, and the N-type thermoelectric conversion element is made of a Ni-Si alloy.

4. 3. A reference thermoelectric conversion module for thermoelectric power generation testing as described in claim 1 or claim 2, characterized in that an Ag contact layer is formed on the first end and the second end of the P-type thermoelectric conversion element and the N-type thermoelectric conversion element.

5. 5. The reference thermoelectric conversion module for thermoelectric power generation test according to claim 4, wherein an Ag layer is formed on a joint surface between the first electrode portion and the second electrode portion.

6. a first insulating substrate including a first ceramic substrate and the first electrode portion formed on one surface of the first ceramic substrate is disposed at the first ends of the P-type thermoelectric conversion elements and the N-type thermoelectric conversion elements; 3. The reference thermoelectric conversion module for thermoelectric power generation testing as described in claim 1 or claim 2, characterized in that a second insulating substrate is arranged at the second ends of the P-type thermoelectric conversion element and the N-type thermoelectric conversion element, the second insulating substrate comprising a second ceramic substrate, an aluminum layer laminated on one surface of the second ceramic substrate, and the second electrode portion formed on one surface of the aluminum layer.

7. 3. The reference thermoelectric conversion module for thermoelectric power generation test according to claim 1, wherein a through hole is formed on a side surface of the P-type thermoelectric conversion element and the N-type thermoelectric conversion element.

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