Heat flow switching element

Abstract

To provide a heat flow switching element having a larger change in thermal conductivity and excellent thermal response.SOLUTION: Included are a temperature change body 4 including a material or element that changes temperature due to external energy and a phase transition body 5 that is provided in contact with the temperature change body and undergoes a phase transition upon a temperature change. The phase transition body has a higher thermal conductivity than any of the phases before and after a phase transition when the phase transition occurs. The thermal conductivity is measured by at least one of a thermo-reflectance method and a flash method. The temperature change body includes a first electrode 2 and a second electrode 3. The temperature change body is an electrical resistive body provided between the first and second electrodes and including a material that generates heat by a current generated in accordance with a voltage applied between the first and second electrodes.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a heat flow switching element capable of actively controlling heat conduction with a bias voltage. [Background technology]

[0002] Conventionally, as a thermal switch that changes thermal conductivity, for example, Patent Document 1 describes a thermal switch element that includes a first electrode, a second electrode, and a transition body disposed between the first electrode and the second electrode, wherein the transition body is made of a material that undergoes an electronic phase transition when energy is applied, and the thermal conductivity between the first electrode and the second electrode changes when energy is applied to the transition body. Furthermore, this cited reference 1 describes a method for applying thermal energy to the transition medium by placing a resistor, which generates heat when an electric current flows, between the transition medium and the electrode as a heating element.

[0003] Furthermore, in Reference 1, the material undergoing an electronic phase transition is given by equation A x D y O z It is stated that the material includes oxides having the composition shown in the formula (wherein A is at least one element selected from alkali metals, alkaline earth metals, Sc, Y, and rare earth elements; D is at least one transition element selected from groups IIIa, IVa, Va, VIa, VIIa, VIII, and Ib; O is oxygen; and x, y, and z are positive numbers), and many oxides are specifically listed. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 3701302 [Overview of the project] [Problems that the invention aims to solve]

[0005] The above conventional technologies still have the following challenges. In other words, while the technology described in Patent Document 1 exemplifies many oxides as transition material, these materials exhibit small changes in thermal conductivity. Therefore, there is a demand for a heat flow switching element that can obtain a larger change in thermal conductivity.

[0006] The present invention has been made in view of the aforementioned problems, and aims to provide a heat flow switching element that exhibits a larger change in thermal conductivity and superior thermal responsiveness. [Means for solving the problem]

[0007] To solve the aforementioned problems, the present invention employs the following configuration. Specifically, the heat flow switching element according to the first invention comprises a temperature changing body including a material or element whose temperature changes due to external energy, and a phase transition body provided in contact with the temperature changing body and undergoing a phase transition due to the temperature change, wherein the phase transition body has a higher thermal conductivity than either the phase before or after the phase transition when the phase transition occurs, as measured by at least one of the thermoreflectance method and the flash method.

[0008] This heat flow switching element comprises a temperature-changing body containing a material or element whose temperature changes due to external energy, and a phase transition body provided in contact with the temperature-changing body and undergoing a phase transition due to the temperature change. The phase transition body has a higher thermal conductivity than either the phase before or after the phase transition, as measured by at least one of the thermoreflectance method and the flash method. Therefore, the thermal conductivity of the phase transition body can be adjusted by changing the temperature of the temperature-changing body, and heat flow can be controlled through this element. In particular, by controlling the temperature to trigger a phase transition to a phase with a different thermal conductivity, the phase transition material will have a higher thermal conductivity than the phases before and after the phase transition, resulting in a large change in thermal conductivity. That is, by using a temperature changer as a heater or cooler for the phase transition material, and by using a phase transition material that has a peak in thermal conductivity when transitioning to a phase with a different thermal conductivity, the thermal conductivity of the phase transition material can be greatly changed to control the heat flow. The thermal conductivity mentioned above refers to the thermal conductivity measured by at least one of the thermoreflectance method and the flash method, and it is sufficient that the thermal conductivity measured by either method has a peak. For example, if the phase transition material is a thin film, it may be measured by the thermoreflectance method, or a bulk material of the same composition may be prepared and measured by the flash method. Also, if the phase transition material is a bulk material, it may be measured by the flash method. Furthermore, the thermoreflectance method may be a time-domain thermoreflectance method or a frequency-domain thermoreflectance method. The flash method may be a laser flash method or a xenon lamp flash method. The most suitable measurement method depends on the thickness of the phase transition material, but the boundary thickness is approximately 10 μm to 100 μm. Furthermore, the boundary thickness varies depending on the composition of the phase transition material. Here, "having a peak in thermal conductivity" in this application means that the thermal conductivity at the time of the phase transition is higher than the thermal conductivity at the vicinity temperature of either the phase before or after the phase transition (approximately the average of -20°C to -10°C and +10°C to +20°C relative to the phase transition temperature).

[0009] The heat flow switching element according to the second invention is, in the first invention, wherein the phase transition material is chemical formula A 2+δ The material is characterized by being M (where A is at least one of Ag and Cu, and M is at least one of S, Se, and Te). In other words, in this heat flow switching element, the phase transition material is chemical formula A 2+δ Since M is (where A is at least one of Ag or Cu, and M is at least one of S, Se, or Te), the chemical formula A2+δ M is a material that exhibits a peak in thermal conductivity when undergoing a phase transition to a phase with a different thermal conductivity, thus enabling a large change in thermal conductivity.

[0010] The heat flow switching element according to the third invention is characterized in that, in the first or second invention, it comprises a first electrode and a second electrode, and the temperature changing element is an electrical resistor provided between the first electrode and the second electrode and containing a material that generates heat due to a current generated in response to a voltage applied between the first electrode and the second electrode. In this heat flow switching element, the temperature change element is an electrical resistor containing a material that is placed between the first electrode and the second electrode and generates heat due to the current generated in response to the voltage applied between the first electrode and the second electrode. Therefore, the thermal conductivity of the phase transition material can be adjusted by the heat generated by the electrical resistor due to the current generated in response to the applied voltage. In particular, by using Joule heating caused by voltage application to make the electrical resistor function as a heater for the phase transition material, and by using a phase transition material that has a peak in thermal conductivity when transitioning to a phase with a different thermal conductivity, it is possible to significantly change the thermal conductivity of the phase transition material and control the heat flow.

[0011] The heat flow switching element according to the fourth invention is characterized in that, in the third invention, the electrical resistor is a silicon oxide film that generates Joule heat when an electric current is applied. In other words, in this heat flow switching element, the electrical resistor is a silicon oxide (silica, silicon oxide, Si-O) film that generates Joule heat when an electric current is applied. Therefore, the silicon oxide film is not an electrical insulating film that does not allow any current to flow even when a voltage is applied, but rather a high electrical resistance film that generates Joule heat due to leakage current when a voltage is applied, and can be easily formed as a high electrical resistance material.

[0012] The heat flow switching element according to the fifth invention is characterized in that, in the fourth or fifth invention, a laminated portion is formed on the first electrode in which the electrical resistor and the phase transition material are laminated, and the second electrode is formed on the laminated portion. In other words, in this heat flow switching element, a laminated portion is formed on the first electrode, in which an electrical resistor and a phase transition material are stacked, and a second electrode is formed on the laminated portion. Therefore, by applying a voltage to the laminated portion sandwiched between the first and second electrodes and allowing a current to flow, the electrical resistor is heated, and the thermal conductivity of the phase transition material stacked on the electrical resistor can be efficiently changed.

[0013] The heat flow switching element according to the sixth invention is characterized in that, in the fifth invention, the laminated portion comprises at least a plurality of the electrical resistors, and the electrical resistors and the phase transition material are alternately laminated, with the upper and lower surfaces each being the electrical resistors. In other words, in this heat flow switching element, the laminated portion comprises at least multiple electrical resistors, with electrical resistors and phase transition materials alternately laminated, and the upper and lower surfaces are both electrical resistors. As a result, multiple electrical resistors generate heat simultaneously, and this heat is quickly transferred from above and below to the phase transition material, thereby achieving high thermal responsiveness.

[0014] The heat flow switching element according to the seventh invention is characterized in that, in the fifth invention, the laminated portion comprises at least a plurality of the phase transition elements, and the electrical resistor and the phase transition elements are alternately laminated, with the upper and lower surfaces each being the phase transition elements. In other words, in this heat flow switching element, the laminated portion comprises at least multiple phase transition materials, with resistors and phase transition materials stacked alternately, and the upper and lower surfaces are each phase transition materials. Therefore, heat from the electrical resistors is quickly transferred to the multiple phase transition materials, resulting in high thermal responsiveness.

[0015] The heat flow switching element according to the eighth invention is characterized in that, in the third or fourth invention, the electrical resistor is formed on the phase transition material, and the first electrode and the second electrode are formed on the electrical resistor with a gap between them. In other words, in this heat flow switching element, an electrical resistor is formed on a phase transition material, and a first electrode and a second electrode are formed on the electrical resistor with a gap between them. As a result, the first electrode and the second electrode are arranged on the same plane on the electrical resistor, making it possible to construct a thinner element. [Effects of the Invention]

[0016] The present invention provides the following effects. In other words, the heat flow switching element according to the present invention comprises a temperature-changing body containing a material or element whose temperature changes due to external energy, and a phase transition body provided in contact with the temperature-changing body and undergoing a phase transition due to the temperature change. Since the phase transition body has a higher thermal conductivity than either of the phases before or after the phase transition when it undergoes a phase transition, by controlling the temperature to a phase transition to a phase with a different thermal conductivity, the phase transition body will have a higher thermal conductivity than the phases before and after the phase transition, resulting in a large change in thermal conductivity. This allows for a large change in the thermal conductivity of the phase transition body and thus enables control of the heat flow. [Brief explanation of the drawing]

[0017] [Figure 1] This is a cross-sectional view showing a first embodiment of the heat flow switching element according to the present invention. [Figure 2] In the first embodiment, this graph shows the change in thermal conductivity of the phase transition material "Ag2+δSxSe1-x" with respect to temperature, as measured by the laser flash method. [Figure 3] In the first embodiment, this graph shows the change in thermal conductivity of the phase transition material "Ag2+δSxTe1-x" with respect to temperature, as measured by the laser flash method. [Figure 4] In the first embodiment, this graph shows the change in thermal conductivity of the phase transition material "Ag2+δSexTe1-x" with respect to temperature, as measured by the laser flash method. [Figure 5] In the first embodiment, this graph shows the change in thermal conductivity of the phase transition material "(AgyCu1-y)2+δSxSe1-x" with respect to temperature, as measured by the laser flash method. [Figure 6] This is a cross-sectional view showing a second embodiment of the heat flow switching element according to the present invention. [Figure 7] This is a cross-sectional view showing a third embodiment of the heat flow switching element according to the present invention. [Figure 8] This is a cross-sectional view showing a fourth embodiment of the heat flow switching element according to the present invention. [Figure 9] This graph shows the results of the X-ray diffraction experiments in Examples 1(a), 2(b), and 3(c) of the present invention. [Figure 10] This graph shows the time dependence of the surface temperature when measuring thermal permeability using the time-domain thermoreflectance method (TDTR method) in Example 1 of the present invention. [Figure 11] This graph shows the time dependence of the thermal permeability measured by the time-domain thermoreflectance method (TDTR method) in Example 2 of the present invention. [Figure 12] This graph shows the time dependence of the rate of change in thermal conductivity measured by the time-domain thermoreflectance method (TDTR method) in Example 2 of the present invention. [Figure 13] This graph shows the time dependence of the surface temperature when measuring thermal permeability by the time-domain thermoreflectance method (TDTR method) when 0V, 40V, and 50V are applied in Example 2 of the present invention. [Figure 14] This graph shows the time dependence of the surface temperature when measuring thermal permeability by the time-domain thermoreflectance method (TDTR method) when 0V, 40V, and 52V are applied in Example 3 of the present invention. [Figure 15] This graph shows the time dependence of thermal osmosis (a), rate of change of thermal conductivity (b), element temperature (c), leakage current (d), and applied voltage (e) measured by the time-domain thermoreflectance method (TDTR method) in Example 4 of the present invention. [Figure 16] This graph shows the relationship between the thermal turbidity measured by the time-domain thermoreflectance method (TDTR method) and the temperature of the element in Example 4 of the present invention. [Figure 17] This graph shows the relationship between the rate of change in thermal conductivity measured by the time-domain thermoreflectance method (TDTR method) and the temperature of the element in Example 4 of the present invention. [Figure 18] This graph shows the results of the X-ray diffraction experiments in Examples 5(a) and 6(b) of the present invention. [Figure 19] This graph shows the time dependence of the surface temperature during thermal permeability measurement using the time-domain thermoreflectance method (TDTR method) in Example 6 of the present invention. [Figure 20] This graph shows the time dependence of thermal osmosis (a), rate of change of thermal conductivity (b), element temperature (c), leakage current (d), and applied voltage (e) measured by the time-domain thermoreflectance method (TDTR method) in Example 5 of the present invention. [Figure 21] This graph shows the time dependence of thermal osmosis (a), rate of change of thermal conductivity (b), element temperature (c), leakage current (d), and applied voltage (e) measured by the time-domain thermoreflectance method (TDTR method) in Example 6 of the present invention. [Figure 22] This graph shows the relationship between the thermal turbidity measured by the time-domain thermoreflectance method (TDTR method) and the temperature of the element in Example 5 of the present invention. [Figure 23] This graph shows the relationship between the rate of change in thermal conductivity measured by the time-domain thermoreflectance method (TDTR method) and the temperature of the element in Example 5 of the present invention. [Figure 24] This graph shows the relationship between the thermal turbidity measured by the time-domain thermoreflectance method (TDTR method) and the temperature of the element in Example 6 of the present invention. [Figure 25] This graph shows the relationship between the rate of change in thermal conductivity measured by the time-domain thermoreflectance method (TDTR method) and the temperature of the element in Example 6 of the present invention. [Modes for carrying out the invention]

[0018] Hereinafter, a first exemplary embodiment of the heat flow switching element according to the present invention will be described with reference to FIGS. 1 to 3. In the drawings used in the following description, the scale is appropriately changed as necessary so that each part has a size that can be recognized or is easy to recognize.

[0019] As shown in FIG. 1, the heat flow switching element 1 of the present exemplary embodiment includes a temperature changing body 4 including a material or element that changes temperature by external energy, and a phase transition body 5 provided in contact with the temperature changing body 4 and undergoing a phase transition due to the temperature change. The above-mentioned phase transition body 5 is formed of a material having a higher thermal conductivity than either of the phases before and after the phase transition when undergoing the phase transition. Further, the heat flow switching element 1 of the present exemplary embodiment includes a first electrode 2 and a second electrode 3, and the temperature changing body 4 is an electric resistor provided between the first electrode 2 and the second electrode 3 and including a material that generates heat by an electric current generated in response to a voltage applied between the first electrode 2 and the second electrode 3.

[0020] The phase transition body 5 has a chemical formula A 2+δ M (where A is at least one of Ag and Cu, and M is at least one of S, Se, and Te). For example, the phase transition body 5 has a chemical formula Ag 2+δ M (where M is at least one of S, Se, and Te). Note that this A 2+δ M may have a deviation in the element ratio of A element:M element of 2:1 within the range of -0.5 ≤ δ ≤ +0.5 as long as it has a composition that undergoes a phase transition due to a temperature change. Specifically, Ag 2+δ M composed only of Ag as the A element is known to exhibit a phase transition within the range of δ of -0.05 to +0.02. The above-mentioned temperature changing body 4 is, for example, a high electric resistor through which a minute current flows, and is a silicon oxide film (silica, silicon oxide, Si-O) that generates heat by Joule heat due to the current. Silicon oxide is an oxide of silicon. Note that as long as it is a high electric resistor through which a minute current flows, other materials such as a hafnium oxide (hafnia) film and a silicon nitride film may be adopted as the temperature changing body 4.

[0021] The electrical resistance of the temperature-changing element (electrical resistor) 4 is preferably 100 times greater than the electrical resistance of the phase transition element 5. That is, "Joule heat generation = I (current value) 2 The formula is "×R (electrical resistance value) × energizing time," and the temperature change element 4, which has a high electrical resistance value, consumes power per unit time (=I (current value)). 2 Since R (electrical resistance) = I (current) × V (voltage) becomes larger, the heat generation effect is more clearly observed. Furthermore, the thinner the film thickness of these temperature-changing elements 4, the lower the thermal resistance. Therefore, the minute Joule heating effect of the temperature-changing elements 4 allows for efficient heat transfer to the phase transition element 5. In other words, it becomes easy to adjust the temperature to near the phase transition temperature where the heat conduction peaks in response to the applied voltage, thereby further increasing the effect of the heat flow change due to the change in heat conduction of the phase transition element 5.

[0022] In this embodiment, a laminated portion 6 is formed on the first electrode 2, in which a layered temperature change element 4 and a layered phase transition element 5 are stacked, and a second electrode 3 is formed on the laminated portion 6. The first electrode 2 described above may be made of a conductive substrate such as a p-type silicon substrate. Furthermore, the second electrode 3 is formed from a metal such as Mo or Al. An external power supply V is connected to the first electrode 2 and the second electrode 3, and a voltage is applied to them.

[0023] Various film deposition methods can be employed for the temperature-dependent material 4 and phase transition material 5 described above, including sputtering, molecular beam deposition (MBD), atomic layer deposition (ALD), chemical vapor deposition (CVD), chemical solution deposition (CSD), and sol-gel deposition. Molecular beam epitaxy (MBE), known as one of the methods used for crystal growth in semiconductors, is included in the molecular beam deposition (MBD) technique. The above phase transition material 5 is chemical formula A 2+δM is adopted (where A is at least one of Ag or Cu, and M is at least one of S, Se, or Te), but the phase transition temperature differs depending on the composition, and the thermal conductivity of the phases before and after the transition also differs. This chemical formula A 2+δ To obtain highly crystalline thin films for M (where A is at least one of Ag or Cu, and M is at least one of S, Se, or Te), molecular beam deposition (MBD) is mainly employed.

[0024] Figures 2, 3, 4, and 5 show A 2+δ This shows the temperature dependence of the thermal conductivity of M (where A is at least one of Ag and Cu, and M is at least one of S, Se, and Te). The laser flash method was used to determine A at each temperature. 2+δ The thermal conductivity of bulk material M was evaluated. Figure 2 shows the Ag measurement data obtained by the laser flash method. 2+δ S x Se 1-x The temperature dependence of the thermal conductivity of " is shown. Specifically, the composition is "Ag2S 0.2 Se 0.8 "Ag2S 0.4 Se 0.6 "Ag2S 0.5 Se 0.5 "Ag2S 0.6 Se 0.4 "Ag2S 0.8 Se 0.2 The temperature characteristics of the thermal conductivity of "Ag2S" are illustrated. As can be seen from Figure 2, the thermal conductivity is higher in the high-temperature phase above the phase transition temperature compared to the low-temperature phase below the phase transition temperature.

[0025] Figure 3 shows the Ag measurement data obtained by the laser flash method. 2+δ S x Te 1-x The temperature dependence of the thermal conductivity of " is shown. Specifically, the compositions are "Ag2Te" and "Ag2S 0.05 Te 0.95 "Ag2S 0.1 Te 0.9 "Ag2S 0.15 Te 0.85The temperature characteristics of the thermal conductivity of "[ ]" are illustrated. As can be seen from Figure 3, the thermal conductivity is lower in the high-temperature phase above the phase transition temperature compared to the low-temperature phase below the phase transition temperature.

[0026] Figure 4 shows the Ag measurement data obtained by the laser flash method. 2+δ Se x Te 1-x The temperature dependence of the thermal conductivity of " is shown. Specifically, the composition is "Ag2Se" 0.8 Te 0.2 "Ag2Se 0.5 Te 0.5 "Ag2Se 0.4 Te 0.6 "Ag2Se 0.2 Te 0.8 The temperature characteristics of the thermal conductivity of "[ ]" are illustrated. As can be seen from Figure 4, the thermal conductivity is lower in the high-temperature phase above the phase transition temperature compared to the low-temperature phase below the phase transition temperature.

[0027] Figure 5 shows the results of the laser flash method for measuring "(Ag y Cu 1-y ) 2+δ S x Se 1-x The temperature dependence of the thermal conductivity of " is shown. Specifically, the compositions are "AgCuSe" and "AgCuS 0.1 Se 0.8 "Ag 1.05 cuS 0.1 Se 0.9 "Ag 1.08 cuS 0.1 Se 0.9 "Ag 1.13 cuS 0.1 Se 0.9 The temperature characteristics of the thermal conductivity of "Cu2Se" are illustrated. As can be seen from Figure 5, for compositions other than Cu2Se, the thermal conductivity is lower in the high-temperature phase above the phase transition temperature compared to the low-temperature phase below the phase transition temperature. For Cu2Se without Ag, the thermal conductivity is higher in the high-temperature phase above the phase transition temperature compared to the low-temperature phase below the phase transition temperature.

[0028] All of these phase transition materials 5 exhibit higher thermal conductivity at the phase transition temperature than the phases before and after the phase transition. In other words, a peak is observed at the phase transition temperature due to a rapid increase in thermal conductivity. Here, "peak in thermal conductivity" indicates that the thermal conductivity at the phase transition is higher than that of either phase before or after the phase transition. Note that in the temperature dependence data of thermal conductivity measured by the laser flash method shown in Figures 2 to 5, there are some cases where a peak in thermal conductivity is not detected in the temperature range near the phase transition temperature. This is due to the measurement accuracy of the thermal conductivity evaluation device using the laser flash method, and in reality, there is a peak where the thermal conductivity increases sharply. In the laser flash method, thermal diffusivity and specific heat are measured separately, and the thermal conductivity is calculated using the measured results of thermal diffusivity, specific heat, and density. Both thermal diffusivity and specific heat are measured by applying a temperature gradient (temperature difference) to both ends of the sample. In this case, if the temperature difference during measurement is greater than the temperature range of the thermal diffusivity or specific heat peak, it becomes difficult to observe the thermal diffusivity or specific heat peak of the phase transition. For the above reasons, it may be difficult to observe the thermal conductivity peak of the phase transition using the laser flash method, so it is desirable that the temperature difference during measurement be smaller than the temperature range of the thermal diffusivity or specific heat peak. In other words, these phase transition materials 5 have a higher thermal conductivity than either the phase before or after the phase transition.

[0029] As described above, the heat flow switching element 1 of this embodiment comprises a temperature-changing body 4 containing a material or element that generates or cools heat in response to external energy, and a phase transition body 5 provided in contact with the temperature-changing body 4 and undergoing a phase transition due to temperature changes. The phase transition body 5 has a higher thermal conductivity than either the phase before or after the phase transition, as measured by at least one of the thermoreflectance method and the laser flash method. Therefore, the thermal conductivity of the phase transition body 5 can be adjusted by changing the temperature of the temperature-changing body 4, and the heat flow can be controlled through this element.

[0030] In particular, by controlling the temperature to the point where a phase transition occurs to a phase with a different thermal conductivity, the phase transition material 5 will have a higher thermal conductivity than the phases before and after the phase transition, resulting in a large change in thermal conductivity. That is, by making the temperature changer 4 function as a heater or cooler for the phase transition material 5, and by using a phase transition material 5 that has a peak in thermal conductivity when it transitions to a phase with a different thermal conductivity, the thermal conductivity of the phase transition material 5 can be greatly changed to control the heat flow.

[0031] In this embodiment, the temperature-changing element 4 is an electrical resistor provided between the first electrode 2 and the second electrode 3, and contains a material that generates heat due to the current generated in response to the voltage applied between the first electrode 2 and the second electrode 3. Therefore, the thermal conductivity of the phase transition element 5 can be adjusted by the heat generated by the electrical resistor (temperature-changing element 4) due to the current generated in response to the applied voltage. In particular, by using Joule heating caused by voltage application to make the electrical resistor (temperature change element 4) function as a heater for the phase transition element 5, and by using a phase transition element 5 that has a peak in thermal conductivity when transitioning to a phase with a different thermal conductivity, the thermal conductivity of the phase transition element 5 can be greatly changed to control the heat flow.

[0032] Furthermore, phase transition 5 has chemical formula A 2+δ Since M is (where A is at least one of Ag or Cu, and M is at least one of S, Se, or Te), the chemical formula A 2+δ M is a material that exhibits a peak in thermal conductivity when undergoing a phase transition to a phase with a different thermal conductivity, thus enabling a large change in thermal conductivity. Furthermore, since the temperature-changing element 4 is a silicon oxide film that generates Joule heat due to electric current, the silicon oxide film is not an electrically insulating film that does not allow any current to flow even when a voltage is applied, but rather a highly electrical-resistive film that generates Joule heat due to leakage current when a voltage is applied, and can be easily formed as a high-resistivity material.

[0033] Furthermore, a laminated portion 6 is formed on the first electrode 2, in which the temperature-changing element 4 and the phase transition element 5 are stacked, and the second electrode 3 is formed on the laminated portion 6. Therefore, by applying a voltage to the laminated portion 6 sandwiched between the first electrode 2 and the second electrode 3 and allowing a current to flow, the temperature-changing element 4 is heated, and the thermal conductivity of the phase transition element 5 stacked on the temperature-changing element 4 can be efficiently changed.

[0034] Next, second to fourth embodiments of the heat flow switching element according to the present invention will be described below with reference to Figures 6 to 8. In the following descriptions of each embodiment, the same reference numerals will be used for the same components described in the above embodiments, and their descriptions will be omitted.

[0035] The difference between the second embodiment and the first embodiment is that in the first embodiment, a laminated portion 6 is employed in which a temperature-changing element 4 and a phase transition element 5 are stacked one layer at a time on the first electrode 2, whereas in the heat flow switching element 21 of the second embodiment, as shown in Figure 6, the laminated portion 26 comprises at least a plurality of temperature-changing elements (electrical resistors) 4, and the temperature-changing elements 4 and phase transition elements 5 are stacked alternately, with the upper and lower surfaces each being made of temperature-changing elements 4.

[0036] In other words, in the second embodiment, a laminated portion 26 is formed on the first electrode 2, in which a temperature change element 4, a phase transition element 5, and another temperature change element 4 are stacked in that order. In the heat flow switching element 21 of the second embodiment, the laminated portion 6 is equipped with at least a plurality of temperature-changing elements 4, and the temperature-changing elements 4 and the phase transition elements 5 are alternately laminated, with the upper and lower surfaces being temperature-changing elements 4. As a result, multiple temperature-changing elements 4 generate heat simultaneously, and this heat is quickly transferred from above and below to the phase transition elements 5, thereby achieving high thermal responsiveness.

[0037] Next, the difference between the third embodiment and the second embodiment is that in the second embodiment, the upper and lower surfaces of the laminated portion 26 are both temperature-changing elements 4, whereas in the heat flow switching element 31 of the third embodiment, as shown in Figure 7, the laminated portion 36 comprises at least a plurality of phase transition elements 5, and the temperature-changing elements (electrical resistors) 4 and the phase transition elements 5 are alternately laminated, with the upper and lower surfaces each being phase transition elements 5.

[0038] In other words, in the third embodiment, a laminated portion 36 is formed on the first electrode 2, in which the phase transition material 5, temperature change material 4, and phase transition material 5 are stacked in that order. In the heat flow switching element 31 of the third embodiment, the laminated portion 36 is equipped with at least a plurality of phase transition elements 5, and the temperature change element 4 and the phase transition elements 5 are alternately laminated, with the upper and lower surfaces being phase transition elements 5. Therefore, heat from the temperature change element 4, which is an electrical resistor, is quickly transferred to the plurality of phase transition elements 5, thereby achieving high thermal responsiveness.

[0039] Next, the difference between the fourth embodiment and the first embodiment is that in the first embodiment, the first electrode 2 is formed on the lower surface of the laminated portion 6 and the second electrode 3 is formed on the upper surface of the laminated portion 6, whereas in the heat flow switching element 41 of the fourth embodiment, as shown in Figure 8, a temperature changing element (electrical resistor) 4 is formed on the phase transition element 5, and the first electrode 2 and the second electrode 3 are formed on the temperature changing element 4 with a gap between them.

[0040] In other words, in the fourth embodiment, a layered temperature change element 4 is stacked on a layered phase transition element 5, and a first electrode 2 and a second electrode 3 are patterned on the upper surface of the temperature change element 4 using Mo or the like. Alternatively, the thermal flow switching element 41 may be fabricated on an insulating substrate. In the heat flow switching element 41 of the fourth embodiment, a temperature changing element 4 is formed on the phase transition element 5, and the first electrode 2 and the second electrode 3 are formed on the temperature changing element 4 with a gap between them. As a result, the first electrode 2 and the second electrode 3 are arranged on the same plane on the temperature changing element 4, making it possible to construct a thinner element. [Examples]

[0041] An example of the heat flow switching element of the present invention and its evaluation method are shown below. In this embodiment, the laser flash method is used to measure the thermal conductivity of bulk materials, while the pulsed optical thermoreflectance method is used to measure the thermal conductivity of thin films. The pulsed optical thermoreflectance method includes frequency-domain thermoreflectance (FDTR method) and time-domain thermoreflectance (TDTR method), but in this embodiment, the time-domain thermoreflectance (TDTR method) is used as the method for measuring thermal conductivity. In the laser flash method, thermal diffusivity and specific heat are measured to calculate thermal conductivity. In the time-domain thermoreflectance method, thermal osmosis is measured using the surface heating / temperature measurement (FF) method. In the laser flash method, when experimenting with the temperature dependence of bulk thermal conductivity, if a peak in specific heat or thermal diffusivity is observed individually near the phase transition temperature, it is considered that a peak in thermal conductivity has been observed. Similarly, in the time-domain thermoreflectance method, when experimenting with the temperature dependence of thin film thermal conductivity, if a peak in thermal osmosis is observed, it is considered that a peak in thermal conductivity has been observed. In other words, in this invention, "having a peak in thermal conductivity" means that if any of the peaks of specific heat, thermal diffusivity, or thermal osmosis are observed, it is uniquely considered that a peak in thermal conductivity has been observed. Furthermore, materials exhibiting a peak in thermal conductivity are preferably those exhibiting a peak in specific heat during the phase transition, and in particular, materials that exhibit a phase transformation with a large entropy change during the phase transition are preferred. The thermal conductivity is measured using the TDTR method, which involves instantaneously heating a thin film sample formed on a substrate with a pulsed laser and measuring the rate of decrease or increase in surface temperature due to thermal diffusion into the thin film to determine the thermal diffusivity or thermal permeability in the film thickness direction. Note that the TDTR method that directly measures thermal diffusivity (backside heating / surface temperature measurement (RF) method) requires a transparent substrate through which the pulsed laser can penetrate. Therefore, if the substrate is not transparent, the thermal conductivity is measured using the surface heating / temperature measurement (FF) method, which measures thermal permeability and converts it to thermal conductivity. This measurement requires a metal film, such as Mo or Al.

[0042] In the embodiments of this invention, thermal osmosis is measured using the TDTR method with a surface heating / temperature measurement (FF) method. The thermal osmosis was measured using the FF method of the TDTR method with a Picotherm NanoTR device. Measurements under zero bias were performed at room temperature. In the embodiments of this invention, the thermal osmosis was measured by applying a voltage between the first electrode and the second electrode and passing a current. We also attempted to measure the thermal osmosis while measuring the temperature of the heat flow switching element by connecting a thermocouple to one of the electrodes. The time during which the voltage was applied was measured to investigate the change in thermal osmosis over time. The TDTR (FF) method described above involves instantaneously heating the element from the Mo film side with a pulsed laser and measuring the rate at which the surface temperature decreases due to heat diffusion into the thin film, thereby measuring the thermal permeability of the thin film. A high thermal permeability, i.e., a high thermal conductivity, means that heat is transferred more rapidly, and the time it takes for the temperature to decrease is faster.

[0043] Thermal conductivity is calculated from thermal diffusivity or thermal permeability using the following formula. Thermal conductivity k = (thermal diffusivity α) × volumetric heat capacity = (Thermal diffusivity α) × (Specific heat × Density) Thermal conductivity k = (thermal osmosis b) 2 / Volumetric heat capacity =(thermal effusivity b) 2 (Specific heat × Density) Therefore, for example, the rate of change Δk of thermal conductivity after voltage application can be evaluated using the following formula. Δk = k(V) / k(0) - 1 Δk = α(V) / α(0) - 1 Δk=b(V) 2 / b(0) 2 -1 k(V): Thermal conductivity when voltage is applied (W / mK) k(0): Thermal conductivity without voltage application (W / mK) α(V): Thermal diffusivity when voltage is applied (m 2 / s) α(0): Thermal diffusivity without voltage application (m 2 / s) b(V): Thermal conductivity (Ws) when voltage is applied. 0.5 / m 2 K) b(0): Thermal conductivity (Ws) without applied voltage 0.5 / m 2 K) In other words, in this embodiment, the rate of change Δk of the thermal conductivity of the thin film after voltage application is evaluated using only the value of the thermal permeability measured by the TDTR method (FF method), assuming that the volumetric heat capacity does not change before and after voltage application.

[0044] An embodiment of the present invention was constructed by laminating a high electrical resistance layer (temperature-changing element), a phase transition layer, and an electrode layer on an electrode substrate using the following materials, and the change in thermal conductivity was measured by the TDTR method (FF method). Examples 1 to 5 of the present invention use Ag-S-Se as the phase transition material and Si-O (silicon oxide) as the high electrical resistance material. Example 6 of the present invention uses Ag-S-Te as the phase transition material and Si-O (silicon oxide) as the high electrical resistance material. The Ag-S-Se and Ag-S-Te films are deposited by molecular beam deposition (MBD). The Si-O film is deposited by sputtering using an SiO2 target. X-ray diffraction experiments have confirmed that the Ag-S-Se and Ag-S-Te films are crystalline materials, while the Si-O film is amorphous. The measurement of electrical resistance (specific resistance) was carried out, and it was confirmed that the electrical resistivity of the Si-O film was 100 times or more greater than that of the Ag-S-Se film or Ag-S-Te film of Examples 1 to 6. In this example, although the film thicknesses of the Si-O film (temperature change body 4) and the Ag-S-Se film or Ag-S-Te film (phase transition body 5) were different, it was confirmed that the electrical resistance value of the Si-O film was 100 times or more greater than that of the Ag-S-Se film or Ag-S-Te film of Examples 1 to 6. That is, this Si-O film is a high electrical resistance body through which a minute current flows, and furthermore, since the film thickness is thin and the thermal resistance value is small, heat can be efficiently transmitted to the Ag-S-Se film or Ag-S-Te film (phase transition body 5) due to the minute Joule heating effect of the Si-O film. (a), (b), and (c) of FIG. 9 and (a) of FIG. 18 each show 0.6 Se 0.4 , Ag2S 0.45 Se 0.55 , Ag2S 0.5 Se 0.5 , Ag2S 0.10 Se 0.90 the results of the thin film X-ray diffraction experiment of. Using a Cu tube target, with the incident angle set to 0 degrees, as a result of performing 2θ-θ measurement (general symmetric measurement) in the range of 2θ = 20 to 100 degrees, it was confirmed that Ag2S 0.6 Se 0.4 , Ag2S 0.45 Se 0.55 , Ag2S 0.5 Se 0.5 , Ag2S 0.10 Se 0.90 is a single-phase film having high crystallinity. Since it is formed on a Si substrate, a diffraction peak derived from the Si substrate is detected near 33 degrees (it has been confirmed by composition analysis such as surface SEM-EDX that the above Ag-S-Se film does not contain Si). Also, thin film X-ray diffraction (glancing angle incident X-ray diffraction) with the incident angle set to 1 degree was carried out, and it has been confirmed that the above Ag-S-Se film is a single-phase film.

[0045] Ag2S 1-x Se xIn the system, in the low-temperature phase near room temperature below the phase transition temperature, when x ≤ 0.6, it has the same crystal structure as Ag2S (monoclinic, space group P21 / c), and when x ≥ 0.7, it has the same crystal structure as Ag2Se (orthorhombic, space group P212121). (In the composition range of 0.6 < x < 0.7, depending on the film formation conditions, a mixed phase or different crystal structures may occur.) Ag2S 0.6 Se 0.4 ,Ag2S 0.45 Se 0.55 ,Ag2S 0.5 Se 0.5 takes the same crystal structure as Ag2S, Ag2S 0.10 Se 0.90 has been confirmed to take the same crystal structure as Ag2Se. Note that the crystal structure of the high-temperature phase above the phase transition temperature is cubic, space group Im-3m for all x composition ranges (0.0 ≤ x ≤ 1.0) in Ag2S 1-x Se x Figure 18(b) shows the results of the thin film X-ray diffraction experiment of Ag2S 0.95 Te 0.05 . The measurement conditions are the same as above. It has been confirmed that the Ag-S-Te film is a single-phase film (it has been confirmed by composition analysis such as surface SEM-EDX that the above Ag-S-Te film does not contain Si). Ag2S 0.95 Te 0.05 has the same crystal structure as Ag2S. All of the Ag-S-Se films or Ag-S-Te films shown below as examples are crystalline materials, and at zero bias (when no external voltage is applied), they are materials that exhibit a very low thermal conductivity of less than 1 W / mK at room temperature.

[0046] "Example 1" The structure of the heat flow switching element of Example 1 is as follows. Electrode substrate: P-type semiconductor Si substrate (thickness 0.5 mm) High electrical resistance layer (temperature change body): Si-O (thickness 50 nm) Phase transition layer: Ag2S 0.6 Se 0.4 (thickness 150 nm) Electrode layer: Mo (thickness 100 nm) Note that Ag2S in the phase transition layer 0.6 Se 0.4 The thermal conductivity at room temperature is 0.33 W / mK. The phase transition temperature is approximately 70°C, and as can be seen from the temperature dependence of the thermal conductivity measured by the laser flash method in Figure 2, the thermal conductivity at room temperature is lower than that of the high-temperature phase above the phase transition temperature.

[0047] Table 1 shows the evaluation results of the heat flow switch in Example 1, measured by the TDTR method (FF method). In Example 1, the thermal fuscurity at zero bias (no external voltage applied) was 1000 Ws 0.5 / m 2 It can be seen that the temperature is below K, and the rate of increase in thermal conductivity after voltage application is large. When a voltage of 40V or higher is applied, a current of 1mA or more flows, Joule heating occurs, and it was confirmed that the temperature of the element is rising. When a voltage of about 60V is applied and the high-resistivity material heats up further, the temperature of the element rises to a temperature near the phase transition temperature, and the thermal conductivity reaches its maximum value. In other words, the Si-O of the high-resistivity material heats up due to leakage current, and the Ag2S of the phase transition material is released. 0.6 Se 0.4 The rise in temperature to near the phase transition temperature, which exhibits a peak in thermal conduction, is considered to be the origin of the heat flow switching.

[0048] [Table 1]

[0049] Figure 10 shows the time dependence of the surface temperature when the thermal osmosis was measured by the TDTR method (FF method), and the surface temperature on the vertical axis is normalized to the maximum temperature when heated with a pulsed laser (maximum 1). The notation on the vertical axis is also called the thermoreflectance signal. As a result of these measurements, it was confirmed that in Example 1 above, as the applied voltage is increased and the leakage current increases, the thermal osmosis increases, and the rate of increase in thermal conductivity after voltage application also increases. In other words, from the results in Figure 10, it can be seen that when a voltage is applied and the leakage current is large, the rate of decrease in surface temperature is faster, and the thermal osmosis is larger, i.e., the thermal conductivity is larger, compared to when no voltage is applied. Furthermore, an X-ray diffraction experiment was performed on the element after the test, and Ag2S 0.6 Se 0.4 No change in crystallinity has been detected.

[0050] Example 2 Next, the structure of the heat flow switching element in Example 2 is as follows. Electrode substrate: P-type semiconductor Si substrate (thickness 0.5 mm) High electrical resistance layer (temperature-dependent material): Si-O (thickness 50 nm) Phase transition layer: Ag2S 0.45 Se 0.55 (Thickness 150nm) Electrode layer: Mo (thickness 100 nm) Note that Ag2S in the phase transition layer 0.45 Se 0.55 The thermal conductivity at room temperature is 0.33 W / mK. The thermal osmosis was measured using the TDTR method (FF method) while controlling the leakage current flowing through Si-O and the amount of heat generated by stepwise changing the voltage from 0V, 40V, and 50V. In Example 2 as well, a significant change in thermal osmosis after voltage application was observed compared to the thermal osmosis at zero bias.

[0051] Figures 11 and 12 show the time dependence of thermal osmosis and thermal conductivity change rate measured by the TDTR method (FF method). Table 2 shows the results at a specific time interval. In Example 2, the thermal osmosis under zero bias (no external voltage applied) was 1000 Ws 0.5 / m 2 The temperature is less than K. The leakage current values ​​while 40V and 50V were applied were 0.22A and 0.26A, respectively, and remained almost constant over time. When a voltage of 40V was applied, a slight decrease in thermal conductivity was observed. When 50V was applied, the amount of heat generated increased, and the temperature rose to near the phase transition temperature where the thermal conductivity peaked, with the thermal conductivity reaching 1000Ws. 0.5 / m 2 The thermal conductivity increased sharply above K, and a very large change of approximately 700% was observed. After applying a 50V voltage, when the voltage was returned to 0V or 40V, the thermal conductivity returned to the original 0V or 40V level. When 50V was applied again, an increase of approximately 700% in thermal conductivity was confirmed, similar to the first time. In other words, the repeatability and cycle characteristics of the heat flow switch were confirmed by measurement using the TDTR method (FF method). Furthermore, X-ray diffraction experiments were conducted on the element after the test, and Ag2S 0.45 Se 0.55 No change in crystallinity has been detected.

[0052] [Table 2]

[0053] Furthermore, the thermal conductivity is lower at 40V than at 0V, and a greater heat flow switching characteristic can be obtained between 40V and 50V than between 0V and 50V. Figure 13 shows the time dependence of surface temperature when thermal osmosis was measured by the time-domain thermoreflectance method (TDTR method) under the application of 0V, 40V, and 50V. It can be seen that the surface temperature decreases faster and the thermal osmosis is higher, i.e., the thermal conductivity is higher, when 50V is applied. This time dependence of surface temperature has been confirmed to show a similar profile even when cyclic testing (repeated voltage changes) is performed.

[0054] Examples 3, 4, 5, and 6 Next, the structures of the heat flow switching elements in Examples 3 and 4 are as follows. Electrode substrate: P-type semiconductor Si substrate (thickness 0.5 mm) High electrical resistance layer (temperature-dependent material): Si-O (thickness 50 nm) Phase transition layer: Ag2S 0.5 Se 0.5 (Thickness 130nm) Electrode layer: Mo (thickness 100 nm) Furthermore, the structure of the heat flow switching elements in Examples 5 and 6 is as follows for the phase transition layer, while the other configurations are the same as in Examples 3 and 4. Phase transition layer of Example 5: Ag2S 0.10 Se 0.90 (Thickness 100nm) Phase transition layer of Example 6: Ag2S 0.95 Te 0.05 (Thickness 100nm)

[0055] Examples 3 and 4 have similar compositions, but the timing of Si-O fabrication differs, resulting in different electrical resistivity of Si-O and thus different heat generation due to leakage current. Note that the phase transition layer is Ag2S 0.5 Se 0.5 The thermal conductivity at room temperature is 0.32 W / mK. In Examples 3 and 4, measurements using the TDTR method (FF method) also revealed that the thermal osmosis after voltage application changed significantly compared to the thermal osmosis under zero bias. In Example 3, the same cycle characteristics as in Example 2 were confirmed using the TDTR method (FF method). At 0V, the thermal fuscurvature of this element was 803 Ws 0.5 / m2 It exhibits a value of approximately K. When a voltage of 40-41V is applied, a current of 0.14-0.16A flows, and the thermal osmosis is 666-706Ws. 0.5 / m 2 It shows a value of approximately K.

[0056] When a voltage of 50-52V is applied, a current of 0.21-0.23A flows, and the thermal osmosis is 1200Ws. 0.5 / m 2 The values ​​will start to show above K. Cycle characteristic experiments were conducted eight times, alternating between applying a voltage of 40-41V and 50-52V to change the amount of heat generated. Figure 14 shows the time dependence of surface temperature when thermal turbulence was measured using the TDTR method (FF method) of Example 3 when 0V, 40V, and 52V were applied. The 40V and 52V values ​​are the measurement results from the second cycle. It can be seen that when 52V was applied, the rate of decrease in surface temperature was faster, and the thermal turbulence was larger, i.e., the thermal conductivity was higher. Furthermore, for all 8 cycles, all data from 40-41V and all data from 50-52V showed similar time dependence profiles for the surface temperature shown in the figure, experimentally confirming the highly reproducible cycle characteristics of thermal conductivity. In addition, X-ray diffraction experiments were performed on the element after the test, and Ag2S 0.5 Se 0.5 No change in crystallinity has been detected. Furthermore, Figure 19 shows the time dependence of the surface temperature when the thermal permeability was measured by the TDTR method (FF method) of Example 6 when 0V and 49V were applied. It can be seen that when 49V was applied, the rate of decrease in surface temperature was faster, and the thermal permeability was larger, i.e., the thermal conductivity was higher. In other words, in the Ag-S-Te film as well, similar to the example of the Ag-S-Se film, the TDTR method (FF method) showed that the thermal permeability after voltage application changed significantly compared to the thermal permeability at zero bias.

[0057] In Example 4, a thermocouple was placed on a Si substrate (electrode), and the thermal flow switching characteristics were evaluated using the TDTR method (FF method) while monitoring the temperature of the element. To prevent current leakage through the tip of the thermocouple, it was confirmed that the Si-O film and the tip of the thermocouple were not in contact before the measurement was performed. Figures 15, 20, and 21 show the time dependence of thermal osmosis (a), rate of change of thermal conductivity (b), element temperature (c), leakage current (d), and applied voltage (e) for Examples 4, 5, and 6. These values ​​were obtained by gradually increasing the voltage, gradually increasing the amount of heat generated by the leakage current, and gradually increasing the element temperature, while measuring the thermal osmosis using the TDTR method (FF method). In Examples 4, 5, and 6, a significant change in thermal osmosis after voltage application was observed compared to the thermal osmosis at zero bias.

[0058] Figures 16, 17, and 22-25 show plots of the relationship between thermal osmosis measured by the TDTR method (FF method) and the element temperature, and the relationship between the rate of change of thermal conductivity and the element temperature, with the horizontal axis being the element temperature, for Examples 4, 5, and 6. As a result, at temperatures near the phase transition temperature, behavior similar to the peak of bulk thermal conductivity measured by the laser flash method shown in Figures 2 and 3 was observed. It is thought that, similar to the laser flash method, a peak in thermal conductivity was observed in the temperature range near the phase transition temperature of the phase transition material using the time-domain thermoreflectance method (TDTR method). In other words, it is thought that the Si-O film, which is a high electrical resistance material, generated heat, and the Ag-S-Se film or Ag-S-Te film, which is a phase transition material, rose in temperature to a temperature near the phase transition temperature where thermal conduction peaks are observed, which is the origin of the large heat flow switching characteristics (large change in thermal conductivity). In fact, at temperatures above the phase transition temperature, the thermal osmosis (thermal conductivity) takes a value smaller than the peak. Figures 2 and 3 show the temperature dependence of the thermal conductivity of Ag-S-Se or Ag-S-Te systems, and the behavior in which the thermal conductivity is higher in the high-temperature phase above the phase transition temperature compared to the low-temperature phase below the phase transition temperature is also reproduced.

[0059] As can be seen from Figures 16 and 17, there is a temperature range where the rate of change of thermal osmosis and thermal conductivity, measured by the TDTR method (FF method), shows a negative broad peak, and the rate of change of thermal osmosis and thermal conductivity is at its lowest value, at a temperature slightly lower than the temperature at which the rate of change of thermal osmosis and thermal conductivity shows a positive peak. Similar behavior was confirmed in Example 2. (The thermal conductivity measured by the TDTR method (FF method) is lower at 40V than at 0V, and a greater heat flow switching characteristic is obtained between 40V and 50V than between 0V and 50V.) These results suggest that by fine-tuning the amount of heat generated by leakage current and precisely controlling the region where the thermal conductivity shows a negative broad peak and the region where the thermal conductivity shows a positive steep peak, a large heat flow switching performance can be obtained. Furthermore, as can be seen from Examples 1 to 5 above, in the Ag-S-Se phase transition layer, the crystalline phase differs between the low-temperature phase and the high-temperature phase. However, both crystalline phases have the characteristic of having a higher thermal conductivity than either the phase before or after the phase transition. In other words, although the crystalline structure of the low-temperature phase near room temperature differs between Example 5, where the Se composition ratio of the phase transition layer is 0.90, and Examples 1 to 4, where the Se composition ratio is ≤0.6, both exhibit a peak in thermal osmosis (thermal conductivity) at temperatures near the phase transition temperature.

[0060] It should be noted that the technical scope of the present invention is not limited to the embodiments and examples described above, and various modifications can be made without departing from the spirit of the invention.

[0061] In the above embodiments, an electrical resistor containing a material that generates heat due to a current generated in response to a voltage applied between the first electrode and the second electrode was used as the temperature-changing element. However, an electromagnetic cooler containing a material or element that cools using electromagnetic external energy such as a Peltier element or a solid calorific effect material (electric calorific effect material, magnetocalorific effect material) may also be used. Furthermore, a combination of an electrical resistor and an electromagnetic cooler may be used as the temperature-changing element. That is, in the case of phase transition materials such as Ag-S-Te, where the thermal conductivity decreases at temperatures higher than the phase transition temperature, it is possible to operate in the high-temperature range using an electrical resistor, and to lower the temperature of the phase transition material using an electromagnetic cooler, thereby increasing the thermal conductivity. [Explanation of Symbols]

[0062] 1, 21, 31, 41… Heat flow switching element, 2… First electrode, 3… Second electrode, 4… Temperature change element (electrical resistor), 5… Phase transition element, 6, 26, 36… Laminated section

Claims

1. A temperature-changing body containing a material or element whose temperature changes due to external energy, The system comprises a phase transition element provided in contact with the temperature change element, which undergoes a phase transition due to a temperature change, The phase transition material has a higher thermal conductivity than either the phase before or after the phase transition, as measured by at least one of the thermoreflectance method and the flash method, First electrode and, It comprises a second electrode, A heat flow switching element characterized in that the temperature-changing element is an electrical resistor provided between the first electrode and the second electrode and contains a material that generates heat due to a current generated in response to a voltage applied between the first electrode and the second electrode.

2. In the heat flow switching element according to claim 1, The aforementioned phase transition material has chemical formula A ２＋δ A heat flow switching element characterized by M (where A is at least one of Ag and Cu, and M is at least one of S, Se, and Te).

3. In the heat flow switching element according to claim 1 or 2, A thermal flow switching element characterized in that the electrical resistor is a silicon oxide film that generates Joule heat when subjected to electric current.

4. In the heat flow switching element according to claim 1 or 2, A laminated portion is formed on the first electrode, in which the electrical resistor and the phase transition material are stacked. A heat flow switching element characterized in that the second electrode is formed on the laminated portion.

5. In the heat flow switching element according to claim 4, The heat flow switching element is characterized in that the laminated portion comprises at least a plurality of electrical resistors, and the electrical resistors and the phase transition material are alternately laminated, with the upper and lower surfaces each being electrical resistors.

6. In the heat flow switching element according to claim 4, The heat flow switching element is characterized in that the laminated portion comprises at least a plurality of the phase transition elements, and the electrical resistor and the phase transition elements are alternately laminated, with the upper and lower surfaces each being the phase transition elements.

7. A temperature-changing body comprising a material or element whose temperature changes due to external energy, The system comprises a phase transition element provided in contact with the temperature change element, which undergoes a phase transition due to a temperature change, The phase transition material has a higher thermal conductivity than either the phase before or after the phase transition, as measured by at least one of the thermoreflectance method and the flash method, First electrode and, It comprises a second electrode, The temperature-changing element is an electrical resistor containing a material that generates heat due to a current generated in response to a voltage applied between the first electrode and the second electrode. The electrical resistor is formed on the phase transition material, A heat flow switching element characterized in that the first electrode and the second electrode are formed on the electrical resistor with a gap between them.

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