Thermistors and related products and systems

Abstract

To provide a thermistor capable of achieving high sensitivity and good thermistor characteristics at 200°C to 250°C.SOLUTION: A thermistor element 100 including at least a thermistor film 50 and electrodes 51, 52, having a B constant (K) at 200°C to 250°C is 8000 or more, has: a thermistor film containing gallium (Ga) and manganese (Mn); a first electrode 51 arranged on a first surface of the thermistor film; and a second electrode 52 arranged on a second surface located on the opposite side of the first surface.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to thermistors that use thermistor films and to products and systems thereof. [Background technology]

[0002] Conventionally, in products such as electronic devices or systems equipped with electronic devices, temperature sensors and gas sensors are used for temperature compensation of the electronic devices, and thermistors are used for the temperature sensors and gas sensors. There are two types of thermistors: Negative Temperature Coefficient (NTC) thermistors and Positive Temperature Coefficient (PTC) thermistors.

[0003] Negative temperature coefficient (NTC) thermistors utilize the phenomenon where resistance decreases as temperature rises, and most thermistors fall into this category as they have the properties of n-type semiconductors, where resistance decreases exponentially over a wide range of temperatures. Positive temperature coefficient (PTC) thermistors are special thermistors that utilize the phenomenon where resistance increases rapidly when the temperature rises and exceeds a certain temperature.

[0004] In recent years, electronic devices have become smaller and thinner, and there is a demand for smaller and thinner temperature sensors and gas sensors used in electronic devices, as well as thermistor elements used in these sensors. In response to such demands, thermistor elements using thermistor films have been considered, but they have been unsatisfactory due to their weak mechanical strength and insufficient thermistor characteristics.

[0005] Patent Document 1 describes an NTC thermistor film formed by a room temperature vacuum powder injection method. However, the NTC thermistor film described in Patent Document 1 has problems such as low mechanical strength, difficulty in thinning, and the need for a complex process using a vacuum device.

[0006] Patent Document 2 also describes a thermistor film formed by the aerosol deposition method. However, when trying to obtain a thermistor film by the aerosol deposition method, it is necessary to forcefully spray the aerosol onto a substrate using a small-diameter nozzle and collide the thermistor raw material particles to obtain a dense film with good thermistor properties, and even if such a film is obtained, it is difficult to expand the area of ​​the film, and even if it is formed into a film over a long period of time, the adhesion and surface flatness are poor, and the thermistor film formed by the method described in Patent Document 2 has a problem that the thermistor properties are insufficient unless the film is a thick film of several microns or more, or a film that is still not satisfactory has been obtained.

[0007] As described above, in the past, when attempting to obtain a thermistor film, simply depositing fine particles of thermistor raw materials resulted in a film with weak mechanical strength and insufficient thermistor characteristics. Furthermore, even when fine particles of thermistor raw materials were sprayed onto a substrate and collided to form a dense film, sufficient thermistor characteristics could not be obtained unless a film of several microns or more was formed, and even films that provided such thermistor characteristics had problems such as poor adhesion and surface flatness.

[0008] Furthermore, Patent Document 3 describes a thin-film thermistor element, but the thin-film thermistor element described in Patent Document 3 has the problem that unless a certain amount of oxygen and nitrogen is contained in the electrodes, adhesion with the thermistor film cannot be ensured, and it is also difficult to realize a vertical thermistor element. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2010-251757 A [Patent Document 2] JP 2015-115438 A [Patent Document 3] Patent No. 5509393 Summary of the Invention [Problem to be solved by the invention]

[0010] An object of the present invention is to provide a thermistor that can achieve high sensitivity and good thermistor characteristics at temperatures between 200°C and 250°C. [Means for solving the problem]

[0011] As a result of intensive research to achieve the above-mentioned object, the inventors have succeeded in forming a crystalline thermistor film containing Ga and Mn by using a mist CVD method under specific conditions, and have found that the film thus obtained can achieve high sensitivity and good thermistor characteristics at 160°C to 250°C. After obtaining the above findings, the inventors conducted further studies and completed the present invention.

[0012] That is, the present invention relates to the following inventions. [1] A thermistor comprising at least a thermistor film and an electrode, the thermistor having a B constant (K) of 8000 or more at 200°C to 250°C. [2] The thermistor according to [1] above, which has a B constant (K) of 8000 or more at 160°C to 250°C. [3] The thermistor according to [1] above, which has a B constant (K) of 10,000 or more at 200°C to 250°C. [4] The thermistor according to any one of [1] to [3] above, wherein the thermistor film contains Ga. [5] The thermistor according to [4] above, wherein the Ga content in the thermistor film is 30 atomic % or more of the metal components. [6] The thermistor according to any one of [1] to [5] above, wherein the thermistor film contains a crystalline oxide semiconductor. [7] The thermistor according to any one of the above [1] to [6], wherein the thermistor film contains Ga and Mn. [8] The thermistor according to any one of [1] to [7], wherein the thermistor has two or more electrodes. [9] The thermistor according to [8], comprising a first electrode arranged on a first surface side of the thermistor film, and a second electrode arranged on a second surface side opposite the first surface.

[10] A product comprising the thermistor according to any one of [1] to [9] above.

[11] The product according to

[10] above, which is a temperature sensor or a temperature control device.

[12] A system including the thermistor according to any one of [1] to [9] above or the product according to

[10] or

[11] above. Effect of the Invention

[0013] The thermistor of the present invention exhibits high sensitivity and excellent thermistor characteristics at temperatures between 200°C and 250°C. [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic diagram showing a thermistor of the present invention; [Diagram 2] 1 is a schematic diagram showing a thermistor of the present invention; [Diagram 3] 1 is a schematic diagram showing a thermistor of the present invention; [Figure 4] 1 is a schematic diagram showing a thermistor of the present invention; [Diagram 5] 1 is a schematic diagram showing a thermistor of the present invention; [Figure 6] FIG. 1 is a schematic diagram showing a configuration in which a thermistor according to the present invention is mounted on a circuit board. [Figure 7] FIG. 1 is a schematic diagram of a film forming apparatus (mist CVD apparatus) used in Example 1. [Figure 8] FIG. [Figure 9] FIG. [Figure 10] FIG. 2 is a diagram showing XRD data in Example 1. [Figure 11] 1 is a configuration diagram showing a preferred embodiment of a fuel cell system in which the product of the present invention is used. [Figure 12]FIG. 4 is a diagram showing the evaluation results of thermistor characteristics in Examples 1 to 3. [Figure 13] FIG. 1 is a diagram showing the evaluation results of thermistor characteristics in Examples 4 to 6. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The thermistor of the present invention is a thermistor including at least a thermistor film and electrodes, and is characterized in that the B constant (K) at 200°C to 250°C is 8000 or more. The thermistor film preferably contains a crystal or a crystalline oxide semiconductor capable of realizing thermistor characteristics. The crystal preferably contains gallium (Ga), and more preferably contains Ga and manganese (Mn). The crystal may have a corundum structure, a β-gallium structure, or another crystal structure. The crystal may be a single crystal or a polycrystal. In the present invention, the crystal preferably contains a metal oxide as a main component. Here, the "main component" may be, for example, the metal oxide in the crystal at an atomic ratio of 0.5 or more. In the present invention, the metal oxide in the crystal preferably has an atomic ratio of 0.7 or more, and more preferably 0.8 or more. The metal oxide is not particularly limited, but preferably contains Ga, and more preferably contains Ga and Mn. The content of Ga in the crystal is not particularly limited as long as it does not impede the object of the present invention, but is preferably 30 atomic % or more, more preferably 60 atomic % or more, and most preferably 90 atomic % or more in the metal component. The content of Mn in the crystal is preferably 0.1 atomic % or more relative to the content of Ga in the metal oxide. The crystal preferably contains Ga and Mn, and may be a mixed crystal containing one or more metal components other than Ga and Mn. Examples of other metal components include aluminum (Al), indium (In), strontium (Sr), and transition metals other than Mn. More specifically, examples of the other metal components include Al, In, Sr, copper (Cu), zinc (Zn), palladium (Pd), iridium (Ir), rhodium (Rh), ruthenium (Ru), iron (Fe), molybdenum (Mo), tungsten (W), titanium (Ti), tantalum (Ta), zirconium (Zr), hafnium (Hf), niobium (Nb), vanadium (V), cobalt (Co), nickel (Ni), ruthenium (Ru), tin (Sn), and chromium (Cr).

[0016] The crystal may contain a dopant. By including the dopant, the electrical properties can be improved. Examples of the dopant include n-type dopants and p-type dopants. Examples of the n-type dopants include tin (Sn), germanium (Ge), silicon (Si), vanadium (V), niobium (Nb), tantalum (Ta), titanium (Ti), zirconium (Zr), and hafnium (Hf). Examples of the p-type dopants include magnesium (Mg) and calcium (Ca).

[0017] The crystalline oxide semiconductor preferably contains gallium (Ga), and more preferably contains Ga and manganese (Mn). The crystalline oxide semiconductor may have a corundum structure, a β-gallium structure, or another crystal structure. It may be a single crystal or a polycrystal. The crystalline oxide semiconductor usually contains the dopant and / or oxygen vacancies. The carrier concentration of the dopant is not particularly limited, but may be, for example, about 1×10 14 / cm 3 ~1×10 22 / cm 3 is preferably about 1×10 15 / cm 3 ~1×10 22 / cm 3It is more preferable that the content of Ga in the preferred crystalline oxide semiconductor is 30 atomic % or more, more preferably 60 atomic % or more, and most preferably 90 atomic % or more, based on the metal component, without any particular limitation as long as the object of the present invention is not hindered. The content of Mn in the preferred crystalline oxide semiconductor is preferably 0.1 atomic % or more, based on the Ga content in the metal oxide. The crystalline oxide semiconductor preferably contains Ga and Mn, but may be a mixed crystal containing one or more metal components other than Ga and Mn. Examples of other metal components include aluminum (Al), indium (In), strontium (Sr), and transition metals other than Mn. More specifically, examples of the other metal components include Al, In, Sr, copper (Cu), zinc (Zn), palladium (Pd), iridium (Ir), rhodium (Rh), ruthenium (Ru), iron (Fe), molybdenum (Mo), tungsten (W), titanium (Ti), tantalum (Ta), zirconium (Zr), hafnium (Hf), niobium (Nb), vanadium (V), cobalt (Co), nickel (Ni), ruthenium (Ru), tin (Sn), and chromium (Cr).

[0018] The thermistor film is a film used in a thermistor, and preferably contains the crystal or the crystalline oxide semiconductor as a main component. Here, the "main component" may mean, for example, that the crystal or the crystalline oxide semiconductor in the thermistor film is contained in an atomic ratio of 0.5 or more. In the present invention, the metal oxide in the film preferably has an atomic ratio of 0.7 or more, more preferably 0.8 or more. The thickness of the thermistor film is not particularly limited, but is preferably 10 μm or less, more preferably 0.001 μm to 10 μm.

[0019] The thermistor film is suitable for use in various thermistors. In the present invention, the thermistor is preferably a thermistor having a thermistor film, a first electrode disposed on a first surface side of the thermistor film, and a second electrode disposed on a second surface side opposite to the first surface.

[0020] Preferred embodiments of the thermistor will be described below, but the present invention is not limited to these embodiments.

[0021] A preferred embodiment of the thermistor of the present invention is characterized by comprising at least the thermistor film and an electrode. In the present invention, the thermistor is preferably a vertical device. Such a preferred thermistor element has low resistance and excellent heat dissipation. The thermistor of the present invention preferably has a first electrode disposed on the first surface side of the thermistor film and a second electrode disposed on the second surface side located opposite to the first surface of the thermistor film. FIG. 1 is a schematic diagram showing a preferred embodiment of the thermistor of the present invention. The thermistor element 100 has a thermistor film 50, a first electrode 51 disposed on the first surface side of the thermistor film 50, and a second electrode 52 disposed on the second surface side located opposite to the first surface of the thermistor film 50. The first electrode 51 and the second electrode 52 are configured to be conductive in the vertical direction. The thermistor element may further have a base 54 disposed in contact with the first electrode 51. The base 54 may include a metal film having electrical conductivity. By providing a conductive metal film on the surface of the base, it is advantageous that the thermistor element can be easily mounted on a circuit board. The base 54 is not particularly limited, but may be, for example, a crystal substrate having a corundum structure. By forming the thermistor film by growing the crystal on the substrate, it is possible to obtain a thermistor film with a flatter surface. FIG. 2 is a schematic diagram showing a preferred embodiment of the thermistor of the present invention. The thermistor element 200 has a thermistor film 50, a first electrode 51 arranged on the first surface side of the thermistor film 50, and a second electrode 52 arranged on the second surface side opposite to the first surface of the thermistor film 50. The thermistor element 200 of this embodiment may have a layer 53 located between the first electrode 51 and the thermistor film 50. The layer 53 may be a crystalline film. FIG. 3 is a schematic diagram showing a preferred embodiment of the thermistor of the present invention. The thermistor element 300 has a thermistor film 50, a first electrode 51 arranged on the first surface of the thermistor film 50, and a second electrode 52 arranged on the second surface opposite to the first surface of the thermistor film 50. As shown in FIG. 3, it is also possible to provide a plurality of second electrodes. Fig. 4 is a schematic diagram showing a preferred embodiment of the thermistor of the present invention. Thermistor element 400 has a thermistor film 50, a first electrode 51 arranged on a first surface of the thermistor film 50, and a second electrode 52 arranged on a second surface of the thermistor film 50 opposite to the first surface. Fig. 5 is a schematic diagram showing a preferred embodiment of the thermistor of the present invention.The thermistor element 500 has a thermistor film 50, a first electrode 51 disposed on a first surface of the thermistor film 50, and a second electrode 52 disposed on a second surface located opposite to the first surface of the thermistor film 50. When the base 54 disposed in contact with the first electrode 51 is, for example, a sapphire substrate, it is also possible to dispose the upper surface electrode electrically connected to the first electrode 51 on the same side as the second electrode 52. Also, as shown in FIG. 6, the first electrode 51 of the thermistor element 100 can be electrically mounted on the first electrode 71 on the circuit board 70 of the electronic device 1000 by soldering or the like via the conductive base 54, and the second electrode located on the upper surface of the thermistor element 300 and the second electrode 72 of the circuit board can be electrically connected by wire bonding 60 or the like. In this way, it can be used as a vertical device.

[0022] (thermistor film) The thermistor film will be described in more detail. The thermistor film may be an NTC thermistor film or a PTC thermistor film. The thermistor film can be obtained, for example, by the following preferred embodiment.

[0023] The preferred embodiment will be described below. In the present invention, the formation of the thermistor film is preferably carried out by a mist CVD method, more preferably by atomizing and forming droplets from a raw material solution of the thermistor film (atomization and droplet formation process), supplying a carrier gas to the obtained atomized droplets (including mist) to transport the atomized droplets to a substrate (transport process), and then thermally reacting the atomized droplets on the substrate (film formation process).

[0024] (Base) The substrate is not particularly limited, and may be crystalline or amorphous. The material of the substrate is also not particularly limited as long as it does not impede the object of the present invention, and may be a known substrate, an organic compound, or an inorganic compound. In the present invention, it is preferable that the substrate contains a conductive material or crystal. The shape of the substrate may be any shape, and is effective for all shapes, for example, a plate shape such as a flat plate or a disk, a fiber shape, a rod shape, a columnar shape, a prism shape, a tube shape, a spiral shape, a sphere shape, a ring shape, etc., but in the present invention, a substrate is preferable. In the present invention, the substrate is preferably one having crystals on a part or all of its surface, more preferably a crystal substrate having crystals on all or a part of the main surface on the crystal growth side, and most preferably a crystal substrate having crystals on the entire main surface on the crystal growth side. The crystal is not particularly limited as long as it does not impede the object of the present invention, but it is preferable that it is a trigonal or hexagonal crystal, and more preferably a crystal having a corundum structure. In the present invention, for example, when the crystal substrate has a corundum structure, the main surface is preferably a c-plane, an a-plane, or an m-plane, since the thermistor characteristics can be further improved. The crystal substrate may have an off-angle, and examples of the off-angle include an off-angle of 0.1° to 12.0°. Here, the "off-angle" refers to the angle between the substrate surface and the crystal growth surface. The shape of the substrate is not particularly limited as long as it is a plate-like substrate that serves as a support for the crystalline oxide semiconductor film. The substrate may be an insulating substrate or a semiconductor substrate, but in the present invention, it is also preferable that the substrate has a conductive metal film, such as nickel foil or precious metal foil, formed on the surface. In the present invention, the substrate is also preferably a conductive substrate. Examples of the conductive substrate include one or more metals belonging to Groups 3 to 15 of the periodic table, preferably one or more transition metals, and more preferably one or more metals belonging to Groups 7 to 11 of the periodic table.The shape of the substrate is not particularly limited, and may be substantially circular (e.g., circular, elliptical, etc.) or polygonal (e.g., triangular, square, rectangular, pentagonal, hexagonal, heptagonal, octagonal, nonagonal, etc.), and various shapes can be suitably used. In the present invention, the shape of the film formed on the substrate can be set by making the substrate have a preferred shape. In addition, in the present invention, a large-area substrate can be used, and the area of ​​the thermistor film can be increased by using such a large-area substrate. The substrate material of the crystal substrate is not particularly limited, and may be a known material as long as it does not impede the object of the present invention. The substrate material having the corundum structure is, for example, α-Al. 2 O 3 (Sapphire substrate) or α-Ga 2 O 3 Preferred examples include a c-plane sapphire substrate, an a-plane sapphire substrate, an m-plane sapphire substrate, and an α-gallium oxide substrate (c-plane, a-plane, or m-plane).

[0025] In the present invention, the substrate preferably has a flat surface, but the substrate may have an uneven shape on a part or all of the surface. When the substrate is a crystalline substrate, the quality of the crystal growth of the thermistor film can be improved, which is preferable. The substrate having the uneven shape may have an uneven portion formed of a concave or convex portion on a part or all of the surface, and the uneven portion is not particularly limited as long as it is formed of a convex or concave portion, and may be an uneven portion formed of a convex portion, an uneven portion formed of a concave portion, or an uneven portion formed of a convex portion and a concave portion. The uneven portion may be formed of regular convex portions or concave portions, or may be formed of irregular convex portions or concave portions. In the present invention, the uneven portion is preferably formed periodically, and more preferably patterned periodically and regularly. The shape of the uneven portion is not particularly limited, and examples thereof include a stripe shape, a dot shape, a mesh shape, and a random shape. In the present invention, a dot shape or a stripe shape is preferable, and a dot shape is more preferable. In addition, when the unevenness is patterned periodically and regularly, the pattern shape of the unevenness is preferably a polygonal shape such as a triangle, a quadrangle (for example, a square, a rectangle, or a trapezoid), a pentagon, or a hexagon, a circle, or an ellipse. When the unevenness is formed in a dot shape, the lattice shape of the dots is preferably a lattice shape such as a square lattice, an oblique lattice, a triangular lattice, or a hexagonal lattice, and more preferably a triangular lattice. The cross-sectional shape of the recess or protrusion of the unevenness is not particularly limited, and examples thereof include a U-shape, an inverted U-shape, a wave shape, or a polygonal shape such as a triangle, a quadrangle (for example, a square, a rectangle, or a trapezoid), a pentagon, or a hexagon.

[0026] (Raw material solution) The raw material solution is not particularly limited as long as it is a raw material solution of a thermistor film and can be atomized and / or turned into droplets, and may contain an inorganic material or an organic material. In the present invention, the raw material solution usually contains a metal of the crystalline oxide. The metal may be a simple metal or a metal compound, and is not particularly limited as long as it does not impede the object of the present invention. The content of the metal in the raw material solution is not particularly limited, but is preferably 0.001% by weight to 80% by weight, more preferably 0.01% by weight to 80% by weight.

[0027] In the present invention, the raw material solution can be suitably used in which the metal is dissolved or dispersed in an organic solvent or water in the form of a complex or salt. Examples of the complex include acetylacetonate complexes, carbonyl complexes, ammine complexes, and hydride complexes. Examples of the salt include organic metal salts (e.g., metal acetates, metal oxalates, and metal citrates), metal sulfides, metal nitrates, metal phosphates, and metal halides (e.g., metal chlorides, metal bromides, and metal iodides).

[0028] The solvent of the raw material solution is not particularly limited, and may be an inorganic solvent such as water, an organic solvent such as alcohol, or a mixed solvent of an inorganic solvent and an organic solvent. In the present invention, the solvent preferably contains water, more preferably is water or a mixed solvent of water and alcohol, and most preferably is water. More specifically, examples of the water include pure water, ultrapure water, tap water, well water, mineral water, hot spring water, spring water, fresh water, and seawater, and in the present invention, ultrapure water is preferred. Furthermore, when water is used as the solvent, a thermistor film useful for a thermistor having a B constant (K) of 10,000 or more at 200°C to 250°C can be easily obtained, and when a lower alcohol is used as the solvent, a thermistor film useful for a thermistor having a B constant (K) of 8,000 or more at 160°C to 250°C can be easily obtained.

[0029] The raw material solution may be mixed with additives such as hydrohalic acid and an oxidizing agent. Examples of the hydrohalic acid include hydrobromic acid, hydrochloric acid, and hydroiodic acid, and among these, hydrobromic acid and hydroiodic acid are preferred. Examples of the oxidizing agent include hydrogen peroxide (H 2 O 2 ), Sodium peroxide (Na 2 O 2 ), barium peroxide (BaO 2 ), Benzoyl peroxide (C 6 H 5 CO) 2 O 2 Examples of peroxides include hypochlorous acid (HClO), perchloric acid, nitric acid, ozone water, and organic peroxides such as peracetic acid and nitrobenzene. The raw material solution may contain the dopant. By adding a dopant to the raw material solution, the properties of the resulting film can be controlled.

[0030] (Atomization / dropletization process) In the atomization / dropletization step, the raw solution is converted into atomized droplets. The atomization / dropletization means is not particularly limited as long as it can atomize and / or convert the raw solution into droplets, and may be a known atomization means, but in the present invention, it is preferable that the atomization / dropletization means uses ultrasonic waves. The atomized droplets preferably have an initial velocity of zero and float in the air, and are more preferably a mist that floats in space and can be transported as a gas, rather than being sprayed like a spray. The droplet size of the atomized droplets is not particularly limited, and may be droplets of about several mm, but is preferably 50 μm or less, and more preferably 1 to 10 μm.

[0031] (Transportation process) In the transport step, a carrier gas is supplied to the atomized droplets obtained in the atomization / dropletization step, and the atomized droplets are transported to the substrate by the carrier gas. The type of carrier gas is not particularly limited as long as it does not impede the object of the present invention, and suitable examples include oxygen, ozone, inert gases such as nitrogen and argon, and reducing gases such as hydrogen gas and forming gas. In the present invention, it is more preferable that the carrier gas is oxygen or an inert gas. In addition, the type of carrier gas may be one type, but may be two or more types, and a dilution gas with a changed carrier gas concentration (for example, a 10-fold dilution gas, etc.) may be further used as a second carrier gas. In addition, the number of supply points of the carrier gas may be not only one but also two or more. The flow rate of the carrier gas is not particularly limited, but is preferably 0.01 to 20 L / min, more preferably 0.1 to 10 L / min. In the case of a diluent gas, the flow rate of the diluent gas is preferably 0.001 to 10 L / min, and more preferably 0.1 to 5 L / min.

[0032] (Film forming process) In the film-forming step, the atomized droplets are thermally reacted to form the thermistor film on the substrate. The thermal reaction may be performed as long as the atomized droplets react with heat, and the reaction conditions are not particularly limited as long as they do not impede the object of the present invention. In this step, the thermal reaction is usually performed at a temperature equal to or higher than the evaporation temperature of the solvent. The thermal reaction may be performed under any atmosphere, such as a vacuum, a non-vacuum, a non-oxygen atmosphere, a reducing gas atmosphere, or an oxygen atmosphere, but in the present invention, the thermal reaction is preferably performed under a non-vacuum atmosphere, and more preferably under a nitrogen atmosphere or an oxygen atmosphere. The thermal reaction may be performed under any condition, such as atmospheric pressure, pressurized pressure, or reduced pressure, but in the present invention, the thermal reaction is preferably performed under atmospheric pressure. The thickness of the resulting film can also be easily adjusted by adjusting the film-forming time. In the present invention, the thermistor film may be a single-layer film or a multi-layer film.

[0033] In the present invention, it is also preferable to carry out an annealing treatment after the film formation step. The annealing temperature is not particularly limited as long as it does not impede the object of the present invention, and is usually 300°C to 1100°C, and preferably 500°C to 1000°C. The annealing time is usually 1 minute to 48 hours, preferably 10 minutes to 24 hours, and more preferably 30 minutes to 12 hours. The annealing may be carried out in any atmosphere as long as it does not impede the object of the present invention.

[0034] The thermistor film obtained as described above is of good quality and has excellent surface properties such as adhesion, and can be used as is or after treatment such as peeling or processing, for example by laminating it with an electrode using known means for use in a thermistor.

[0035] A suitable method for manufacturing the thermistor includes forming a first electrode, forming the thermistor film by mist CVD so that at least a portion of the thermistor film is in contact with the first electrode, and forming a second electrode by mist CVD so that at least a portion of the thermistor film is in contact with the thermistor film. FIG. 8 shows an example of the manufacturing method. A first electrode 51 is formed on a substrate 54, and a thermistor film 50 is grown by mist CVD so that at least a portion of the thermistor film is in contact with the first electrode 51. A second electrode 52 is then formed. FIG. 9 shows an example of a collective manufacturing method. A first electrode layer 510 is formed on a large substrate 540. A thermistor film 5000 is formed by mist CVD so that at least a portion of the thermistor film 5000 is in contact with the first electrode layer 510 to obtain an aggregate, and then the aggregate is diced vertically and horizontally to obtain a plurality of thermistor elements. A second electrode 52 may be formed on each of the thermistor elements.

[0036] The thermistor is used in a temperature sensor or a temperature control device in a conventional manner, and the temperature sensor or the temperature control device equipped with the thermistor is further applied to a product or a system such as an electronic device using a known means. Examples of the product include a product using a temperature sensor or a temperature control device of 200° C. or more. In the present invention, the thermistor can also be suitably used in a system including at least the product and a CPU. The product is not particularly limited, and examples thereof include a mobile terminal, a commercial device, a cooking device, a manufacturing device, a gas processing device, a CPU-equipped device, a base station for a mobile phone or the like, a 5G wireless device, a sensor device for a car, and a temperature compensation element for a new device (e.g., IoT, AI, etc.).

[0037] A preferred embodiment using the temperature sensor will be described, but the present invention is not limited thereto. Fig. 11 is a block diagram showing an example of a power generation system including the product and a CPU (controller). The power generation system 30 includes, for example, a fuel cell system 32, which includes a fuel processor 33 that performs steam reforming, aqueous shift reaction, and selective oxidation reaction on raw gas such as city gas to generate fuel gas mainly composed of hydrogen, a stack (fuel cell stack) 34 that generates power by chemically reacting the fuel gas and oxidant gas supplied from the fuel processor 33, an inverter 35 that converts the output DC power obtained by power generation in the stack 34 into AC power, a controller (CPU) 36 that controls a series of operations of starting, power generation, termination, and stopping the fuel cell system 32, a blower 37 that supplies air containing oxygen as an oxidant gas to the stack 34, and a heat exchanger 38 that recovers heat generated when the stack 34 generates power and stores it in a water tank as hot water, and is provided with a temperature control device at 200°C to 250°C inside. In Fig. 7, the fuel cell system 32 is connected to commercial AC via a distribution board 39 installed in a home, for example. A load 40 such as a home appliance or industrial product is connected between the distribution board 39 and the fuel cell system. When the stack 34 starts generating electricity, electricity is supplied to the load 40 via the inverter 35, the load 40 operates, and the heat generated by the power generation of the stack 34 is also utilized to efficiently store the heat as hot water in the water storage tank 31. The water storage tank 31 is provided with a temperature sensor as the sensor 41, which controls the temperature of the water storage tank 31. Although not shown, the fuel processor 33 is also provided with a gas sensor, which controls the generation of fuel gas. As described above, the thermistor film is useful in any system in which a temperature control device or a temperature sensor can be used.

[0038] Examples of the present invention will be described below, but the present invention is not limited to these.

[0039] Example 1 1. Film deposition equipment The mist CVD apparatus 1 used in this embodiment will be described with reference to FIG. 7. The mist CVD apparatus 1 includes a carrier gas source 2a for supplying a carrier gas, a flow rate control valve 3a for adjusting the flow rate of the carrier gas sent from the carrier gas source 2a, a carrier gas (dilution) source 2b for supplying a carrier gas (dilution), a flow rate control valve 3b for adjusting the flow rate of the carrier gas (dilution) sent from the carrier gas (dilution) source 2b, a mist source 4 for containing a raw material solution 4a, a container 5 for containing water 5a, an ultrasonic vibrator 6 attached to the bottom surface of the container 5, a film formation chamber 7, a supply pipe 9 connecting the mist source 4 to the film formation chamber 7, a hot plate 8 installed in the film formation chamber 7, and an exhaust port for exhausting mist, droplets, and exhaust gas after the thermal reaction. A substrate 10 is installed on the hot plate 8.

[0040] 2. Preparation of Stock Solutions Manganese acetylacetonate and gallium acetylacetonate were mixed in water so that the atomic ratio of Ga:Mn in the resulting film was 100:2, and this was used as a raw material solution.

[0041] 3. Preparation for film deposition The raw material solution 4a obtained in 2 above was placed in the mist generating source 4. Next, a sapphire substrate was placed on the hot plate 8 as the substrate 10, and the hot plate 8 was operated to heat it up to 900°C. Next, the flow rate control valves 3a and 3b were opened, and carrier gas was supplied from the carrier gas supply means 2a and 2b, which are the carrier gas sources, into the film formation chamber 7, and the atmosphere in the film formation chamber 7 was sufficiently replaced with the carrier gas, after which the flow rate of the carrier gas was adjusted to 3 L / min. Nitrogen was used as the carrier gas. The flow rate of the carrier gas (dilution) was also set to 0.5 L / min.

[0042] 4. Film formation Next, the ultrasonic vibrator 6 was vibrated at 2.4 MHz, and the vibration was propagated to the raw material solution 4a through the water 5a, thereby atomizing the raw material solution 4a to generate mist 4b. This mist 4b was introduced into the film-forming chamber 7 through the supply pipe 9 by the carrier gas, and the mist thermally reacted near the substrate 10 at 500°C under atmospheric pressure to form a film with a thickness of 0.5 μm on the substrate 10. The film-forming time was 60 minutes. The obtained film had excellent adhesion without peeling, and also had sufficient mechanical strength. The results of XRD are shown in FIG. 10. From FIG. 10, it is clear that the obtained film is α-Ga 2 O 3 It is clear that the material contains ZnO and has a corundum structure. The resistance was measured to evaluate the thermistor characteristics. The evaluation results are shown in FIG. 12. It is clear from FIG. 12 that the material has good NTC thermistor characteristics. The B constant was 10337 at 200°C to 250°C.

[0043] (Examples 2 to 3) Thermistor films were obtained as Examples 2 and 3 in the same manner as in Example 1, except that the film composition ratios were as shown in Table 1 below. The films obtained as Examples 2 and 3 were excellent in adhesion without peeling, and had sufficient mechanical strength, similar to Example 1. Furthermore, when the resistance was measured and the thermistor properties were evaluated, they had good NTC thermistor properties, similar to the thermistor film of Example 1 (FIG. 12, Table 1).

[0044] [Table 1]

[0045] (Examples 4 to 6) Thermistor films were obtained in the same manner as in Example 1, except that methanol was used as a solvent instead of water, and the film composition ratio was as shown in Table 2 below. Each of the films obtained in Examples 4 to 6 was a film with excellent adhesion without peeling, and had sufficient mechanical strength, similar to Example 1. Furthermore, when the resistance value was measured and the thermistor characteristics were evaluated, it was found to have good NTC thermistor characteristics, similar to the thermistor film of Example 1 (FIG. 13, Table 2).

[0046] [Table 2] [Industrial Applicability]

[0047] The crystal, crystalline oxide semiconductor, and thermistor film of the present invention are useful for thermistor elements and can be used for temperature sensors and gas sensors for temperature compensation of electronic devices. Furthermore, such temperature sensors and gas sensors are useful in products such as electronic devices or systems equipped with electronic devices. [Explanation of symbols]

[0048] 1 Film deposition equipment 2a Carrier gas source 2b Carrier gas (dilution) source 3a Flow control valve 3b Flow control valve 4. Mist Source 4a Raw material solution 4b Raw material fine particles 5 containers 5a water 6 Ultrasonic transducer 7 Deposition chamber 8. Hot Plate 9 Supply pipe 10 Substrate 30 Power Generation System 31 Water Tank 32 Fuel Cell System 33 Fuel processor 34 Stack 35 Inverter 36 Controller 37 Blower 38 Heat exchanger 39 Distribution Board 40 Load 41 Sensors 50 Thermistor film 51 1st electrode 52 2nd electrode 100 Thermistor element 200 Thermistor element 300 Thermistor element 400 Thermistor element 500 Thermistor element

Claims

1. A thermistor comprising at least a thermistor film and electrodes, the thermistor film comprising a crystalline oxide having a corundum structure or a β-galloy structure, and having a B constant (K) of 8000 or more at 200°C to 250°C.

2. 2. The thermistor according to claim 1, which has a B constant (K) of 8000 or more at 160° C. to 250° C.

3. 2. The thermistor according to claim 1, wherein the B constant (K) at 200° C. to 250° C. is 10,000 or more.

4. 4. The thermistor according to claim 1, wherein the thermistor film contains a uniaxially oriented crystalline oxide.

5. The thermistor according to any one of claims 1 to 4, wherein the thermistor film contains Ga.

6. 6. The thermistor according to claim 5, wherein the Ga content in said thermistor film is 30 atomic % or more of the metal components.

7. 7. The thermistor according to claim 1, wherein the thermistor film comprises a crystalline oxide semiconductor.

8. 8. The thermistor according to claim 1, wherein the thermistor film contains Ga and Mn.

9. The thermistor according to any one of claims 1 to 8, comprising two or more electrodes.

10. 10. The thermistor according to claim 9, further comprising a first electrode disposed on a first surface of the thermistor film, and a second electrode disposed on a second surface opposite the first surface.

11. A product comprising the thermistor according to any one of claims 1 to 10.

12. 12. The article of manufacture of claim 11 which is a temperature sensor or a temperature control device.

13. A system comprising a thermistor according to any one of claims 1 to 10 or a product according to claim 11 or claim 12.

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