WO2016114296A1

WO2016114296A1 - Vanadium dioxide

Info

Publication number: WO2016114296A1
Application number: PCT/JP2016/050814
Authority: WO
Inventors: 廣瀬　左京
Original assignee: 株式会社村田製作所
Priority date: 2015-01-15
Filing date: 2016-01-13
Publication date: 2016-07-21
Also published as: JPWO2016114296A1

Abstract

In this vanadium dioxide, or vanadium dioxide doped with other atoms, which has a high heat absorption capacity and releases heat slowly, the metal vanadium content is 61.45-61.8 wt%.

Description

Vanadium dioxide

The present invention relates to vanadium dioxide or vanadium dioxide doped with other atoms.

With the recent improvement in performance of electronic equipment, the number of electronic components such as CPU (Central Processing Unit), power amplifier, FET (Field Effect Transistor), IC (Integrated Circuit), voltage regulator, etc., which become heat sources, has increased and introduced. The increase in energy generated overlaps with the problem of heat generation. In particular, mobile devices such as smartphones and tablet terminals have a problem that the heat deteriorates the capacity of the battery and seriously affects the reliability of the electronic devices to be configured. Therefore, it is required to control the temperature inside the device to a higher degree.

Control of the heat generated from the heat source as described above is performed by a cooling fan, a heat pipe, a heat sink, a thermal sheet, a Peltier element, or the like, which is an existing heat management solution. A cooling device in which a fan or a Peltier element is combined is described (see Patent Document 1).

However, the cooling device combining the heat sink and the fan or the Peltier element as described above has a relatively complicated structure and increases the size of the device, particularly for thin devices such as smartphones and tablet terminals. Hateful. Furthermore, since power is consumed, it is disadvantageous from the viewpoint of low power consumption (battery life).

Therefore, for thin devices such as smartphones and tablet terminals, the temperature is currently controlled only by means of heat dissipation through the housing, and the heat source and the housing are thermally coupled by a thermal sheet or the like to release heat.

JP 2010-223497 A

放熱 Heat dissipation through the enclosure as described above is limited because the surface area of the enclosure is limited. Therefore, the temperature of each heat source is measured, and when the temperature exceeds a predetermined temperature, the performance of the CPU or the like is limited (suppressing heat generation itself). That is, the temperature rise of the housing may hinder the performance of the CPU or the like. Naturally, in heat dissipation through such a case, in other words, heat dissipation by heat transfer to the entire device, heat is also transferred to the battery, which can lead to a decrease in battery capacity over time.

In view of this, the present inventor has arranged vanadium oxide (specifically, vanadium dioxide), which is a ceramic material that absorbs heat accompanying a crystal structure phase transition or a magnetic phase transition, by placing it near the heat source of an electronic device. We considered a cooling device that can be used with a power supply. However, the study of the present inventors has revealed that vanadium dioxide may have different endothermic amounts and endothermic characteristics depending on the sample, even if the VO ₂ structure is shown by X-ray structural analysis.

In order to use vanadium dioxide as a heat storage, cold storage or cooling element, it is necessary to produce and use vanadium dioxide having a large endothermic amount and exhibiting endothermic / exothermic characteristics according to the purpose. Specifically, in the case of an element that repeatedly generates heat on a short time scale, it is desirable that the cooling device rapidly absorbs heat and generates heat (heat radiation) in addition to a large amount of heat absorption. On the other hand, when it is preferable to absorb heat, it is preferable to quickly absorb the heat, but it may be preferable to release the absorbed heat slowly. For example, if the target is in an environment where heat insulation is high and it is difficult to release heat to the outside, if the absorbed heat is released quickly, the heat radiation to the outside cannot catch up and the temperature of the device to be cooled is kept high. There is a risk of it.

Therefore, an object of the present invention is to provide vanadium dioxide containing vanadium oxide as a main component or vanadium dioxide doped with other atoms, which has a large endothermic amount and generates heat (heat radiation) slowly.

As a result of studying the above problems, the present inventor has found that vanadium dioxide is a material (VO ₂ ) in which V and O are 1: 2, but the contents of vanadium and oxygen deviate from the stoichiometric composition to some extent. Even in the case, the same crystal structure can be maintained, and the composition of vanadium and oxygen in the vanadium dioxide crystal may be different from the stoichiometric amount depending on the sample. It has been found that the temperature decreases and the heat absorption and heat generation characteristics change. That is, it has been found that by controlling the vanadium dioxide composition, in other words, the vanadium content in vanadium dioxide within a desired range, a desired endothermic amount and endothermic property can be obtained.

The present inventor has found that the difference in vanadium dioxide can be clarified based on the metal vanadium content (hereinafter also referred to as “V metal amount”) in vanadium dioxide determined by a titration method.

Moreover, although the composition of vanadium dioxide can be specified by the amount of oxygen, conventionally, it has been difficult to directly determine the amount of oxygen in vanadium dioxide. However, the present inventor has found that it can be indirectly quantified by the weight increase rate when vanadium dioxide (VO ₂ ) is oxidized to vanadium pentoxide (V ₂ O ₅ ), and the difference in vanadium dioxide is also determined by this weight increase rate. Found that can be clarified.

According to the first aspect of the present invention, vanadium dioxide or vanadium dioxide doped with other atoms, wherein the metal vanadium content is 61.45 wt% or more and 61.8 wt% or less (herein, the above-mentioned The other atom is an atom selected from the group consisting of W, Ta, Mo and Nb;
When the other atom is W, the content mole part of the other atom when the total of vanadium and the other atom is 100 mole parts is greater than 0 mole part and 1.5 mole parts or less,
When the other atom is Ta, Mo, or Nb, the content mole part of the other atom when the total of vanadium and the other atom is 100 mole parts is greater than 0 mole part and 10 mole parts or less. )
Is provided.

According to a second aspect of the invention, the formula:
V _1-x M _x O ₂
(Wherein M is W, Ta, Mo or Nb;
x is greater than or equal to 0,
When M is W, X is 0.015 or less,
When M is Ta, Mo or Nb, x is 0.1 or less. )
Vanadium dioxide represented by or vanadium dioxide doped with other atoms,
There is provided vanadium dioxide or vanadium dioxide doped with other atoms, characterized in that the metal vanadium content is 61.45 wt% or more and 61.8 wt% or less.

According to the third aspect of the present invention, a ceramic material containing vanadium dioxide and / or vanadium dioxide doped with other atoms is provided.

According to a fourth aspect of the present invention, there is provided a cooling device comprising the vanadium dioxide or other atom-doped vanadium dioxide or the ceramic material.

According to a fifth aspect of the present invention, there is provided an electronic component comprising the cooling device.

According to the sixth aspect of the present invention, there is provided an electronic apparatus comprising the cooling device or the electronic component.

According to a seventh aspect of the present invention, there is provided a method for producing vanadium dioxide or vanadium dioxide doped with other atoms, wherein the metal vanadium content is 61.45 wt% or more and 61.8 wt% or less. A featured method is provided.

According to an eighth aspect of the present invention, there is provided a method for controlling the heat absorption or heat dissipation characteristics of vanadium dioxide or vanadium dioxide doped with other atoms, wherein the metal vanadium content is 61.45 wt% or more and 61.8 wt%. % Or less is provided.

According to the present invention, by setting the metal vanadium content to 61.45 wt% or more and 61.8 wt% or less, vanadium dioxide having a large endotherm and generating heat slowly and vanadium dioxide doped with other atoms are doped. Can be provided.

FIG. 1 shows the results of DSC measurement of sample number 1. FIG. 2 shows the results of DSC measurement of sample number 2. FIG. 3 shows the results of DSC measurement of sample number 3. FIG. 4 shows the result of TG-DTA measurement of sample number 1. FIG. 5 shows the results of TG-DTA measurement of sample numbers 1 to 3.

The vanadium dioxide of the present invention and vanadium dioxide doped with other atoms (hereinafter collectively referred to as “vanadium oxide of the present invention”) absorb heat by latent heat. Such vanadium dioxide and vanadium dioxide doped with other atoms can obtain a high cooling effect by temporally leveling heat by temporarily absorbing excess heat by latent heat. It becomes possible.

The above-mentioned vanadium dioxide and vanadium dioxide doped with other atoms are usually used as a ceramic material containing this as a main component.

The “main component” means a component contained in the ceramic material by 60% by mass or more, particularly 80% by mass or more, preferably 90% by mass or more, more preferably 95% by mass or more, and further preferably 98% by mass. For example, it means a component contained in, for example, 98.0 to 99.8% by mass or substantially 100%.

In the present invention, “vanadium dioxide” means vanadium oxide exhibiting a VO ₂ structure by X-ray structural analysis (typically using a powder X-ray diffraction method). In the present specification, “vanadium dioxide doped with other atoms” means that vanadium atoms in vanadium dioxide are substituted with other atoms, and an oxidation which shows a corresponding crystal structure by X-ray structural analysis. It means vanadium.

The vanadium dioxide or vanadium dioxide doped with other atoms of the present invention may contain impurities other than vanadium dioxide or vanadium dioxide doped with other atoms. Impurities include, but are not limited to, other ceramic materials such as vanadium dioxide or vanadium oxide other than vanadium dioxide doped with other atoms, such as V ₂ O ₃ and V ₂ O ₅ , such as glass, and Na, Al , Cr, Fe, Ni, Mo, Sb, Ca, Si and oxides thereof.

The amount of the impurities is preferably as small as possible, for example, 5% by mass or less, preferably 3% by mass or less, more preferably 1% by mass or less, still more preferably 0.5% by mass or less, and even more preferably 0%. .2% by mass or less, and most preferably substantially 0% by mass (that is, substantially free of impurities).

The other atoms are not particularly limited as long as they can be contained in vanadium oxide as a doping element, but are preferably W, Ta, Mo, and Nb, and more preferably W.

When the other atom is W, the content mole part of the other atom when the total of vanadium and other atoms is 100 mole parts is preferably larger than 0 mole part and 1.5 mole parts or less.

When the other atom is Ta, Mo or Nb, the content mole part of the other atom when the total of vanadium and the other atom is 100 mole parts is preferably greater than 0 mole part and 10 mole parts or less. .

In one embodiment, the vanadium dioxide or vanadium dioxide doped with other atoms of the present invention has the formula:
V _1-x M _x O ₂
(Wherein M is W, Ta, Mo or Nb;
x is greater than or equal to 0,
When M is W, x is 0.015 or less,
When M is Ta, Mo or Nb, x is 0.1 or less. )
Or one or more oxides represented by: Note that M corresponds to “another atom” and is not an essential component, and the molar portion of M may be 0. In this case, the compound represented by the above formula is vanadium dioxide.

In one embodiment, the vanadium oxide of the present invention is a compound represented by the above formula where x is 0, that is, vanadium dioxide.

In another embodiment, the vanadium oxide of the present invention is a compound in which M is W, that is, tungsten-doped vanadium dioxide.

The temperature at which the vanadium oxide of the present invention undergoes phase transition is appropriately selected according to the object to be cooled, the purpose of cooling, etc. For example, when the object to be cooled is a CPU, the temperature is 20 to 100 ° C., preferably 40 to 60. It is preferable that the phase transition occurs at ° C. The temperature at which the vanadium oxide of the present invention undergoes phase transition, that is, the temperature at which the vanadium oxide exhibits latent heat, can be adjusted by adding (doping) other atoms and adjusting the amount of the atoms added.

In one embodiment, the vanadium dioxide or vanadium dioxide doped with other atoms of the present invention has a metal vanadium content of 61.45 wt% or more and 61.8 wt% or less. The metal vanadium content can be measured by a titration method. By setting the metal vanadium content within the above range, the vanadium oxide of the present invention has a large latent heat, and can generate heat absorption relatively quickly, and can generate heat gradually.

In another embodiment, the vanadium dioxide of the present invention or vanadium dioxide doped with other atoms is 650 ° C. relative to the weight at 200 ° C. in differential thermal-thermogravimetric measurement (TG-DTA). The rate of increase in the weight of “A” is “hereinafter simply referred to as“ weight increase rate ”” is 9.45% or more and 9.95% or less, preferably higher than 9.5% but not higher than 9.95%. This weight increase is attributed to the oxidation of VO ₂ to V ₂ O ₅ in the case of vanadium dioxide, for example. Even if this weight increase rate shows the same crystal structure by X-ray structural analysis, it may differ with samples. And by making this weight increase rate into the said range, the vanadium oxide of this invention has a big latent heat, and it will raise | generate heat absorption comparatively quickly, and it will become possible to raise | generate heat_generation | fever moderately.

Usually, it is difficult to quantify the composition of oxygen in the material, but vanadium dioxide or vanadium dioxide doped with other atoms consists essentially of vanadium and oxygen, so the weight increase rate and metal vanadium Content becomes a value according to the composition ratio of V and O in vanadium oxide, and the amount of oxygen in vanadium oxide can be quantified indirectly. That is, by controlling the weight increase rate and the metal vanadium content, it becomes possible to determine the amount of latent heat (endothermic amount) and the endothermic characteristics. In addition, when the vanadium oxide of the present invention contains an impurity that easily affects the oxygen content, an error may occur in the weight increase rate, so that a raw material having the highest possible purity is used, or metal vanadium is used. It is preferable to control the content.

In one embodiment, the weight increase rate of the vanadium dioxide of the present invention or vanadium dioxide doped with other atoms is 9.45% or more and 9.95% or less, preferably more than 9.5% and 9.95% or less. In addition, the metal vanadium content is 61.45 wt% or more and 61.8 wt% or less.

In the vanadium dioxide of the present invention or vanadium dioxide doped with other atoms, the method of setting the metal vanadium content to 61.45 wt% or more and 61.8 wt% or less is not particularly limited. Vanadium oxide (for example, V ₂ O ₃ , V ₂ O _5, etc.) is mixed in an appropriate ratio, preferably so that the stoichiometric ratio of V and O is 1: 2, and the oxygen partial pressure is controlled. The method of processing at high temperature is mentioned.

Conditions for performing the above method, for example, temperature, time, pressure, atmosphere, and the like may vary depending on the raw materials used, but those skilled in the art can appropriately determine them. Can be adjusted.

In the ceramic material of the present invention, even when the weight increase rate is 9.45% or more and 9.95% or less, it is processed at a high temperature or heat-treated in a reducing atmosphere while controlling the oxygen partial pressure as described above. be able to.

Alternatively, vanadium dioxide or other atom doped vanadium dioxide is heat treated in a reducing atmosphere to provide vanadium dioxide or other atom doped dioxide having the desired weight gain or vanadium content. Vanadium can also be obtained.

Accordingly, the present invention provides a method for producing vanadium dioxide or vanadium dioxide doped with other atoms, wherein the vanadium dioxide or vanadium dioxide doped with other atoms has a metal vanadium content of 61.45 wt% or more. .8 wt% or less, or the rate of increase in weight at 650 ° C. with respect to the weight at 200 ° C. in the differential thermal-thermogravimetric simultaneous measurement is 9.45% or more and 9.95% or less, preferably 9.5% Provided is a method characterized by being higher than 9.95%.

The present invention also provides a method for controlling the endothermic or heat dissipation properties of vanadium dioxide or vanadium dioxide doped with other atoms, wherein the vanadium dioxide or vanadium dioxide doped with other atoms has a metal vanadium content. 61.45 wt% or more and 61.8 wt% or less, or the rate of increase in weight at 650 ° C. with respect to the weight at 200 ° C. in simultaneous differential thermal-thermogravimetric measurement is 9.45% or more and 9.95% or less, Preferably, the method is characterized in that it is higher than 9.5% and lower than 9.95%.

The vanadium dioxide or vanadium dioxide doped with other atoms preferably has a latent heat amount of 40 J / g or more, more preferably 42 J / g or more, and further preferably 45 J / g or more. By having such a large amount of latent heat, a large cooling effect can be exhibited with a smaller volume, which is advantageous in terms of downsizing. Here, “latent heat” is the total amount of thermal energy required when the phase of a substance changes, and in this specification, solid-solid phase transitions such as electrical, magnetic, and structural phase transitions are used. This refers to the amount of heat generated and absorbed.

The vanadium dioxide or vanadium dioxide doped with other atoms is preferably in the form of particles (powder). Average particle diameter of the core part of vanadium dioxide or vanadium dioxide doped with other atoms (D50: The particle size distribution is determined on a volume basis, and the cumulative value is 50% in the cumulative curve with the total volume being 100%. The particle size is not particularly limited, but is, for example, 0.1 to several hundred μm, specifically 0.1 to 900 μm, typically about 0.2 to 50 μm, and preferably 0.5 to 50 μm. The average particle diameter can be measured using a laser diffraction / scattering soot particle diameter / particle size distribution measuring apparatus or an electronic scanning microscope. The average particle diameter is preferably 0.2 μm or more from the viewpoint of ease of handling, and is preferably 50 μm or less from the viewpoint that it can be more densely molded.

The vanadium oxide or ceramic material of the present invention described above can be formed into a desired shape, for example, a sheet shape, a block shape, and other various shapes. The molding method is not particularly limited, and compression, sintering, or the like can be used. Moreover, you may mix and shape | mold with binders, such as resin or glass. Furthermore, it is good also as paste by mixing with resin etc. which have fluidity | liquidity.

As described above, the vanadium oxide or ceramic material of the present invention has a large latent heat, that is, a large endothermic amount, and an endothermic heat is generated quickly, so that it can be suitably used as a cooling device.

Therefore, the present invention also provides a cooling device comprising the vanadium oxide or ceramic material of the present invention described above.

The shape of the cooling device of the present invention is not particularly limited, and can be any shape.

In one aspect, the cooling device of the present invention may be block-shaped. By making it into a block shape, the whole volume becomes large and more heat can be absorbed. In another aspect, the cooling device of the present invention may be in the form of a sheet. By making it into a sheet shape, the surface area increases, so it becomes easy to release absorbed heat to the outside. Moreover, the shape which laminated | stacked powder with metal foil, a sheet | seat, etc., or the shape which wrapped was sufficient.

The cooling device of the present invention is installed in another member, for example, a protective cover for protecting the cooling device, a heat conductive part such as a metal for enhancing heat conductivity, an insulating sheet for ensuring insulation, and an electronic device. Members (for example, pressure-sensitive adhesive sheets, pins, nails, etc.) may be included.

The present invention also provides an electronic component having the cooling device of the present invention and an electronic apparatus having the cooling device or the electronic component.

The electronic component is not particularly limited, but for example, an integrated circuit (IC) such as a central processing unit (CPU), a power management IC (PMIC), a power amplifier (PA), a transceiver IC, and a voltage regulator (VR). , Light emitting diodes (LEDs), incandescent bulbs, semiconductor lasers and other light emitting elements, field effect transistors (FETs) and other heat source components, and other components such as lithium ion batteries, substrates, heat sinks, housings, etc. Examples include parts generally used in electronic equipment.

The electronic device is not particularly limited, and examples thereof include a mobile phone, a smartphone, a personal computer (PC), a tablet terminal, and a hard disk drive.

As mentioned above, although this invention was demonstrated, this invention is not limited to said aspect, A various modification | change can be performed.

Examples The following materials were prepared as starting materials.
・ Vanadium raw material Vanadium trioxide (V ₂ O ₃ ) with a purity of 99.8% or more
Vanadium pentoxide (V ₂ O ₅ ) with a purity of 99.9%
Vanadium dioxide (VO ₂ ) with a purity of 99.8% or more
・ Shifter tungsten oxide (WO ₃ ) for controlling the endothermic temperature
Tantalum oxide (Ta ₂ O ₅ )
Niobium oxide (Nb ₂ O ₅ )
Molybdenum oxide (MoO ₃ )

For vanadium dioxide (sample numbers 1 to 8), V ₂ O ₃ and V ₂ O ₅ were weighed at a mixing ratio of V ₂ O ₃ / V ₂ O ₅ = 25/25, and W, Mo as a shifter were used. For vanadium dioxide (sample numbers 9 to 22) to which Ta or Nb was added (dope), VO ₂ and shifter were weighed to a predetermined composition ratio. These raw materials were put in a polypot container together with partially stabilized zirconia (PSZ) balls, pure water, and a dispersant, and wet pulverized for 16 hours. Next, the mixed slurry was dried and sized.

Thereafter, heat treatment was performed while controlling the oxygen partial pressure in a water / hydrogen / nitrogen atmosphere. During heat treatment, the amount of water (water vapor) and nitrogen are constant during the treatment in the section above 150 ° C, and the oxygen partial pressure is sampled in the furnace gas and monitored with a zirconia oxygen partial pressure gauge to determine the amount of hydrogen as desired. The pressure was controlled to be a pressure. The temperature profile was 900 ° C. to 1000 ° C. at a rate of temperature increase of 300 K / hour, held for 2 hours, and decreased at a rate of 300 K / minute. Natural cooling was performed from 300 ° C. About the obtained sample, the crystal structure was analyzed by powder X-ray diffraction (XRD: X-ray Diffraction) measurement, and it confirmed that the target sample was obtained. However, only 5% of V ₂ O ₅ was present only in sample number 5. Detailed heat treatment conditions for sample numbers 1 to 22 are shown in Table 1 below. The numbers marked with * are comparative examples.

Further, samples were prepared by heat-treating the synthesized VO ₂ (sample number 4) at a temperature of 500 to 900 ° C. shown in Table 2 for 2 hours under the condition of N ₂ 20 L / min (sample numbers 23 to 27). The temperature of the reduction heat treatment for sample numbers 23 to 27 is shown in Table 2 below. The numbers marked with * are comparative examples.

Evaluation The characteristics of the vanadium oxide powder prepared above (vanadium dioxide and vanadium dioxide doped with each atom) were evaluated.

・ Differential scanning calorimetry (DSC: Differential scanning calorimetry; DSCQ2000 (manufactured by TA Instruments))
The DSC measurement was performed by sweeping the temperature from 0 ° C. to 100 ° C. and then to 0 ° C. at 10 K / min in a nitrogen atmosphere. From the DSC results, the endothermic amount absorbed at the time of temperature rise and the intensity ratio (exothermic / endothermic ratio) of the endothermic peak at the time of temperature rise and temperature drop were determined. Representatively, the results of sample numbers 1 to 3 are shown in FIGS. 1 to 3, respectively.

-Measurement of amount of metal vanadium (V metal) The amount of V metal of the prepared sample was measured by a titration method.
First, a sample was sampled, added to a sulfuric acid aqueous solution, heated on a hot plate at about 60 ° C. to be completely dissolved, and cooled to room temperature. Then, phosphoric acid was added, and ammonium iron (II) sulfate hexahydrate as a standard solution was added and stirred. From the resulting solution, a potassium permanganate standard solution was dropped, and the point where the color of the solution was reddish purple was the end point. From the aqueous solution in which VO ₂ was dissolved, the concentration of potassium permanganate, and titration The amount of V metal in the sample was quantified. This method is essentially based on the same measurement principle as that of a general method for quantifying the amount of V metal. Other reagents may be used as the reducing agent and oxidizing agent, and other procedures may be used as long as the amount of V metal can be determined from the change in the valence of vanadium by oxidation-reduction titration.

・ Differential heat-thermogravimetric simultaneous measurement (TG-DTA: Thermogravimetry / Differential Thermal Analysis; made by SEIKO)
In the TG-DTA measurement, the temperature was raised to 200 ° C. in the atmosphere, held there for 10 minutes, and after removing the influence of adsorbed water, thermogravimetric analysis was performed while heating to 700 ° C. at a rate of 10 K / min. . Based on the weight after holding at 200 ° C., the weight increase rate up to 650 ° C. was calculated.

The results of the above test are shown in Table 3 below. The numbers marked with * are comparative examples.

FIG. 4 shows the result of TG-DTA measurement of sample number 1. From FIG. 4, it was confirmed that the weight of vanadium oxide increased from about 400 ° C., and oxidation from VO ₂ to V ₂ O ₅ began. Then, it was confirmed that the increase in weight was saturated at about 600 ° C. and became V ₂ O ₅ completely.

From Table 3 and FIG. 5, Sample Nos. 1 to 3 were identified as VO ₂ by powder X-ray diffraction measurement, but it was confirmed that the oxidation behavior, the amount of weight increase (TG-DTA measurement), and the amount of V metal were different. It was.

Further, as apparent from Table 3 and FIGS. 1 to 3, sample numbers 1 to 3 were identified as VO ₂ by powder X-ray diffraction measurement, but each exhibited different DSC characteristics. Sample No. 1 has a sharp peak at the time of endothermic exotherm and an exothermic / endothermic peak ratio of 1.0. Sample No. 3 has a slightly lower peak height at the time of exotherm. The exothermic / endothermic peak ratio was 0.7. On the other hand, the sample of Sample No. 2 has a broad peak during heat release and an exothermic / endothermic peak ratio of 0.3, and it was confirmed that heat was released slowly.

From the above results, it was revealed that even in the sample identified as VO ₂ by powder X-ray diffraction measurement, the endothermic / exothermic characteristics differ significantly due to the difference in the amount of metal vanadium. Similarly, it was also clarified that the endothermic characteristics differ significantly depending on the difference in weight increase rate. This is considered to be because the ratio of V and O is deviated from 1: 2 of the stoichiometric amount of VO ₂ , and this deviation is considered to have a great influence on the heat absorption and heat generation characteristics.

As shown in Table 1, in the samples (sample numbers 1 to 8) prepared from the V ₂ O ₃ and V ₂ O ₅ raw materials under different heat treatment conditions, only the sample number 5 had an endotherm of less than 40 J / g. . Sample No. 5 has a weight increase rate of 10.1% and a V metal amount of 61.85%, which is outside the scope of the present invention, and about 5% of V ₂ O ₅ is detected from the XRD measurement. It is considered that the amount of endotherm was reduced because oxygen was synthesized under excessive heat treatment conditions. The samples Nos. 1 and 3 had an endotherm of 40 J / g or more, but the endothermic peak ratio was as high as 0.6 or more, and the exothermic peak was an endothermic peak as shown in FIGS. Similarly, it is steep. On the other hand, the sample of sample number 2 has a weight increase rate of 9.57% and a V metal amount of 61.7%, which is within the scope of the present invention. As shown in FIG. 2, this sample has a sharp endothermic peak but a gentle exothermic (heat dissipating) peak. The sample of sample number 2 was determined to be VO ₂ from the XRD measurement, but was in a state in which oxygen was deficient. Therefore, it is considered that the heat generation characteristics were broad. It was confirmed that Sample Nos. 2, 4 and 8 whose weight increase rate or V metal amount was within the range of the present invention provided a sufficiently large endothermic amount and ideal characteristics with a mild exothermic peak. It was done.

Further, from the results of sample numbers 9 to 22, the same results as in the case of VO ₂ were obtained in the samples to which W, Mo, Ta, or Nb was added as a temperature shifter. When the amount of W added was 1.5 at% or less, the endothermic amount exceeded 40 J / g, which was particularly good. On the other hand, Sample No. 9 in which the addition amount of W was 2.0 at% had a slightly low endotherm even when the weight increase rate and the V metal amount were within the range of the present invention. Similarly, when the addition amount of Mo, Nb and Ta was 10 at% or less, the endothermic amount exceeded 40 J / g, which was particularly favorable.

From the above results, it was confirmed that vanadium dioxide having desired characteristics or vanadium dioxide doped with other atoms can be obtained by using the V metal amount or the weight increase rate as an index.

Further, the samples obtained by heat treatment in the nitrogen atmosphere using the synthesized VO ₂ raw material (sample numbers 23 to 27), the amount of V metal decreases as the reduction temperature increases, in other words, in the sample. It was confirmed that the amount of oxygen increased. Similarly, the rate of increase in weight also increased as the reduction temperature increased. This is thought to be because the sample was oxidized due to the release of oxygen from the furnace material in a nitrogen atmosphere. Among the obtained samples, the sample of Sample No. 27 had a weight increase rate and a V metal amount outside the range of the present invention, a sharp exothermic peak, and a large endothermic peak ratio. Even from this result, even if it is set to VO ₂ from the XRD measurement, not all show the same endothermic characteristics, but it is managed using the weight increase rate or V metal amount index obtained from TG-DTA, It was confirmed that it was necessary to control.

The cooling device of the present invention can be used, for example, as a cooling device for a small communication terminal in which a thermal countermeasure problem has become remarkable.

Claims

Vanadium dioxide having a metal vanadium content of 61.45 wt% or more and 61.8 wt% or less, doped with other atoms or vanadium dioxide doped with other atoms:
Here, the other atom is an atom selected from the group consisting of W, Ta, Mo and Nb,
When the other atom is W, the content mole part of the other atom when the total of vanadium and the other atom is 100 mole parts is greater than 0 mole part and 1.5 mole parts or less,
When the other atom is Ta, Mo, or Nb, the content mole part of the other atom when the total of vanadium and the other atom is 100 mole parts is greater than 0 mole part and 10 mole parts or less.
Formula: V 1-x M x O 2
(Wherein M is W, Ta, Mo or Nb;
x is greater than or equal to 0,
When M is W, X is 0.015 or less,
When M is Ta, Mo or Nb, x is 0.1 or less. )
Vanadium dioxide represented by or vanadium dioxide doped with other atoms,
Vanadium dioxide or vanadium dioxide doped with other atoms, characterized in that the metal vanadium content is 61.45 wt% or more and 61.8 wt% or less.
The vanadium dioxide according to claim 2, wherein x is 0.
3. Vanadium dioxide doped with other atoms according to claim 2, characterized in that M is W.
5. A ceramic material containing vanadium dioxide according to any one of claims 1 to 4 and / or vanadium dioxide doped with other atoms.
The ceramic material according to claim 5, wherein the content of vanadium dioxide and vanadium dioxide doped with other atoms is 96 mass% or more.
A cooling device comprising the vanadium dioxide according to any one of claims 1 to 4 or vanadium dioxide doped with other atoms or the ceramic material according to claim 5 or 6.
An electronic component comprising the cooling device according to claim 7.
An electronic apparatus comprising the cooling device according to claim 7 or the electronic component according to claim 8.
A method for producing vanadium dioxide or vanadium dioxide doped with other atoms, wherein the vanadium dioxide and vanadium dioxide doped with other atoms has a metal vanadium content of 61.45 wt% or more and 61.8 wt% or less. A method characterized by that.
A method for controlling the endothermic or heat dissipation properties of vanadium dioxide or vanadium dioxide doped with other atoms, wherein the vanadium dioxide and vanadium dioxide doped with other atoms has a metal vanadium content of 61.45 wt% or more. . 8 wt% or less.