阅读说明：本技术 测温仪标定装置及使用该装置对测温仪标定的方法 (Thermodetector calibration device and method for calibrating thermodetector by using same ) 是由 吴长征 郭宇桥 吴俊驰 杨波 谢毅 于 2019-04-30 设计创作，主要内容包括：本发明提供了一种测温仪标定装置,所述测温仪标定装置包括：加热保温腔室：电阻测量仪；和置于所述加热保温腔室中的通过以下步骤制得的二氧化钒基单晶体：在流动惰性气体气氛中,将包含钒源的原料加热至950℃至1150℃之间的温度,并保持24小时至72小时,随后以不高于20℃/分钟的速度降温至室温,以得到二氧化钒基单晶体,其中,所述钒源是除钒之外不包含其他金属元素的含氧化合物,并且其中的钒为+4或+5价,氧与钒的摩尔比为2∶1以上,其中,所述电阻测量仪配置为用于测量所述二氧化钒基单晶体的电阻。该测温仪标定装置提供对测温仪的准确标定。本发明还提供一种使用该装置对对测温仪进行标定的方法。(The invention provides a thermodetector calibration device, which comprises: heating the heat preservation chamber: a resistance measuring instrument; and a vanadium dioxide-based single crystal disposed in the heating and holding chamber and produced by the steps of: heating a raw material containing a vanadium source to a temperature of 950 ℃ to 1150 ℃ in a flowing inert gas atmosphere for 24 hours to 72 hours, and then cooling to room temperature at a rate of not more than 20 ℃/minute to obtain a vanadium dioxide-based single crystal, wherein the vanadium source is an oxygen-containing compound containing no other metal element than vanadium, and wherein vanadium has a valence of +4 or +5, and the molar ratio of oxygen to vanadium is 2: 1 or more, wherein the resistance measuring instrument is configured to measure the resistance of the vanadium dioxide-based single crystal. The thermodetector calibration device provides accurate calibration for the thermodetector. The invention also provides a method for calibrating the temperature measuring instrument by using the device.)

1. A thermoscope calibration apparatus, comprising:

heating the heat preservation chamber:

a resistance measuring instrument; and

a vanadium dioxide-based single crystal placed in the heating and holding chamber and produced by the following steps:

heating a raw material containing a vanadium source to a temperature of 950 ℃ to 1150 ℃ for 24 to 72 hours in a flowing inert gas atmosphere, and then cooling to room temperature at a rate of not more than 20 ℃/min to obtain a vanadium dioxide-based single crystal, wherein the vanadium source is an oxygen-containing compound containing no other metal element than vanadium, and wherein vanadium has a valence of +4 or +5, and the molar ratio of oxygen to vanadium is 2: 1 or more,

Wherein the resistance measuring instrument is configured to measure the resistance of the vanadium dioxide-based single crystal.

2. The thermometer calibration device according to claim 1,

the source of vanadium is selected from the group consisting of: oxides of vanadium, oxygen-containing vanadium salts, vanadium oxyacid salts, and combinations thereof.

3. The thermometer calibration device according to claim 1,

the source of vanadium is selected from the group consisting of: vanadium pentoxide, ammonium metavanadate, vanadyl oxalate, vanadyl sulfate hydrate, vanadium ammonium sulfate, and combinations thereof.

4. The thermometer calibration device according to claim 1,

the feedstock comprising a source of vanadium is placed in a semi-open vessel.

5. The thermometer calibration device according to claim 1,

the semi-open container is a single-opening pipe which is positioned in a horizontal inert gas flow and is obliquely placed, the pipe orifice of the single-opening pipe is higher than the pipe bottom, and the included angle between the length direction and the horizontal plane is 5-35 degrees.

6. The thermometer calibration device according to claim 1,

the flowing inert gas atmosphere comprises convection of an inert gas.

7. The thermometer calibration device according to claim 1,

The inert gas is selected from the group consisting of: nitrogen, argon, and combinations thereof.

8. The method of claim 1, wherein,

the feedstock also includes a source of a doping element.

9. The thermometer calibration device according to claim 1,

the vanadium dioxide-based single crystal is a rod-like single crystal having a length of 1 mm or more and a diameter of 100 μm or more.

10. The thermometer calibration device according to claim 1,

the insulator-metal phase transition temperature difference of the vanadium dioxide-based single crystal is below 0.05K, wherein the resistivity of the insulating phase is 10 of that of the metal phase⁵The above.

11. A method of calibrating a thermometer using the thermometer calibration device of claim 1, the method comprising:

placing a detection part of a thermometer to be calibrated and a vanadium dioxide-based single crystal in the heating and heat-preserving chamber;

measuring the resistance of the vanadium dioxide-based single crystal by using the resistance measuring instrument while changing the temperature of the heating and heat-preserving chamber;

and when the resistance suddenly changes, reading the temperature measured by the thermometer to be calibrated, and comparing the temperature with the insulator-metal phase transition temperature of the vanadium dioxide-based single crystal.

Technical Field

The invention relates to the field of insulator-metal phase change materials, in particular to a temperature measuring instrument calibration device and a method for calibrating a temperature measuring instrument by using the same.

Background

The solid-solid phase change of a substance under the condition of variable temperature does not depend on air pressure generally, is accompanied by obvious physical quantity mutation, and can be used as an ideal fixed point for temperature calibration. The vanadium oxide compound is an important strongly-associated material, and the crystal structure, the electronic structure and the spin structure of the vanadium oxide compound can be changed strongly at a specific temperature to generate an agile response to a specific condition. Vanadium dioxide is a special vanadium-oxygen compound, can generate insulator-metal phase transition in a range near 340K, has huge difference of two-phase resistance, is quick in response, and has huge potential for temperature calibration.

However, currently available vanadium dioxide materials are mainly titanium dioxide or sapphire substrates on which vanadium dioxide thin films are grown. In the growth process, the vanadium dioxide epitaxial film is limited by conditions such as harsh oxygen partial pressure, growth temperature and the like, the vanadium dioxide epitaxial film is difficult to produce in large quantity, meanwhile, the vanadium dioxide epitaxial film grown on the substrate is usually a polycrystalline film, the insulator-metal phase change process of the vanadium dioxide epitaxial film can be realized only by wide temperature change, namely, the width of the thermal hysteresis loop is widened, and the vanadium dioxide epitaxial film is not suitable for quick and sensitive temperature induction. In addition, internal stress is easily generated in the thin film, resulting in a large temperature deviation of the insulator-metal phase transition. Therefore, the preparation of large-size high-quality single crystals is an important condition for realizing the practical application of vanadium dioxide.

Disclosure of Invention

In one aspect, the present invention provides a thermometer calibration device, comprising:

heating the heat preservation chamber:

a resistance measuring instrument; and

a vanadium dioxide-based single crystal placed in the heating and holding chamber and produced by the following steps:

heating a raw material containing a vanadium source to a temperature of 950 ℃ to 1150 ℃ for 24 to 72 hours in a flowing inert gas atmosphere, and then cooling to room temperature at a rate of not more than 20 ℃/min to obtain a vanadium dioxide-based single crystal, wherein the vanadium source is an oxygen-containing compound containing no other metal element than vanadium, and wherein vanadium has a valence of +4 or +5, and the molar ratio of oxygen to vanadium is 2: 1 or more,

wherein the resistance measuring instrument is configured to measure the resistance of the vanadium dioxide-based single crystal.

Preferably, the source of vanadium is selected from the group consisting of: oxides of vanadium, oxygen-containing vanadium salts, vanadium oxyacid salts, and combinations thereof.

Preferably, the source of vanadium is selected from the group consisting of: vanadium pentoxide, ammonium metavanadate, vanadyl oxalate, vanadyl sulfate hydrate, vanadium ammonium sulfate, and combinations thereof.

Preferably, the source comprising vanadium is placed in a semi-open vessel.

Preferably, the semi-open container is a single-opening pipe which is positioned in a horizontal inert gas flow and is obliquely placed, the single-opening pipe is arranged in a way that a pipe orifice is higher than the bottom of the pipe, and the included angle between the length direction and the horizontal plane is 5-35 degrees. More preferably, the length direction of the single-opening tube forms an angle of 20 to 30 ° with the horizontal plane.

Preferably, the flowing inert gas atmosphere comprises convection of an inert gas.

Preferably, the inert gas is selected from the group consisting of: nitrogen, argon, and combinations thereof.

Optionally, the feedstock further comprises a source of a doping element.

Preferably, the vanadium dioxide-based single crystal is a rod-shaped single crystal having a length of 1 mm or more and a diameter of 100 μm or more.

Preferably, the insulator-metal phase transition temperature difference of the vanadium dioxide-based single crystal is below 0.05K, wherein the resistivity of the insulating phase is 10 of that of the metal phase⁵More than twice.

In another aspect, the present invention provides a method for calibrating a thermometer by using the above thermometer calibration device, the method including:

placing the detection part of the thermometer to be calibrated in the heating and heat-preserving chamber;

Measuring the resistance of the vanadium dioxide-based single crystal by using the resistance measuring instrument while changing the temperature of the heating and heat-preserving chamber;

and when the resistance suddenly changes, reading the temperature measured by the thermometer to be calibrated, and comparing the temperature with the insulator-metal phase transition temperature of the vanadium dioxide-based single crystal.

Drawings

In order to more fully illustrate the invention, reference will now be made to the accompanying drawings, which are to be used in either an embodiment or a prior art description, and it is to be noted that the following description of the drawings is only a partial illustration of the invention, and that other drawings may be derived from the drawings provided by those skilled in the art without the benefit of the inventive faculty.

Fig. 1 shows temperature-change resistance data of a vanadium dioxide single crystal according to an embodiment of the present invention.

Fig. 2 is a schematic diagram of a high-precision temperature calibration apparatus according to an embodiment of the present invention.

FIG. 3 is a flow diagram of method steps for one embodiment of the present invention.

Fig. 4 is a schematic diagram of the arrangement of the apparatus in one embodiment of the invention.

Detailed description of the preferred embodiments

The invention provides a temperature measuring instrument calibration device which can be used for accurately indicating the insulator-metal phase transition temperature of a vanadium dioxide single crystal.

The invention provides a thermodetector calibration device, which comprises:

heating the heat preservation chamber:

a resistance measuring instrument; and

a vanadium dioxide-based single crystal placed in the heating and holding chamber and produced by the following steps:

heating a raw material containing a vanadium source to a temperature of 950 ℃ to 1150 ℃ for 24 to 72 hours in a flowing inert gas atmosphere, and then cooling to room temperature at a rate of not more than 20 ℃/min to obtain a vanadium dioxide-based single crystal, wherein the vanadium source is an oxygen-containing compound containing no other metal element than vanadium, and wherein vanadium has a valence of +4 or +5, and the molar ratio of oxygen to vanadium is 2: 1 or more,

wherein the resistance measuring instrument is configured to measure the resistance of the vanadium dioxide-based single crystal.

The large-size vanadium dioxide-based single crystal prepared by a specific method is used in the calibrating device of the thermodetector. The method comprises heating a raw material containing a vanadium source to a temperature of 950 ℃ to 1150 ℃ for 24 hours to 72 hours in a flowing inert gas atmosphere, and then cooling to room temperature at a rate of not more than 20 ℃/min to obtain a vanadium dioxide-based single crystal,

Wherein the vanadium source is an oxygen-containing compound containing no other metal element than vanadium, and wherein vanadium has a valence of +4 or +5, and the molar ratio of oxygen to vanadium is 2: 1 or more.

By this method, a large-sized vanadium dioxide-based single crystal in a non-thin film form can be prepared for use as a standard for temperature calibration.

The vanadium dioxide-based single crystal has an insulator-metal phase transition and a narrow phase transition temperature difference. The resistance change can reach 10 in the temperature range of 0.05K before and after phase change, namely tetragonal rutile phase vanadium dioxide in a metal state above 340K and monoclinic phase vanadium dioxide in an insulator state below 340K⁵And meanwhile, the temperature of the phase change point of the material can be repeated, and the material is not influenced by an external magnetic field, an electric field and air pressure and can be used as a calibration point of a high-precision temperature sensor.

The vanadium dioxide-based single crystal is produced by heating a raw material containing a vanadium source at a high temperature for a long time in a flowing inert gas atmosphere. The vanadium dioxide-based single crystal is not in the form of a thin film and can have a maximum dimension of the order of millimeters.

In order to produce a high-purity vanadium dioxide-based single crystal, the vanadium source of the present invention is an oxygen-containing compound containing no other metal element than vanadium, and wherein vanadium has a valence of +4 or +5 and the molar ratio of oxygen to vanadium is 2: 1 or more. Without being bound to any theory, the principle of such a vanadium source to form a vanadium dioxide-based single crystal is as follows: during heating, the vanadium source in the raw material decomposes vanadium and oxygen, producing vanadium-oxygen compounds. The stable phase of the vanadium oxide compound under the high-temperature oxygen-deficient condition is vanadium dioxide. Therefore, a vanadium dioxide phase can be generated through vanadium source decomposition, meanwhile, the vanadium dioxide phase can generate solid-gas conversion at high temperature, and in a growth container, continuous inert convection airflow can drive the volatilization-deposition growth process of vanadium dioxide gaseous substances, so that large-size high-quality vanadium dioxide single crystals can be obtained. The atmosphere of the vanadium dioxide-based single crystal preparation method is oxygen-deficient, so if a low-valence vanadium source is selected, further oxidation under oxygen-deficient conditions cannot be carried out to form vanadium dioxide species. In addition, if the molar ratio of oxygen to vanadium is less than 2: 1 per mole, the formation of a vanadium dioxide single crystal is also unfavorable. Alternatively, the molar ratio of oxygen to vanadium per mole may be 2: 1, 3: 1, 4: 1, etc. The excess oxygen in the vanadium source, as well as non-metallic elements other than oxygen (e.g., N, S, C, H, etc.), does not adversely affect the crystals of vanadium dioxide under flowing inert gas atmosphere conditions.

From the viewpoint of easy decomposition of the vanadium source, the vanadium source is preferably selected from the group consisting of: oxides of vanadium, oxygen-containing vanadium salts, vanadium oxyacid salts, and combinations thereof. Preferably, the source of vanadium is selected from the group consisting of: vanadium pentoxide, ammonium metavanadate, vanadyl oxalate, vanadyl sulfate hydrate, vanadium ammonium sulfate, and combinations thereof. Still more preferably, the source of vanadium is selected from the group consisting of: vanadium pentoxide, ammonium metavanadate, vanadyl oxalate, and combinations thereof.

The vanadium source is typically in powder form, but may be in other forms. The invention has no special requirement on the granularity of the vanadium source.

The raw material containing a vanadium source may contain only a vanadium source, or may contain a source of a doping element other than a vanadium source. When the source of the doping element is contained, the doping element is doped in the vanadium dioxide single crystal, the whole crystal structure of the vanadium dioxide single crystal is not influenced, and the obvious adjustment effect on the phase transition temperature of the insulator-metal is generated.

The source of doping elements may be selected from the group consisting of: a molybdenum source, a tungsten source, a titanium source, an aluminum source, a niobium source, a chromium source, and combinations thereof. These doping element sources can also generally be in powder form and homogeneously mixed with the vanadium source in powder form. The mass ratio of the source of doping element to the source of vanadium may be in the range 0.01: 10 to 1: 10, for example 0.5: 10. The doping element source is generally an oxygen-containing compound containing no other metal element than the doping element or a salt that is easily decomposed into an oxygen-containing compound. For example, molybdenum trioxide or ammonium molybdate may be used as the molybdenum source.

After the raw materials are placed, the vanadium source is heated to a temperature between 950 ℃ and 1150 ℃ in a flowing inert gas atmosphere for 24 hours to 72 hours, and then cooled to room temperature at a speed of not more than 20 ℃/minute to obtain a vanadium dioxide-based single crystal.

The inert gas is a gas that does not react with the starting materials and products. The inert gas is flowing. Which is used to carry away gases generated or volatilized from the raw materials during the reaction and as a carrier gas for the gas phase transport of vanadium dioxide. The inert gas used in common use may be one or more of nitrogen, argon, helium, and the like. Preferably, the inert gas is selected from the group consisting of: nitrogen, argon, and combinations thereof. In the method for producing a vanadium dioxide-based single crystal, the flowing inert gas atmosphere preferably includes convection of an inert gas. Under the environment including convection, the growth of vanadium dioxide crystals is more facilitated. The vanadium dioxide-based single crystal preparation method does not particularly specify the flow rate of the inert gas.

Heating the sample to a temperature of 950-1150 ℃ under a flowing inert gas atmosphere for 24-72 hours, and then cooling to room temperature at a speed of not more than 20 ℃/min to obtain a vanadium dioxide-based single crystal.

The influence of the temperature rise process on the product of the invention is not obvious. Typically, the temperature may be increased at a ramp rate of, for example, 10 deg.C/minute.

The holding temperature and time are critical to the preparation method of the vanadium dioxide-based single crystal. The temperature needs to be between 950 ℃ and 1150 ℃, preferably between 1000 ℃ and 1150 ℃. If the temperature is too low, large-sized high-quality single crystals cannot be formed, and even vanadium dioxide phases cannot be formed. If the temperature is too high, oxygen vacancies tend to be generated in the vanadium dioxide material, and the vanadium dioxide phase is decomposed at a higher temperature, so that the vanadium dioxide-based single crystal cannot be obtained. The incubation time is required to be 24 to 72 hours, preferably 48 to 60 hours. If the time is too short, the single crystal size is small and even only a granular powder is obtained. If the time is too long, the vanadium dioxide-based single crystal is difficult to grow continuously.

And after the heat preservation is finished, cooling to room temperature at the speed of not higher than 20 ℃/min. If the temperature reduction speed is too fast, residual stress is introduced into the vanadium dioxide-based single crystal, so that the quality of the single crystal is reduced. Preferably, the cooling rate is more than 5 ℃/minute so as not to take too long.

In the above manner, a large-sized vanadium dioxide-based single crystal can be formed in a specific temperature range by the synergistic effect of the thermal decomposition of the raw material containing a vanadium source and an optional doping element source and the inert gas flow on the transport of oxygen and vanadium atoms.

Preferably, the source comprising the vanadium source is placed in a semi-open vessel. Placing the raw materials in a semi-open container is beneficial to preventing inert gas flow from blowing away raw material powder and is also beneficial to providing a better microenvironment for single crystal growth. A semi-open container refers to a container having only one opening. A typical example of a semi-open container is a single-opening tube. The gas flows into the container through the opening and flows out through the opening again, and a stable convection atmosphere is formed in the container. The raw material powder is not carried out of the semi-open container by the gas flow and the deposition growth is carried out under the convection gas flow in the container.

When the raw materials are melted at the heating temperature of the process, the melted raw materials are prevented from flowing and spreading in the vessel. For example, when the vessel is a single-port tube and is positioned in a horizontal inert gas flow, if it is positioned horizontally or diagonally downward (the nozzle is below the bottom of the tube), the molten feedstock will tend to spread out and even flow out of the nozzle. A single-opening tube, also referred to herein as a sample tube, is a tube similar to a test tube, having a tube body of uniform thickness and a tube mouth and a tube bottom at both ends, respectively. At this time, the single-opening tube should be placed obliquely so that the opening is higher than the bottom of the tube, thereby collecting the molten raw material at the bottom of the tube. Meanwhile, in order to realize the gas phase convection growth in the reaction system, the inclination angle is not too large, otherwise, inert gas flow is difficult to enter a single-opening tube, only vanadium dioxide-based particles generated by the decomposition of a vanadium source can be obtained, and the growth of large-size single crystals cannot be carried out. Preferably, the angle between the length direction and the horizontal plane is 5 to 35 °. More preferably, the angle between the length direction and the horizontal plane is between 20 ° and 30 °. Preferably, the single-ported tube is positioned with its vertical plane parallel to the direction of the external inert gas flow, with its ports facing substantially in the upstream direction of the external inert gas flow.

The semi-open vessel may be otherwise provided so long as it is satisfied that the raw materials in the semi-open vessel may be in a flowing inert gas atmosphere including convection. When the raw material is melted in the temperature range of the present invention, the inclination angle of the semi-open vessel is set to avoid the melted raw material from spreading or flowing out of the vessel.

Since the vanadium dioxide-based single crystal is produced in a flowing inert gas atmosphere and the starting materials are generally in powder form, loading the starting materials into the tube provides a better semi-enclosed space, better in terms of convective circulation of the gaseous vanadium oxygen species within the space. In addition, the use of a single open tube to hold the material also utilizes the feeding of the material into the heating device and the removal of the product from the heating device. When a single-opening tube is used, the raw material may be put into the tube, and then the tube may be placed in a heating device such as an annealing furnace in which an inert gas flow is horizontally passed, with the tube opening directed obliquely upward.

The sample tube can be a round or square tube. The material of the sample tube can be selected from one or more of quartz glass, corundum and graphite. The inner diameter of the device can be 0.5-2 cm, and the length of the device can be 5-20 cm. Preferably, the material of the sample tube is selected from one or more of quartz glass and corundum, the inner diameter is 0.8-1.2 cm, and the length is 8-12 cm. More preferably, the inner diameter is 0.9-1.1 cm, and the length is 9-11 cm.

In the method for producing a vanadium dioxide-based single crystal, the mass of the vanadium source compound may be 50 to 1000mg, preferably 200 to 600mg, and more preferably 300 to 400mg, from the viewpoint of the size of the single crystal product to be obtained.

When a semi-open container is used to provide the inclined surface, the semi-open container may be placed in an annealing furnace and an inert gas is passed through the annealing furnace. In other words, the whole of the semi-open container is in an external flowing inert gas atmosphere. The opening of the semi-open vessel is preferably directed substantially upstream of the flow of inert gas to the exterior so that the inert gas readily flows into the semi-open vessel and forms a convective atmosphere within the vessel that facilitates the growth of the single crystal of vanadium dioxide. The direction of the external inert gas flow may be inclined or horizontal as long as it can flow into the semi-open container. The direction of the external inert gas flow is preferably horizontal in view of the arrangement of the cavity of a typical heater such as an oven.

The large-size vanadium dioxide-based single crystal can be prepared by the preparation method of the vanadium dioxide-based single crystal. The large-sized vanadium dioxide-based single crystal may be a rod-shaped single crystal having a length of 1 mm or more. The maximum length can be as much as 6 mm or more. The rod-shaped single crystal may have a diameter of several hundred micrometers. Such size and shape facilitates its further fabrication into the desired device.

In particular, the insulator-metal phase transition temperature difference of the vanadium dioxide-based single crystal can reach below 0.05K. The insulator-metal phase transition temperature difference described herein refers to the temperature difference experienced to complete the transition from the fully insulator phase to the fully metal phase (tetragonal rutile phase). At this time, the resistivity of the insulating phase should be 10 of that of the metal phase⁵More than twice. The phase transition temperature during the warming and cooling process may have a hysteresis greater than 1K

The vanadium dioxide-based single crystal has large size and high quality, and is suitable for accurate temperature calibration. The preparation method is simple and cheap, and the flow is simple and easy to operate, so that the method has great application value.

The calibrating device of the thermodetector comprises:

heating the heat preservation chamber:

a resistance measuring instrument; and

the vanadium dioxide-based single crystal prepared by the method is placed in the heating and heat-preserving chamber:

wherein the resistance measuring instrument is configured to measure the resistance of the vanadium dioxide-based single crystal.

The heating and heat-preserving chamber is an insulating chamber having heating and cooling functions, and the rate of temperature rise or fall can be controlled. The heating and heat-preserving chamber can also contain a detection part of a thermometer to be calibrated. In other words, the thermometer to be calibrated may measure the temperature within the heating and incubation chamber.

The vanadium dioxide-based single crystal is placed in a heating and heat-preserving chamber, so that the temperature changes along with the temperature in the chamber.

The resistance measuring instrument is used for measuring the resistance of the vanadium dioxide-based single crystal. When the vanadium dioxide based single crystal has insulator-metal phase transition, the resistance measuring instrument will measure 10⁵The resistance of the fold changes abruptly. When the abrupt change is observed, the temperature of the heating and heat-preserving chamber is known to just reach the insulator-metal phase transition temperature. The temperature is consistent over multiple measurements.

Preferably, the vanadium dioxide-based single crystal used in the thermometric calibration apparatus is a rod-like single crystal having a length of 1 mm or more and a diameter of 100 μm or more. Such a large-sized single crystal is convenient to install and use, and is excellent in crystallinity, and can provide an accurate response to temperature.

Preferably, the insulator-metal phase transition temperature difference of the vanadium dioxide-based single crystal is below 0.05K, wherein the resistivity of the insulating phase is 10 of that of the metal phase⁵The above. Such small phase change temperature differences and large resistivity variations ensure accurate calibration of the temperature.

The invention also provides a method for calibrating the thermodetector by using the thermodetector calibration device, which comprises the following steps:

Placing a detection part of a thermometer to be calibrated and a vanadium dioxide-based single crystal in the heating and heat-preserving chamber, and keeping the detection part and the vanadium dioxide-based single crystal to have similar temperature conditions;

measuring the resistance of the vanadium dioxide-based single crystal by using the resistance measuring instrument while changing the temperature of the heating and heat-preserving chamber;

and when the resistance of the vanadium dioxide-based single crystal suddenly changes, reading the temperature measured by the thermometer to be calibrated, and comparing the temperature with the sudden change temperature of the resistance of the vanadium dioxide-based single crystal.

The temperature change of the heating and heat-preserving chamber can be a heating process or a cooling process. When the temperature is close to the phase transition temperature of the insulator-metal, the temperature change rate should be slowed to be within 0.1K/min so as to ensure the measurement precision.

If the temperature measured by the thermodetector is exactly the insulator-metal phase transition temperature, the thermodetector is proved to be accurate at the temperature. If the temperature measured by the thermodetector is not the insulator-metal phase transition temperature, the thermodetector is proved to be inaccurate at the temperature. At this point, the thermometer may be calibrated, adjusted, and the method of the invention repeated to perform calibration again until it is accurate.

The invention is illustrated by the following more detailed description.

A method for producing a vanadium dioxide-based single crystal according to an embodiment of the present invention includes the steps of:

a) adding vanadium source powder into the sample tube;

the sample tube is a round or square sample tube with a single opening, the material of the sample tube is selected from one or more of quartz glass, corundum and graphite, the inner diameter is 0.5-2 cm, and the length is 5-20 cm; the preferred conditions are: the sample tube is made of one or more of quartz glass and corundum, the inner diameter is 0.8-1.2 cm, and the length is 8-12 cm; more preferred conditions are: the inner diameter is 0.9-1.1 cm, and the length is 9-11 cm.

The vanadium source compound is selected from one or more of vanadium pentoxide, vanadium acetylacetonate, ammonium metavanadate, vanadyl oxalate, vanadyl sulfate hydrate and vanadium ammonium sulfate, preferably one or more of vanadium pentoxide, ammonium metavanadate, vanadyl oxalate, vanadyl sulfate hydrate and vanadium ammonium sulfate, and more preferably one or more of vanadium pentoxide, ammonium metavanadate and vanadyl oxalate.

The mass of the vanadium source compound is 50-1000 mg, preferably 200-600 mg, and more preferably 300-400 mg.

b) Placing the sample tube in a sample chamber of a tubular annealing furnace with a gas washing device, introducing inert gas to remove oxygen, and then maintaining the inert gas flow at a constant flow rate;

The sample tube is placed in the sample chamber in an inclined mode, the opening faces upwards and faces to the upstream of the airflow, and the tangential angle is 5-35 degrees, and preferably 20-30 degrees.

The sample chamber of the tubular annealing furnace with the gas washing device is selected from one or more of sample chambers with round shapes, square shapes and the like and two open ends.

The tubular annealing furnace sample chamber with the gas washing device is provided with a lining, and the lining is made of one or more materials selected from quartz glass, corundum and graphite; preferably one or more of quartz glass and corundum;

the gas washing process can be realized by vacuumizing and filling inert gas or continuously introducing the inert gas for flushing.

The inert gas is one or more selected from nitrogen, argon and helium; preferably one or more of nitrogen and argon inert gases.

The flow rate is 20 sccm-500 sccm, and the specific preferred value is selected according to the size of the sample chamber.

c) And setting a muffle furnace temperature control program, keeping the temperature of the muffle furnace at a high temperature for a certain time, cooling the muffle furnace, and finally collecting a single crystal sample from the sample tube.

The sample chamber of the tubular annealing furnace with the gas washing device is placed horizontally.

The high temperature is 950 ℃ to 1150 ℃, preferably 1000 ℃ to 1150 ℃.

The certain time is 24 to 72 hours, and preferably 48 to 60 hours.

The cooling rate is not higher than 20 ℃/min.

On the basis, a high-precision temperature calibration device is prepared:

putting the reference unit connected with the vanadium dioxide single crystal in series into a heat preservation testing cavity (namely a heating heat preservation cavity);

and connecting the heat preservation test cavity with a sensor to be calibrated, a temperature reading component (namely a thermometer to be calibrated) and a heating and control module.

The temperature reference unit is a vanadium dioxide single crystal connected in series and a basic circuit used for measuring the resistance value of the vanadium dioxide single crystal in real time.

The heat-preservation test cavity is mainly used for integrating the reference unit and the temperature sensing assembly to be calibrated together and ensuring that the sensor to be calibrated and the vanadium dioxide single crystal are always in the same temperature state in the calibrating and calibrating processes.

The high-precision temperature calibration method comprises the following steps:

a. connecting a temperature sensor to be calibrated with a temperature reading unit, placing a reference unit of the vanadium dioxide single crystal and the temperature sensor to be calibrated into a test cavity, controlling a heating unit, slowly heating the temperature of the test cavity, and ensuring the temperature in the test cavity to be fully balanced;

b. when the temperature is heated to the phase transition temperature of the vanadium dioxide, the resistance of the reference circuit connected with the vanadium dioxide single crystal in series is measured to be rapidly reduced, and the temperature display of the high-precision temperature sensor to be calibrated is read;

c. And obtaining calibration data according to the reading value, and calibrating the sensor.

In the step a, the heating device is positioned in the middle of the test cavity, and the reference unit vanadium dioxide single crystal and the temperature sensor to be calibrated are equidistantly placed on two sides of the heating device, so that the two are ensured to have similar temperature conditions. When the heating device is heated to the temperature before the phase transition point of the vanadium dioxide single crystal, the temperature rise rate needs to be slowed down to be within 0.1K/min.

In the step c, the phase change hysteresis effect in the heating and cooling processes of the vanadium dioxide is utilized, the hysteresis temperature is constant, and the temperature comparison is carried out in one temperature cycle (the heating and cooling processes).

While the preferred embodiments of the present invention will now be described in conjunction with the following examples, it is to be understood that these descriptions are merely illustrative of the features and advantages of the present invention, and are not intended to limit the scope of the appended claims. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.