KR20150031128A - Process for preparing co-doped vanadium dioxide with transition materials by molten method - Google Patents

Abstract

The present invention relates to a method for preparing vanadium dioxide particles co-doped with 2 or more transition elements. The present invention provides the method for preparing vanadium dioxide having a phase transition effect which comprises: a mixing step which evenly mixes predetermined amount of vanadate with transition elements used for co-doping; a molten step which melts the mixed powder in a furnace at high temperatures; a quick freezing step which takes out the compound from the furnace and quick freezes the compound; a plasticizing step for removing absorbed moisture; a reduction step which reduces using ammonia and nitrogen gas; and a heat treating step which heat treats and stabilizes the reduced powder. The method for preparing vanadium dioxide co-doped with transition elements according to the present invention reduces transition temperature down to room temperature and can prepare stabilized vanadium dioxide powder using a general process. The prepared powder can be easily applied to a film for heat transition after being dispersed. Also the vanadium dioxide fine particles co-doped with transition elements can selectively transmit and reflect infrared ray according to temperature, thereby being able to be applied to glasses of buildings and and vehicles and highly reducing energy.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for producing vanadium dioxide in which a transition element is co-doped using a melting method,

The present invention relates to a process for preparing vanadium dioxide in which a transition metal is co-doped, and more particularly to a process for preparing a transition metal co-doped vanadium dioxide having a good phase transition effect by using a melting method.

Recently, it is important to control energy consumption as the prices of chemical energy sources such as petroleum surge. In fact, more than 60% of household energy consumption is used for heating and cooling, and 45% of energy is lost through windows in general houses and buildings.

Various methods have been attempted to reduce the energy consumed through windows. Typically, various efforts are made to save energy from the method of adjusting the window size to the method of installing the high insulating windowpane.

 Especially, thermochromic glass which controls the energy inflow through visible light transmittance by coating a thermochromic material, which has a phase transition at a constant temperature, on a glass is studied. Such a thermochromic glass is called a 'smart window' that can control light transmittance and reflectance freely.

The representative material of the thermochromic glass is vanadium dioxide, which is one of various forms of vanadium oxide. The vanadium dioxide is thermochromic, which is a characteristic that the light transmittance and reflectivity in the infrared region are greatly changed based on the phase transition temperature of 68 캜 .

The vanadium dioxide with thermochromic characteristics has a monoclinic structure below the transition temperature and a tetragonal rutile structure above the transition temperature. The electrical and optical properties of the vanadium dioxide depend on the microstructure of the coating layer and the lattice strain, and the transition temperature, which depends on the lattice strain, The hysteresis width, and the resistivity difference.

Generally, as a method for producing vanadium dioxide particles, it is known that vanadium pentoxide (V ₂ O ₅ ) is converted into vanadium hydrate form through hydrothermal synthesis or sol-gel to obtain vanadium dioxide particles have. However, in such a case, a large amount of solvent used in the reaction and a long reaction time in crystallization are required to obtain a high yield of vanadium dioxide. Also, it takes a lot of time to find the optimization of the physical synthesis parameters, and there is a problem that the initial process installation cost incurred in mass production is expensive.

On the other hand, after the reaction using the reducing agents, the vanadium dioxide vanadium (V ₂ O ₅ ), vanadyl chloride (VOCl ₂ ) and vanadium sulfate (VOSO ₄ ) precursors are pyrolyzed at a high temperature Followed by melting. In the case of using a reducing agent, a reducing agent is relatively excessively used in the process of producing vanadium dioxide using a precursor, which is disadvantageous in that it is economically costly.

Therefore, a study on the development of a ceramic particle manufacturing process which can minimize the initial process installation cost and cost increase due to the use of expensive tungsten or reducing agent, which can be made at the time of mass production, need.

The present invention provides a method for producing vanadium dioxide which is co-doped with a transition metal having a smaller particle size and crystallinity and a high phase transformation efficiency while reducing the cost and environmental burden by using a molten process do.

In addition, the present invention is intended to provide co-doped vanadium dioxide of at least two transition metals prepared according to the above process.

The present invention relates to a process for producing a vanadium salt, which comprises homogeneously mixing a vanadium salt and two or more transition metal compounds, and then molten at a temperature of 700 ° C to 1,000 ° C; After the molten compound is quenched, removing moisture through a firing process; Reducing the calcined compound with ammonia and nitrogen gas; And heat treating the reduced compound at a temperature of 500 ° C to 800 ° C; Wherein the vanadium salt and the transition metal compound are reacted such that the content of the transition metal element is 0.01 at% to 5.5 at% based on the total of the vanadium element and the transition metal element, .

The present invention also provides vanadium dioxide doped with a transition metal prepared according to the method.

Hereinafter, a method for producing a co-doped vanadium dioxide according to a specific embodiment of the present invention and a transition metal co-doped vanadium prepared from the vanadium dioxide will be described in detail. It is to be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

&Quot; Including "or" containing ", unless the context clearly dictates otherwise throughout the specification, refers to any element (or component) including without limitation, excluding the addition of another component .

In the present invention, the vanadium salt and the transition metal used for co-doping are uniformly mixed to mix the starting powder, the molten mixture is molten at a high temperature in the furnace, the compound is taken out from the furnace A step of quenching the distilled water, a step of firing to remove the moisture absorbed, a step of reducing the powder by ammonia and nitrogen gas, and a step of heat treatment in which the reduced powder particles are heat- It is possible to effectively manufacture a metal-co-doped vanadium dioxide fine particle.

In particular, in the conventional method, there is a problem that an excessive amount of a reducing agent is used to increase an economical cost. Accordingly, the present invention is characterized in that transition metal co-doped vanadium dioxide having excellent phase transition effect is produced using a melting method. In the case of applying the melting method as in the present invention, vanadium dioxide can be produced by charging the mixed powder into a crucible, charging the furnace into the furnace, holding the temperature of the furnace at a temperature higher than the melting point, melting the vanadium salt powder and pyrolyzing. This method is economically superior because it uses less solvent than other production methods. In addition, since the powder is melted at a temperature higher than the melting point at a time by mixing the doping material and the precursor all at once without special control device, the manufacturing is easy.

In general, when vanadium dioxide having thermochromic characteristics is doped with at least one transition metal having a high valence such as tungsten (W), molybdenum (Mo), or niobium (Nb), the doped material (impurity) The transition temperature can also be controlled by adjusting the amount of the impurity introduced between the lattice structure of the substrate and the phase transition temperature to a temperature close to room temperature. In addition, in the case of tungsten among the transition metals, when the tungsten and the other transition metal are co-doped, the two elements act independently of each other, so that the phase transition temperature can be finely adjusted and the phase transition temperature It is easy to get off. In addition, the economic burden of the ceramic particle manufacturing process can be reduced by reducing the amount of expensive tungsten used.

In one embodiment of the present invention, the present invention provides a method for producing vanadium dioxide in which a transition metal having excellent dispersion and thermoelectric properties is co-doped through a melting process. The method for producing vanadium dioxide in which the transition metal is co-doped includes the steps of uniformly mixing a vanadium salt and two or more transition metal compounds, and then molten at a temperature of 700 ° C to 1,000 ° C; After the molten compound is quenched, removing moisture through a firing process; Reducing the calcined compound with ammonia and nitrogen gas; And heat treating the reduced compound at a temperature of 500 ° C to 800 ° C.

In particular, the method for producing vanadium dioxide doped with a transition metal according to the present invention is characterized in that the vanadium salt and the transition metal compound have a transition metal element content of 0.01 at% to 5.5 at% based on the total of the vanadium element and the transition metal element, The reaction can be carried out at 0.1 at% to 5.3 at%, more preferably at 0.5 at% to 5.2 at%. Here, when the content of the transition metal compound is less than 0.01 at%, the effect of lowering the transition temperature of the vanadium dioxide film is weak. When the content of the transition metal compound exceeds 5.5 at%, the phase transition temperature of the vanadium dioxide film is very wide. The characteristics as a device are not good.

The present invention relates to a process for the preparation of co-doped vanadium dioxide in which a transition metal exhibiting a transition temperature of lower than 68 ° C is formed of particles having a stable powder state and having a nano-size, and a vanadium oxide (VO ₂ ) We suggest a method. Here, the nano size refers to a size having a unit of nanometer (nm), which means a size of 100 nm or more and less than 1 탆.

As the starting material of the present invention, a vanadium compound or a hydrate or derivative of the compound is used. The vanadium salt may be at least one selected from vanadium pentoxide (V ₂ O ₅ ), vanadyl sulfate (VOSO ₄ ), vanadyl chloride (VOCl ₂ ) acetylacetonate _{[VO (C 5 H 7 O} 2] groups in can be used to select one or more particular, vanadium pentoxide (V ₂ O ₅ to obtain a high yield for money economically made of a) a Is preferably used.

The transition metal compound which is the other one of the starting materials may be at least one transition metal element selected from the group consisting of tungsten (W), molybdenum (Mo), titanium (Ti), tin (Sn), and antimony Two or more kinds of compounds may be used. Of these, tungsten (W), molybdenum (Mo) and the like are preferable from the viewpoint of performance. In particular, the transition metal compound may be at least one tungsten compound selected from the group consisting of tungstic acid, ammonium tungstate, sodium tungstate, and a hydrate thereof; At least one molybdenum compound selected from the group consisting of ammonium molybdate, sodium molybdate, and hydrate thereof; At least one titanium compound selected from the group consisting of titanium dioxide, titanium sulfate, and hydrates thereof; At least one tin compound selected from the group consisting of tin dioxide, tin salts and hydrates thereof; Or one or more antimony compounds selected from the group consisting of antimony trioxide, antimony tetraoxide and hydrates thereof. For example, the transition metal compound is tungsten arithmetic cargo (H ₂ WO ₄ and nH ₂ O), tungstic acid, ammonium ((NH _{4) 2} WO ₄ and 5H ₂ O), sodium tungstate hydrate (Na ₂ WO ₄ and 2H ₂ O) and molybdenum compounds such as ammonium molybdate [(NH ₄ ) ₆ Mo ₇ O ₂₄ .4H ₂ O] and sodium molybdate (Na ₂ MoO ₄ ) can be used.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow chart of a process for producing co-doped vanadium dioxide powder of two transition metal compound compounds according to a preferred embodiment of the present invention. FIG.

As shown in FIG. 1, a method for producing vanadium dioxide according to the present invention includes a starting powder mixing step (P01) for uniformly mixing a vanadium salt and a transition element used for co-doping, a step for mixing the starting powder with a molten (P02), removing the compound from the furnace and quenching it with distilled water (P03), firing to remove moisture (P04), reducing the powder with ammonia and nitrogen gas A reducing step (P05), and a heat treatment step (P06) for stabilizing the reduced powder particles by heat treatment.

The vanadium compound used in the starting powder preparation step (P01) may be the vanadyl salt represented by the formula (1). Specifically, the vanadium salt in the present invention are vanadium pentoxide (V ₂ O _5), vanadium sulfate (VOSO _4, vanadyl sulfate), vanadyl chloride (VOCl _2, vanadyl chloride), and vanadyl acetylacetonate [VO (C ₅ H ₇ O ₂ ) ₂ , vanadyl acetylacetonate] and the like, and vanadium sulfate is preferable from the viewpoint of economical efficiency in obtaining a high yield relative to the price. Here, the hydrate (.nH ₂ O, where n is an integer of 1 to 20) can also be used.

[Chemical Formula 1]

VOX ₂

Wherein X is a sulfate group, a halogen group, or an acetylaceto group.

The transition metal compound, which is the other one of the starting materials, is selected from the group consisting of tungstic acid hydrate (H ₂ WO ₄ .nH ₂ O), sodium tungstate hydrate (Na ₂ WO ₄ .2H ₂ O) and tungstic acid Ammonium molybdate (MoO ₃ .H ₂ O), ammonium molybdate (((NH ₄ ) ₁₀ H ₂ (W ₂ O ₇ ) ₆ ] NH ₄ ) ₂ MoO ₄ ) and sodium molybdate hydrate (Na ₂ MoO ₄ .H ₂ O), and the titanium (Ti) series is one of titanium (TiO ₂ ) tin (Sn) (SnO), and antimony (Sb) series include at least one of antimony trioxide (Sb ₂ O ₃ ) and the like, and two kinds Or more.

At least one of the above-mentioned vanadium salt powders and at least two of the transition metal compounds are prepared according to a predetermined weight ratio, and in the case of the transition metal compound, the doping amount is set to 0.01 at% to 5.5 at% (atomic percent, atomic%) . When the content of the transition metal compound powder is less than 0.01 at%, the effect of lowering the transition temperature of the vanadium dioxide film is insufficient. When the content of the transition metal compound powder is higher than 5.5 at%, the phase transition temperature of the vanadium dioxide film is very wide. This is not good.

The weighed oxide powders are homogeneously mixed and placed in a furnace.

In the molten step (P02), the temperature of the furnace is raised to a temperature higher than the melting point of the vanadium salt (for example, 700 to 1,000 DEG C). The temperature of the furnace is preferably raised at a temperature raising rate of 5 to 50 DEG C / min. For example, the melting point of vanadium pentoxide (V ₂ O ₅ ) is 690 ° C., and when the temperature of the furnace is higher than 690 ° C., vanadium pentoxide (V ₂ O ₅ ) powder starts to be melted. The powder of the vanadium salt is maintained at a temperature higher than the melting point for a predetermined time (for example, 5 minutes to 1 hour) so that the vanadium salt powder can be completely melted. The temperature of the furnace for melting the vanadium salt powder is preferably about 700 to 1,000 ° C. If the temperature is lower than 700 ° C, the vanadium salt powder may not be melted and may not be melted. If the temperature is higher than 1,000 ° C., not only the energy consumption is high but also the production time is long, It is not preferable.

After dissolving the vanadium salt powder, the compound containing the vanadium salt and the transition metal is taken out of the furnace and quenched into a container containing 50 to 300 mL of prepared DI water.

The step (P03) of quenching the above-mentioned distilled water prevents quenching of the sol particles of the vanadium salt containing the two transition metals formed by rapid cooling.

In the subsequent firing step (P04), it is suitably carried out in the temperature range of 300 to 600 ° C, and is maintained for 30 minutes to 3 hours to carry out this step for the purpose of removing the moisture absorbed in the quenching step.

In the reduction step (P05) in a subjected to the firing step (P04) compound of ammonia 5 ~ 50 mL / min (NH 3) gas flow conditions, and 50 to nitrogen of 200 mL / min (N ₂₎ gas flow conditions At a temperature of 400 to 700 ° C for 1 to 5 hours. The temperature is raised at a rate of 2 to 4 ° C / min to reach the reduction condition, and when the reduction is completed, the temperature is slowly cooled to 2 to 4 ° C / min to reach the room temperature.

In this process, the transition metal atoms are uniformly introduced into the crystals of vanadium dioxide, so that the transition metal forms co-doped vanadium dioxide crystals.

A heat treatment step (P06) in a subjected to the reduction step of (P05) a compound of nitrogen of 5 ~ 100 mL / min (N 2) temperature of 500 ~ 800 ℃ the gas flow conditions to be stabilized by heat treatment to the reduced powder For 1 to 6 hours.

On the other hand, in another embodiment of the present invention, the present invention provides co-doped vanadium dioxide in which the transition metal prepared by the method as described above is co-doped. The vanadium dioxide doped with the transition metal has a monoclinic crystal structure at room temperature and turns into a tetragonal crystal at a temperature higher than the phase transition temperature. Further, the vanadium dioxide doped with the transition metal is a fine particle having a nano-size of less than 1 탆 or 980 nm or less, for example, 30 to 980 nm. The particle size of the transition metal-doped vanadium oxide can preferably be 50 to 900 nm, more preferably 80 to 800 nm, and still more preferably 100 to 600 nm.

The phase transition temperature of the vanadium dioxide doped with the transition metal of the present invention can be finely adjusted in the vicinity of room temperature (25 degrees), and the phase transition to the material having the transmission and reflection characteristics to infrared rays at the temperature can be performed. In particular, the transition temperature of the transition metal-doped vanadium dioxide may be about 39.5 degrees or less, or 20 to 39.5 degrees Celsius, preferably 25 to 39 degrees Celsius, more preferably 28 to 38 degrees Celsius.

The vanadium dioxide doped with the transition metal can be analyzed by differential scanning calorimetry (DSC) analysis. DSC (Differential Scanning Calorimeter) analysis is an analysis to confirm the transition characteristics of thermochromic materials. When optical and electrical properties change rapidly at the transition temperature, the metal oxide crystals are converted from monoclinic crystals to tetragonal tetragonal crystals, which are endothermic, so this endothermic process is a definitive clue to the thermochromic material. The existence of this endothermic peak shows the thermochromic characteristics such as the blocking of infrared rays at the transition temperature and the increase of the electric conductivity.

The transition metal-doped vanadium dioxide of the present invention may exhibit a single peak at an endothermic peak at about 39.5 degrees Celsius or at 20 to 39.5 Celsius in the differential scanning calorimetry (DSC) analysis, , It can be confirmed that the electrical characteristic is a rapidly changing thermochromic material. Particularly, since the endothermic peak appears as a sharp single peak, the transition metal acts only to the extent of optimizing the phase transition temperature by controlling the crystallinity, and the problem of deteriorating the excellent physical properties of vanadium dioxide in the form of a mixture in which multiple peaks appear Can be prevented.

Meanwhile, in another embodiment of the present invention, the present invention provides an optical product wherein the transition metal comprises co-doped vanadium dioxide. In particular, the optical article may be in the form of an optical hard coat film having infrared absorption and reflection capabilities.

At this time, it is possible to prepare a coating agent in which the transition metal is dispersed up to 30 wt% of the co-doped vanadium dioxide particles in the production of the infrared hard coat film, and the UV coating curing agent is benzophenone type or aceto phenone type And the binder was synthesized as a film through a bar coater by synthesizing Urethane Acrylate.

In the present invention, matters other than those described above can be added or subtracted as needed, and therefore, the present invention is not particularly limited thereto.

According to the present invention, by reacting vanadium and a transition metal compound in a predetermined content range using a melting method, a transition metal having a smaller particle size and crystallinity and a high phase transition efficiency can be obtained, -Doped vanadium dioxide can be prepared.

The thus-prepared transition metal vanadium dioxide of the present invention can be applied to a thermally conductive film which is easy to adhere to a building or an automobile window, and selectively blocks and transmits infrared rays under a practical temperature condition. Efficient energy saving is possible by reducing cooling and heating costs in winter.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a process flow diagram for a method for producing co-doped vanadium dioxide according to the present invention.
2 is a graph showing the results of X-ray diffraction analysis of the co-doped vanadium dioxide produced through the pyrolysis step according to Example 1 of the present invention.
FIG. 3 is a TEM photograph of co-doped vanadium dioxide particles produced through a pyrolysis step according to Example 1 of the present invention.
4 is a diagram showing DSC analysis results of co-doped vanadium dioxide particles prepared according to Example 1 of the present invention.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the scope of the present invention is not limited to the following examples.

Example 1

A vanadium dioxide doped with a transition metal was prepared in the following manner with the composition shown in Table 1 below.

The transition metal is tungsten (W) and molybdenum (Mo) containing dioxide vanadium (VO ₂₎ powder produced, the vanadium pentoxide with a purity of 97% (V ₂ O ₅₎ powder (Aldrich chemical Company, Ltd.), purity 99% tungsten (Aldrich chemical Co., Ltd.) powder of sodium hydrate (Na ₂ WO ₄ .2H ₂ O) and 98% sodium hydride sodium hydrate (Na ₂ MoO ₄ .2H ₂ O) . 5 at% of a vanadium pentoxide (V ₂ O ₅ ) powder, 2.5 at% of sodium tungstate hydrate (Na ₂ WO ₄ .2H ₂ O) powder and 2.5 at% of sodium sodium molybdate hydrate (Na ₂ MoO ₄ .2H ₂ O) Weighed, weighed powders were charged into a ball mill and homogeneously mixed. At this time, the vanadium salt and the transition metal compound were weighed so that the total content of the transition metal was 5 at% based on the sum of the vanadium element, the tungsten element and the molybdenum element. The powder was mechanically pulverized and uniformly mixed by rotating it at a speed of 200 rpm to 300 rpm using a ball mill. The ball milling was carried out for 24 hours.

The mixed powders were put in a furnace, and the temperature was raised to 800 DEG C at a heating rate of 5 DEG C / min for 20 minutes. The molten powders were removed from the furnace and quenched in a bottle containing 250 mL of distilled water (DI Water). If it takes a long time to quench the distilled water in the furnace, the molten vanadium pentoxide (V ₂ O ₅ ) powder hardens and the metal may precipitate and crystallize. Therefore, the molten mixture is quickly taken out and quenched in distilled water.

(V ₂ O ₅ ), sodium tungstate hydrate (Na ₂ WO ₄ .2H ₂ O) and sodium molybdate hydrate (Na ₂ MoO ₄ .2H ₂ O) are quenched in distilled water so that these substances are dispersed in distilled water The formation of sol was observed.

The sol formed by quenching with distilled water is fired again in a furnace at 400 DEG C for 1 hour to remove moisture adsorbed.

The calcined mixture was fed at a rate of 15 mL / min and 150 mL / min, respectively, for reduction by ammonia gas (NH ₃ ) and nitrogen gas (N ₂ ). The reaction was carried out at 500 ° C for 1 hour. The powder particles thus reduced were supplied with nitrogen gas (N ₂ ) at a rate of 50 mL / min at 650 ° C. for 5 hours in an electric furnace using a quartz tube, and a heat treatment step was performed. At this time, the heating rate of the electric furnace was fixed at 10 ° C / min.

Examples 2 to 3

As shown in the following Table 1, vanadium dioxide doped with a transition metal was prepared in the same manner as in Example 1, except that the transition metal component and the composition were changed.

Comparative Example 1

As shown in the following Table 1, vanadium dioxide was prepared in the same manner as in Example 1, except that no separate transition metal compound was used.

Comparative Examples 2 to 6

As shown in the following Table 1, vanadium dioxide doped with a transition metal was prepared in the same manner as in Example 1, except that the transition metal component and the composition were changed.

Test Example

Crystallinity and transition temperature-related properties were evaluated for vanadium dioxide or vanadium dioxide doped with transition metal prepared according to Examples 1 to 3 and Comparative Examples 1 to 6 in the following manner.

a) Crystallization evaluation

X-ray diffraction (XRD) analysis was performed to confirm the crystallinity of the vanadium dioxide or vanadium dioxide doped with the transition metal prepared through the heat treatment step to determine the crystallographic appearance of the thermochromic material .

b) Shape analysis

Transmission electron microscopy (TEM) analysis was performed to confirm the shape and size of synthesized particles of vanadium dioxide or vanadium dioxide doped with transition metal prepared through the heat treatment step.

c) Transition temperature analysis

Transition characteristics of thermochromic materials were confirmed by performing differential scanning calorimetry (DSC) analysis on vanadium dioxide or vanadium dioxide doped with transition metal prepared through a heat treatment step.

Particularly, when the optical and electrical properties are rapidly changed at the transition temperature in DSC (Differential Scanning Calorimeter) analysis, the metal oxide crystals change from monoclinic crystals to tetragonal crystals, endothermic), this endothermic process is a decisive clue to the thermochromic material. The existence of this endothermic peak shows the thermochromic characteristics such as the blocking of infrared rays at the transition temperature and the increase of the electric conductivity.

The composition and content ranges of vanadium dioxide or vanadium dioxide doped with transition metal prepared according to Examples 1 to 3 and Comparative Examples 1 to 6 are shown in Table 1 below.

Furtherance Transition metal
Doping content
(at%) Transition temperature (캜) Example 1 W-Mo-VO ₂ 5 32.6 Example 2 W-Nb-VO ₂ 5 38 Example 3 W-Mo-VO ₂ 3 38.9 Comparative Example 1 VO ₂ 5 68 Comparative Example 2 W-VO ₂ 5 40 Comparative Example 3 Mo-VO ₂ 5 52 Comparative Example 4 W-Mo-VO ₂ 6 - Comparative Example 5 W-Mo-VO ₂ 7 - Comparative Example 6 W-Mo-VO ₂ 8 -

On the other hand, the X-ray diffraction analysis, the TEM analysis and the DSC analysis of the vanadium dioxide doped with the transition metal prepared according to Example 1 are shown in FIGS. 2 to 4, respectively. In particular, referring to Fig. 2, diffraction peaks are shown for various crystal planes of vanadium dioxide in various peaks, and peaks of transition metal particles are also shown. As a result, it can be seen that the transition metal atoms are uniformly introduced into the crystal of vanadium dioxide through the reduction step (P05). Also, referring to FIG. 3, it can be seen that a slightly pressed square-shaped transition metal co-doped vanadium dioxide crystal is well formed and its size has a crystal size in the range of 100 to 200 nm. According to the results of the DSC analysis of FIG. 4, it can be seen that the optical and electrical properties of the thermochromic material rapidly change at 32.6 ° C. in Example 1.

As shown in Table 1 above, the transition metal co-doped vanadium dioxide particles of Examples 1 to 3 according to the present invention exhibit a fine adjustment of the phase transition temperature due to the fact that the two elements act independently as compared with the case where tungsten is single- And the phase transition temperature is lowered to the vicinity of room temperature.

On the other hand, it can be seen that the vanadium dioxide of Comparative Examples 1 to 3 synthesized according to the conventional method is remarkably deteriorated in fine adjustment of the phase transition temperature and the like. In such a case, fine adjustment to the vicinity of room temperature can not be performed, which may result in a problem that the film can not be applied to the film. Also, as in Comparative Examples 4 to 6, when the total content of the transition metal is excessively doped to 6 to 8 at%, a large change occurs in the VO ₂ particle structure and the characteristic of the thermochromic phase transition at a constant temperature is lost The discard can be seen. Therefore, vanadium dioxide doped with transition metal of Comparative Examples 4 to 6 does not exhibit a phase transition temperature, so that even if particles are formed, a problem that the vanadium dioxide can not be applied to a film may occur.

Claims (8)

Uniformly mixing a vanadium salt and two or more transition metal compounds, and then molten at a temperature of 700 ° C to 1,000 ° C;
After the molten compound is quenched, removing moisture through a firing process;
Reducing the calcined compound with ammonia and nitrogen gas; And
Heat treating the reduced compound at a temperature of 500 ° C to 800 ° C;
Lt; / RTI >
Wherein the vanadium salt and the transition metal compound are reacted such that the content of the transition metal element is 0.01 at% to 5.5 at% based on the sum of the vanadium element and the transition metal element. The method according to claim 1,
Wherein the vanadium salt is at least one transition metal selected from the group consisting of vanadium pentoxide, vanadyl sulfate, vanadyl chloride, vanadyl acetylacetonate and hydrates thereof and derivatives thereof. The method according to claim 1,
Wherein the transition metal compound comprises at least one transition metal element selected from the group consisting of tungsten, molybdenum, titanium, tin, and antimony. The method according to claim 1,
Wherein the baking step is performed at a temperature ranging from 300 ° C to 600 ° C. The method according to claim 1,
Wherein the reducing step is carried out in an inert gas atmosphere at a temperature ranging from 400 ° C to 700 ° C. A transition metal doped vanadium dioxide produced by the process according to any one of claims 1 to 5. The method according to claim 6,
Vanadium dioxide doped with a transition metal having a monoclinic crystal structure and a particle size of 980 nm or less. The method according to claim 6,
Vanadium dioxide doped with a transition metal having a phase transition temperature of 39.5 DEG C or lower.

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