KR20030006579A - Method of producing barium titanate by using new starting materials - Google Patents

Abstract

PURPOSE: A preparation method of barium titanate powder by hydrothermal synthesis is provided, which prevents corrosion of powder preparation equipment and lowers production cost by using Ba and Ti hydroxides as raw materials instead of conventional raw materials containing chlorides. CONSTITUTION: The continuous preparation method of fine and homogeneous BaTiO3 powder through hydrothermal process comprises the steps of: (i) mixing barium hydroxide, Ba(OH)2-8H2O, with titanium hydroxide, TiO(OH)2 in a concentration ratio of 0.5-2 : 1 under pressure of 10-40MPa, which is expressed by the formula TiO(OH)2 + Ba(OH)2-8H2O -->BaTiO3 +10H2O; (ii) supplying hot water to the mixture for 100-400deg.C of mixture; (iii) reacting 3-10sec. to form critical nuclei; (iv) supplying hot water to the intermediates forming critical nuclei, and dehydrating under subcritical and supercritical state to get BaTiO3; (v) separating synthesized materials and recycling.

Description

Method of producing barium titanate by using new starting materials}

The present invention relates to a method for producing barium titanate powder, and more particularly, to a method for continuously producing barium titanate powder in which a series of synthetic steps are sequentially organically formed by using hydrothermal synthesis.

Barium titanate (Barium Taitanate, BaTiO ₃₎ is fetched as a cityscape for lobes steel series dielectric material having a tree structure, the dielectric constant is very large, and is excellent in thermal stability material. Therefore, barium titanate has been used as a main raw material in products such as ceramic capacitors, multilayer ceramic capacitors (MLCC), thermistors, and varistors, which are required for next-generation microwave communication equipment, and will be spotlighted as a basic raw material for these fields. It is foreseen.

In order to achieve such a thinning of a multilayer ceramic capacitor, it is indispensable to refine, homogenize, or purify the particle size of the barium titanate as a raw material. This is because barium titanate has been fine-grained and highly purified since the 1980s by Professor Kent Bowen of MIT and his colleagues insisting that the mono particle distribution of spherical fine particles is extremely effective for sintering. Because it became very important. Subsequently, Arlt et al reported that the dielectric constant at room temperature for the barium titanate sintered body indicates that the sintered particle diameter reaches a maximum of 1 micron and indicates 4,000 or more.

Today, such barium titanate has been industrially produced in several ways. First, there is a solid phase method as a physical synthesis method. This method is a method of mixing the powder of titanium oxide (TiO ₂ ) and barium carbonate (BaCO ₃ ) and then thermal decomposition at a high temperature of 1000 ℃ or more.

Looking at this method,

① As a method of manufacturing titanium oxide (TiO ₂ ), which is one of the raw materials,

First, titanium sulfate is prepared by grinding raw ore and treating with sulfuric acid;

FeOTiO ₂ + 2H ₂ SO ₄ → TiOSO ₄ + FeSO ₄ + 2H ₂ O

Separating and removing ferrous sulfate (FeSO ₄ .7H ₂ O) using a centrifuge;

Heat hydrolysis this to produce titanium hydroxide;

TiOSO ₄ + 2H ₂ O → TiO (OH) ₂ + H ₂ SO ₄

The solution produced above is washed with water to remove sulfuric acid and soluble impurities,

This yields titanium hydroxide, which is prepared by firing at high temperature;

TiO (OH) ₂ → TiO ₂ + H ₂ O

② As another method of manufacturing barium carbonate (BaCO ₃ ),

Grinding the raw ore and sulfuric acid and Coke treatment to produce barium sulfide;

BaSO ₄ + Coke (1200 ~ 1250 ℃) → BaS (Solid)

Heat-hydrolyzing the barium sulfide to produce barium hydroxide;

BaS + H ₂ O → Ba (SH) OH

The material is prepared by firing at high temperature in the presence of carbon dioxide;

Ba (SH) OH + CO ₂ → BaCO ₃ + H ₂ S

( ₃ ) Mixing the titanium oxide (TiO ₂ ) and the barium carbonate (BaCO ₃ )

Thermal decomposition at high temperature (over 1000 DEG C);

TiO ₂ + BaCO ₃ → BaTiO ₃ + CO ₂

By the way, such a solid phase method has the advantage that the production cost of barium titanate is relatively inexpensive, but the disadvantage is that the powder particles are relatively large and the size of the particles is very uneven, which is not suitable for use in precise products.

In order to alleviate these drawbacks, chemical synthesis is proposed. These include an alkoxide method, an oxalate method (coprecipitation method), a hydrothermal synthesis method and the like. First, although the alkoxide method is divided into various types depending on the selection of the starting materials, it is generally synthesized using titanium alkoxide and an aqueous solution of barium hydroxide. According to this method, there is an advantage that the particles can obtain a relatively fine powder, but since titanium alkoxide easily reacts with moisture in the air, and the Ti-OH reaction rapidly occurs in the solution to form hydrated titania, The disadvantage is that it requires careful process control.

In the above oxalate method, barium chloride and titanium chloride solution are mixed to Ba: Ti = 1: 1, oxalic acid is added thereto to precipitate titanium barium oxalate, which is then washed, filtered and dried, It is a method of manufacturing by firing at high temperature. This method has the advantage of relatively simple process and low manufacturing cost, but has the disadvantage that the powder of the barium titanate produced is large.

On the other hand, the above hydrothermal synthesis method is a method of producing crystalline barium titanate by mixing gel hydrate of titanium and barium hydroxide aqueous solution under high temperature and high pressure. This method has already been reported under normal pressure by Kubo of Japan in the 1960s, and was later introduced to the public by receiving a US patent (USP No. 4,643,984) from Sakai Chemical Co., Ltd. in the 1980s. Attention in the market. It is recognized that hydrothermal synthesis is also excellent as a method for synthesizing complex titanates. Looking at the conventional hydrothermal synthesis method according to the US Patent No. 4,643,984 is as follows:

① First, titanium oxide (TiO ₂ ) is prepared by using hydrochloric acid method in raw material ore,

Coke treatment of the titanium oxide at high temperature to produce titanium tetrachloride,

TiO ₂ + Coke + 2Cl ₂ → TiCl ₄ + CO ₂ + CO

Titanium tetrachloride is dissolved in distilled water and reacted with mineralizer

Preparing titanium hydroxide;

TiCl ₄ + 4 NaOH (or KOH) → Ti (OH) ₄ + 4 NaCl (or 4 KCl)

(2) preparing barium hydroxide or barium chloride aqueous solution by a conventional method;

③ the above titanium tetrachloride and the above barium hydroxide (or barium chloride) aqueous solution

Prepared by reacting at about 200 ° C. for about 5 hours;

Ti (OH) ₄ + Ba (OH) ₂ 8H ₂ O → BaTiO ₃ + 11 H ₂ O

However, according to the above hydrothermal synthesis method (USP No. 4,643,984), since the starting material titanium tetrachloride (TiCl ₄ ) causes a vigorous exothermic reaction in air, it must first be dissolved in distilled water to make an aqueous solution of titanium tetrachloride. There is a hassle.

In addition, the above-mentioned hydrothermal synthesis method above all, since the reactants contain a chlorine component, in addition to generating a toxic chlorine (Cl ₂ ) gas in the reaction process, there is a disadvantage inevitably corrodes the manufacturing apparatus. Since this uses a mineralizer (NaOH or KOH), corrosion of a manufacturing apparatus also cannot be avoided. Therefore, in order to solve this problem, it is pointed out that the problem of periodically cleaning the chlorine and alkali components.

In addition, in the hydrothermal synthesis method, the use of titanium tetrachloride prepared by the hydrochloric acid method as a starting material, it is inevitable to add a mineralizer such as potassium hydroxide or caustic soda, such mineralizers affect the dielectric constant of the final product Therefore, there was a problem that the dielectric constant of barium titanate which is the final product is lowered.

The present invention is to improve the disadvantages of the conventional hydrothermal synthesis method, it is an object of the present invention to provide a method for producing barium titanate by a new process that can prevent the corrosion of the manufacturing apparatus.

In order to achieve the above object, the present inventors carefully examine and analyze various problems of the conventional synthetic method, and confirm through a number of experiments. Thus, barium titanate can be produced without using conventional starting materials. By using a new raw material, it is confirmed that it is possible to lower the production cost unlike the existing process while fundamentally solving the corrosiveness to the device, to complete the present invention.

The present invention is characterized by using a titanium-containing hydroxide and a barium-containing hydroxide which does not contain chlorine components as starting materials.

The present invention can produce the barium titanate powder in a conventional batch and continuous mode, and in view of economics, the continuous type is more preferable.

1 is an overall process diagram schematically showing the overall process by the continuous manufacturing method of the present invention,

2 is a SEM photograph of 20,000 times magnification of the barium titanate powder prepared by the production method (Example 1) of the present invention;

3 is a distribution diagram of the barium titanate powder produced by the production method of the present invention,

4 is a SEM photograph of a 20,000-fold magnification of a barium titanate powder prepared by adding a mineralizer to the preparation method (Example 2) of the present invention;

5 is an X-ray diffraction diagram of the barium titanate powders of FIGS. 2 and 4,

6 is a distribution diagram of the barium titanate powder produced by the production method of the present invention.

The present invention comprises the steps of preparing a titanium-containing hydroxide and barium-containing hydroxide as a raw material; And dehydrating the titanium-containing hydroxide and the barium-containing hydroxide to produce barium titanate.

The present invention is characterized in that the use of titanium containing hydroxide as one of the new raw material in the above preparation step and using the barium containing hydroxide as one of the other new raw material. In the present invention, the reason for using titanium-containing hydroxide as a new raw material is to completely exclude the chlorine component from the raw material itself. In the present invention, titanium hydroxide is most preferred as the titanium-containing hydroxide.

In the present invention, barium-containing hydroxide is used as another novel raw material. In the present invention, the reason for using the barium-containing hydroxide as one of the raw materials is to exclude the chlorine component from the raw materials themselves. In the present invention, barium hydroxide is most preferred as the barium-containing hydroxide.

In the present invention, the titanium-containing hydroxide and the barium-containing hydroxide, which are new raw materials, are completely different from the conventional hydrothermal synthesis method in that there is no chlorine component in the material itself. In addition, when these raw materials are used, there is no room for chlorine, so there is no room for corrosion of the manufacturing apparatus due to chlorine. In addition, since these raw materials are highly reactive with each other, there is no necessity of using mineralizers (NaOH or KOH) as in the prior art. There is also an advantage that can increase the dielectric constant uniformly.

The present invention is characterized in that the barium titanate is produced by directly dehydrating the titanium-containing hydroxide and the barium-containing hydroxide in the manufacturing step of the barium titanate. This method is the first attempt in the present invention, which may be referred to as "direct dehydration". In this invention, it is most preferable to use titanium hydroxide as said titanium containing hydroxide, and it is most preferable to use barium hydroxide as said barium containing hydroxide. In the present invention, in the step of reacting the raw material can be prepared barium titanate by dehydration reaction, which is expressed as follows:

TiO (OH) ₂ + Ba (OH) ₂ 8H ₂ O → BaTiO ₃ + 10 H ₂ O

In the present invention, as long as the above starting material is used as a starting material, the production method of the barium titanate can be carried out batchwise or can be carried out continuously. In the present invention, the efficiency is slightly reduced in the manufacturing process when proceeding to the batch, while the continuous process may be preferable to the batch because there is an advantage to increase the productivity when proceeding in a continuous manner. However, the batch is not excluded in the present invention.

In the present invention, the continuous production method of barium titanate is mixed with preheated water to the barium hydroxide and titanium hydroxide solution as the raw material to form a critical nucleus, and supplying the hot preheated water to the subcritical or supercritical It is characterized in that the barium titanate powder is stably prepared by maintaining the state and synthesizing the barium titanate particles by dehydration reaction in the state.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings. However, the accompanying drawings are only provided to be easily carried out by those skilled in the art, it is apparent that the technical spirit of the present invention is not limited to the accompanying drawings.

The present invention uses titanium containing hydroxide as a new raw material. Titanium hydroxide is most preferred as the titanium-containing hydroxide, and titanium hydroxide may be obtained as an intermediate product in the titanium dioxide manufacturing process. For example, 50 to 54% of titanium dioxide grade ore (Ilmenite) is mixed with 85 to 95% sulfuric acid (using 1.5 to 2.0 times the amount of ore) for continuous reaction, and then distilled water is added to the titanium sulfate solution ( Titanyl) was prepared and ferrous sulfate (FeSO ₄ · 7H ₂ O) was separated and removed from the solution using a centrifugal separator, the solution was further quenched, and the concentrated titanium sulfate was heated and hydrolyzed to form titanium hydroxide. (TiO.xH ₂ O or TiO (OH) ₂ ) can be obtained. In this case, when the residual sulfur is removed using the titanium hydroxide using 25% ammonia water, a more pure starting material may be obtained.

The present invention uses barium-containing hydroxide as another raw material. As said barium-containing hydroxide, barium hydroxide is most preferable. At this time, the barium hydroxide may be obtained as an intermediate product in the barium carbonate manufacturing process. For example, barium sulfate is prepared by treating sulfuric acid and coke from raw material ore, dissolved in water to produce Ba (SH) OH by thermal hydrolysis, and then sulfur is removed from Ba (SH) OH. It is to manufacture a new raw material, barium hydroxide. Even in this case, when the residual sulfur is removed by the barium hydroxide with 25% ammonia water, a purer starting material can be obtained.

The present invention proceeds to the step of directly reacting these raw material aqueous solution after preparing the titanium-containing hydroxide and barium-containing hydroxide. The method for producing barium titanate according to the present invention can be both batch and continuous, and in view of productivity, continuous is preferred over batch.

Continuous production method according to the present invention

a). The barium-containing hydroxide and the titanium-containing hydroxide at room temperature are mixed under a pressure of 10 to 40 MPa, and hot preheated water is directly supplied thereto and mixed to raise the temperature to 100 ° C to 400 ° C, and the residence time of the raw material aqueous solution is 10 to 3 seconds. A critical nucleation step of reacting for seconds to produce a critical nuclei;

b). A dehydration and synthesis step of synthesizing barium titanate by directly applying high-temperature preheated water directly to the intermediate product in which the critical nucleus is formed, and dehydrating under rapidly heated subcritical and supercritical states;

c). A recovery step of separating and recovering the synthesized product and sending the remainder to a recovery container; It may include.

In the present invention, in the raw material nucleus forming step, it is preferable that the concentration ratio of the initial reactant is barium-containing hydroxide: titanium-containing hydroxide = about 0.5 to 2: 1. In this step, it is much more preferable to proceed with the reaction without using a mineralizer at all.

In the present invention, in the recovery step, a direct cooling method of directly adding cooling water, and a cyclone-type storage tank considering mass differences between water and barium titanate molecules may be used.

Brief Description of Drawings [Fig. 1] Fig. 1 is an overall process diagram schematically showing the entire process of a preferred embodiment of the present invention as a continuous production method of barium titanate. According to the present invention, a barium-containing hydroxide and a titanium-containing hydroxide are prepared first, and the titanium-containing aqueous solution 1 and the barium-containing aqueous solution 2 are supplied and mixed at room temperature. This is quite different from the manner of US Pat. No. 5,433,878. This is because, in the case of US Pat. No. 5,433,878, the alkali aqueous solution (mineralizer) is heated to a high temperature in advance and then mixed, and the temperature of the mixture reaches 100 to 250 ° C. In the present invention, the aqueous solutions (1) and (2) are each pressurized and conveyed by a non-flow type high pressure pump (3), and are mixed under a pressure of 10 to 40 MPa at room temperature at the mixing point MP1.

In the present invention, the mixed aqueous solution is mixed again at the mixing point MP2 with preheated water 6 supplied preheated to a high temperature in advance. While the temperature of the mixed solution of the aqueous solution is room temperature, the preheated water 6 has a high temperature of about 350 ° C to 450 ° C, so that the mixed solution heated by direct mixing reaches a temperature of about 100 ° C to 400 ° C. . At this temperature condition, the critical nucleus starts to form, so the reaction of the two stages proceeds sequentially. In this case, when the mixed solution is 100 ° C. or less, the rate of generation of the critical nucleus (minimum particle structure for producing barium titanate) is slowed, so that the overall reaction rate is slowed, leading to a decrease in particle formation. As the temperature rises too rapidly, the preheated water and the raw material water solution form an unstable mixed state in the reaction system, and thus the distribution of the produced particles is not preferable. At this time, the reaction time is preferably set to 3 seconds to 10 seconds. If it is less than 3 seconds, the reaction nucleus is too short to grow, whereas if it is more than 10 seconds, the reaction nucleus grows too much, which causes the size of the particles to grow. Since the residence time (τ) of the mixed liquid in the flow tube is expressed as follows, the reaction time can be controlled by adjusting the volume of the tube and the flow rate of the mixed liquid. :

Here, V ₁ means the volume of the flow tube, F ₁ means the flow rate of the mixture aqueous solution, ρ ₁ represents the density of the mixture aqueous solution. FIG. 1 conceptually illustrates the reaction time τ ₁ before entering the reactor 9.

In the present invention, the mixed liquid in which the critical nucleus is generated is mixed at a mixing point MP3 with hot preheated water 8 preheated to 500 ° C to 600 ° C in advance, and then introduced into the reactor 9. At this time, the high temperature preheated water 8 is mixed at the mixing point MP3 and then introduced into the reactor 9 to induce a dehydration reaction more quickly, while achieving uniformity of newly produced composite particles. to be. Therefore, the present invention is to install a mixing point MP3 in this regard in order to minimize the temperature gradient in the reactor 9. From this time, the mixed reaction solution is maintained in a supercritical state, and an external heater may be used in order to further minimize the temperature gradient in the reactor 9.

In the reactor 9, dehydration proceeds to synthesize barium titanate. The dehydration reaction is carried out in the mixing point MP3 and the reactor (9) of Figure 1, wherein the reaction temperature and pressure are maintained in a subcritical and supercritical state, thereby synthesizing barium titanate powder at a fast reaction rate. . Since the reaction time τ ₂ in the reactor 9 is expressed as follows, the reaction time can be controlled by adjusting the volume of the reactor 9 and the flow rate of the mixed liquid. :

Here, V ₂ means the volume of the reactor 9, F ₂ means the flow rate of the mixture aqueous solution, ρ ₂ represents the density of the mixture aqueous solution. 1 conceptually illustrates the reaction time τ ₂ of the dehydration reaction.

In the present invention, when the barium titanate synthesis reaction is completed in the reactor (9), it is then proceeded to the recovery step of the barium titanate powder. In this step, it is preferable to supply the cooling water 10 directly to the finished product immediately and rapidly cool it. This is to prevent the further progress of reaction or crystal growth by rapidly cooling the reaction conditions proceeding in the reactor (9). In this way, the present invention can obtain very uniform and fine barium titanate particles. In order to cool more rapidly and rapidly, the reaction mixture, which is directly cooled directly, may be sent to the heat exchanger (11) to be secondly cooled again. The fine particles of barium titanate, which have undergone the cooling process, flow into the cyclone 12, where they are separated from the mixture aqueous solution and recovered. At this time, the remaining filtrate is collected in the reservoir 15 through the filter 13 and then through the back pressure valve (14). The recovered barium titanate powder is used after washing and drying with water.

Hereinafter, the present invention will be described in more detail based on examples. The following examples are only one of the most preferred embodiments of the present invention, it is obvious that the protection scope of the present invention is not limited thereto.

<Example 1>

As a starting aqueous solution washed with ammonia water, 100 ml of Ba (SH) OH 0.5M aqueous solution and 100 ml of TiO (OH) ₂ 0.5M aqueous solution having good reactivity and relatively low corrosiveness were used as starting materials. The aqueous raw material solution at normal temperature was transferred by the high pressure pump 3 at a rate of 3 ml / min, respectively, and mixed at the mixing point MP1. Next, the mixed aqueous metal salt solution was mixed with preheated water 6 at 400 ° C. at the mixing point MP2, and the mixture was transferred to the critical nucleus forming step while maintaining the reaction temperature at 200 ° C. and the reaction pressure of 30 MPa. The residence time to point MP3 was about 6 seconds. In this process, the aqueous metal salt solution of titanium and barium (1) (2) and the preheated distilled water (6) start to form a critical nucleus. Thereafter, the preheated distilled water (8) was directly added to the aqueous solution mixture containing the critical nucleus so that the temperature at the mixing point MP3 was maintained at 300 ° C and introduced into the reactor (9). From this time, crystal growth starts as the dehydration reaction proceeds, and crystal growth is completed stably in the reactor 9 maintaining 300 ° C. The residence time of the hydrolysis product in the mixing point MP3 and the reactor 9 was 60 seconds, and the reactor 9 was used vertically. The effluent from reactor 9 was cooled to ambient temperature by cooling water 10 and heat exchanger 11. The fine particles formed after cooling were recovered in a reservoir in the form of a cyclone 12, and the remaining part was recovered in a filter 13 installed in front of the back pressure valve 14. The barium titanate powder accumulated in the above storage tank was washed with distilled water, dried, calcined at 1000 ° C. for 2 hours, and the physical properties thereof were measured.

FIG. 2 is a photograph in which the barium titanate powder synthesized in Example 1 is magnified 20,000 times with a scanning electron microscope. The barium titanate powder seen in Figure 3 was found to have an average diameter of about 0.15 to 0.25㎛.

<Example 2>

As in Example 1, the starting materials were prepared in a stirred mixture at room temperature, 0.5 M of KOH was added as a mineralizer, and the mixture was transferred by a high pressure pump at a rate of 3 ml / min, and mixed at the mixing point MP1. Each other operation condition was performed in the same manner as in <Example 1>.

The obtained reaction product was filtered, washed well with acetic acid, ethanol and distilled water, and then ultrasonically washed to remove alkaline components and impurities, and then dried at 1000 ° C. for 2 hours, and then the physical properties thereof were measured.

FIG. 4 is a photograph obtained by magnifying a barium titanate powder synthesized according to Example 2 with a scanning electron microscope at a magnification of 20,000 times. In this case, as shown in FIG. 6, the average diameter of the barium titanate powder was found to be about 0.3 to 0.5 μm.

5 is an X-ray diffraction pattern of the barium titanate powder synthesized in Example 1 and the barium titanate powder synthesized in Example 2 above. According to this data, it can be seen that the barium titanate powder is superior in crystallinity when the mineralizer is not added.

The present invention has the advantage of reducing the corrosion of the device compared to the conventional hydrothermal synthesis method because it uses a new raw material without using a conventional mineralizer.

In addition, according to the present invention, as the barium titanate is stably manufactured without the mineralizer, there is less need to clean the device, thereby reducing the production cost.

In addition, in the present invention, since the reactants are gradually mixed at the mixing points MP1, MP2 and MP3 as the reaction proceeds, they are stably synthesized. Since it occurs evenly with respect to the size of the synthesized particles has the advantage that it is formed uniformly.

In addition, the present invention can proceed to the above-described general process in a continuous series of steps, there is also an advantage that can be produced continuously barium titanate powder having a small particle size and uniform.

Although the method for producing barium titanate according to the present invention has been described in detail with reference to the drawings and examples, it is only the most preferred embodiment of the present invention, and the present invention is not limited thereto. In addition, anyone of ordinary skill in the art will be able to make various modifications and imitations according to the description of the present specification, but it will be apparent that this is also outside the scope of the present invention.

Claims (6)

A method for producing barium titanate, wherein barium titanate is produced by directly dehydrating a titanium-containing hydroxide and a barium-containing hydroxide as a raw material. The method of claim 1, The titanium-containing hydroxide is titanium hydroxide, and the barium-containing hydroxide is barium hydroxide. The method according to claim 1 or 2, The direct dehydration reaction of the titanium-containing hydroxide and the barium-containing hydroxide is a method of producing barium titanate through the following reaction formula: TiO (OH) ₂ + Ba (OH) ₂ 8H ₂ O → BaTiO ₃ + 10 H ₂ O The method of claim 3, Titanium-containing hydroxide: barium-containing hydroxide = 0.5 to 2: The process characterized in that proceeds with a concentration ratio. The method of claim 3, The production process of the barium titanate is carried out in a continuous method, the continuous method is a). The barium-containing hydroxide and the titanium-containing hydroxide at room temperature are mixed under a pressure of 10 to 40 MPa, and hot preheated water is directly supplied thereto and mixed to raise the temperature to 100 ° C to 400 ° C, and the residence time of the raw material aqueous solution is 10 to 3 seconds. A critical nucleation step of reacting for seconds to produce a critical nuclei; b). A dehydration and synthesis step of synthesizing barium titanate by directly applying high-temperature preheated water directly to the intermediate product in which the critical nucleus is formed, and dehydrating under rapidly heated subcritical and supercritical states; And c). And a recovery step of separating and recovering the synthesized product, and sending the remainder to a recovery container. The method of claim 5, C) above. The recovery step is characterized by using a direct cooling method of applying the cooling water directly, and a cyclone-type storage tank considering the mass difference between water and barium titanate molecules.