KR101180829B1 - Method of manufacturing crystalline barium titanate nanoparticles at low temperature - Google Patents

Abstract

The present invention relates to a method for producing crystalline barium titanate nanoparticles, the method for producing crystalline barium titanate nanoparticles at low temperature according to the present invention, by mixing and reacting at least one of acetic acid or acetylacetone and titanium alkoxide, Stabilizing the titanium alkoxide to produce titanium acylate, which is a titanium precursor; A mixing step of adding and stirring an aqueous barium salt solution to the titanium acylate; A maturing step of gelling the titanium acylate-barium salt mixed solution for 10 to 30 hours in an airtight container having an internal temperature of 30 to 60 ° C .; And adding a basic aqueous solution to the gelled mixed solution, and then reacting at a temperature of 20 to 60 ° C. to produce crystalline barium titanate.

According to the present invention, it is possible to produce crystalline nano BaTiO ₃ particles, which are the basic materials of electronic components, preferably at low temperature at room temperature without causing impurities generated by the generation of organic materials only by hydrolysis and condensation polymerization. have.

 Barium Titanate, Sol-Gel Process, Crystalline Particles, MLCC, Electronic Materials

Description

Method for manufacturing crystalline barium titanate nanoparticles at low temperature {METHOD OF MANUFACTURING CRYSTALLINE BARIUM TITANATE NANOPARTICLES AT LOW TEMPERATURE}

The present invention relates to a method for producing crystalline barium titanate nanoparticles, and more particularly, to be used throughout portable electronic devices such as mobile phones, laptops, digital AV equipment such as camcorders, digital cameras, CD-Rs, DVDs, and multimedia products. The present invention relates to a method for manufacturing crystalline barium titanate (BaTiO ₃ ) particles, which are used as a main raw material in the manufacture of ceramic filters and other precision parts, including a multi-layer ceramic capacitor (MLCC), which is a core passive device.

MgTiO ₃ and MgTiO ₄ were developed in Germany around 1936 on the basis of TiO ₂ material development around 1932. The dielectric constant is low as 13 ~ 18, but the temperature coefficient is positive with + 150ppm / ℃, allowing the mixing of CaTiO ₃ (dielectric constant 150, temperature coefficient -1500ppm / ℃) and mixing system, allowing the dielectric constant and temperature coefficient to be adjusted freely. . We developed materials for temperature compensation using a CaTiO ₃ and SrTiO ₃ from the dielectric constant of the 1960, Japan was less practical but less favorable temperature characteristics and dielectric loss. Subsequently, it was found that BaO: TiO ₂ (copper mol%) has a surprisingly large dielectric constant, which is barium titanate (BaTiO ₃ ), which is the base material of a capacitor having a high dielectric constant.

Such barium titanate is a ferroelectric material having a perovskite structure, and has an advantage that the dielectric constant is very high, such as 1000 to 30,000. Such materials include BaTiO ₃ (Barium titanate) and (Pb, Zr) TiO ₃ (Lead Zirconium Titanate), Pb (Mg, Nb) O3-PbTiO3 (Lead magnesium niobate-lead titanate). In addition, barium titanate is a core electronic device used in MLCC (multi-layer ceramic capacitor) chips, portable home appliances such as mobile phones and laptops, digital AV devices such as camcorders, digital cameras, CD-Rs, DVDs, and multimedia products. Electronic ceramic) parts. Recently, according to the trend of miniaturization and weight reduction of electronic devices, models of electronic components are also miniaturized, high capacity, and multifunctional, and this trend will continue in the future.

The production of ultra-small and ultra high-capacity MLCCs (100㎌ or more) requires the support of printing, laminating, and mounting processes required to form sheets thinly, as well as slurry production techniques in which barium titanate particles are uniformly and stably dispersed. For example, the production of barium titanate nanoparticles having a nano-particle size and excellent crystallinity is the most important. Like other ceramic nanoparticles, barium titanate has been studied and commercialized by various methods such as solid phase method, liquid phase method, and gas phase method. The gas phase method has excellent particle properties but is not yet commercialized due to increased equipment and operating costs.

The solid phase method is a method of producing barium titanate by mixing a powder of titanium oxide and barium carbonate and reacting at a high temperature of 1000 ° C or higher. This method has been widely used because it has a low production cost of barium titanate powder. However, by using the reaction at a high temperature, the minimum size of the powder to be produced is around 1 μm, and the shape of the particles is also very uneven. Specifications are required and are not suitable as raw materials for producing small products.

As a liquid phase method, there is a precipitation method using oxalate. For example, Samsung Fine Chemicals proposes a high-quality barium titanate-based powder production method for producing BaTiO ₃ powder by mixing barium chloride, titanium tetrachloride, and oxalic acid with a nozzle spray of an aqueous solution. (Registered patent; 10-0562520, 10-0555399). This method has the advantage of relatively simple and high yield, but it is not easy to control the particle size and entanglement of the particle. In addition, this method also requires heat treatment at a high temperature, the average particle diameter of the powder produced is about 0.5㎛.

Among the methods for producing BaTiO ₃ , the hydrothermal synthesis method belonging to the liquid phase method is known to be the best BaTiO ₃ production method in terms of size and crystallinity of BaTiO ₃ particles. In hydrothermal synthesis, when the temperature is raised above the boiling point of the aqueous solution (above 120 ℃), gaseous phase is generated in the closed space, and the pressure in the container increases, and the increase in pressure causes the arrangement of metal and oxygen inside the particle. It is similar to that of crystalline particles, so that the crystallinity is low but the principle that crystalline particles are produced is used.

However, the microparticles prepared by hydrothermal synthesis include very agglomerated macroparticles. Such macroparticles have a high molding density because the reaction by diffusion inside the aggregates is superior to the diffusion between the aggregates when heat-treated for molding. The production of visible nanoparticles is difficult. In addition, although the synthesis of crystalline particles at low temperature is mentioned as a representative advantage of the hydrothermal synthesis method, the temperature range applied to the hydrothermal synthesis method is about 150-300 ° C, which is higher than the reaction temperature of the general sol-gel method. As the particle size decreases, the particle growth due to the calcination process occurs very well, and the growth of the fine particles becomes a very disadvantageous condition in terms of application.

The sol-gel method is a representative method of the liquid phase method in which the appearance (size, surface area, pore structure) characteristics of the particles are easier to control than the hydrothermal synthesis method. The sol-gel method mixes metal salts and metal alkoxides (MN Kamalasanan et al., J. Appl. Phys. 74 (9), 0021 to 8979 (1993)) as organic materials for Ba and Ti, and apply them onto a substrate. To crystallize.

The sol-gel method allows the production of an oxide having an inorganic network structure at a low temperature, but the metal oxide nanoparticles prepared by the sol-gel process are amorphous, and thus, in order to obtain crystalline particles, the sol-gel method must be used at 500 ° C or higher as described above. Calcination process is required. The first disadvantage of the calcination process is agglomeration. The use of large aggregated powders is not suitable for the manufacture of end applications with nanostructures required by modern industry. In general, the process of preparing nanoparticles by the liquid phase method starts with a starter (dimer) → trimer → trimmer → oligomer → nucleus → primary particle having a crystal phase → final particle ( final particles) or gels.

Of course, when TiO ₂ nanoparticles are used as Ti starting materials of BaTiO ₃ nanoparticles in the hydrothermal synthesis method, BaTiO ₃ nanoparticles are generated by diffusion of Ba components from the TiO ₂ particle surface to the inside without following the above process. However, in the process of manufacturing nanoparticles by the solution method, since the starting material itself or the solvent contains organic materials, oxo-bridge (MOM: M = metal) in which all organic materials are removed by chemical reaction in the solution. It is difficult to manufacture nanoparticles with only). In other words, an organic substance is necessarily present inside the final particle.

In particular, in the production of BaTiO ₃ , this organic material reacts with Ba in which the CO ₂ generated in the calcination process is in a hydrolyzed state, resulting in the generation of impurities called BaCO ₃ or a second phase, thereby lowering the purity of the final product. react with TiO ₂ to form because of the BaTiO _3, releasing CO _2, CO ₂ The weight change at the time of release is so great that it leads to cracking as the shrinkage of the membrane increases, which in turn significantly reduces the electrical properties of the product.

In addition, a large amount of energy is required for the calcination process, which is a significant burden in terms of cost in the mass production process. In addition, the formation of macroparticles by agglomeration between particles in the calcination process makes it difficult to manufacture nano-scale MLCCs, and additional crushing process for removing these macromolecules requires complexity and additional costs. .

In addition, although a considerable amount of organic material is removed by the reaction by a general liquid phase method, atoms are regularly produced by condensation polymerization reaction at the same level as the arrangement of atoms in the solid crystal by the production step of the basic particles or a subsequent process. Since the spatial arrangement of the metal and oxygen atoms in the nanoparticles is similar to the spatial arrangement in the crystal structure, it is very difficult to show crystallinity only by controlling process variables (temperature, composition, concentration, catalyst, etc.). Furthermore, in the case of two-component systems with different reaction rates in Ba and Ti starting materials, such as BaTiO ₃ , the Ba and Ti components are uniformly distributed spatially by chemical reaction at a low temperature of 80 ° C. or lower to have crystallinity. Manufacturing has been known to be almost impossible by the general solution method until now.

In order to solve this problem, Korean Patent No. 10-288502 uses a titanium acylate and a barium compound to prepare a stable sol precursor by controlling the reactivity of titanium, and then spraying it on a strong alkali solution to coprecipitate and precipitate A method for producing barium titanate, which crystallizes barium titanate powder from a solution and then purifies through a washing process, has been proposed. However, according to the above patent document, for crystallization, the precipitation solution must be heated to a high temperature in an autoclave to undergo hydrothermal synthesis. When using a strong alkali solution having a pH of 14 or more, it is described that the hydrothermal synthesis method is excluded. In reality, even with this method, it is difficult to uniformly arrange Ba and Ti particles in a space without hydrothermal synthesis, and in particular, ligand substitution reaction between titanium alcohol and at least one of acetic acid or acetylacetone is performed to prepare titanium acylate. When, there was a problem that by-products are generated by organic materials such as BaCO ₃ .

The present invention is to solve the above problems, an object of the present invention, excluding the generation of organic substances in the sol-gel method, calcination process (calcination) which was basically required in the conventional crystalline metal oxide manufacturing process A method for synthesizing crystalline barium titanate (BaTiO ₃ ) particles which are widely used as a basic material of an electronic material by a chemical reaction at a low temperature near room temperature.

It is also an object of the present invention to provide a method for producing crystalline barium titanate which can produce barium titanate nanoparticles having a uniform crystal structure without using a hydrothermal synthesis method.

The present invention is derived to solve the above problems, the method for producing crystalline barium titanate nanoparticles at low temperature according to the present invention, as shown in Figure 1, the stabilization step (S10); Mixing step (S20); Aging step (S30); And a crystallization step (S40).

The inventor of the present invention has repeatedly studied whether it is impossible to manufacture BaTiO ₃ nanoparticles having a crystal structure by a pure chemical reaction excluding hydrothermal synthesis method, solve the problem of the prior art purely at low temperature near room temperature The present invention proposes a new method which is considered to be capable of producing crystalline nano BaTiO ₃ nanoparticles through the chemical reaction of, which is the so-called "gel-sol method" proposed in the present invention.

Generally, the gel is structurally divided into a polymer gel and a colloidal gel. A polymer gel is one in which all atoms are bonded in a uniform space arrangement in three dimensions without the presence of particles, and a colloid gel is a step of oligomer and nucleus by chemical reaction of starting materials. Fundamental particles are generated via the three-dimensionally connected primary particles by agglomeration. That is, the colloid gel can measure the spherical particles through TEM or SEM analysis.

Therefore, the size of the basic particles of the colloidal gel can be controlled to a size of about 1 to 10nm depending on the reaction conditions, and the Ba and Ti components will be uniformly distributed spatially inside the gel, and the condensation / polymerization reaction during the gelation process. It is also possible to form a Ba-O-Ti oxo-bridge (oxo-bridge). Therefore, if Ba and Ti are uniformly distributed spatially by the control of reaction process variables, and if the gel in which the size of the basic particles is controlled is refined in the form of a sol through a peptizing process, crystalline BaTiO _{3 may be} obtained by chemical reaction at room temperature alone. It has been noted that the preparation of the particles is possible. Here, in order to convert the gel into a sol, a reaction is required by the addition of an aqueous solution containing a catalyst, and the size, shape and crystallinity of the particles are affected by the reaction conditions.

The present invention can be divided into three steps. The first step is the synthesis of stable (Ba-Ti) gels using the starting materials of Ba and Ti, the constituents of BaTiO ₃ , to control the reaction rate of the starting materials so that a uniform mixture of molecular units can be produced Steps S10 and S20 are performed, and the second step is an aging process, in which an inorganic network is generated due to the condensation polymerization reaction and the density of the gel is increased (S30). The final third step is a step (S40) of synthesizing crystalline particles by reacting an amorphous gel with a reinforcing agent (catalyst). Hereinafter, each step of the method for producing crystalline barium titanate nanoparticles at low temperature according to the present invention will be described in detail.

1. Stabilization stage ( S10 )

The stabilization step (S10) is a step of preparing titanium acylate as a titanium precursor by mixing and reacting at least one of acetic acid or acetylacetone with titanium alkoxide to chelate the titanium alkoxide.

As a starting material of the titanium (Ti) atom used in the present invention, titanium alkoxide (Ti (OR) ₄ ) is used, and as a starting material of barium (Ba), preferably barium acetate (Ba) (O ₂ C ₂ H ₃ ) ₂ )), barium chloride (BaCl ₂ ), barium nitrate (Ba (NO ₃ ) ₂ ) or barium hydroxide (Ba (OH) ₂ ) using a barium salt in the form of a single or mixed do. Here, examples of the titanium alkoxide include titanium ethoxide (Ti (O (CH ₃ ) ₄ ), titanium butoxide, Ti (O (CH ₂ ) ₃ CH ₃ ) ₄ ) and titanium iso Propoxide (titanium isopropoxide, Ti (OCH (CH ₃ ) ₂ ) ₄ ), etc. may be used alone or in combination, more preferably titanium isopropoxide (hereinafter referred to as 'TIP').

In the present invention, it is preferable to use acetic acid (AcOH) and acetylacetone (Acac).

Transition metal alkoxides such as titanium alkoxides used in the present invention have a very high reactivity with water due to the low electronegativity of the metal, and thus, have a desired physicochemical property to weaken the reactivity with water and delay the reaction. Most important for the final product preparation.

In order to solve this problem, in the present step, the titanium alkoxide (Ti (OR) ₄ ) is reacted with at least one of acetic acid or acetylacetone to chelate the titanium alkoxide before synthesis of the (Ba-Ti) gel. Titanium acylate is prepared. By doing in this way, stability of the reaction with water of titanium alkoxide is improved. The solution prepared by the reaction of titanium alkoxide (Ti (OR) ₄ ) with at least one of acetic acid or acetylacetone has a low reactivity with water due to the steric hindrance effect of the titanium atom due to chelation.

The effects of steric hindrance due to the reaction of a typical titanium alkoxide, titanium isopropoxide (Ti (OCH (CH ₃ ) ₂ ) ₄ or less), with at least one of acetic acid or acetylacetone are as follows. same.

In pure TIP, the titanium atom is present as a tetragonal, but when reacted with acetic acid, the coordination number of titanium is increased to 6, and stabilized to the extent that no precipitate is formed even when mixed with water due to chelation of the acetate group.

The reaction taking place in a mixed solution of TIP and acetic acid (AcOH) is as follows. The first reaction is a reaction in which the acetate group of acetic acid replaces the isopropyl group of IPA to produce isopropyl alcohol (IPA or ⁱ PrOH).

Ti-O ⁱ Pr (TIP) + HOAc (Acetic acid) ↔ ⁱ PrOH + Ti-OAc (1)

And two ester reactions are possible:

ⁱ PrOH + HOAc ↔ ⁱ PrOAc + H ₂ O (2)

Ti-O ⁱ Pr + Ti-OAc ↔ ⁱ PrOAc + Ti-O-Ti (3)

The reaction of free acetic acid with isopropyl group ( ⁱ Pr) bonded to Ti, or vice versa, is also possible with the reaction of free alcohol with acetate bound to Ti.

Ti-O ⁱ Pr + HOAc ↔ ⁱ PrOAc + Ti-OH (4)

Ti-OAc + ⁱ PrOH ↔ ⁱ PrOAc + Ti-OH (5)

  By the above reactions, a highly reactive Ti-OH group can be obtained, and further, Ti-O-Ti bonds will be formed through the polycondensation reaction. That is, the production of esters at all bonds can ultimately produce oxygen bonds between Ti atoms.

FIG. 2 is a structural diagram showing the structure of titanium acylate Ti ₆ O ₄ (O ⁱ Pr) ₈ (OAc) ₈ produced under the condition of [AcOH] / [TIP] = 2. It can be seen that it is stabilized.

Thus, before the reaction with the barium starting material through the stabilization step (S10), the TIP, acetic acid and the reactor sphere was examined in advance, and in particular, the concentration ratio of TIP and acetic acid through a variety of experiments affect the degree of safety It was confirmed that the molar ratio of at least one of acetic acid or acetylacetone and titanium alkoxide (at least one of acetic acid or acetylacetone / titanium alkoxide, [AcOH ] / [TIP]) was 1.5-4, More preferably, it was 2-3.

2. Mixing step ( S20 )

It is a step of adding and stirring the barium salt aqueous solution to the titanium acylate formed by the stabilization step (S10). That is, in the stabilization step (S10) to prepare a Ti starting material which is partially reduced the reactivity to water, and by adding and stirring the barium salt aqueous solution to it, it is a step of reacting both. Unlike the titanium acylate, the barium salt compound is not sensitive to hydrolysis. Thus, the barium salt compound may be prepared by using a suitable solvent such as water or an organic solvent, and mixing the solution with the titanium acylate solution in a predetermined molar ratio. It is possible to prepare a mixed solution in sol form.

In the mixing step (S20), the preferred molar ratio (Ba) / (Ti) of barium (Ba) and titanium (Ti) for forming a homogeneous mixture at the molecular level is 0.5 to 2.0, more preferably is 1 to 1.5, the molar ratio of water and titanium _{[(H 2 0) / (} Ti)] is preferably from 5 to 7.

3. Ripening step ( S30 )

Aging step (S30) is a step of aging and gelling the titanium acylate-barium salt mixture solution produced by the mixing step (S20) for 10 to 30 hours in an airtight container having an internal temperature of 30 to 60 ℃, condensation and polymerization The inorganic network is produced by the reaction, thereby increasing the density of the (Ba-Ti) gel.

The aging step (S30) is a key step in the present invention. Due to this aging step, the starting material mixed solution is gelled at a low temperature close to room temperature to form an inorganic network structure, and crystallized in a later step, thereby increasing the high temperature. No calcination process or hydrothermal synthesis process is required.

For example, in a solid barium acetate as a barium salt compound, the acetate group is bonded to the Ba atom in the form of a bridge, but the bonding method is changed to a monodentate form as it is dissolved in water. As described above, when an aqueous barium acetate solution is added to a solution having a ratio of [AcOH] / [TIP] in the range of 1.5 to 4, the isopropyl group bound to Ti and monodentate by water, and Ti and The acetate group bound in the form of a bridge is removed. That is, the organic material that causes impurities in the gelation process through aging is removed, and a gel in which Ba and Ti ions are spatially uniformly distributed can be formed.

Therefore, due to the introduction of the aging step (S30), although introduced to give a uniform crystal structure, the coagulation phenomenon of the particles is introduced to give the applicability to the hydrothermal synthesis method or particles, but due to the generation of organic substances Barium titanate nanoparticles can be produced by chemical reactions at low temperatures, namely, hydrolysis and condensation / polymerization reactions, without causing calcining.

4. Crystallization stage S40 )

The crystallization step (S40) is a step of adding a basic aqueous solution to the gelled mixed solution and reacting by stirring at a temperature of 20 to 60 ℃ to produce crystalline barium titanate, the amorphous gel is reacted with a reinforcing agent (catalyst) To synthesize crystalline particles. In other words, Ba and Ti are uniformly distributed spatially through the aging step (S30), and by refining the gel in which the size of the basic particles is controlled through a peptizing process again in the form of a sol, finally the crystal structure consisting of fine particles It is a process of forming. Depending on the reaction conditions in this crystallization step (S40), the size, shape and crystallinity of the particles are affected.

It is preferable to use what shows a strong base as the basic aqueous solution used here, For example, potassium hydroxide (KOH) or sodium hydroxide (NaOH) aqueous solution can be used.

In the present invention, the barium and titanium ions are formed by adding barium acetate aqueous solution to the titanium alkoxide stabilized by the above method and controlling the reactivity of the titanium alkoxide due to the reaction between the titanium alkoxide and acetic acid or at least one of acetylacetone. A uniformly distributed gel was prepared, and crystalline BaTiO ₃ particles, which are frequently used as electronic materials, were synthesized by adding a basic aqueous solution and then stirring at room temperature. As the biggest advantage of the present invention, until now, most of the calcination process at about 1000 ° C. was required to synthesize crystalline BaTiO ₃ particles, but according to the present invention, only a chemical reaction due to simple agitation at room temperature without a calcination process is required. Crystalline particles were synthesized. This result is expected to improve the mass productivity due to the omission of the calcination process, and to reduce the occurrence of high heat, it is also helpful to the environmental aspects. In addition, the synthesis of crystalline metal oxide particles at low temperatures enables the synthesis of not only BaTiO ₃ particles but also other metal oxides such as TiO ₂ , Al ₂ O _3, and ZrO ₂ at low temperatures, thereby contributing much to the nano metal oxide synthesis. It seems to be.

According to the present invention, it is possible to produce crystalline nano BaTiO ₃ particles, which are the basic materials of electronic components, preferably at low temperature at room temperature without causing impurities generated by the generation of organic materials only by hydrolysis and condensation polymerization. have. The development of crystalline BaTiO ₃ nanoparticles manufacturing process by low temperature chemical reaction alone is expected to make a significant contribution to the prevention of environmental pollution due to energy saving and simplification of the process because low reaction temperature and calcination process are not required. It is expected to be a great help to reduce production costs.

Hereinafter, the method for producing the crystalline barium titanate nanoparticles at low temperature according to the present invention will be described through examples of the present invention.

Example 1 - titanium Alkoxide  stabilize

Titanium isopropoxide (Ti (OCH (CH ₃ ) ₂ ) ₄ ) and acetic acid (CH ₃ COOH) were mixed in varying molar ratios ([AcOH] / [TIP]) and stirred at low temperature for 1 hour. Titanium acylate (Ti (OR) _4-x (OAc) _x ) having a low reactivity with it was synthesized.

3 is a result of FT-IR analysis of a sample reacted by changing the above [AcOH] / [TIP]. 3, it can be seen that isopropyl alcohol resulting from the above formula (1) was produced under the condition of [AcOH] / [TIP] = 0.5. When the ratio of [AcOH] / [TIP] was increased to 2, the absorption band due to the isopropyl group ([OCH (CH ₃ ) ₂ ] bound to the TIP was decreased and was due to isopropyl acetate [ ⁱ PrOAcE]. The strength of the absorption bands at 1741 and 1247 cm ^-1 was increased, and increasing the ratio of [AcOH] / [TIP] to 3 or more did not change the strength and position of the absorption bands of isopropyl groups bound to Ti atoms. Absorption bands at 1294.2 resulted from pure acetic acid, which indicates that two moles of acetic acid are chemically bonded to 1 mole of TIP to stabilize TIP, which is highly reactive with water.

In the case of a liquid having a ratio of [AcOH] / [TIP] of 3 or more, water was added for a long time without precipitation. In this case, however, TIP can be stabilized considerably by the reaction with acetic acid, but when the ratio of [AcOH] / [TIP] is 3 or more, acetic acid does not contribute to stabilization, but rather acts as an impurity, and calcining process During the production of BaCO ₃ . Especially when the ratio of [AcOH] / [TIP] is 4 or more, acetic acid has a greater effect of generating BaCO _{3 as an} impurity than the effect of stabilization of TIP.

According to the FT-IR analysis, the acetate group bonded to the Ti atom is present in the form of a bridge in which two Ti atoms and one acetate are bonded, and in the chelate form in which one Ti atom and one acetate atom are bonded. Can be inferred.

Example  2- ( Ba - Ti ) Gel  Synthesis and Aging

After adding the barium acetate aqueous solution while stirring the solution which changed the ratio of [AcOH] / [TIP] to 2-4, the (Ba-Ti) gel was synthesize | combined through the aging process at 45 degreeC for 12 to 24 hours. It was. A photograph of the gel thus prepared is shown in FIG. 4.

According to the results of the small angle XRD of the (Ba-Ti) gel prepared by aging for 24 hours, it can be seen that the fine particles of about 9 nm are aggregated and have a mesoporous porous structure. The FT-IR analysis of the prepared gel shows that the spatial arrangement of Ba and Ti atoms present in the gel is at a position similar to that in the crystalline BaTiO ₃ particles (FIG. 5, 540 nm). And absorption band of 405nm)

Example  3- crystalline BaTiO ₃  Synthesis of Particles

After adding KOH and NaOH basic solutions to the (Ba-Ti) gel prepared in Example 2, crystalline BaTiO ₃ particles were synthesized by stirring at room temperature. It was. As shown in Figure 6, it can be seen that when the basic solution is added to the gel, as the reaction time elapses, the gel mass decreases and white particles are produced.

According to the XRD analysis results of the sample with the change of the basic solution concentration, the crystalline particles were not prepared for the particles prepared by adding the 1N KOH solution, but the crystalline particles were prepared from the sample to which the KOH solution of 2N or more was added ( 7). For particles prepared in 2N KOH solution, some TiO ₂ crystals were also produced in the second phase. In addition, the crystallinity is best when the 3N, and when increasing the KOH concentration to 3N or more it can be seen that the size of the particle decreases.

8a to 8c are SEM results of crystalline BaTiO ₃ particles prepared by mixing KOH concentration 3N, 4N, 5N solution and (Ba-Ti) gel, respectively. All are spherical and the particle size decreases with decreasing KOH concentration.

The foregoing has been described in detail with reference to preferred embodiments of the present invention. However, the scope of the present invention is not limited to the above embodiments, but may be embodied in various forms of embodiments within the appended claims. Without departing from the gist of the invention as claimed in the claims, any person skilled in the art to which the invention pertains is considered to be within the scope of the claims of the invention to the various possible modifications possible.

1 is a flow chart sequentially illustrating a method for producing crystalline barium titanate nanoparticles at low temperature according to the present invention.

2 is a structural diagram showing a structure of titanium acylate produced under the condition of [AcOH] / [TIP] = 2;

FIG. 3 shows the results of FT-IR analysis on a sample reacted by changing [AcOH] / [TIP] according to Example 1 of the present invention.

Figure 4 is a photograph of the gel produced by aging according to Example 2 of the present invention

5 is an FT-IR analysis of the gel prepared by Example 2 of the present invention

6 is a view showing a particle generation process with the reaction time according to Example 3 of the present invention.

7 is an XRD analysis result of a sample in which the concentration of the basic solution according to Example 3 of the present invention is changed.

8A to 8C are SEM results of crystalline BaTiO ₃ particles prepared by mixing KOH concentration 3N, 4N, 5N solution and (Ba-Ti) gel, respectively.

Claims (5)

Stabilizing step of preparing titanium acylate as a titanium precursor by mixing and reacting at least one of acetic acid or acetylacetone with titanium alkoxide to chelate the titanium alkoxide; A mixing step of adding and stirring an aqueous barium salt solution to the titanium acylate; A maturing step of gelling the titanium acylate-barium salt mixed solution for 10 to 30 hours in an airtight container having an internal temperature of 30 to 60 ° C .; And Adding a basic aqueous solution to the gelled mixed solution and then reacting at a temperature of 20 to 60 ° C. to produce a crystalline barium titanate, In the stabilization step, the molar ratio (at least one of acetic acid or acetylacetone / titanium alkoxide) of at least one of acetic acid or acetylacetone is 2 to 3, The molar ratio ([Ba) / (Ti)] of barium (Ba) and titanium (Ti) in the mixing step is 1 to 1.5, and the molar ratio [(H ₂ 0) / (Ti)] of water and titanium is A method for producing crystalline barium titanate nanoparticles at low temperature, characterized in that 5 to 7. The method of claim 1, The barium salt is a method for producing crystalline barium titanate nanoparticles at low temperature, characterized in that at least one of barium acetate, barium chloride, barium nitrate and barium hydroxide. delete delete delete

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