KR20150060189A - Method of preparing barium titanyl oxalate, method of preparing barium titanate comprising the same, and barium titanate prepared thereby - Google Patents

Abstract

Disclosed are a manufacturing method of barium titanyl oxalate, a manufacturing method of barium titanate, and the barium titanate. The disclosed manufacturing method of barium titanyl oxalate comprises the steps of: manufacturing a barium compound solution, a titanium compound solution, and an oxalate solution (a material solution manufacturing step); contacting the barium compound solution and the titanium compound solution with the oxalate solution, and compounding the barium titanyl oxalate [BaTiO(C_2O_4)_2·4H_2O] (BTO) (a BTO compounding step); wet-grinding the dried BTO (a BTO dry-grinding step); drying the wet-ground BTO, and gaining a BTO powder (a BTO drying step); and dry-grinding the dried BTO (a BTO dry-grinding step). The BTO dry-grinding step is conducted until a bulk density of the dry-ground BTO is greater than or equal to 0.2 g/cm^3 and less than or equal to 0.50 g/cm^3.

Description

A method for producing barium titanyl oxalate, a method for preparing barium titanate, and a method for preparing barium titanate, and a method for preparing barium titanate,

A process for producing barium titanyl oxalate, a process for preparing barium titanate, and barium titanate are disclosed. More particularly, the present invention relates to a process for producing barium titanyl oxalate capable of obtaining a barium titanyl oxalate powder having a low bulk density by improving dry grinding efficiency, a method of producing barium titanyl oxalate having a high crystallinity A process for producing barium titanate capable of obtaining barium titanate, and barium titanate produced by the method are disclosed.

The present invention is derived from the research carried out by the Ministry of Knowledge Economy and the Korea Industrial Technology Evaluation & Management Service (KEIT) as part of the development project of fusion composite parts.

[Task Control Number: 10040832, Title: Development of 50 ~ 80nm BaTiO ₃ Powder Material and Device Manufacturing Technology for 47μF Class 1005 MLCC]

Conventionally, barium titanate powder has been produced by a solid phase reaction in which titanium dioxide (TiO ₂ ) and barium carbonate (BaCO ₃ ) are mixed and heat-treated at a high temperature. In recent years, barium titanate powder has been used as a small-capacity (MLCC) multilayer ceramic condenser It is required to have high purity / composition uniformity, fine particle / particle uniformity, non-cohesive / high dispersibility due to low temperature firing, high frequency and high performance due to high dielectric constant, high dielectric constant, dielectric thinning, Have been used for the production of barium titanate powder. However, for mass production of barium titanate powder, coprecipitation, which is a kind of liquid phase method, is required to obtain chemically uniform barium titanate powder with low manufacturing cost.

In the coprecipitation method, a liquid raw material containing barium (Ba) and titanium (Ti) is contacted with oxalic acid (H ₂ C ₂ O ₄ ) to form barium titanyl oxalate [BaTiO (C ₂ O ₄ ) ₂ .4H ₂ O] (Hereinafter simply referred to as BTO) is formed, and then the BTO is heat-treated at a high temperature to synthesize a barium titanate (BaTiO ₃ ) powder having an appropriate size. In this coprecipitation method, barium titanate (BT) formed after calcination of BTO is strongly agglomerated when the precipitated BTO is not pulverized to an appropriate size, so that a large amount of fine powder is generated along with particle separation in the BT grinding process , The particle size distribution of BT is widened, and crystallinity is deteriorated. Accordingly, the above properties are required to make the BTO small. Therefore, in the conventional coprecipitation method, a wet grinding process with high grinding efficiency is adopted and used. However, as the drying process after the wet grinding process proceeds, the BTO particles agglomerate with each other to increase the ratio of agglomerates in the BTO powder, There is a problem that the crystallinity of barium titanate which is the final product is lowered. In addition, when the barium titanate is applied to MLCC, abnormal grain growth may occur during sintering of the MLCC, and pores may be formed inside the particles, which negatively affects the capacity and reliability of the MLCC. It is difficult to apply barium titanate to a high-capacity MLCC.

One embodiment of the present invention provides a method for producing barium titanyl oxalate capable of obtaining a barium titanyl oxalate powder having a low bulk density by improving dry grinding efficiency.

Another embodiment of the present invention provides a method for producing barium titanate in which barium titanate having a high crystallinity is obtained because the content and the necking ratio of the aggregate are low.

Another embodiment of the present invention provides barium titanate which can be used for a small-to-high capacity multilayer ceramic capacitor manufactured by the above-mentioned method for producing barium titanate.

According to an aspect of the present invention,

Barium compound solution, titanium compound solution and oxalic acid solution (raw material solution preparation step);

(BTO synthesis) of barium titanyl oxalate [BaTiO (C ₂ O ₄ ) ₂ .4H ₂ O] (hereinafter simply referred to as BTO) by bringing the barium compound solution and the titanium compound solution into contact with the oxalic acid solution, step);

Wet pulverizing the synthesized BTO (BTO wet pulverization step);

Drying the wet pulverized BTO to obtain a BTO powder (BTO drying step); And

And dry-milling the dried BTO (BTO dry milling step)

The BTO dry grinding step is carried out until the bulk density of the dry pulverized BTO is from 0.2 g / cm ³ to 0.50 g / cm ³ or less.

The barium compound solution is prepared by dissolving at least one barium compound selected from the group consisting of barium chloride (BaCl ₂ ), barium nitrate (Ba (NO ₃ ) ₂ ) and barium perchlorate (Ba (ClO ₄ ) ₂ ) Wherein the titanium compound solution is prepared by dissolving at least one titanium compound selected from the group consisting of titanium oxychloride (TiOCl ₂ ) and titanium tetrachloride (TiCl ₄ ) in water, and the oxalic acid solution is prepared by dissolving oxalic acid in water Lt; / RTI >

The BTO synthesis step may be performed at a synthesis temperature of 20 to 100 < 0 > C.

The BTO dry pulverization step may be carried out using at least one pulverizer selected from the group consisting of a hammer mill, an air flow classifier (ACM) and a jet mill.

The dry-milled BTO may have a particle size (PSA D50) of 2.5 μm or less and a particle size (PSA D90) of 8.0 μm or less.

The method of producing barium titanyl oxalate may further comprise, between the BTO synthesis step and the BTO wet grinding step, aging the synthesized BTO, filtering the aged BTO, and treating the filtered BTO with an excess And washing with water.

According to another aspect of the present invention,

Barium titanate (BaTiO ₃ ) (hereinafter simply referred to as BT) (BT synthesis step) by heat-treating BTO prepared according to the production method of barium titanyl oxalate at 800 to 1000 ° C, Of the present invention.

The method for producing barium titanate may further include a step (BT crushing step) of pulverizing the synthesized BT after the BT synthesis step.

According to another aspect of the present invention,

And barium titanate produced by the method for producing barium titanate.

The barium titanate powder composed of the barium titanate may contain not more than 10% by weight of agglomerates.

According to the method for producing barium titanyl oxalate according to one embodiment of the present invention, by introducing the dry grinding step, it is possible to achieve the homogenization of the barium titanyl oxalate and the grinding level up, and the productivity can be improved.

According to the method for producing barium titanate according to another embodiment of the present invention, barium titanate having a high crystallinity can be obtained because the aggregate content and the necking ratio are low.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is a diagram for explaining the action and effect of the BTO dry pulverization step in the method for producing barium titanyl oxalate (BTO) according to one embodiment of the present invention. FIG.
FIG. 1B is a view for explaining a problem that occurs when the BTO dry pulverization step is not performed, as in the conventional method for producing barium titanyl oxalate (BTO).
2 is a SEM photograph of BTO prepared according to the BTO production method of some examples and comparative examples.
FIG. 3 is a graph showing the results of a comparison between the results of the BT production according to the BT production method of the present invention and the comparative example, in which the BT dispersion was prepared by dispersing BT in an alcohol and then filtering the BT dispersion with a filter. Agglomerate).
4 is a SEM photograph of BT prepared according to the BT production method of some examples and comparative examples.
5 is an XRD spectrum of BT prepared according to the BT production method of some examples and comparative examples.

Hereinafter, a method for producing barium titanyl oxalate and a method for producing barium titanate according to an embodiment of the present invention will be described in detail.

A method for producing barium titanyl oxalate according to an embodiment of the present invention includes the steps of preparing a barium compound solution, a titanium compound solution, and an oxalic acid solution (raw material solution preparation step), adding the barium compound solution and the titanium compound solution to the oxalic acid (BTO synthesis step) of barium titanyl oxalate [BaTiO (C ₂ O ₄ ) ₂ .4H ₂ O] (hereinafter simply referred to as BTO) by bringing the obtained BTO into contact with a solution, (BTO wet grinding step), drying the wet pulverized BTO to obtain BTO powder (BTO drying step), and dry-pulverizing the dried BTO (BTO dry grinding step).

The barium compound solution is prepared by dissolving at least one barium compound selected from the group consisting of barium chloride (BaCl ₂ ), barium nitrate (Ba (NO ₃ ) ₂ ) and barium perchlorate (Ba (ClO ₄ ) ₂ ) It can be done. The concentration of the barium compound solution may be 0.2 to 2.0 mol / L. When the concentration of the barium compound solution is within the above range, the productivity of barium titanate (BT) described later with respect to the volume of the barium compound solution is high, and the barium compound is not precipitated.

The titanium compound solution may be prepared by dissolving at least one titanium compound selected from the group consisting of titanium oxychloride (TiOCl ₂ ) and titanium tetrachloride (TiCl ₄ ) in water. The concentration of the titanium compound solution may be 0.2 to 2.0 mol / L. If the concentration of the titanium compound solution is within the above range, the productivity of the BT compound to the volume of the titanium compound solution is high, and the titanium compound is not precipitated.

The oxalic acid solution may be prepared by dissolving oxalic acid (H ₂ C ₂ O ₄ ) in water. At this time, the oxalic acid solution may be used in a larger amount than the barium compound solution or the titanium compound solution. Specifically, the concentration range of the oxalic acid solution may be 0.2 to 5.0 mol / L. When the concentration of the oxalic acid solution is within the above range, the productivity of BT relative to the volume of the oxalic acid solution is high, and oxalic acid can be completely dissolved in water.

The BTO synthesis step may be performed at a synthesis temperature of 20 to 100 ° C, for example, 50 to 90 ° C. If the synthesis temperature is within the above range in the BTO synthesis step, the productivity of BTO is high and the synthesized BTO can be prevented from being re-decomposed.

In the BTO synthesis step, the barium compound solution and the titanium compound solution may be simultaneously or sequentially contacted with the oxalic acid solution in the form of a mixed solution or separately. The contact may proceed by nozzle injection, and the time at which the contact is made (i.e., the contact time) may be from 1 to 3 hours. This contact time can be achieved by adjusting the injection speed of the nozzle. Injection nozzles can use a first-flow or second-flow nozzle depending on the flow of the fluid, and the use of a first-flow nozzle may be more advantageous in terms of convenience and obtaining uniform sediment. The first nozzle may be a full cone, a hollow cone, or a flat nozzle. For example, a process for producing BTO [BaTiO (C ₂ O ₄ ) ₂ .4H ₂ O] by bringing an aqueous barium chloride solution as a barium compound solution and an aqueous titanium oxychloride solution as a titanium compound solution into contact with an oxalic acid aqueous solution is as follows: Can be displayed together.

[Reaction Scheme 1]

BaCl ₂ .2H ₂ O + TiOCl _2. + 2H ₂ C ₂ O ₄ .2H ₂ O? BaTiO (C ₂ O ₄ ) ₂ .4H ₂ O + 4HCl

Next, the synthesized BTO can be aged (BTO aging step), filtered (BTO filtration step), and then washed with water (BTO cleaning step). The BTO aging step may be advantageous in productivity from 0.5 to 2 hours. Here, filtration refers to a process of separating only solid phase BTO from a BTO-containing BTO slurry using a centrifugal separator, a filter press, or the like. Thereafter, the filtered BTO can be washed with excess water until the pH of the washing liquid becomes neutral.

Optionally, the cleaned BTO can then be dried at 80-150 ° C for 8-12 hours.

Thereafter, the BTO obtained through the above process is wet pulverized (BTO wet pulverization step). Here, wet grinding refers to pulverizing BTO together with a predetermined medium into a wet grinder such as a beads mill, a ball mill, and an attrition mill. Here, the medium means water such as organic medium such as alcohol and deionized water. If organic medium is used, it is advantageous from the viewpoint of grinding efficiency and particle size control, but there is a disadvantage that cost is increased. This simplifies the process and reduces costs. When water is used as the medium, the amount thereof may be 1 to 10 parts by weight based on 1 part by weight of BTO. When the amount of the water used is within the above range, the viscosity is adequate and the pulverization is easy, and the productivity of BTO relative to the volume of water is high. The milling time needs to be appropriately controlled by the difference in milling power depending on the milling equipment, and it may be 10 to 300 minutes when using the bead mill. By adjusting the milling time in this manner, the particle size of the BT powder as the final product can be appropriately controlled. During the wet milling process, a nitrogen-containing additive such as ammonia can be further added. This makes it possible to acidify the mixture before and after pulverization, increase the viscosity of the BTO slurry after pulverization, and reduce the dielectric property of the powder due to the presence of chloride ions in the synthesized BTO Partially or completely.

Next, the wet pulverized BTO is dried at a temperature of 400 DEG C or lower to remove the used medium (BTO drying step). As a result, a dried BTO powder is obtained. In this case, it is natural that the drying temperature should be equal to or higher than the boiling point of the medium in order to evaporate and remove the used medium.

Thereafter, the dried BTO is dry-pulverized (BTO dry pulverization step). As a result, a dry milled BTO powder is obtained.

The BTO dry grinding step is carried out until the bulk density of the dry pulverized BTO becomes 0.2 g / cm ³ or more and 0.50 g / cm ³ or less. Accordingly, the ratio and necking ratio of the agglomerate in the barium titanate powder prepared by heat-treating the dry pulverized BTO powder may be reduced. In the heat treatment of BTO (i.e., during the BT synthesis step), BTO decomposes The generated gas (CO, CO ₂ , H ₂ O, etc.) is efficiently removed, defects formed in the BT are minimized, and thus a highly crystalline BT can be obtained. In this specification, " necking " means that when two or more particles are bonded to each other, a constricted portion occurs at the boundary.

The dry-milled BTO may have a particle size (PSA D50) of 2.5 μm or less and a particle size (PSA D90) of 8.0 μm or less. In this specification, particle diameters (PSA D10, PSA D50 and PSA D90) were measured with a particle size analyzer (Malvern Mastersizer 2000).

Hereinafter, the operation and effect of the BTO dry grinding step will be described in detail with reference to FIG. 1A.

1A, the BTO dry grinding step reduces the bulk density of the dry-milled BTO powder to less than 0.50 g / cm ³ , so that the dry milled BTO powder has a low aggregate formation ratio, The ratio in which they exist in a state of being separated from each other increases. On the other hand, when the bulk density of the dry pulverized BTO powder is reduced to less than 0.2 g / cm ³ , the fine BTO is present in a re-agglomerated state without being separated from each other. As a result, There is a problem that the BTO powder present in the form of voids has a slow grain growth due to the slow BTO particle diffusion rate during the heat treatment. Thus, when the dry-milled BTO powder, that is, the BTO powder having a bulk density of 0.2 g / cm ³ or more and 0.5 g / cm ³ or less is heat-treated, the BT particles having a high ratio of the BT particles, . The BT powder is then applied to the MLCC. That is, the MLCC is manufactured by disposing the BT powder between the two electrode layers 10 to form the dielectric layer 20. At this time, the dielectric layer 20 contains a large proportion of BT particles arranged regularly without being agglomerated with each other. The MLCC is then sintered. At this time, the BT particles of the dielectric layer 20 are crystallized to form a void-free crystal structure. Thus, FIG. 1A illustrates that the BTO dry milling step has the action and effect of forming BT with high crystallinity.

Hereinafter, with reference to FIG. 1B, the problems that occur when the BTO dry milling step is absent or not suitable, as in the conventional method of producing barium titanyl oxalate (BTO), will be described in detail.

Referring to FIG. 1B, when the BTO dry milling step is absent or not suitable, the dry milled BTO powder is present with at least some of the BTO particles forming aggregates. Accordingly, when the dry-milled BTO powder is heat-treated, at least a part of the synthesized BT particles forms a BT powder present in the form of agglomerates. In addition, the BT powder has pores as a result of aggregate formation. The BT powder is then applied to the MLCC. That is, the MLCC is manufactured by disposing the BT powder between the two electrode layers 10 to form the dielectric layer 20 '. At this time, the dielectric layer 20 'contains a large proportion of irregularly arranged BT particles, which are agglomerated with each other. The MLCC is then sintered. At this time, the BT particles of the dielectric layer 20 'are crystallized to form a crystal structure including voids. Thus, FIG. 1B illustrates the problem that BT with low crystallinity is formed without the BTO dry milling step.

The BTO dry pulverization step may be carried out using at least one pulverizer selected from the group consisting of a hammer mill, an air classifying mill (ACM), and a jet mill. The rotor rotation speed of the hammer mill and the airflow classifying pulverizer and the air pressure of the jet mill were such that the dry milled BTO had a bulk density of 0.2 g / cm ³ Or more and 0.50 g / cm < ³ > or less.

Then, the BTO powder is filled in a heating furnace and then heat-treated at 800 to 1000 ° C to synthesize barium titanate [BaTiO ₃ ] (hereinafter simply referred to as BT) (BT synthesis step). When the heat treatment temperature is within the above range in the BT synthesis step, barium titanate having a target particle size (PSA D50) (that is, 0.08 to 0.5 탆) can be obtained. In the BT synthesis step, impurities (CO, CO ₂ , H ₂ O, etc.) including moisture and / or carbon may be removed. The temperature raising rate from the drying temperature of the BTO drying step to the heat treatment temperature of the BT synthesis step may be 0.5 to 10 占 폚 / min, for example, 1 to 5 占 폚 / min. When the temperature raising rate is within the above range, productivity of BT is high and the temperature distribution becomes uniform, and the particle size of the BT powder becomes uniform. By performing the BT synthesis step as described above, water and excess carbon dioxide gas existing as crystal water are removed in the BTO crystal, and BT powder of several tens nm to several hundreds nm is obtained through the processes of the following Reaction Schemes 2 to 4 .

[Reaction Scheme 2]

BaTiO (C ₂ O ₄ ) ₂ .4H ₂ O? BaTiO (C ₂ O ₄ ) ₂ + 4H ₂ O

[Reaction Scheme 3]

BaTiO (C ₂ O ₄ ) ₂ + 1/2 O _{2 -} > BaCO ₃ + TiO ₂ + 2CO ₂

[Reaction Scheme 4]

BaCO ₃ + TiO _{2 -} > BaTiO ₃

Sagger or Tray may be used as a heating furnace for the heat treatment of the dried BTO powder. Here, Sagger refers to refractory earth containers. The sagger may be, for example, a hexagonal container having a square bottom surface.

Thereafter, BT produced through the BT synthesis step is pulverized to obtain BT powder (BT pulverization step). However, this BT crushing step may be omitted. The BT pulverization step may be performed by wet grinding using a pulverizer such as a beads mill, attrition mill, or ball mill together with a predetermined medium, jet mill or a disk mill in a state in which no medium is used, or by dry grinding using frictional force with the grinder. The pulverization step is intended to solve the intergranular agglomeration of barium titanate. After the wet pulverization, a drying process is additionally required, but it is not necessary to use facilities specially limited for drying. In the BT grinding step, when the grinding efficiency is excessively high, fracture of the particles is caused and a large amount of fine powder is generated. As a result, the particle size distribution and crystallinity may be lowered, Only the necking between the particles can be broken without destroying itself.

Another aspect of the present invention provides barium titanate produced by the above-described method for producing barium titanyl oxalate.

The barium titanate powder composed of barium titanate may contain not more than 10% by weight of agglomerates. In the present specification, the term "aggregate" means a BT dispersion in which a predetermined amount (for example, 5 g) of BT powder is dispersed in alcohol (for example, 150 ml of ethanol) Means a material that does not pass through the filter when it is injected into a filter having a mesh size of 탆 and then filtered.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

Example

Example  1 to 5 and Comparative Example  1-4

(BTO synthesis and aging)

1320 L of a 1 mol / L aqueous solution of barium chloride and 1200 L of a titanium tetrachloride aqueous solution having a concentration of 1 mol / L were mixed well in a 4M ³ glass-lined reaction tank to prepare a mixed aqueous solution. Then, the mixed aqueous solution was injected into 2520 L of oxalic acid aqueous solution having a concentration of 1 mol / L prepared in a 6M ³ reactor at a rate of 2.5 L / min using a full cone type nozzle. A diaphragm pump was used to supply the mixed aqueous solution during nozzle injection. At this time, the oxalic acid solution was sprayed while stirring with a stirrer, the stirring speed of the stirrer was maintained at 150 rpm, and the temperature of the oxalic acid solution was maintained at 70 ° C.

 After the dropwise addition of the mixed aqueous solution for 2 hours, the reaction temperature was maintained for 1 hour, and the mixture was air-cooled while stirring and aged for 1 hour. As a result, a BTO slurry containing BTO was obtained.

(Filtration and washing of the synthesized BTO slurry)

The BTO slurry prepared above was filtered with a centrifugal separator, and the washed BTO was obtained by washing the washed slurry with an excessive amount of water to a pH of 3 or more.

(Wet grinding and drying of cleaned BTO)

50 kg of BTO, 250 kg of deionized water and 0.5 kg of 29 vol.% Ammonia water (8.4 molar parts relative to 100 molar parts of BTO) were charged into a mixing tank and stirred to produce a slurry. At this time, the pH of the slurry was 4.5. Thereafter, the BTO was wet pulverized so as to have a maximum particle diameter of 5 탆 or less with a 20 L horizontal bead mill (medium: deionized water). After milling, the slurry had a pH of 5.1 and a viscosity of 1800 cP. The BTO slurry thus obtained was dried in an oven at a temperature of 200 DEG C for 12 hours to prepare a BTO powder.

(Dry milling of dried BTO)

The dried BTO was fed to a hammer mill (DGHSM-2), an air stream classifier (BCM-T1-00) or a jet mill (SEISHIN ENTERPRISE, STJ-560) at a rate of 4 kg / hr Followed by dry pulverization. As a result, dry milled BTO was obtained. The rotor rotation speed of the hammer mill, the rotor rotation speed of the airflow classifying pulverizer, and the air pressure of the jet mill employed in each of the above Examples and Comparative Examples are shown in Table 1 below.

Dry grinding device Process variable Rotation speed (rpm) or air pressure (MPa) Comparative Example 1 Hammer mill Rotation speed of the rotor 2000 Comparative Example 2 4000 Comparative Example 3 6000 Comparative Example 4 ACM Rotation speed of the rotor 5000 Example 1 8000 Example 2 11000 Example 3 Jet mill windage 0.5 Example 4 0.6 Example 5 0.7

(Heat treatment, wet grinding and drying)

The dry-pulverized BTO powder was put into an electric furnace (Wonjun, RHK) and heat-treated at 930 ° C for 3 hours. As a result, a BT powder was obtained. Then, the BT powder was wet-pulverized for 30 minutes at a peripheral speed of 5 m / s (i.e., 1500 rpm) using 20 L of a horizontal type bead mill (medium: deionized water). The BT slurry formed after the wet grinding was dried in an oven at 150 캜 for 24 hours. As a result, a BT powder was obtained.

Evaluation example

Evaluation example  1: dry-milled BTO Evaluation of bulk density

The bulk density of the dry pulverized BTO obtained in each of the Examples and Comparative Examples was measured. The results are shown in Table 2 below. Specifically, the bulk density of the dry-milled BTO (i.e., BTO powder) was measured according to ISO 23145-1 standard.

Evaluation example  2: BTO Particle size measurement

The particle sizes (PSA D10, PSA D50 and PSA D90) of the dry-milled BTO obtained in the above Examples and Comparative Examples were measured and the results are shown in Table 2. Here, PSA D90) was measured using a particle size analyzer (Malvern, Mastersizer 2000).

Bulk density
(g / cm ³⁾ Particle size (탆) PSA D10 PSA D50 PSA D90 Comparative Example 1 0.57 3.68 16.5 41.51 Comparative Example 2 0.53 2.59 12.54 33.92 Comparative Example 3 0.52 2.21 7.16 20.54 Comparative Example 4 0.55 2.71 13.19 38.11 Example 1 0.48 1.56 6.16 19.34 Example 2 0.37 0.82 2.61 10.21 Example 3 0.39 1.38 5.12 12.86 Example 4 0.36 0.78 2.44 11.22 Example 5 0.31 0.72 2.05 6.21

Referring to Table 2 above, the particle sizes (PSA D10, PSA D50 and PSA D90) of the BTO prepared in Examples 1 to 5 were smaller than those of BTO prepared in Comparative Examples 1 to 4.

Evaluation example  2: Synthesized IT (K- factor  And c / a) evaluation

The crystallinity (k-factor and c / a) of BT synthesized in the above Examples and Comparative Examples was measured by XRD (D / Max 2000 series manufactured by Rigaku Co.) and the results are shown in Table 3 below. Specifically, the XRD analysis conditions of 40 kV, 200 mA at a rate of 2 sec / step and a step size of 0.02 were analyzed for the range of 2? = 44.5 to 46 degrees (?). Then, in the XRD spectrum as shown in Fig. 5, the k-factor of the BT particles was calculated as the ratio (I _t / I _c ) of the tetragonal fraction (I _t ) to the cubic phase fraction (I _c ). Also, the d-spacing values of the a-axis and the c-axis of the crystal lattice were calculated, and then the c / a of the BT particles was calculated by the ratio. The results are shown in Table 3 below. FIG. 5 shows XRD spectra of BT prepared in Examples 2, 5 and Comparative Example 3. FIG.

Evaluation example  3: Synthesized IT Particle size ( SEM D50 ) Measure

The particle diameters (SEM D50) of the BT after completion of drying obtained in the above Examples and Comparative Examples were measured, and the results are shown in Table 3 below. The particle size (SEM D50) was measured by scanning electron microscopy (SEM, JSM-7400F from Jeol Co.) using an image analysis program (Image Pro Plus ver. 4.5 from Mediacybernetics) And the number of barium titanate particles measured was 500 or more.

Evaluation example  4: Synthesized IT of Specific surface area  evaluation

The specific surface area of BT synthesized in each of the above Examples and Comparative Examples was analyzed by a specific surface area meter (Mountech Co., Macsorb HM-1220), and the results are shown in Table 3 below.

Evaluation example  5: Synthesized IT  Evaluation of the content of agglomerate in powder

The contents of agglomerates in the BT powders synthesized in the above Examples and Comparative Examples were analyzed, and the results are shown in Table 3 below. Specifically, 5 g of the BT powder synthesized in each of the above Examples and Comparative Examples was dispersed in 150 ml of ethanol to prepare a BT dispersion. Then, the BT dispersion was dispersed by using a metering pump (Masterflex, 7528-10S) Filter (stainless steel mesh) and filtered. Then, the content (W _R ) of the remaining material that did not pass through the filter was measured in units of 'g'. Then, the content of agglomerates was calculated according to the following equation (1).

[Equation 1]

Content of agglomerate (wt%) = W _R / 5 * 100

Crystallinity SEM D50
(nm) Specific surface area
(m ² / g) Content of agglomerates (wt%) k-factor c / a Comparative Example 1 3.90 1.0097 211 2.89 18.19 Comparative Example 2 4.74 1.0099 205 3.15 13.88 Comparative Example 3 5.18 1.0100 203 3.37 10.13 Comparative Example 4 4.18 1.0097 208 3.00 14.95 Example 1 5.62 1.0101 201 3.42 8.13 Example 2 6.99 1.0105 194 3.75 5.41 Example 3 5.84 1.0102 197 3.52 7.94 Example 4 6.90 1.0104 195 3.73 5.91 Example 5 7.84 1.0106 183 4.30 0.30

Referring to Table 3, the BT prepared in Examples 1 to 5 has a higher crystallinity (k-factor and c / a) and a smaller particle size (SEM D50) than the BT prepared in Comparative Examples 1 to 4, The specific surface area was large and the content of agglomerates was very small.

Evaluation example  6: BTO  Of powder SEM  evaluation

SEM photographs of BTO powder before and after dry pulverization were taken and the results are shown in Fig. (B) is a BTO powder after dry milling produced in Comparative Example 3, and (c) is a BTO powder after dry milling in Comparative Example 3, (B) is a BTO powder after dry milling as prepared in Example 2, and (d) is a BTO powder after dry milling as prepared in Example 5. Fig.

2, BTO powders ((c) and (d)) after dry milling prepared in Examples 2 and 5 were prepared by mixing BTO powder (a) before dry milling and BTO after dry milling The content of agglomerate was remarkably smaller than that of the powder ((b)).

Evaluation example  7: IT  Evaluation of photos of aggregates

The BT dispersion was prepared and filtered according to the evaluation example 5, and the remaining aggregate which could not pass through the filter was photographed. The results are shown in Fig. 3 (a) shows the BT powder before dry milling prepared in Examples 1 to 5 and Comparative Examples 1 to 4, and FIG. 3 (b) shows the BT powder after dry- (C) shows the case where the BT powder after dry milling prepared in Example 2 is used, and (d) shows the case where the BT powder after dry milling prepared in Example 5 is used.

3 (c) and (d)) of the BT powder after dry milling (a) prepared in Examples 2 and 5 and the BT powder (a) after dry grinding The content of agglomerate was remarkably smaller than that of the powder ((b)).

Evaluation example  8: IT  Of powder SEM  evaluation

SEM photographs of the BT powder prepared by heat-treating the BTO powder before and after dry pulverization were taken and the results are shown in FIG. 4 (a) is a BT powder prepared by directly heat-treating the BTO powder before dry grinding produced in Examples 1 to 5 and Comparative Examples 1 to 4, and (b) (C) is the BT powder prepared in Example 2, and (d) is the BT powder prepared in Example 5.

Referring to FIG. 4, the BT powders ((c) and (d)) prepared in Examples 2 and 5 were prepared by blending BT powder ((a)) prepared by directly heating the BTO powder before dry pulverization Compared with the BT powder ((b)) prepared in Example 3, the particle size was similar but the amount of aggregate was remarkably small.

Although the present invention has been described with reference to the drawings and embodiments, it is to be understood that various modifications and equivalent embodiments may be made by those skilled in the art. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

10: electrode layer 20, 20 ': dielectric layer

Claims (10)

Barium compound solution, titanium compound solution and oxalic acid solution (raw material solution preparation step);
(BTO synthesis) of barium titanyl oxalate [BaTiO (C ₂ O ₄ ) ₂ .4H ₂ O] (hereinafter simply referred to as BTO) by bringing the barium compound solution and the titanium compound solution into contact with the oxalic acid solution, step);
Wet pulverizing the synthesized BTO (BTO wet pulverization step);
Drying the wet pulverized BTO to obtain a BTO powder (BTO drying step); And
And dry-milling the dried BTO (BTO dry milling step)
Wherein the BTO dry grinding step is carried out until the bulk density of the dry pulverized BTO is from 0.2 g / cm ³ to 0.50 g / cm ³ or less. The method according to claim 1,
The barium compound solution is prepared by dissolving at least one barium compound selected from the group consisting of barium chloride (BaCl ₂ ), barium nitrate (Ba (NO ₃ ) ₂ ) and barium perchlorate (Ba (ClO ₄ ) ₂ ) Wherein the titanium compound solution is prepared by dissolving at least one titanium compound selected from the group consisting of titanium oxychloride (TiOCl ₂ ) and titanium tetrachloride (TiCl ₄ ) in water, and the oxalic acid solution is prepared by dissolving oxalic acid in water ≪ / RTI > barium titanyl oxalate. The method according to claim 1,
Wherein the BTO synthesis step is carried out at a synthesis temperature of from 20 to 100 < 0 > C. The method according to claim 1,
Wherein the BTO dry pulverization step is carried out using at least one pulverizer selected from the group consisting of a hammer mill, an airflow classifier (ACM) and a jet mill. The method according to claim 1,
Wherein the dry-milled BTO has a particle size (PSA D50) of 2.5 占 퐉 or less and a particle size (PSA D90) of 8.0 占 퐉 or less. The method according to claim 1,
Between the BTO synthesis step and the BTO wet grinding step,
Aging the synthesized BTO;
Filtering the aged BTO; And
Further comprising washing the filtered BTO with excess water. ≪ RTI ID = 0.0 > 11. < / RTI > (BT synthesis step) of synthesizing barium titanate [BaTiO ₃ ] (hereinafter simply referred to as BT) by heat-treating BTO prepared according to any one of claims 1 to 6 at 800 to 1000 ° C. Process for the preparation of barium titanate. 8. The method of claim 7,
Further comprising, after the BT synthesis step, grinding the synthesized BT (BT grinding step). A barium titanate produced by the method of claim 7. 10. The method of claim 9,
And barium titanate powder comprising barium titanate in an amount of 10 wt% or less.

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