KR100558460B1 - A Method for Producing the Barium Titanate Based Powder by Oxalate Process - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to barium titanate based powders used in various fields, such as ferroelectrics and piezoelectrics, and a method for producing the same, and the object thereof is a barium titanate powder having a uniform particle size and having an ultrafine particle size. It is intended to provide.

This invention makes the summary the ultrafine barium titanate powder which has the following structural formula, and its manufacturing method.

[constitutional formula]

ABO ₃

[Wherein O represents oxygen, A is one or two or more of the additives that may be substituted with Ba and Ba, B is one or two or more of the additives that may be substituted with Ti and Ti, and A / Mole ratio of B> 1]

According to the present invention, a perovskite barium titanate-based powder can be provided that can be usefully used as a dielectric material such as MLCC and the like due to its ultrafine and excellent dielectric properties.

Ultra fine, barium titanate, oxalate, additives,

Description

A method for producing the barium titanate based powder by oxalate process

1 is a manufacturing process of the conventional barium titanate powder

2 is a manufacturing process diagram of the barium titanate-based powder according to the present invention

3 is a barium titanate system prepared according to the present invention SEM histogram after calcination of the powder.

Figure 4 is a SEM histological picture after calcination of the other barium titanate-based powder prepared by the present invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a barium titanate based powder used in various fields such as ferroelectrics and piezoelectrics, and to a method of manufacturing the same by a oxalate process, and more particularly, to barium titanate based ultrafine particles. powder) and a method for producing the same by an oxalate process.

In general, barium titanate-based powder is an important component of electronic ceramics with ferrite as a ferroelectric material.

For example, barium titanate-based powders are widely used as raw materials for multilayer ceramic chip capacitors (MLCCs), positive temperature coefficients of thermistors, and piezoelectric materials.

Conventionally, such barium titanate-based powders have been prepared by a dry process of mixing component powders and heating the mixture at a high temperature to induce a solid phase reaction.

The powders thus obtained usually require high temperature firing to form agglomerates with irregular shapes to achieve the desired properties.

As electronic components such as MLCCs increasingly require smaller and larger capacities, the production of powders with uniform, fine and narrow particle size distribution becomes very important.

Therefore, barium titanate-based powders are now produced by wet processes such as hydrothermal synthesis, coprecipitation (oxalate method), alkoxide method (sol-gel method) and the like.

The hydrothermal synthesis method, despite the advantages that the properties of the powder is good, the synthesis process is complex, the productivity is not good because of the use of the autoclave (autoclave), the price of the powder produced is expensive.

In addition, the alkoxide method is also difficult to handle the starting material and expensive.

For this reason, barium titanate-based powders are mainly produced by the oxalate method.

The oxalate method has the advantages of high purity and excellent reproducibility compared to the powder produced by a dry process or another wet process.

The oxalate method has been developed by Clabaugh ["Preparation of Barium Titanyl Oxalate Tetrahydrate for Conversion to Barium Titanate of High Purity", Journal of Research of the National Bureau of Standards, vol. 56, No. 5, pp. 289-291, 1956, which is currently used for commercialization of barium titanate powder production.

1, the manufacturing process by the said oxalate method is shown schematically. As shown in Fig. 1, the oxalate method is obtained by adding a mixed solution containing Ba and Ti ions to oxalic acid to form barium titanyl oxalate ([BaTiO (C ₂ O ₄ ) ₂ .4H). ₂ O]; Hereafter, only 'BTO') is precipitated, followed by drying and pyrolysis to prepare barium titanate powder.

That is, as shown in Figure 1, the barium chloride and titanium chloride aqueous solution is mixed so that the Ba: Ti ratio is 1: 1, and when added to oxalic acid, BTO precipitates, which is washed well, filtered and dried to about 800 Pyrolysis at 占 폚 gives barium titanate powder.

However, the oxalate method has been commercialized first because of its simple process and low cost of raw materials and equipment investment, but it is difficult to control the particle size and forms a strong aggregate between particles during pyrolysis. There is a disadvantage of being.

In addition, there is a problem that a lot of fine particles are generated, not only good dispersibility during mixing and molding, but also poor sinterability during sintering and abnormal grains are not suitable for application to ultra-thin MLCC.

As another method for overcoming this problem, Hennings et al. Proposed a method for preparing new barium titanate powder in US Pat. No. 5,009,876.

In this method, the mixing order is changed in the method proposed by Clabaugh, and the aqueous oxalic acid solution and TiOCl ₂ solution are mixed first, and then the aqueous barium chloride solution is added thereto, and the reaction temperature is maintained at about 55 ° C. And a condensed barium titanate having a size of 3 to 30 µm.

As another example similar to the method of Hennings et al., Wilson et al. Proposed a new improved method for producing barium titanate powder by converting a source of Ba from aqueous barium chloride solution to barium carbonate in US Pat. No. 5,783,165.

In addition, Yamamura et al. Dissolve oxalic acid in ethanol instead of water to obtain particulate precipitate by Clabaugh et al. ["Preparation of Barium Titanate by Oxalate Method in Ethanol Solution", Ceramic International, vol. 11, No. 1, pp. 17-22, 1985, Cho et al., Also changed the aging solvent and time of sediment solution in the Clabaugh method to obtain particulate barium titanate ["Particle Size Control of Barium Titanate Prepared from Barium Titanyl Oxalate", Journal of the American Ceramic Society, vol. 80, no. 6, pp. 1599-1604, 1997.

However, these methods are not enough to fundamentally solve the problem that the powder is agglomerated severely during the manufacturing process of barium titanate. Therefore, due to the strong coagulation between the particles, the particles cannot be greatly increased, and the crystallinity is also poor, resulting in poor X7R or Y5V characteristics. Not suitable for MLCC.

In particular, reducing the particle size by adjusting the process conditions has more process variables, which may cause problems in reproducibility.

Techniques for improving the above problems are presented in Korean Patent Application No. 2001-0035131.

That is, Korean Patent Application No. 2001-0035131 discloses a method for producing barium titanate powder having a particle size control and uniform particle shape by pulverizing BTO prior to pyrolysis and then performing pyrolysis or mixing an additive substituted in place of Ba or Ti. in this has been proposed, ABO ₃ structure a mixture of the additive is in the form of _{Ba (Ti 1-Z Zr Z} ) O 3, (Ba 1-X Ca X) (Ti 1-Z Zr Z) O 3 a / B ( The additive is added to A (Ba site) or B (Ti site) while maintaining mole ratio) = 1.

However, the above method has a limitation in producing ultrafine barium titanate powder of 0.3 μm or less, which is difficult to control uniform particle size by the simple pulverization process before the heat treatment or the above-mentioned additive mixing method and corresponds to the ultra thin layer MLCC. There is this.

The present inventors conducted research and experiments to solve the above problems of the prior art, and based on the results, the present invention proposes the present invention, which provides a uniform particle size and ultrafine barium titanate-based powder. The purpose is to do that.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

The present invention relates to an ultrafine barium titanate powder having the following structural formula.

[constitutional formula]

ABO ₃ [wherein O represents oxygen, A is one or two or more of the additives that may be substituted with Ba and Ba, B is one or two or more of the additives that may be substituted with Ti and Ti, and Mole ratio of A / B> 1]

In addition, the present invention comprises the steps of adding a mixed aqueous solution of barium chloride and titanium chloride to the aqueous solution of oxalic acid to precipitate BTO;

Separating the precipitated BTO;

Pulverizing the BTO to prevent the separated BTO from agglomerating after the pyrolysis process;

ABO ₃ during or after the pulverization of BTO, wherein O represents oxygen, A is one or two or more of the additives that may be substituted with Ba and Ba, and B is one of the additives that may be substituted with Ti and Ti. 1 or 2 or more of an additive group which may be substituted with Ba, and an additive group which may be substituted with Ti, to obtain a barium titanate-based powder having a structural formula of A / B mole ratio> 1. Adding species or two or more;

Pyrolyzing the BTO to which the additive is added as described above to form a barium titanate-based powder; And

It relates to a method for producing ultra-fine barium titanate-based powder by the oxalate process comprising the step of pulverizing the barium titanate-based powder formed above.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The ultrafine barium titanate-based powder of the present invention has a composite perovskite structural formula as follows, and has an ultrafine grain, preferably a particle size of 0.3 m or less.

[constitutional formula]

ABO ₃

In the above structural formula, O represents oxygen, and A represents one or two or more of the additives that may be substituted with Ba and Ba, and preferred additives that may be substituted with Ba include Mg, Ca, Sr, and Pb. And the like.

In the above structural formula, B represents one or two or more of the additives that may be substituted with Ti and Ti, and preferred additives that may be substituted with Ti include Zr, Hf, and Sn.

The addition amount of the additive which may be substituted with Ba is preferably set to 15 mol% or less, and the addition amount of the additive which may be substituted with Ti is preferably set to 30 mol% or less.

In addition, the mole ratio of A / B in the above structural formula should satisfy the mole ratio of A / B> 1.

The ultrafine barium titanate-based powder of the present invention includes (BaCa _X ) TiO ₃ , (Ba _1-X Ca _X ) _{1 + Z} (Ti _1-Y Zr _Y ) O ₃ , (Ba _1-XC Ca _X Sr _C ) _{1 + Z} (Ti _1-Y Zr _Y ) O ₃ , (BaCa _X ) _{1 + Z} (Ti _1-Y Zr _Y ) O ₃ [0 <x ≤15 mol%, 0≤y≤50 mol%, 0 < z ≦ 15 mol%, 0 ≦ c ≦ 15 mol%] and the like, and barium titanate-based powder having a composite perovskite structure.

The composite perovskite barium titanate-based powder according to the present invention is very suitable as a dielectric material of MLCC satisfying X5R, X7R (A, B characteristics) and Y5V (F characteristics).

Hereinafter, a method for producing ultrafine barium titanate-based powder according to the present invention will be described.

The manufacturing process according to the invention is shown in FIG.

As shown in FIG. 2, in the manufacturing process of the barium titanate powder of the present invention, first, an aqueous barium chloride solution and an aqueous titanium chloride solution are added to an aqueous oxalic acid solution to precipitate BTO. At this time, it is preferable that the barium chloride aqueous solution and the titanium chloride aqueous solution are mixed well so that the molar ratio of barium chloride to titanium chloride is about 1: 1 to 1: 1.5.

As a specific example, an aqueous barium chloride solution is usually used by dissolving BaCl ₂ · 2H ₂ O in water, with a preferred concentration range of about 0.2-2.0 mol / l.

In addition, the aqueous titanium chloride solution is usually diluted with a TiCl ₄ solution, the preferred concentration range is about 0.2-2.0 mol / L.

It is preferable to use the oxalic acid aqueous solution which has a density | concentration of about 0.2-5.0 mol / L, and also the thing whose temperature is about 20-100 degreeC.

In addition, when the mixed barium chloride solution and titanium chloride solution are added to the oxalic acid solution, the addition rate is about 1-20 ml / min when dropped into a burette, and about 10 to 500 when in the form of a nozzle. It is preferably ml / min.

The precipitated BTO is then separated to obtain BTO.

At this time, the separation may be performed after aging, washed with water and filtered to obtain BTO. It is preferable to perform the said aging about 1-100 hours.

Next, in the present invention, the BTO is pulverized in order to prevent aggregation of the BTO in the pyrolysis process.

It is important to grind the BTO before pyrolysis.

ABO ₃ during or after the pulverization of BTO, wherein O represents oxygen, A is one or two or more of the additives that may be substituted with Ba and Ba, and B is one of the additives that may be substituted with Ti and Ti. 1 or 2 or more of an additive group which may be substituted with Ba, and an additive group which may be substituted with Ti, to obtain a barium titanate-based powder having a structural formula of A / B mole ratio> 1. Add species or two or more.

Preferred additives that may be substituted with Ba in the above structural formula include Mg, Ca, Sr, and Pb, and preferred additives that may be substituted with Ti include Zr, Hf, and Sn.

The addition amount of the additive which may be substituted with Ba is preferably set to 15 mol% or less, and the addition amount of the additive which may be substituted with Ti is preferably set to 30 mol% or less.

The elements are introduced after or during the grinding of the above-mentioned BTO in the form of oxides, carbonates, nitrides and chlorides.

In the present invention, the pulverization before pyrolysis may be performed by any kind of pulverization.

That is, the pulverizer may include a planetary mill, an attribution mill, a ball mill, a bead mill, a dyno mill, a nano mill, or the like. It may be one of wet grinding or may be one of dry grinding such as an atomizer, a jet mill, or the like.

It is important to make the average particle diameter of BTO after grinding | pulverization into 5 micrometers or less, Preferably it is the range of 0.1-3 micrometers.

It is preferable to perform grinding before the thermal decomposition by wet grinding.

The wet grinding is most suitable for bringing the average particle diameter of the BTO to about 5 μm or less.

To this end, the wet grinding is preferably performed by adding water at least twice or more by weight to the precipitate.

A small amount of dispersant may be added so that the precipitate of BTO is more easily dispersed in water, in which case the amount of water may be reduced.

In the case of wet grinding as described above, the wet-pulverized BTO slurry is dried, and the drying method is not particularly limited, and any method may be used as long as it is a commonly used method.

The preferred drying method is the spray dry method.

The spray drying method is a method of hot air drying while dropping the BTO slurry precipitated in a spray dryer onto a disk that rotates at high speed.

The preferred rotational speed of the disk is about 5,000-20,000 rpm.

In addition, the drying temperature during the hot air drying is set to at least 100 ℃ or more, preferably about 100 ~ 450 ℃.

Next, the barium titanate-based powder is prepared by calcining, that is, thermally decomposing BTO, to which additives are added and dried as described above.

At this time, it is preferable to maintain the heating rate at a temperature of about 700-1200 ° C. at about 0.5-10 ° C./min during pyrolysis.

Next, the pyrolyzed barium titanate-based powder is pulverized by a conventional method to produce ultrafine barium titanate-based powder having 0.3 µm or less.

The ultrafine barium titanate-based powder includes (BaCa _X ) TiO ₃ , (Ba _1-X Ca _X ) _{1 + Z} (Ti _1-Y Zr _Y ) O ₃ , (Ba _1-XC Ca _X Sr _C ) _{1+ Z} (Ti _1-Y Zr _Y ) O ₃ , (BaCa _X ) _{1 + Z} (Ti _1-Y Zr _Y ) O ₃ [0 <x ≤15 mol%, 0≤y≤50 mol%, 0 <z≤ 15 mol%, 0 ≦ c ≦ 15 mol%] and the like, and barium titanate-based powder having a composite perovskite structure.

The barium titanate powder thus obtained has ultrafine powder with a particle size of 0.3 μm or less, a very uniform particle size, a morphology close to a spherical shape, and a low content of chlorine ions in the powder. Therefore, it is very suitable as a dielectric material of MLCC which satisfies X5R, X7R (A and B characteristics) and Y5V (F characteristics).

Hereinafter, the present invention will be described in more detail with reference to Examples.

However, of course, the scope of the present invention is not limited thereto.

For example, the type of additive added to barium titanate may be simply changed depending on the type of dielectric to be obtained.

Example 1

1.6 liters of 0.5 mol / l TiCl ₄ aqueous solution and 0.84 liters of 1 mol / l BaCl ₂ aqueous solution are mixed well to make a mixed solution, and it is added dropwise to 5.0 liters of 0.5 mol / l concentration of oxalic acid with stirring. Added.

At this time, the temperature of the oxalic acid solution was 70 ~ 80 ℃, was added to adjust the rate at 1 ~ 10ml / min.

Then, after maintaining the reaction for about 30 to 60 minutes, stirring was stopped and air cooled to obtain a BTO precipitate, which was then aged for about 5 hours.

Next, the BTO precipitate solution obtained above was washed with water and filtered to obtain a BTO precipitate.

The BTO precipitate obtained as described above was pulverized with a bead mill in a slurry state in which about 5 times of water was added to the precipitate so that the average particle diameter thereof was 0.5 μm or less, and dried by hot air.

CaCO ₃ additive and 1.5 times of water were added to the pulverized BTO powder, mixed using a planetary mill, dried, and then thermally decomposed at 950 to 1050 ° C. as shown in Table 1 below. And (BaCa _X ) TiO ₃ [x = 1,2,5 mol% Ca] powder was prepared by milling.

The average particle size of each composite perovskite powder thus prepared was measured, and the results are shown in Table 1 below.

In addition, SEM micrographs of the powder calcined at 1050 ° C. in the powder of Table 1 were observed, and the results are shown in FIG. 3.

division Powder composition A / B molar ratio Calcination Temperature (℃) Average particle size (㎛) Conventional example BaTiO ₃ 1.00 950 0.287 1000 0.286 1050 0.363 Inventive Example 1 (BaCa _0.01 ) TiO ₃ 1.01 950 0.168 1000 0.238 1050 0.242 Inventive Example 2 (BaCa _0.02 ) TiO ₃ 1.02 950 0.162 1000 0.157 1050 0.212 Inventive Example 3 (BaCa _0.05 ) TiO ₃ 1.05 950 0.164 1000 0.126 1050 0.212

As shown in Table 1 above. It can be seen that the average particle size of the powder decreases after calcination as the content of the additive which may be substituted with Ba increases.

In addition, as shown in Figure 3, the powder produced according to the present invention can be seen that the particle size distribution is uniform ultrafine powder.

(Example 2)

Via BaCO ₃ and ZrO ₂ additive, and the same procedure as in Example 1 except that a mixture with a, planetary mill (planetary mill) followed by the addition of 1.5 times the water BTO powder preparation for pulverized BTO powder Ba _x ( Ti _1-y Zr _y ) O ₃ [x, y = 1,2,5 mol%] powder was prepared.

The average particle size of each composite perovskite powder thus prepared was measured, and the results are shown in Table 2 below.

In addition, SEM micrographs of the powder calcined at 1050 ° C. in the powder of Table 1 were observed, and the results are shown in FIG. 4.

division   Powder composition A / B molar ratio Calcination Temperature (℃) Average particle size (㎛) Inventive Example 4 Ba _1.01 (Ti _0.99 Zr _0.01 ) O ₃ 1.01 950 0.256 1000 0.265 1050 0.324 Inventive Example 5 Ba _1.02 (Ti _0.98 Zr _0.02 ) O ₃ 1.02 950 0.283 1000 0.213 1050 0.259 Inventive Example 6 Ba _1.05 (Ti _0.95 Zr _0.05 ) O ₃ 1.05 950 0.261 1000 0.233 1050 0.219

As shown in Table 2 above. As the content of the additive that can be substituted with Ti increases, the average particle size of the powder decreases after calcination.

In addition, as shown in Figure 4, the powder produced in accordance with the present invention can be seen that the particle size distribution is a uniform ultra fine powder.

(Example 3)

After mixing the X5R composition additive in each 1050 ℃ calcined powder prepared in Example 1 to prepare K2, and then measured the overall dielectric properties, and the results are shown in Table 3 below.

division   Powder composition A / B molar ratio permittivity Dielectric loss (%) Insulation resistance (10 ¹² Ω) TCC (%) (at 85 ° C) Conventional example BaTiO ₃ 1.00 2420 0.95 6.78 -9.87 Inventive Example 1 (BaCa _0.01 ) TiO ₃ 1.01 2318 0.94 7.59 -8.55 Inventive Example 2 (BaCa _0.02 ) TiO ₃ 1.02 2116 0.94 7.42 -6.44 Inventive Example 3 (BaCa _0.05 ) TiO ₃ 1.05 2151 0.93 7.11 -6.13

As shown in Table 3 above, in the case of using a powder prepared by adding an additive to BTO such that A / B> 1 according to the present invention [Invention Examples (1), (2) and (3)], MLCC X5R It can be seen that the characteristics are well satisfied.

(Example 4)

After mixing the X5R composition additive in each 1050 ℃ calcined powder prepared in Example 2 to prepare K2, and then measured the overall dielectric properties, and the results are shown in Table 4 below.

division    Powder composition A / B molar ratio permittivity Dielectric loss (%) Insulation resistance (1012Ω) TCC (%) (at 85 ° C) Inventive Example 4 Ba _1.01 (Ti _0.99 Zr _0.01 ) O ₃ 1.01 2455 0.97 6.54 -10.12 Inventive Example 5 Ba _1.02 (Ti _0.98 Zr _0.02 ) O ₃ 1.02 2324 0.97 6.71 -10.55 Inventive Example 6 Ba _1.05 (Ti _0.95 Zr _0.05 ) O ₃ 1.05 2196 0.95 6.13 -9.88

As shown in Table 4, when using the powder prepared by adding the additive to the BTO to A / B> 1 according to the present invention it can be seen that the MLCC X5R properties are well satisfied.

 As described above, in the present invention, in the conventional method of mixing the additive after crushing BTO, the additive is added so that the A / B molar ratio is> 1. It is effective to provide perovskite barium titanate-based powder which can be very usefully used as a dielectric material.

Claims (9)

delete delete delete Adding a mixed aqueous solution of barium chloride and titanium chloride to an aqueous oxalic acid solution so that BTO precipitates; Separating the precipitated BTO; Pulverizing the BTO to prevent the separated BTO from agglomerating after the pyrolysis process; ABO ₃ during or after the pulverization of BTO, wherein O represents oxygen, A is one or two or more of the additives that may be substituted with Ba and Ba, and B is one of the additives that may be substituted with Ti and Ti. 1 or 2 or more of an additive group which may be substituted with Ba, and an additive group which may be substituted with Ti, to obtain a barium titanate-based powder having a structural formula of A / B mole ratio> 1. Adding species or two or more; Pyrolyzing the BTO to which the additive is added as described above to form a barium titanate-based powder; And Method for producing ultrafine barium titanate-based powder by oxalate process comprising the step of pulverizing the barium titanate-based powder formed above The additive according to claim 4, wherein the additive which may be substituted with Ba is one or two or more selected from the group consisting of Mg, Ca, Sr, and Pb, and the additive which may be substituted with Ti is Zr, Hf, and Sn. Method for producing ultrafine barium titanate-based powder by oxalate process, characterized in that at least one selected from the group consisting of The ultrafine barium titanate-based powder obtained by the oxalate process according to claim 5, wherein the amount of the additive which may be substituted with Ba is 15 mol% or less, and the amount of the additive which may be substituted with Ti is 30 mol% or less. Manufacturing Method The ultrafine barium titanate system according to any one of claims 4 to 6, wherein the separation of the precipitated BTO is performed by aging, washing, and filtering the precipitated barium titanate oxalate. Preparation method of powder The method for producing ultrafine barium titanate-based powder according to any one of claims 4 to 6, wherein pulverization of the precipitate before the pyrolysis is performed by wet pulverization. The ultrafine barium titanate according to any one of claims 4 to 6, wherein the precipitated barium titanate oxalate prior to pyrolysis is pulverized to have an average particle diameter of 0.1 to 5 탆. Manufacturing method of system powder

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