KR20140063691A - Method for producing barium titanyl oxalate and method for producing barium titanate - Google Patents

Abstract

An object of the present invention is to provide a method for producing barium titanyl oxalate which can obtain barium titanate having excellent crystallinity despite its small particle size by the oxalate method. Another object of the present invention is to provide a method for producing barium titanate which is fine and has excellent crystallinity. The present invention is a method for producing barium titanyl oxalate, wherein an aqueous solution (liquid B) containing titanium tetrachloride is added to a solution (liquid A) containing at least oxalic acid and barium chloride, The liquid is preferably obtained by contacting oxalic acid and barium chloride in a water solvent.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a barium titanyl oxalate compound, a barium titanyl oxalate compound, a barium titanyl oxalate compound, a barium titanyl oxalate compound,

The present invention relates to a method for producing barium titanyl oxalate useful as a raw material for functional ceramics such as piezoelectric materials, optoelectronics materials, dielectrics, semiconductors and sensors, and a method for producing barium titanate using the same.

Conventionally, barium titanate is produced by a solid phase method, a hydrothermal synthesis method, an alkoxide method, an oxalate method, or the like.

As the solid phase method, since the powder is formed by the dry method in which the constituent raw powder or the like is mixed and the mixture is heated at a high temperature, the obtained powder forms an aggregate form exhibiting an irregular shape and requires high temperature firing Do. In addition, the hydrothermal synthesis method is complicated in the synthesis process, despite the advantages of good powder characteristics, and the productivity is lowered due to the use of the autoclave, the production cost is high, and it is not industrially advantageous. In addition, the alkoxide process is similarly difficult to handle starting materials, is expensive, and is not industrially advantageous.

Barium titanate obtained by the oxalate method is characterized in that it can be produced at low cost and has a uniform composition as compared with the hydrothermal synthesis method and the alkoxide method and has a uniform composition as compared with barium titanate produced by the solid phase method. As a conventional oxalate method, a method in which an aqueous solution of TiCl ₄ and BaCl _{2 is added} dropwise to an aqueous solution of H ₂ C ₂ O ₄ with stirring to obtain barium titanyl oxalate and the barium titanyl oxalate is baked (for example, See Non-Patent Document 1 and Patent Document 1).

Japanese Patent Application Laid-Open No. 2005-500239

 W. S. Clabaugh et al., J. Res. Nat.Bur.Stand., 56 (5), 289-291 (1956)

Barium titanate obtained by the oxalate method exhibits excellent performance as a material of dielectric ceramics, but further performance improvement is demanded from the recent increase in required performance. Barium titanate is generally known to have high crystallinity and good dielectric properties as a dielectric ceramic (for example, see Japanese Patent Laid-Open No. 2006-117446).

The inventors of the present invention have studied barium titanyl oxalate obtained by a conventional method. The barium titanyl oxalate has a bulk Ba / Ti molar ratio of about 0.998 to 1.002, and the Ba / Ti molar ratio per grain size varies (I.e., the smaller the specific surface area), the smaller the Ba / Ti molar ratio and the larger the particle size (in other words, the smaller the specific surface area), the smaller the Ba / Ti molar ratio And the like. Therefore, it has been found that the oxalate method is difficult to obtain barium titanate having a small grain size and a Ba / Ti molar ratio of approximately 0.998 to 1.002, which is high in crystallinity.

Therefore, an object of the present invention is to provide a method for producing barium titanyl oxalate which can obtain barium titanate having excellent crystallinity despite its small particle size by the oxalate method. Another object of the present invention is to provide a method for producing barium titanate which is fine and has excellent crystallinity.

As a result of intensive studies in view of the above circumstances, the present inventors have found that an aqueous solution (solution B) containing titanium tetrachloride is added to a solution (solution A) containing at least oxalic acid and barium chloride, Barium titanyl oxalate having a Ba / Ti molar ratio of 0.998 to 1.002 is obtained even with a fine particle having a particle size of 4 탆 or less and that barium titanyl oxalate can be used to form barium titanate A dielectric ceramic material having excellent performance can be provided, and the present invention has been accomplished.

That is, a first invention to be provided by the present invention is a barium oxalate solution (barium oxalate solution) characterized in that an aqueous solution (solution B) containing titanium tetrachloride is added to a solution containing at least oxalic acid and barium chloride Lt; / RTI >

The second invention to be provided by the present invention is a method for producing barium titanate, which comprises firing barium titanyl oxalate obtained by the first invention.

Hereinafter, the present invention will be described based on its preferred embodiments.

The production method of the present invention is characterized in that an aqueous solution (solution B) containing titanium tetrachloride is added to a solution (solution A) containing at least oxalic acid and barium chloride to carry out the reaction. The barium titanyl oxalate produced according to the production method of the present invention preferably has a molar ratio of Ba to Ti (hereinafter referred to as "Ba / Ti molar ratio") of 0.998 to 1.002, preferably about 1, The fine barium titanyl oxalate has an average particle diameter of 4 탆 or less, preferably 0.1 to 4 탆, determined by the scattering method.

Solution A used in the present invention is a solution containing at least oxalic acid and barium chloride. The liquid A according to the present invention may contain a chlorine ion source such as barium oxalate, furthermore hydrochloric acid, as a component other than water, oxalic acid and barium chloride. The mixing ratio of oxalic acid and barium chloride in solution A or oxalic acid, barium chloride and barium oxalate, and furthermore, chlorine ion source to solution A is such that the concentration of oxalic acid and barium in solution A and the molar ratio of oxalic acid and barium, When the chloride ion concentration is within the range described later, the compounding ratio of each raw material is not particularly limited.

The composition of the liquid A is 0.7 to 2.5 mol / L, preferably 1.0 to 2.2 mol / L in terms of oxalic acid (H ₂ C ₂ O ₄ ) and 0.4 to 1.3 mol / L, preferably 0.9 to 1.1 Mol / L, and the molar ratio of oxalic acid to oxalic acid (oxalic acid / Ba) is from 1.5 to 2.5, preferably from 1.8 to 2.2, from the viewpoint that barium titanyl oxalate having a Ba / Ti molar ratio of about 1 is obtained at a high yield . The barium titanyl oxalate having a Ba / Ti molar ratio of about 1 at a high yield can be obtained when the chloride ion concentration in the liquid A is 0.7 to 2.5 mol / L, preferably 1.0 to 2.2 mol / L in terms of Cl .

The liquid A according to the present invention can be obtained by contacting oxalic acid with barium chloride in a water solvent. Normally, when oxalic acid and barium chloride are brought into contact with each other in a water solvent, a part of oxalic acid and barium chloride react with each other to precipitate fine barium oxalate. In this case, the composition of the liquid A is one containing water, oxalic acid, barium chloride, furthermore, barium oxalate and hydrochloric acid as other components, but in the present production method, the liquid A thus prepared has a reactivity with titanium tetrachloride Is particularly preferably used from the viewpoint of obtaining a desired barium titanyl oxalate at a high yield. The mixing ratio of oxalic acid and barium chloride may be such that the concentration of oxalic acid and barium in solution A and the molar ratio of oxalic acid and barium, as well as the chloride ion concentration, fall within the above range.

The contact between the oxalic acid and barium chloride with respect to the production of the liquid A is carried out with stirring to obtain a suspension in which the precipitated fine barium oxalate is uniformly dispersed. The contact temperature is not particularly limited, and in many cases, 100 占 폚 or lower, preferably around room temperature (15 to 30 占 폚) is sufficient. The contact time of oxalic acid and barium chloride in the production of the liquid A is not particularly limited, but in many cases, the liquid A of satisfactory physical properties is obtained in 0.25 hours or more, preferably 0.5 to 2 hours.

As a method for contacting oxalic acid with barium chloride, for example, 1) a method of adding barium chloride as an aqueous solution or a powder to an oxalic acid aqueous solution, 2) a method of adding oxalic acid as an aqueous solution or a powder to an aqueous barium chloride solution, 3) A method in which oxalic acid and barium chloride are added to the charged container, and 4) a method in which water is added to a vessel into which oxalic acid and barium chloride have been charged. However, a method suitably advantageous in consideration of the apparatus, operability and the like may be selected .

The liquid B used in the present invention is an aqueous solution containing titanium tetrachloride. The concentration of titanium tetrachloride in the liquid B is preferably from 0.1 to 1.2 mol / L, particularly from 0.3 to 1.0 mol / L as Ti from the viewpoint of obtaining a barium titanyl oxalate having a Ba / Ti molar ratio of about 1 at a high yield. The chlorine ion concentration in the liquid B is 0.7 to 2.5 mol / L, preferably 1.0 to 2.2 mol / L in terms of Cl, in a high yield, in the form of fine particles, and a Ba / Ti molar ratio of approximately 1, barium titanyl oxalate From the viewpoint of obtaining the above.

In the present manufacturing method, the ratio of the concentration of the chloride ion in the liquid B to the concentration of the chloride ion in the liquid A (B / A) is preferably 0.5 to 5.0, The barium titanyl oxalate titanyl oxalate having a finer Ba / Ti molar ratio of 0.998 to 1.00, preferably about 1 can be easily obtained by adjusting the solution A and the solution B so that the ratio is 0.75 to 3.0.

A chlorine ion source may be added to the liquids A and B to adjust the concentration of the chlorine ions. Examples of the chlorine ion source include organic compounds including hydrochloric acid, sodium chloride, potassium chloride, lithium chloride, and chloride ions.

In the reaction operation, the solution B is added to the solution A to carry out the reaction. The addition of the liquid B to the liquid A is carried out so that the molar ratio of the barium atom to the titanium atom in the reaction liquid after addition is 1.0 to 1.5, particularly 1.1 to 1.3, so that the barium titanyl oxalate titanyl Is obtained at a high yield.

The faster the addition speed of the liquid B is, the more nuclei are generated per unit time and the more finer the liquid is obtained. The addition rate is appropriately selected depending on the size of the reaction vessel, the amount of the reaction solution and the like. For example, at the laboratory level of 0.5 L scale, the addition rate of the B liquid is 5 L / hour or more, preferably 8 to 11 L / .

The addition temperature of the liquid B to the liquid A is 40 占 폚 or lower, preferably 25 to 40 占 폚. In the oxalate method, in many cases, this addition temperature is carried out at a temperature of 50 DEG C or higher, but in the present production method, by decreasing the addition temperature to 40 DEG C, elution of Ba from the resulting barium titanyl oxalate is suppressed, and fine barium oxalate The change in the molar ratio of titanyl can be suppressed, so that it becomes easy to obtain a Ba / Ti molar ratio closer to 1. The temperature of the liquid B is not particularly limited, but is preferably within the same range as the temperature of the liquid A, because the reaction operation becomes easy.

The addition of the liquid B to the liquid A is preferably carried out with stirring. In the present production method, a strong reaction is performed by intensifying the stirring, thereby suppressing the nucleation and tending to obtain a more differential product. The stirring speed is appropriately selected depending on, for example, the size of the reaction vessel, the diameter of the stirring blade, the amount of the reaction solution and the like. For example, with reference to the laboratory level of 0.5 L scale, Or more, and the peripheral speed of the stirring blade is particularly preferably 1.6 to 1.8 m / sec.

After completion of the addition of the liquid B, it is preferable to perform aging to obtain barium titanyl oxalate in a high yield. Although the aging temperature is not particularly limited, it is preferable that the aging temperature is the same as the reaction temperature because it is easy to operate. The aging time is not particularly limited, but in many cases, it is 0.5 hour or more, preferably 0.5 to 2 hours. After completion of aging, solid-liquid separation is carried out by a conventional method, followed by washing with water. The washing method is not particularly limited. Repulping or the like is preferable because the cleaning efficiency is good. Subsequently, the barium titanyl oxalate is obtained by drying and, if necessary, pulverizing or pulverizing.

Preferable physical properties of the barium titanyl oxalate thus obtained are an average particle diameter of 4 탆 or less, preferably 0.1 to 4 탆, determined by laser diffraction / scattering. In addition, the composition of the barium titanyl oxalate has a Ba / Ti molar ratio of 0.998 to 1.002, preferably approximately 1.

The barium titanyl oxalate obtained by the production method of the present invention can be preferably used as a raw material for producing barium titanate ceramics of a dielectric ceramic material. The method for producing barium titanate of the present invention is as follows.

The method for producing barium titanate of the present invention is characterized by calcining barium titanyl oxalate obtained by the above-mentioned method.

The organic material derived from oxalic acid contained in the final product is undesirable because it deteriorates the dielectric characteristics of the material and becomes an unstable factor in the thermal process for the ceramicization. Therefore, in the present invention, barium titanyl oxalate is thermally decomposed by firing to obtain the desired barium titanate, and at the same time, it is necessary to sufficiently remove the organic material derived from oxalic acid. The firing conditions are preferably a firing temperature of 600 to 1200 占 폚, and more preferably 700 to 1100 占 폚. When the firing temperature is less than 600 ° C, it is difficult to obtain barium titanate in a single phase. On the other hand, when the firing temperature exceeds 1200 ° C, the fluctuation of the particle diameter becomes large. The firing time is preferably 2 to 30 hours, more preferably 5 to 20 hours. The firing atmosphere is not particularly limited and may be any of the atmosphere in an inert gas atmosphere under a vacuum atmosphere, an oxidizing gas atmosphere, or firing in the atmosphere while introducing water vapor.

Firing can be done any number of times if desired. Alternatively, for the purpose of making the powder characteristics uniform, it is also possible to pulverize the calcined material once, and then re-calcine it.

After firing, it is suitably cooled and, if necessary, pulverized to obtain a powder of barium titanate. The pulverization which is carried out according to need is suitably carried out, for example, in the case where barium titanate obtained by firing is a weak and block phase, and the barium titanate particles themselves have the following specific average particle diameter and BET specific surface area. That is, the average particle size of the barium titanate powder obtained from the scanning electron microscope (SEM) is preferably 0.5 μm or less, and more preferably 0.05 to 0.5 μm. The BET specific surface area is preferably 2 to 20 m 2 / g, more preferably 2.0 to 10 m 2 / g. In addition, the composition of barium titanate obtained by the production method of the present invention is preferably such that the molar ratio (Ba / Ti) of Ba and Ti is 0.998 to 1.002, particularly approximately 1. [ It is more preferable that the c-axis / a-axis ratio which is an index of crystallinity is 1.007 or more, preferably 1.0085 or more.

The barium titanate obtained by carrying out the production method of barium titanate of the present invention may be added to barium titanate obtained by carrying out the production method of barium titanate of the present invention for the purpose of adjusting dielectric characteristics and temperature characteristics as necessary Can be added to contain a subcomponent element. Examples of the subcomponent-containing compound which can be used include rare earth elements such as Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, At least one element selected from the group consisting of Li, Bi, Zn, Mn, Al, Si, Ca, Sr, Co, Ni, Cr, Fe, Mg, Ti, V, Nb, Mo, And the like.

The subcomponent-containing compound may be either an inorganic substance or an organic substance. For example, oxides, hydroxides, chlorides, nitrates, oxalates, carboxylates and alkoxides containing the above elements can be mentioned. When the subcomponent-containing compound is a compound containing an Si element, silica sol, sodium silicate or the like may be used in addition to the oxide. The subcomponent-containing compound may be used alone or in combination of two or more. The addition amount thereof and the combination of the additive compound can be carried out according to a conventional method.

In order to contain the subcomponent in barium titanate, for example, barium titanate and the subcomponent-containing compound may be homogeneously mixed and fired. Alternatively, barium titanyl oxalate and the subcomponent-containing compound may be homogeneously mixed and fired.

For example, when a multilayer ceramic capacitor is produced using barium titanate obtained by carrying out the production method of barium titanate of the present invention, the barium titanate powder is first mixed with a conventionally known additive, an organic binder, a plasticizer , A dispersing agent and the like are mixed and dispersed in an appropriate solvent to form a slurry, and the sheet is formed. Thus, a ceramic sheet used for producing a multilayer ceramic capacitor is obtained. In order to produce a multilayer ceramic capacitor from the ceramic sheet, first, a conductive paste for forming an internal electrode is printed on one surface of the ceramic sheet. After drying, a plurality of the ceramic sheets are laminated and pressed in the thickness direction to obtain a laminate. Next, this laminate is heat-treated to perform a debindering treatment, and fired to obtain a sintered body. Further, Ni paste, Ag paste, nickel alloy paste, copper paste, copper alloy paste and the like are coated and baked on the sintered body to obtain a multilayer ceramic capacitor.

When the powder of barium titanate obtained by the method for producing barium titanate of the present invention is mixed with a resin such as an epoxy resin, a polyester resin or a polyimide resin to form a resin sheet, a resin film, an adhesive, or the like, A printed circuit board, a multilayer printed wiring board and the like, but also a material for suppressing a shrinkage difference between the internal electrode and the dielectric layer, an electrode ceramic circuit board, a glass ceramic circuit board, a circuit peripheral material, and a dielectric material Can also be used.

Further, the barium titanate obtained by carrying out the production method of barium titanate of the present invention is preferably used as a catalyst used in a reaction such as exhaust gas removal, chemical synthesis and the like, as a surface modifying material for a printing toner for imparting antistatic and cleaning effects .

<Examples>

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

[Examples 1 to 14]

(Preparation of solution A)

The barium chloride 2 hydrate and the oxalic acid dihydrate were added to pure water at 30 DEG C so that the ratios shown in Table 1 were obtained, and the mixture was stirred at a stirring speed of 1.3 m / sec for 0.5 hour to give Solution A as a solution.

(Preparation of liquid B)

A commercially available 15 wt% aqueous solution of titanium tetrachloride was diluted with pure water to obtain a solution of composition B shown in Table 1.

Solution B was added to Solution A under the conditions shown in Table 2, and aging was performed for 1 hour. After completion of the aging, the barium titanyl oxalate was recovered by filtration.

Then, the recovered barium titanyl oxalate was repulped with pure water and washed thoroughly. And then dried at 105 DEG C for 2 hours to obtain a powder of barium titanyl oxalate. Table 3 shows various physical properties of the barium titanyl oxalate obtained. The molar ratio of Ba to Ti was measured by fluorescent X-ray. The average particle diameter was measured by a laser diffraction / scattering method particle size distribution measuring apparatus. The results are shown in Table 3.

[Comparative Example 1]

(Preparation of solution A)

Oxalic acid dihydrate was added to pure water at 30 DEG C in the ratio shown in Table 1, and the mixture was stirred at a stirring speed of 1.3 m / sec for 0.5 hour to give Solution A as a solution.

(Preparation of liquid B)

The solution of the composition shown in Table 1, which was obtained by adding barium chloride dihydrate to purified water and a commercially available aqueous solution of titanium tetrachloride of 15 wt%, was designated as Solution B.

Solution B was added to Solution A under the conditions shown in Table 2, and aging was performed for 1 hour. After completion of the aging, the barium titanyl oxalate was recovered by filtration.

Then, the recovered barium titanyl oxalate was repulped with pure water and washed thoroughly. And then dried at 105 DEG C for 2 hours to obtain a powder of barium titanyl oxalate. Table 3 shows various physical properties of the barium titanyl oxalate obtained. The molar ratio of Ba to Ti was measured by fluorescent X-ray. The average particle diameter was measured by a laser diffraction / scattering method particle size distribution measuring apparatus. The results are shown in Table 3.

[Comparative Example 2]

(Preparation of solution A)

Oxalic acid 2-hydrate and commercially available 15 wt% aqueous solution of titanium tetrachloride in purified water were added at 30 ° C in the proportions shown in Table 1, and the mixture was stirred at a stirring speed of 1.3 m / sec for 0.5 hour.

(Preparation of liquid B)

A solution of the composition shown in Table 1 obtained by dissolving barium chloride dihydrate in pure water was designated as Solution B.

Solution B was added to Solution A under the conditions shown in Table 2, and aging was performed for 1 hour. After completion of the aging, the barium titanyl oxalate was recovered by filtration.

Then, the recovered barium titanyl oxalate was repulped with pure water and washed thoroughly. And then dried at 105 DEG C for 2 hours to obtain a powder of barium titanyl oxalate. Table 3 shows various physical properties of the barium titanyl oxalate obtained. The molar ratio of Ba to Ti was measured by fluorescent X-ray.

The average particle diameter was measured by a laser diffraction / scattering method particle size distribution measuring apparatus. The results are shown in Table 3.

[Comparative Example 3]

(Preparation of solution A)

Barium chloride heptahydrate was added to pure water at 30 DEG C in the ratio shown in Table 1, and the mixture was stirred at a stirring speed of 1.3 m / sec for 0.5 hour to obtain a solution A.

(Preparation of liquid B)

The solution of the composition shown in Table 1, which was obtained by adding oxalic acid dihydrate to purified water and a commercially available 15 wt% aqueous solution of titanium tetrachloride, was designated as Solution B.

Solution B was added to Solution A under the conditions shown in Table 2, and aging was performed for 1 hour. After completion of the aging, the barium titanyl oxalate was recovered by filtration.

Then, the recovered barium titanyl oxalate was repulped with pure water and washed thoroughly. And then dried at 105 DEG C for 2 hours to obtain a powder of barium titanyl oxalate. Table 3 shows various physical properties of the barium titanyl oxalate obtained. The molar ratio of Ba to Ti was measured by fluorescent X-ray. The average particle diameter was measured by a laser diffraction / scattering method particle size distribution measuring apparatus. The results are shown in Table 3.

Note) The oxalic acid concentration in the table indicates the concentration as oxalic acid dihydrate.

Note) Oxalic acid in the table indicates 2 hydrate.

Note) BTO represents barium titanyl oxalate.

From Table 3, the barium titanyl oxalate obtained in the examples has an average particle diameter of 4 占 퐉 or less as determined by laser diffraction scattering method and the composition of the barium titanyl oxalate has a Ba / Ti molar ratio of approximately 1.000 to 1.002, .

From Table 3, the barium titanyl oxalate obtained in Comparative Example had an average particle diameter of more than 4 mu m as determined by laser diffraction scattering method, and the Ba / Ti molar ratio of the barium titanyl oxalate was 0.997 to 1.001.

[Examples 15 and 16 and Comparative Examples 4 to 6]

&Lt; Preparation of barium titanate &

8 g of the barium titanyl oxalate sample obtained in Example 1 and Comparative Examples 1 to 3 was fired in air at 875 or 900 DEG C for 24 hours. After cooling, the mixture was pulverized to obtain powders of barium titanate. Table 4 shows various physical properties of the obtained barium titanate. The molar ratio of Ba to Ti was determined in the same manner as described above. The average particle size was determined from the SEM photograph, and the specific surface area was determined by the BET method. With respect to the obtained barium titanate, the ratio of the lengths of the c-axis and the a-axis, which is an index of crystallinity (c-axis / a-axis ratio), was measured by XRD.

Note) BTO represents barium titanyl oxalate. BT represents barium titanate.

It can be seen from Table 4 that barium titanyl oxalate (Example 15) obtained in the present invention was used at the same temperature (900 DEG C) as the firing temperature, and barium titanate having a high c-axis / a- . It was also found that the c-axis / a-axis ratio of barium titanate obtained even when the firing temperature was lowered to 875 캜 (Example 16) was as high as 1.0085 or more.

&Lt; Industrial Availability >

According to the present invention, barium titanyl oxalate having a Ba / Ti molar ratio of approximately 0.998 to 1.002 can be provided, even if the average particle size is as small as 4 占 퐉 or less. By using such barium titanyl oxalate, a dielectric ceramic material having high crystallinity and excellent performance can be provided by the oxalate method despite the small particle size.

Claims (7)

A method for producing barium titanyl oxalate, which comprises reacting a solution (solution A) containing at least oxalic acid and barium chloride with an aqueous solution (solution B) containing titanium tetrachloride. The method for producing barium titanyl oxalate according to claim 1, wherein the liquid A is obtained by contacting oxalic acid and barium chloride in a water solvent. The method for producing barium titanyl oxalate according to claim 1, wherein the ratio (B / A) of the chloride ion concentration in the liquid B to the chloride ion concentration in the liquid A is 0.50 to 5 by weight. 4. The process for producing barium titanyl oxalate according to any one of claims 1 to 3, wherein the reaction temperature is 40 占 폚 or lower. The method for producing barium titanyl oxalate according to any one of claims 1 to 4, wherein the resulting barium titanyl oxalate has an average particle diameter of 4 탆 or less. A process for producing barium titanate according to any one of claims 1 to 5, wherein the barium titanyl oxalate is calcined. The method for producing barium titanate according to claim 6, wherein the baking temperature is 600 to 1200 占 폚.