JP3163649B2 - Manufacturing method of ceramic raw material powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a ceramic raw material powder, and more particularly to a method for producing a ceramic raw material powder having a fine particle diameter, which is useful as a ceramic material for electronic parts.

[0002]

2. Description of the Related Art With the miniaturization of electronic devices, miniaturization of electronic components incorporated therein has been attempted. Among the electronic components, for example, there are two methods for reducing the size of a ceramic capacitor, a method using a dielectric porcelain having a higher dielectric constant and a method using a thinner dielectric layer. Because a dramatic increase cannot be expected,
Only dielectric thinning is being pursued. However, simply reducing the thickness of the ceramic capacitor not only increases the dielectric loss but also increases the capacitance change with respect to DC bias change and applied AC voltage change. In addition, when the grain size of the dielectric ceramic is large, there is a problem that relatively large holes exist between the crystal grains, which causes a reduction in withstand voltage.

Therefore, in order to reduce the thickness of the ceramic capacitor, it is necessary to solve the above problems,
This is achieved by making the grain size of the grain size fine and uniform. It is well known that in order to obtain such dielectric porcelain, the raw material powder itself needs to be fine and uniform.

Conventionally, ceramics for electronic parts, for example,
As a method for producing a raw material powder of a barium titanate-based dielectric porcelain, (a) a carbonate or oxide such as barium carbonate, calcium carbonate, strontium carbonate, titanium oxide, zirconium oxide, or tin oxide is used as a raw material;
These are appropriately blended and calcined, and once BaTiO ₃ , Ca
A method of generating ZrO _{3 and the} like, mixing them at a predetermined ratio, and firing the mixture; (b) mixing all the raw materials at a predetermined ratio so as to have the composition of the final product, and calcining the mixed powder. (C) precipitation of Ti ion and Ba ion with titanic acid as titanyl barium oxalate,
This precipitate is calcined at a temperature of 700 ° C. or more to synthesize barium titanate, and (d) a method in which titanium and barium are precipitated as alkoxides and the precipitate is calcined at a predetermined temperature. Are known.

[0005]

However, the solid-state reaction methods (a) and (b) have a common problem caused by using dried carbonates and oxides as raw materials. There is. That is, these raw materials are first precipitated as colloidal fine particles by a liquid phase reaction, but are filtered and then agglomerated into secondary particles in a stage of drying (and, in some cases, further calcination) to form crystal grains. Becomes larger. Even if the raw materials once aggregated are to be mixed, it is difficult to reduce the particle size to 1 μm or less by pulverization, and it is impossible to uniformly disperse and mix these raw materials at the molecular level. Therefore, the dielectric ceramic using the mixed powder has a crystal grain size of 5 μm or more, which causes not only the problem described above but also a variation in characteristics.

On the other hand, in the above-mentioned liquid phase reaction methods (c) and (d), fine particles of each raw material are mixed as they are in the form of colloid obtained by precipitation. Although it is possible, the oxalic acid method can produce molecular compounds for some constituent elements, for example, Ba and Ti, but cannot precipitate other constituent elements at the same time. There is a problem that it is not possible to obtain a composite ceramic used industrially. Also, oxalate has the disadvantage of being expensive and industrially disadvantageous. On the other hand, in the alkoxide method, most of metal alkoxides are expensive, and depending on the kind of metal, they are insoluble in organic solvents or cannot be synthesized, so that they are generally difficult to use. Moreover, since an organic solvent is used, there is a problem that it is disadvantageous in industrial use, such as a need to take measures to explode the solvent.

Accordingly, the present invention has been made to overcome the above-mentioned drawbacks of the prior art, and to enable easy and safe production of ceramic raw material powder having a fine particle size. The purpose is to be able to obtain.

[0008]

According to the present invention, as a means for solving the above-mentioned problems, in a first reaction tank, ceramics are selected from the group consisting of nitrates or chlorides of Ba, Sr, Ca and Mg. At least one surfactant is added to the obtained aqueous solution containing at least one, and a carbonate aqueous solution is added thereto to adjust the pH thereof to 7 to 10 to precipitate the ceramic constituent elements as carbonate. And Ti, Zr, Sn, as ceramic constituent elements
Alkali hydroxide is added to an aqueous solution containing at least one selected from the group consisting of nitrates or chlorides of Pb and Mn to adjust the pH thereof to 7 to 10 to precipitate the ceramic constituent elements as hydroxides. One kind of surfactant is added, and then the reaction solutions of both reaction tanks are mixed,
The precipitate is filtered from the mixed reaction solution, washed with water, dried,
The obtained powder is calcined.

Examples of the carbonate include, but are not limited to, carbon dioxide, alkali carbonate and ammonium carbonate. Further, as the alkali hydroxide, sodium hydroxide, ammonium hydroxide,
Typical examples include potassium hydroxide and lithium hydroxide, but are not limited thereto.

Further, the surfactant includes, for example, carboxylate, sulfonate, sulfate, phosphate, aliphatic amine salt and its ammonium salt, aromatic quaternary ammonium salt, heterocyclic 4 Ionic surfactants such as quaternary ammonium salts; polyoxyethylene alkyl ether, single-chain polyoxyethylene alkyl ether, polyoxyethylene secondary alcohol ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene glycerin fatty acid ester, poly Non-ionic fields such as oxyethylene sorbitan fatty acid ester, polyethylene glycol fatty acid ester, propylene glycol fatty acid ester, fatty acid alkanolamide, polyoxyethylene fatty acid amide, polyoxyethylene alkylamine Active agent; and carboxy betaine, sulfo betaine, aminocarboxylates, and ampholytic surfactants such as imidazoline derivatives. These can be used alone or in combination.

The aqueous solution of the second reaction layer contains N, which functions as a crystal growth inhibitor for suppressing crystal grain growth during sintering.
At least one of b, Y and rare earth elements may be contained. Further, Mn, Al, Si, Bi, Zn, Fe, Cr, as mineralizers are added to the aqueous solution of the second reaction layer.
At least one selected from the group consisting of Co and Cu may be contained.

Further, in order to prevent the pH from being shifted at the stage of mixing the first slurry and the second slurry, the pH of the aqueous solution of the first reaction layer and the pH of the aqueous solution of the second reaction layer are made equal. More preferred. In the second reaction layer, the pH of the aqueous solution is adjusted to 7 to 10, but the reason is limited to this range because the constituent elements are dissolved even if the pH is lower or higher.

Further, in order to prevent the Ti hydroxide from being hydrolyzed and precipitated, and to lower the decomposition temperature of the product and facilitate the subsequent filtration and washing, the aqueous solution of the second reaction layer is added with an alkali hydroxide. Before the addition, an appropriate amount of hydrogen peroxide may be added. If hydrogen peroxide is added to the aqueous solution of the second reaction layer, when the aqueous solution becomes alkaline, hydrogen peroxide is decomposed to generate nascent oxygen, for example, Ti, Zr,
Mn is represented by Ti (OOH) (OH) ₃ , Zr (OOH) (OH) ₃ ,
Each precipitates in the form of an oxyhydroxide having a low decomposition temperature, such as nOOH.

The ceramic raw material powder obtained by the method of the present invention is a perovskite-type oxide represented by the general formula: ABO ₃ , and the precipitate formed in the first reaction layer is formed of the A site of the general formula. It does not mean the carbonate of the element, and the precipitate formed in the second reaction layer does not mean the hydroxide of the element at the B site in the above general formula. In short, an element that can be precipitated as a carbonate may be precipitated in the first reaction layer, and an element that can be precipitated as a hydroxide may be precipitated in the second reaction layer, regardless of the A and B sites. . 700-1000 dry powder
It is preferred to calcine at a temperature in the range of ° C.

In the obtained ABO ₃ type ceramic raw material powder, the molar ratio between A site and B site (A /
B) is preferably in the range of 1.00 to 0.95. this is,
This is because the grain size increases as the molar amount of the B site increases, and a gap is formed between the grains.

[0016]

According to the method of the present invention, the ceramic constituent elements are precipitated as carbonates or hydroxides according to the respective elements, and these are mixed with colloidal fine particles. In addition, by containing at least one of Nb, Y and rare earth elements in the aqueous solution of the second reaction layer, these elements function as a crystal growth inhibitor, and the The grain size can be reduced to 1 μm or less to suppress grain growth. Also, these crystal growth inhibitors
The effect of flattening the temperature characteristic of the dielectric constant of the dielectric porcelain also works. For example, barium titanate has a peak value of the dielectric constant around 120 ° C., and has a function of flattening this peak value. Among the crystal growth inhibitors, Ce and Nd have a weak depressor effect and are rather effective in obtaining a high dielectric constant. La and Nb, especially Nb, are effective in flattening the temperature characteristics of the dielectric constant.

Hereinafter, embodiments will be described in detail.

[0018]

【Example】

(Example 1) Materials shown in Table 1 were prepared as raw materials to be used.

[0019]

[Table 1]  

First, in a first reaction tank, an anionic surfactant (Caribbon L-400 manufactured by Sanyo Chemical Co., Ltd.) was dissolved in a solution of barium chloride in an amount shown in Table 1 in 1,000 cc of pure water in terms of an effective component. After adding 5 g, ammonium carbonate was added to adjust the pH to 9 to 9.5, and a slurry containing a precipitate of barium carbonate was obtained.

Separately, titanium tetrachloride, tin tetrachloride, silicon tetrachloride, and manganese chloride in the amount shown in Table 1 were mixed and dissolved in 1000 cc of pure water in a second reaction tank.
5 ml, and ammonia water was added thereto to adjust the pH to 9 to 9.
The pH was adjusted to 9.5, and Ti, Sn, Si, and Mn were precipitated as oxyhydroxides.
5 g was added to obtain a slurry.

The slurry in the first reaction tank and the slurry in the second reaction tank were mixed, filtered, and washed with water. After mixing and pulverizing this water-washing raw material with a ball mill, the mixture is filtered and dried,
Calcination at 900 ° C for 1 hour, pulverized and Ba (Ti,
A calcined powder of Sn) O ₃ was obtained. The average particle size of the calcined powder is D
_{At 50} , it was 0.5 μm.

A binder was added to the calcined powder, granulated by a conventional method, formed into a disc shape, and fired at 1300 ° C. for 2 hours to obtain a porcelain disc. (The average grain size of the porcelain was 1.1 μm.) Silver electrodes were formed on both sides of the porcelain disk by a conventional method to obtain a capacitor.

Using this capacitor as a sample, its dielectric constant, dielectric loss (tan δ), and temperature coefficient of capacitance (TC
C) and withstand voltage characteristics were measured. Table 2 shows the obtained results.

[0025]

[Table 2] Dielectric constant tanδ (%) TCC (%) Withstand voltage (KV / mm) 18000 2.0 +20 to -70 15

(Example 2) Materials shown in Table 3 were prepared as raw materials to be used.

[0027]

[Table 3]

First, each compound of alkaline earth metal ions was mixed and dissolved in 1000 cc of pure water in a first reaction tank, and anionic and nonionic surfactants (Carbon L-400 manufactured by Sanyo Chemical Co., Ltd. and Newpole) were added. PZ-68) was added in an amount of 0.25 g in terms of the active ingredient, and sodium carbonate was added to adjust the pH to 9 to 9.5.
a, Sr, Mg) Co ₃ ).

Further, the aqueous solutions of the remaining metal chlorides or oxychlorides are mixed, 30 ml of hydrogen peroxide is added, and the pH is adjusted to 9 to 9.5 by adding caustic soda.
A precipitate containing Sn, Zr, Mn, Ce, and Zn was obtained, and anionic and nonionic surfactants (Caribbon L-400 and Newpol PZ-68, manufactured by Sanyo Chemical Co., Ltd.) were added in an amount of 0.25 g in terms of active ingredients. Add each.

Thereafter, in the same manner as in Example 1, the average particle diameter was D
₅₀ of 0.7μm (Ba, Sr, Mg) (Ti, Sn,
Zr) O ₃ -based calcined powder was obtained. Using this calcined powder,
A capacitor was obtained in the same manner as in Example 1. The firing temperature was 1150 ° C. Table 4 shows the results obtained by measuring the electric characteristics.

[0031]

[Table 4] Dielectric constant tan δ (%) TC (%) Withstand voltage (KV / mm) 6000 1.5 +15 to -48 18

Example 3 The raw materials shown in Table 5 were prepared.

[0033]

[Table 5]

First, in the first reaction tank, Valum chloride was dissolved in 500 cc of pure water, and 0.26 g of an amphoteric surfactant (Amphitol 20BS manufactured by Kao) in terms of an active ingredient was converted.
And further add ammonium carbonate to adjust the pH to 9 to 9.
Adjusted to 9.5 to precipitate the carbonate.

In the second reaction layer, the remaining metal chloride or oxychloride was mixed and dissolved in 500 cc of pure water, and 10 ml of hydrogen peroxide was added. Adjusted to ~ 9.5, Ti, Ce, Zr,
A precipitate containing Mn was obtained, and a zwitterionic surfactant (Amphitol 20BS manufactured by Kao) was added in an amount of 0.26 in terms of the active ingredient.
g was added. Here, Ce was added as having both functions of a crystal growth inhibitor and a depressor.

[0036] Hereinafter, calcined at to 1000 ° C. in the same manner as in Example 1, the average particle size is 0.4μm at D ₅₀ Ba (Ti, Z
(r, Mn) O ₃ -based calcined powder was obtained. A binder and a solvent were added to the calcined powder to prepare a slurry, and then a ceramic green sheet was prepared by a doctor blade method. Internal electrodes were printed on the green sheet, and these were stacked and integrated by pressure bonding. This integrated product was cut to obtain a multilayer capacitor chip, and these were removed in air for 1 hour.
It was fired at 300 ° C. for 2 hours to form a multilayer capacitor body. The grain size of this capacitor body is 0.9 μm
Met.

External electrodes were formed at both ends of each element to produce a multilayer capacitor. The dielectric constant was measured.
000-11,000.

[0038]

As described above, according to the present invention,
A ceramic raw material powder having a fine particle size can be obtained by a simple operation using an inexpensive raw material. Moreover, since the raw material is chloride or nitrate and is reacted in the form of an aqueous solution, there is no danger of explosion as in the case of using an organic solvent,
Can be implemented safely. In addition, since the raw material powder according to the method of the present invention has a small particle size, when a ceramic capacitor is manufactured using the raw material powder, pores formed between crystal particles are reduced, and the withstand voltage can be improved. In addition, by containing a growth inhibitor for crystal grains, the crystal grain size of the ceramic can be suppressed to about 1 μm or less, and can approach the size of a domain called 0.6 μm. Excellent effects such as a reduction in the capacitance can be suppressed, a change in capacitance caused by application of an AC or DC voltage can be reduced, and mechanical strength can be further improved.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-195576 (JP, A) JP-A-59-195575 (JP, A) JP-A-1-290508 (JP, A) JP-A-49-195575 69599 (JP, A) JP-A-63-2808 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C01G 23/00 C01G 25/00 C01G 45/00 C04B 35/626

Claims (5)

(57) [Claims] (1) In a first reaction tank, at least one surfactant is added to an aqueous solution containing at least one selected from the group consisting of nitrates or chlorides of Ba, Sr, Ca and Mg as ceramic constituent elements. In addition, a carbonate aqueous solution is added thereto to adjust the pH to 7 to 10 to precipitate the ceramic constituent elements as carbonates, while the second reaction layer contains Ti, Zr, Sn, Pb as ceramic constituent elements.
And alkali hydroxide added to an aqueous solution containing at least one selected from the group consisting of nitrates and chlorides of Mn and Mn to adjust the pH thereof to 7 to 10 to precipitate the ceramic constituent elements as hydroxides. (B) mixing the reaction solutions in both reaction tanks, filtering out the precipitate from the mixed reaction solution, washing with water and drying, and (c) temporarily disposing the obtained powder. And baking a ceramic raw material powder. 2. The ceramic raw material powder according to claim 1, wherein the aqueous solution of the second reaction layer contains ions of at least one element selected from the group consisting of Nb, Y and rare earth elements. Production method. 3. The method according to claim 1, wherein the aqueous solution of the second reaction layer is Mn, A
3. The method for producing a ceramic raw material powder according to claim 1, comprising ions of at least one element selected from the group consisting of 1, Si, Bi, Zn, Fe, Cr, Co, and Cu. 4. 4. The method according to claim 1, wherein the surfactant is an ionic surfactant,
The method for producing a ceramic raw material powder according to any one of claims 1 to 3, wherein the method is at least one of a nonionic surfactant and an amphoteric surfactant. 5. The method for producing a ceramic raw material powder according to claim 1, wherein an appropriate amount of hydrogen peroxide is added before adding the alkali hydroxide to the aqueous solution of the second reaction layer.