JP2003342077A - Process for manufacturing dielectric ceramic raw powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an industrially advantageous process for manufacturing a dielectric ceramic raw powder which enables easy management of composition, has an accessory element firmly attached to the surface of the raw powder particle, allows no presence of a segregating or heterogeneous phase, even when baked, and may provide a small, highly reliable laminated capacitor having a high electrostatic capacity. <P>SOLUTION: In the manufacturing process, a compound containing the accessory element is attached to the surface of the particle of the perovskite (ABO<SB>3</SB>) ceramic raw powder. The process comprises a step wherein a slurry, obtained by dispersing the perovskite (ABO<SB>3</SB>) ceramic raw powder and the accessory element-containing compound in an aqueous medium, is spray dried with a spray bag dryer to obtain the dielectric ceramic raw powder. <P>COPYRIGHT: (C)2004,JPO

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 dielectric ceramic raw material powder, and is particularly useful as a raw material for functional ceramics such as piezoelectric bodies, optoelectronic materials, dielectrics, semiconductors and sensors. The present invention relates to a method for producing a dielectric ceramic raw material powder.

[0002]

2. Description of the Related Art Dielectric ceramic materials for monolithic ceramic capacitors are usually made of BaTiO ₃ or the like as a main component, and are used in several types for the purpose of imparting reduction resistance, adjusting temperature characteristics, and improving various characteristics such as reliability. Is added as an accessory element.

As a method for producing a dielectric ceramic material containing such a sub-component element, for example, a compound containing the sub-component element has an average particle size of 0.2 to 1.0 μm in advance.
A method of mixing and pulverizing the mixture into a mixture and dispersing the mixture with the main component (Japanese Patent Laid-Open No. Hei 5
-124857), a compound containing a sub-component element is heated and melted with a plasma flame at a temperature of 2000 ° C. or more and 20000 ° C. or less to be ultrafine particles,
A method of mixing with one or more main components of O ₃ , CaTiO ₃ , SrTiO ₃ or BaZrO ₃ (JP-A-10-255549) has been proposed.

Further, in Japanese Patent Laid-Open No. 63-141204, a metal oxide powder is dispersed in a solution of a metal salt containing a metal element component different from the metal oxide powder component. A method of adhering the metal element component on the surface, Japanese Patent Laid-Open No. 2000-203942 discloses that a dielectric ceramic basic composition powder is dispersed in water, and a Si compound is added to the slurry to form the dielectric material. A ceramic base composition powder, and then a slurry containing the dielectric ceramic base composition powder to which the Si compound is attached,
While stirring the slurry, a solution containing a metal element forming the compound and a precipitating agent that reacts with the metal element to form a precipitate are added to the dielectric ceramic basic composition with the desired metal element as a sub-component element. In the method disclosed in JP-A-10-139553, a ceramic basic composition powder is mixed and pulverized with an organic solvent and a surfactant to form a slurry, and then the composite alkoxide containing a metal element is added to the slurry. A method has been proposed in which a solution is added and mixed, then the organic solvent is removed from this slurry, and the surface is coated with a complex alkoxide containing the metal element.

[0005]

However, when a dielectric ceramic material is obtained by mixing the above-mentioned main component and a compound containing a sub-component element, the compound containing a sub-component element is uniformly dispersed in the main component. It is difficult to adhere them, and if such a state is fired, a biased layer or a different phase tends to occur. Further, even in the method of depositing a compound containing a sub-component element on the surface, it is not industrially advantageous because it is difficult to control the manufacturing process so that the compound containing the sub-component element always has a constant composition. In particular, the smaller the amount of the compound containing the accessory component element added, the more difficult the uniform mixing technically becomes. On the other hand, on the other hand, even if the auxiliary component is successfully and uniformly attached and dispersed on the surface of the main component particle, if the adhesion between the compound containing the auxiliary component element and the main component is weak, for example, a multilayer capacitor The compound containing the sub-component element is easily peeled off from the surface of the main component particles by applying a slight external force at the time of preparation, and as a result, the composition is changed, which easily causes defective products.

Therefore, an object of the present invention is to easily control the composition in a method for producing a dielectric ceramic raw material powder to which a compound containing a sub-component element is attached, and to attach the sub-component element firmly to the particle surface, It is an object of the present invention to provide an industrially advantageous method for producing a dielectric ceramic raw material powder that does not have a segregation phase or a heterogeneous phase even if fired, and can make a small-sized, high capacitance, highly reliable multilayer capacitor. .

[0007]

Under such circumstances, as a result of intensive researches conducted by the present inventors, the perovskite (A
After dispersing the BO ₃ ) -based ceramic raw material powder in an aqueous medium, a compound containing a sub-component element is added, and at least a part of the sub-component element is hardly soluble on the particle surface of the perovskite (ABO ₃ ) -based ceramic raw material powder. By subjecting the slurry deposited or deposited as a salt, hydroxide, or oxide to a dry treatment by a specific method, composition control of the subcomponents is easy, and the perovskite particle surface contains the subcomponent element. They have found that the compound particles can be adhered uniformly and firmly, and have completed the present invention.

That is, the present invention relates to a perovskite (ABO).
₃ ) The first step of dispersing the ceramic raw material powder in an aqueous medium to form a slurry, and one or more compounds selected from the group of compounds containing sub-component elements are added to the slurry after the first step. A second step, a third step of spray-drying the slurry after the second step to obtain a dielectric ceramic raw material powder, wherein a compound containing a sub-component element is attached to the surface of the ceramic raw material powder A method for obtaining a body ceramic raw material powder, wherein the spray drying in the third step is carried out by spraying the slurry after the second step into a bag-shaped or cylindrical drying chamber made of a heat-resistant porous material, and then in the drying chamber. It is intended to provide a method for producing a dielectric ceramic raw material powder, which is a method of separating dried exhaust gas and dielectric ceramic raw material powder by hot air supplied.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for producing a dielectric ceramic raw material powder according to an embodiment of the present invention will be described in detail by dividing it into first to third steps.

(First Step) The first step of the present invention is a step in which a perovskite (ABO ₃ ) ceramic raw material powder is dispersed in an aqueous medium to form a slurry. The perovskite-type ceramic raw material powder used as the raw material in the first step is not particularly limited, and may be BaTiO ₃ , SrTiO ₃ , Pb.
Examples thereof include TiO ₃ and CaZrO ₃ . These ceramic raw material powders can be used alone or in combination of two or more, and among them, BaTiO ₃ is particularly preferable.

The production history of such a perovskite-type ceramic raw material powder is not particularly limited, and those obtained by ordinary methods such as a wet method, a sol-gel method and a solid phase method are used. The physical properties of these perovskite-type ceramic raw material powders are not particularly limited, and those having an average particle size of 0.05 to 5 μm and 0.1 to 3 μm,
It is particularly preferable in terms of thinning the dielectric layer at the time of manufacturing the multilayer capacitor. This average particle size is determined by observation with an electron microscope. Further, those having a low content of impurities are particularly preferable for obtaining a highly pure product.

In the first step, first, the perovskite type ceramic raw material powder is added in an amount of 20 to 100 parts by weight of water.
A slurry having 100 parts by weight, preferably 40 to 85 parts by weight, is prepared. Usually, this slurry has a pH of 1 due to the elution of the A site in the perovskite-type ceramic raw material powder.
It becomes a weak alkaline substance of about 0.

In the first step, in order to uniformly disperse, a slurry in which the perovskite-type ceramic raw material powder is uniformly dispersed is prepared, if necessary, by using a dispersing device such as high-speed stirring, colloid mill and homogenizer. Is preferred. Further, at this time, in order to uniformly disperse the fine perovskite-type ceramic raw material powder in the slurry, a dispersion treatment such as a carboxylic acid, a polycarboxylic acid, or an ammonium salt thereof may be carried out as necessary. .

(Second Step) In the second step, the perovskite (ABO ₃ ) ceramic raw material powder prepared in the first step is dispersed in an aqueous medium, and the slurry contains one or more sub-component elements. Is a step of adding a compound to be added. Examples of the compound containing an accessory element include Sc, Y, La,
Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, D
rare earth elements of y, Ho, Er, Tm, Yb and Lu, B
a, Li, Bi, Zn, Mn, Al, Si, Ca, S
Examples thereof include compounds containing at least one metal element selected from the group consisting of r, Co, V, Nb, Ni, Cr, Fe and Mg. These compounds may be either inorganic substances or organic substances, or may be acidic compounds or alkaline compounds. Specific compounds include, for example, compounds containing one or more kinds of metal elements such as hydroxides, chlorides, nitrates, oxalates, carboxylates, and metal alkoxides, which show acidity. Examples of the compound include chlorides, nitrates, oxalates, and carboxylates containing the one or more metal elements, and examples of compounds showing alkalinity include the one or more metals. Examples thereof include hydroxides containing elements and metal alkoxides.
Further, in the case of a compound containing an Si element, silica sol, sodium silicate or the like can be used in addition to the above.
These compounds may be used alone or in combination of two or more. The compound containing these subcomponents can be added to the slurry as an aqueous solution dissolved in water or as it is.

The combination and addition amount of the compounds containing these sub-component elements can be arbitrarily set according to the intended dielectric properties, and the addition amount of each sub-component element is often a perovskite. It is 0.1 to 5 parts by weight as an element with respect to 100 parts by weight of the type ceramic raw material powder.

In the present invention, the method of adding one or more compounds containing a sub-component element is not particularly limited, but the following method (1) is a method of adding a compound showing alkalinity to the slurry after the first step. , (2) a method of adding a compound exhibiting acidity to the slurry after the first step,
(3) A method of appropriately selecting a compound showing alkalinity and a compound showing acidity and adding it to the slurry after the first step will be described separately.

The addition method (1) is a method of adding one or more kinds of only alkaline compounds to a slurry prepared by dispersing perovskite (ABO ₃ ) type ceramic raw material powder in water. By using the addition method of (1), most of the compound containing the accessory component element is converted to hydroxide on the surface of the perovskite (ABO ₃ ) ceramic particle by the (−) surface potential of the perovskite ceramic raw material. Can be attached.

The addition method (2) is a method of adding at least one kind of compound showing acidity to a slurry showing weak alkalinity in which perovskite (ABO ₃ ) ceramic raw material powder is dispersed in water. By using this addition method (2), the auxiliary component element is formed on the particle surface of the perovskite (ABO ₃ ) based ceramic raw material powder by the neutralization reaction between the alkali component in the slurry and the acidic compound to be added. It can be deposited as a fine sparingly soluble salt, hydroxide or oxide.

In the addition method (3), at least one compound containing an alkaline subcomponent element and an acidic subcomponent are added to a slurry prepared by dispersing perovskite (ABO ₃ ) ceramic raw material powder in water. In this method, one or more compounds containing an element are appropriately selected and added. By using the addition method of (3), the auxiliary component element is the perovskite (ABO ₃ ) based ceramic raw material powder due to the neutralization reaction between the alkaline component in the slurry and the alkaline compound to be added, and the acidic compound. It is possible to deposit fine refractory salts, hydroxides or oxides on the surface of the particles. In the addition methods (1) to (3), when a plurality of compounds are added, these compounds may be sequentially added to the slurry.

By carrying out the above-mentioned addition methods (1) to (3), one or more compounds having the above-mentioned sub-component element are added to the slurry after the completion of the first step, and the perovskite (ABO ₃ ) A step of precipitating or adhering at least a part of the accessory component element as a sparingly soluble salt, a hydroxide or an oxide on the particle surface of the system ceramic raw material powder. In this case, it is possible to obtain the perovskite-type ceramic raw material powder by depositing or adhering fine refractory salts, hydroxides or oxides of the sub-component elements on the particle surface, but after the second step is completed. In the slurry liquid of (1), unreacted or re-eluted subcomponent elements still exist.

Further, by performing the addition method of (2) or (3), the reaction between the perovskite ceramic raw material powder contained in the slurry after the completion of the first step and the compound containing the sub-component element The second step of depositing or adhering at least a part of the sub-component element as a sparingly soluble salt, hydroxide or oxide on the particle surface of the perovskite (ABO ₃ ) ceramic raw material powder can be performed.

(Third Step) In the third step, the entire amount of the slurry after the second step is spray-dried, and the sub-component elements dissolved in the slurry are further applied to the particle surface of the perovskite-type ceramic raw material powder. Along with the deposition, the insoluble salt, hydroxide or oxide of the sub-component element deposited or attached in the second step is further firmly attached to the particle surface of the perovskite type ceramic raw material powder to obtain the desired dielectric ceramic raw material powder. Is a step of obtaining.

In the spray drying in the third step, the slurry after the second step is sprayed into a bag-shaped or cylindrical drying chamber made of a heat-resistant porous material, and the hot exhaust gas is supplied to the drying exhaust gas and the dielectric. It is carried out by a method of separating the body ceramic raw material powder. The spray dryer used for the spray drying is also called a so-called spray back dryer and is distinguished from a normal spray dryer. That is, in the spray drying method typified by a normal spray dryer, the product fine powder after drying is collected separately from the main body of the device and the cyclone, and the relatively lightweight and small particle size is the cyclone, and the comparatively heavy particle is used. Since the one with a large diameter is taken out from the apparatus main body, the composition is likely to change due to the difference in the specific gravity or the difference in the particle size of the collected material. On the other hand, in the spray back dryer, as described above, the spray drying chamber is formed of a bag-shaped or cylindrical heat-resistant and good-peeling porous film, and hot air and a stock solution (slurry) are supplied to the spray drying chamber. Having a dry exhaust gas and fine powder separated by hot air supplied into the drying chamber, the fine powder collects the whole amount from the bottom of the spray drying chamber, and the dry exhaust gas passes through the pores of the porous membrane to form a bag or a cylinder. It is a special device that discharges to the outside. The stock solution is supplied to the spray drying chamber by spraying through an atomizer installed above the spray drying chamber. As the heat-resistant porous film forming the spray drying chamber, the mesh film is a PTFE film, the polytrifluoroethylene film, and the woven or non-woven fabric is polyimide, heat-resistant nylon, polyester,
An example is made of aramid. In the present invention, by spray-drying using this spray back dryer, the sub-element component dissolved in the slurry liquid can be attached to the particle surface of the perovskite-type ceramic raw material powder with a uniform and strong bond. As the drying conditions of this spray back dryer, the hot air inlet temperature is 200 to 230 ° C., the hot air outlet temperature is 90 to 130 ° C., preferably 100 to 120 ° C., the atomizer rotation speed is 3
000-8000 rpm, preferably 4000-600
It is preferable to carry out at 0 rpm. The spray back dryer is described in detail in JP-A-62-152501, and a commercially available one can be usually used.

The dielectric ceramic raw material powder thus obtained is, if desired, calcined and pulverized to obtain a product. The calcination condition is that the calcination temperature is 700 to 1100 ° C., preferably 85.
0 to 1050 ° C, calcination time 5 to 15 hours, 8 to 12
It is preferable to set the time. Further, in the present invention, this calcination may be performed as many times as desired. In the dielectric ceramic raw material powder obtained by this calcination, since the compound containing the sub-component element is present on the particle surface of the perovskite type ceramic raw material powder by a stronger bond or adhesion, for example, a bead mill, a ball mill Even if the wet pulverization is carried out for 30 hours or more in the apparatus, the compound particles containing the sub-component element are not peeled off and the composition of the dielectric ceramic raw material powder hardly changes.

The dielectric ceramic raw material powder obtained by the production method of the present invention is mixed and dispersed with a conventionally known compounding agent such as an additive, an organic binder, a plasticizer and a dispersant for producing a laminated ceramic capacitor. To make a slurry,
Sheet molding is performed to obtain a ceramic sheet, and then a conductive paste for forming internal electrodes is printed on one surface of the ceramic sheet, and after drying, a plurality of ceramic sheets are laminated and then pressure-bonded in the thickness direction. As a laminate,
This laminated body is heat-treated to remove the binder, and then fired to obtain a fired body, and then the sintered body is subjected to In—Ga paste, Ni paste, Ag paste, nickel alloy paste, copper paste, copper alloy paste, etc. It is possible to obtain a multilayer capacitor by applying and baking.

Further, for example, the dielectric ceramic raw material powder of the present invention is mixed with a resin such as an epoxy resin, a polyester resin or a polyimide resin, and a resin sheet, a resin film,
Materials such as printed wiring boards and multilayer printed wiring boards used as adhesives, co-materials for suppressing the contraction difference between internal electrodes and dielectric layers, electrode ceramics circuit boards, glass ceramics circuit board base materials and circuit periphery It can be added as a material, a catalyst used in reactions such as exhaust gas removal and chemical synthesis, and a surface modifier of a printing toner, and can also be used as a material for imparting an antistatic or cleaning effect.

[0027]

EXAMPLES Next, the present invention will be described in more detail by way of examples, which are merely examples and do not limit the present invention.

<Production of Barium Titanate> Barium titanate was used as the perovskite ceramic raw material powder. The barium titanate used was obtained by thermally decomposing barium titanyl oxalate (BaTiO (C ₂ O ₄ ) ₂ .4H ₂ O). The average particle size of the barium titanate determined by an electron micrograph was 0.6 μm.

Example 1 <First Step> BaT as a main component prepared above in 7 kg of water
5 kg of iO ₃ powder was added and sufficiently stirred to prepare a slurry in which BaTiO ₃ was uniformly dispersed.

<Second Step> 2.14 kg of an aqueous solution containing 6.62% by weight of Mg (OC ₂ H ₅ ) ₂ was dropped at a rate of 40 ml / min while stirring this slurry. The theoretical amount of Mg in the slurry containing the supernatant liquid (a) obtained by analyzing the Mg concentration of the supernatant liquid of the slurry obtained 30 minutes after the end of dropping by ICP and calculating from the charged amount of the raw materials.
Ratio of Mg amount (b) in the supernatant to (b / a)
Was calculated to be 2.65%.

<Third Step> After stirring the slurry (pH 12.7) obtained in the second step for 2 hours, a spray back dryer (BDP-22 manufactured by Okawara Kakoki Co., Ltd.) is used.
(Type) to obtain a dry powder. The operating conditions of the spray back dryer are: hot air inlet temperature 220 ° C,
Hot air outlet temperature 110 ° C, atomizer speed 5000r
It was done in pm.

Then, the obtained dry powder was calcined at 1030 ° C. for 10 hours to obtain a dielectric ceramic raw material powder. When the obtained dielectric ceramic raw material powder was observed by a scanning electron microscope, 0.005 to 0.005 was obtained on the surface of BaTiO _3.
The presence of fine particles of about 0.03 μm was confirmed. Also,
The composition of the fine particles present on the surface of BaTiO ₃ was analyzed by a transmission electron microscope, and it was found to be fine particles containing Mg. In addition, various physical property values of the obtained powder are shown in Table 1.

5% by weight of PVA binder was added to the obtained dielectric ceramic raw material powder, and the mixture was passed through a 250 mesh screen to press-mold a disk having a diameter of 15 mm and a thickness of 1 mm. Dispersion state of Mg in this compact S
Mapping analysis by EM-EPMA (manufactured by JEOL Ltd.) revealed that Mg was not unevenly distributed and was uniformly dispersed on the powder surface.

Comparative Example 1 A dielectric ceramic raw material powder sample was obtained in the same manner as in Example 1 except that a spray dryer was used as the drying device in the third step. The main physical property values are shown in Table 1. The operating conditions of the spray dryer are hot air inlet temperature 2
20 ° C, hot air outlet temperature 110 ° C, atomizer speed 5
It was set to 000 rpm.

[0035]

[Table 1]

Example 2 <First Step> The main component BaT prepared above was added to 7 kg of water.
5 kg of iO ₃ powder was added and sufficiently stirred to prepare a slurry in which BaTiO ₃ was uniformly dispersed.

<Second Step> 3.17 kg of an aqueous solution containing 5.76% by weight of Mn (CH ₃ COO) ₃ .4H ₂ O was added dropwise at a rate of 40 ml / min while stirring this slurry. The Mn concentration of the supernatant liquid of the slurry obtained 30 minutes after the end of dropping was analyzed by ICP, and the Mn concentration in the slurry containing the supernatant liquid calculated from the charged amount of the raw materials was compared with the theoretical amount (a) of Mn in the supernatant liquid. Ratio of Mn amount (b) (b
The value of / a) was 7.15%.

<Third step> After stirring the slurry (pH 7.58) obtained in the second step for 2 hours, a spray back dryer (BDP-22 manufactured by Okawara Kakoki Co., Ltd.)
(Type) to obtain a dry powder. The operating conditions of the spray back dryer are: hot air inlet temperature 220 ° C,
Hot air outlet temperature 110 ° C, atomizer speed 5000r
It was done in pm.

Next, the obtained dry powder was calcined at 1030 ° C. for 10 hours to obtain a dielectric ceramic raw material powder. When the obtained dielectric ceramic raw material powder was observed by a scanning electron microscope, 0.005 to 0.005 was obtained on the surface of BaTiO _3.
The presence of fine particles of about 0.03 μm was confirmed. Also,
The composition of the fine particles present on the surface of BaTiO ₃ was analyzed by a transmission electron microscope, and it was found to be fine particles containing Mn. In addition, various physical properties of the obtained powder are shown in Table 2.

5% by weight of PVA binder was added to the obtained dielectric ceramic raw material powder, and the mixture was passed through a 250 mesh screen to press-mold a disc disk having a diameter of 15 mmφ and a wall thickness of 1 mm. Dispersion state of Mn of this compact S
Mapping analysis by EM-EPMA (manufactured by JEOL Ltd.) revealed that Mn was not unevenly distributed and was uniformly dispersed on the powder surface.

Comparative Example 2 A dielectric ceramic raw material powder sample was obtained in the same manner as in Example 2 except that a spray dryer was used as the drying device in the third step. The main physical property values are shown in Table 2. In addition,
The operating condition of the spray dryer is hot air inlet temperature 220
℃, hot air outlet temperature 110 ℃, atomizer speed 500
It was performed at 0 rpm.

[0042]

[Table 2]

Example 3 <First step> BaT as the main component prepared above in 7 kg of water
5 kg of iO ₃ powder was added and sufficiently stirred to prepare a slurry in which BaTiO ₃ was dispersed.

<Second Step> 2.08 k of an aqueous solution containing 3.61% by weight of silica sol while stirring this slurry.
g was added dropwise at a rate of 40 ml / min. Drip end 30
The Si concentration of the supernatant of the slurry obtained after
When the ratio (b / a) of the amount (b) of Si in the supernatant liquid to the theoretical amount (a) of Si in the slurry containing the supernatant liquid obtained by calculation from It was 0.04%.

<Third Step> The slurry (pH 10.7)
3) was stirred for 2 hours, and then spray-dried with a spray back dryer (BDP-22 type manufactured by Okawara Kakohki Co., Ltd.) to obtain a dry powder. The operating conditions of the spray back dryer were hot air inlet temperature 220 ° C., hot air outlet temperature 110 ° C., and atomizer rotation speed 5000 rpm.

Then, the obtained dry powder was calcined at 1030 ° C. for 10 hours to obtain a dielectric ceramic raw material powder. When the obtained dielectric ceramic raw material powder was observed by a scanning electron microscope, 0.005 to 0.005 was obtained on the surface of BaTiO _3.
The presence of fine particles of about 0.03 μm was confirmed. Also,
The composition of the fine particles present on the surface of BaTiO ₃ was analyzed by a transmission electron microscope, and it was found to be fine particles containing Si. In addition, various physical properties of the obtained powder are shown in Table 3.

To the powder obtained above, 5% by weight of PVA binder was added and passed through a 250 mesh screen to obtain a diameter of 15 mm.
A circular disk having a φ and a wall thickness of 1 mm was pressure-molded. Mapping analysis of the Si dispersion state of this molded body by SEM-EPMA (manufactured by JEOL Ltd.) revealed that no Si bias was observed and that the powder was uniformly and highly dispersed on the powder surface.

Comparative Example 3 A dielectric ceramic raw material powder sample was obtained in the same manner as in Example 3 except that a spray dryer was used as the drying device in the third step. The main physical property values are shown in Table 3. In addition,
The operating conditions of the spray dryer are as follows.
The hot air inlet temperature was 220 ° C., the hot air outlet temperature was 110 ° C., and the atomizer rotation speed was 5000 rpm.

[0049]

[Table 3]

Example 4 <First Step> BaT as the main component prepared above in 9 kg of water
5 kg of iO ₃ powder was added and sufficiently stirred to prepare a slurry in which BaTiO ₃ was uniformly dispersed.

<Second Step> While stirring this slurry, 128.72 g of Sr (OH) ₂ .8H ₂ O powder was added. The Sr concentration of the supernatant liquid of the slurry obtained after 30 minutes was analyzed by ICP, and the theoretical amount (a) of Sr in the slurry containing the supernatant liquid calculated from the charged amount of the raw materials was compared with the Sr content of the supernatant liquid. The ratio (b / a) of the amount (b) was calculated and found to be 93.12%.

<Third Step> The slurry (pH 13.9)
After stirring 1) for 2 hours, it was spray-dried with a spray back dryer (BDP-22 type manufactured by Okawara Kakoki Co., Ltd.) to obtain a dry powder. The operating conditions of the spray back dryer were hot air inlet temperature 220 ° C., hot air outlet temperature 110 ° C., and atomizer rotation speed 5000 rpm.

Then, the obtained dry powder was dried at 1030 ° C. for 1 hour.
It was calcined for 0 hour to obtain a dielectric ceramic raw material powder. The obtained dielectric ceramic raw material powder was observed with a scanning electron microscope BaTiO ₃ on the surface, from 0.005 to 0.
The presence of fine particles of about 0.3 μm was confirmed. Also, Ba
The composition of the fine particles present on the surface of TiO ₃ was analyzed by a transmission electron microscope, and it was found to be fine particles containing Sr. In addition, various physical properties of the obtained powder are shown in Table 4.

To the above powder obtained, 5% by weight of PVA binder was added, passed through a 250 mesh sieve, and the diameter was 15 mm.
A circular disk having a φ and a wall thickness of 1 mm was pressure-molded. Mapping analysis of the dispersion state of Sr of this molded body by SEM-EPMA (manufactured by JEOL Ltd.) showed that Sr was not unevenly distributed and was highly dispersed uniformly on the powder surface.

Comparative Example 4 A dielectric ceramic raw material powder sample was obtained by the same operation method as in Example 4 except that a spray dryer was used as the drying device in the third step. The main physical property values are shown in Table 4. In addition,
The operating conditions of the spray dryer are as follows.
The hot air inlet temperature was 220 ° C., the hot air outlet temperature was 110 ° C., and the atomizer rotation speed was 5000 rpm.

[0056]

[Table 4]

Example 5 <First Step> The main component of BaT prepared above was added to 7 kg of water.
5 kg of iO ₃ powder was added and sufficiently stirred to prepare a slurry in which BaTiO ₃ was uniformly dispersed.

<Second step> Slurry obtained in the first step
57.43 g Ba (OH) while stirring₂・ 8H₂O
Was thrown in. Thirty minutes after the completion of dropping, the obtained slurry was stirred.
35.01 g Sr (OH) while stirring₂・ 8H₂Throw O
I entered. 30 minutes after the end of dropping, the resulting slurry was stirred.
While Mn (CH₃COO)₂・ 4H₂6.50 weight of O
% Aqueous solution containing 748.63 g of 40 ml / min
Dropped at a rate. 30 minutes after the end of dropping, the obtained slurry
While stirring Ho (CH₃COO)₃・ 4H₂O to 7.
40 ml of 1075.33 g of an aqueous solution containing 01% by weight
It was dripped at a rate of / min. 30 minutes after the end of dropping, obtained
Dy (CH₃COO)₃・ 4H
₂740.54 g of an aqueous solution containing 5.47% by weight of O
It was added dropwise at a rate of 40 ml / min. 30 minutes after dropping
After that, the silica sol was stirred while stirring the obtained slurry.
40 min / 460.5 g of an aqueous solution containing 34% by weight
It was dripped at a rate of min. Obtained 30 minutes after the end of dropping
While stirring the slurry, Mg (OC₂H_Five) ₂To 4.03
40 ml / mi of 729.42 g of an aqueous solution containing 50% by weight
It was added dropwise at a rate of n. Slurry obtained 30 minutes after the end of dropping
Ba, Sr, Mn, Ho, Dy, S of the supernatant of Lee
Measure the i and Mg concentrations by ICP and measure from the amount of raw material charged.
In the slurry containing the supernatant of these elements calculated
Ratio of the amount of element (b) in the supernatant to the theoretical amount (a)
The rate (b / a) was calculated. The results are shown in Table 5.

[0059]

[Table 5]

<Third Step> The slurry (pH 10.4)
After 8) was stirred for 2 hours, it was spray dried with a spray back dryer (BDP-22 type, manufactured by Okawara Kakoki Co., Ltd.) to obtain a dry powder. The operating conditions of the spray back dryer were hot air inlet temperature 220 ° C., hot air outlet temperature 110 ° C., and atomizer rotation speed 5000 rpm.

Then, the obtained dry powder was calcined at 1030 ° C. for 10 hours to obtain a dielectric ceramic raw material powder. When the obtained dielectric ceramic raw material powder was observed by a scanning electron microscope, 0.005 to 0.005 was obtained on the surface of BaTiO _3.
The presence of fine particles of about 0.03 μm was confirmed. Also,
The composition of the fine particles present on the surface of BaTiO ₃ was analyzed by a transmission electron microscope, and Ba, Sr, Mn, Ho,
It was found to be Dy, Si, and Mg. Further, various physical properties of the obtained dielectric ceramic raw material powder are shown in Table 6,
The electron micrograph is shown in FIG.

[0062]

[Table 6]

To the above powder obtained, 5% by weight of PVA binder was added, passed through a 250 mesh sieve, and the diameter was 15 mm.
A circular disk having a φ and a wall thickness of 1 mm was pressure-molded. Mapping analysis of the dispersed state of Ba, Sr, Mn, Ho, Dy, Si, Mg of this molded body by SEM-EPMA (manufactured by JEOL Ltd.) revealed that Ba, Sr, Mn, H
No segregation of o, Dy, Si, and Mg was observed, and the powder was uniformly and highly dispersed on the powder surface.

Further, this molded body was subjected to 12 atmosphere in N ₂ atmosphere.
Abnormal grain growth was not observed in the one fired at 45 ° C. for 2 hours. On the other hand, barium titanate prepared in the section of <Barium titanate sample> described above was similarly molded and
Abnormal grain growth was observed after firing at ℃ for 2 hours.
Further, an electrode was applied to the obtained molded body with an In—Ga paste, the dielectric constant was measured, and the rate of change in capacitance with temperature was determined.
The result is shown in FIG. From the result of FIG. 2, it was confirmed that the X7R characteristic of the EIA standard was satisfied. The inside of the dotted frame in FIG. 2 shows the range of the X7R characteristic.

Comparative Example 5 A dielectric having Ba, Sr, Mn, Ho, Dy, Si, and Mg attached to the surface of BaTiO ₃ particles was prepared by the same operation as in Example 5, except that the drying apparatus was spray-dried with a spray dryer. A body ceramic raw material powder was obtained. In addition, various physical properties of the obtained powder are shown in Table 7. The operating conditions of the spray dryer were hot air inlet temperature 220 ° C., hot air outlet temperature 110 ° C., and atomizer rotation speed 5000 rpm.

[0066]

[Table 7]

Further, 1 kg of the dielectric ceramic raw material powder obtained in Example 5 and Comparative Example 5 was put into a ball mill, wet-milled at 100 rpm for 33.5 hours, filtered, dried, and dried. The composition is shown in Table 8. In addition,
The amount of elements other than Ba is the analytical value obtained by ICP, and
The element amount of a is an analytical value obtained by XRF.

[0068]

[Table 8]

From the results shown in Table 8, the composition of Comparative Example 5 has a composition change due to the sub-component elements easily peeling off during wet pulverization, whereas the composition of Comparative Example 5 is obtained by the production method of the present invention. Even if the dielectric ceramic raw material powder is pulverized by the wet pulverizer, the composition hardly changes,
It can be seen that the powder adheres to the perovskite type ceramic raw material powder with a stronger bond than ever before.

[0070]

As described above, according to the method for producing the dielectric ceramic raw material powder of the present invention, the content of the sub-component element is the content of the sub-component element calculated from the charged amount and the sub-component element actually obtained. Since the contents of the constituent elements are almost the same, it is easy to manage the composition of the elements that are the sub-components.
Since the obtained dielectric ceramic raw material powder is one in which the elemental components that are the subcomponents are uniformly dispersed on the surface of the powder particles, there is no segregation phase or heterophase even if this is fired, and the particles Since the sub-component element is firmly attached to the surface, there is almost no change in composition during the production of the laminated ceramic. Therefore, by using this as a dielectric ceramic raw material, for example, it is possible to obtain a small-sized, high capacitance, highly reliable multilayer capacitor.

[Brief description of drawings]

FIG. 1 is an electron micrograph of a dielectric ceramic raw material powder obtained in Example 5.

FIG. 2 is a graph showing a temperature change rate of capacitance of the multilayer capacitor obtained in Example 5.

Continued front page    F-term (reference) 4G030 AA02 AA07 AA08 AA09 AA10                       AA11 AA16 AA19 AA20 AA22                       AA25 AA27 AA28 AA32 AA36                       AA37 AA43 BA09 GA01 GA07                       GA08                 4G031 AA01 AA03 AA04 AA05 AA06                       AA07 AA11 AA13 AA14 AA16                       AA19 AA21 AA22 AA23 AA26                       AA29 AA30 AA35 BA09 GA01                 5G303 AA01 AA10 AB20 BA12 CA01                       CB01 CB03 CB05 CB06 CB09                       CB10 CB13 CB16 CB17 CB18                       CB21 CB23 CB30 CB32 CB35                       CB36 CB38

Claims (6)

[Claims] 1. A first step of dispersing a perovskite (ABO ₃ ) based ceramic raw material powder in an aqueous medium to form a slurry, and one kind selected from the group of compounds containing a sub-component element in the slurry after the completion of the first step, or A second step of adding two or more compounds, a third step of spray-drying the slurry after the second step to obtain a dielectric ceramic raw material powder, and a sub-component element on the particle surface of the ceramic raw material powder. A method for obtaining a dielectric ceramic raw material powder having a compound containing, wherein the spray drying in the third step,
A method in which the slurry after the second step is sprayed into a bag-shaped or cylindrical drying chamber made of heat-resistant porous material and separated into dry exhaust gas and dielectric ceramic raw material powder by hot air supplied into the drying chamber. A method for producing a dielectric ceramic raw material powder, comprising: 2. In the second step, one or more compounds selected from the group of compounds containing the sub-component element are added to the slurry after the completion of the first step, and a perovskite (ABO ₃ ) ceramic is added. 2. The method for producing a dielectric ceramic raw material powder according to claim 1, which is a step of depositing or adhering at least a part of the accessory component element as a sparingly soluble salt, hydroxide or oxide on the particle surface of the raw material powder. . 3. The second step comprises mixing the perovskite-based ceramic raw material powder contained in the slurry after the completion of the first step and one or more compounds selected from the group of compounds containing the sub-component element. _3. A step of depositing or adhering at least a part of the accessory component element as a sparingly soluble salt, hydroxide or oxide on the particle surface of the perovskite (ABO ₃ ) based ceramic raw material powder by a reaction. A method for producing the dielectric ceramic raw material powder described. 4. The sub-component element is a rare earth element, Ba,
Li, Bi, Zn, Mn, Al, Si, Ca, Sr, C
The method for producing a dielectric ceramic raw material powder according to any one of claims 1 to 3, which is one or more elements selected from o, V, Nb, Ni, Cr, Fe and Mg. 5. The method for producing a dielectric ceramic raw material powder according to claim 1, wherein the perovskite (ABO ₃ ) ceramic raw material powder is barium titanate. 6. The dielectric ceramic raw material powder obtained after the third step is calcined.
6. The method for producing a dielectric ceramic raw material powder according to any one of 5 above.