JPH04132651A - Production of ceramic structure - Google Patents

Abstract

PURPOSE:To obtain the title structure with density close to the theoretical value by calcining a mixed raw material composition which is prepared by adding to a suspension of oxide ceramic raw material powder an organic compound containing the constituent elements for said raw material to effect coating the surface of the raw material powder with highly active fine particles. CONSTITUTION:Firstly, oxide ceramic powder is suspended in an organic solvent into a suspension. Thence, a liquid organic compound or a solution of this compound containing an element same as or different from the constituent element for said oxide is admixed with the above suspension followed by distillation. Thus, fine particles of said organic compound are deposited on the surface of the ceramic powder. The mixed raw material composition thus obtained is then formed and calcined.

Description

[Detailed Description of the Invention] “Industrial Application Field” The present invention relates to dielectric porcelain, transparent ceramics, insulating porcelain,
The present invention relates to a method of manufacturing metal sintered bodies, magnetic sintered bodies, and other ceramic structures. More specifically, the present invention relates to a method for manufacturing a ceramic structure by obtaining a mixed raw material composition that has two contradictory properties of ceramic powder: easy sinterability and easy handling.

[Prior art] This type of ceramic structure is made by applying ceramic paste to a film sheet or the like to obtain a desired green sheet, or by forming ceramic powder into a desired molded body and then firing it. .

In recent years, methods for manufacturing electronic materials such as ceramic porcelain among ceramic structures have been made more uniform and finer in order to make electronic devices smaller, higher in quality, and lower in price. , thereby achieving low-temperature sintering. As a method for uniformly refining this ceramic raw material to a diameter on the submicron order, firstly, the pulverization method involves repeating the preparation, calcining, and pulverization of the raw materials, and the pulverization is performed using a bead mill, etc., or the second method is the metal alkoxide method. Examples include chemical synthesis methods such as coprecipitation method. Ceramic paste is manufactured by adding and mixing additives such as an organic solvent and a binder to this uniformly finely divided ceramic powder.

Conventionally, the manufacturing method for this type of ceramic paste is as follows:
The alkoxide solution of the metal element constituting the thick film is wet-reacted to form a metal oxide or metal hydroxide, an organic binder, a solvent, etc. are added, and the excess solvent and/or water is removed by vacuum distillation to form the surface. A method for producing a thick film forming paste having a desired composition and high activity is disclosed (Japanese Patent Laid-Open No. 1286905).

Since this method does not require operations such as filtration, washing, and dehydration of metal oxides, it prevents the contamination of impurities during the operation process, and also prevents compositional deviations and surface activity due to elution and evaporation of constituent components. It has the advantage of being able to prevent deterioration and generate paste through a series of operations.

[Problem to be solved by the invention] Powder that is easily sinterable can be obtained by the above-mentioned pulverization method and chemical synthesis method, but if the powder is infinitely refined in pursuit of sinterability, the pulverization method will produce impurities. Also, due to the increase in the surface active energy of the powder, when it is made into a paste, the viscosity of the paste increases and it becomes easier to gel, or the powder becomes difficult to disperse uniformly, causing the powder to deteriorate when molded. There were problems such as the filling rate of the body decreased and the sintered density was difficult to approximate the theoretical density.

In particular, the composition particles obtained by the method for producing a paste for forming a thick film have an extremely fine particle size of less than submicron and have a very large specific surface area. They tend to aggregate with each other, resulting in poor handling properties, which may lead to the above-mentioned problems.

The first object of the present invention is to provide a method by which an easily sinterable mixed raw material composition can be obtained by coating the surface of oxide powder with fine particles.

Secondly, the mixed raw material composition can be manufactured in a continuous operation, and it is difficult to agglomerate after manufacturing, making it easy to handle. Moreover, the firing temperature after molding is low, and a sintered density close to the theoretical density can be obtained after firing. An object of the present invention is to provide a method for manufacturing a structure.

[Means for Solving the Problems] The present inventors have discovered that if an oxide ceramic powder with a particle size on the submicron order is used as a core and the surface of this powder is coated with particles even finer than this powder, a submicron particle size can be obtained. The present invention was achieved by focusing on the fact that, compared to powders with extremely fine particle sizes of less than microns, agglomeration between powders is less likely to occur, and low-temperature sintering is possible due to the fine particles coated during firing. .

In order to achieve the above object, the method for manufacturing a ceramic structure of the present invention comprises: dispersing oxide ceramic powder substantially insoluble in an organic solvent in the solvent to prepare a suspension; A liquid organic compound or a solution of an organic compound containing either or both of the same or different elements constituting the oxide is added to and mixed with the suspension, and the mixed liquid is distilled to produce the ceramic powder. In this method, a mixed raw material composition in which the organic compound fine particles or hydroxide fine particles are precipitated on the surface of the body is prepared, the mixed raw material composition is shaped, and then fired.

The present invention will be explained in detail below.

The starting material of the present invention is an oxide ceramic powder that is substantially insoluble in organic solvents. This oxide ceramic powder is made of fine powder made by known pulverization methods and chemical synthesis methods.
From the viewpoint of sintering characteristics, a particle size in the submicron range, preferably 05 μm or less, is used, but since the purpose is to lower the sintering temperature, there is no particular limitation.

This oxide ceramic powder is suspended in an organic solvent to prepare a suspension. Examples of the organic solvent include alcohols with a low boiling point of 50 to 100'C, benzene, and acetone, which easily volatilize during distillation.

When forming powder or flocs in a solvent, it is preferable to add a dispersant or to disperse the powder using a mixing/dispersing machine such as a mill.

Organic compounds are added to this suspension and mixed.

This organic compound is a liquid organic compound or a solution of an organic compound containing either or both of the same or different elements as the elements constituting the oxide. The amount of organic compound added can be arbitrarily controlled at the particle center of the oxide ceramic powder, and is 1% by weight per 100% by weight of the oxide ceramic powder.
It is about 10% by weight. If it is less than 1% by weight, the molded body will not be sintered at low temperatures, and if it exceeds 10% by weight, particles will tend to aggregate with each other.

Next, the mixture of the suspension and the organic compound is distilled at a temperature close to the boiling point of the organic solvent. As a result, the solvent is removed, and organic compound fine particles are precipitated on the surface of the oxide ceramic powder in this liquid mixture, forming a coating layer of fine particles. If the organic compound is soluble in the organic solvent, or if it evaporates together with the organic solvent during distillation and a coating layer of fine particles is not formed, After hydrolyzing the metal alkoxide in the mixture, or
After adding a precipitant to the mixture, each is distilled.

During hydrolysis, the oxide or hydroxide of the metal constituting the alkoxide is converted into the metal oxide powder by adding to the mixture an equimolar amount of water or several times the molar amount of water required for hydrolysis. A coating layer of fine particles is formed on the surface of the particles.

Further, the addition of a precipitant is carried out when a water-soluble organic compound such as a carboxylic acid salt is selected as the organic compound to be added to the suspension. By adding a precipitating agent, fine particles of hydroxide of an organic compound are precipitated on the surface of the oxide ceramic powder. As the precipitant, ammonia, oxalic acid, ammonium oxalate, ammonium carbonate, etc. are used. The particle size of the fine particles constituting the coating layer is about 0.01 to 0.05 μm, and a plurality of coating layers are laminated.

If the solvent is completely removed by distillation, a powder mixed raw material composition can be obtained. In addition, if an organic solvent with a higher boiling point than the organic solvent used to prepare the suspension is added before distillation, and distillation is carried out to volatilize only the low-boiling point 41 solvent, the high-boiling point organic solvent can be used as a dispersion medium. A mixed raw material composition for a paste-based paste is obtained. When the above-mentioned water-soluble organic compound is selected as the organic compound, a water-based paste can be obtained.

It is preferable to add a binder before or after distillation, or before or after precipitation, in order to bond the particles together and increase the strength of the molded body. The addition of the binder before distillation or precipitation is carried out before, after or simultaneously with the addition of the organic compound to the suspension, but it is preferably carried out after the preparation of the mixture. When the fine particles are formed in a liquid by distillation or precipitation, or when the fine particles are deposited on the surface of the oxide ceramic powder, the binder forms a coating layer of the fine particles. Further, the addition of the binder after distillation or precipitation is preferably carried out after a coating layer of fine particles is formed and then heated and aged. The heating and aging conditions may be the same as those for hydrolyzing metal alkoxides, and the aging temperature is the boiling point of the solvent used, for example, 70-80'C for alcohol.
The aging time is about 1 to 3 hours.

Examples of the binder used before and after distillation include solvent-based polyvinyl butyral and methyl cellulose.

Examples of the binder used before and after precipitation to obtain the mixed raw material composition of the water-based paste include water-based polyvinyl alcohol.

When the mixed raw material composition obtained by distillation is a paste, the binder is about 5% by weight based on 100% by weight of the oxide.
~10% by weight, and when the mixed raw material composition is a powder, it is added in an amount of about 1 to 5% by weight.

Further, if necessary, add a dispersant, plasticizer, etc., and stir thoroughly. Examples of dispersants include glycerin, oleic acid, glycerin monooleate, glycerin tristearate, etc., and examples of plasticizers include dioctyl phthalate,
Examples include phthalic acid esters such as dibutyl phthalate, and glycol esters such as triethylene glycol and polyalkylene glycol. The dispersant is about 0.1 to 3% by weight and the plasticizer is about 1 to 4% by weight based on 100% by weight of the oxide.
are added respectively.

The powder mixed raw material composition obtained in this way is molded into a predetermined shape by a dry molding method using a press, and the base mixed raw material composition is molded into a predetermined shape by a doctor blade method or a printing method. . Molded body for 5 to 10 hours, 400 to 70
After degreasing by heating at 0° C., the mixed raw material composition is sintered and a ceramic structure is obtained by firing.

It goes without saying that the present invention is applicable to raw materials other than the various raw materials exemplified in the above description that can achieve the functions and effects aimed at by the present invention.

[Function] By using oxide ceramic powder with a particle size on the submicron order as a core and coating or adsorbing the surface of this powder with particles even finer than this powder, all the powder can be removed as in the conventional method. Compared to powders with extremely fine particle sizes of less than submicrons, the specific surface area of the powder is smaller, making it difficult for powders to agglomerate, and the fine particles coated during firing induce sintering between the particles. To facilitate sintering, all powders are sintered at temperatures as low as those with extremely fine submicron particle sizes.

[Effects of the Invention] As described above, according to the present invention, a ceramic raw material powder having a particle size on the submicron order obtained by a conventional chemical synthesis method is used, and this ceramic raw material powder is added to a suspension of this raw material powder. By adding an organic compound containing one or more constituent elements or a second element different from the constituent elements, or both elements, the surface of the ceramic raw material powder is coated with extremely fine particle sizes of less than submicron with high surface activity. By coating or adsorbing fine particles on a particle-by-particle basis, an easily sinterable mixed raw material composition can be easily produced in a continuous operation. This mixed raw material composition has a smaller specific surface area of the powder, which makes it difficult for powders to agglomerate together, and has good handling properties, compared to those in which all the powders have extremely fine particle sizes of less than submicrons. Become.

When the mixed raw material composition of the present invention is molded and fired, the presence of fine particles on the surface of the ceramic raw material powder can arbitrarily control the solid solution phase at the grain boundaries of the ceramic, improving the physical and electrical properties of the ceramic raw material powder. The sinterability can be improved without impairing the sinterability, and a ceramic structure with a sintered density close to the theoretical density can be obtained.

The ceramic structure of the present invention can be widely used in ceramics such as dielectric ceramics, transparent ceramics, insulating ceramics, metal sintered bodies, and magnetic sintered bodies.

[Example] Next, Examples of the present invention will be described in detail together with Comparative Examples, but the examples shown below are merely examples, and are not intended to limit the technical scope of the present invention.

<Example> Dielectric ceramic composition described in JP-A No. 62-138360 X(Pb, -utau)(zr+-VTIV)0
8” (1-X)Pb(Mg+zaNb2is)Os
Of which, X = 0.15. u=0.13. v
= 1.0 of 0, 15 (Pbo, atLao, +
a) (Ti)03 ・0.85Pb(Mg+/3Nb
PLZT-PMN oxide powder of 2za)03 was synthesized by a chemical synthesis method.

Lead nitrate 0.73 mol, magnesium nitrate (hexahydrate) 0
．． 21 moles of lanthanum nitrate and 0.015 moles of lanthanum nitrate were dissolved in 700 m of water. Add 0 titanium isopropoxide to this solution.
．． Hydrolysis was carried out by dropping 150 ml of an inpropyl alcohol solution containing 113 mol of niobium chloride and 0.43 mol of niobium chloride to obtain a precipitate. Add 3 diethylamine to this precipitate.
00 ml was added to precipitate the remaining dissolved elements, and the precipitate was filtered, dried, and then calcined at 750°C. The calcined product is ground in a ball mill to give an average particle size of 0.2 to 0.3.
I) LZi'-PMN oxide powder of μm was obtained.

Add 50 ml of isopropyl alcohol to 100 g of the oxide powder, and add 1 ml of resistin as a dispersant.
g was added and dispersed well to prepare a suspension. This suspension contains 15.3X 10-3 moles of lead butoxide, 4.43X 10-3 moles of magnesium acetate, 0.30X 10-3 moles of lanthanum isopropoxide, 2.34X 10-3 moles of titanium isopropoxide, and Niobium isopropoxy l''8.85X 10-3 molar isopropyl alcohol solution (30mf) was added and mixed uniformly.

2 ml of water was added to this mixture, and the alkoxide was hydrolyzed at 80°C for 1 hour. After hydrolysis, 25 m of terpineol solution in which 5 g of polyvinyl butyral was dissolved.
Q was added and distilled at atmospheric pressure and 120°C to obtain a mixed raw material composition for paste.

<Comparative example> 50 m fl of isopropyl alcohol was added to 100 g of the PLZT-I)MN oxide powder of the example, and 1 g of lecithin was added as a dispersant to disperse well and suspend lfk. did. 25 ml of terpineol solution in which 5 g of polyvinyl butyral was dissolved in this suspension Hk
was added and distilled at 120° C. under atmospheric pressure to obtain a paste raw material composition.

The pastes obtained in the above Examples and Comparative Examples were screen printed on polyester film sheets (trade name Mylar Sheet) to obtain ceramic green sheets of 10 x 10 x 1 mm. 50 of these green sheets
After degreasing by heating at 0°C for 5 hours, 900°C, 95
It was baked at 0°C, 1000°C, 1050°C, and 1100°C for 2 hours each. The results are shown in Table 1.

The sintered density of the green sheet in Table 1 is determined when the firing temperature of the comparative example is 1.
This corresponds to the sintered density at 050° C., and it was found that the green sheets of Examples had high sinterability at low temperatures.

Claims (1)

[Claims] 1) A suspension is prepared by dispersing an oxide ceramic powder that is substantially insoluble in an organic solvent in the solvent, and a suspension is prepared by dispersing an oxide ceramic powder that is substantially insoluble in an organic solvent, A mixture in which a liquid organic compound or a solution of an organic compound containing either or both elements is added to the suspension and mixed, and the mixed liquid is distilled to precipitate the organic compound fine particles on the surface of the ceramic powder. A method for manufacturing a ceramic structure, comprising preparing a raw material composition, molding the mixed raw material composition, and then firing the mixed raw material composition. 2) The solution of the organic compound is an organic solution of a metal alkoxide, and after the metal alkoxide in the mixed solution is hydrolyzed, it is distilled to precipitate fine particles of hydroxide of the organic compound on the surface of the ceramic powder. The method for manufacturing a ceramic structure according to claim 1, wherein a mixed raw material composition is prepared. 3) The ceramic structure according to claim 1, wherein a precipitating agent is added to the mixed liquid and then distilled to prepare a mixed raw material composition in which hydroxide fine particles of the organic compound are precipitated on the surface of the ceramic powder. Production method. 4) The method for manufacturing a ceramic structure according to any one of claims 1 to 3, wherein a binder is added before distillation. 5) The method for manufacturing a ceramic structure according to any one of claims 1 to 3, wherein a binder is added after distillation.