JPS6065759A - Manufacture of ceramic sintered body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a ceramic sintered body using a metal alkoxide as a starting material, and in particular to a ceramic sintered body thin film/sheet having high density and high translucency. Relating to a manufacturing method.

[Background technology and its problems]

Conventionally, electronic components using ceramic sintered bodies with excellent electrical properties have been known, but with the miniaturization of electronic devices that house these electronic components,
Haa l-yo P7→Yu・l/77 Kyoyo Ita finely processed,
Attempts have been made to make the electronic components ultra-small and lightweight. For example, so-called multilayer ceramic capacitors, which are applied to capacitors to increase their capacity, are attracting attention.

By the way, in order to achieve both miniaturization and large capacity in such capacitors, it is necessary to reduce the thickness of the ceramic sintered body that is the dielectric layer on the order of microns, and to make it more uniform and dense. There is.

However, conventionally, the above-mentioned ceramic sintered bodies have been manufactured by sintering using solid-phase reaction, that is, by press-forming fine particulate raw materials and firing them at high temperatures. is relatively large, there is a limit to how thin the obtained sintered body can be made. For example, in ceramic sintered bodies used in ordinary single-phase capacitors, problems such as poor withstand voltage will occur if the ceramic particles that make up the sintered body do not overlap in multiple layers. In the manufacturing method of 20-30
The limit is μm. However, with the above manufacturing method,
Non-uniform secondary aggregation is likely to occur, and pores occupy a large proportion, making it difficult to achieve high density.

Furthermore, conventionally, methods have been developed to manufacture ceramic thin film elements by means such as physical vapor deposition, but these methods have not been put to practical use due to many problems such as the generation of pinholes and microcracks during firing.

On the other hand, the above-mentioned ceramic sintered body is also used in the field of optical technology, for example, in thin film waveguides for optical ICs, electro-optical elements for optical modulation, and the like.

In this type of element, the transparency of the ceramic sintered body is particularly problematic, and in order to manufacture such transparent ceramics, expensive equipment such as a hot press must be used, which increases manufacturing costs. At the same time, productivity is also declining. In addition, the above transparent ceramic sintered body is
Like single crystals, it is treated as a bulk material and cut out by machining before use, so there is a limit to how thin it can be made.

Therefore, conventionally, the so-called alkoxide method using metal alkoxide as a raw material has drawbacks such as difficulty in controlling the temperature of the ceramic as described above and difficulty in removing air bubbles, which are the cause of pores.

[Purpose of the invention]

Therefore, the present invention was proposed in order to solve the above-mentioned drawbacks of the prior art, and it is an object of the present invention to provide a method for manufacturing a ceramic sintered body that can produce an extremely thin ceramic sintered body thin film or thin plate. It is an object of the present invention to provide a manufacturing method capable of obtaining a homogeneous and high-density ceramic sintered body.

Furthermore, an object of the present invention is to provide a method for manufacturing a ceramic sintered body that can obtain a ceramic sintered body having high translucency without using expensive equipment.

[Summary of the invention]

In order to achieve the above objects, the present invention hydrolyzes a metal alkoxide to produce a metal hydrate, tetracamide or oxide, and further adds a pH adjuster to form a colloidal solution. This method is characterized in that the colloidal solution is contracted and solidified under reduced pressure and then fired. - [Example] Hereinafter, a method for manufacturing a ceramic sintered body according to the present invention will be explained in accordance with the process order.

In the present invention, a metal alkoxide, which is a derivative in which the hydrogen of the hydroxyl group of an alcohol is replaced with a metal, is prepared as a starting material.

This metal alkoxide can be obtained by directly reacting these metals with an alcohol when the metal is a strongly positive element with a valence of up to 3, such as an alkali metal, an alkaline earth metal, or a lanthanide. In the case of other metals, it can be obtained by reacting a metal halide, particularly a metal chloride, with an alcohol instead of the metal.

The above-mentioned metal is appropriately selected depending on the composition of the intended ceramic sintered body, and is, for example, titanium.

Examples include Kuntal Ta, aluminum A4, zinc Zn+silicon Si, and germanium Ge.

Further, the alcohol mentioned above is methanol.

Ethanol, isopropanol, n-butanol.

Examples include tertiary butanol.

First, the metal alkoxide is hydrolyzed using water. This hydrolysis produces and precipitates metal hydrates, hydroxides, or oxides.

Next, the precipitate obtained by the above hydrolysis is stirred using a homogenizer or the like to form a suspension, and further added with hydrochloric acid etc.
The pH value of the solution is adjusted by adding an H adjuster, and the solution is peptized using a homogenizer or ultrasonic waves to prepare a colloidal solution.

In this colloidal solution, the size of colloidal particles dispersed in the solvent is about 100A or less.

Subsequently, the colloidal solution is contracted and solidified under reduced pressure using a pressure reducing device as shown in FIG.

The pressure reducing device includes a container 1 such as a petri dish in which the colloidal solution is placed, a heater 2 on which the container 1 is placed and which heats the colloidal solution in the container 1, a bell jar 3 that accommodates the container 1 and the heater 2, and a liquid nitrogen 4. It consists of a trap 5 which is cooled by a vacuum pump 6, and a vacuum pump 6 such as a diffusion pump or a rotary pump. Then, the colloidal solution is poured into the container 1, and while being heated by the heater 2, the pressure inside the bell jar 3 is reduced by the vacuum pump 6. Then, first, the solvent of the colloidal solution evaporates,
Furthermore, the colloidal particles are brought into close contact with each other, contracted, solidified in an extremely dense state, and dried.

The pressure inside the bell jar 3 may be reduced to 10 Torr or less, but it is preferable to reduce the pressure to 1 Torr or less.

The heating by the heater 2 is preferably performed just before the colloidal solution in the container 1 boils under the reduced pressure;
It is desirable to set the temperature to 0°C.

By firing the thin film of colloidal particles obtained by shrinking and solidifying under reduced pressure, all water molecules contained in the thin film are removed, and the colloidal particles become hydrated metals or hydroxides. In some cases, these become oxides and a thin film of ceramic sintered body is obtained. The resulting ceramic sintered body is made by shrinking and solidifying colloidal particles with a particle size of 100A or less, so the proportion of pores, so-called pores, existing between the particles is reduced, and There is no careless generation of pores due to non-uniform secondary aggregation, resulting in extremely high density.

By the way, the present invention is applicable not only to ceramic sintered bodies made of single metal oxides, but also to general A'B03 (where A is Ba, 'Ca', Sr, Mg + P).
bConfirmation B represents Ti, Zr, Hf, Sn), lithium niobate LiNb0:+, lithium quantalate Li
Ceramics such as T a Os, lanthanum lead zirconate titanate PII, ZT, potassium quantal niobate K
It can also be applied to the production of transparent ceramics such as TN.

In this case, a colloidal solution having a predetermined metal element ratio may be prepared by a sol mixing method or a composite alkoxide method.

That is, in the above sol mixing method, the alkoxides of each component metal of the desired ceramic are synthesized separately,
It is hydrolyzed to form a colloidal solution, and these colloidal solutions are mixed at a predetermined composition ratio. Therefore, this mixed colloidal solution is contracted and solidified under reduced pressure.
By firing, a ceramic sintered body having a predetermined metal composition is obtained.

On the other hand, the above-mentioned composite alkoxide method uses a composite alkoxide as a starting material, and as in the case of using a single-metal metal alkoxide described above, the various steps of hydrolysis, peptization, shrinkage solidification under reduced pressure, and calcination are performed. Through these steps, a ceramic sintered body having a predetermined metal element ratio can be manufactured. This composite alkoxide can be easily synthesized by a neutralization reaction between a basic alkoxide such as an alkali metal alkoxide and an acidic alkoxide such as an alkoxide of zinc or aluminum. In addition, composite alkoxides of alkaline earth metals, rare earth metals, and aluminum, gallium, niobium, tantalum, etc.
It can be synthesized by reacting metal alkoxides with each other or by reacting a chloride of the alkaline earth metal or rare earth metal with a composite alkoxide of a metal such as aluminum and potassium. Furthermore, in such a complex alkoxide, the third. It is also possible to introduce a fourth metallic element.

As described above, in the present invention, colloidal particles of metal hydrates, hydroxides, or oxides obtained by hydrolyzing metal alkoxides are shrunk and solidified under reduced pressure, and the colloidal particles become highly dense. Since the agglomerated material is fired, it is possible to obtain a homogeneous and extremely dense ceramic sintered body, and therefore it is possible to obtain a ceramic sintered body having high translucency. In particular, since the colloidal particles mentioned above have extremely small particle diameters of 100A or less, the proportion of pores existing between the particles is small, and since they are contracted under reduced pressure, moisture removal etc. can be done at low temperatures. Uniform secondary agglomeration is eliminated and the density is even higher.

Furthermore, since the particle size of the colloidal particles is extremely small, it is possible to obtain highly dense and thin particles on the order of micrometers. For example, it is possible to provide a ceramic sintered body film with a thickness of 10 pm or less as a dielectric layer of a single-phase capacitor. In particular, if a grain growth inhibitor is mixed into the colloidal solution, it is possible to further reduce the thickness during firing.

Furthermore, the above-described manufacturing method does not require large-scale equipment, has high productivity, and can reduce manufacturing costs.

Furthermore, it is also possible to apply the colloidal solution to minute locations.

Furthermore, 1. By shrinking and solidifying under reduced pressure, it is possible to increase the devitrification temperature during heat treatment. For example, in the case of titanium dioxide T i O2, it devitrifies at about 300°C in the conventional method, but it devitrifies at about 300°C by reducing the pressure.
No devitrification up to 50°C.

Next, specific examples according to the present invention will be explained.

It goes without saying that the present invention is not limited to this specific example.

[Specific example] Approximately 70 mol of titanium 1-line propoxide Ti (OC3H7") is added to 100 mol of pure water to give 41 mol of titanium te-line propoxide Ti (OC3H7").
The mixture was gradually added dropwise to warm water at ℃ while stirring. Next, in order to disperse the white flocculent precipitate produced here and improve the hydrolysis rate, high-speed stirring was immediately performed using a homogenizer for several minutes. The emulsion thus produced was placed in an Erlenmeyer flask and refluxed for about 1 hour. Next, dilute hydrochloric acid, which had been adjusted in advance so that the molar ratio of hydrochloric acid HC7 to the above titante 1-line propoxide was 01, was added and peptized for 15 hours.

During this time, peptization was promoted using stirring and ultrasonic waves. The colloidal solution thus obtained was stored at 80°C for several days. Next, this colloidal solution was poured into a container 1 of a pressure reducing device shown in FIG. 1, and the pressure was reduced to below IQTorr to cause it to shrink and solidify. The temperature at this time was 4.0 to 60°C.

By shrinking and solidifying under reduced pressure, a transparent thin plate as shown in the photograph in FIG. 2 was obtained. This transparent thin plate (thickness 58μm)
FIG. 3 shows a comparison of the transmission spectrum a of the sample with the transmission spectrum b of the sample dried in a nitrogen stream (thickness: 80 μm). From FIG. 3, it can be seen that the material that is shrunk and solidified under reduced pressure has much better translucency.

Next, the transparent thin plate was heated at a rate of 40°C per hour and fired at 1500°C for 3 hours. The obtained ceramic sintered body is photographed in FIG. As is clear from FIG. 4, it was possible to obtain a ceramic sintered body having high translucency.

In addition, FIG. 5 is a graph showing the relationship between firing temperature and the number of pores per unit area of the fracture surface of the ceramic sintered body obtained.
Figure 6 shows graphs showing the relationship between firing temperature and pore diameter. Based on the results obtained from the graphs in FIGS. 5 and 6, FIG. 7 shows the change in porosity of the ceramic sintered body, determined from the average pore diameter and the average number of pores, with respect to the firing temperature. This porosity is 13 in ceramic sintered bodies obtained by dry forming using conventional solid phase reaction.
It is said to be 20-30% at 00°C and around 10% at 1400°C, and as is clear from Figure 7, according to the present invention, high density is achieved with a value much lower than these values. That is clear.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to form an extremely thin homogeneous and high-density ceramic sintered body.

Further, according to the present invention, it is possible to manufacture a ceramic sintered body having high translucency without using expensive equipment.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the configuration of a pressure reducing device used in the present invention. Figure 2 is a photograph of a transparent thin plate obtained by shrinkage and solidification under reduced pressure, and Figure 3 is a graph comparing its transmission spectrum with that of one obtained by conventional methods. Fig. 4 is a photograph showing an example of the ceramic/cus sintered body obtained by the present invention, Fig. 5 is a graph showing the relationship between the firing temperature and the number of pores, and Fig. 6 is the graph showing the relationship between the firing temperature and the pore diameter. Figure 7 is a graph showing the relationship between firing temperature and porosity.Patent applicant Mimi Koike, representative patent attorney for Sony Corporation 1) Sakae Mura - Procedural amendment (method) Patent Mr. Kazuo Wakasugi, Director of the Agency 1. Indication of the case 1982 Patent Application No. 170231 2. Name of the invention Relationship to the case Patent RR applicant address 6-7-35, Kitashina, Tokyo Parts Co., Ltd. Name (2)
18) Sony Corporation (0) Representative: Norio Ohga 4, Agent: 105 January 11, 1980 (Delivery date: January 31, 1980) (7-1) Specification, Page 13, No. 2 The sentences from line 1, ``Under the above reduced pressure'' to page 14, line 6, ``It is obvious.'' are amended as follows. [A transparent thin plate was obtained by shrinkage assimilation under reduced pressure. The transmission spectrum a of this transparent thin plate (thickness: 58 μm) is compared with the transmission spectrum b of the transparent thin plate (thickness: 80 μm) dried in a nitrogen stream, as shown in FIG. From FIG. 2, it can be seen that the material that is shrunk and solidified under reduced pressure has much better translucency. Next, the transparent thin plate was heated at a rate of 40°C per hour and fired at 1500°C for 3 hours. The obtained ceramic sintered body had high translucency. In addition, Fig. 3 is a graph showing the relationship between the firing temperature and the number of pores per unit area of the fractured surface of the ceramic sintered body obtained.
FIG. 4 shows graphs showing the relationship between firing temperature and pore diameter. Based on the data obtained from the graphs in FIGS. 3 and 4, FIG. 5 shows changes in the porosity of the ceramic sintered body, which can be determined from the average pore diameter and the average number of pores, with respect to the firing temperature. This porosity is 13 in ceramic sintered bodies obtained by dry forming using conventional solid phase reaction.
It is said to be 20-30% at 00°C and around 10% at 1400°C, and as is clear from Figure 5, according to the present invention, it is much lower than these values [Figure 2 shows the shrinkage under reduced pressure]. 2 is a graph showing a comparison of the transmission spectrum of a transparent thin plate obtained by solidification with the transmission spectrum of one obtained by a conventional method. Figure 3 is a graph showing the relationship between the firing temperature and the number of pores in the ceramic sintered body obtained, Figure 4 is a graph showing the relationship between the firing temperature and the pore diameter of the ceramic sintered body obtained, and Figure 5 is the firing temperature. Graph (7-3) showing the relationship between the porosity and the porosity of the ceramic sintered body obtained. Figures 2 and 4 in the attached drawings are deleted. (7-4) As indicated in red on the attached sheet, in the attached drawings, Figure 3 is replaced by Figure 2, Figure 5 is replaced by Figure 3, Figure 6 is replaced by Figure 4, and Figure 7
The figures have been corrected to Figure 5. (that's all)

Claims (1)

[Claims] Hydrolyzing a metal alkoxide to produce metal hydrates, hydroxides, or oxides, adding a pH adjuster to form a colloidal solution, shrinking and solidifying this colloidal solution under reduced pressure, and then firing. A method for producing a ceramic sintered body characterized by: