JPH01257169A - Ceramic vessel for calcining - 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] [Object of the Invention] (Industrial Application Field) The present invention relates to a firing container, and more particularly to a ceramic firing container suitable for heat treatment and firing of ceramic materials, particularly phosphors. .

(Prior Art) Various materials have been known as phosphor materials used in cathode ray tubes, etc., such as ZnS:Ag.
.

ZnS: Sulfide type such as Cu*A1, A l 203°Er2O3 Y2O28: Eu1 Ga202S: Tb1 (Y"Ga) 202S: Oxide type such as Tb, Y
p V S i 04: E u 1ZnSi03:M
n.

Y2SiO5: Silicates such as Ce-Tb, Ca W
Tungstate salts such as 04, Ca(PO4)2I
ICa(FφC1): Sb-Mn1SrOIJSrF
In the heat treatment or firing process of the phosphor materials mentioned above, where oxyacid-based materials such as Mn and 28203:Mn and their mixtures are manufactured, alumina or quartz are conventionally used as firing containers. Crucibles and trays made of aluminum are mainly used.

(Problems to be Solved by the Invention) However, conventional alumina containers have a problem of poor thermal shock resistance.On the other hand, quartz baking containers crystallize when the heating temperature exceeds 1000°C. There is a tendency for the strength of the container to deteriorate over time. Therefore, none of these containers can sufficiently withstand continuous use over a large number of times, and is therefore unsatisfactory in terms of durability and economy.

In addition to the ceramic containers mentioned above, heat treatment containers made of alloys that have excellent thermal shock resistance and mechanical strength and can withstand relatively high temperatures are also known; Since containers tend to react with the phosphor material that is the object of heat treatment, it is not preferable to use them for such treatments.

The present invention has been made in view of the problems of the prior art described above, and has excellent thermal shock resistance and durability, and does not cause undesirable reactions with the material to be treated even under high-temperature heating conditions. The purpose is to provide a container for firing ceramics.

[Structure of the invention]

(Means and effects for solving the problems) Summary of the invention The ceramic firing container of the present invention is characterized in that a surface layer made of alumina is formed on the surface of the container body made of a porous ceramic base material. .

DETAILED DESCRIPTION OF THE INVENTION The ceramic firing container of the present invention will be described below with reference to specific examples shown in the drawings.

The ceramic firing container of the present invention has a surface layer made of alumina (A1203) formed on the surface of a porous ceramic base material 1, as shown in the cross-sectional view of FIG.

As the ceramic base material 1, silicon carbide (S i C) can be particularly preferably used from the viewpoint of mechanical strength, thermal shock resistance, and the like. This ceramic base material has a porous structure. Although the porosity in this case is not particularly limited, a porosity in the range of 20 to 30% is suitable in terms of mechanical strength and thermal shock resistance. Further, since SiC has excellent moldability, it is also advantageous in that container bodies of various shapes and sizes can be obtained to suit various uses.

The alumina surface layer 2 formed on the surface of the ceramic base material 1 is chemically stable and inert even at high temperatures, and does not cause any interaction with the firing atmosphere or the object to be fired. It has excellent properties. In particular, it is important that the ceramic material to be processed be thermally and chemically stable when firing materials such as phosphors, which are easily affected by chemical properties. . Therefore, in the present invention, the coating state of the surface layer 2 is such that the open pores existing on the surface of the ceramic base material 1 are covered with alumina, and the surface layer of the ceramic base material 1 is covered with an alumina surface layer of an appropriate thickness. It is preferable that the alumina is formed in order to exhibit the characteristics of alumina.

In general, the firing process of ceramic materials, especially phosphor materials, may require a temperature of 1300°C or higher, but when firing in a container made only of SiC, the metal Si inevitably contained in the container and the fluorescent There is a problem in that the phosphor material reacts with the phosphor material, which adversely affects the properties of the phosphor material (for example, the brightness decreases). In the present invention, by actively utilizing the characteristics of SiC, which has excellent mechanical and thermal properties, and the characteristics of alumina, which has excellent chemical stability, we have developed a synergistically excellent firing container. Effects can be obtained.

In the present invention, the appropriate thickness of the alumina surface layer is usually about 0.01 to 1 mm, although it varies depending on the size, shape, and purpose of the container.

Next, a method for manufacturing the firing container of the present invention having the above structure will be explained.

First, in order to obtain a container body made of a porous ceramic base material, a suitable sintering aid (for example, carbon, boron compound, AI
compound, Y compound, etc.) or not, the material powder is prepared.

Next, this material powder is molded into a crucible shape by molding means such as metal molding or rubber molding. Further, this molded body is degreased and then fired at a temperature of 2000 to 2200°C to obtain a porous ceramic base material. The porosity of the base material in this case can be adjusted as appropriate by the particle size of the raw material powder and the firing temperature.

In addition to the above method, a slip casting method can also be used to obtain the container body made of a porous ceramic base material. In this method, first, a ceramic powder using a predetermined base is mixed with an appropriate amount of water, a dispersant, and a binder to obtain a slip.
This slip was poured into a plaster mold of a predetermined shape to obtain a crucible-shaped molded body, and after degreasing in the same manner as above,
By firing, a container body made of a porous ceramic base material is formed.

On the other hand, the alumina surface layer is formed as follows.

That is, first, alumina powder is prepared, and a suitable solvent such as water, ethanol, butyl acetate, tetralin, etc. is added to the alumina powder to prepare a slurry for immersion. The alumina used in this case is preferably one with as high purity and fineness as possible (for example, 1 μm or less). Further, the type of solvent is not particularly limited, but from the viewpoint of quick drying properties, organic solvents are preferably used.

In the thus obtained alumina-containing slurry, the container body made of the porous ceramic base material already obtained is immersed to coat the surface of the container body with alumina.

The immersion in this case is preferably performed under reduced pressure. If you want to increase the thickness of the alumina surface layer, it is necessary to repeat the above dipping treatment multiple times, and the layer thickness of the alumina surface layer must be adjusted as appropriate depending on the number of dipping treatments, dipping time, and alumina concentration. I can do it.

After the immersion treatment as described above, the manufacturing process is completed by performing a baking treatment at a temperature of 1300 to 1600°C.

(Example) For α-5iC with an average particle size of 7 μm, 1% by weight of carbon black, 0.5% by weight of 84 C, and an appropriate amount of water,
A dispersant and a binder were added and mixed in a pot mill for 24 hours to obtain a slurry casting slip.

Next, this slip was poured into a container-shaped plaster mold to obtain a crucible-shaped molded body. Furthermore, after degreasing, 21
A container body made of high purity porous SiC with a porosity of 22% was obtained by firing at a temperature of 50° C. for 4 hours.

The obtained container body was immersed under reduced pressure in a slurry consisting of 500 cc of ethanol and 400 g of high-purity alumina.
After drying, the container was fired at a temperature of 1500° C. for 2 hours to form an alumina layer in the open pores and surface layer of the container body, thereby obtaining the container for firing of the present invention.

In the firing container of the present invention thus obtained, p=
A phosphor +4 material consisting of a mixed powder of 1203/E r 203 was added and heat treated at a temperature of 1500° C., and the brightness of the obtained phosphor was examined (Example 1). For comparison, a phosphor 1) was prepared using the same phosphor material as in Example 1 and heat-treated under the same conditions using a SiC-only container (high-purity porous 5iC) on which no alumina surface layer was formed. (Comparative Example 1). The results are shown in Table 1 below. In addition, the brightness in this case is 10% based on the results obtained by firing under the same conditions in an alumina firing container.
It was set to 0.

Table 1 Example Example 1 Comparative Example 1 Brightness 100.8 98.2 From the above results, the phosphor obtained by firing in the firing container of the present invention has extremely excellent characteristics as a phosphor. I understand that.

〔Effect of the invention〕

The ceramic firing container of the present invention has a surface layer made of alumina formed on the surface of the porous ceramic base material, so it has excellent mechanical and thermal properties as well as excellent chemical stability at high temperatures. Therefore, it is extremely useful industrially as a container for firing ceramic materials such as phosphor abrasive materials, which require a balance of these characteristics.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the ceramic firing container of the present invention. ]...Porous ceramic base material, 2...Alumina surface layer. Applicant's agent Sato - Figure 1 of the rooster

Claims (2)

[Claims] 1. A container for firing ceramics, characterized in that a surface layer made of alumina is formed on the surface of a container body made of a porous ceramic base material. 2. The ceramic firing container according to claim 1, wherein the porous ceramic base material is made of SiC.