JPH0448749B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing alumina porcelain having a novel composition, and in particular to a method for manufacturing an improved alumina porcelain that can be used as a container for firing phosphors, etc., and has excellent translucency. Alumina porcelain is an excellent material that has high mechanical strength and corrosion resistance, and also has translucency, so it is used for various purposes. Alumina porcelain is also used in the field of phosphor manufacturing as a container (crucible) for firing raw materials. Incidentally, a phosphor is generally manufactured by mixing a base material, an activator material, and a flux, and firing the mixture. Here, the flux is generally about 20 to 20% of the total raw material.
80% by weight of alkali metal compounds and/or alkaline earth metal compounds are used. When an alumina porcelain crucible is used repeatedly in the production of such a phosphor, it almost always breaks after a few times. The cause of this is the alumina (α-
Al ₂ O ₃ ) reacts with the alkali metal and/or alkaline earth metal in the flux of the phosphor raw material to form β-Al ₂ O ₃
The alumina on the outer wall of the crucible changes to a different phase from the alumina on the outer wall of the crucible, resulting in a difference in the coefficient of thermal expansion.
Therefore, it is thought that this is because distortion occurs during repeated high-temperature firing and cooling. To prevent this, conventionally a trace amount of Al ₂ O ₃ is added to
MgO, TiO ₂ , CaO or La ₂ O ₃ , Y ₂ O ₃ , Er ₂
Rare earth element oxides such as O ₃ have been added singly or in combination, but even when using an alumina crucible containing such conventional additives, the above-mentioned alkali metal compounds and/or Alternatively, in the production of phosphors in which raw materials containing large amounts of alkaline earth metal compounds are fired, the number of repeated uses before breakage is still small. Therefore, the inventor of the present invention has developed a method that has sufficient mechanical strength and corrosion resistance even in high-temperature firing in contact with large amounts of alkali metal compounds and/or alkaline earth metal compounds, such as in the production of phosphors, and that can be used many times. As a result of various studies aimed at producing alumina porcelain that can withstand repeated use, it has been discovered that the objective can be achieved by mixing two specific types of additives in specific amounts in specific proportions. That is, the present invention provides MgO powder and MgO by firing.
Magnesium compound, _ZrO2 powder, which can be transformed into
Aluminum compounds, magnesium compounds, and zirconium compounds are selected from among zirconium compounds that can be changed to ZrO ₂ by firing, MgO・ZrO ₂ sintered powder, Al ₂ O ₃ powder, and aluminum compounds that can be changed to Al ₂ O ₃ by firing. Select, the weight ratio of magnesium compound and zirconium compound is MgO
and 2:8 to 7:3 in terms of ZrO ₂ and the total amount is 0.1 to 0.65% by weight based on Al ₂ O ₃ are weighed, mixed, and fired. This is a method for manufacturing alumina porcelain. The method for producing alumina porcelain of the present invention is carried out by mixing and dispersing MgO powder and ZrO ₂ powder with Al ₂ O ₃ powder, molding the mixture, and then firing it according to a conventional method. MgO powder and ZrO ₂ powder may be added to Al ₂ O ₃ powder as individual powders, or MgO powder and ZrO ₂ powder may be mixed in an appropriate ratio in advance, sintered, and then crushed. Agglomerated powder may be added to the Al ₂ O ₃ powder. _Al2O3 powder is generally used with an average particle size of 0.1~ _5μ , and MgO
The powder used has an average particle size of 0.5 to 2μ, the ZrO ₂ powder has an average particle size of 0.4 to 3μ, and the MgO.ZrO ₂ sintered powder has an average particle size of 0.5 to 3μ. still,
Instead of Al ₂ O ₃ , MgO and ZrO ₂ , those that can be converted into these by calcination, such as Al, Mg and
Sulfates, sulfides, chlorides, etc. of Zr can also be used. In the method for manufacturing alumina porcelain of the present invention,
Raw materials MgO powder, ZrO ₂ powder and MgO・
The average particle size of ZrO ₂ sintered powder is the average particle size of Al ₂ O ₃ .
It is preferable that it is 0.5 to 2 times, so that Al ₂
The uniformity of dispersion of additives in O ₃ is improved, which helps improve various properties such as sintered density. Further, it is preferable that the particle size distribution of these raw materials be as sharp as possible, since this will help improve the durability of the porcelain. Preferably, a new method called sol-gel method is used to produce raw materials with uniform particle size. The sol-gel method is a method in which, for example, a metal alkoxide is prepared, hydrolyzed and peptized to form a sol, and the sol is turned into a gel. Here, during gelation, a gel with a good particle size distribution can be obtained by dropping the sol into a nonaqueous solvent from an orifice and drying it. For example, to obtain an alumina gel, aluminum isopropoxide is hydrolyzed, hydrochloric acid is added to peptize the sol, and the sol is dropped into hexane through an orifice, stirred, and dried. The particle size of the resulting gel can be controlled by the stirring speed. Similarly, MgO and ZrO ₂ can also be obtained with the desired uniform particle size by the sol-gel method. The alumina porcelain obtained by the production method of the present invention as described above does not contain large crystal grains, has high density, has good corrosion resistance against alkali metal compounds and alkaline earth metal compounds, and is suitable for use in phosphor production. Even when used as a commercial crucible, it can withstand much more use than conventional crucibles. Another aspect of the invention comprises MgO and ZrO ₂ in a weight ratio of 2:8 to 7:3, the total amount of which is
_{Al2O3 , MgO} , which is 0.1-0.65% by weight relative to _Al2O3
and ZrO ₂ is fired in a hydrogen atmosphere. By performing firing in a hydrogen atmosphere in this manner, a translucent fired sintered body is obtained, which is not affected by alkali metal vapor and can therefore be used as an arc tube for an alkali metal vapor discharge lamp such as a sodium lamp. The present invention will be explained below with reference to Examples. Example 1 α-Al ₂ O ₃ of 99.8% purity with an average particle size of 0.3μ, and MgO, ZrO ₂ and MgO・with an average particle size of 0.5μ
The ZrO ₂ sintered bodies were mixed in varying amounts, thoroughly dispersed, dried with a spray dryer, and then molded with a rubber press (1500 Kg/cm ² ) to an inner diameter of 50 mm and a height of 50 mm.
A cylindrical shape was formed and sintered at 1650°C for 2 hours to produce an alumina porcelain crucible. In order to fire the phosphor in this crucible,
The phosphor matrix material: yttrium oxide (average particle size 3μ), the activator material: europium oxide, and the flux: sodium carbonate and potassium carbonate are mixed in the conventional composition ratio and charged. did.
This was baked at a temperature of 1100°C for 2 hours. This firing process was repeated until the crucible cracked. Table 1 shows the sintered density and number of repeated uses for each composition of the crucible.

【table】

[Table] Figure 1 shows the relationship between MgO/ZrO ₂ (weight ratio) and the number of repeated uses (times) when the amount of MgO + ZrO ₂ added to Al ₂ O ₃ is 0.3% by weight. In addition, the weight ratio of MgO/ZrO ₂ is 50/
The relationship between the amount of MgO+ZrO ₂ added to Al ₂ O ₃ (weight %) and the number of times of repeated use (times) in the case of 50% Al 2 O 3 is shown in FIG. As is clear from Figure 1, significant effects have been achieved.
MgO/ZrO ₂ (weight ratio) ranges from 2:8 to 7:3
It is. Furthermore, as is clear from Fig. 2, a remarkable effect is achieved when MgO + ZrO ₂ is used for Al ₂ O ₃ .
The amount added (wt%) is 0.1 to 0.65. Example 2 After adding water to commercially available aluminum isopropoxide and hydrolyzing it, 0.2 mol of hydrochloric acid was added to give 70
Peptization was carried out at ℃ for 7 days, and this was dropped into anhydrous hexane through an orifice with a diameter of 0.1 mm, and by stirring vigorously, transparent alumina with an average particle size of 0.3 μm was obtained. Sols were prepared from magnesium and zirconium isopropoxides in the same manner, and gelatinized. They were transparent bodies with average particle diameters of 0.3μ and 0.5μ, respectively. The above-mentioned magnesium oxide and zirconium oxide were added in an amount of 0.15% by weight to the above-mentioned alumina, and after drying, a molded body similar to that in Example 1 was obtained, and it was fired at 1300°C to obtain a transparent sintered body (crucible). . The sintered density at this time was 3.96. Using this crucible, a repeated phosphor firing test similar to that in Example 1 was carried out, and no change was observed even after 35 cycles.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between MgO/ZrO ₂ (weight ratio) and the number of repeated uses (times) in alumina porcelain obtained by the manufacturing method of the present invention.
FIG. 2 is a graph showing the relationship between the amount of MgO+ZrO ₂ added to Al ₂ O ₃ (% by weight) and the number of times of repeated use (times) in alumina porcelain obtained according to the manufacturing direction of the present invention.

Claims (1)

[Claims] 1 MgO powder, a magnesium compound that can be converted into MgO by firing, ZrO ₂ powder, ZrO ₂ by firing
Zirconium compound that can be converted into MgO・ZrO ₂
An aluminum compound, a magnesium compound, and a zirconium compound are selected from sintered body powder, Al ₂ O ₃ powder, and an aluminum compound that can be changed into Al ₂ O ₃ by firing, and the weight ratio of the magnesium compound and zirconium compound is MgO and ZrO. The ratio is ₂ :8 to 7:3 in terms of 2, and the total amount is Al ₂ O ₃
1. A method for producing alumina porcelain, which comprises weighing 0.1 to 0.65% by weight of alumina porcelain, mixing them, and firing them. 2. The method for producing alumina porcelain according to claim 1, wherein the firing is performed in a hydrogen atmosphere. 3. The method for manufacturing alumina porcelain according to claim 1, wherein the firing is performed in the atmosphere. 4 At least one of the above Al ₂ O ₃ , MgO and ZrO ₂
4. The method for producing alumina porcelain according to claim 1, 2 or 3, wherein the seeds are produced using a sol-gel method.