JPS6026067B2 - Transparent polycrystalline alumina composition and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a translucent polycrystalline alumina composition having excellent mechanical strength and electrical properties at high frequencies, and a method for producing the same.

In general, high-purity polycrystalline alumina has excellent mechanical and thermal strength, electrical properties at high frequencies, and excellent translucency, making it a useful material in many ways.

Conventionally, high-purity polycrystalline alumina is produced by adding a certain amount of magnesium oxide (Mg0) to fine alumina powder, molding it into the desired shape, and pre-calcining it in air at 1,000 to 1,300 degrees Celsius to fully burn the binder. After that, it is baked in a reducing atmosphere or in a vacuum from 1800 to 1950 pm, with a heat retention time of 1 to 1 feeding time. Although translucent polycrystalline alumina can be produced using this conventional method, it is extremely difficult to select firing conditions to obtain the desired quality. That is, it is difficult to sufficiently advance the coagulation without causing abnormal growth of crystal grains. However, in order to improve the translucency, it is necessary to allow sufficient particle growth, but at this time the mechanical strength of the aggregate decreases significantly, making it difficult to obtain the desired quality. The present invention was made in view of these points, and its gist is that aluminum oxide (mountain 203), 0.07 to 0.5% by weight of magnesium oxide (Mg0) and 0.01~0. The box consists of a translucent polycrystalline alumina composition consisting of % manganese dioxide (MN02) by weight.

In the present invention, Mn02 added at the same time as Mg0 is Mg
Similar to 0, it suppresses the abnormal growth of particles and provides excellent translucency while maintaining strong bending strength.

The reason for limiting the composition range in this invention is as follows.

That is, Mg0 is 0.07 or less, Mh02 is 0.01
In the following cases, the crystal grains grow abnormally and the bending strength becomes extremely weak, and when the crystal grains grow abnormally, they include pores and the transmittance decreases.
Further, if Mg0 is 0.5 or more and Mn02 is 0.3 or more, the transmittance decreases. The composition is preferably manufactured by the following method.

That is, the first amount is added to 10 parts by weight of alumina powder having a purity of 99.9% or more, an average particle diameter of 0.08 to 0.5r, and a specific surface area of 3 to 10 force/g. 0.07 to 0.5 parts by weight of magnesium oxide (Mg○) or a magnesium compound that becomes M due to temporary phosphorus are added as a substance, and manganese dioxide (Mn0) is added as a second component additive.
2) Or use a temporary gun to add a manganese compound that becomes Mn02 to 0.01 to 0. In addition to the phantom weight part, 0.7 to 1.5 tons/
This is a manufacturing method in which the product is molded under the same pressure as the ground, and after being cooled in air at 1,000 to 1,200 pm, it is fired in a vacuum (1 to 5 x 10-5 skin Hg) or in a hydrogen atmosphere at 1,780 to 185 pm. The reason why the firing atmosphere is a vacuum or a hydrogen atmosphere is because it serves to promote the removal of pores remaining during the sintering process.

Examples of the present invention will be described below.

Example Magnesium oxide and manganese dioxide with a purity of 99.5% or more and a powder average particle size of 0.5 μm are added to fine alumina powder with a purity of 99.99%, a powder average particle size of 0.3 μm, and a specific surface area of 5 mm/g. Add the same amount of pure water as the raw material and 8% by weight of vinyl acetate, and wet-mix for 40 hours using a resin ball with a diameter of 15 steel balls at 1.5 times the raw material. The powder is dehydrated and dried, passed through a 50-mesh thread, and then dry-pulverized for 2 hours using the same type and amount of resin balls, and then passed through a 50-mesh knot to form particles for molding.

Next, it is molded into a disk with a diameter of 30 sails and a thickness of 1.3 fences, and a cylinder with a diameter of 5.3 ribs and a thickness of 3 yards using a pressure of lton/lump.

Rinse this in the air at 50~7 ○/hr for 1100q.
After holding at o for 2 hours, let it cool naturally. This calcined product was heated in vacuum (1 to 5 x 10-5 Hg) at a rate of 100°C/hr, held at 1810°C for 2 hours, and then cooled at 250 qo/hr to obtain a measurement sample. The crystal grain size of this sample was measured using a metallurgical microscope using a disk, and the average value of 50 Green's diameters was measured, and the bending strength was measured based on the JIS standard using a cylinder. To measure the average value and transmittance of G. C. After polishing with #800, an infrared spectrophotometer was used at the highest value of diffuse transmittance in the wavelength range of 1.5 to 15 peaks. The results are shown in Table-1. Table 1-2 shows a conventional example. M. in Table 11. No. 1 to 15 are examples of the present invention. Reference examples 16 to 19 are outside the scope of the present invention. Table 1 Table 2 Table 2 shows a conventional example. In order to obtain excellent transmittance with this composition, it is necessary to increase the crystal particle size, but in this case, the bending strength It can be seen that it becomes extremely weak.

The present invention improves this point, and AI203-Mg○
By adding Mh02 to the system, it is possible to obtain an excellent transparency rate and to reduce the crystal grain size to obtain strong bending strength, and the composition of the present invention has a high alumina content, In addition, since the Akatsuki crystal is extremely dense, the dielectric loss at high frequencies, especially in the G household, is extremely small, making it useful as a dielectric material. The measurement results for three representative examples are shown in the right column of Table 1. Similar results can be obtained by using chloride or carbonate instead of oxide powder as the additive in the present invention. As described above, according to the present invention, transparent crystalline alumina having excellent mechanical and electrical properties can be obtained.

Claims (1)

[Claims] 1 Aluminum oxide (Al_2O_3), 0.07 to 0.5% by weight of magnesium oxide (MgO) and 0.01 to 0.3% by weight of manganese dioxide (MnO_2 ) A translucent polycrystalline alumina composition. 2 The purity is 99.9% or more, and the average particle size of the powder is 0.
．． Manganese dioxide or manganese dioxide formation by adding 0.07 to 0.5 parts by weight of magnesium oxide or a magnesium oxide forming compound to 100 parts by weight of alumina powder with a specific surface area of 08 to 0.5μ and a specific surface area of 3 to 10 m^2/g. Add 0.01 to 0.3 parts by weight of the compound and mold, and
A method for producing a translucent polycrystalline alumina composition, which comprises calcining at 0 to 1200°C and then firing at 1780 to 1850°C in vacuum or in a hydrogen atmosphere.