JPS6149280B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is the first to complete the production of a chrysoberyl single crystal exhibiting the cat's eye effect.

An object of the present invention is to provide an artificially produced chrysoberyl single crystal exhibiting a perfect cat's eye effect.

Another object of the present invention is to provide a large, inclusion-free chrysoberyl single crystal that exhibits a high quality cat's eye effect without cuts, distortions, etc.

When a certain kind of chrysoberyl single crystal is cut into a cabochon shape, white rays appear on the peaks of the crystal, resembling cat's eyes, and when the crystal is moved, the rays also move. This is commonly referred to as the cat's eye effect, glow effect or shadowy effect.

Attempts have been made to produce it artificially since ancient times, but no success has been achieved.

The present inventor melted titanium oxide in a chrysoberyl composition using a halogen lamp or xenon arc lamp, which is a very stable heat source, crystallized it, dissolved titanium oxide at a high concentration in chrysoberyl, and then heat-treated it to finely dissolve the titanium oxide. The cat's eye effect was completed by precipitating the crystals within a single crystal.

FIG. 1 shows an outline of the method of the present invention.

The spheroidal mirror body 1 has two focal points.

A halogen lamp 2 or a xenon arc lamp is placed at one focal point, and a rod-shaped sintered raw material 3 is placed at the other focal point. The rod-shaped raw material 3 is held by an upper rotating shaft 4. Further, the seed crystal 5 is set on the lower rotating shaft 6. The rod-shaped raw material 3, the seed crystal 5, and the upper and lower rotating shafts 4 and 6 are enclosed in a transparent quartz tube 7, so that the atmosphere can be controlled freely, and it is also possible to apply vacuum or pressure. The temperature rises in the rod-shaped raw material 3 and a molten zone 8 is formed only in the portion that completely coincides with the focal point. The melting zone 8 is relatively moved by moving the rotating shafts 4 and 6 upward or downward. The operation is performed by first concentrating infrared rays on the tip of the raw material rod 3 to form a molten zone 8, and then moving the seed crystal 5 upward to bring the molten zone 8 into contact with it. After confirming that an equilibrium state has been reached, the rotating shafts 4 and 6 are moved, and a transparent single crystal is obtained with the seed crystal 5 growing. That is, melting of the raw material occurs at the interface between the melting zone 8 and the raw material rod 3, and crystallization occurs at the interface between the melting zone 8 and the seed crystal 5.

This method allows crystal growth of a wide variety of substances. The biggest features are that there is no need to use a crucible and that the infrared light source is extremely stable. That is, the melt is very stable. For this reason, it has become possible to grow solid solution type single crystals with arbitrary composition ratios, which was impossible using normal crystal growth methods. Another advantage is that high temperatures can be easily obtained. 1900℃ or higher with a halogen lamp,
High temperatures up to 2800℃ can be obtained with a xenon arc lamp.

In the present invention, a chrysoberyl single crystal in which titanium oxide is solid-dissolved at a high concentration ratio is obtained by the method described above.

The amount of titanium oxide in the single crystal is preferably 0.1% by weight or more, and it was possible to contain it up to 1.0% by weight. The most effective amount was around 0.5 weight percent. If the amount of titanium oxide is less than 0.1% by weight, the cat's-eye effect will hardly be observed, and if it exceeds 1.0% by weight, crystallinity will be inhibited. It also contains chromium oxide, iron oxide, vanadium oxide, nickel oxide, cobalt oxide, etc. for coloring, and these added solid solutions, including titanium oxide, are uniformly dissolved in the single crystal.

The rod-shaped high-density sintered body is designed to reduce the density of the chrysoberyl single crystal in order to prevent the generation of bubbles and stabilize the molten zone.
It has a density of over 95%, and its outer diameter is almost uniform except at both ends.

If the density does not reach 95%, air bubbles will occur in the melted zone and will be incorporated into the crystal, inhibiting crystallinity. Moreover, if the outer diameter dimension is non-uniform, the molten zone becomes unstable and the crystallinity deteriorates. In order to obtain such a high density, starting materials used were ammonium, aluminum, or calcined aluminum hydroxide for aluminum oxide, and calcined beryllium sulfate or beryllium hydroxide for beryllium oxide. In order to completely form a solid solution of titanium oxide, 0.1 to 8 weight percent of titanium oxide was added as a powder having a particle size of 0.1 micron or less, which was obtained by reacting titanium tetrachloride with oxygen in the gas phase.

When the titanium oxide content is less than 0.1% by weight, almost no cateye effect occurs, and when it exceeds 8% by weight, crystal growth is inhibited and good quality crystals cannot be obtained. Chromium oxide, which is further colored
One or more of iron oxide, vanadium oxide, nickel oxide, cobalt oxide, and manganese oxide.
0.1 to 5 weight percent was added, mixed, rubber press molded, and sintered at 1300°C to 1700°C. When the amount of the colorant is less than 0.1% by weight, there is almost no coloring effect, and crystal growth is inhibited because the infrared absorption ability is poor. On the other hand, if the colorant exceeds 8% by weight, the colorant itself segregates and becomes inclusions, deteriorating crystallinity. If the sintering temperature does not reach 1300°C, sintering is insufficient, crystal growth is inhibited, and good crystals cannot be obtained.

If the temperature exceeds 1700°C, the sintered rod will become bent and its outer diameter will become uneven, making crystal growth difficult.

Great care was taken during rubber press molding to eliminate non-uniformity in the outer diameter and to ensure that the colorant was uniformly dissolved in the crystal. Infrared rays were focused on the rod-shaped high-density sintered raw material thus obtained to form a molten zone. In the method of the present invention, the high temperature melting zone and the grown crystal were very close to each other, so it was very easy to dissolve titanium oxide into the crystal. In particular, by increasing the maximum temperature of the melting zone by at least 50°C higher than the melting point of chrysoberyl, 1870°C, the solid solution effect was further improved and the occurrence of inclusions etc. could be prevented. That is, if the maximum temperature of the melting zone does not reach 1920°C, titanium oxide and coloring agent will not be uniformly dissolved in solid solution and will become unnecessary inclusions. In addition, since heating is carried out from the outer periphery of the melting zone, the temperature at the center may become low and the amount of titanium oxide in the crystal may become uneven. By changing the angle by 0.5% to 10%, it was possible to obtain a seamless cat's eye effect.

If the fluctuation period of the infrared output does not reach 20 seconds or the width of the fluctuation output does not reach 0.5%, there is almost no effect of the output fluctuation; if the fluctuation period exceeds 60 seconds or the width of the fluctuation output does not reach 10%. If the amount exceeds 1%, the molten zone becomes unstable and crystal growth is inhibited.

The orientation of crystal growth is very important. If the growth axis is aligned in a direction other than the C-axis, a plane perpendicular to the C-axis will be generated as shown in FIG. 2a, resulting in a flat crystal.

When this is grown in the C-axis direction, a cylindrical crystal is obtained as shown in FIG. 2b.

The single crystal thus obtained is further heat treated at 1000°C to 1550°C for 10 hours or more.

This is continued until microcrystals precipitate inside and a cat's eye effect occurs. This process may also be carried out after the subsequent cabochon cutting.

If the temperature does not reach 1000°C or 10 hours, the cat's eye effect will not be observed, and if it exceeds 1,550°C, the crystallinity will be impaired and the cat's eye effect will become unclear. To ensure even higher quality
A columnar single crystal or a cabochon-cut single crystal is buried in a mixed powder containing 1 to 20 weight percent of BeAl ₂ O ₄ powder and titanium oxide powder, and a coloring agent, and then heated at 1300°C to 1700°C for 10 hours. Heat treatment is performed. This heat treatment is performed alone or in combination with the previous heat treatment. If titanium oxide does not reach 1% by weight or the temperature condition is 1300℃
Alternatively, if the time is less than 10 hours, the expected quality of the cat's eye effect will not appear, and if it exceeds 1700°C, the crystallinity will be impaired or the cat's eye effect will become unclear.

A cabochon cut is cut so that its bottom surface is parallel to the C-axis. The situation is shown in Figure 3.

As detailed above, according to the present invention, a chrysoberyl single crystal exhibiting a cat's eye effect was obtained for the first time, and a method for easily obtaining such a high-quality large-sized single crystal was also clarified.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the outline of the present invention. FIG. 2 is a diagram illustrating a single crystal. FIG. 3 is a diagram illustrating a cabochon cut. 1...Spheroidal mirror body, 2...Halogen lamp, 3...Rod-shaped raw material, 4...Upper rotating shaft, 5...
Seed crystal, 6... Lower rotating shaft, 7... Quartz tube, 8
...melting zone.

Claims (1)

[Claims] 1 a spheroidal body, a thermal light source placed at one focal point of the spheroidal body, a raw material rod placed at the other focal point, an upper rotating shaft and a lower rotating shaft that pivotally support the raw material rod, and the upper rotating shaft. In the green waorsterite single crystal production method using an infrared concentrated heating furnace equipped with a transparent quartz tube that encloses the rotating shaft and the lower rotating shaft, aluminum oxide, beryllium oxide, and particles with a particle size of 0.1 micron or less are used as starting materials. Using 0.1 to 8 weight percent of powdered titanium oxide and 0.1 to 5 weight percent of one or more of chromium oxide, iron oxide, vanadium oxide, nickel oxide, cobalt oxide, and manganese oxide as a coloring agent, After press-molding the raw material into a rod shape, it is heated to 1300℃
Sintering at 1700°C to form the raw material rod, holding the raw material rod on the upper rotating shaft, and setting a seed crystal with the C axis positioned parallel to the rotating axis on the lower rotating shaft,
Thereafter, the tip of the raw material rod is melted, the melted part is brought into contact with the seed crystal, and the upper rotation axis and the lower rotation axis are mutually moved downward to grow a single crystal on the seed crystal, and the single crystal is grown on the seed crystal. Crystals from 1000℃ to
A method for producing chrysoberyl single crystals exhibiting a cat's-eye effect, which is heat-treated at 1550°C for 10 hours or more, and then cut into cabochons with the bottom surface parallel to the c-axis.