JPH0227314B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing an emerald single crystal.

[Conventional technology]

Emerald is a curbstone (beryl, 3BeO・
It is made by replacing some of _the Al ₂ O ₃ of Al ₂ O 3 6SiO ₂ ) with Or ₂ O ₃ , and has been prized as a gemstone since ancient times.

Emeralds have been synthesized for a long time, and the main methods for producing them include hydrothermal synthesis and solvent methods (hereinafter referred to as flux methods). The former method is disclosed in Japanese Patent Publication No. 42-3484, Japanese Patent Publication No. 46-25499, etc., but it is hardly used industrially because the growth rate is slow and the equipment is large-scale and expensive. On the other hand, the latter has a relatively fast growth rate and inexpensive equipment, so
46-25500, Special Publication Showa 47-27639, Special Publication Showa 48-23278,
Special Publication No. 52-39396, Special Publication No. 54-12120, No. 12120 No. 58-
115093, Unexamined Japanese Patent Publication No. 58-115095, Unexamined Japanese Patent Publication No. 58-199798,
Or, as shown in the Journal of the Chemical Society of Japan (see references), it has been researched or industrialized by many people.

[Problem to be solved by the invention]

However, although all of these patent documents mention the flux composition, raw material composition, slow cooling temperature program, etc., there is no description of the industrially rational crystal orientation of the seed crystal and the pretreatment of the seed crystal. I can't.

An object of the present invention is to further improve the conventional method for synthesizing emerald single crystals using the flux method, and to provide a method for producing emerald single crystals of better quality.

[Means to solve the problem]

The method for producing an emerald single crystal of the present invention uses one or more selected from vanadium pentoxide, lithium molybdate, molybdenum trioxide, sodium molybdate, lithium oxide, etc. as a solvent; In a method for producing an emerald single crystal, in which beryllium oxide, aluminum oxide, silicon dioxide as emerald components, and chromium oxide as a coloring agent are dissolved and an emerald single crystal is precipitated by a temperature difference method or a slow cooling method, the (1010) face of the emerald single crystal is It is characterized in that a seed crystal with the widest parallel planes is etched in advance with hydrofluoric acid.

When an emerald single crystal is synthesized by the flux method, the main planes that are generated are the (0001) plane called the c-plane, the (1120) plane called the a-plane, and the (1010) plane called the m-plane. When one or more types selected from vanadium pentoxide, lithium molybdate, molybdenum trioxide, sodium molybdate, lithium oxide, etc. are used as a flux, the growth rate of the c-plane is generally the fastest. , a seed crystal with this plane as the widest parallel plane is often used.

However, through repeated experiments, the present inventors found that using a seed crystal with the m-plane as the widest parallel plane and etching it with hydrofluoric acid in advance resulted in the highest yield, including quality. I found out.

That is, when the c-plane is used as a seed crystal, the growth rate is faster than that of the a-plane and m-plane under the same conditions (flux composition, temperature, etc.), but so-called flux inclusions tend to occur and the quality tends to deteriorate. Therefore, in order to grow crystals of good quality, the growth rate must be reduced. The final yield is expressed as growth rate x quality yield, but if the growth rate is decreased, the yield also decreases, and this cannot be said to be a rational manufacturing method. On the other hand, when we checked the crystal quality by using the m-plane as a seed crystal and setting conditions so that the growth rate was the same as that of the c-plane, we found that the crystal layer grown on the m-plane contained flux inclusions seen on the c-plane. It was found that the yield was improved.

When cutting natural emerald, beryl, or synthetic emerald to obtain a parallel seed crystal with the widest m-plane, it is desirable that the planes deviate within 10° from the crystal orientation. This is because the m-plane is the naturally occurring plane of emerald, so if the plane of the seed crystal deviates significantly from the m-plane, the crystal will grow to make the m-plane the outermost surface, resulting in abnormal growth near the seed crystal. This is because defects such as flux inclusions are more likely to occur. That is, the shape of the seed crystal is preferably a rectangular plate with one side in the a direction and the other side in the c direction, when the widest parallel plane is the m-plane.

However, since emerald crystals are relatively brittle, they tend to chip when cut as seed crystals, making it difficult to form perfect rectangular plates. Therefore, as a practical means, after introducing the seed crystal, the a-plane, m
Defects such as flux inclusions near the seed crystal can be prevented by slowing down the growth rate until natural planes such as planes and c-planes appear.

As a way to slow down this growth rate, Slow down the rate of dissolution of raw materials.

Reduce temperature difference.

Slow down the slow cooling rate.

Although this can achieve some objectives, it also depends to a large extent on the surface of the seed crystal.

Therefore, since a cut seed crystal should be smooth to eliminate the interface with the growth layer, better results will be produced, so it is preferable to wrap and polish both sides. In particular, pre-etching with a 5% or less hydrofluoric acid aqueous solution is advantageous because it can be easily used industrially, especially in order to remove the process-affected layer on the surface and bring out the natural surface at an early stage.

Furthermore, when seed crystals are introduced into flux, it is necessary to sufficiently preheat them and to minimize thermal shock at the time of injection. Furthermore, when removing the emerald after crystal growth, it must be slowly cooled to room temperature after being removed from the flux. These operations are essential means to prevent cracking of emeralds due to thermal shock.

The present invention will be described in detail below based on examples.

Example 1 100 g of natural beryl and 2 g of sintered Cr ₂ O ₃ were placed in a platinum crucible with an inner diameter of 100 mmφ and a height of 200 mm, and a hole of 3 mmφ was drilled at a distance of 50 mm from the bottom, with an open area ratio of 5%. Place a full board. Into this, 100% of BeO, Al ₂ O ₃ , SiO ₂ and Cr ₂ O ₃ were added in advance in a separate furnace.
After saturated melting in a mixed melt of 3.2Kg of V ₂ O ₅ and 0.16Kg of Li ₂ O at ℃, the cooled flux is pulverized and put into the melt, and then covered with a platinum lid. However _{, Cr2O3}
The amount of Al ₂ O ₃ was 3%. This has an inner diameter of 130mmφ
Place it in a vertical tube furnace and heat it, then heat the bottom of the
The temperature is maintained at 1005°C, and the temperature around 4 to 5 cm from the surface of the flux is maintained at 995°C for about one week. As seed crystals, six emerald sheets, which had been etched in advance with a hydrofluoric acid aqueous solution and had dimensions of 30 mm in the a direction, 20 mm in the c direction, and 1 mm in the m direction, were supported and fixed with a platinum wire. Place the seed crystal into the flux so that the center of the seed crystal is approximately 50 mm below the flux liquid level and the m-plane is perpendicular to the flux liquid level.

At this time, the seed crystal is introduced into the furnace from above while being gradually preheated. After 90 days of growth, an emerald single crystal with a thickness of approximately 2.7 mm was grown on one side of the m-plane of the seed crystal. Rough emeralds grown in this way have very few defects such as inclusions. When this m-plane was used as the seed crystal growth surface and the crystal was cut for use in jewelry, the yield was about 30%.

Example 2 Al ₂ O ₃ , BeO, SiO ₂ and Cr ₂ O ₃ were added in advance.
After saturated dissolving in a flux having the same composition as in Example 1 at 1050°C, the flux was cooled and ground, and the flux was placed in a platinum crucible with an inner diameter of 100 mmφ and a height of 200 mm, covered with a platinum lid, and heated at 1050°C for one week. Heat.
However, Cr ₂ O ₃ was set at 2% of the amount of dissolved Al ₂ O ₃ .
The same seed crystal as in Example 1 was put into this flux in the same manner as in Example 1, and after holding for 24 hours, it was gradually cooled from 1050°C to 800°C at a rate of 5°C/day.

When the crystal was taken out after 50 days of slow cooling growth, an emerald single crystal with a thickness of approximately 1.5 mm had grown on one side on the m-plane of the seed crystal. The emerald rough grown in this way has very few defects such as inclusions, and when cut into gemstones while avoiding inclusions, the highest quality was obtained at a yield of 25%.

Example 3 Components of flux Li ₂ O 5% MoO ₃ 70% V ₂ O ₅ 25% Temperature at growth zone 850°C Temperature under buffer 860°C After seed crystals were introduced in the same manner as in Example 1, After growing for 90 days, an emerald single crystal with a thickness of approximately 1.9 mm grew on one side on the m-plane of the seed crystal. Emerald rough grown in this way has very few defects such as inclusions, and
The color tone was a slightly brighter green than that of Example 1. The cut yield was about 28%.

Example 4 Using the flux of Example 3, slow cooling was carried out from 950°C to 650°C at a rate of 5°C/day in the same manner as in Example 2.

When the crystal was taken out after 60 days of slow cooling growth, an emerald single crystal with a thickness of approximately 1.8 mm had grown on one side on the m-plane of the seed crystal. The emerald rough grown in this way has very few defects such as inclusions, and when cut into gemstones while avoiding inclusions, the highest quality was obtained at a yield of 20%.

〔Effect of the invention〕

As described above, according to the present invention, (1010)
By using a seed crystal that has been etched with hydrofluoric acid in advance and with the widest parallel plane, it is possible to obtain a beryl single crystal that is not prone to cracking, has significantly fewer defects such as inclusions, and has a high yield. can.

Also, since the direction of inclusions is mostly in the <0001> direction, when cutting the so-called m-plane into a table, the inclusions are in the thickness direction, so
Inclusions are difficult to see and the grade after cutting can be increased. That is, the wider the m-plane, the higher the yield and quality.

As described above, the present invention is extremely useful in practice for synthesizing emerald single crystals.

Reference Journal of the Chemical Society of Japan 1972 P1648 1973 P 506 1973 P 941 1974 P1468 1975 P1730 1976 P 752 1976 P 748 1977 P 194 1979 P1489 K.NASSAU “Gems Made by Man P127
~P158

Claims (1)

[Claims] 1 Vanadium pentoxide, lithium molybdate,
One or more selected from molybdenum trioxide, sodium molybdate, lithium oxide, etc. are used as a solvent, and in this solvent, beryllium oxide, aluminum oxide, silicon dioxide, which becomes an emerald component, and chromium oxide as a coloring agent are used. In a method for producing an emerald single crystal in which the emerald single crystal is precipitated by melting and using a temperature difference method or slow cooling method, a seed crystal with the (1010) plane of the emerald single crystal as the widest parallel plane is etched in advance with hydrofluoric acid. A method for producing an emerald single crystal characterized by using the method.