JPH0319199B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for synthesizing beryl single crystals using flux, and more particularly to a method for efficiently and economically synthesizing high-quality beryl single crystals by a flux method.

In recent years, there has been a great deal of interest in techniques for producing large synthetic single crystals. Synthetic single crystals have been successfully used in laser and maser fields. In addition to these industrial fields, synthetic gemstones are also used in the decorative field.

Although there are several types of known methods for synthesizing single crystals (e.g. Vuernoulli method and pulling method), these methods have fatal drawbacks for synthesizing large single crystals of beryl and similar stones. have. Although the above two methods are often used to synthesize simple structures (colladam spinel, etc.), they also have the drawback of large crystal strain. Furthermore, the synthesis of beryl single crystals using the above two methods has not been successful so far. A third method of synthesizing single crystals is hydrothermal synthesis. Hydrothermal synthesis requires high-temperature, high-pressure vessels and is therefore too costly. Furthermore, when beryl single crystals are synthesized using this method, doping of chromium oxide in the beryl composition is not successful, making it difficult to obtain single crystals that can be used as synthetic gemstones.

A flux method is also known in which crystal components are dissolved in a flux of oxides, fluorides, metal salts, etc., and a single crystal is synthesized by utilizing the difference in solubility depending on temperature.

In the synthesis of beryl single crystals using the conventional flux method, the base material for single crystal growth is selected from among natural beryl, aluminum oxide, beryllium oxide, quartz, chromium oxide, titanium oxide, etc., so that it has an almost beryl composition. They used mixed raw materials. This case has the following drawbacks.

(1) When natural beryl is used as a base material, it is desirable to obtain beryl single crystals of the desired color due to impurities contained in natural beryl.

(2) When natural beryl is used as a matrix, Al ₂ , O ₃ , and BeO in the beryl composition are preferentially dissolved, and the beryl compositions (Al ₂ O ₃ , BeO) in the flux are dissolved preferentially.
It is difficult to control the amount of dissolved components (SiO ₂ , BeO, Cr ₂ O ₃ , Fe ₂ O _{3 ,} etc.) and their respective composition ratios.

(3) When natural beryl is used as a base material, the dissolution of SiO ₂ is slow, so residues of SiO ₂ remain, which becomes a source of naturally nucleated beryl, precipitates a large amount of microcrystals, and does not meet the intended purpose. This reduces the quality of large beryl single crystals, such as inclusion in large beryl single crystals.

(4) When beryl composition components (aluminum oxide, beryllium oxide, quartz as silicon oxide (here, quartz refers to fused quartz, porous quartz glass, etc.) are mixed and used as a base material, Since the dissolution speed of quartz is slow, the growth speed of beryl single crystals is also very slow, making the cost very high.

(5) In (4), if quartz powder is used in order to increase the dissolution speed of quartz, this quartz powder becomes the generation nucleus of naturally nucleated beryl, resulting in the same result as in (3).

(6) In (4), in order to increase the growth speed of beryl single crystals, if the temperature difference between the temperature of the single crystal precipitation/growth section and the temperature of the raw material melting section is widened, a large amount of naturally nucleated beryl will be generated. , not only does it give the same result as (3), but also a large amount of inclusions occur in the single crystal.

(7) When quartz is used as a base material, zAl ₂ O ₃・xSiO ₂・
yBeO (x: 1-6, y: 1-3, z: 0-1)
An intermediate layer with _a composition of

In order to solve the above problems, a method that can stably dissolve silicon oxide in flux has been awaited.

The present invention eliminates such drawbacks and allows large beryl single crystals with few defects to be grown at a constant growth speed by using synthetic quartz to control the amount of silicon oxide dissolved in the flux.

As a base agent, aluminum oxide, beryllium oxide, and synthetic quartz are mixed to have an approximately beryl composition, and as a coloring agent, chromium oxide, titanium oxide, or iron oxide is mixed with 0 to 0.
A mixture of 5wt% is sintered and used. Preferably, two types of base materials are used: a sintered body in which aluminum oxide and beryllium oxide are blended in a molar ratio of 1:3, and a coloring agent is mixed in an amount of 0 to 3 wt%, and a synthetic quartz crystal.

In the present invention, high-quality beryl single crystals can be grown efficiently because, unlike quartz, quartz easily dissolves in flux and does not form intermediate compounds on the surface of the quartz, so the concentration of silicon oxide in the flux can be easily reduced. This is because it can be controlled.

The present invention will be explained in detail below based on Examples.

Example 1 When using sintered Al ₂ O ₃ , BeO, and SiO ₂ (quartz) (molar ratio 1:3:6) as the base material, and sintered SiO ₂ (quartz) as the base material ( _{Cr2O3 _}
(1wt% mixed) The mother compound should be added every week depending on the amount of growth.

First, 15g of base material was poured into a platinum crucible (φ70mm x 110mm).
800 g of V ₂ O ₅ was added as a flux and heated. Temperature of growth part: 970℃, temperature of base agent: 980℃
Two furnaces were prepared, and 1 to 15 g of mother compound was added every two weeks (the amount added increases as the growing period gets longer), and the plants were grown for 140 days. A beryl single-crystal plate was placed as a seed in the growth section, suspended from a platinum wire. (Fig. 1) When the growth speed is shown in a graph, it becomes as shown in Fig. 2, and it can be seen that the growth speed is faster when crystal is used as the base material.
In addition, the obtained single crystal was subjected to X-ray rocking curve,
When examined under a microscope, the crystals using quartz showed inclusions in the early stages of growth and inclusions of microcrystals throughout, and the crystals were not very good. High quality crystals were obtained, with no inclusions or microcrystals present.

Example 2 A beryl single crystal was grown under the same conditions as in Example 1, except that the temperature in the growth part was 970°C and the temperature in the base material part was 990°C.

When the growth speed is shown in a graph as shown in Figure 3, it can be seen that the growth speed is faster when crystal is used as the base material. In addition, when the obtained single crystal was examined using an X-ray rocking curve and a microscope, inclusions and inclusions of microcrystals were observed throughout the crystal, and twin crystals were observed in the crystal. It was of extremely poor quality. For those using crystal, inclusions are seen in the early stages of growth, and although there are a few,
Microcrystal inclusions were also present.

Example 3 Al ₂ O ₃ and BeO (molar ratio 1:3) were used as base agents.
A sintered body mixed with 0.5 wt% of Cr ₂ O ₃ and quartz were used, and in the other one, the sintered body and quartz were used as a base material.

First, 80 g of sintered body and 10 g of SiO ₂ were placed in a platinum crucible (φ70 mm x 110 mm) and used as a flux.
800 g of Li ₂ O/M ₀ O ₃ /V ₂ O ₅ (weight ratio 1:1:1) was added and heated. Two flux furnaces were set so that the temperature of the growth section was 930°C and the temperature of the base material section (sintered compact charging section) was 940°C. Quartz was added to one unit, and crystal was added to the other unit every 10 days, and the plants were grown for 140 days.
A beryl single crystal was placed as a seed in the growth section, suspended from a platinum wire. (Fig. 4) When the growth speed is shown in a graph, it becomes as shown in Fig. 5, and it can be seen that the growth speed is faster when crystal is used as the base material. Further, when the obtained single crystal was examined using an X-ray rocking curve and a microscope, it was found that the crystal containing microcrystals was found throughout the crystal using quartz. Slight inclusions were also observed. When crystal was used, no inclusions or microcrystalline inclusions were observed, and the single crystal was of very high quality.

Example 4 Temperature of growth section: 930°C, base material section (sintered body input section)
A beryl single crystal was grown at a temperature of 950°C and other conditions the same as in Example 3.

When the growth speed is shown in a graph as shown in Figure 6, it can be seen that the growth speed is faster when crystal is used as the base material. In addition, the obtained single crystal was
When the line rocking curve was examined using a microscope, large inclusions were seen in several places in the case of the one using quartz, and there were many inclusions of microcrystals. In the case of using crystal, only a few inclusions were observed in the early stage of growth, and the crystal was overall of high quality.

As mentioned above, the method for synthesizing beryl single crystals of the present invention involves the use of beryllium oxide, which has a composition ratio approximately that of beryl,
A base substance consisting of aluminum oxide, silicon dioxide, and chromium oxide as a coloring agent is mixed with vanadium pentoxide, sodium molybdate, molybdenum trioxide, lithium oxide, sodium oxide, etc. as the above-mentioned melting agent (flux). In a synthesis method in which beryl single crystals are precipitated on seed crystals by adding one or more selected from the above and heating above the melting temperature of the above-mentioned flux to form a molten salt, the above-mentioned base material dioxide is added. By using synthetic quartz as silicon, we can obtain high-quality single crystals with no inclusions or inclusions of microcrystals, while at the same time making it possible to synthesize beryl single crystals with significantly improved crystal growth rates. This is what I did. Since the present invention can easily improve quality and yield, it can be used not only for functional crystals such as masers, but also for jewelry, so it is an extremely useful invention in practice.

[Brief explanation of the drawing]

1 and 4 are schematic cross-sectional views of a crucible in the flux method. In FIGS. 1 and 4, 1 is a platinum crucible, 2 is a base material, 3 is a flux, 4 is a seed, and 5 is a platinum plate. In FIG. 4, 2-a is a sintered body, and 2-b is quartz or crystal. Figures 2, 3, 5, and 6 show the relationship between the number of days for growth and the speed of growth based on the present invention. A...Growing speed curve when using quartz as the base material, B...Growing speed curve when using quartz as the base material.

Claims (1)

[Claims] 1 Beryllium oxide, which has a composition ratio almost that of beryl,
Vanadium pentoxide as a melting agent (flux),
One or more selected from sodium molybdate, molybdenum trioxide, lithium oxide, sodium oxide, etc. are added and heated to a temperature higher than the melting temperature of the above flux to form a molten salt. 1. A method for synthesizing a beryl single crystal, characterized in that a synthetic quartz crystal is used as silicon dioxide as the base substance.