JPH01230492A - Apparatus for producing single crystal - Google Patents

Abstract

PURPOSE:To control the growing temperature, prevent contamination by convection and improve the quality of single crystals, by using 2 baffle plates in a hydrothermal crystallization apparatus for growing the crystal in a solvent at a prescribed temperature under a prescribed pressure. CONSTITUTION:A starting substance 4 for growing crystal is placed on the bottom of the pressure vessel 1 which is sealed with a cover 3, a seed crystal 6 is set in the upper part. Further the upper baffle plate 7 and the lower baffle plate 8 are arranged between the seed crystal 6 and the starting substance 4. Then, the starting substance 4 such as crushed natural crystal is dissolved in an appropriate solvent such as aqueous sodium hydroxide, heated at a prescribed temperature and pressurized at a prescribed pressure to send the starting material to the upper part of the vessel 1 by convection whereby a single crystal is allowed to grow on the seed crystal 6. The use of 2 baffle plates 7, 8 enables the temperatures in seed crystal zone and the starting substance zone to be controlled stably.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is widely used as a method for growing single crystals such as artificial quartz. The present invention relates to a method and apparatus for producing a single crystal using a hydrothermal synthesis method.

Currently, various single crystals such as quartz, corundum, heryl, berlinite, and calcite are synthesized by hydrothermal synthesis. These single crystals must be colorless and transparent, have no internal bubbles or cracks, and have no twin crystals.3. It is required to have no internal distortion and to have a certain size or more. Furthermore, when these single crystals are used at the optical level, higher quality is required.

The hydrothermal synthesis method has the possibility of synthesizing higher quality single crystals than other single crystal manufacturing methods such as the flux method and the Czochralski method.

However, there are problems with temperature control or convection control, making it difficult to obtain higher quality single crystals.

[Summary of the invention]

The present invention relates to an apparatus for producing various single crystals such as artificial quartz by hydrothermal synthesis, and a method for producing the same, which is equipped with two baffle plates.
The present invention relates to a method for producing a single crystal, using the above production apparatus, applying a predetermined temperature and pressure, and growing a crystal on a seed crystal in an appropriate solvent.

[Conventional technology]

Conventionally, attempts to synthesize single crystals have been made using various methods. That is, crystallization from a solvent, synthesis from a gel, crystallization from a fullernox or melt, hydrothermal synthesis, etc. Recently, attempts have also been made to use the FZ method under high pressure. However, in either method,
There have been problems such as the presence of impurities, inclusions, defects such as dislocations, and the presence of strain inside the crystal, which significantly impede the characteristics of the crystal.

Among the various methods mentioned above, the hydrothermal synthesis method uses natural single crystals grown in hydrothermal ore deposits and the growth atmosphere most often, and synthesizes those with characteristics closest to natural single crystals. There is a possibility that it can be done. Furthermore, it is possible to synthesize artificial single crystals with the best characteristics that do not exist in nature.

The hydrothermal synthesis method is a method of synthesizing materials at a predetermined temperature and pressure using an aqueous solution in an autoclave (pressure vessel), and is used for mass production of artificial quartz crystals. Generally, the aqueous solution used is an alkaline aqueous solution such as NaOH or a carbonate aqueous solution such as Na2Go, 2Co, or the like.

[Problem to be solved by the invention]

In growing single crystals using conventional hydrothermal synthesis equipment, although crystals can be grown, there are the following problems.

First, by providing a baffle plate, a temperature difference is created between the seed crystal growth area and the growth material melting area, and the temperature is kept constant in each area.
In reality, there will be a temperature difference between the part close to the baffle plate and the part far away.

For this reason, in the seed crystal growth region, the growth speeds of the seed crystals installed in the upper part (position far from the baffle plate) and the seed crystals installed in the lower part (position close to the baffle plate) are different. Furthermore, even with the same seed crystal, the growth rate is different between the upper and lower parts, resulting in a crystal with non-uniform thickness.

Furthermore, it is difficult to completely control convection with two baffle plates, and impurities and inclusions may be mixed in due to the influence of convection.

[Means to solve the problem]

Problems caused by conventional hydrothermal synthesis equipment, such as differences in the growth rate of single crystals, impurities, and inclusions in the crystal, are caused by controlling the temperature inside the autoclave and controlling convection. are doing.

In order to solve the above problem, a hydrothermal synthesis apparatus equipped with two baffle plates is provided.

[Effect]

In the hydrothermal synthesis method, starting materials are dissolved in an aqueous solution of an appropriate solvent at an appropriate temperature and pressure, and crystals are formed by slowly cooling or transporting nutrients using a temperature difference. Grow on a suitable substrate. Usually, raw materials placed in the lower part of the autoclave (sometimes raw materials are placed in the upper part) are dissolved in an aqueous solution and transported to the upper part of the autoclave by convection. At that time, since there is a temperature difference between the upper and lower parts, the seed crystal placed in the upper part or the raw material transported onto a suitable substrate precipitates and grows. In order to eliminate this temperature difference, a baffle plate is installed approximately in the center of the autoclave. The baffle plate has holes to control convection. Changing the size of this hole also changes the growth rate of the single crystal. this time,
A baffle plate was installed to enable more ideal temperature and convection control.

Hereinafter, a detailed explanation will be given according to examples.

〔Example〕

FIG. 1 shows a cross-sectional view schematically showing the configuration of this embodiment.

The pressure vessel main body 1 is pressure-sealed by a cover 3 via a seal ring 2. In the autoclave having the above configuration, the raw material for growth 4 is placed at the bottom of the pressure vessel main body 1. Next, a seed crystal 6 is placed on the growth raw material 4 via a seed crystal support frame 5 . The seed crystal needs to have particularly few internal inclusions and dislocations so as not to cause defects in the single crystal to be grown. The growing raw material 4 and the seed crystal 6 are arranged in this way, and the upper baffle plate 7 and the lower baffle plate 8 are also installed between them via the seed crystal support frame 5. FIG. 2 shows a perspective view of this baffle plate.

The upper baffle plate 7 and the lower baffle plate 8 can be rotated independently. In other words, the positions of the holes in the upper and lower baffle plates can be set to arbitrary positions. Further, the distance between the upper and lower baffle plates can also be set to any desired distance. The shapes and numbers of the openings 9 and 10 in the upper and lower baffle plates may be exactly the same on the upper and lower sides, or may be different. The aperture ratio of each baffle plate is about 5 to 25%.

In this example, artificial quartz crystal was grown. As the raw material for growth, we used natural crystal raw stone (lass power) crushed into appropriate sizes. Further, as the seed crystal 6, a Z plate of natural or artificial optical grade quartz was used. An aqueous NaOH solution was used as the solvent.

1st Example Temperature of seed crystal 6: 340°C Temperature of growing raw material 4: 370°C Solvent: 0.5 mol NaOH aqueous solution Pressure: 1000 kg/cJ Growth period: 10 days Structure of the baffle plates: The upper and lower baffle plates had the same shape, the aperture ratio was 10%, the openings were the same on the top and bottom, and the distance between the top and bottom was 15 m.

As a result, crystal was grown on the seed crystal 6.

Thickness of grown layer: 5.2 mm Growth rate: 520 μm/day Properties of grown layer: α-quartz (identified by X-ray diffraction method). Compared to traditional artificial quartz, inclusions,
Highly perfect crystals with very few inclusions and defects such as microcracks were obtained.

Moreover, no difference was observed in the thickness of the growth layer at the top and bottom of the grown seed crystal.

Second Example Temperature of seed crystal 6: 330°C Temperature of growing raw material 4: 360°C Solvent: 0.5 mol NaOH aqueous solution pressure: 1000 kg/ct Growth period: 10 days Baffle plate configuration: The upper and lower baffle plates have the same shape, but the openings do not match on the top and bottom. FIG. 3 is a view of this baffle plate viewed from above.

The opening in the upper baffle plate and the opening in the lower baffle plate are
As shown in Figure 3, it was installed with a 15 degree offset in the rotational direction. The aperture ratio was 10%, and the distance between the top and bottom was 15 mm.

As a result, crystal was grown on the seed crystal 6 as shown below.

Thickness of the grown layer: 4.7 fl Growth rate: 470 μm/day Properties of the grown layer: α-quartz (identified by X-ray diffraction). Compared to traditional artificial quartz, Inclugidine,
Highly perfect crystals with very few inclusions and defects such as microcracks were obtained.

Further, as in Example a, no difference was observed in the thickness of the growth layer at the top and bottom of the grown seed crystal.

〔Effect of the invention〕

As detailed above, according to the present invention, it is possible to more stably control the respective temperatures of the seed crystal part and the growing raw material part compared to the conventional single crystal growth method using a hydrothermal synthesis apparatus. Furthermore, contamination of impurities and inclusions due to convection can be prevented. Therefore, the hydrothermal synthesis apparatus according to the present invention enables higher quality single crystal growth, and its effects are extremely large.

Note: The baffle plates are a single-crystal manufacturing device that can rotate independently.

Baffle plates are a single crystal manufacturing device that can be fixed at any distance.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of a single crystal manufacturing apparatus according to the present invention. FIG. 2 is a perspective view of the baffle plate. FIG. 3 is a plan view of the baffle plate in the second embodiment. 1... Pressure vessel body 2... Seal ring 3... Cover 4... Raw material for growth 5... Seed crystal support frame 6... Seed crystal 7... Upper baffle plate 8... Lower baffle plate 9... Upper baffle plate opening 10... Lower baffle plate opening and above Applicant: Seiko Electronics Industries, Ltd.

Claims (1)

[Claims] 1. A single-crystal manufacturing apparatus, which is a hydrothermal synthesis apparatus for growing crystals in a suitable solvent by applying a predetermined temperature and pressure, and is equipped with two baffle plates.