JPH0313200B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a method for synthesizing chrysoberyl single crystals (orthorhombic system) using a solvent (flux), and more specifically, a method for efficiently and economically producing chrysoberyl single crystals of better quality than molten salt. It is related to a method of synthetic synthesis.

[Prior Art] Conventionally, hydrothermal methods and molten salt methods using a solvent have been known as methods for synthesizing chrysoberyl, but the present invention is directed to improving these molten salt methods. The molten salt method uses less energy (heat, pressure) and growth time than the hydrothermal method, and has the advantage of being economical because the equipment and parts used can be greatly simplified. That is, in the molten salt method, panadium pentoxide as a solvent is added to a raw material consisting of beryllium oxide, aluminum oxide, and if necessary chromium oxide, iron oxide, and other auxiliary colorants or dopants, which have a composition ratio of almost the zone. , molybdenum trioxide, lithium molybdate, and lithium hydroxide are added to the molten salt and heated to a temperature higher than the melting temperature of the solvent to form a molten salt. By placing chrysoberyl seed crystals in the molten salt by holding it for a long time with a temperature difference, or by holding it for a certain period of time and then slowly cooling it with a gentle temperature gradient, the surroundings of the seed crystals are formed. This is a method of producing or growing chrysoberyl.

In this way, the molten salt method uses temperatures above the melting point, usually 900℃~
It can be produced or grown in a temperature range of 1500℃, but when it comes to growing high-quality chrysoberyl single crystals that do not contain inclusions in the crystal, there are many points that need to be managed, such as the temperature profile of the crucible furnace, the growth rate, and the type of solvent. There is. Inclusions can be broadly divided into those that incorporate molten salt, that is, feather inclusions, and those that incorporate crystalline substances that are produced in the same crucible in the same way as chrysoberyl. This is the main cause of the decline in transparency, which is a key point. These inclusions cannot be avoided at this stage in the synthesis of chrysoberyl single crystals by the molten salt method, and they are the biggest problem in terms of the quality of chrysoberyl single crystals.

The first cause of inclusions is that cracks occur due to internal stress in the crystal caused by the inability to control the crystal growth speed, resulting in feather inclusions. The second problem is bunching on the surface of the seed crystal, which occurs because the crystal growth speed cannot be controlled. Any cause can be prevented by keeping the crystal growth speed constant for a long period of time and controlling the growth to be low.

〔the purpose〕

The present invention solves the above-mentioned problems by synthesizing high-quality chrysoberyl single crystals by controlling temperature and crystal growth speed.

〔overview〕

In particular, in order to control the crystal growth speed, the present invention uses a buff-filled material inside the crucible together with vitrified or sintered raw materials (beryllium oxide, aluminum oxide, chromium oxide as a coloring agent, iron oxide, etc.). Divided into two zones, each consisting of a raw material dissolution zone and a seed crystal growth zone,
All of them are characterized by controlling the amount of dissolution by controlling the temperature and also controlling the amount of raw materials transported to the seed crystal zone, which further clarifies the effects of the present invention. Therefore, a detailed explanation will be given along with examples.

[Example 1] (1) Raw materials Beryllium oxide 4.0g Aluminum oxide 15.0g Iron oxide 0.5g The above raw materials were mixed and sintered.

The solvent used was 400 g of lithium molybdate and molybdenum trioxide in a 1:1 ratio.

(2) Apparatus and method A platinum crucible was used as the container into which the above substances were charged. For heating, the apparatus shown in FIG. 1 was used.

In FIG. 1, 1 is a heating device, and 2 is a lid of the heating device for preventing heat radiation from the heating device or preventing dust from entering. Heat the platinum crucible 9 with the heater 3, and measure the temperature by bringing the measurement terminal of the thermocouple thermometer 4 into contact with the platinum crucible 9.
Controls the temperature of the heating device.

Reference numeral 6 indicates a seed crystal introduced into the seed crystal growth zone 8, and reference numeral 5 indicates a raw material introduced into the raw material dissolution zone 7.

In the following description, the raw material dissolution zone 7 will be referred to as zone a, and the seed crystal growth zone 8 will be referred to as zone b.

A sintered body (beryllium oxide, aluminum oxide) was placed in zone a. Seed crystals were placed in zone b.

The heating temperature was set at 980°C for the a zone and 850°C for the b zone.

(3) Results No inclusions were observed in the chrysoberyl single crystal grown by maintaining the seed crystal growth speed constant for a long time.

[Example 2] (1) Raw materials The raw materials are the same as in Example 1. The solvent is lithium molybdate, molybdenum trioxide, and vanadium pentoxide in a ratio of 1:1:1.
400g was used.

(2) Apparatus and method The apparatus and internal layout of the container were the same as in Example 1.

The heating temperature was set at 925°C for the a zone and 900°C for the b zone.

(3) Results No inclusions were observed in the chrysoberyl single crystal grown by maintaining the seed crystal growth speed constant for a long time.

[Example 3] (1) Raw materials Beryllium oxide 4.0g Aluminum oxide 15.0g Iron oxide 0.5g Chromium oxide 0.5g The above raw materials were mixed and sintered.

Solvents include vanadium pentoxide and lithium hydroxide.
400g was used at a ratio of 10:1.

(2) Apparatus and method The layout inside the apparatus and container was the same as in Example 1, and the heating temperatures were set at 1070°C in zone a and 1040°C in zone b.

(3) Results No inclusions were observed in the chrysoberyl single crystal grown by maintaining the seed crystal growth speed constant for a long time.

〔effect〕

As described above, according to the present invention, a heating device is divided into a raw material melting zone and a seed crystal growth zone, a predetermined raw material or seed crystal is introduced into each zone, and the temperature difference between the two zones is maintained. Since chrysoberyl single crystals are synthesized or grown by attaching them, it is possible to easily obtain large single crystals that have no inclusions and do not break, and it is possible to provide chrysoberyl single crystals at low cost.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an outline of a heating device according to the present invention, FIG. 1a is a top view of the device, and FIG. 1b is a top view of the device.
shows a front view of this device. ...Heating device, ...Heating device lid, ...
...heater, ...measuring terminal of thermocouple thermometer,
...raw material, ...seed crystal, ...raw material dissolution zone, ...seed crystal growth zone, ...
Platinum crucible.

Claims (1)

[Claims] 1. Lithium molybdate, molybdenum trioxide, and water as a solvent to a raw material obtained by adding beryllium oxide, aluminum oxide, and, if necessary, coloring agents of chromium oxide and iron oxide, each having an approximately chrysoberyl composition ratio. A mixture containing at least one selected from lithium oxide and vanadium pentoxide is charged into the raw material dissolution zone of the crucible, which is divided into a raw material dissolution zone and a seed crystal growth zone by a batch, and the crucible is heated. The solvent is melted by heating to a temperature higher than the melting temperature of the solvent, the raw material dissolution zone and the seed crystal growth zone are filled with a molten salt of the solvent, and the seeds are placed in the seed crystal growth zone filled with the molten salt. A method for synthesizing or growing a chrysoberyl single crystal by adding crystals and making the temperature of the molten salt in the seed crystal growth zone lower than the temperature of the molten salt in the raw material dissolution zone. .