JPH05146663A - Superhigh pressure and temperature reaction process - Google Patents

Abstract

PURPOSE:To easily prepare a high quality product by providing the material and atmosphere stably useable in a reaction chamber especially at a pressure of about 5-8GPa and a temp. of at least 1200 deg.C in order to synthesize, nurture or sinter diamond, boron nitride and other high pressure phase crystals. CONSTITUTION:Starting materials are introduced into a container made of quartz material, which is then mounted on a high temp. high pressure device to bring the materials under the condition of the phase transition of the quartz to coesite or stishovite, whereby the container material is changed into the coesite or stishovite and whereby the materials in the container are subjected to a required pressure and temp. to synthesize and nurture a high pressure phase crystal or sinter polycrystal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrahigh pressure and high temperature reaction method, in particular, a starting material is subjected to ultrahigh pressure and high temperature conditions of about 5 GPa and 1200 ° C. or higher to obtain a high pressure phase such as diamond and cubic boron nitride. The present invention relates to a reaction method for synthesizing crystals, growing a single crystal, obtaining a polycrystalline sintered body, and the like.

[0002]

BACKGROUND OF THE INVENTION These processes require a container material that surrounds and effectively transfers pressure to the starting reactant materials while providing thermal and electrical insulation. Particularly required requirements for the container material include physical and chemical stability in addition to effective pressure transmission to the reaction material and good hydrostatic pressure. The latter is especially important in the case of the temperature difference crystal growing method, which requires maintaining a uniform environmental condition for a long time.

As such materials, natural minerals such as pyrophyllite and talc, calcined materials such as calcined wax and calcined magnesia, and glass such as borosilicate glass and macerite (trade name) have been used as a base material. Composite materials are used. However, plastic natural minerals contain water that inhibits synthesis and sintering reactions in the form of water of crystallization or bound water. Therefore, a treatment for removing the water is required prior to use, and in addition to an increase in economic burden, this treatment itself has a drawback of lowering the plasticity of the material. On the other hand, although the calcined material does not contain water or gas that may be an obstacle, the hydrostatic pressure is not necessarily good. Borosilicate glass, macerite, and the like have a drawback that they cannot be used as general materials because they have a low softening temperature. Further, borosilicate glass, in particular, lowers the purity of the produced diamond crystal, and is not suitable for growing a high-purity single crystal.

[0004]

Therefore, the present invention is
It provides a stable reaction chamber material or environment that can be used under the pressure and temperature conditions of 5 GPa or more and about 1200 ° C, which is used for crystal synthesis or growth of diamond or other minerals, and thus provides a high-quality product. The purpose is to facilitate the preparation.

[0005]

In the present invention, the container or reaction chamber for containing the carbon source and the flux is essentially made of quartz glass, and the reaction material, especially in the case of diamond crystal synthesis, is made of carbon. It is inserted between the source, the flux metal, etc. and the external electric heater, pyrophyllite, or other pressure medium. This can be configured in various shapes according to the design of the high-pressure device used, but in a general device, it is easy to make it into a sleeve (tube) shape. A commercially available quartz glass tube, which is available in a caliber size, can be used for the process simply by cutting it into a required length. Therefore, it is advantageous in terms of cost and time since no special processing device for forming a container material and a device and a process for molding and firing, which are required in the past, are required.

The quartz glass portion is heated under a pressure of about 2 GPa or more to cause a phase transition to coesite.
Since the phase transitions proceed rather quickly, it is practical to utilize part of the process (early heating) for this. For example,
This process is completed within a few minutes at 1100 ° C. under the pressure of about 5 GPa used for synthesizing diamond crystals. The phase diagram of SiO ₂ is described in, for example, H. We
ntorf, Jr. Editing, "Modern Ultra High Voltage Technology (Mode
rn very high pressure technology
Nikes) "(Butterworths, 19
1987), page 137.

In a quartz state, the quartz glass tube cracks and cracks when being pressurized in a high-pressure apparatus. At this time, the quartz glass is softened by heating and fused to the outer surface of the starting material. After that, it is preferable to cause a phase transition to coesite. In particular, in the crystal growing step, by performing this softening / fusion before the flux is still melted, it is possible to prevent the flux from flowing out from the crevice when the flux is melted. In addition, the starting material used here refers to various structures that are placed inside the reaction chamber (quartz glass tube) to adjust the pressure and temperature, if necessary, in addition to the reactants that are directly involved in the composition of the product. Including wood.

In any case, it is important to allow sufficient time for the phase transition from quartz to coesite before the reactant reaches the final heating temperature or the melting temperature of the flux. For this purpose, for example, by applying a pressure of about 2 GPa or more necessary for the phase transition at the beginning of heating, heating at a low speed, or holding at a temperature lower than the final reached temperature or the melting temperature of the flux for several minutes. Good. The phase transition progresses faster at higher pressures. Therefore, for example, under a pressure of about 5 GPa, at least 2 minutes, preferably 4 minutes before reaching such a temperature.
Allow a transition time of about 5 minutes. After that, heating can be performed at a regular rate to the final temperature.

[0009]

[Function] Coesite is 4-10 GPa, about 1000 ° C
It exists stably in the above condition range and its melting point is 2000
High enough above ℃. In addition, because it is chemically stable, the reaction turned to coesite for the synthesis and growth of diamond and cubic boron nitride and the sintering reaction of polycrystalline that are carried out in such temperature and pressure ranges. The container can provide a stable environment without time constraints.
Although the reaction site of coesite is somewhat inferior in hydrostatic pressure, this drawback can be easily overcome by reducing the proportion of the whole. Next, the present invention will be described with reference to examples.

[0010]

Example 1 Diamond seed crystals were grown using a reaction chamber configuration as shown in FIG. Outer diameter 8.2m
A macerite disc 2 was placed in the bottom of a fused silica glass tube 1 having a diameter of m, an inner diameter of 6.9 mm, and a length of 14.0 mm, and a diamond small crystal 3 was placed thereon as a seed. Further, a Kovar alloy disk 4 and an artificial graphite block 5 were placed on top of this, and the top was capped again with a block 6 of macerite. The outer diameters of the reactants 3 to 5 and macerite 2 and 6 are all 6.65 mm. A heating tube 7 made of graphite is arranged on the outer periphery of the tube 1, and NaCl-Zr
Filled with O ₂ sleeve 8 and metal (Mo) at the top and bottom
Quality discs 9 and 10, refractory rings 11 and 12, metal (steel) rings 13 and 14 for energization, pyrophyllite discs 15 and 16 for insulation and heat insulation, and a cylinder made of pyrophyllite to surround the whole. At 17, the pressure assembly was completed. This was attached to a piston-cylinder type high temperature and high pressure device, a pressure of 5.8 GPa was applied, and the temperature was kept constant at 1080 ° C.
Hold for minutes to transfer tubing to coesite. The temperature near the seed was set to about 1130 ° C., and the seed crystal was grown by heating at a temperature gradient of 23 ° C./mm in the axial direction for 24 hours. The recovered reaction vessel is completely transformed into coesite, and the obtained crystal has no inclusion, (1
The (00) plane was well developed.

[0011]

When carrying out the ultrahigh pressure and high temperature reaction according to the method of the present invention, for example, in a stable pressure and temperature condition range of diamond, a stable process environment is maintained for at least 24 hours without actually being restricted by time. Can be maintained. Also, especially in the case of diamond single crystal growth,
The crystals obtained in such an environment have almost no inclusion, and are excellent in both crystal quality and shape.
Characteristic is recognized.

In the above description, a method for synthesizing a diamond crystal and a method for growing a seed crystal have been mainly shown, but the method of the present invention synthesizes a high-pressure phase crystal operated in a similar pressure range, particularly cubic boron nitride. It is clear that it can also be used for growing and preparing sintered bodies of these high-pressure phases. Further, although the present invention has been described exclusively with regard to the phase transition from silica to coesite, it is subjected to a pressure of 10 GPa or more to obtain SiO 2.
Even if the phase transition of ₂ to stishovite occurs, it is stable under this pressure, and thus it is possible to provide a similarly stable operating environment.

[Brief description of drawings]

1 is a cross-sectional view showing the construction of a pressure assembly that can be used to carry out the method of the present invention.

[Explanation of symbols]

1 Fused quartz glass tube 2 Macerite disk 3 Diamond seed crystal 4 Kovar alloy disk 5 Artificial graphite ingot 6 Macerite ingot 7 Graphite heating tube 8 NaCl-ZrO ₂ sleeve 9 Metallic disk 10 Metallic disk 11 Refractory ring 12 Refractory ring 13 Metal ring 14 Metal ring 15 Pyrophyllite disc 16 Pyrophyllite disc 17 Pyrophyllite cylinder

Claims (7)

[Claims] 1. The starting material is placed in a container made of a quartz material,
The whole is attached to a high temperature and high pressure device, and quartz cossite (co
Ester), the container material is changed to coesite, while the starting material in the container is subjected to the required pressure and temperature to obtain the reaction product. Reaction method. 2. A container material is prepared by placing a starting material for crystal growth in a container made of a quartz material and mounting the whole on a high temperature and high pressure apparatus and subjecting it to a phase transition condition of quartz to coesite. In addition, the starting material in the container is subjected to the required pressure and temperature to synthesize, grow or sinter high-pressure phase crystals, which is an ultrahigh-pressure high-temperature reaction method. 3. A starting material containing a carbonaceous material and a flux is placed in a container made of a quartz material, and the whole is attached to a high temperature and high pressure apparatus, and subjected to thermodynamically stable pressure and temperature conditions of diamond. , The ultrahigh-pressure high-temperature reaction method of diamond, wherein the carbonaceous material in the container is transformed into diamond while the container material is changed to coesite. 4. A diamond seed crystal, a diamond and / or a non-diamond carbonaceous substance as a carbon source, and a metallic fluxing agent having a solubility for carbon during melting are placed in a container made of a quartz material, A diamond ultra-high pressure and high temperature, which is characterized by growing a diamond crystal by a temperature gradient method while being attached to a high temperature and high pressure device and being subjected to thermodynamically stable pressure and temperature conditions of diamond to change the container material to coesite. Reaction method. 5. A starting material containing a fine diamond crystal aggregate and a source of a molten metal that acts to form a bond between the aggregates is surrounded by a refractory metal and placed in a container made of a quartz material, Is attached to a high temperature and high pressure apparatus, and subjected to a phase transition condition of quartz to coesite, while changing the container material to coesite, while sintering the fine diamond aggregate in the container, Ultra high pressure high temperature reaction method. 6. A starting material comprising fine crystal aggregates of high pressure phase boron nitride and a source of molten metal which acts to form bonds between the aggregates is surrounded by a refractory metal and made of a quartz material. Put it in a container, attach the whole to a high temperature and high pressure device, and subject it to the phase transition condition of quartz to coesite,
An ultrahigh-pressure high-temperature reaction method, characterized in that a fine boron nitride aggregate in the container is sintered while the container material is changed to coesite. 7. The starting material is placed in a container made of a quartz material,
The whole material is attached to a high temperature and high pressure device and subjected to the phase transition condition of quartz to stishovite to change the container material to stishovite, while the starting material in the container is at the required pressure and temperature. An ultrahigh-pressure high-temperature reaction method, characterized in that the reaction product is obtained by subjecting to a high temperature.