JPS63278545A - Diamond synthesis method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is a method of synthesizing diamond using an ultra-high pressure generator. Especially with high purity containing almost no nitrogen,
This invention relates to a method for synthesizing colorless and transparent diamonds. Large single crystals synthesized by this method are used for optical preparation materials, ultra-precision cutting tools, surgical knives, etc.

[Conventional technology and problems]

A colorless and transparent diamond that contains almost no nitrogen can be synthesized by adding 3 to 5% by weight of M to an Fe solvent as described in USP 4.043.066, or as described in Inorganic Materials Research Report N. (139 (1984) As described in PI3, the method was to add metals with a strong affinity for nitrogen, such as Zr and Ti, to Fe, Ni, and alloy solvents. However, as described above, when M, Zr, Ti, etc. When added, nitrides or carbides are formed between the metal and the solvent.It also improves the wettability of the synthesized single crystal with the solvent.Therefore, there are the following problems.

■ Fine inclusions of nitrides or carbides of added metals are incorporated into the crystal.

■ The metal solvent itself becomes easily entangled in the crystal.

The present invention aims to improve the above-mentioned drawbacks and provide a high quality single crystal without inclusions.

[Means for solving problems]

The present invention will be explained by taking as an example a single crystal synthesis by a temperature difference method.

The feature of the present invention is that instead of adding a metal that has a strong affinity for nitrogen as in the conventional method described above, an environment with extremely low nitrogen content is easily created and a single crystal is synthesized in that environment.

Therefore, in the present invention, we considered the source of nitrogen and used a method to remove the nitrogen before synthesizing the single crystal.

As shown in Figure 1, the sources of nitrogen are: ■ Nitrogen in the air existing in the cell gap ■ Nitrogen contained in the surrounding pressure medium ■ Nitrogen contained in the carbon source ■ Nitrogen contained in the solvent metal be.

The first feature of the present invention is that, as shown in FIG. 2, the reaction container of the ultra-high pressure generator is sealed with an airtight container and evacuated, thereby easily removing the nitrogen described in (2) above. = The synthetic part of the blade wheel crystal is packed into a capsule and sealed under vacuum,
Attempts have been made in the past to synthesize a single crystal by incorporating the capsule into an ultra-high pressure cell, as described in JP-A-56-140017. Therefore, a method for synthesizing in a vacuum and nitrogen-poor environment is known.

However, in the method using capsules as described above,
a) Encapsulation under vacuum is time-consuming. b) During compression, the capsule may break and the vacuum may be broken. h) When using a pressure medium made of powder or stamped material,
Nitrogen cannot be completely removed and the product does not become colorless and transparent. (Engineering) Since a capsule is used, the carbon source solvent becomes small and has the disadvantage that large single crystals cannot be formed. By using the above-mentioned method, which is the first feature of the present invention, the above-mentioned a) and b) can be achieved.

The shortcomings of (engineering) were solved.

Further, in the present invention, experiments were conducted regarding the relationship with the degree of vacuum, and it was found that a pressure of 10 Torr or less is effective.

A second feature of the invention is that 6.
Ti, Zr, , Hf, V
, Nb, Ta.

The reason is that metals that have a strong affinity for nitrogen, such as Cr and Mo, are mixed into the pressure medium. According to the present invention, it was possible to completely remove nitrogen from the pressure medium, which could not be removed simply by vacuuming. At the same time, the above-mentioned drawback (1) was also solved.

One or more of the metals mentioned above may be laminated in plate form or powdered and mixed, but the latter method is preferred.

Furthermore, in the present invention, experiments were also conducted regarding the relationship between the mixing amount of the above-mentioned metals and the synthesized single crystal. As a result, it was found that if the mixing amount was less than 0.5% by volume, there was no nitrogen removal effect;
In the above, a reaction occurs between the metal and the solvent or heater,
This resulted in the inconvenience that synthesis could not be performed with good reproducibility.

More Aj! A similar experiment was conducted by mixing metals with low melting points such as Mn and Mn, but a reaction occurred between the metal and the solvent or heater.

The third feature of the present invention is that high purity raw materials are used and nitrogen in the carbon source and solvent metal is removed.

The carbon source is highly purified 1 with a nitrogen content of several ppn+ or less.
It is preferable to use type 1a abrasive grains.

In addition, in the present invention, we also conducted experiments on the relationship between the content chamber and the elementary amount and the synthesized single crystal, and found that in the carbon source, the nitrogen content was 20
It has been found that a concentration of 5 ppm or less for solvent metals is effective. We also found that electron beam dissolution is the most suitable method for producing this solvent.

[Effects of the Invention] According to the present invention, it has become possible to easily and reliably synthesize high-quality colorless and transparent single crystals that do not include nitrides, carbides, or metal solvents in the crystal and contain almost no nitrogen. .

Example 1 As shown in FIG. 2, the reaction vessel of the ultra-high pressure generator was sealed with an airtight container and evacuated. The degree of vacuum is 5 as shown in Table 1.
The pressure was varied up to 50 Torr.

The results are shown in the table below. The cell configuration used for single crystal synthesis is the third
As shown in the figure, all experiments were the same, and the pressure medium used was a mixture of pyrophyllite powder to which Zr powder was added at 2 VoA%, the mixture was pressed, and then shaped.

Further, as a carbon source, a 1:1 mixture of Type IIa abrasive grains and graphite for spectroscopic analysis and stamping was used.

The nitrogen concentration of the embossed body was analyzed and found to be 12 ppm. Further, as the solvent metal, a Pa-Co alloy containing 50% by weight of Pa was used. The nitrogen concentration of the solvent was analyzed and found to be 5 ppm. In addition, the synthesis conditions are 5.5G Pa, 140
It was carried out at 0°C. The synthesized single crystal has a ratio of 0.5 to 0.71/
It weighed 1,000 yen.

Example 2 The inside of an airtight container as shown in FIG. 2 was evacuated to 5 Torr before pressurization. Moreover, using a cell configuration as shown in FIG.
A Pa-Co alloy containing 50% by weight of Fe was used as the solvent.

In addition, high-purity graphite for spectroscopic analysis was used as a carbon source. When nitrogen analysis was performed on each, the content was 16p.
pm and 3 ppm. Further, as a pressure medium, a mixture of pyrophyllite powder and Ti varying from 0.2 to 15Vo by 1% was pressed and used.

The synthesis conditions were 5.6 GPa and 1420°C, and the weight of the single crystal obtained was 0.4 to 0.6 ct/piece.

The experimental results are shown in Table 2.

The same results were obtained using other solvents consisting of one or more elements of Pe, Co, Mn, Ni, and Cr.

Example 3 As shown in Fig. 2, the inside of the airtight container was heated to 5 Torr before pressurization.
It was pulled to a vacuum. Also, using a cell configuration as shown in Figure 3,
The solvent contained Pe-, which contained 70% by weight of Pe and 30% by weight of Mn.
A Mn alloy was used. The nitrogen content was 4 ppm.

As a pressure medium, apply Z'' to pyrophyllite powder at 2V.
A mixture of oA% was pressed and used.

Table 3 shows the results of an experiment in which graphite for spectroscopic analysis and graphite powder for general use were mixed as a carbon source, and the nitrogen concentration was varied from 8 to 50 ppm.

The synthesis conditions were 5.60 Pa and 1400°C, and the weight of the single crystal obtained was 0.4 to 0.6 ct/piece.

The same results were obtained using other solvents consisting of one or more elements of Pa, Co, Mn, and Cr.

Example 4 As shown in Fig. 2, the inside of the airtight container was heated to 5 Torr before pressurization.
It was pulled to a vacuum. Also, using a cell configuration as shown in Figure 3,
A Pa-30Co alloy containing 70% by weight of Fe was used as the solvent. A metal solvent having a nitrogen content of 3 to 20 ppm was prepared using electron beam melting and vacuum melting. As the pressure medium, a mixture of pyrophyllite powder and 5Vo1% of Nb was pressed and molded.

Furthermore, graphite for spectroscopic analysis was used as a carbon source.

The nitrogen content was 15 ppa+.

The synthesis conditions were 5.7 GPa and 1450 DEG C. The experimental results are shown in Table 4, and the weight of the single crystal obtained was 0.3 to 0.4 ct/piece.

Table 4

[Brief explanation of drawings]

FIG. 1 shows a conventional cell configuration for diamond synthesis using the temperature difference method. 1 is an anvil, 2 is a cylindrical die, 3 is a cell gap, 4 is a pressure medium, 5 is a carbon source, 6 is a solvent metal, 7 is a seed crystal, and 8 is an electrode. FIG. 2 shows a vacuum-tight section according to the invention. A. B is the vacuum-tight part, 11 is an anvil, 12 is an anvil reinforcing case, 13 is a die, 14 is a die reinforcing case, 15
is the vacuum direction, 16 is the airtight container, and 17 is 0 for vacuum sealing.
ring, 18 is an electrode, 19 is a carbon source, 20 is a seed crystal, 2
1 is a solvent metal, 22 is a pressure medium, and 23 is a carbon heater. FIG. 3 shows a cell configuration according to the invention. 31 is an anvil, 32 is a cylindrical die, 33 is a gasket, 34 is a pressure medium according to the present invention, 35 is a carbon heater, 36 is a low nitrogen concentration carbon source according to the present invention, 37 is a low nitrogen concentration metal solvent according to the present invention, 38 is a Seed crystals are shown in each case. /, Ambill 4. Pressure 1 piece 7.4 weights, 6 crystals 2, cylindrical die 57 pieces 48. Reitoku 3, +tru/11 demon eyes 2 Ne medium 4 Me Mei Kay 2 figures

Claims (1)

[Claims] (1) The reaction vessel of the ultra-high pressure generator consisting of an anvil or die, or a part of the vessel, is sealed with an airtight container, the inside of the airtight container is evacuated to 10 Torr or less, and Ti, Zr, Hf, V, Nb, Mo, Ta, Cr, Mn
0.5 to 1 metal powder consisting of one or more of the following.
Pressure medium mixed with 0% by volume and nitrogen content concentration is 20pp
m or less carbon raw material and 5 ppm or less Fe, Co
, a metal solvent made of one or more elements among Ni, Mn, and Cr is placed in the reaction vessel and heated under pressure to a diamond stable region to grow diamond on the seed crystal. A method for synthesizing diamond having a nitrogen content of 2 ppm or less.