JPH0686927A - Method for synthesis of diamond signal crystal - Google Patents

Abstract

PURPOSE:To provide a new method for synthesis of a colorless and transparent diamond single crystal which can be used for decorative applications and optical parts. CONSTITUTION:In synthesizing a diamond single crystal by means of temp. difference, one or two or more metals selected from Al, Ti, Zr or Hf as a nitrogen getter 3 are positioned on the solvent metal side and Sn 4 is positioned on the seed crystal side between the solvent metal and the seed crystal 5 positioned on a cell and synthesis of the diamond is started in such a way that the nitrogen getter 3 is not brought into contact with the seed crystal 5. As it is possible thereby to synthesize inexpensively and stably a IIa-type diamond crystal being colorless and transparent, with very few inclusions and with good quality, this method is a favorable method for preparation of a synthetic diamond which can be provided for decorative applications and optical parts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for synthesizing colorless and transparent diamond single crystals used for decorative purposes and optical parts.

[0002]

2. Description of the Related Art As decorative diamonds currently on the market, those which are colorless and transparent and have few internal defects are selected and used from those mainly produced in South Africa and the Soviet Union. Natural ornamental diamonds are the most sold gemstones. Moreover, there are laser windows, IR anvil cells, etc. as optical parts using diamond, but in each case, transparent diamond (called type IIa) that does not absorb light in the infrared region is selected from natural rough stones. It is used. However, the production of transparent and colorless rough stones is extremely low, and there are problems with stable supply and prices. On the other hand, artificially synthesized diamond is usually colored yellow due to the nitrogen in the solvent being taken into the crystal lattice when synthesized under ultrahigh pressure and high temperature, but it is colorless and transparent by adding a nitrogen getter to the solvent. You can get a diamond. As this nitrogen getter, for example, The Journal o
f Physical Chemistry, Vol.75, No.12 (1971) p1838
Al is well known as shown in FIG. Specifically, US Pat. No. 4,034,066 discloses Fe.
It is described that a gem-grade colorless and transparent diamond single crystal can be obtained by adding 3 to 5% by weight of Al to a solvent. As an example of using a nitrogen getter other than Al, for example, Nitrogen in a crystal is removed by adding Ti or Zr to a solvent metal in Research Report No. 39 (1984), pages 16 to 19 of Institute for Materials Research. There is a report that it was done.

[0003]

However, since the synthetic cost of the colorless and transparent synthetic diamond is much higher than that of the natural decorative diamond, industrial production has not been carried out. This is because the synthesis requires expensive and special equipment, and when Al or the like is added as a nitrogen getter,
As the amount of addition increases, the solvent is often taken into the crystal (hereinafter referred to as inclusion) and often becomes a defective crystal. Therefore, in order to obtain a good crystal, it is necessary to significantly reduce the growth rate. is there. Especially Ti and Zr
When used as a nitrogen getter, carbides (carbides) such as TiC and ZrC formed in the solvent during the synthesis
Is not incorporated into the crystal, so a perfect crystal cannot be obtained.

According to the result of the experiment conducted by the present inventors,
When Al is used as a nitrogen getter and uniformly mixed with a solvent metal, in order to synthesize a colorless and transparent diamond crystal, the addition amount thereof is at least 4% by weight (about 1%) with respect to the solvent.
2% by volume), but in this case the growth rate is 1 in order to grow crystals without inclusion inclusion.
It was necessary to keep it below mg / hr. With this growth rate, for example, a synthesis time of 200 hours or more is required to synthesize a 1-carat (200 mg) crystal, and the manufacturing cost becomes enormous. Further, when a substance having a higher reactivity with nitrogen than Al, such as Ti and Zr, is uniformly added to the solvent as a nitrogen getter, even if the addition amount is 2% by volume, a colorless and transparent crystal is formed, but the growth rate is significantly reduced. Even if so, a large amount of carbides such as TiC and ZrC are taken into the crystal, and a good crystal is hardly obtained. The present invention solves such a problem, provides a method of synthesizing a colorless and transparent crystal having almost no inclusion at low cost and stably, and enables the use of artificial synthetic diamond for decoration or optical parts. It is a thing.

[0005]

As a means for solving the above-mentioned problems, the present invention, in the diamond single crystal synthesis by the temperature difference method, arranges a solvent metal in contact with a carbon source, and arranges the solvent metal and the lower part thereof. One or two or more metals selected from Al, Ti, Zr or Hf are arranged as a nitrogen getter on the solvent metal side between the seed crystal and the nitrogen getter and the seed crystal by arranging Sn on the seed crystal side. It is characterized in that the synthesis of diamond is started in the state where the diamonds are not in contact with each other. In the present invention, the solvent metal is one or more selected from Fe, Co, Ni, Mn and Cr, and 0.1 to 6.
Those containing 0% by weight of carbon are particularly preferred. In addition, Al, T added as the nitrogen getter in the present invention
The addition amount of one or two or more metals selected from i, Zr, and Hf is 0.2 to 10 volume% with respect to the solvent metal, and the addition amount of Sn is 0.1 to 5 volume with respect to the solvent metal. % Is a particularly preferred embodiment of the invention.

In order to synthesize a colorless, transparent and inclusion-free crystal at a high growth rate by adding a nitrogen getter, the following method was used in the present invention. That is, since inclusions are more likely to be taken in as the amount of nitrogen getter added increases, it is desirable to minimize the amount of nitrogen getter. Therefore, the nitrogen getter is added (disposed) only in the vicinity of the seed crystal of the solvent. Further, since inclusion is trapped especially when there is unfilled residue during growth, Sn having the action of increasing the potential of carbon in the solvent is arranged between the nitrogen getter and the seed crystal in order to prevent this. When an element that easily forms carbides such as Ti and Zr is used as the nitrogen getter, the generated carbides hinder the crystal growth and the inclusion is included, but Sn suppresses the formation of such carbides. Alternatively, it also has a function of diffusing the generated carbide into the solvent before being taken into the crystal.

FIG. 1 is a schematic view showing the structure of a sample chamber for crystal synthesis, which is one embodiment of the present invention. On the solvent side between the solvent metal 2 and the seed crystal 5, a nitrogen getter (plate-shaped in FIG. 1) 3 made of Al, Ti, Zr, or Hf is added to the seed crystal 5.
On the side, Sn (which has a plate shape in FIG. 1) 4 is arranged. The nitrogen getter 3 may be one of Al, Ti, Zr, and Hf, or a combination of two or more, such as an Al plate and Ti.
It may be a stack of plates, a stack of Ti plates and Zr plates, or A
An alloy plate such as an l-Ti alloy or a Ti-Zr alloy may be used.
1 indicates a carbon source. Here, as the solvent metal 2, Fe,
One or more selected from Co, Ni, Mn, and Cr are used, but 0.1 to prevent dissolution of the seed crystal 5.
~ 6.0 wt% carbon is added beforehand. When a solvent metal containing less than 0.1% by weight of carbon or containing no carbon is used, it is necessary to dispose a seed crystal dissolution inhibitor such as Pt on the seed crystal.
Is not effective enough. Also, the amount of carbon added is 6% by weight.
If it exceeds, natural nucleation is likely to occur, and crystals grow from portions other than the seed crystal, so that the crystals interfere with each other, and it becomes impossible to obtain high-quality crystals. In the present invention, when the amount of Sn added is 0.1% by volume or less with respect to the solvent metal, the effect of preventing inclusion is not seen, and when Ti, Zr or the like is used for the nitrogen getter, TiC on the seed crystal. A layer of carbide such as is formed, crystal growth is hindered, and a large amount of these carbide remains in the crystal. If the amount added exceeds 5% by volume, polycrystallization and spontaneous nucleation tend to occur. Al, Ti, Zr as nitrogen getter,
When the amount of Hf added is less than 0.2% by volume with respect to the solvent metal, nitrogen is not sufficiently removed and the crystals become yellowish. On the other hand, if it exceeds 10% by volume, a large amount of inclusions are incorporated in the crystal.

The seed crystal, carbon source and the like used in the present invention may be those known in this type of technical field. Also,
The conditions for synthesis by the temperature difference method can be appropriately selected. Specific examples are given in Examples described later.

[0009]

According to the method for synthesizing a diamond single crystal according to the present invention, since the nitrogen getter is added (disposed) only in the vicinity of the seed crystal of the solvent, the nitrogen removal efficiency is high, and nitrogen is sufficiently removed even if the addition amount is small. Therefore, inclusion becomes difficult to mix. Further, since Sn is arranged on the seed crystal, the potential of carbon immediately before being incorporated into the crystal is increased, it is possible to prevent unfilling (inclusion), and it is possible to prevent TiC, ZrC, etc. from remaining in the crystal. Can be prevented. As a result, it becomes possible to synthesize a colorless and transparent diamond crystal having no inclusion at a high growth rate.

[0010]

【Example】

Example 1 In the sample chamber configuration shown in FIG. 1, diamond powder was used as the carbon source 1 and Fe: Co: C = 60: 4 was used as the solvent metal 2.
Alloy with a composition of 0: 4.5 (weight ratio), diameter 20
mm and a thickness of 10 mm were used. As the nitrogen getter 3, a Ti plate having a diameter of 20 mm and a thickness of 0.1 mm was arranged, and as the seed crystal side Sn4, Sn having a diameter of 20 mm and a thickness of 0.1 mm was arranged. At this time, the amount of Ti added to the solvent metal is 1% by volume, and the amount of Sn added is 1% by volume. As the seed crystal 5, three diamond crystals having a diameter of about 500 μm were used. The sample chamber was set on a heater so that a temperature difference of about 30 ° C. was created between the carbon source and the seed part. Using an ultra-high pressure generator, the pressure was 5.5 GPa and the temperature was 13
It was kept at 00 ° C. for 70 hours to synthesize diamond. As a result, three colorless and transparent, high-quality diamond crystals of IIa type having almost no inclusions of 0.7 to 0.9 carat were obtained. When the nitrogen concentration in the crystal was measured by ESR, all were 0.1 ppm or less.
When the inclusion amount was measured with a magnetic balance, all were 0.3% by weight or less.

Example 2 Diamond was synthesized in the same manner as in Example 1 except that a Zr plate having a diameter of 20 mm and a thickness of 0.1 mm (1% by volume with respect to the solvent metal) was used as the nitrogen getter 3. As a result, a good quality IIa diamond crystal, which is almost the same as in Example 1, was obtained.

Example 3 Diamond was synthesized in the same manner as in Example 1 except that an Hf plate having a diameter of 20 mm and a thickness of 0.1 mm (1% by volume based on the solvent metal) was used as the nitrogen getter 3. As a result, a good quality IIa diamond crystal, which is almost the same as in Example 1, was obtained.

Example 4 Diamond was synthesized in the same manner as in Example 1 except that an Al plate having a diameter of 20 mm and a thickness of 0.8 mm (1% by volume with respect to the solvent metal) was used as the nitrogen getter 3. As a result, a good quality IIa diamond crystal, which is almost the same as in Example 1, was obtained.

Example 5 As the nitrogen getter 3, a Ti plate having a diameter of 20 mm and a thickness of 0.1 mm (1% by volume based on the solvent metal), a diameter of 20 mm,
Diamond was synthesized in the same manner as in Example 1 except that Al plates having a thickness of 0.1 mm (1% by volume with respect to the solvent metal) were stacked and used so that the Ti plate was in contact with the solvent side. As a result, a good quality IIa diamond crystal, which is almost the same as in Example 1, was obtained.

Example 6 As a nitrogen getter 3, a Zr plate having a diameter of 20 mm and a thickness of 0.1 mm (1% by volume based on the solvent metal), a diameter of 20 mm,
Diamond was synthesized in the same manner as in Example 1 except that Al plates having a thickness of 0.1 mm (1 vol% with respect to the solvent metal) were stacked and used so that the Zr plate was in contact with the solvent side. As a result, a good quality IIa diamond crystal, which is almost the same as in Example 1, was obtained.

Example 7 Fe: Ni: Co: C = 60: 30: 10: as a solvent
Diamond crystals were synthesized in the same manner as in Example 1 except that an alloy having a composition of 4.2 (weight ratio) was used. As a result, a good quality IIa diamond crystal, which is almost the same as in Example 1, was obtained.

Example 8 Fe: Ni: Mn: C = 60: 30: 10: as a solvent
Diamond crystals were synthesized in the same manner as in Example 1 except that an alloy having a composition of 4.0 (weight ratio) was used. As a result, a good quality IIa diamond crystal, which is almost the same as in Example 1, was obtained.

Example 9 Diamond crystals were synthesized in the same manner as in Example 1 except that an alloy having a composition of Fe: Ni: C = 70: 30: 3.5 (weight ratio) was used as a solvent. As a result, a good quality IIa diamond crystal, which is almost the same as in Example 1, was obtained.

Example 10 A diamond crystal was prepared in the same manner as in Example 1 except that an alloy having a composition of Co: C = 100: 4.7 (weight ratio) was used as a solvent and the synthesis temperature condition was 1350 ° C. Synthesized. As a result, a good quality IIa diamond crystal, which is almost the same as in Example 1, was obtained.

Example 11 A diamond crystal was prepared in the same manner as in Example 1 except that an alloy having a composition of Ni: C = 100: 4.2 (weight ratio) was used as a solvent and the synthesis temperature condition was 1350 ° C. Synthesized. As a result, a good quality IIa diamond crystal was obtained, which was almost the same as in Example 1.

Comparative Example 1 An attempt was made to synthesize a diamond crystal in the same manner as in Example 1 except that the Sn plate was not arranged. As a result, diamond was hardly grown, and a TiC film was formed on the seed crystal surface.

Comparative Example 2 Example 1 was repeated except that no Sn plate was arranged and an Al plate having a diameter of 20 mm and a thickness of 0.8 mm (8% by volume based on the solvent metal) was used as the nitrogen getter instead of the Ti plate. An attempt was made to synthesize diamond crystals in the same manner as in. A colorless and transparent 0.8-carat crystal was obtained, but it contained a large amount of inclusions. The inclusion amount was 3% by weight.

Comparative Example 3 An attempt was made to synthesize a diamond crystal in the same manner as in Example 1 except that the nitrogen getter 3 was not arranged. As a result, a crystal of about 0.8 carat having almost no inclusion (0.3% by weight or less) was obtained, but it was a yellow type Ib crystal containing about 80 ppm of nitrogen as a substitution type.

Comparative Example 4 The thickness of the Sn plate was 0.7 mm (7% by volume based on the solvent metal).
Synthesis of diamond crystals was tried in the same manner as in Example 1 except that. As a result, polycrystallization occurred and a good single crystal could not be obtained. In addition, many spontaneous nucleation was observed from other than seed crystals.

Comparative Example 5 Synthesis of diamond crystals was tried in the same manner as in Example 1 except that the thickness of the Ti plate was 1.2 mm (12% by volume based on the solvent metal) without changing the diameter. As a result, a crystal of about 0.8 carat having a low nitrogen content was obtained, but a large amount of inclusion was contained. Nitrogen concentration is 0.1pp
Although it was m or less, the inclusion amount was about 5% by weight.

Comparative Example 6 A diamond was prepared in the same manner as in Example 1 except that an alloy having a composition of Fe: Ni: Co = 60: 30: 10 (weight ratio) was used as a solvent and carbon (C) was not added. An attempt was made to synthesize crystals. As a result, the seed crystal was completely dissolved in the solvent and disappeared, and no diamond growth was observed.

Comparative Example 7 Fe: Ni: Co: C = 60: 30: 10: as a solvent
Example 1 except that an alloy having a composition of 7 (weight ratio) was used.
Diamond crystals were synthesized in the same manner as in. as a result,
A large number of diamonds were naturally nucleated from places other than the seed crystal, and the crystals interfered with each other, so that a good quality crystal was hardly obtained.

[0028]

As described above, according to the present invention,
Crystals that are colorless and transparent and have almost no inclusion can be synthesized stably and inexpensively. The synthetic diamond according to the present invention can be used for decorative purposes, optical parts, etc.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing the structure of a sample chamber according to a specific example of the present invention.

[Explanation of symbols]

 1 carbon source 2 solvent metal 3 nitrogen getter 4 Sn 5 seed crystal

Claims (3)

[Claims] 1. In the synthesis of a diamond single crystal by a temperature difference method, a solvent metal is arranged in contact with a carbon source, and Al as a nitrogen getter is provided on the solvent metal side between the solvent metal and a seed crystal arranged below the solvent metal. To start the synthesis of diamond in a state where one or more metals selected from Ti, Zr or Hf are arranged, and Sn is arranged on the seed crystal side so that the nitrogen getter and the seed crystal are not in contact with each other. A method for synthesizing a diamond single crystal characterized by: 2. The solvent metal is Fe, Co, Ni, M.
The method for synthesizing a diamond single crystal according to claim 1, wherein the method comprises at least one selected from the group consisting of n and Cr and contains 0.1 to 6.0% by weight of carbon. 3. Al added as the nitrogen getter,
The addition amount of one or more metals selected from Ti, Zr or Hf is 0.2 to 10% by volume with respect to the solvent metal.
And the addition amount of Sn is 0.1 to 5 with respect to the solvent metal.
The method for synthesizing a diamond single crystal according to claim 1 or 2, wherein the content is% by volume.