JPH06182182A - Synthesis of single crystal diamond - Google Patents

Abstract

PURPOSE:To advantageously produce a colorless, transparent high-quality single- crystal diamond in the synthesis thereof employing temp. difference process by a method where Ti, etc., are added as nitrogen getter to a solvent metal, a metal plate such as made of iron is interposed between the solvent metal and seed crystal and, in this condition, the synthesis of the diamond is started. CONSTITUTION:In the synthesis of a single crystal diamond employing temp. difference process, one or more metals selected as nitrogen getter from among Ti, Zr, Hf, V, Nb and Ta are added to a solvent metal 2, a metal plate 3 consisting of one or more metals selected from among Fe, Co, Ni and Mn is interposed between the solvent metal 2 and seed crystal 4 and, in this condition, the diamond synthesis is started. Since, in this way, a colorless, transparent high quality IIa type diamond almost free from inclusion can be synthesized inexpensively and stably, a synthetic diamond useable for accessory or optical part application can be produced advantageously.

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 Decorative diamonds currently on the market are used by selecting those which are colorless and transparent and have few internal defects from those mainly produced in South Africa and Russia. Natural ornamental diamonds are the most sold gemstones. Moreover, there are laser windows and IR anvil cells 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. 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 because it is incorporated in the crystal lattice of nitrogen in the solvent 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 of Physi
Al is well known as shown in cal Chemistry, vol.75, No.12 (1971) p1838. In particular,
U.S. Pat. No. 4,034,066 describes Fe solvent as A
It is described that a gem-grade colorless and transparent diamond single crystal can be obtained by adding 3 to 5% by weight of 1. A
Examples of the use of nitrogen getters other than 1 include, for example, Research Report No. 39 of Inorganic Materials Research Institute, p.
There is a report that nitrogen in the crystal was removed by adding the to the solvent metal.

[0003]

However, since the synthetic cost of a colorless and transparent synthetic diamond is much higher than that of natural diamond, industrial production has not been carried out. The reason for this is that, in addition to requiring expensive and special equipment for synthesis, when Al or the like is added as a nitrogen getter, the solvent is taken into the crystal as the amount of addition increases (hereinafter referred to as inclusion), This is because the number of defective crystals increases, and thus the growth rate must be significantly reduced in order to obtain good quality crystals. In particular, when Ti or Zr is used as a nitrogen getter, more inclusions are taken into the crystal due to carbides such as TiC and ZrC formed in the solvent during the synthesis.

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 m in order to grow crystals without inclusion inclusion.
It was necessary to make it g / hr or less. At this growth rate,
For example, it takes 200 hours or more to synthesize 1 carat (200 mg) crystals, and the production cost becomes enormous. Further, when a substance having a higher reactivity with nitrogen than Al, such as Ti or Zr, is uniformly added to the solvent as a nitrogen getter, even if the addition amount is 1% by weight, colorless and transparent crystals are obtained. However, these tend to form carbides, and even if the growth rate is greatly reduced, good quality crystals are hardly obtained due to the influence of carbides such as TiC and ZrC. The present invention solves such a problem, provides a method of synthesizing a colorless and transparent crystal having almost no inclusions stably at low cost, and makes it possible to use an artificial synthetic diamond for a decorative use or an optical component use. To do.

[0005]

The present inventors have found that Ti and Z
Observation of a diamond crystal grown by adding r to a solvent as a nitrogen getter showed that most of the inclusions were continuously incorporated into the crystal starting from the seed crystal. Furthermore, detailed examination revealed that carbides such as TiC and ZrC formed on the seed crystal surface at the initial stage of growth were the starting points of inclusion. There is a place where Ti and Zr added in the solvent were in direct contact with the diamond of the seed crystal, and it is considered that TiC and ZrC were formed on the seed surface as a result of the reaction of Ti and Zr with the diamond when the synthesis started at that part. . Therefore, the present inventors, so that the solvent and the seed crystal do not come into direct contact,
Between the solvent and the seed crystal, Fe, Co, Ni, etc.
When a metal plate that can be a solvent for diamond synthesis and does not easily form carbide is arranged, it was found that almost no carbide such as TiC or ZrC is formed on the seed surface. At the same time, it was also found that the growth at the initial stage of growth was stable. As a result, it is possible to prevent inclusion of inclusions originating from carbide and inclusion of inclusions due to unstable initial growth, so that a high-quality IIa crystal can be obtained even at a growth rate twice or more faster than the conventional one. confirmed.

In the present invention, in the diamond crystal synthesis by the temperature difference method, the solvent metal, Ti as a nitrogen getter,
One or more metals selected from Zr, Hf, V, Nb and Ta are added, and further one or more metals selected from Fe, Co, Ni and Mn are added between the solvent metal and the seed crystal. It is characterized in that the synthesis of diamond is started in a state where the metal plate is formed. In the present invention, the thickness of the metal plate arranged between the solvent metal and the seed crystal is preferably 0.01 mm or more and 0.5 mm or less. Also, T used as a nitrogen getter
The content of one or more metals selected from i, Zr, Hf, V, Nb, and Ta is 0.
It is preferably from 2 to 10% by weight. These metals as nitrogen getters include other metals such as Al, Cu,
It can also be added in the form of an alloy with Si, Sn or the like. The solvent metal is composed of one or more selected from Fe, Co, Ni, Mn, and Cr, and is 0.1
It is preferred to contain ˜6.0 wt% carbon.

FIG. 1 is a schematic sectional view showing the structure of a sample chamber for synthesizing a diamond crystal, which is one embodiment of the present invention.
The solvent metal 2 includes Ti, Zr, Hf, as a nitrogen getter,
V, Nb, and Ta are added, and the metal plate 3 selected from Fe, Co, Ni, and Mn is arranged between the solvent metal and the seed crystal 4. The metal plate 3 may be an alloy such as Fe-Co or Fe-Ni. 1 is a carbon source, 5 is an insulator, 6 is a graphite heater, and 7 is a pressure medium. If the thickness of the metal plate 3 is less than 0.01 mm, the effect is insufficient, and if it exceeds 0.5 mm, the seed crystal often melts and disappears. Further, Ti, Zr, Hf, which is added to the solvent 2 as a nitrogen getter,
If the added amount of V, Nb, or Ta is less than 0.2% by weight, nitrogen is not sufficiently removed, and the synthesized diamond becomes yellowish crystals. On the other hand, if it exceeds 10% by weight, polycrystallization and natural nucleation increase, and a good quality diamond crystal cannot be obtained.

Here, the solvent metals of 2 are Fe, Co, N.
It is a metal consisting of one or more selected from i, Mn, and Cr, and is 0.1 to prevent seed crystal dissolution.
Carbon in an amount of 6.0% by weight is added in advance. 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. It is not preferable to dispose because of causing polycrystallization and inclusion inclusion. If the amount of carbon added exceeds 6% by weight, spontaneous nucleation tends to occur,
Since the crystals grow from a portion other than the seed crystal, the crystals interfere with each other, and a good quality crystal cannot be obtained.

[0009]

In the present invention, Ti, Zr, Hf, V, Nb, Ta are used.
For example, the element that has high reactivity with nitrogen is used as a nitrogen getter.
A IIa type diamond crystal is obtained, and is synthesized with a metal plate or alloy plate of Fe, Co, Ni, Mn pre-disposed between the solvent and the seed crystal for preventing carbide formation or stabilizing initial growth. Since it is configured to start, inclusion can be greatly suppressed. As a result, a good quality IIa type diamond crystal can be obtained even at a much higher growth rate than before. The seed crystal, carbon source, etc. used in the present invention may be those known in the technical field of this type. Further, the conditions for synthesis by the temperature difference method can be appropriately selected.

[0010]

The present invention will be described in more detail with reference to the following examples. Example 1 High purity F having a particle size of 50 to 100 microns as a raw material of a solvent
e powder, Co powder, and graphite powder were used and blended so that Fe: Co: C = 60: 40: 4.5 (weight ratio). To this, 1.5% by weight of Ti powder having an average particle size of 50 μm was further added as a nitrogen getter, and they were sufficiently mixed. This mixed powder is pressed and molded,
Degassed and fired (20 mm diameter, 10 mm thickness)
Was used as the solvent. In the sample chamber structure shown in FIG. 1, diamond powder was used as the carbon source 1, and three diamond crystals having a diameter of 500 μm were used as the seed crystals 4. As the metal plate 3 arranged between the seed crystal 4 and the solvent 2, a Co plate having a thickness of 0.1 mm was used. Then, the carbon source 1 and the seed crystal 4 were set in the heater 6 so that there was a temperature difference of about 30 ° C. Using an ultrahigh pressure generator, the pressure was 5.5 GPa and the temperature was 1
The temperature was maintained at 300 ° C. for 70 hours to synthesize diamond. As a result, a colorless and transparent 0.7-0.9 carat type IIa diamond crystal of good quality with almost no inclusion was 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 A metal plate 3 placed between a seed crystal 4 and a solvent 2 has a thickness of 0.1.
Diamond was synthesized in the same manner as in Example 1 except that a Ni plate of mm was used. As a result, a good quality IIa type diamond crystal, which is almost the same as in Example 1, was obtained. Example 3 A metal plate 3 placed between a seed crystal 4 and a solvent 2 has a thickness of 0.1.
Example 1 with the exception of using a 73 mm Fe-27 Co alloy plate
Diamond was synthesized in the same manner as in. as a result,
Almost the same quality IIa type diamond crystals as in Example 1 were obtained. Example 4 A metal plate 3 placed between a seed crystal 4 and a solvent 2 has a thickness of 0.1.
Example 1 except using a 50 Fe-50 Ni alloy plate of mm
Diamond was synthesized in the same manner as in. as a result,
Almost the same quality IIa type diamond crystals as in Example 1 were obtained.

[0012]Example 5 The thickness of the metal plate 3 arranged between the seed crystal 4 and the solvent 2 is 0.0
Example other than using a 5 mm 95Co-50Fe alloy plate
Diamond was synthesized in the same manner as in 1. That conclusion
As a result, IIa diamond of good quality which is almost the same as that of Example 1
Crystals were obtained. Example 6 The metal plate 3 arranged between the seed crystal 4 and the solvent 2 has a thickness of 0.3.
Die in the same manner as in Example 1 except that a 5 mm Co plate was used.
The synthesis of yamond was performed. As a result,
The same high quality type IIa diamond crystals were obtained.Example 7 Nitrogen getter added to solvent 2 has a particle size of 44 microns or less
3% by weight of Zr powder (average of 10 microns) in the solvent
Synthesis of diamond in the same manner as in Example 1 except for the addition
I went. As a result, II of almost the same quality as in Example 1
An a-type diamond crystal was obtained.

Example 8 Synthesis of diamond was carried out in the same manner as in Example 1 except that 3% by weight of AlTi alloy powder having a particle size of 44 microns or less (average of 10 microns) was added to the solvent in the nitrogen getter added to the solvent 2. went. As a result, a good quality IIa type diamond crystal, which is almost the same as in Example 1, was obtained. Example 9 Diamond was synthesized in the same manner as in Example 8 except that CuTi, SnTi, or Si ₅ Ti ₆ alloy powder was used instead of the AlTi alloy powder as the nitrogen getter added to the solvent 2. As a result, in each case, a good quality IIa diamond crystal, which is almost the same as that of Example 1, was obtained. Example 10 High-purity F having a particle size of 50 to 100 microns as a solvent raw material
e powder, Ni powder, Co powder, and graphite powder were used, and blended so as to be Fe: Ni: Co: C = 60: 30: 10: 4.2 (weight ratio), in the same manner as in Example 1. Diamond was synthesized. As a result, a good quality IIa type diamond crystal, which is almost the same as in Example 1, was obtained.

[0014]Example 11 High-purity F with a particle size of 50-100 microns as a solvent raw material
e powder, Ni powder, Mn powder, graphite powder
Fe: Ni: Mn: C = 60: 30: 10: 4 (weight
The same as in Example 1 except that the composition was
The synthesis of Mondo was performed. As a result, almost the same as in Example 1.
The same good quality IIa type diamond crystal was obtained. Example 12 High-purity F with a particle size of 50-100 microns as a solvent raw material
Diamond powder was prepared in the same manner as in Example 1 except that e powder, Ni powder, and graphite powder were used and blended so that Fe: Ni: C = 70: 30: 3.5 (weight ratio).
The synthesis of Mondo was performed. As a result, almost the same as in Example 1.
The same good quality IIa type diamond crystal was obtained. Example 13 High-purity C with a particle size of 50-100 microns as a solvent raw material
Diamond powder was used in the same manner as in Example 1 except that Co powder and graphite powder were blended so that Co: C = 100: 4.7 (weight ratio).
The synthesis of Mondo was performed. As a result, almost the same as in Example 1.
The same good quality IIa type diamond crystal was obtained.

Example 14 High-purity N having a particle size of 50 to 100 μm as a solvent raw material
Diamond was synthesized in the same manner as in Example 1 except that the i powder and the graphite powder were used and were mixed so that Ni: C = 100: 4.2 (weight ratio). As a result, a good quality IIa type diamond crystal, which is almost the same as in Example 1, was obtained.

COMPARATIVE EXAMPLE 1 No metal plate was placed between the solvent and the seed crystal, and the other example was used.
The synthesis of diamond was tried in the same manner as in. Crystals with a low nitrogen content (about 0.1 ppm) were obtained, but the inclusion amount was about 1.5% by weight, and a good quality crystal could not be obtained. Example 15 An attempt was made to synthesize diamond in the same manner as in Example 1 except that the thickness of the Co plate placed between the solvent and the seed crystal was 1 mm.
All the seed crystals were dissolved and disappeared, and no diamond was obtained. Example 16 An attempt was made to synthesize diamond as in Example 1, except that the amount of Ti added to the solvent as a nitrogen getter was 15% by weight. The crystal grown from the seed crystal was polycrystallized, and a good single crystal could not be obtained. Moreover, many spontaneous nuclei were also observed.

Example 17 High-purity F having a particle size of 50 to 100 μm as a solvent raw material
e powder, Ni powder, and Co powder were used, blended in such a manner that Fe: Ni: Co = 60: 30: 10 (weight ratio), and graphite was not added. The synthesis was carried out.
As a result, the seed crystal dissolves in the solvent and disappears,
No diamond growth was observed. Example 18 High-purity F having a particle size of 50 to 100 microns as a solvent raw material
Diamond powder was prepared in the same manner as in Example 1 except that Fe powder, Ni powder, Co powder, and graphite powder were mixed so that Fe: Ni: Co: C = 60: 30: 10: 10 (weight ratio). The synthesis was carried out. As a result, a large number of natural nuclei of diamond were generated from places other than the seed crystal, and the crystals interfered with each other, so that a good quality diamond crystal was hardly obtained.

[0018]

As described above, according to the present invention,
A colorless and transparent diamond crystal with almost no inclusion can be stably synthesized at low cost. This method makes it possible to use synthetic diamond for decorative purposes, optical parts, and the like.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the structure of a sample chamber for crystal synthesis, which is one specific example of the present invention.

[Explanation of symbols]

 1: Carbon source 2: Solvent metal (including nitrogen getter) 3: Metal plate 4: Seed crystal 5: Insulator 6: Graphite heater 7: Pressure medium

Claims (4)

[Claims] 1. In a diamond crystal synthesis by a temperature difference method, Ti, Zr, H as a nitrogen getter is used as a solvent metal.
One or more metals selected from f, V, Nb, and Ta are added, and one or more metals selected from Fe, Co, Ni, and Mn are included between the solvent metal and the seed crystal. A method for synthesizing a diamond single crystal, characterized in that synthesis of diamond is started in a state where a metal plate is arranged. 2. The synthesis of diamond single crystal according to claim 1, wherein the metal plate arranged between the solvent metal and the seed crystal has a thickness of 0.01 mm or more and 0.5 mm or less. Method. 3. T used as the nitrogen getter
The content of one or more metals selected from i, Zr, Hf, V, Nb and Ta is 0.
The method for synthesizing a diamond single crystal according to claim 1 or 2, wherein the content is 2 to 10% by weight. 4. The solvent metal is Fe, Co, Ni, M.
The method for synthesizing a diamond single crystal according to claim 1, 2 or 3, which is composed of one or more selected from n and Cr and contains 0.1 to 6.0% by weight of carbon. .