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INVENTION
Patent of the Russian Federation RU2156330
PRECIOUS STONES FROM SILICON CARBIDE
Name of applicant: SI THREE, INC. (US)
The name of the inventor: HUNTER Charles Eric (US); VERBAYST Dick (US)
The name of the patent holder: SI THREE, INC. (US)
Address for correspondence: 125040, Moscow, Leningradsky Prospect 23, "Transtechnology", Zolotykh N.I.
Date of commencement of the patent: 1996.08.27
The invention relates to synthetic gemstones made from semi-transparent monocrystalline silicon carbide and can be used in the jewelry industry. Synthetic gemstones that have extraordinary gloss and hardness are made of large single crystals of translucent silicon carbide of one polytype with a relatively low content of impurities. The crystals are grown in a system using a sublimation furnace. The crystals are cut into unpolished gemstones, which are then shaped into shape, and thus processed gemstones are obtained. In the process of growing with the chosen additives to the crystal stones acquire a variety of colors and shades. A colorless gemstone is obtained by growing a crystal without an additive in a system protected from unwanted impurity atoms.
DESCRIPTION OF THE INVENTION
The invention relates to synthetic gemstones. In particular, the invention relates to synthetic gemstones made of translucent monocrystalline silicon carbide.
General information about precious stones. The number of elements and chemical compounds having physical characteristics that meet the requirements for precious stones is limited. The physical characteristics commonly considered as the most important in this sense include hardness, refractive index, and color, although heat resistance, chemical resistance and adhesion are considered important properties in many applications of gemstones.
To date, the only chemicals that are technically considered precious stones are diamond (single crystal carbon) and corundum (sapphire and ruby) (single crystal alumina), since their Moss hardness is 9 or more units. The Mosa system is a scale for determining the hardness of a mineral, according to which the hardest is diamond (10 units), sapphire (9 units), topaz (8 units) and so on to the softest mineral, talc, whose hardness is 1. Emerald, , That it is rare in nature, is referred to as gemstones, despite the fact that its hardness is 7.5, while other precious stones, such as chrysoberyl, topaz and garnet are usually referred to as semi-precious because of their lower Hardness index. Hardness is of practical importance, because it determines the resistance of the precious stone to scratching.
The value of the refractive index is that it determines the ability of the precious stone to refract light. When receiving processed precious stones from materials with a high refractive index, the stones sparkle and shine in the light. The characteristic sparkling of a diamond is mainly due to its high refractive index.
The color of the gemstone is determined by a number of factors, from impurity atoms that can be incorporated into the crystal lattice, to the physical and electronic structure of the crystal itself. For example, a ruby is a simple sapphire crystal (aluminum oxide) with a small concentration of impurity atoms in the form of chromium.
The heat resistance and chemical resistance of the gemstone can be important indicators for the insertion of stones into jewelry. In general, it is convenient if the stones can be heated to a high temperature without changing the color or reacting with the gases in the environment (which damage the finish of the surface).
The adhesion of the gem is related to its ability to absorb energy without destruction, splintering or splitting. A gemstone must have the property of resisting shocks that are common during the service life if the stone is inserted into a ring or other piece of jewelry.
Hardness, refractive index, color, thermochemical resistance and adhesion are all characteristics that combine with each other to determine the suitability of the material for use as a precious stone.
Synthetic diamonds. Since the 1960s, as seen from numerous patents, including US Patent No. 4,042,673, General Electric has attempted to produce synthetic diamonds that meet the quality requirements for precious stones. These attempts were focused on the use of very high pressure / high temperature environments to grow single crystal diamonds on seed crystals. Synthetic diamonds with the properties of the precious stone, as a rule, did not get distribution on the market.
Synthetic silicon carbide as an abrasive and semiconductor material. Silicon carbide is rarely found in nature. However, it has been produced for more than eighty years in a crystalline form for abrasive products. Crystals of silicon carbide, found in nature and in abrasive products, are black and opaque, since they have a significant level of impurities.
In the 1960s and 1970s, significant activity was developed in the field of development of growing large (volume) crystals with a low content of silicon carbide for their use in the production of semiconductor devices. As a result, these attempts led to the fact that in 1990, semi-transparent crystals of silicon carbide with relatively low impurity content appeared in production. These silicon carbide crystals are manufactured and sold only as very thin, green or blue cuts (175 μm - 400 μm) used in semiconductor devices.
Silicon carbide has a very high hardness (8.5-9.25 units on the Mohs scale, depending on the polytype (arrangement of atoms) and crystallographic direction) and a high refractive index (2.5-2.71, depending on the polytype). In addition, silicon carbide is a material with a very high coefficient of adhesion and an extremely strong material that can be heated to a temperature well above 2000 ° F (1093.3 ° C) in air without fracture.
Silicon carbide is a complex system of material, including more than 150 different polytypes, each of which has different physical and electronic properties. These different polytypes can be divided into three main forms: cubic, rhomboidal and hexagonal. Both rhomboidal and hexagonal forms can occur in a number of different atomic arrangement systems, which differ depending on the sequence of atoms arrangement.
BRIEF SUMMARY OF THE INVENTION
The present invention in its broadest sense is the discovery that a single silicon carbide crystal with low impurity content, translucent, currently used as a material for the manufacture of very thin semiconductor devices, can be grown with the desired coloring and then cut, granulated and ground (I) a hardness close to diamond, (ii) high adhesion, (iii) excellent thermochemical resistance, and (iv) a high refractive index that gives a gemstone of silicon carbide a sheen equal to if Not more, the brilliance of a diamond. According to this aspect of the invention, a single silicon carbide crystal, preferably of a suitable color, is grown by an appropriate technique, such as the sublimation method described in the patent No. Re. 34.861 Instead of dividing a large crystal into many thin sections, the crystals are used as beads, which are cut into unpolished synthetic gemstones weighing in the order of, for example, 1/4 to 5 carats. The unrefined gemstones are then shaped until a synthetic synthetic gemstone of silicon carbide is obtained. The methods of faceting and polishing are based on the currently used methods of cutting and polishing colored gems such as rubies and sapphires, including certain methods used for diamonds.
As indicated above, single crystals of silicon carbide are preferably grown under the same or similar conditions that are used to produce crystals with a low content of impurities and are necessary for semiconductor devices, and it should be noted that higher levels of impurity content can be tolerated in Established limits, depending on the need for materials with an appropriate degree of translucency and other optical properties, corresponding to the use of the precious stone.
Silicon carbide crystals can be grown using a wide range of color solutions (including green, cyan, red, magenta, yellow and black) and shades of each color, by selecting appropriate additives (eg nitrogen or aluminum) and by changing the density of additives (concentrations). Crystals of silicon carbide without additives with hexagonal and rhomboidal forms are colorless and have a brilliance equal to that of a diamond, or higher.
Unrefined gemstones from silicon carbide are cut from large single crystals, and then processed to processed gemstones by combining the methods currently used to produce conventional colored gemstones and diamonds. The hardness and solderiness of silicon carbide makes it possible to cut stones with very sharp edges, which improves the overall appearance and enhances the shine of the stones.
BRIEF DESCRIPTION OF THE DRAWINGS
Some items are already listed, other items will be listed below when referring to accompanying drawings on which:
 FIG. 1 - a ball of a large single crystal of one silicon carbide polytype |
 FIG. 2 is an enlarged view of an uncut synthetic gem cut from a single crystal depicted in FIG. 1 |
 FIG. 3 is an enlarged view of a treated synthetic gemstone made of silicon carbide made of unrefined stone depicted in FIG. 2 |
DETAILED DESCRIPTION OF THE INVENTION
Since a more complete description of the invention is given with reference to the accompanying drawings and the description includes questions about preferred methods of application of the present invention, after reading the following description, it is to be understood that those skilled in the relevant art can modify the invention described herein while achieving the successful results of this invention . Accordingly, the following description should be understood as extensive teaching information intended for those skilled in the art, but not limited to the present invention.
In Fig. 1 shows a bead, a large single crystal 11 silicon carbide weighing approximately 716 carats, from which approximately 105 uncut synthetic gemstones (FIG. 2) of five carat weight can be cut. From each precious stone weighing five carats you can get a processed precious stone weighing about two carats. The crystal 11 is generally cylindrical and measures approximately 44 mm in height and 40 mm in diameter. For the preferred application of the invention, the crystal 11 is obtained from a single polytype with a rather wide energy range (a fairly small number of electrically active impurity atoms) for example a hexagonal shape such as 6HSiC and has a sufficiently low level of impurities, i.e., additives, to impart A crystal of sufficient brilliance in order to use it as a precious stone.
The crystal 11 is grown by a suitable sublimation or precipitation method, or by another growth method used to grow a large (bulk) single silicon carbide crystal, and it is preferred that the sublimation is grown on a seed crystal. According to this preferred method, the crystal 11 is grown as a result of placing a polished single crystal seed crystal of silicon carbide with the necessary polytype into the furnace of the sublimation system together with the source gas or powder containing silicon and carbon (starting material). The starting material is heated to a temperature sufficient to generate a vapor stream, as a result of which deposits of evaporating Si, Si 2 C and SiC 2 form on the growth surface of the filler crystal. The reproductive growth of one selected polytype on a seed crystal is achieved by maintaining a constant flux of Si, Si 2 C and SiC 2 and by monitoring the temperature gradient between the starting material and the seed crystal.
Crystals grown by the sublimation method are used as a material from which very thin sections are taken to be used in the production of semiconductor devices. These sections (175-400 μm) have a green and blue color, like a crystal, and the color (and the necessary electrical properties) is obtained by adding specially selected additives of a certain concentration during the growth process.
Silicon carbide without additives, i.e. Unalloyed (genuine) was not grown in an industrial way. The extremely low electrical conductivity of undoped silicon carbide explains its low or almost zero value for the production of semiconductor products. However, it has been found that since hexagonal and rhomboidal silicon carbide polytypes have large energy ranges (> 2.7 eV), if they are grown without additive (or, equivalently, with very low levels of impurity atoms or very low levels of electrically active impurity atoms), the crystals will be Colorless. In order to grow unalloyed single colorless silicon carbide crystals, the crystal growth system is maintained basically free of atoms of undesired gaseous or vaporous impurities that lead to an unintentional addition of the crystal immediately after cultivation using the low pressure drying method, as is well known in the art . The preferred polytypes for colorless gemstones are 6HSiC and 4HSiC. The seed to begin the growth of a single crystal for such precious stones is a primer having the same polytype, 6HSiC or 4HSiC, respectively.
To obtain crystals of silicon carbide of hexagonal form, having different colors, it is necessary to add atoms of certain impurities. Cubic form, or form 3C, silicon carbide because of its narrower energy range will be yellow in the absence of an additive in the form of impurity atoms. Since there are a large number of different silicon carbide atom arrangement systems (to which any additive can be added in the form of a number of different additives in various combinations and with different concentrations), it is possible to obtain precious stones with a large range of colors and shades. For the 6H polytype, the commonly used additives are nitrogen (n-type) and aluminum (p-type) in concentrations usually from low, about 10 15 carrier atoms per cubic centimeter, to high, about 10 19 carrier atoms per cubic centimeter. Other additives, such as boron, can be used in concentrations sufficient to obtain the necessary colors and shades. In Table. 1 shows various systems of arrangement of atoms and additives, which give several characteristic primary colors.
Despite the fact that the combinations given in Table. 1, give a wide variety of colors, all crystals have two very important characteristics in common: (1) high hardness and (2) high refractive index. Silicon carbide is compared with other materials for precious stones by hardness and refractive index, and by density (see Table 2).
As it follows from Table 2, silicon carbide obtained under a certain system of atoms arrangement under controlled input of certain additive atoms is an excellent material for a gemstone having physical characteristics that favorably differ or exceed the physical characteristics of corundum and emerald. In its hexagonal or rhomboidal forms without additives (in particular, in hexagonal forms, repeating the same structure of atoms through every six layers of atoms, that is, 6H), silicon carbide is the most famous candidate, repeating the characteristics of diamond.
PROMOTION OF THE FORM WITH PRECIOUS STONES
Returning to the drawings, it can be said that the silicon carbide 11 crystal (Figure 1) weighs perhaps 716 carats and is cut into numerous uncut synthetic gemstones 12 (one of which is shown in Figure 2) having a certain weight, for example five carats. The uncoloured gemstone 12 preferably has a cubic or approximately cubic shape. It has been found that, in order to obtain a treated gemstone, as shown in FIG. 3, the unpolished gem is desirable to give the shape of the processed gemstone according to the newest developed process, the most convenient for using the advantages of the physical characteristics of silicon carbide. This process involves a cutting method that allows you to obtain precise angles and very sharp edges that allow you to take full advantage of the adhesion and hardness of silicon carbide while using other methods more similar to those used for colored stones. A more complete description of the shaping process is given below, after a brief description of the shaping process in general and information on certain issues of shaping colored gemstones such as rubies, sapphires and emeralds.
General description of the shaping process (prior art)
The process of shaping gems involves applying four methods: cutting, tumbling, preforming and cutting. As a result, the facings get flat facies (facets) on stones of many different shapes. Transparent and highly translucent stones are usually restricted. Less transparent and opaque minerals are usually treated by tumbling, or threading, because the optical properties associated with faceting depend on the reflection of light in the direction of the stone.
The shape of the gemstone is the shape of its upper surface, the position in which it will be looked upon after installation into the article. The surface forms, except round ones, are figured. Some popular figured forms include the following well-known: emerald cut, cabochon, antique cabochon, oval, pear and marquise. Colored stones (and diamonds weighing more than three carats) are usually cut into shape in the process of cutting, as the cutter can save a large weight of the original gemstone, using a shape, thus reducing the weight loss of the stone.
The exact standard cut that can be seen in diamonds is rarely found in colored stones. One of the reasons is the impossibility of cutting some colored stones to sharp angles without destroying the stones or dividing them into slices because of their lower hardness and cohesion. Another reason is the difference between what professionals and consumers expect from diamonds compared to other stones. "Eastern or" colonial "cutting" are terms used to describe faceted gemstones that have distorted shapes and wrong facet locations, which more often can be attributed to colored stones. Most colored stones are limited to a degree sufficient to penetrate light.
Most cut stones have three main parts: the crown, the girdle and the corolla. The crown is the upper part, the girdle is the narrow part that forms the boundary between the crown and the corona and is the setting edge of the gem. Corolla is the bottom part of the stone. Colored stones usually have facets on the corolla.
General description of the process of shaping colored stones
The border of colored gemstones starts with the grinding of the unpolished colored stone until the approximate shape and dimensions of the processed stone are obtained. This process is called the preliminary shaping process. Preliminary shaping is performed using a coarse abrasive tool. A large diamond grain embedded in a nickel plated copper disk is the best choice for preforming very hard colored stones (corundum, chrysoberyl, spinel and silicon carbide).
Water is a wetting agent in the process of preforming and subsequent faceting processes. Cutters of precious stones use different means to maintain the humidity of the circles. In the process of preliminary shaping, the belt and the overall profile of the corona and corolla are grinded, and the surface of the entire stone becomes matte at the same time. Before polishing the facets, the cutter must insert the stone into the filler rod. The method is called doping. The stone is slightly heated, then placed on the end of the additive previously placed in the molten filler wax. After setting the stone processed to the pre-form into the required position, it is set aside for cooling.
The facets of a colored stone are polished on horizontal, rapidly rotating circles, called grinding wheels. Cutters use a number of circles for cutting with grains of different sizes, increasing, for grinding the facets and gradually leveling their surfaces. Then, the final grinding is carried out on a special grinding wheel for grinding the surface.
Grinding wheels for grinding are made of different materials. The grinding agents used for these wheels are very fine-grained powder materials including diamond, corundum, cerium oxide, and tin oxide. For cutting and grinding at the required angle, respectively, the cutter brings the seed rod to the device in which the stone is held while it is in contact with the circle. A traditional tool for installation, used in many workshops for processing colored stones is a special holder. It has a section mounted on a vertical support. The filler rod is inserted into one of the row of holes on the side of the section. The position of each hole determines the specific size of the angle (from the plane of the stone belt), under which the facet is cut. By turning the filler rod in the hole, all facets of this type are installed at the same angle along the entire circumference of the stone.
The process of shaping the precious stones of silicon carbide
Since the beauty of most diamonds depends on the degree of their glittering, shine and radiance (not color), diamond carvers must carefully monitor the factors that affect these characteristics. It is very difficult to install cut diamonds on colored gemstones.
In view of the fact that the refractive index of silicon carbide is greater than that of diamond and colored stones, according to the present invention, a silicon carbide gemstone is manufactured using precision diamond tools used in diamond hand tools known as "diamond". "Diamonds" allow the carver to set and adjust the facet angle, something that the cutter can not do with pre-installed tools for colored stones. Precisely the precision of diamond hand tools, "diamonds", allows the carver to use the angle and proportions of the diamond, which allows to obtain "sharp edges" on the precious stones of silicon carbide to which the present invention belongs. However, since silicon carbide is not as hard as diamond, traditional grinding wheels for colored stones are used in the cutting process at a speed below the speeds normally used for diamond wheels, i. E. Less than 3000 rpm, and preferably with a rotational speed of about 300 rpm.
For a more detailed understanding of the method for shaping the silicon carbide described in the present invention, it should be noted that the unrefined gemstone of silicon carbide is mounted on the filler rod and fixed in the upper "diamond". The edge of the belt is cut first on the grinding wheel. This determines the shape of the stone.
The top face, the flat upper surface, which is the largest facet on the entire stone, is cut in the next turn, and with the use of a "diamond" for the face. The face is then sanded in four stages using grinding wheels (discs, wheels, etc.) from coarse to fine grained. Grinding can begin with a circle of grain size 600, then go to the size of 1200, and then to 3000 and finish it with a ceramic disk with a grain size of 0.5 to 1 micron, the smallest.
The additive is then transferred to the upper "diamond" to cut the upper side and obtain an intersection that includes 4 main parts (facets). Then the additive passes to the lower "diamond", and the lower side is cut to obtain an intersection that includes 4 main parts (facets). At this time, the stone is visually inspected to determine its accuracy. After this check, the grinding process using grinding wheels described for the face is repeated for the main parts.
The additive is transferred to the upper "diamond" and facets of the "star" of the upper side - all such facets are cut 8 together with the upper facet facets (16 facets). The additive is transferred to the lower "diamond", and the lower facets of the belt are cut (16 facets). The grinding process using 4 grinding wheels, described for the face and the main parts, is repeated for the rest of the belt facets. Now, the untreated stone became a faceted polished gemstone with a round brilliant cut 13, as shown in FIG. 3.
Since the description of the invention is accompanied by the drawings, it is important that the modifications be made without departing from the true spirit and scope of the invention.
CLAIM
1. Treated synthetic gemstone made of silicon carbide with ground facets, characterized in that it consists of a single crystal of synthetic silicon carbide, while the facets are sufficiently ground to refract light in the precious stone.
2. The processed synthetic gemstone of silicon carbide according to claim 1, characterized in that the synthetic silicon carbide has a crystalline structure selected from the group consisting of 6HSiC and 4HSiC.
3. Artificial diamond, characterized by the fact that it consists of a single crystal of colorless synthetic silicon carbide with facets, sufficiently polished to refract light in the precious stone.
4. An artificial diamond according to claim 3, characterized in that said facets are characteristic for diamond cutting.
5. An artificial diamond according to claim 4, characterized in that said diamond cutting is a round brilliant cut.
6. An artificial diamond according to claim 3, characterized in that the synthetic silicon carbide has a crystalline structure selected from the group consisting of 6HSiC and 4HSiC.
7. An artificial diamond according to claim 6, characterized in that the colorless crystal of synthetic silicon carbide is genuine silicon carbide.
8. Treated gemstone of synthetic silicon carbide with polished facets, characterized in that it consists of one crystal of synthetic silicon carbide containing additive atoms at a concentration sufficient to produce a visually distinct color, while the facets are sufficiently ground to refract light in the precious stone .
9. A processed synthetic gemstone of silicon carbide according to claim 8, characterized in that it has a color, crystal structure and additive characteristics selected from the group (see Table 3 in the graphical part).
10. The processed synthetic gemstone of silicon carbide according to claim 8, characterized in that the additive atoms are present in the synthetic silicon carbide crystal in a concentration of 10 15 to 10 19 carrier atoms per cubic centimeter.
11. A processed synthetic gemstone of silicon carbide according to claim 9, characterized in that the additive atoms are present in the synthetic silicon carbide crystal in a concentration of 10 15 to 10 19 carrier atoms per cubic centimeter.
12. The processed synthetic gemstone of silicon carbide according to claim 8, characterized in that the synthetic silicon carbide has a crystalline structure from the group containing 6HSiC and 4HSiC.
13. Artificial diamond from a single crystal of colorless synthetic silicon carbide, characterized in that it has facets polished to a degree characteristic of processed diamonds.
14. An artificial diamond according to claim 13, characterized in that said facets therein are characteristic for diamond cutting.
15. An artificial diamond according to claim 14, characterized in that said cut is a round brilliant cut.
16. An artificial diamond according to claim 13, characterized in that the synthetic silicon carbide has a crystal structure selected from the group consisting of 6HSiC and 4HSiC.
17. An artificial diamond according to claim 16, characterized in that the colorless crystal of synthetic silicon carbide is genuine silicon carbide.
18. A process for producing a treated gemstone having a strength of about 8.5 to 9.25 on a Mosa scale, a density (SG) of about 3.2 and a refractive index of about 2.50 to 2.71, characterized in that it comprises the following steps : Growing a single silicon carbide crystal of one polytype of the required color, and cutting and polishing the silicon carbide crystal to a processed gem.
19. The method of claim 18, characterized in that it comprises the step of growing a single crystal of colorless silicon carbide.
20. The method of claim 19, characterized in that it comprises the step of growing a single silicon carbide crystal from a seed crystal in a sublimation system.
21. The method of claim 19, characterized in that it comprises the step of growing a single crystal as 6HSiC.
22. The method of claim 21, characterized in that it comprises the step of growing a single crystal as a genuine 6HSiC.
23. The method of claim 19, further comprising the step of growing a single crystal as 4HSiC.
24. The method of claim 23, further comprising the step of growing a single crystal as a genuine 4HSiC.
25. The method of claim 18, wherein the step of growing the silicon carbide crystal uses a selected additive to the crystal to obtain the desired color and shade of the crystal.
26. The method of claim 25, wherein the color of the processed gemstone, the crystal structure and the characteristics of the silicon carbide crystal providing additives providing a color are selected from the group: (a) blue, 6HSiC, with Al-additive; (B) magenta, 6HSiC, with an additive with a high Al content; (C) magenta, 24RSiC, with an N-additive; (D) green, 6HSiC, with N-additive; (E) yellow, 3CSiC, without additive; (E) yellow-green, 3CSiC, with N-additive; (G) red, 27RSiC, with N-additive; (H) light brown, 4HSiC, with an additive with a low concentration of N; (And) yellow-orange, 8HSiC, with an N-additive.
27. The method of claim 18, wherein the step of cutting and grinding includes cutting the silicon carbide crystal with diamonds.
28. The method of claim 27, characterized in that the faceting and grinding step includes grinding the facets with a gradual reduction in the size of the grinding grain.
29. The method of claim 18, characterized in that it comprises the step of cutting a grown single crystal immediately after growing into a plurality of uncut synthetic gemstones.
30. A process for producing processed gemstones from synthetic silicon carbide from a single silicon carbide crystal, characterized in that it comprises the following steps: cutting a single crystal of synthetic silicon carbide to obtain a plurality of uncut synthetic gemstones, and polishing and polishing each of the unpolished synthetic gems To the spent gem.
31. A process for producing a treated artificial diamond, characterized in that it comprises the following steps: growing a colorless single crystal of silicon carbide of one polytype in a crystal growth system protected from atoms of gaseous and vaporous impurities capable of imparting an undesirable color level to the stone and cutting and grinding Crystal silicon carbide to obtain a processed gemstone.
32. The method of claim 31, wherein the step of cutting and grinding involves cutting the silicon carbide crystal with diamonds.
33. The method of claim 31, wherein the steps of cutting and grinding include grinding the facets with a gradual reduction in the size of the grinding grain.
34. The method of claim 33, wherein the grinding step includes the use of a grinding wheel with a gradual reduction in the size of the grinding grain.
35. The method of claim 34, characterized in that it comprises the use of a grinding wheel rotating at a speed below 3000 rpm.
36. The method according to claim 35, characterized in that, at the stage of using the grinding wheel, its rotation speed is of the order of 300 rpm.
37. The method of claim 31, characterized in that it comprises a step of cutting the crystal immediately after growing into a plurality of uncut synthetic gemstones.
38. A process for producing a treated artificial diamond, characterized in that it comprises the following steps: growing a single crystal of colorless silicon carbide and shaping and shaping the facets of a silicon carbide crystal and grinding the facets until the optical characteristics of the treated diamond are obtained to thereby obtain the treated artificial diamond.
39. An artificial diamond obtained by the method according to claim 38.
40. The method of claim 38, wherein the fine grinding step is performed using an appropriate grinding grain of 0.5-1 μm.
41. Artificial diamond obtained by the method according to paragraph 40.
42. The method of claim 38, wherein shaping, size and grinding is performed with a gradual reduction in the size of the grinding grain.
43. A method for producing a treated gemstone from silicon carbide having a visually distinguishable color, comprising the steps of: growing a single crystal of semitransparent silicon carbide, adding a crystal optionally at the crystal growth stage by adding additive atoms capable of imparting a color and shade to the crystal and shaping And the dimensions of the silicon carbide crystal with facets and grinding the facets to achieve the optical characteristics of the processed gemstone to thereby obtain a faceted gemstone having a visually distinct color.
44. A processed gemstone made of silicon carbide obtained by the method of claim 43.
45. The method of claim 43, wherein the fine grinding step is performed using a suitable grinding grain having a size of 0.5-1 μm.
46. Treated gemstone obtained by the method of claim 45.
47. The method of claim 43, wherein the additive atoms are added at concentrations of from 10 15 to 10 19 carrier atoms per cubic centimeter.
48. A method for producing a treated artificial diamond, characterized in that it comprises the following steps: cutting and grinding an untreated gemstone obtained from a single crystal of colorless synthetic silicon carbide to produce a treated artificial diamond having a shape and grinding characteristics allowing the gemstone to refract light.
49. The method of claim 48, wherein the treated artificial diamond has a round brilliant cut.
50. The method of claim 48, wherein the synthetic silicon carbide has a crystal structure selected from the group consisting of 6HSiC and 4HSiC.
print version
Date of publication 03.01.2007gg
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