Blue silicon carbide gemstone and preparation method thereof

Abstract

The invention provides a blue silicon carbide gemstone and a preparation method thereof, and particularly relates to the field of crystal growth. The preparation method of the blue silicon carbide gemstone comprises the following steps: providing a first silicon carbide raw material and a second silicon carbide raw material, wherein the first silicon carbide raw material comprises polyaluminocarbosilane; sequentially putting the first silicon carbide raw material, the second silicon carbide raw material and silicon carbide particles into a crucible, wherein the volumes of the first silicon carbide raw material, the second silicon carbide raw material and the silicon carbide particles are sequentially increased; and carrying out crystal growth by adopting a physical vapor transport method to obtain the blue silicon carbide gemstone. According to the preparation method provided by the invention, a ceramic precursor polyaluminocarbosilane is introduced as a silicon carbide raw material, and in the growth process of the silicon carbide gemstone, the polyaluminocarbosilane is decomposed to release an aluminum element, so that the situation that the doping concentration of the doping element is insufficient in the later stage due to relatively high doping concentration in the early stage is avoided, and the obtained gemstone is uniform in color, low in microtube defect and high in quality. And the crystal quality is high.

Description

Technical Field

[0001] The present invention relates to the technical field of crystal growth, in particular to a blue silicon carbide gemstone and a preparation method thereof. Background Art

[0002] Silicon carbide (SiC), an emerging synthetic gem material, exhibits significant comprehensive performance advantages in the field of gemology. Its Mohs hardness of 9.25 is second only to diamond and significantly surpasses traditional corundum gemstones such as ruby ​​and sapphire. This provides exceptional scratch and abrasion resistance, and allows it to maintain its surface luster over time. In terms of optical properties, SiC possesses a high refractive index (2.65-2.69), exhibiting intense adamantine luster and brilliance. Its dispersion value is approximately 2.4 times that of diamond, producing a remarkable rainbow fire effect under illumination, resulting in a stunning visual effect. Chemical stability is also a core advantage, with SiC exhibiting strong resistance to high temperatures, acid and alkali corrosion, ultraviolet light, and everyday chemical reagents, ensuring its long-term durability in wear environments. Furthermore, the cost of synthetic SiC gemstones is significantly lower than that of natural diamonds, while their appearance is highly similar, making them a cost-effective alternative to diamonds. By doping with different elements (such as vanadium, nitrogen, aluminum, etc.), rich color control can be achieved - for example, doping with vanadium can produce champagne color, and doping with nitrogen can produce emerald green, meeting the market's diverse demand for personalized colors.

[0003] Color characteristics (such as hue, saturation, and distribution uniformity) are core evaluation indicators in gemstone valuation. Currently, physical vapor transport (PVT) is the mainstream technology for synthesizing silicon carbide gemstones. However, this method suffers from a critical bottleneck: the uncontrollable release rate of the dopant element, which leads to severely uneven color distribution. Specifically, during the initial growth phase, the dopant release concentration is high, resulting in a darker color near the seed crystal. As growth progresses, the dopant is gradually depleted, and the color at the edge of the crystal becomes significantly lighter, even nearing colorlessness, forming a distinct color gradient. This unevenness significantly reduces the gemstone's overall quality and commercial value, becoming a key technical obstacle to industrialization.

[0004] Therefore, how to effectively solve the problem of color unevenness in the process of growing silicon carbide gemstones using the PVT method is a technical problem that needs to be solved urgently. Summary of the Invention

[0005] The present invention provides a blue silicon carbide gemstone and a preparation method thereof, so as to solve the technical problem of uneven color of silicon carbide gemstones.

[0006] The present invention provides a method for preparing a blue silicon carbide gemstone, comprising the following steps: Providing a first silicon carbide raw material, a second silicon carbide raw material, and silicon carbide particles, wherein the first silicon carbide raw material includes polyaluminocarbosilane; placing the first silicon carbide raw material, the second silicon carbide raw material, and the silicon carbide particles in a crucible in sequence, wherein the volumes of the first silicon carbide raw material, the second silicon carbide raw material, and the silicon carbide particles increase in sequence; The physical vapor transport method was used for crystal growth to obtain blue silicon carbide gemstone.

[0007] In one embodiment of the present invention, the preparation method of the polyaluminocarbosilane is as follows: The aluminum-containing substance and polycarbosilane are mixed evenly and dissolved in an organic solvent; The mixed solution of the aluminum-containing substance and the polycarbosilane is heated to 100-300° C. under the protection of an inert atmosphere, kept warm for 10-60 hours, and then cooled to room temperature to obtain the polyaluminocarbosilane.

[0008] In one embodiment of the present invention, the weight of the aluminum-containing substance is 1-50% of the weight of the polycarbosilane.

[0009] In one embodiment of the present invention, the aluminum-containing substance includes any one or more of aluminum acetylacetonate, triethylaluminum, diethylaluminum chloride, diisobutylaluminum hydride, aluminoxane, aluminum porphyrin complex, tris(pentafluorophenyl)aluminum, and aluminum nitrogen heterocyclic carbene complex.

[0010] In one embodiment of the present invention, the organic solvent is any one of toluene, xylene, tetrahydrofuran, n-propanol, and acetone.

[0011] In one embodiment of the present invention, the volume of the first silicon carbide raw material is 1-100 mm 3 The volume of the second silicon carbide raw material is 100~300mm 3 The volume of the silicon carbide particles is 500~1000mm 3 .

[0012] In one embodiment of the present invention, the weight ratio of the first silicon carbide raw material, the second silicon carbide raw material, and the silicon carbide particles is (1-2):(1.5-2.5):(2.5-4).

[0013] In one embodiment of the present invention, the first silicon carbide raw material further includes any one of a mixture of carbon powder and silicon powder, polycarbosilane, and silicon carbide powder.

[0014] In one embodiment of the present invention, when the first silicon carbide raw material is a mixture of the polyaluminocarbosilane and other powders, the weight of the polyaluminocarbosilane is 10% to 50% of the total mass of the first silicon carbide raw material.

[0015] The present invention also provides a blue silicon carbide gemstone, which is prepared by the above-mentioned preparation method.

[0016] The present invention provides beneficial effects: The method for preparing blue silicon carbide gemstones, by introducing the ceramic precursor polyaluminocarbosilane as a silicon carbide raw material, effectively controls the binding of aluminum to the silicon carbide source. This avoids the problems of color stratification and high crystal defect density that can occur during the initial growth phase when synthesizing blue silicon carbide directly by adding aluminum oxide or aluminum carbide to the silicon carbide source. Furthermore, compared to silicon carbide, the hydrogen produced by the decomposition of polyaluminocarbosilane during heating can purify the growth atmosphere, significantly reducing the impact of impurities (such as nitrogen) on the gemstone crystal color. By arranging the source materials in layers, the large silicon carbide particles at the top physically and chemically filter the decomposition products of the powder at the bottom, ultimately producing a uniform and vibrant blue silicon carbide gemstone. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings are incorporated into and constitute a part of the specification, illustrate embodiments consistent with the present application, and together with the specification, are used to explain the principles of the present application. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be derived from these drawings without inventive effort.

[0018] In the attached figure: Figure 1 This is a flow chart of a method for preparing a blue silicon carbide gemstone provided in one embodiment of the present invention; Figure 2 A flow chart for preparing polyaluminocarbosilane provided in one embodiment of the present invention; Figure 3 This is a schematic structural diagram of silicon carbide material charging provided in one embodiment of the present invention; Figure 4 A schematic structural diagram of a crucible body provided in one embodiment of the present invention; Figure 5 A schematic structural diagram of a seed crystal cover provided in one embodiment of the present invention; Figure 6 This is a schematic structural diagram of a graphite ring provided in one embodiment of the present invention; Figure 7 This is a schematic structural diagram of a porous ring in one embodiment of the present invention; Figure 8 A schematic diagram of the structure of a graphite plate provided in one embodiment of the present invention; Figure 9 This is a physical photo of a blue silicon carbide gemstone provided in one embodiment of the present invention; Figure 10This is a slice photo of the blue silicon carbide gemstone prepared in Example 1 of the present invention; Figure 11 This is a slice photo of the blue silicon carbide gemstone prepared in Example 2 of the present invention; Figure 12 This is a slice photo of the blue silicon carbide gemstone prepared in Example 3 of the present invention; Figure 13 This is a slice photo of the blue silicon carbide gemstone prepared in Comparative Example 1.

[0019] The reference numerals are as follows: 100, seed crystal cover; 101, seed crystal cover thread; 102, seed crystal; 200, graphite ring; 201, step; 202, graphite ring body; 300, crucible body; 301, crucible thread; 302, channel; 303, step; 400, porous ring; 401, pore; 500, graphite plate; 501, channel; 600, silicon carbide particles; 700, second silicon carbide raw material; 800, first silicon carbide raw material. DETAILED DESCRIPTION

[0020] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments. The details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention. The following embodiments and features therein may be combined with one another without conflict.

[0021] It should be noted that the illustrations provided in the following embodiments are merely schematic illustrations of the basic concept of the present invention. The drawings only show components related to the present invention and are not drawn according to the number, shape, and size of components in actual implementation. In actual implementation, the type, quantity, and proportion of each component may be changed arbitrarily, and the component layout may also be more complex.

[0022] In the following description, numerous details are discussed to provide a more thorough explanation of the embodiments of the present invention. However, it will be apparent to those skilled in the art that the embodiments of the present invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring the embodiments of the present invention.

[0023] See also Figure 1 The present invention provides a method for preparing blue silicon carbide gemstone, which comprises the following steps: S1. Providing a first silicon carbide raw material, a second silicon carbide raw material, and silicon carbide particles, wherein the first silicon carbide raw material includes polyaluminocarbosilane; S2, placing a first silicon carbide raw material, a second silicon carbide raw material, and silicon carbide particles in a crucible in sequence, with the volumes of the first silicon carbide raw material, the second silicon carbide raw material, and the silicon carbide particles increasing in sequence; S3. Use physical vapor transport method to grow crystals to obtain blue silicon carbide gemstones.

[0024] In step S1, in one embodiment, the first silicon carbide raw material further includes any one of a mixture of carbon powder and silicon powder, polycarbosilane, and silicon carbide powder. For example, the first silicon carbide powder can be polyaluminocarbosilane, a mixture of polyaluminocarbosilane and polycarbosilane, a mixture of polyaluminocarbosilane and silicon carbide powder, or a mixture of polyaluminocarbosilane, carbon powder, and silicon powder. When the first powder is a mixture of polyaluminocarbosilane and other powders, the weight of the polyaluminocarbosilane is 10% to 50% of the total mass of the first silicon carbide raw material, for example, 10%, 30%, or 50%.

[0025] See also Figure 2 In one embodiment, the preparation method of polyaluminocarbosilane is as follows: S11, uniformly mixing the aluminum-containing substance and polycarbosilane, and dissolving them in an organic solvent; S12. The mixed solution of the aluminum-containing substance and polycarbosilane is heated to 100-300° C. under an inert atmosphere, kept warm for 10-60 hours, and then cooled to room temperature to obtain polyaluminocarbosilane.

[0026] In step S11, the aluminum-containing substance is subjected to a hydrosilylation reaction to graft aluminum elements onto the polycarbosilane structure, and is used to dope aluminum elements during the crystal growth process to obtain blue silicon carbide gemstones. The weight of the aluminum-containing substance is 1 to 50% of the weight of the polycarbosilane. For example, the weight of the aluminum-containing substance is 1%, 10%, 20%, 30% or 50% of the weight of the polycarbosilane. In one embodiment, the aluminum-containing substance includes any one or more of aluminum acetylacetonate, triethylaluminum, diethylaluminum chloride, diisobutylaluminum hydride, aluminoxane, aluminum porphyrin complex, tris(pentafluorophenyl)aluminum, and aluminum nitrogen heterocyclic carbene complex. That is, the aluminum-containing substance can be selected from any one of the materials listed above, such as aluminum acetylacetonate, or triethylaluminum, or aluminoxane, or a combination of two or more of the materials listed above mixed in any proportion, such as a combination of aluminum acetylacetonate and triethylaluminum, or a combination of triethylaluminum chloride, aluminoxane, and aluminum porphyrin complex. In other embodiments, the aluminum-containing material may also be selected from materials not listed above that can provide aluminum doping elements to the silicon carbide material. In some embodiments, the organic solvent is any one of toluene, xylene, tetrahydrofuran, n-propanol, and acetone. In other embodiments, the organic solvent may be any other common solvent in the art that can dissolve the aluminum-containing material and the polycarbosilane.

[0027] In step S12, in one embodiment, the inert atmosphere is, for example, argon. In other embodiments, the inert atmosphere may also be other inert gases, as long as they do not participate in the reaction and do not introduce impurities. Polyaluminocarbosilane can be prepared using a heating reaction apparatus commonly used in the art, such as a tube furnace, an oven, or a muffle furnace.

[0028] In step S2, a first silicon carbide raw material, a second silicon carbide raw material, and silicon carbide particles are placed in order from the bottom of the crucible upward along the axial direction of the crucible. The volume of the second silicon carbide raw material is larger than that of the first silicon carbide raw material, and the volume of the silicon carbide particles is larger than that of the second silicon carbide raw material. For example, the volume of the first silicon carbide raw material is 1 to 100 mm 3 , for example 1mm 3 , 10mm 3 , 50mm 3 or 100mm 3 etc.; the volume of the second silicon carbide raw material is 100~300mm 3 , for example 100mm 3 , 200mm 3 or 300mm 3 etc.; the volume of silicon carbide particles is 500~1000mm 3 , for example 500mm 3 , 800mm 3 or 1000mm 3 The weight ratio of the first silicon carbide raw material, the second silicon carbide raw material, and the silicon carbide particles is (1-2):(1.5-2.5):(2.5-4).

[0029] Figures 3 to 8 This is the graphite piece and charging structure for crystal growth in this application. The crucible in this step is the graphite crucible structure commonly used in growing silicon carbide crystals using the PVT method. Figure 3 As shown, as an example, the crucible includes a seed crystal cover 100, a graphite ring 200, a crucible body 300, a porous ring 400 and a graphite plate 500. Figure 4 As shown, the crucible body 300 is the main body for holding silicon carbide raw materials, and can be any three-dimensional structure with a cavity, such as a cylindrical structure. The top of the cavity of the crucible body 300 is provided with a crucible thread 301, a channel 302 and a step 303. Figure 5 As shown, the outer wall of the seed crystal cover 100 is provided with a seed crystal cover thread 101 that matches the crucible thread 301. The seed crystal cover 100 and the crucible body 300 are connected and fixed by the seed crystal cover thread 101 and the crucible thread 301. The side of the seed crystal cover 100 facing the crucible body 300 is used to bond the seed crystal 102. Figure 6 As shown, the graphite ring 200 includes an upper step 201 and a graphite ring body 202. Figure 7As shown, the porous ring 400 is provided with a plurality of pores 401. Figure 8 As shown, a plurality of channels 501 are provided on the graphite plate 500 , and the plurality of channels 501 penetrate along the thickness direction of the graphite plate 500 .

[0030] See also Figure 3 As shown, during loading, the first silicon carbide raw material 800, the second silicon carbide raw material 700 and the silicon carbide particles 600 are placed in sequence from the bottom of the crucible body 300 upward along the axial direction of the crucible body 300, the graphite plate 500 is placed on the step 303 of the crucible body 300, and the graphite plate 500 is located above the silicon carbide particles 600, the porous ring 400 and the graphite ring 200 are placed in sequence above the graphite plate 500, and the porous ring 400 corresponds to the channel 302 of the crucible body 300, and the seed crystal cover 100 is fixed to the crucible body 300 by screw threads.

[0031] Step S3 places the crucible after loading into a crystal growth furnace, and grows silicon carbide crystals using the PVT method according to conventional processes. After the growth is completed, a blue silicon carbide gemstone is obtained. For example, for example, first, in an argon atmosphere, the temperature in the furnace is raised to 800°C at a heating rate of 10-50°C, for example, 30°C, and maintained at this temperature for 1-10 hours; then, the temperature is slowly raised to 2200-2300°C, for example, 2260°C, at a heating rate of 1-10°C, for example, 5°C. During this process, the pressure is reduced from 300-500mbar, for example, 300mbar, to a growth pressure of 1-5mbar, for example, 3mbar, and then grown in a stable pressure section for 100-150h, for example, 120h.

[0032] The core innovation of the present method for preparing blue silicon carbide gemstones lies in the introduction of polyaluminocarbosilane, an aluminum-containing ceramic precursor, as a blue control dopant. Furthermore, by constructing a layered material, the volatile cracking products of the lower source material are filtered. During the high-temperature growth process, the silicon carbide raw material sublimates sequentially. By regulating the interlayer ratio and temperature field distribution, the concentration of vapor-phase aluminum transferred to the seed crystal interface remains stable at each growth stage, thereby achieving uniform axial aluminum doping of the crystal. Furthermore, the hydrogen released during the cracking of polyaluminocarbosilane purifies the growth environment, reducing the impact of impurities (such as nitrogen) on the crystal color, ultimately producing a blue silicon carbide gemstone with a consistent hue.

[0033] The preparation method described in this application is not only applicable to blue silicon carbide gemstones. By grafting other doping elements onto polycarbosilane, it can also be used to prepare silicon carbide gemstones of other colors (such as nitrogen for yellow gemstones and vanadium / chromium composite doping for red gemstones). It is compatible with the homogenized preparation of multi-color silicon carbide gemstones. Compared to traditional single-component doping processes, the introduction of a highly structurally designable polymer precursor as a dopant effectively solves the color gradient problem caused by unbalanced volatilization dynamics, providing a key technical path for the industrialization of high-quality synthetic silicon carbide gemstones.

[0034] See also Figure 9 The present invention also provides a blue silicon carbide gemstone produced using the aforementioned preparation method. Because the aforementioned preparation method mitigates the release of aluminum, the doping element, from the synthetic blue silicon carbide gemstone, and because hydrogen generated by the decomposition of polyaluminocarbosilane can purify impurity elements in the growth atmosphere, the resulting blue silicon carbide gemstone exhibits uniform and pure color.

[0035] The technical scheme of the present invention is described in detail below through several specific examples and comparative examples. Unless otherwise stated, the raw materials and reagents used in the following examples are all commercially available commodities, or can be prepared by conventional methods in the art, and the instruments used in the examples are all commercially available. The described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention.

[0036] In the embodiment of the present application, the volume of the first silicon carbide raw material at the bottom layer is 1~100mm 3 The volume of the second silicon carbide raw material in the middle is 100~300mm 3 , the volume of the upper silicon carbide particles is 500~1000mm 3 .

[0037] Example 1 The preparation method of the blue silicon carbide gemstone in this embodiment is as follows: Preparation of polyaluminocarbosilane: Aluminum acetylacetonate and polycarbosilane were uniformly mixed and completely dissolved in tetrahydrofuran. The mixed solution of aluminum acetylacetonate and polycarbosilane was placed in an oven, evacuated, and then purged with argon to atmospheric pressure. The temperature was raised to 260°C and maintained for 50 hours. The oven was cooled to room temperature, evacuated, and then purged with argon to atmospheric pressure before opening the oven to obtain a yellow resinous polyaluminocarbosilane. The weight of aluminum acetylacetonate was 10% of the weight of the polycarbosilane.

[0038] Filling: Place 2kg of polyaluminocarbosilane at the bottom of the crucible, followed by 2kg of polycarbosilane and 3kg of silicon carbide particles. Place a graphite plate on the step of the crucible, and place a porous ring on top of it, with the bottom surface of the porous ring in contact with the graphite plate. Place another graphite ring and a seed crystal cap with a seed crystal bonded to it on the porous ring. The seed crystal cap is connected to the crucible body via threads.

[0039] Silicon carbide growth: Place the crucible in the crystal growth furnace chamber, evacuate to <1Pa, then heat to 800℃ at a rate of 10℃ / min, keep constant temperature for 5h, fill with argon to 300mbar, heat to 2200℃ at a rate of 5℃ / min, and then heat to 2260℃ at a rate of 2℃ / min. During this period, reduce the pressure to 1mbar at a linear speed. After keeping constant temperature for 120h, cool to room temperature with the furnace to obtain a blue silicon carbide gemstone.

[0040] See also Figure 10 The blue silicon carbide gemstone prepared in this embodiment was sliced ​​and observed to have uniform color.

[0041] Example 2 The preparation method of the blue silicon carbide gemstone in this embodiment is as follows: Preparation of polyaluminocarbosilane: Triethylaluminum and polycarbosilane are uniformly mixed and completely dissolved in xylene. The mixed solution of triethylaluminum and polycarbosilane is placed in an oven, evacuated, and then purged with argon to atmospheric pressure. The temperature is then raised to 280°C and maintained for 30 hours. The oven is cooled to room temperature, evacuated, and then purged with argon to atmospheric pressure before being opened to obtain a resinous polyaluminocarbosilane. The weight of triethylaluminum is 30% of the weight of the polycarbosilane.

[0042] Filling: Mix 1.2 kg of polyaluminocarbosilane and 0.8 kg of silicon carbide powder and place them evenly at the bottom of the crucible. Then, add 1.8 kg of polycarbosilane and 3.2 kg of silicon carbide granules. Place a graphite plate on the step of the crucible, and a porous ring on top, ensuring the bottom surface of the porous ring contacts the graphite plate. Then, place another graphite ring and a seed crystal cap with a seed crystal bonded to it on the porous ring. The seed crystal cap is connected to the crucible via threads.

[0043] Growth of silicon carbide gemstone: Place the crucible in the crystal growth furnace chamber, evacuate to <1Pa, then heat to 900℃ at a rate of 15℃ / min, keep constant temperature for 3h, fill with argon to 500mbar, heat to 2200℃ at a rate of 10℃ / min, and then heat to 2280℃ at a rate of 2℃ / min. During this period, reduce the pressure to 3mbar at a linear speed. After keeping constant temperature for 150h, cool to room temperature with the furnace to obtain a blue silicon carbide gemstone.

[0044] See also Figure 11The blue silicon carbide gemstone prepared in this embodiment was sliced ​​and observed to have uniform color.

[0045] Example 3 The preparation method of the blue silicon carbide gemstone in this embodiment is as follows: Preparation of polyaluminocarbosilane: Diisobutylaluminum hydride and polycarbosilane are uniformly mixed and completely dissolved in n-propanol. The mixed solution of diisobutylaluminum hydride and polycarbosilane is placed in an oven, evacuated, and then purged with argon to atmospheric pressure. The temperature is then raised to 100°C and maintained for 60 hours. The oven is cooled to room temperature, evacuated, and then purged with argon to atmospheric pressure before being opened to obtain a resinous polyaluminocarbosilane. The weight of triethylaluminum is 50% of the weight of the polycarbosilane.

[0046] Filling: Mix 0.2 kg of polyaluminocarbosilane and 1.8 kg of polycarbosilane and place them evenly at the bottom of the crucible. Then, add 1.5 kg of polycarbosilane and 4 kg of silicon carbide particles. Place a graphite plate on the crucible step, and a porous ring on top, ensuring the bottom surface of the porous ring contacts the graphite plate. Then, place another graphite ring and a seed crystal cap with a seed crystal bonded to it on the porous ring. The seed crystal cap is connected to the crucible via threads.

[0047] Growth of silicon carbide gemstone: Place the crucible in the crystal growth furnace chamber, evacuate to <1Pa, then heat to 900℃ at a rate of 15℃ / min, keep constant temperature for 3h, fill with argon to 500mbar, heat to 2200℃ at a rate of 10℃ / min, and then heat to 2280℃ at a rate of 2℃ / min. During this period, reduce the pressure to 3mbar at a linear speed. After keeping constant temperature for 150h, cool to room temperature with the furnace to obtain a blue silicon carbide gemstone.

[0048] See also Figure 12 The blue silicon carbide gemstone prepared in this embodiment was sliced ​​and observed to have uniform color.

[0049] Comparative Example 1 The preparation method of the blue silicon carbide gemstone in this embodiment is as follows: Filler: 7kg volume of 1~100mm 3 Mix 1g of silicon carbide material and 2g of aluminum oxide evenly and place them in a crucible.

[0050] Silicon carbide growth: The growth conditions of the silicon carbide gemstone in this comparative example are the same as those in Example 1.

[0051] See also Figure 13 The blue silicon carbide gemstone prepared in Comparative Example 1 was sliced ​​and observed to find that the color of the blue silicon carbide gemstone was dark at first and then light, with obvious stratification in the center and uneven color.

[0052] Comparing Examples 1-3 with Comparative Example 1 reveals that the introduction of polyaluminocarbosilane as a silicon carbide raw material decomposes and releases aluminum during the growth of blue silicon carbide gemstones. This controlled release of aluminum prevents insufficient doping concentrations later due to high initial doping concentrations. Furthermore, the hydrogen generated by the decomposition of polyaluminocarbosilane during the heating process purifies the growth atmosphere, significantly reducing the impact of impurities (such as nitrogen) on the gemstone crystal color.

[0053] The hydrogen generated by polymer cracking purifies impurities in the growth atmosphere, further purifying the crystal's color. Furthermore, during loading, the first and second SiC raw materials, along with the SiC particles, are layered. The large SiC particles in the upper layer physically and chemically filter the cracking products of the SiC raw material at the bottom, ultimately yielding a uniform and vibrant blue SiC gemstone.

[0054] In summary, the present invention provides a blue silicon carbide gemstone and a preparation method thereof. By introducing a silicon carbide precursor polymer and grafting aluminum elements into its structure through a silicon-hydrogen addition reaction, it is used as a dopant. The loading structure is placed in layers, and the cracking products are further filtered to finally obtain a blue silicon carbide gemstone with uniform color, low microtube defects and high crystallization quality.

[0055] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A method for preparing blue silicon carbide gemstone, characterized in that: The following steps are involved: Providing a first silicon carbide raw material, a second silicon carbide raw material, and silicon carbide particles, wherein the first silicon carbide raw material includes polyaluminocarbosilane; placing the first silicon carbide raw material, the second silicon carbide raw material, and the silicon carbide particles in a crucible in sequence, wherein the volumes of the first silicon carbide raw material, the second silicon carbide raw material, and the silicon carbide particles increase in sequence; The physical vapor transport method was used for crystal growth to obtain blue silicon carbide gemstone.

2. The preparation method according to claim 1, characterized in that The preparation method of the polyaluminocarbosilane is as follows: The aluminum-containing substance and polycarbosilane are mixed evenly and dissolved in an organic solvent; The mixed solution of the aluminum-containing substance and the polycarbosilane is heated to 100-300° C. under the protection of an inert atmosphere, kept warm for 10-60 hours, and then cooled to room temperature to obtain the polyaluminocarbosilane.

3. The preparation method according to claim 2, characterized in that The weight of the aluminum-containing substance is 1-50% of the weight of the polycarbosilane.

4. The preparation method according to claim 2, characterized in that The aluminum-containing substance includes any one or more of aluminum acetylacetonate, triethylaluminum, diethylaluminum chloride, diisobutylaluminum hydride, aluminoxane, aluminum porphyrin complex, tris(pentafluorophenyl)aluminum, and aluminum nitrogen heterocyclic carbene complex.

5. The preparation method according to claim 2, characterized in that The organic solvent is any one of toluene, xylene, tetrahydrofuran, n-propanol and acetone.

6. The preparation method according to claim 1, characterized in that The volume of the first silicon carbide raw material is 1-100 mm 3 The volume of the second silicon carbide raw material is 100~300mm 3 The volume of the silicon carbide particles is 500~1000mm 3 .

7. The preparation method according to claim 1, characterized in that The weight ratio of the first silicon carbide raw material, the second silicon carbide raw material and the silicon carbide particles is (1-2):(1.5-2.5):(2.5-4).

8. The preparation method according to claim 1, characterized in that The first silicon carbide raw material further includes any one of a mixture of carbon powder and silicon powder, polycarbosilane, and silicon carbide powder.

9. The preparation method according to claim 8, characterized in that When the first silicon carbide raw material is a mixture of the polyaluminocarbosilane and other powders, the weight of the polyaluminocarbosilane is 10% to 50% of the total mass of the first silicon carbide raw material.

10. A blue silicon carbide gemstone, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 9.

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