A low-viscosity, low-moisture boron oxide, its preparation method and application

Abstract

This invention relates to the field of material preparation, specifically to a low-viscosity, low-moisture boron oxide, its preparation method, and its applications. The boron oxide preparation method provided by this invention requires the addition of sodium aluminofluorate. Adding a certain amount of sodium aluminofluorate during the boron oxide preparation process not only reduces the introduction of impurities but also effectively lowers the viscosity of the resulting boron oxide, giving it a low viscosity that meets the requirements of a liquid sealant for gallium antimonide crystals. The preparation method provided by this invention is simple, and its advantages include low moisture content, low viscosity, low impurities, and high transparency in the prepared sodium aluminofluorate-doped boron oxide. Furthermore, it can be recast into different shapes and sizes to cover materials of varying areas, meeting the requirements of a liquid sealant for gallium antimonide crystals. Experiments show that this invention prepared transparent boron oxide with 280 ppm moisture content, which, when used as a liquid sealant in the preparation of gallium antimonide, successfully yielded single crystals.

Description

Technical Field

[0001] This invention relates to the field of material preparation, specifically to a low-viscosity, low-moisture boron oxide, its preparation method, and its applications. Background Technology

[0002] Gallium antimonide (GaS) is commonly used as a substrate material and has a wide range of applications in industries such as infrared detectors, lasers, light-emitting diodes (LEDs), optical communications, and solar cells. The growth of GaS single crystals commonly uses the liquid-sealed Czochralski (LEC) method. This method requires covering the surface of the melt in a conventional Czochralski crucible with a liquid phase layer to prevent the volatilization of antimony at high temperatures. Boron oxide is commonly used as a liquid sealant in the semi-crystalline industry to prevent the loss of volatile components in the crystal. Its low moisture content effectively avoids the introduction of moisture, which would lead to an increase in melt oxides.

[0003] Boron oxide used on gallium antimonide has unique requirements. It needs not only sufficiently low moisture content and transparency but also low viscosity; otherwise, it will lead to crystal pulling failure during subsequent use in a single crystal furnace. Chinese patent CN108622912A discloses a high-temperature covering agent-grade boron oxide. This production method only addresses the preparation of conventional boron oxide. While it can produce boron oxide with low moisture content, it cannot solve the viscosity problem. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a low-viscosity, low-moisture boron oxide, its preparation method and application. The preparation method provided by the present invention can prepare boron oxide with not only low moisture content but also low viscosity, which can meet the various requirements of liquid sealant for gallium antimonide crystals.

[0005] This invention provides a method for preparing low-viscosity, low-moisture boron oxide, comprising the following steps:

[0006] S1) The molten boron oxide is dehydrated by heating once;

[0007] S2) The material obtained in step S1) and sodium aluminofluoroate are calcined; the amount of sodium aluminofluoroate added accounts for 3.2 mol% to 3.8 mol% of the total amount of sodium aluminofluoroate and boron oxide in step S1);

[0008] S3) The material obtained in step S2) is heated and dehydrated a second time to obtain low-viscosity, low-moisture boron oxide.

[0009] The boron oxide preparation method provided by this invention requires the addition of sodium aluminofluoride in step S2), wherein the amount of sodium aluminofluoride added accounts for 3.2 mol% to 3.8 mol% of the total amount of sodium aluminofluoride and boron oxide in step S1). The inventors of this application have creatively discovered that adding a certain amount of sodium aluminofluoride during the preparation of boron oxide not only reduces the introduction of impurities but also effectively reduces the viscosity of the prepared boron oxide, giving it a low viscosity that meets the requirements of liquid sealants for gallium antimonide crystals.

[0010] This invention first dehydrates molten boron oxide through heating. Specifically, this dehydration process involves heating the molten boron oxide to 850-900°C at a rate of 60-80°C / h and calcining it for 1-2 hours. More specifically, the invention involves melting boron oxide in a crucible to obtain molten boron oxide; then, the molten boron oxide is further dehydrated through heating in the crucible; the melting temperature is 700-800°C, and the melting time is 1-2 hours; the molten boron oxide is in a transparent molten state. The boron oxide used in this invention has a purity of 5N and is anhydrous boron oxide with a moisture content ≤300ppm. This invention directly uses anhydrous boron oxide without the need for boric acid. The anhydrous boron oxide used in this invention has already undergone dehydration treatment, resulting in even less moisture. If boric acid were used, it would introduce some moisture. The crucible described in this invention is made of platinum or high-purity quartz, which can effectively avoid the introduction of impurities. Platinum is superior, and it can be reused, saving costs.

[0011] This invention involves heating and dehydrating molten boron oxide once, then calcining the resulting material with sodium aluminofluoroate. The amount of sodium aluminofluoroate added is 3.2 mol% to 3.8 mol% of the total amount of sodium aluminofluoroate and boron oxide in step S1). Specifically, after heating and dehydrating molten boron oxide once, sodium aluminofluoroate is added to the resulting material within 30 seconds for calcination. In some embodiments of this invention, after heating and dehydrating molten boron oxide once, a certain amount of sodium aluminofluoroate is weighed according to the weight of the added boron oxide. The furnace door is quickly opened, and the sodium aluminofluoroate powder is poured into a crucible containing the material obtained after heating and dehydration using a clamp. The entire process is controlled within 30 seconds. The calcination temperature of this invention is 850–900°C; the calcination time is 1–2 hours. The sodium aluminofluoroate of this invention has a purity of 3N and is white in color. Sodium aluminofluoroate has different color forms. This invention selects white sodium aluminofluoroate with a purity of 3N, which can reduce the introduction of impurities and ensure the transparency of boron oxide.

[0012] This invention involves calcining the material obtained after a first heating and dehydration process with sodium aluminofluoroate, followed by a second heating and dehydration of the resulting material. Specifically, the second heating and dehydration of the material obtained after calcination in step S2) involves calcining the material at 1000–1100°C for 3–6 hours. More specifically, the second heating and dehydration of the material obtained after calcination in step S2) involves calcining the material at 1000–1100°C for 1–2 hours at a pressure below 20 Pa, followed by holding at a pressure below 5 Pa for 2–4 hours. In some embodiments of the present invention, after the material obtained from the initial heating and dehydration is mixed with sodium aluminofluoroate and calcined, the vacuum switch is opened, the valve is turned to 1 / 2, and the vacuum degree is reduced to below 20 Pa. The temperature of the reaction system is raised by 150-200°C to 1000-1100°C and held for 1-2 hours. Then, all valves are opened, the temperature is kept constant, the vacuum degree is reduced to 5 Pa, and held for 2-4 hours until no bubbles are observed in the melt. The present invention raises the temperature of the reaction system by 150-200°C, so that the material obtained after calcination in step S2) is calcined at 1000-1100°C to ensure the complete melting of sodium aluminofluoroate. Holding the temperature below 5 Pa for 2-4 hours ensures complete melting and mixing of the melt.

[0013] This invention further includes casting the material obtained in step S2) after secondary heating and dehydration. Specifically, the material obtained in step S2) is removed under a protective gas atmosphere at positive pressure and cast into a mold. In some embodiments of this invention, after secondary heating and dehydration of the material obtained in step S2), nitrogen gas is introduced into the reaction system to positive pressure, and the crucible containing the material obtained in step S2) is removed within 10-20 minutes and cast into a mold. The protective gas used in this invention is selected from high-purity protective gases with a purity of 7N, which can effectively prevent the introduction of moisture and impurities by nitrogen gas; the protective gas is selected from nitrogen, helium, neon, or xenon, preferably nitrogen. In some embodiments of this invention, the protective gas is selected from high-purity nitrogen with a purity of 7N.

[0014] This invention preferably involves casting the material, obtained through secondary heating and dehydration, into a mold made of smooth 316 stainless steel. The reason for choosing a smooth 316 stainless steel mold, rather than a conventional platinum crucible, is that after adding sodium aluminofluorate, boron oxide cannot be demolded in platinum, making it impossible to remove the solidified boron oxide. Using a 316 stainless steel mold solves the problem of difficult demolding with platinum crucibles. The mold of this invention can be customized as needed. By customizing different molds, boron oxide can be recast into different sizes and shapes as required, covering materials of different areas. In particular, the customization cost of 316 stainless steel molds is far lower than that of traditional platinum crucibles.

[0015] This invention involves casting the material obtained through secondary heating and dehydration into a mold, followed by demolding and packaging the cast material. Specifically, the cast material is cooled for 1-3 hours before demolding. In some embodiments of this invention, the cast material is transferred to a glove box for cooling for 1-3 hours, and then the boron oxide is demolded inside the glove box and vacuum-sealed in an aluminum foil bag. The reason for transferring the cast material to a glove box for cooling for 1-3 hours before demolding is that boron oxide expands after the addition of sodium aluminofluoride, potentially causing it to burst. Demolding after it has stabilized and solidified is safer.

[0016] This invention provides a low-viscosity, low-moisture boron oxide prepared according to the above-described method. This invention also provides an application of the low-viscosity, low-moisture boron oxide prepared by the above-described method as a liquid encapsulant for gallium antimonide crystals. The low-viscosity, low-moisture boron oxide provided by this invention has high transparency and low moisture content (below 300 ppm). More importantly, its low viscosity allows it to meet all the requirements for gallium antimonide crystal liquid encapsulants, preventing crystal pulling failures.

[0017] This invention provides a low-viscosity, low-moisture boron oxide, its preparation method, and its applications. The boron oxide preparation method provided by this invention requires the addition of sodium aluminofluorate. Adding a certain amount of sodium aluminofluorate during the boron oxide preparation process not only reduces the introduction of impurities but also effectively lowers the viscosity of the resulting boron oxide, giving it a low viscosity that meets the requirements of a liquid sealant for gallium antimonide crystals. The preparation method provided by this invention is simple, and its advantages include low moisture content, low viscosity, low impurities, and high transparency in the prepared sodium aluminofluorate-doped boron oxide. Furthermore, it can be recast into different sizes and shapes, covering materials of varying areas, thus meeting the requirements of a liquid sealant for gallium antimonide crystals. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of boron oxide prepared in Example 1 of the present invention in a stainless steel crucible;

[0019] Figure 2 This is a schematic diagram of the boron oxide prepared in Comparative Example 2 of the present invention in a stainless steel crucible.

[0020] Figure 3 A schematic diagram of boron oxide prepared in Comparative Example 6 of this invention in a platinum crucible;

[0021] Figure 4 A schematic diagram of boron oxide prepared in Comparative Example 7 of this invention in a platinum crucible. Detailed Implementation

[0022] This invention discloses a low-viscosity, low-moisture boron oxide, its preparation method, and its applications. Those skilled in the art can refer to this document and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments, and those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0023] In the specific embodiments of the present invention, the experimental methods used are conventional methods unless otherwise specified, and the materials and reagents used are commercially available unless otherwise specified.

[0024] The present invention will be further described below with reference to the embodiments:

[0025] Example 1

[0026] S1. Heating of anhydrous boron oxide: 320g of 5N B2O3 (270ppm moisture) is put into a platinum crucible, and the vacuum furnace is heated to 750℃ and held for 2 hours to make the boron oxide transparent and molten.

[0027] S2, First dehydration: Heat the vacuum furnace to 880℃ and keep it at that temperature for 2 hours;

[0028] S3. Add sodium aluminofluoride: Weigh 3.5 mol% of 3N sodium aluminofluoride (g), quickly open the furnace door, and use a clamp to pour the sodium aluminofluoride powder into the crucible. The whole process should be controlled within 30 seconds, and the temperature should be controlled at 880℃ for 2 hours.

[0029] S4. Secondary dehydration: Turn on the vacuum switch, turn the valve to 1 / 2, and draw the vacuum down to below 20Pa. Continue to raise the temperature by 200℃, keep it at that temperature for 2 hours, and then open all the valves. Keep the temperature constant, reduce the vacuum down to 5Pa, and keep it at that temperature for 2 hours until no bubbles are observed in the melt.

[0030] S5. Casting: After introducing nitrogen to positive pressure, remove the crucible within 15 minutes and cast it in a 316 stainless steel crucible at 20% humidity. Then, transfer the boron oxide to a glove box for cooling. Results showed that the boron oxide had a water content of 280 ppm and was transparent. Figure 1 As shown, Figure 1 This is a schematic diagram of boron oxide prepared in Example 1 of the present invention in a stainless steel crucible.

[0031] In this embodiment 1, when the boron oxide prepared was put into use in a single crystal furnace, it can be seen through the observation window that the liquid surface is transparent and there are some bubbles. During the crystal pulling process, a layer of viscous substance is attached to the crystal surface. The crystal can be easily pulled out of the liquid seal layer, rises without jamming, and the crystal does not stick to the liquid sealant, thus successfully pulling out the single crystal.

[0032] Comparative Example 1

[0033] Boron oxide was produced according to the method in Example 1, except that sodium aluminofluoroate was not added. The results showed that the water content of the boron oxide was 283 ppm, and the color was transparent.

[0034] When the boron oxide prepared in Comparative Example 1 was put into use in a single crystal furnace, it could be seen through the observation window that the liquid surface was transparent and contained some bubbles. During the crystal pulling process, a layer of viscous substance was also attached to the crystal surface, but it was not easy to detach and the rise was obviously stuck. After growing at the same diameter for a period of time, the crystal and the liquid sealant adhered to each other, resulting in the seed crystal breaking and the crystal pulling failure.

[0035] Comparative Example 2

[0036] Boron oxide was produced according to the method in Example 1, except that 2N sodium aluminofluoroate was used. The results showed that the water content of the boron oxide was 295 ppm, and its color was yellow. Figure 2 As shown, Figure 2 This is a schematic diagram of the boron oxide prepared in Comparative Example 2 of the present invention in a stainless steel crucible.

[0037] Comparative Example 3

[0038] Boron oxide was produced according to the method in Example 1, except that 3N sodium aluminofluorate was used, and the color was yellow powder. The results showed that the water content of the boron oxide was 282 ppm, and the color was yellow.

[0039] Comparative Example 4

[0040] Boron oxide was produced according to the method in Example 1, except that instead of adding boron oxide, 345g of boric acid was added, resulting in 322g of boron oxide for further reactions. The results showed that the boron oxide had a water content of 340ppm and was transparent in color.

[0041] Comparative Example 5

[0042] Boron oxide was produced according to the method in Example 1, except that 4N boron oxide was used and the moisture content was 298 ppm. The results showed that the water content of the boron oxide was 294 ppm and its color was yellow.

[0043] Comparative Example 6

[0044] Boron oxide was produced according to the method in Example 1, except that a platinum crucible was used for demolding. The resulting cast boron oxide could not be detached due to expansion, had a water content of 283 ppm, and was transparent in color. Figure 3 As shown, Figure 3 This is a schematic diagram of boron oxide prepared in Comparative Example 6 of the present invention in a platinum crucible.

[0045] Comparative Example 7

[0046] Boron oxide was produced according to the method in Example 1, except that 3N sodium aluminofluoroate was used, which was a yellow powder, and a platinum crucible was used for demolding. The resulting cast boron oxide could not be detached due to expansion, had a moisture content of 287 ppm, and was yellow in color. Figure 4 As shown, Figure 4 This is a schematic diagram of boron oxide prepared in Comparative Example 7 of the present invention in a platinum crucible.

[0047] Comparative Example 8

[0048] Boron oxide was produced according to the method in Example 1, except that the nitrogen gas used was 5N pure. The results showed that the boron oxide had a water content of 318 ppm and was transparent.

[0049] Comparative Example 9

[0050] Boron oxide was produced according to the method in Example 1, except that the casting moisture content was 40%. The results showed that the boron oxide had a moisture content of 342 ppm and was transparent.

[0051] Comparative Example 10

[0052] Boron oxide was produced according to the method in Example 1, except that the dehydration method used was a two-step process, that is, only steps S1, S3, S4 and S5 of Example 1 were performed. The results showed that the water content of the boron oxide was 323 ppm and it was transparent.

[0053] Comparative Example 11

[0054] Boron oxide was produced according to the method in Example 1, except that a high-purity quartz crucible was used for the molten material. As a result, the crucible fractured due to the expansion of the residual boron oxide solution upon cooling.

[0055] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing low-viscosity, low-moisture boron oxide, characterized in that, Includes the following steps: S1) Boron oxide is heated and melted to obtain molten boron oxide; the purity of the boron oxide is 5 N; the water content of the boron oxide is less than 300 ppm; The molten boron oxide is then subjected to a single heating process to remove water. S2) The material obtained in step S1) and sodium aluminofluoroate are calcined; the amount of sodium aluminofluoroate added accounts for 3.2 mol%~3.8 mol% of the total amount of sodium aluminofluoroate and boron oxide in step S1); the sodium aluminofluoroate is white sodium aluminofluoroate with a purity of 3N; the calcination temperature is 850~900℃; the calcination time is 1~2 h; S3) The material obtained in step S2) is heated and dehydrated a second time. The material obtained after the second heating and dehydration is cast into a bright 316 stainless steel mold to obtain low viscosity and low moisture boron oxide. In step S1), the dehydration of molten boron oxide by heating is specifically performed by heating the molten boron oxide to 850-900℃ at a heating rate of 60-80℃ / h and calcining it for 1-2 h. In step S3), the material obtained in step S2) is subjected to secondary heating and dehydration. More specifically, the material obtained in step S2) is calcined at 1000~1100℃ for 1~2 h at a pressure below 20 Pa, and then kept at a pressure below 5 Pa for 2~4 h.

2. Low-viscosity, low-moisture boron oxide obtained by the preparation method according to claim 1.

3. The application of the low-viscosity, low-moisture boron oxide obtained by the preparation method of claim 1 as a liquid sealant for gallium antimonide crystals.

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