Platinum crucible used for crystal growth and manufacturing method therefor

Abstract

A manufacturing method for a platinum crucible used for crystal growth, which comprises steps: smelting platinum in a composite crucible, and casting same into a platinum ingot; and the platinum ingot undergoing hot forging, rolling, first annealing, rough spinning, second annealing, fine spinning and third annealing, so as to obtain the platinum crucible used for crystal growth. The platinum crucible has a smooth surface, homogeneous texture and consistent thickness, involves one-time forming from a sheet material and does not need to weld an outer edge, so that the product quality is greatly improved than that of traditional welding processes. In addition, platinum is smelted and purified by using the composite crucible during the smelting process, so that the leakage rate of the platinum crucible during crystal growth processes is reduced, and furthermore, the platinum crucible can be subjected to smelting and spinning again for manufacturing a new one, thereby achieving recovery of platinum.

Description

A platinum crucible for crystal growth and preparation method thereof

[0001] This application claims priority to the Chinese patent application filed with the Patent Office of China on January 2, 2024, with application number CN202410001249.8 and invention name “A platinum crucible for crystal growth and its preparation method”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of crystal growth, and in particular to a method for preparing a platinum crucible for crystal growth. Background Art

[0003] As a medium for converting multiple energy forms, including light, electricity, heat, magnetism, sound, and force, artificial crystals (ICLs) are key strategic materials in high-tech fields such as lasers and optoelectronics, microelectronics, communications, information, healthcare, aerospace, and national defense. They are also one of the fastest-growing and most competitive technologies in the world. Their development is crucial for my country's scientific and technological development, national economic development, and national defense. However, the production of ICLs typically requires high temperatures and prolonged processing times, and the raw materials used to grow ICLs often contain corrosive substances such as lead, cadmium, and manganese. Therefore, platinum, a precious metal with a high melting point, is typically used as the crucible material for crystal growth. However, platinum crucibles can corrode over time and even leak during the growth process. This leakage not only causes crystal growth failure, severely impacts yield, and can even damage the furnace, but also increases platinum loss and releases large amounts of corrosive vapors, polluting the environment. Therefore, the preparation of platinum crucibles is a crucial step in crystal production. Existing platinum crucible preparation techniques typically utilize die stamping and welding. This method uses a bottom die to stretch or forge the platinum sheet, then welds the outer edge of the crucible. Because the force is applied locally, the wall thickness in the stressed area is thinner than in other areas, resulting in uneven thickness throughout the crucible, ultimately affecting the lifespan of the platinum crucible. A small number of platinum crucibles use conventional melting and spinning techniques, but after one or two uses, the platinum material becomes contaminated by impurities, reducing its ductility and increasing its brittleness, making it unsuitable for further spinning and, therefore, unusable.

[0004] Summary of the Invention

[0005] The purpose of this application is to provide a platinum crucible for crystal growth and a preparation method thereof, which reduces the leakage rate of the platinum crucible during the crystal growth process and enables recycling. The specific technical solution is as follows:

[0006] A first aspect of the present application provides a method for preparing a platinum crucible for crystal growth, comprising the following steps:

[0007] Melting platinum in a composite crucible and casting it into platinum ingots;

[0008] The composite crucible is composed of an inner layer material, a middle layer material, and an outer layer material. The inner layer material is selected from at least one of calcium carbonate, silicon dioxide, and calcium oxide. The middle layer material is selected from at least one of zirconium oxide and magnesium oxide. The outer layer material is selected from composite quartz.

[0009] The platinum ingot is subjected to hot forging, sheet rolling, first annealing, rough spinning, second annealing, fine spinning, and third annealing to prepare the platinum crucible for crystal growth.

[0010] In one embodiment of the present application, the thickness of the inner layer material is 1 to 3 mm.

[0011] In one embodiment of the present application, the thickness of the middle layer material is 3 to 7 mm.

[0012] In one embodiment of the present application, the thickness of the outer layer material is 7 to 12 mm.

[0013] In one embodiment of the present application, the smelting temperature is 1700-2000°C.

[0014] In one embodiment of the present application, the hot forging temperature is 600-1000°C.

[0015] In one embodiment of the present application, the temperature of the first annealing is 800-1000°C, and the time is 1-3 hours; the temperature of the second annealing is 800-1000°C, and the time is 1-3 hours; the temperature of the third annealing is 800-1000°C, and the time is 1-3 hours.

[0016] In one embodiment of the present application, the thickness of the platinum crucible used for crystal growth is 0.3-1.5 mm.

[0017] The second aspect of the present application provides a platinum crucible for crystal growth prepared by the preparation method described in the first aspect of the present application.

[0018] Beneficial effects of this application:

[0019] The present application provides a method for preparing a platinum crucible for crystal growth, wherein platinum is smelted and cast into a platinum ingot in a composite crucible, and the platinum ingot is subjected to hot forging, sheet rolling, a first annealing, rough spinning, a second annealing, fine spinning, and a third annealing to prepare a platinum crucible for crystal growth. The platinum crucible has a smooth surface (surface finish can reach level 6), uniform structure, and consistent thickness. The sheet is formed in one step, and the outer edge does not require welding, which greatly improves the product quality compared to traditional welding processes. By using the composite crucible of the present application to smelt and purify platinum during the smelting process, the leakage rate of the platinum crucible during the crystal growth process is reduced. The platinum crucible can also be repeatedly smelted and spun to prepare the platinum crucible, so that the platinum can be recycled.

[0020] Of course, it is not necessary to achieve all the advantages described above at the same time when implementing any product or method of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other embodiments can also be obtained based on these drawings.

[0022] FIG1 is a schematic structural diagram of a composite crucible according to an embodiment of the present application;

[0023] FIG2 is a flow chart of the preparation of a platinum crucible for crystal growth according to an embodiment of the present application;

[0024] FIG3 is a schematic diagram of the planar structure of a platinum crucible used for crystal growth in Example 1 of the present application (unit: mm);

[0025] FIG4 is a schematic diagram of the planar structure of a platinum crucible used for crystal growth in Comparative Example 2 of the present application (unit: mm).

[0026] In the figure, 1. Inner layer material, 2. Middle layer material, 3. Outer layer material, diameter. DETAILED DESCRIPTION

[0027] The following will be combined with the accompanying drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0028] A first aspect of the present application provides a method for preparing a platinum crucible for crystal growth, comprising the following steps:

[0029] Melting platinum in a composite crucible and casting it into platinum ingots;

[0030] The composite crucible is composed of an inner layer material, a middle layer material, and an outer layer material. The inner layer material is selected from at least one of calcium carbonate, silicon dioxide, and calcium oxide. The middle layer material is selected from at least one of zirconium oxide and magnesium oxide. The outer layer material is selected from composite quartz.

[0031] The platinum ingot is subjected to hot forging, sheet rolling, first annealing, rough spinning, second annealing, fine spinning, and third annealing to prepare the platinum crucible for crystal growth.

[0032] In the present application, the prepared platinum crucible for crystal growth can be recycled by repeating the preparation steps of the present application after use.

[0033] In the present application, there is no particular limitation on the device used for the smelting, as long as the purpose of the present application can be achieved. For example, platinum smelting can be carried out in a high-frequency smelting furnace.

[0034] In the present application, there is no particular limitation on the shape and size of the platinum crucible, as long as the purpose of the present application can be achieved.

[0035] In the present application, there is no particular limitation on the spinning molds used for the rough spinning and the fine spinning, as long as the purpose of the present application can be achieved. They can be designed according to the shape and size of the platinum crucible required for crystal growth.

[0036] In this application, the composite quartz refers to a quartz fiber reinforced quartz ceramic composite material purchased from Luoyang Beiyuan New Materials Technology Co., Ltd.

[0037] The inventors discovered in their research that platinum smelting is a crucial step in preparing platinum crucibles for crystal growth, determining the ability and quality of subsequent spinning. After a platinum crucible has been used for crystal growth, the platinum stripped from the crystal can contain impurities from the raw materials used for crystal growth, as well as other impurities introduced during the production process. These impurities, such as compounds containing lead, cadmium, and manganese, can form cracks or pinholes in the crucible during subsequent crystal growth. This can lead to leakage during subsequent crystal growth. The present application carries out platinum smelting in a composite crucible, which is composed of an inner layer material, a middle layer material, and an outer layer material; the inner layer material can react chemically with impurities during high-temperature smelting, and the reactants evaporate from the surface of the melt or form light slag floating on the surface of the melt, thereby achieving the purpose of purifying the platinum; the melting point of the middle layer material is higher than that of the outer layer material, and the smelting temperature can be raised to 1700-2000°C, or even higher, and maintained for a long time; the outer layer material serves as a supporting material, which can protect and support the brittle and easily cracked middle layer material and play a role in heat preservation. The smelting of platinum in the composite crucible of the present application overcomes the problem of using only ordinary zirconia or composite quartz crucibles in the prior art, which causes the impurity content in the platinum crucible to accumulate more and more, making the platinum ductility worse and the brittleness increased. Cracks and peeling will occur during subsequent spinning, and a platinum crucible with a smooth and consistent surface cannot be obtained, and it is easy to leak material during crystal growth.

[0038] In the present application, the specific structure of the composite crucible is not particularly limited, as long as the purpose of the present application can be achieved. For example, the composite crucible may be the structure shown in FIG1 .

[0039] In the present application, there is no particular limitation on the preparation method of the composite crucible, as long as the purpose of the present application can be achieved. For example, the inner layer material can be prepared by a powder cold pressing method, wherein calcium carbonate, silicon dioxide or calcium oxide with a mesh size of less than 100 is filled in a non-metallic mold, and a pressure of 1 to 5 MPa is used on a cold press, and the pressure is maintained for 3 to 8 minutes to form the inner layer material. The non-metallic mold is selected from ceramic molds such as polyurethane, polyethylene, polypropylene, polytetrafluoroethylene or alumina. The inventor found in the study that not using a metal mold can avoid mold deformation during pressing. Metal scraps on the tool fall into the inner layer material and form an alloy with platinum during smelting, causing pollution; the middle layer material can be formed by powder hot pressing and sintering, and the outer layer material can be formed by hot pressing. This application does not specifically limit the specific methods of powder hot pressing and sintering, as long as the purpose of this application can be achieved; after the inner layer material, the middle layer material and the outer layer material are prepared respectively, the inner layer material, the middle layer material and the outer layer material are put together, and the layers are sealed with water glass. After that, the composite crucible is placed in an oven at 500-700°C and baked for 10-15 hours to prepare a composite crucible.

[0040] The inventors discovered during their research that by melting platinum in a composite crucible, casting it into platinum ingots, hot forging the platinum ingots, rolling them into sheets, annealing them for the first time, rough spinning them, annealing them for the second time, fine spinning them for the third time, a platinum crucible for crystal growth was prepared, which had a smooth surface, uniform structure, and consistent thickness. The sheet was formed in one step, and the outer edge did not require welding, greatly improving product quality compared to traditional welding processes. By using a composite crucible to melt and purify platinum during the smelting process, the leakage rate of the platinum crucible during the crystal growth process was reduced, and the platinum crucible could be prepared by repeated melting and spinning, allowing the platinum to be recycled.

[0041] In one embodiment of the present application, the thickness of the inner layer material is 1 to 3 mm. The inventors have found that controlling the thickness of the inner layer material within the range of the present application can remove impurities in the melt to the greatest extent while not affecting the use effect of the middle layer material.

[0042] In one embodiment of the present application, the thickness of the middle layer material is 3 to 7 mm. The inventors have found that if the thickness of the middle layer material is controlled within the range of the present application, the middle layer material can better withstand the melting temperature and is not easily damaged.

[0043] In one embodiment of the present application, the thickness of the outer layer material is 7 to 12 mm. The inventors have found that controlling the thickness of the outer layer material within the range of the present application supports and protects the inner and middle layer materials, thereby improving the thermal insulation effect of the composite crucible.

[0044] In one embodiment of the present application, the smelting temperature is 1700-2000° C. The inventors have found that controlling the smelting temperature within the range of the present application is conducive to sufficient melting of the platinum material and sufficient volatilization of impurities.

[0045] In one embodiment of the present application, the casting mold is made of copper. The inventors have found that using copper as the casting mold material allows for better heat dissipation during the casting process and faster demolding of the platinum ingot.

[0046] In one embodiment of the present application, the hot forging temperature is 600-1000° C. The inventors have found that controlling the hot forging temperature within the range of the present application is beneficial to reducing stress and defects such as shrinkage cavities and pores during the casting process, and increasing the plasticity and toughness of the material.

[0047] In one embodiment of the present application, the temperature of the first annealing is 800-1000°C and the time is 1-3 hours; the temperature of the second annealing is 800-1000°C and the time is 1-3 hours; the temperature of the third annealing is 800-1000°C and the time is 1-3 hours. The inventors found in their research that the stress generated during processing can be eliminated by performing the first annealing after sheeting, the second annealing after rough spinning, and the third annealing after fine spinning. Furthermore, controlling the temperature and time of the first annealing, the second annealing, and the third annealing within the scope of the present application can better eliminate the stress generated during processing.

[0048] In one embodiment of the present application, the preparation method further includes cutting after the first annealing and before rough spinning. The present application does not particularly limit the size of the cutting, as long as the purpose of the present application can be achieved. The cutting can be performed according to the size of the platinum crucible required for crystal growth; for example, the platinum sheet after the first annealing is cut into discs in preparation for spinning.

[0049] In one embodiment of the present application, the method for preparing the platinum crucible for crystal growth is shown in Figure 2, comprising the following steps: melting platinum in a composite crucible and casting it into a platinum ingot; hot forging the platinum ingot, rolling it into sheets, annealing it for the first time, cutting it, rough spinning it, annealing it for the second time, fine spinning it, and annealing it for the third time to prepare the platinum crucible for crystal growth.

[0050] In one embodiment of the present application, the platinum crucible used for crystal growth has a thickness of 0.3 to 1.5 mm. The inventors have discovered that controlling the thickness of the platinum crucible used for crystal growth within the range of the present application can reduce the leakage rate of the prepared platinum crucible during the crystal growth process, and can also be repeatedly melted and spun to produce platinum crucibles, allowing the platinum crucible to be recycled. Furthermore, controlling the thickness of the platinum crucible within the range of the present application can reduce the amount of platinum used and reduce costs.

[0051] The second aspect of the present application provides a platinum crucible for crystal growth prepared by the preparation method described in the first aspect of the present application.

[0052] The platinum crucible provided in the present application for crystal growth has a smooth surface, uniform structure, consistent thickness, and the sheet is formed in one step without welding on the outer edge. The product quality is greatly improved compared with the traditional welding process. By using a composite crucible to melt and purify platinum during the smelting process, the leakage rate of the platinum crucible during the crystal growth process is reduced. The platinum crucible can also be prepared by repeated melting and spinning, so that the platinum can be recycled.

[0053] Example

[0054] The following examples and comparative examples are provided to more specifically illustrate the embodiments of the present invention. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0055] The composite crucible of the following embodiments adopts the composite crucible shown in FIG1 ; the details are as follows:

[0056] Preparation method of composite crucible A: Calcium carbonate with a mesh size below 100 is filled into a polyurethane mold, and cold pressing is performed on a cold press with a pressure of 3 MPa and pressure maintained for 5 minutes to prepare an inner layer material 1; the middle layer material 2 is purchased from Beijing Hamamatsu Photonics Technology Co., Ltd.; the outer layer material 3 is purchased from Luoyang Beiyuan New Materials Technology Co., Ltd.; the inner layer material 1, the middle layer material 2 and the outer layer material 3 are put together, and the layers are sealed with water glass, and then the composite crucible is placed in a 600°C oven and baked for 12 hours to obtain a composite crucible A; wherein, the inner layer material 1 is calcium carbonate with a thickness of 2 mm; the middle layer material 2 is zirconium oxide with a thickness of 5 mm; and the outer layer material 3 is composite quartz with a thickness of 10 mm.

[0057] Preparation method of composite crucible B: fill silica with less than 100 mesh into a polyurethane mold, use a pressure of 3Mpa on a cold press, maintain the pressure for 5 minutes and cold press to prepare inner layer material 1; middle layer material 2 is purchased from Beijing Hamamatsu Photonics Technology Co., Ltd.; outer layer material 3 is purchased from Luoyang Beiyuan New Materials Technology Co., Ltd.; inner layer material 1, middle layer material 2 and outer layer material 3 are put together, and water glass is used to seal the middle between the layers. Then, the composite crucible is placed in a 600°C oven and baked for 12 hours to obtain composite crucible B; wherein, inner layer material 1 is silica with a thickness of 2 mm; middle layer material 2 is zirconia with a thickness of 5 mm; outer layer material 3 is composite quartz with a thickness of 10 mm.

[0058] Preparation method of composite crucible C: calcium oxide with a mesh size below 100 is filled into a polyurethane mold, and cold pressing is performed on a cold press with a pressure of 3 MPa and a pressure holding time of 5 minutes to prepare an inner layer material 1; the middle layer material 2 is purchased from Beijing Hamamatsu Photonics Technology Co., Ltd.; the outer layer material 3 is purchased from Luoyang Beiyuan New Materials Technology Co., Ltd.; the inner layer material 1, the middle layer material 2 and the outer layer material 3 are put together, and the layers are sealed with water glass, and then the composite crucible is placed in a 600°C oven and baked for 12 hours to obtain a composite crucible C; wherein, the inner layer material 1 is calcium oxide with a thickness of 2 mm; the middle layer material 2 is zirconium oxide with a thickness of 5 mm; and the outer layer material 3 is composite quartz with a thickness of 10 mm.

[0059] Preparation method of composite crucible D: Calcium carbonate with a mesh size below 100 is filled into a polyurethane mold, and cold pressing is performed on a cold press with a pressure of 3 MPa and a pressure holding time of 5 minutes to prepare an inner layer material 1; the middle layer material 2 is purchased from Beijing Hamamatsu Photonics Technology Co., Ltd.; the outer layer material 3 is purchased from Luoyang Beiyuan New Materials Technology Co., Ltd.; the inner layer material 1, the middle layer material 2, and the outer layer material 3 are put together, and the layers are sealed with water glass. After that, the composite crucible is placed in a 600°C oven and baked for 12 hours to obtain a composite crucible D; wherein, the inner layer material 1 is calcium carbonate with a thickness of 2 mm; the middle layer material 2 is magnesium oxide with a thickness of 5 mm; and the outer layer material 3 is composite quartz with a thickness of 10 mm.

[0060] Example 1

[0061] (1) Under oxygen-free conditions, 2500 g of platinum sheet was placed in the composite crucible A in a high-frequency melting furnace, the melting temperature was set to 1800 ° C for melting, and then poured into a copper casting mold to form (diameter) × 7 cm (height) platinum ingot;

[0062] (2) hot forging the platinum ingot at 800°C to form a platinum block of 14 cm (length) × 7 cm (width) × 1.4 cm (thickness);

[0063] (3) rolling the hot-forged platinum block into a platinum sheet of 40 cm (length) × 20 cm (width) × 0.17 cm (thickness), while maintaining the same direction of the platinum sheet entering the sheet rolling machine;

[0064] (4) The rolled platinum sheet was subjected to a first annealing at 900°C for 2h; the platinum sheet after the first annealing was cut into two discs with a diameter of 19cm and a thickness of 0.2cm, and the discs were roughly spun using a spinning machine, and subjected to a second annealing at 900°C for 2h. The platinum sheet was finely spun using a spinning machine, and subjected to a third annealing at 900°C for 2h to prepare a platinum crucible with a thickness of 0.8mm for crystal growth. The schematic diagram of the planar structure of the platinum crucible is shown in Figure 3.

[0065] Example 2

[0066] Except that the composite crucible A in Example 1 is replaced by the composite crucible B, the rest is the same as Example 1.

[0067] Example 3

[0068] Except that the composite crucible A in Example 1 is replaced by the composite crucible C, the rest is the same as Example 1.

[0069] Example 4

[0070] Except that the composite crucible A in Example 1 is replaced by the composite crucible D, the rest is the same as Example 1.

[0071] Comparative Example 1

[0072] The process is the same as that of Example 1 except that the composite crucible A in Example 1 is replaced by a zirconia crucible.

[0073] Comparative Example 2

[0074] The present invention is the same as Example 1 except that step (4) is replaced by “cutting the rolled platinum sheet and rolling it into a large cylinder, a conical cylinder and a small cylinder as shown in FIG4 , welding the seams of the large cylinder, the conical cylinder and the small cylinder respectively, and then welding the large cylinder, the conical cylinder and the small cylinder into one to prepare a platinum crucible with a thickness of 0.8 mm for crystal growth (the position of the weld is shown by the dotted line in FIG4 )”.

[0075] Test Case

[0076] The following are the crucible-drop crystal growth furnace purchased from Fuzhou Fred Experimental Equipment Co., Ltd., model KLS-GWL-4WQ-120; the crystal orientation instrument purchased from Dandong Aolong Radiation Instrument Group Co., Ltd., model YX-2H8A; the spectral quantitative analysis was tested at Wuxi Interpai Platinum Co., Ltd., and the equipment manufacturer was Suzhou Huygens Instrument Technology Co., Ltd., model AES-8000.

[0077] Test Example 1: Determination of the Recycling of Platinum Crucibles for Crystal Growth

[0078] Preparation of the synthetic raw material for lead indium niobate-lead magnesium niobate-lead titanate: 415.706 g of indium niobate, 549.502 g of magnesium niobate, 303.023 g of titanium dioxide, and 2731.769 g of lead monoxide were weighed and mixed uniformly in a mixer. The mixture was placed in a sintering furnace at 900°C for 5 hours for a first sintering synthesis. The synthesized material blocks were crushed, ground, and mixed, and then placed in a sintering furnace again at 1100°C for 5 hours for a second sintering synthesis. The resulting material blocks were then crushed, ground, and mixed to obtain 4000 g of the synthetic raw material for lead indium niobate-lead magnesium niobate-lead titanate.

[0079] Preparation of cadmium tungstate synthetic raw materials: Weigh 1283.216g of cadmium oxide and 2316.784g of tungsten oxide and mix them evenly in a mixer, place them in a sintering furnace at 800℃ for 5h for the first sintering synthesis, crush, grind and mix the synthesized material blocks, place them in a sintering furnace again at 1000℃ for 5h for the second sintering synthesis, and then crush, grind and mix them to obtain 3600g of cadmium tungstate synthetic raw materials.

[0080] 4000 g of lead indium niobate-lead magnesium niobate-lead titanate synthetic raw materials were respectively loaded into the platinum crucibles prepared in Examples 1 to 4, and placed in a crucible descending crystal growth furnace for crystal growth. The crystal growth point temperature was controlled at 1290±5°C. After use, the platinum crucible was peeled off from the lead indium niobate-lead magnesium niobate-lead titanate crystal, and platinum crucibles were again prepared according to the preparation methods of Examples 1 to 4.

[0081] 3600 g of cadmium tungstate synthetic raw material was respectively loaded into the platinum crucibles prepared in Examples 1 to 4, and placed in a crucible descending crystal growth furnace for crystal growth. The crystal growth point temperature was controlled at 1280 ± 5 ° C. After use, the platinum crucible was peeled off from the cadmium tungstate crystal, and the platinum crucible was prepared again according to the preparation methods of Examples 1 to 4.

[0082] 4000 g of lead indium niobate-lead magnesium niobate-lead titanate synthetic raw material was charged into the platinum crucible prepared in Comparative Example 1 and placed in a crucible descending crystal growth furnace for crystal growth. The crystal growth point temperature was controlled at 1290±5°C. After use, the platinum crucible was peeled off from the lead indium niobate-lead magnesium niobate-lead titanate crystal, and a platinum crucible was prepared again according to the preparation method of Comparative Example 1.

[0083] 3600g of cadmium tungstate synthetic raw material was charged into the platinum crucible prepared in Comparative Example 1, and placed in a crucible descending crystal growth furnace for crystal growth. The crystal growth point temperature was controlled at 1280±5°C. After use, the platinum crucible was peeled off from the cadmium tungstate crystal, and a platinum crucible was prepared again according to the preparation method of Comparative Example 1.

[0084] 4000 g of the lead indium niobate-lead magnesium niobate-lead titanate synthetic raw material was charged into the platinum crucible prepared in Comparative Example 2 and placed in a crucible descending crystal growth furnace for crystal growth. The crystal growth point temperature was controlled at 1290±5°C. After use, the platinum crucible was peeled off from the lead indium niobate-lead magnesium niobate-lead titanate crystal, and then a platinum crucible was prepared according to the preparation method of Comparative Example 1.

[0085] 3600g of cadmium tungstate synthetic raw material was charged into the platinum crucible prepared in Comparative Example 2, and placed in a crucible descending crystal growth furnace for crystal growth. The crystal growth point temperature was controlled at 1280±5°C. After use, the platinum crucible was peeled off from the cadmium tungstate crystal, and then a platinum crucible was prepared according to the preparation method of Comparative Example 1.

[0086] After testing, it was found that 20 platinum crucibles prepared in Examples 1 to 4 were used for the growth of lead indium niobate-lead magnesium niobate-lead titanate crystals, and no platinum crucible leaked material. The preparation was repeated 10 times according to the methods of Examples 1 to 4, and then lead indium niobate-lead magnesium niobate-lead titanate crystals were grown, and still no platinum crucible leaked material. The grown lead indium niobate-lead magnesium niobate-lead titanate crystals had no cracks, inclusions or other defects, and the directions were consistent at all locations when tested on a crystal orientation instrument.

[0087] Twenty platinum crucibles prepared in Comparative Example 1 were used to grow lead indium niobate-lead magnesium niobate-lead titanate crystals. Nine of these crucibles leaked material. After growth was complete, the crucibles were peeled from the crystals, revealing polycrystalline crystals with numerous grain boundaries. Crystal orientation testing using a crystal orientation instrument revealed inconsistent crystal orientation and several cracks. Eleven platinum crucibles that did not leak material were stripped from the crystals and then melted again using zirconia crucibles according to the method of Comparative Example 1. However, cracks developed during spinning and the crystals could not be recycled.

[0088] Twenty platinum crucibles prepared in Comparative Example 2 were used to grow lead indium niobate-lead magnesium niobate-lead titanate crystals, of which 11 platinum crucibles leaked material. After the growth was completed, the platinum crucibles were peeled off from the crystals, and the obtained crystals were polycrystalline with a large number of grain boundaries. Using a crystal orientation instrument for detection, there was no consistent crystal direction and there were some crack defects. Preparation was performed once according to the method of Comparative Example 1, of which 12 platinum crucibles cracked during spinning and could not be recycled. In addition, 6 of the 8 platinum crucibles leaked material during crystal growth.

[0089] Twenty platinum crucibles prepared in Examples 1 to 4 were used to grow cadmium tungstate crystals, and none of the platinum crucibles leaked material. The preparations were repeated 10 times according to the methods of Examples 1 to 4, and then cadmium tungstate crystals were grown. Still, none of the platinum crucibles leaked material. The grown cadmium tungstate crystals had no defects such as cracks and inclusions, and were tested on a crystal orientation instrument, showing that the directions were consistent everywhere.

[0090] Twenty platinum crucibles prepared in Comparative Example 1 were used to grow cadmium tungstate crystals. Ten of these crucibles leaked material. After growth was complete, the crucibles were peeled from the crystals. The resulting crystals were polycrystalline, with numerous grain boundaries. Crystal orientation testing using a crystal orientation instrument revealed inconsistent crystal orientation and several cracks. The platinum sheets from the ten crucibles that did not leak material were peeled from the crystals and then melted again using zirconia crucibles according to the method of Comparative Example 1. However, cracks developed during spinning and the crystals could not be recycled.

[0091] Twenty platinum crucibles prepared in Comparative Example 2 were used to grow cadmium tungstate crystals, of which 9 platinum crucibles leaked material. After the growth was completed, the platinum crucible was peeled off from the crystal, and the obtained crystal was polycrystalline with a large number of grain boundaries. The crystal was tested using a crystal orientation instrument, and there was no consistent crystal direction, and there were some crack defects. The preparation was performed once according to the method of Comparative Example 1, of which 13 platinum crucibles cracked during spinning and could not be recycled. In addition, 6 of the 7 platinum crucibles leaked material during crystal growth.

[0092] The above results show that the platinum crucible obtained by the preparation method of the present application can reduce the leakage rate of the prepared platinum crucible during the crystal growth process by using the composite crucible of the present application to smelt and purify platinum during the smelting process. The platinum crucible can also be repeatedly smelted and spun to prepare the platinum crucible, so that the platinum crucible can be recycled.

[0093] Test Example 2: Determination of Impurity Content and Ductility in Platinum Crucibles Used for Crystal Growth

[0094] After growing lead indium niobate-lead magnesium niobate-lead titanate crystals or cadmium tungstate crystals on the platinum crucibles prepared in Examples 1 to 4 according to the method in Test Example 1, the platinum crucible was peeled off from the lead indium niobate-lead magnesium niobate-lead titanate crystals or cadmium tungstate crystals, and platinum crucibles were again prepared according to the preparation methods of Examples 1 to 4, respectively, which was recorded as one cycle; after growing lead indium niobate-lead magnesium niobate-lead titanate crystals or cadmium tungstate crystals on the platinum crucibles prepared in Comparative Examples 1 and 2 according to the method in Test Example 1, the platinum crucible was peeled off from the lead indium niobate-lead magnesium niobate-lead titanate crystals or cadmium tungstate crystals, and the platinum crucible was again prepared according to the preparation method of Comparative Example 1, which was recorded as one cycle; after each cycle, the content of impurities such as lead and cadmium in the platinum crucible was detected by spectral quantitative analysis (detection equipment model AES-8000), and the thickness of the platinum sheet before fracture was compared by thinning the homemade platinum sheet on a sheet rolling machine multiple times until it broke, and the ductility of the platinum crucible was tested.

[0095] After testing, it was found that the platinum crucibles prepared in Examples 1 to 4 had lead and cadmium contents in the platinum crucibles obtained after one cycle for the growth of lead indium niobate-lead magnesium niobate-lead titanate or cadmium tungstate crystals, which were all less than 0.0005 wt%; the platinum crucible prepared in Comparative Example 1 had a lead content of 0.039 wt% in the platinum crucible obtained after one cycle for the growth of lead indium niobate-lead magnesium niobate-lead titanate crystals, and a cadmium content of 0.051 wt% in the platinum crucible obtained after one cycle for the growth of cadmium tungstate crystals; the platinum crucible prepared in Comparative Example 2 had a lead content of 0.025 wt% in the platinum crucible obtained after one cycle for the growth of lead indium niobate-lead magnesium niobate-lead titanate crystals, and a cadmium content of 0.041 wt% in the platinum crucible obtained after one cycle for the growth of cadmium tungstate crystals. The platinum crucibles prepared in Examples 1 to 4 were used for the growth of lead indium niobate-lead magnesium niobate-lead titanate crystals, and the lead content in the platinum crucibles obtained after two cycles was <0.0005wt%. The platinum crucibles prepared in Comparative Examples 1 and 2 were used for the growth of lead indium niobate-lead magnesium niobate-lead titanate crystals, and the lead contents in the platinum crucibles obtained after two cycles were 0.047wt% and 0.033wt%, respectively. The platinum crucibles prepared in Examples 1 to 4 were used for the growth of cadmium tungstate crystals, and the cadmium contents in the platinum crucibles obtained after two cycles were <0.0005wt%. The platinum crucibles prepared in Comparative Examples 1 and 2 were used for the growth of cadmium tungstate crystals, and the cadmium contents in the platinum crucibles obtained after two cycles were 0.066wt% and 0.053wt%, respectively.

[0096] The platinum crucibles prepared in Examples 1 to 4, Comparative Example 1, and Comparative Example 2 were used to grow lead indium niobate-lead magnesium niobate-lead titanate crystals, and the platinum crucibles obtained in one cycle were all made into platinum test pieces with a length of 50 mm, a width of 30 mm, and a thickness of 1 mm. These were rolled multiple times along the length direction on a sheet rolling machine. The thicknesses of the platinum test pieces at break were 0.08 mm, 0.08 mm, 0.08 mm, 0.07 mm, 0.15 mm, and 0.12 mm, respectively. The platinum crucibles prepared in Examples 1 to 4, Comparative Example 1, and Comparative Example 2 were used to grow cadmium tungstate crystals, and the platinum crucibles obtained in one cycle were all made into platinum test pieces with a length of 50 mm, a width of 30 mm, and a thickness of 1 mm. These were rolled multiple times along the length direction on a sheet rolling machine. The thicknesses of the platinum test pieces at break were 0.08 mm, 0.08 mm, 0.08 mm, 0.08 mm, 0.14 mm, and 0.13 mm, respectively. After two cycles of each of Examples 1 to 4, Comparative Example 1, and Comparative Example 2, the thicknesses of the platinum test pieces for growing lead indium niobate-lead magnesium niobate-lead titanate crystals at fracture were tested according to the above method, and the thicknesses of the platinum test pieces for growing cadmium tungstate crystals at fracture were 0.08 mm, 0.08 mm, 0.08 mm, 0.18 mm, and 0.15 mm, respectively; the thicknesses of the platinum test pieces for growing cadmium tungstate crystals at fracture were 0.08 mm, 0.08 mm, 0.09 mm, 0.08 mm, 0.18 mm, and 0.16 mm, respectively.

[0097] The above results illustrate that the platinum crucible obtained by the preparation method of the present application has a low impurity content, and the platinum crucible still maintains a high purity and ductility after being used for crystal growth, which can reduce the leakage rate of the platinum crucible during the crystal growth process. Repeated spinning of platinum crucibles can be performed to recycle platinum.

[0098] In summary, the method for preparing a platinum crucible for crystal growth provided in the present application comprises the following steps: melting platinum in a composite crucible, casting the platinum into a platinum ingot, hot forging the platinum ingot, rolling the platinum ingot into a sheet, annealing the platinum ingot for the first time, rough spinning the platinum ingot, annealing the platinum ingot for the second time, fine spinning the platinum ingot, and annealing the platinum ingot for the third time, thereby preparing a platinum crucible for crystal growth. The platinum crucible has a smooth surface, uniform structure, and consistent thickness. The sheet is formed in one step, and the outer edge does not need to be welded. The product quality is greatly improved compared to traditional welding processes. By using a composite crucible to purify platinum during the smelting process, the leakage rate of the platinum crucible during the crystal growth process is reduced. The platinum crucible can also be repeatedly smelted and spun to prepare a platinum crucible, so that the platinum can be recycled.

[0099] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A preparation method of a platinum crucible for crystal growth, which comprises the following steps: Melting platinum in a composite crucible and casting it into a platinum ingot; Wherein, the composite crucible is composed of an inner layer material, a middle layer material, and an outer layer material. The inner layer material is selected from at least one of calcium carbonate, silicon dioxide, and calcium oxide. The middle layer material is selected from at least one of zirconia and magnesia. The outer layer material is selected from composite quartz; Performing hot forging, rolling, first annealing, rough spinning, second annealing, fine spinning, and third annealing on the platinum ingot to prepare the platinum crucible for crystal growth.

2. The preparation method according to claim 1, wherein, The thickness of the inner layer material is 1-3 mm.

3. The preparation method according to claim 1, wherein The thickness of the middle layer material is 3-7 mm.

4. The preparation method according to claim 1, wherein The thickness of the outer layer material is 7-12 mm.

5. The preparation method according to claim 1, wherein The temperature of the melting is 1700-2000 °C.

6. According to the preparation method described in claim 1, wherein, The temperature of the hot forging is 600-1000 °C.

7. The preparation method according to claim 1, wherein, The temperature of the first annealing is 800-1000 °C, and the time is 1-3 hours; the temperature of the second annealing is 800-1000 °C, and the time is 1-3 hours; the temperature of the third annealing is 800-1000 °C, and the time is 1-3 hours.

8. The preparation method according to claim 1, wherein, The thickness of the platinum crucible for crystal growth is 0.3-1.5 mm.

9. A platinum crucible for crystal growth prepared by the preparation method according to any one of claims 1-8.

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