A method for synthesizing gadolinium gallium garnet single crystal

Abstract

The present invention relates to the technical field of crystal synthesis, and discloses a method for synthesizing gadolinium gallium garnet single crystal, which comprises the following steps: S1. After uniformly mixing the raw materials, load them into a mold, and use a briquetting machine to initially briquette the raw material powder into a block and then demold; S2. Put the briquetted raw material block into a muffle furnace for pre-sintering and cool it with the furnace; S3. Crush the cooled polycrystalline raw material, use die pressing to form it again, put it into the muffle furnace for sintering, repeat 1 to 3 times, cool it and then load it into a crucible, and vibrate the crucible to make the polycrystalline raw material uniformly filled; S4. Put the crucible containing the polycrystalline raw material into the guide rail of a horizontal crystal growth furnace, evacuate and then fill it with an inert gas, and control the crucible to sequentially pass through the melting zone, crystal growth zone and cooling zone of the furnace tube of the horizontal crystal growth furnace to complete crystal growth. The present invention uses the horizontal method to grow gadolinium gallium garnet single crystal, which can achieve continuous growth, and the obtained crystal has a high utilization rate and uniform stress.

Description

Technical Field

[0001] The present invention belongs to the technical field of crystal synthesis, and particularly relates to a method for synthesizing gadolinium gallium garnet single crystal. Background Art

[0002] At present, magneto-optical crystals have been widely used in the fields of optical isolators, magneto-optical memories, optical fiber communications, and integrated optical devices. Most of these materials are grown by liquid phase epitaxy (LPE) on single crystal substrates with large lattice constants, and the quality of the substrate directly determines the performance of the magneto-optical thin film. Gadolinium gallium garnet is a complex oxide with a garnet structure, and its chemical formula is Gd3Ga5O 12 (abbreviated as GGG), belonging to the cubic crystal system. GGG has excellent optical properties and stable chemical properties, and is widely used in structural materials and functional materials. In addition, the lattice constant of GGG single crystal (1.2380 nm) matches that of yttrium iron garnet (1.2376 nm), so it is considered to be a suitable substrate material for the growth of YIG-like magneto-optical epitaxial films.

[0003] Currently, the synthesis of large-size gadolinium gallium garnet (GGG) single crystals mostly uses the Czochralski method. The raw materials used for crystal growth are placed in a crucible and heated above the melting point by induction or resistance heating. A seed crystal rod connected by a pulling and rotating system is suspended above. The seed crystal rod is lowered to contact the melt surface, and the temperature of the raw material melt is maintained near the crystallization temperature. At this time, the seed crystal will neither melt nor crystallize too quickly, resulting in low crystal quality. The seed crystal rod is slowly pulled up and rotated, and the temperature of the temperature field is gradually lowered, and the melt gradually crystallizes along the seed crystal. The growth cycle of the Czochralski method is short, and the crystal growth situation can be directly observed through the observation port, and high-quality large-size crystals can be obtained. However, the crystals grown by the Czochralski method are columnar, with low material utilization rate in subsequent processing. At the same time, due to the pulling and rotation of the seed crystal rod during the crystal growth process of the Czochralski method, the internal stress of the crystal is uneven, and there is a risk of cracking during the slicing and grinding to prepare the substrate. Summary of the Invention

[0004] To solve the deficiencies mentioned in the above background art, the purpose of the present invention is to provide a method for synthesizing gadolinium gallium garnet single crystal, which uses the horizontal method to grow gadolinium gallium garnet single crystal, can achieve continuous growth, and the obtained crystal has high utilization rate and uniform stress.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for synthesizing gadolinium gallium garnet single crystal, comprising the following steps:

[0007] S1. According to the molecular formula Gd3Ga5O 12Weigh the raw materials Gd2O3 and Ga2O3 in stoichiometric ratio, uniformly mix the raw materials and then load them into a mold. Use a briquetting machine to initially press the raw material powder into a block and then demold it.

[0008] S2. Put the pressed raw material block into a muffle furnace, pre-sinter it at 900 - 1100 °C for 12 - 20 h, and cool it down with the furnace.

[0009] S3. Crush the cooled polycrystalline raw materials, use molding by die pressing again, put them into a muffle furnace for sintering, cool them down and then load them into a crucible, and vibrate the crucible to make the polycrystalline raw materials evenly filled.

[0010] S4. Put the crucible containing the polycrystalline raw materials into the guide rail of a horizontal crystal growth furnace, evacuate to 1.0×10 -4 Pa and then fill it with an inert gas. Control the crucible to pass through the melting zone, crystal growth zone and cooling zone of the furnace tube of the horizontal crystal growth furnace in sequence to complete crystal growth.

[0011] Further preferably, the purities of both Gd2O3 and Ga2O3 are 99.999%, and Ga2O3 is in excess of 1.5 - 2 wt% based on the mass calculated according to the chemical formula stoichiometry.

[0012] Further preferably, in step S3, heat it up to 1200 - 1250 °C at a rate of 4 - 6 °C / min and hold for sintering for 8 - 10 h.

[0013] Further preferably, the crucible is one of molybdenum crucible, iridium crucible and graphite crucible. The crucible is in a boat shape, with a thickness of 20 - 30 mm, a length of 120 - 240 mm and a width of 120 mm. A seed crystal groove is provided at the front end of the crucible, and a GGG seed crystal is placed in the seed crystal groove.

[0014] Further preferably, the inert gas filled in step S4 is high-purity argon, and after filling the argon, the pressure in the furnace tube of the horizontal crystal growth furnace is brought to 105 - 115 kPa.

[0015] Further preferably, the ratio of the melting zone to the crucible length is 1:2 - 4, and the temperature of the melting zone is 1900 - 2000 °C.

[0016] Further preferably, the temperature gradient in the crystal growth zone is 3.5 - 4.5 °C / mm, the temperature of the crystal growth zone is 1650 - 1750 °C, and the moving speed of the crucible in the crystal growth zone is 0.8 - 1.2 mm / h.

[0017] Further preferably, the temperature gradient in the cooling zone is 5 - 6 °C / mm to cool the crystal to below 200 °C.

[0018] Further preferably, buffer zones are provided at both ends of the furnace tube of the horizontal crystal growth furnace. A sealing partition is provided between the buffer zones and the melting zone and the cooling zone. After the crystal growth is completed in step S4, it is moved to one side buffer zone to be naturally cooled to room temperature, while the crucible filled with filler is placed in the other side buffer zone to prepare for the growth of the next crystal.

[0019] Advantages of the present invention:

[0020] The present invention uses the horizontal method to grow gadolinium gallium garnet single crystals, which can achieve continuous growth. The obtained crystals have a uniform internal lattice without heterophase, high short-wave transmittance, more uniform stress compared with the gadolinium gallium garnet single crystals synthesized by the Czochralski method, are not easily cracked and damaged during processing, and at the same time, the formed crystals are square, and the material utilization rate is higher than that of the columnar crystals formed by the Czochralski method. Description of the drawings

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0022] Figure 1 It is a schematic diagram of the zoning of the furnace tube of the horizontal crystal growth furnace for synthesizing gadolinium gallium garnet single crystals of the present invention;

[0023] Figure 2 It is an X-ray powder diffraction pattern of the gadolinium gallium garnet single crystal prepared in Example 1 of the present invention;

[0024] Figure 3 It is the crystal light transmittance test result of the gadolinium gallium garnet single crystal prepared in Example 1 of the present invention. Specific embodiments

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0026] In the embodiments of the present invention, a horizontal crystal growth furnace is used to synthesize gadolinium gallium garnet single crystals. As Figure 1 shown, the furnace tube of the horizontal crystal growth furnace includes a melting zone, a crystal growth zone, and a cooling zone arranged in sequence. Buffer zones are provided at both ends of the furnace tube, and the length ratio of the melting zone to the crucible is 1:2 to 4. The raw materials are 99.999% high-purity Gd2O3 and 99.999% high-purity Ga2O3. Embodiment

[0027] A method for synthesizing gadolinium gallium garnet single crystal, comprising the following steps:

[0028] S1. Weigh 1087.5 g of high-purity Gd2O3 and 951.2 g of high-purity Ga2O3, mix them evenly, load them into a mold, use a NYL-600 type hydraulic press, press the raw materials into a block under a pressure of 280 kN, and then demold;

[0029] S2. Put the pressed raw material block into a muffle furnace, pre-sinter it at 900 °C for 20 h, and cool it with the furnace;

[0030] S3. Crush the cooled polycrystalline raw materials, use die pressing again, put them into a muffle furnace, heat them up to 1250 °C at a rate of 4 °C / min, keep them sintered for 8 h, cool them, and then load them into a 240×120×100 mm boat-shaped iridium crucible with a crucible thickness of 30 mm, vibrate the crucible to make the polycrystalline raw materials evenly filled;

[0031] S4. Put the crucible containing the polycrystalline raw materials into the guide rail of a horizontal crystal growth furnace, evacuate to 1.0×10 -4 Pa, then flush in high-purity argon until the pressure in the furnace tube of the horizontal crystal growth furnace reaches 115 kPa. The crucible first passes through the melting zone, the temperature of the melting zone is 2000 °C, melt the polycrystalline raw materials in the crucible and contact them with the seed crystal at the front section of the crucible. When the front section of the crucible moves to the crystal growth zone, the temperature of the crystal growth zone is 1650 - 1750 °C, the temperature gradient is 3.5 - 4.5 °C / mm, lower the temperature of the raw material melt near the crystallization temperature so that the polycrystalline melt starts to grow from the seed crystal, control the moving speed of the crucible to be 0.8 - 1.2 mm / h, make it equivalent to the crystal diffusion speed, finally the crucible moves to the cooling zone, the temperature gradient of the cooling zone is 5 - 6 °C / mm, gradually cool the crystal to below 200 °C, and then move it to a buffer zone on one side to cool naturally to room temperature.

[0032] Perform the following tests on the gadolinium gallium garnet single crystal prepared in Example 1:

[0033] Crystal X-ray powder diffraction analysis, which is in good agreement with the standard card of GGG, indicating that the crystal has no impurity phase and the crystal structure has not changed;

[0034] Crystal light transmittance detection, the transmittance spectrum in the 320 - 3000 nm band has almost no absorption in the whole band, and the transmittance reaches more than 80%, having good light transmittance. Example

[0035] A method for synthesizing gadolinium gallium garnet single crystal, comprising the following steps:

[0036] S1. Weigh 1053.4 g of high-purity Gd2O3 and 937.5 g of high-purity Ga2O3, mix them evenly, put them into a mold, and use a NYL-600 type hydraulic press to press the raw materials into a block under a pressure of 280 kN and then demold;

[0037] S2. Put the pressed raw material block into a muffle furnace, pre-sinter it at 1100 °C for 12 h, and cool it with the furnace;

[0038] S3. Crush the cooled polycrystalline raw materials, use die pressing again, put them into a muffle furnace, heat them up to 1200 °C at a rate of 6 °C / min, hold for sintering for 10 h, cool them, and then put them into a graphite crucible of 240×120×100 mm, and vibrate the crucible to make the polycrystalline raw materials evenly filled;

[0039] S4. Put the crucible containing the polycrystalline raw materials into the guide rail of a horizontal crystal growth furnace, evacuate to 1.0×10 -4 Pa, then fill it with high-purity argon until the pressure in the furnace tube of the horizontal crystal growth furnace reaches 105 kPa. The crucible first passes through the melting zone, and the temperature of the melting zone is 1900 °C. Melt the polycrystalline raw materials in the crucible and contact them with the seed crystal at the front section of the crucible. When the front section of the crucible moves to the crystal growth zone, lower the temperature of the raw material melt near the crystallization temperature so that the polycrystalline melt starts to grow from the seed crystal. Control the moving speed of the crucible at 0.8 - 1.2 mm / h to make it equivalent to the crystal diffusion speed. Finally, the crucible moves to the cooling zone to gradually cool the crystal to below 200 °C, and then move it to a buffer zone on one side to cool naturally to room temperature. Example

[0040] A method for synthesizing gadolinium gallium garnet single crystal, comprising the following steps:

[0041] S1. Weigh 1109.6 g of high-purity Gd2O3 and 975.8 g of high-purity Ga2O3, mix them evenly, put them into a mold, and use a NYL-600 type hydraulic press to press the raw materials into a block under a pressure of 280 kN and then demold;

[0042] S2. Put the pressed raw material block into a muffle furnace, pre-sinter it at 1000 °C for 16 h, and cool it with the furnace;

[0043] S3. Crush the cooled polycrystalline raw materials, use die pressing again, put them into a muffle furnace, heat them up to 1225 °C at a rate of 5 °C / min, hold for sintering for 8 h, cool them, and then put them into a molybdenum crucible of 240×120×100 mm, and vibrate the crucible to make the polycrystalline raw materials evenly filled;

[0044] S4. Put the crucible containing the polycrystalline raw materials into the guide rail of a horizontal crystal growth furnace, evacuate to 1.0×10 -4Pa, and then fill high-purity argon gas into the furnace tube of the horizontal crystal growth furnace until the pressure reaches 110 kPa. First, move the crucible through the melting zone where the temperature is 1950 °C to melt the polycrystalline raw materials in the crucible and make them contact with the seed crystal at the front section of the crucible. When the front section of the crucible moves to the crystal growth zone, lower the temperature of the raw material melt near the crystallization temperature so that the polycrystalline melt starts to grow from the seed crystal. Control the moving speed of the crucible at 0.8 - 1.2 mm / h to make it equivalent to the crystal diffusion speed. Finally, move the crucible to the cooling zone to gradually cool the crystal to below 200 °C, and then move it to the buffer zone on one side to cool naturally to room temperature.

[0045] Comparative Example 1

[0046] The method for synthesizing GGG crystals by the Czochralski method includes the following steps:

[0047] S1. Weigh 268.3 g of high-purity Gd2O3 and 236.5 g of high-purity Ga2O3, mix them evenly and load them into a mold. Use a NYL-600 type hydraulic press to press the raw materials into a block under a pressure of 280 kN and then demold;

[0048] S2. Put the pressed raw material block into a muffle furnace, pre-sinter it at 900 °C for 20 h, and cool it with the furnace;

[0049] S3. Crush the cooled polycrystalline raw materials, use molding by pressing again, put them into a muffle furnace and heat them up to 1250 °C at a rate of 4 °C / min, keep them sintered for 8 h, cool them and then load them into a cylindrical iridium crucible with a size of φ80×60 mm, vibrate the crucible to make the polycrystalline raw materials evenly filled;

[0050] S4. Place the crucible at the center of the induction heating coil in the hearth of the Czochralski crystal growth furnace, then adjust the seed rod to make the center of the seed crystal and the center of the crucible concentric. After evacuating, fill high-purity argon gas, heat up to 2000 °C to melt the polycrystalline raw materials, then lower the seed crystal to make it contact with the melt, control the temperature and go through the processes of necking, shoulder forming, equal diameter, and lifting support in sequence. After the crystal is lifted off, slowly lower the temperature to below 200 °C to cool the crystal.

[0051] In the description of this specification, the descriptions referring to terms such as "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0052] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and what is described in the above embodiments and the specification is only to illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements fall within the scope of the present invention claimed.

Claims

1. A method for synthesizing a gadolinium gallium garnet single crystal, characterized in that: The following steps are involved: S1, according to the molecular formula Gd3Ga5O 12 Weigh the raw materials Gd2O3 and Ga2O3 in a stoichiometric ratio, mix them evenly and put them into a mold, use a press to initially press the raw material powder into blocks and then demould; S2. Place the pressed raw material block into a muffle furnace, pre-sinter at 900-1100°C for 12-20h, and cool with the furnace; S3, crushing the cooled polycrystalline raw material, molding it again, sintering it in a muffle furnace, loading it into a crucible after cooling, and vibrating the crucible to make the polycrystalline raw material evenly filled; S4. Place the crucible containing the polycrystalline raw material into the guide rail of the horizontal crystal growth furnace and evacuate to 1.0×10 -4 Pa and then filled with inert gas, the crucible is controlled to pass through the melting zone, crystal growth zone and cooling zone of the furnace tube of the horizontal crystal growth furnace in sequence, the length ratio of the melting zone to the crucible is 1:2-4, the temperature of the melting zone is 1900-2000°C, the temperature gradient of the crystal growth zone is 3.5-4.5°C / mm, the temperature of the crystal growth zone is 1650-1750°C, the moving speed of the crucible is 0.8-1.2 mm / h, the temperature gradient of the cooling zone is 5-6°C / mm, the crystal is cooled to below 200°C, and the crystal growth is completed.

2. The method for synthesizing a gadolinium gallium garnet single crystal according to claim 1, characterized in that: The purity of the Gd2O3 and Ga2O3 is 99.999%, and the Ga2O3 is in excess of 1.5-2wt% based on the mass calculated according to the stoichiometric ratio.

3. The method for synthesizing a gadolinium gallium garnet single crystal according to claim 1, characterized in that: In step S3, the temperature is raised to 1200-1250° C. at a rate of 4-6° C. / min, and the sintering is carried out at the temperature for 8-10 hours.

4. The method for synthesizing a gadolinium gallium garnet single crystal according to claim 1, characterized in that: The crucible is one of a molybdenum crucible, an iridium crucible, and a graphite crucible. The crucible is in a boat shape with a crucible thickness of 20-30 mm, a length of 120-240 mm, and a width of 120 mm. A seed crystal groove is provided at the front end of the crucible, and a GGG seed crystal is placed in the seed crystal groove.

5. The method for synthesizing a gadolinium gallium garnet single crystal according to claim 1, characterized in that: The inert gas filled in step S4 is high-purity argon gas, and after the argon gas is filled in, the pressure in the furnace tube of the horizontal crystal growth furnace is increased to 105-115 kPa.

6. The method for synthesizing a gadolinium gallium garnet single crystal according to claim 1, characterized in that: Buffer zones are provided at both ends of the furnace tube of the horizontal crystal growth furnace, and sealed partitions are provided between the buffer zone and the melting zone and the cooling zone. After the crystal growth is completed in step S4, it is moved to one buffer zone to cool naturally to room temperature, while the filled crucible is placed in the other buffer zone to prepare for the next crystal growth.

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