Device and method for controlling the volatilization of gallium-containing photofunctional crystals

Abstract

The present invention discloses a pulling preparation device and method for controlling the volatilization of gallium-containing photofunctional crystals. The device comprises a crucible, a gallium-containing crystal arranged in the crucible, a heating mechanism for heating the gallium-containing crystal, and a pulling mechanism for assisting the growth of the gallium-containing crystal. The pulling end of the pulling mechanism extends into the crucible and abuts against the gallium-containing crystal arranged in the crucible. The heating mechanism comprises at least two heating units, each of which is respectively wound around the outer circumference of the crucible. The pulling preparation device adopts this multi-segment induction coil heating method to realize the gradual melting of the gallium-containing crystal melt from the crucible mouth to the crucible bottom as the crystal grows, thereby avoiding the problem of serious and uncontrollable volatilization of crystal melt components caused by the full-cycle melting of all gallium-containing crystals in the crucible.

Description

Technical Field

[0001] The present invention relates to the technical field of photofunctional crystal preparation, and in particular to a pulling preparation device and method for controlling the volatilization of gallium-containing photofunctional crystals. Background Art

[0002] Gallium-containing optically functional crystals, such as gadolinium gallium garnet (GGG), are excellent substrate crystals. Their lattice constant and thermal expansion coefficient closely match those of yttrium iron garnet (YIG) magneto-optical thin films. The quality of the GGG substrate directly determines the performance of the epitaxial thin film. Terbium gallium garnet (TGG) is an excellent magneto-optical crystal for visible and near-infrared lasers. Its performance directly affects the crystal's ability to withstand laser power and its transmission performance.

[0003] Gallium oxide, as one of the main components of gallium-containing crystals, is prone to volatilization and decomposition during the crystal growth process, Ga2O3=Ga2O+O2↑. The decomposed Ga2O and O2 react with the iridium crucible, leading to the production of iridium gold and heterogeneous oxides, which in turn causes: the melt composition deviates from the stoichiometric ratio, affecting the high-quality and stable growth of the crystal; the floating iridium gold affects the temperature gradient around the seed crystal, easily leading to eccentric growth of the crystal; the heterogeneous oxides are easily transported by melt convection to the solid-liquid interface and are wrapped to form particles in the crystal, leading to the generation of crystal defects.

[0004] Although Ga2O3 volatilization has been controlled to some extent through methods such as optimizing the initial raw material composition ratio (adding a certain proportion of excess gallium oxide), changing the crystal growth atmosphere (increasing the oxygen partial pressure), and pre-synthesizing high-purity polycrystalline raw materials, the composition ratio range for stable growth of gallium-containing crystals is narrow. Excessive gallium oxide will precipitate as a different phase within the crystal, leading to crystal scattering and severely affecting the crystal quality. While increasing the oxygen partial pressure can inhibit the decomposition of gallium oxide to a certain extent, it can also cause oxidation of the iridium crucible, thereby affecting crystal growth. Furthermore, as crystal size increases, the crystal growth cycle becomes longer, making it more difficult to control gallium oxide volatilization with these methods in the later stages of crystal growth. Especially with the rapid development of high-power solid-state laser and fiber laser technology, and the urgent demand for large-scale gallium-containing crystals, the above-mentioned gallium oxide volatilization problem has become prominent. Therefore, effectively controlling gallium oxide volatilization is a technical difficulty that needs to be overcome. Summary of the Invention

[0005] Based on the technical problems existing in the background technology, the present invention proposes a pulling preparation device and method for controlling the volatilization of gallium-containing photofunctional crystals, which can effectively control the volatilization of gallium oxide and improve the quality of the grown crystals.

[0006] The present invention proposes a pulling and preparation device for controlling the volatilization of gallium-containing photofunctional crystals, which includes a crucible, a gallium-containing crystal arranged in the crucible, a heating mechanism for heating the gallium-containing crystal, and a pulling mechanism for assisting the growth of the gallium-containing crystal. The pulling end of the pulling mechanism extends into the crucible and abuts against the gallium-containing crystal arranged in the crucible. The heating mechanism includes at least two heating units, each of which is respectively wrapped around the outer circumference of the crucible.

[0007] Furthermore, different heating units are sequentially attached to the outer circumference of the crucible and wound around it, the crucible opening is flush with the uppermost end of one of the heating units, and the heating temperature of the heating unit at the crucible opening is equal to the melting point of the crystal;

[0008] The power of the heating unit increases gradually from the bottom of the crucible to the crucible mouth, and the concentration of gallium oxide in the gallium-containing crystal decreases in a unidirectional gradient.

[0009] Furthermore, the heating unit includes a coil, and the spacing between adjacent wound coils in the same heating unit is equal to the spacing between adjacent coils in different heating units;

[0010] The coils in each heating unit have the same number of turns and the same diameter, and each heating unit is powered by a different power supply unit.

[0011] Furthermore, the pulling mechanism includes a seed crystal and a seed crystal rod, one end of the seed crystal rod is inserted into the crucible and fixed to the seed crystal, and the end of the seed crystal away from the seed crystal rod abuts against the upper end surface of the gallium-containing crystal.

[0012] Furthermore, a heat-insulating layer is provided on the outer periphery of the crucible, and the heating units are arranged in sequence in contact with the heat-insulating layer.

[0013] A method for preparing gallium-containing photofunctional crystals by controlling volatilization thereof comprises the following steps:

[0014] (A) The crucible size is determined according to the size of the gallium-containing crystal, and at least two independent heating units are wound around the periphery of the crucible, wherein the different heating units are wound in sequence from the bottom of the crucible to the crucible mouth.

[0015] (B) preparing a plurality of polycrystalline raw materials containing different proportions of gallium oxide according to the type of gallium-containing crystals, wherein the polycrystalline raw materials are provided in a corresponding number to the number of the heating units;

[0016] (C) placing the polycrystalline raw materials in a crucible in sequence, wherein the gallium oxide ratio increases unidirectionally from the crucible mouth to the crucible bottom;

[0017] (D) The polycrystalline raw material in the crucible is heated in sections by the heating unit, and the polycrystalline raw material in the crucible is pulled and grown by the pulling mechanism.

[0018] Further, after preparing the polycrystalline raw material in (B), select <111> The cross section of the seed crystal blank is circular or rectangular, and one end of the seed crystal blank is fixedly connected to the seed crystal rod.

[0019] Furthermore, in (D), heating the polycrystalline raw material in the crucible in sections by the heating unit and pulling the polycrystalline raw material in the crucible for growth by the pulling mechanism, the steps specifically include:

[0020] (D1) The crucible is vacuumed. When the pressure in the furnace is less than 10 Pa, protective gas and less than 5% oxygen are filled to (1.0-1.8)×10 5 Pa;

[0021] (D2) applying multi-stage induction heating to the coils in different heating units, gradually increasing the heating power of the coils from the bottom of the crucible to the crucible mouth, until the heating temperature of the heating unit at the crucible mouth is equal to the crystal melting point, and the polycrystalline raw material at the crucible mouth is melted;

[0022] (D3) slowly lowering the seed crystal to the end surface of the molten polycrystalline raw material, and adjusting the heating power of the coil until the seed crystal and the end surface of the molten polycrystalline raw material are in stable contact for more than 0.2 hours;

[0023] (D4) pulling and rotating the seed crystal (41) at a certain rate to perform crystal growth of the polycrystalline raw material;

[0024] (D5) feedback the induction heating power of the coil (31) according to the downward displacement of the solid-liquid interface of the polycrystalline raw material and the crystal growth rate, thereby achieving real-time movement of the solid-liquid interface;

[0025] (D6) After the crystal growth is completed, the seed crystal rod is pulled up at a certain rate to separate the crystal from the liquid surface in the crucible, and the crystal is cooled to room temperature before being taken out.

[0026] Furthermore, when multi-stage induction heating is adopted for the coils in different heating units, the power of the coil at the crucible mouth is 500 to 1000 W higher than the power of the coil at the crucible bottom.

[0027] Furthermore, in (C), the polycrystalline raw materials are sequentially placed in a crucible, and the gallium oxide ratio increases unidirectionally from the crucible mouth to the crucible bottom; the gallium oxide ratio changes unidirectionally within the range of 0 to 10%.

[0028] The advantages of the pulling and preparing device and method for controlling the volatilization of gallium-containing photofunctional crystals provided by the present invention are: the pulling and preparing device and method for controlling the volatilization of gallium-containing photofunctional crystals provided in the structure of the present invention adopt this multi-stage induction coil heating method to realize the gradual melting of the gallium-containing crystal melt from the crucible mouth to the crucible bottom as the crystal grows, avoiding the full-cycle melting of all gallium-containing crystals in the crucible, which leads to serious and uncontrollable volatilization of crystal melt components; at the same time, different heating powers can be set to provide different heating temperatures for gallium-containing crystals at different positions in the crucible, thereby controlling the melting state of the gallium-containing crystals. When growing gallium-containing crystals, the induction heating power of the feedback coil can be used according to the downward displacement of the solid-liquid interface of the polycrystalline raw material prepared from the gallium-containing crystals and the crystal growth rate to realize real-time movement of the solid-liquid interface, thereby avoiding volatilization defects during crystal growth of the gallium-containing crystals. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the structure of the pulling preparation device corresponding to the embodiment of growing GGG crystal in the present invention;

[0030] Figure 2 Schematic diagram of the structure of the pulling preparation device corresponding to the embodiment of growing TGG crystal in the present invention;

[0031] Among them, 1-crucible, 2-gallium-containing crystal, 3-heating mechanism, 4-pulling mechanism, 5-insulation layer, 31-coil, 41-seed crystal, 42-seed crystal rod, 311-first coil, 312-second coil, 313-third coil, 314-fourth coil, 315-fifth coil, 316-sixth coil, 317-seventh coil. DETAILED DESCRIPTION

[0032] The technical solutions of the present invention are described in detail below through specific embodiments. Numerous specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art may make similar modifications without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0033] like Figure 1 As shown, the pulling preparation device for controlling the volatilization of gallium-containing photofunctional crystals proposed in the present invention includes a crucible 1, a gallium-containing crystal 2 arranged in the crucible 1, a heating mechanism 3 for heating the gallium-containing crystal 2 and a pulling mechanism 4 for assisting the growth of the gallium-containing crystal 2. The pulling end of the pulling mechanism 4 extends into the crucible 1 and abuts against the gallium-containing crystal 2 arranged in the crucible 1. The heating mechanism 3 includes at least two heating units, and each heating unit is respectively wrapped around the outer circumference of the crucible 1.

[0034] Since gallium-containing crystals 2 are prone to volatilization of gallium oxide during crystal growth, which leads to the generation of crystal defects, in this application, a method is adopted in which the power of the heating unit gradually increases from the bottom of the crucible to the mouth of the crucible. By using this multi-segment induction heating method, the melt of the gallium-containing crystal 2 is gradually melted from the mouth of the crucible to the bottom of the crucible as the crystal grows, avoiding the serious volatilization and uncontrollable problems of the crystal melt components caused by the full-cycle melting of all the gallium-containing crystals 2 in the crucible 1.

[0035] It is also possible to set the concentration of gallium oxide in the gallium-containing crystal 2 to increase in a one-way gradient from the mouth of the crucible to the bottom of the crucible. This gallium-containing crystal 2 with a one-way change in concentration gradient can compensate for the volatilization of components and meet the requirements of the high-power laser technology and optical communication fields for large-size and high-quality gallium-containing optical functional crystals.

[0036] It should be noted that the gallium-containing crystal 2 described in this application can be Ga2O3, Gd3Ga5O 12 、Tb3Ga5O 12 、Y3Sc2Ga3O 12 、Gd3Sc2Ga3O 12 、Y3Ga5O 12 、Gd 3x Y 3(1-x) Sc2Ga3O 12 (0 < x < 1) one of the matrix crystals or a laser crystal formed after doping activation ions such as Yb 3+ 、Nd 3+ 、Er 3+ 、Tm 3+ 、Ho 3+ 、Pr 3+ 、Eu 3+ 、Sm 3+ 、Dy 3+ 、Ti 3+ 、Cr 3+ and so on.

[0037] In this embodiment, different heating units are successively attached and wound around the outer periphery of the crucible 1. The mouth of the crucible is flush with the uppermost end of one of the heating units, and the heating temperature of the heating unit at the mouth of the crucible is equal to the crystal melting point. Specifically, the heating unit includes a coil 31. The above different coils work independently of each other, and different heating temperatures can be provided for the gallium-containing crystals 2 at different positions in the crucible 1 by setting different heating powers. Furthermore, the molten state of the gallium-containing crystal 2 can be controlled. When crystal growth is carried out on the gallium-containing crystal 2, the induction heating power of the coil can be fed back according to the downward displacement of the solid-liquid interface of the polycrystalline raw material prepared from the gallium-containing crystal 2 and the crystal growth rate, realizing the real-time movement of the solid-liquid interface and avoiding the volatilization defects during the crystal growth of the gallium-containing crystal 2.

[0038] Specifically, the coils 31 in each heating unit have the same number of turns and diameter, and each heating unit is powered by a different power supply unit. The different coils are configured to be of consistent specifications, facilitating synchronous adjustment of the heating power of the different coils during the downward displacement of the solid-liquid interface of the polycrystalline raw material. Furthermore, the spacing between adjacent coils 31 in the same heating unit is equal to the spacing between adjacent coils 31 in different heating units. This avoids the defect of faulty heating of the gallium-containing crystals 2, allowing the gallium-containing crystals 2 to be stably melted and pulled from the bottom of the crucible to the crucible mouth.

[0039] It should be noted that, assuming the total number of coil segments is N, as the crystal grows, the time taken for each 1 / N drop in the melt height of the gallium-containing crystal 2 in the crucible 1 is T hours, and the power of the Nth coil segment rises uniformly to the power required for the melting point temperature of the gallium-containing crystal 2 within the NT time. Within each T time, the power adjustment of a single coil can be achieved by real-time detection of the weight of the crucible 1 and the gallium-containing crystal 2 therein, and adjustment is made based on the relationship between the increase in crystal weight per unit time and the theoretical weight increase. Assuming the growing crystal is cylindrical, the crystal growth rate is v, the crystal density is ρ, and the theoretical weight increase within the △T time is Δm s =πr 2 ×ν×ΔT×ρ, when the actual weight increase is greater than the theoretical weight increase, increase the power, otherwise, reduce the power.

[0040] In this embodiment, the pulling mechanism 4 includes a seed crystal 41 and a seed crystal rod 42. One end of the seed crystal rod 42 is inserted into the crucible 1 and fixed to the seed crystal 41. The end of the seed crystal 41, which is away from the seed crystal rod 42, abuts the upper end surface of the gallium-containing crystal 2. The seed crystal 41 can be cylindrical or rectangular. The gallium-containing crystal 2 is pulled and grown using the seed crystal 41, and the melt is directed along the crystallographic orientation of the seed crystal. High-quality seed crystals contain fewer impurities and defects, which can reduce defects in the grown crystal and improve crystal quality.

[0041] In this example, an insulation layer 5 is further provided on the outer periphery of the crucible 1, and the coil 31 is attached to the insulation layer 5 in sequence. The concentration of gallium oxide in the gallium-containing crystal 2 increases in a unidirectional gradient. A temperature field structure is provided on the outer side of the insulation layer 5. The temperature field structure can adopt insulation bricks or insulation cylinders made of zirconium oxide or aluminum oxide. A cylindrical temperature field or a rectangular cylindrical temperature field is constructed in combination with the length of the grown crystal. The crucible 1, the insulation layer 5, etc. are all in the constructed temperature field.

[0042] In this embodiment, the method for preparing gallium-containing photofunctional crystals by controlling volatilization thereof includes the following steps:

[0043] (A) The size of the crucible 1 is determined according to the size of the gallium-containing crystal 2, and at least two independent heating units are wound around the periphery of the crucible 1, and the different heating units are wound in sequence from the bottom of the crucible to the crucible mouth.

[0044] The pulling and preparing device for crystal growth refers to the description of the pulling and preparing device for controlling the volatilization of gallium-containing photofunctional crystals.

[0045] (B) preparing a plurality of polycrystalline raw materials containing gallium oxide in different proportions according to the type of gallium-containing crystals 2, wherein the polycrystalline raw materials are provided in a corresponding number to the number of the heating units;

[0046] The shape of the polycrystalline raw material is the same as that of the crucible 1, which is cylindrical or rectangular.

[0047] (C) placing the polycrystalline raw materials in a crucible 1 in sequence, with the gallium oxide ratio increasing unidirectionally from the crucible opening to the crucible bottom;

[0048] The crucible 1, coil 31, insulation layer 5, seed crystal 41, and seed crystal rod 42 are placed concentrically and coaxially. A plurality of polycrystalline raw materials are prepared, and the gallium oxide ratio thereof varies unidirectionally within the range of 0 to 10%. The polycrystalline raw materials containing different gallium oxides are placed in the crucible 1 in sequence according to the unidirectional increase of the gallium oxide ratio. In order to better control the crystal growth and volatilization of the polycrystalline raw materials, the number of polycrystalline raw materials can be set to be consistent with the number of coils 31. At the same time, the outer side of each polycrystalline raw material corresponds to a coil 31 for heating, so as to achieve control of the solid and molten states of different polycrystalline raw materials.

[0049] (D) The polycrystalline raw material in the crucible 1 is heated in sections by the heating unit, and the polycrystalline raw material in the crucible 1 is pulled and grown by the pulling mechanism 4 .

[0050] In this embodiment, for (D), the following steps are specifically included:

[0051] (D1) The crucible 1 is vacuumed. When the pressure in the furnace is less than 10 Pa, the protective gas Ar or N and less than 5% oxygen are filled to (1.0-1.8)×10 5 Pa;

[0052] The protective gas Ar or N is to protect the crucible 1 from being oxidized. Filling less than 5% of the furnace volume with oxygen can not only inhibit the decomposition of gallium oxide to a certain extent, but also prevent the oxidation of the crucible 1, thereby avoiding the oxidation of the crucible 1 affecting the growth of crystals.

[0053] (D2) using multi-stage induction heating for the coils 31 in different heating units, with the heating power of the coils 31 gradually increasing from the bottom of the crucible to the crucible mouth. The heating temperature of the heating unit at the crucible mouth is equal to the crystal melting point, and the polycrystalline raw material at the crucible mouth is melted;

[0054] The power of coil 31 at the crucible mouth can be set to 500-1000W higher than that of coil 31 at the crucible bottom. This power difference ensures that the lower portion of the material in crucible 1 is within a suitable temperature range, where it is molten but not melted. Heating by coil 31 causes the polycrystalline material at the crucible mouth to be molten, while the polycrystalline material below is molten (i.e., unmelted). This prevents the polycrystalline material below from volatilizing during crystal growth, thus controlling crystal volatilization.

[0055] (D3) slowly lowering the seed crystal 41 to the end surface of the molten polycrystalline raw material, and adjusting the heating power of the coil 31 until the seed crystal 41 and the end surface of the molten polycrystalline raw material are in stable contact for more than 0.2 hours;

[0056] Because the weight of the seed crystal 41 generally changes when it first contacts the molten polycrystalline raw material, increasing or decreasing, it is necessary to adjust the power at this time so that the weight of the seed crystal 41 in the molten polycrystalline raw material neither increases nor decreases. Therefore, the stable contact time between the seed crystal 41 and the end face of the molten polycrystalline raw material is set to be greater than 0.2h.

[0057] (D4) pulling and rotating the seed crystal 41 at a certain rate to grow the polycrystalline raw material;

[0058] The pulling preparation of crystal growth is achieved by pulling and rotating the seed rod 42, wherein the pulling and rotation of the seed rod 42 can be completed manually or mechanically, and the specific pulling speed and rotation speed can be set according to the specific polycrystalline raw material.

[0059] (D5) According to the downward displacement of the solid-liquid interface of the polycrystalline raw material and the crystal growth rate, the induction heating power of the feedback coil 31 is fed back to achieve real-time movement of the solid-liquid interface;

[0060] (D6) After the crystal growth is completed, the seed crystal rod 42 is pulled up at a certain rate to separate the crystal from the liquid surface in the crucible 1, and the crystal is cooled to room temperature before being taken out.

[0061] Through the above (A) to (D), the component volatilization problem in the current growth process of gallium-containing crystals 2 can be effectively suppressed, the stability of crystal growth is improved, and a new technical solution is provided for the growth of large-sized gallium-containing crystals, thereby achieving high-quality crystal growth and laying the foundation for large-sized, high-quality gallium-containing crystal materials for the development of laser technology and optical communications.

[0062] As an example, a three-stage induction heating coil is used to grow GGG (gadolinium gallium garnet) crystals with a crystal size of like Figure 1 As shown, a cylindrical crucible 1 is made of metal iridium, and the dimensions of the crucible 1 are an inner diameter of 60 mm and an inner height of 45 mm.

[0063] Steps for growing GGG crystals:

[0064] (11) Raw material preparation: High-purity Gd2O3 and Ga2O3 nanopowders were used as raw materials for the growth of GGG crystals. The raw materials were weighed according to a molar ratio of Gd2O3:Ga2O3=3:5, with Ga2O3 in excess of 0.5%, 1%, and 1.5%, respectively. Then, they were mixed in a high-frequency oscillating mixer for 24 hours and pressed into three Φ60mm×20mm block raw materials with excesses of 0.5%, 1%, and 1.5%, respectively. The blocks were calcined at 1200°C for 24 hours to obtain polycrystalline raw materials, which were used as the growth raw materials for GGG crystals.

[0065] (12) Seed crystal production: selection <111> The seed crystal 41 has a circular cross section and a diameter of about 6 mm. One end of the seed crystal 41 is fixedly connected to the seed crystal rod 42 and the other end is in contact with the polycrystalline raw material in the crucible 1.

[0066] (13) Furnace loading: A temperature field structure for growing crystals is constructed in the medium frequency single crystal pulling furnace. The crucible 1, the insulation layer 5, the coil 31, the seed crystal rod 42, and the seed crystal 41 are placed concentrically and coaxially. The polycrystalline raw material is loaded into the iridium crucible 1. The proportion of gallium oxide increases unidirectionally from the crucible mouth to the crucible bottom (0.5% → 1.0% → 1.5%).

[0067] (14) Crystal growth: Vacuum the furnace until the pressure inside is less than 10Pa, then fill with protective gas N2 and 2% of the furnace volume of O2 until the pressure inside the furnace is (1.0-1.8)×10 5Pa, so that the air pressure in the furnace is slightly positive, to prevent air from entering the furnace to oxidize the crucible 1, using three sections of induction heating coils 31 for induction heating, the three sections of coils 31 have the same number of turns, the distance between coils 31 and coils 31 is the same as the distance between each turn of coils 31, the total height of coils 31 is the same as the height of crucible 1, increase the power of the power supply, the load power of the first coil 311 is higher than the load power of the second coil 312 and the third coil 313 by 500W, observe through the observation window, and simultaneously increase the power of the three coils to melt the polycrystalline raw material at the crucible mouth first, and the raw materials in other parts are in a molten (non-melted) state, and slowly lower the seed The seed crystal 41 contacts the end face of the melted polycrystalline raw material, and the heating power of the first coil 311 is adjusted until the contact surface of the seed crystal 41 and the melted polycrystalline raw material is stable for more than 0.2h, and the weight signal of the electronic scale of the single crystal furnace remains basically unchanged. Then the seed crystal 41 is pulled at a rate of 0.5-1.5mm / h and rotated at 5-10rpm / min to grow the crystal. The use of the pulling rate of 0.5-1.5mm / h and the rotation speed of 5-10rpm / min can avoid the problems of long cycle, serious volatilization, and power consumption caused by too slow growth; the crystal pulled out due to fast growth may be polycrystalline and cannot be used, which affects the crystal quality.

[0068] From the start of automatic crystal growth to the time when the liquid level drops to 1 / 3 of the height of the crucible 1, the power of the second coil 312 is uniformly increased to the power required for melting the polycrystalline raw material; from the start of automatic crystal growth to the time when the liquid level drops to 2 / 3 of the height of the crucible 1, the power of the third coil 313 is uniformly increased to the power required for melting the raw material, thereby realizing real-time movement of the solid-liquid interface; when the actual grown length of the crystal reaches 80mm, the growth is completed, and then the crystal is separated from the liquid surface at a rate of 10-50mm / h. After observing that the signal of the electronic scale remains unchanged, it indicates that the pulling-off is completed, and then the temperature is lowered at 40-50℃ / h. The crystal is taken out after it cools to room temperature. The setting of the rate of 10-50mm / h avoids the problem that the pulling-off speed is too fast, and the crystal may crack due to the large temperature difference it is subjected to; if it is too slow, the pulling-off time will become too long.

[0069] As an example, a TGG (terbium gallium garnet) crystal is grown by induction heating using a four-stage induction heating coil. The crystal size is like Figure 2 As shown, a cylindrical crucible 1 is made of metal iridium, and its dimensions are an inner diameter of 90 mm and an inner height of 90 mm.

[0070] Steps for growing TGG crystals:

[0071] (21) Raw material preparation: High-purity Tb4O7 and Ga2O3 nanopowders were used as raw materials for TGG crystal growth. The raw materials were weighed according to a molar ratio of Tb4O7:Ga2O3 = 3:10, with Ga2O3 in excess of 0.5%, 1%, 1.5%, and 2.0%, respectively. Then, the raw materials were mixed in a high-frequency oscillating mixer for 24 hours and pressed into four Φ90 mm block raw materials with excesses of 0.5%, 1%, 1.5%, and 2.0%, respectively. The raw materials were calcined at 1250°C for 24 hours to obtain polycrystalline raw materials, which were used as the growth raw materials for TGG crystals.

[0072] The high-frequency oscillation mixer is used for mixing for 24 hours, mainly to improve the mixing uniformity; the setting of calcination at 1250°C for 24 hours is mainly to allow the block raw materials to become polycrystalline raw materials with the same phase as the crystal after calcination, which helps to reduce the volatilization of components.

[0073] (22) Seed crystal production: selection <111> The high-quality seed crystal 41 body has a circular cross section and a diameter of about 8 mm. One end of the seed crystal 41 is fixedly connected to the seed crystal rod 42 and the other end is in contact with the polycrystalline raw material in the crucible 1.

[0074] (23) Furnace loading: A temperature field structure for growing crystals is constructed in the medium frequency single crystal pulling furnace. The crucible 1, the insulation layer 5, the coil 31, the seed crystal rod 42, and the seed crystal 41 are placed concentrically and coaxially. The polycrystalline raw material is loaded into the iridium crucible 1. The proportion of gallium oxide increases unidirectionally from the crucible mouth to the crucible bottom (0.5% → 1.0% → 1.5% → 2.0%).

[0075] (24) Crystal growth: Vacuum the furnace until the pressure inside the furnace is less than 10Pa, then fill it with protective gas N2 and 2% of the furnace volume of O2 until the pressure inside the furnace is (1.0-1.8)×10 5Pa, heating is performed using four-segment induction heating coils. The four coils have the same number of turns, the distance between the coils is the same as the distance between each turn of the coil, and the total height of the coils is the same as the height of the crucible. The power of the power supply is increased, and the load power of the fourth coil 314 is higher than the load power of the fifth coil 315, the sixth coil 316, and the seventh coil 317. It can be set as high as 800W, mainly to make the power of the fourth coil higher than that of the other coils at a certain temperature; the power of the other three coils can be the same, or a certain power difference can be generated. If the power is the same, the complexity of the adjustment can be reduced. Observe through the observation window and increase the power of the four coils simultaneously to melt the raw material at the crucible mouth first, while the raw materials in other parts are in a molten (unmelted) state. Slowly lower the seed crystal 41 to contact the end face of the melted polycrystalline raw material. Adjust the heating power of the fourth coil 314 until the contact time between the seed crystal 41 and the melted polycrystalline raw material is stable for more than 0.2h, and the weight signal of the electronic scale of the single crystal furnace remains basically unchanged. Then, pull the seed crystal at a rate of 0.5-1.5mm / h and rotate it at 5-10rpm / min to grow the crystal. The use of the pulling rate of 0.5-1.5mm / h and the rotation speed of 5-10rpm / min can avoid problems such as long cycle, severe volatilization, and power consumption caused by too slow growth; the crystal pulled out due to fast growth may be polycrystalline and cannot be used, affecting the crystal quality.

[0076] From the start of automatic crystal growth until the liquid level drops to 1 / 4 of the crucible height, the power of the fifth coil 315 is uniformly increased to the power required to melt the polycrystalline raw material; from the start of automatic crystal growth until the liquid level drops to 2 / 4 of the crucible height, the power of the sixth coil 316 is uniformly increased to the power required to melt the polycrystalline raw material; from the start of automatic crystal growth until the liquid level drops to 3 / 4 of the crucible height, the power of the seventh coil 317 is uniformly increased to the power required to melt the polycrystalline raw material, thereby achieving real-time movement of the solid-liquid interface; when the actual grown length of the crystal reaches 100mm, growth is completed, and then the crystal is separated from the liquid surface at a rate of 10-50mm / h. When the weight signal of the electronic scale remains unchanged, it indicates that the pull-off is complete, and then the temperature is lowered at 40-50℃ / h to room temperature and the crystal is removed.

[0077] The rate is also set at 10 to 50 mm / h to avoid the defect that if the pulling speed is too fast, the crystal may crack due to the large temperature difference; if it is too slow, the pulling time will become too long.

[0078] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing gallium-containing photofunctional crystals by controlling the volatilization thereof, characterized in that: The pulling preparation method is implemented by using a pulling preparation device, the pulling preparation device comprising a crucible (1), a gallium-containing crystal (2) arranged in the crucible (1), a heating mechanism (3) for heating the gallium-containing crystal (2), and a pulling mechanism (4) for assisting the growth of the gallium-containing crystal (2), wherein the pulling end of the pulling mechanism (4) extends into the crucible (1) and abuts against the gallium-containing crystal (2) arranged in the crucible (1), and the heating mechanism (3) comprises at least two heating units; The specific pulling preparation method is: (A) determining the size of the crucible (1) according to the size of the gallium-containing crystal (2), and winding at least two independent heating units around the periphery of the crucible (1), wherein the different heating units are wound in sequence from the bottom of the crucible to the crucible mouth; (B) preparing a plurality of polycrystalline raw materials containing gallium oxide in different proportions according to the type of gallium-containing crystals (2), wherein the polycrystalline raw materials are provided in a corresponding number to the heating units; (C) placing the polycrystalline raw materials in a crucible (1) in sequence, with the gallium oxide ratio increasing in one direction from the crucible mouth to the crucible bottom; (D) heating the polycrystalline raw material in the crucible (1) in sections by the heating unit, and pulling and growing the polycrystalline raw material in the crucible (1) by the pulling mechanism (4), specifically including (D1) to (D6): (D1) Evacuate the crucible (1) and when the pressure inside the furnace is less than 10Pa, fill it with protective gas and less than 5% oxygen by volume to (1.0-1.8)×10 5 Pa; (D2) using multi-stage induction heating for the coils (31) in different heating units, and gradually increasing the heating power of the coils (31) from the bottom of the crucible to the crucible mouth, so that the heating temperature of the heating unit at the crucible mouth is equal to the crystal melting point, and the polycrystalline raw material at the crucible mouth is melted; (D3) slowly lowering the seed crystal (41) to the end surface of the molten polycrystalline raw material, and adjusting the heating power of the coil (31) until the seed crystal (41) and the end surface of the molten polycrystalline raw material have a stable contact time of more than 0.2 hours; (D4) pulling and rotating the seed crystal (41) at a certain rate to grow the polycrystalline raw material; (D5) according to the downward displacement of the solid-liquid interface of the polycrystalline raw material and the crystal growth rate, the induction heating power of the feedback coil (31) is fed back to realize the real-time movement of the solid-liquid interface; (D6) After the crystal growth is completed, the seed crystal rod (42) is pulled at a certain rate to separate the crystal from the liquid surface in the crucible (1), and the crystal is cooled to room temperature and then taken out.

2. The pulling preparation method according to claim 1, characterized in that: Different heating units are sequentially attached to the outer periphery of the crucible (1) and wound around it, the crucible opening is flush with the uppermost end of one of the heating units, and the heating temperature of the heating unit at the crucible opening is equal to the melting point of the crystal; The power of the heating unit gradually increases from the bottom of the crucible to the crucible mouth, and the gallium oxide concentration in the gallium-containing crystal (2) decreases in a unidirectional gradient.

3. The pulling preparation method according to claim 2, characterized in that: The heating unit comprises a coil (31), and the spacing between adjacent wound coils (31) in the same heating unit is equal to the spacing between adjacent coils (31) in different heating units; The coils (31) in each heating unit have the same number of turns and the same diameter, and each heating unit is powered by a different power supply unit.

4. The pulling preparation method according to claim 3, characterized in that: The pulling mechanism (4) comprises a seed crystal (41) and a seed crystal rod (42), one end of the seed crystal rod (42) is inserted into the crucible (1) and fixed to the seed crystal (41), and the seed crystal (41) abuts against the upper end surface of the gallium-containing crystal (2) at one end away from the seed crystal rod (42).

5. The pulling preparation method according to any one of claims 1 to 4, characterized in that: The outer periphery of the crucible (1) is further provided with a heat-insulating layer (5), and the heating units are sequentially arranged in contact with the heat-insulating layer (5).

6. The pulling preparation method according to claim 1, characterized in that: After preparing polycrystalline raw materials in (B), select <111> A high-quality seed crystal (41) blank of the same type as the matrix is ​​provided in the same direction, wherein the cross section of the seed crystal (41) blank is circular or rectangular, and one end thereof is fixedly connected to the seed crystal rod (42).

7. The pulling preparation method according to claim 1, characterized in that: When multi-stage induction heating is respectively adopted for the coils (31) in different heating units, the power of the coil (31) at the crucible mouth is 500-1000W higher than the power of the coil (31) at the crucible bottom.

8. The pulling preparation method according to claim 1, characterized in that: In (C), the polycrystalline raw materials are placed in a crucible (1) in sequence, and the gallium oxide ratio increases unidirectionally from the crucible mouth to the crucible bottom; the gallium oxide ratio changes unidirectionally within the range of 0-10%.

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