Device and method for crystal growth

Abstract

The invention discloses a device and a method for crystal growth. The device comprises a vacuum furnace body system; the double-area heater comprises an upper heater and a lower heater which can be independently controlled, and the double-area heater is arranged in the furnace body and used for adjusting the temperature of the upper area and the temperature of the lower area to form the needed temperature gradient; the heat preservation structure is arranged in the furnace chamber and cooperates with the double-zone heater to form a stable upper high-temperature zone, a stable middle gradient zone and a stable lower low-temperature zone; the multi-rod crucible assembly is arranged in the thermal field in the thermal insulation structure and has the characteristic of symmetrical arrangement; and the crucible lifting mechanism is connected to the multi-rod crucible assembly and is used for adjusting the position of the crucible in the crystal growth process. According to the invention, the stability of the temperature field, the simplification of the structure and the reduction of the cost are realized, and the stress concentration is effectively reduced. Meanwhile, the method supports high-throughput crystal growth, increases the degree of freedom of growth crystal specifications, improves the component screening efficiency, shortens the crystal research and development period, and improves the production efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of single crystal growth, and in particular to a device and method for crystal growth. Background Art

[0002] Fluoride crystals have a large bandgap, high transmittance, low refractive index and low light reflection coefficient in the ultraviolet, visible and infrared spectral regions. They are the best vacuum ultraviolet optical materials and are widely used in the production of ultraviolet and infrared windows, lenses and prisms. Fluoride laser crystals can be formed by doping active ions into the fluoride matrix. Fluoride crystals such as barium fluoride, cerium fluoride and lead fluoride are important scintillators or Cherenkov radiators and are widely used in fields such as nuclear physics and particle physics. Different applications have different requirements for fluoride crystals, and the specifications, components and doping amount of the crystals need to be adjusted according to the needs. For example, barium fluoride crystal is a sub-nanosecond ultrafast decay scintillator, but the crystal also has a slow scintillation decay component that causes signal accumulation in high-count applications. Selective doping is an effective way to suppress its slow scintillation luminescence component. In order to determine the optimal doping amount and process, the existing growth devices and methods require multiple rounds of long-term formula screening and doping process exploration, which is inefficient, costly and long-term.

[0003] At present, domestic and foreign reports on the production of fluoride crystals mainly use a single-heated crucible descent method for crystal growth. However, fluoride crystals have a large expansion coefficient and poor impact resistance, and are easily affected by the accumulation of thermal stress during the growth process, resulting in severe cracking during cooling and processing. For fluoride crystals that require doped ions (such as yttrium-doped barium fluoride crystals), the introduction of doped ions and the increase in doping amount will also introduce component stress during the growth process, making high-doped fluorides more susceptible to stress cracking. In addition, due to the influence of the segregation effect of doped ions in the crystal, a molten zone with a higher doping concentration is often formed at the tail end of the growing crystal, which makes the influence of component stress greater, causing more serious crystal cracking problems and reducing crystal utilization. In addition, for the component screening process of doped fluorides, it is necessary to comprehensively consider multiple factors such as the growth cycle and the difficulty of the growth process in terms of crystal preparation. Usually, a multi-station crucible is used to reduce time and growth costs.

[0004] In the existing multi-station growth technology, there are traditional single-crucible multi-station growth methods, inner and outer dual-zone heating outer ring porous crucibles (Chinese patent CN11633456A), and multiple growth crucibles isolated from each other (Chinese patent CN117344371A). Among them, the traditional multi-station crucible usually uses a large single crucible with multiple growth stations, and different stations grow crystals of the same component to meet the needs of industrial production, but it is not suitable for the process conditions of "growing crystals of different components in the same furnace" in the component screening process.

[0005] The inner and outer dual-zone heating ring porous crucible is limited by the ring size, and the degree of freedom for component screening is not high enough. The mutually isolated multiple crucible growth system sets an independent insulation layer for each crucible, which has a large working space requirement and many restrictions. Summary of the invention

[0006] The present invention provides a device and method for crystal growth, aiming to solve the cracking problem caused by stress accumulation during the growth of non-doped and doped fluoride crystals in the prior art, as well as the technical bottleneck of high-throughput component rapid screening. The device achieves temperature field stability, structural simplification and cost reduction through independently controlled dual-zone heating and multi-rod crucible technology, effectively reducing stress accumulation. At the same time, the method supports high-throughput crystal growth, increases the degree of freedom of growing crystal specifications, improves component screening efficiency, shortens the crystal R&D cycle, and improves production efficiency.

[0007] According to a first aspect of the present invention, there is provided an apparatus for crystal growth, the apparatus comprising:

[0008] A vacuum furnace system for providing a controlled environment and having a cooling structure;

[0009] A dual-zone heater, comprising two independently controllable upper and lower heaters, the dual-zone heater being arranged in the furnace body and used to adjust the temperatures of the upper and lower zones respectively to form a desired temperature gradient;

[0010] The heat preservation structure is arranged in the furnace cavity and cooperates with the double-zone heater to form an upper high-temperature zone, a middle gradient zone and a lower low-temperature zone, thereby ensuring the stability and uniformity of the overall temperature field;

[0011] The multi-rod crucible assembly is arranged in the temperature field within the insulation structure and has the characteristics of symmetrical arrangement, ensuring the mutual independence and stable operation of the multi-rod crucibles to achieve the simultaneous growth of crystals of multiple components or different specifications;

[0012] The crucible lifting mechanism, connected to the multi-rod crucible assembly, is used to adjust the position of the crucible during the crystal growth process to optimize the temperature distribution and growth conditions.

[0013] In some technical solutions, the multi-rod crucible assembly includes a multi-rod crucible, a base and a tray connected in sequence from top to bottom;

[0014] The crucible lifting mechanism includes a support column and a descending transmission device, the support column is connected to the tray and is connected to the descending transmission device, and the descending transmission device is used to drive the support column to move up and down to adjust the height of the multi-rod crucible during the crystal growth process;

[0015] The bottom of the crucible is provided with a temperature measuring thermocouple which moves with the crucible or moves freely, so as to realize real-time temperature monitoring and feedback.

[0016] In some technical solutions, the multi-rod crucibles have the same size and are symmetrically arranged on the tray. The center of the crucible is located on a concentric circle with the center in the middle of the tray. The crucible can be arranged in a single circle, two circles inside and outside, or multiple circles according to its size.

[0017] In some technical solutions, the multi-rod crucible is provided with an explosion-proof valve. When the pressure difference between the inside and outside of the crucible is less than a preset threshold, the crucible is kept relatively closed. When the pressure difference exceeds the preset threshold, the explosion-proof valve automatically opens to release the gas in the crucible.

[0018] In some technical solutions, the insulation structure includes upper and lower insulation layers and an insulation ring. The height and position of the upper and lower insulation layers are adjusted according to multi-rod crucibles of different specifications, and the height of the insulation ring can be adjusted according to crucibles of different sizes and specific crystal growth needs.

[0019] In some technical solutions, the insulation structure includes an insulation cover, an upper insulation barrel, an insulation ring, a lower insulation barrel, an insulation base and a support ring, the insulation cover, the upper insulation barrel and the insulation ring together form an upper insulation layer, and the insulation ring, the lower insulation barrel and the insulation base together form a lower insulation layer; and / or,

[0020] The thermal insulation structure is made of graphite material; and / or,

[0021] The thickness of the thermal insulation structure is not less than 30 mm.

[0022] In some technical solutions, the vacuum furnace body system is mainly composed of a double-layer structure of a furnace cover, an upper furnace cavity shell, a lower furnace cavity shell and a furnace bottom plate, and a cooling water channel is provided inside; the vacuum furnace body system also includes a furnace shell lifting mechanism connected to the furnace cover and the upper furnace cavity shell, and a vacuum pipe connected to the furnace cavity.

[0023] In some technical solutions, the device also includes an atmosphere control system, which is connected to the vacuum furnace system. The vacuum furnace system provides and adjusts the required atmosphere environment through the atmosphere control system, so that the device can operate in a variety of environments such as vacuum, inert gas and fluorine-containing gas, ensuring that the atmosphere composition and pressure inside the cavity are stable within a preset range, so as to adapt to different crystal growth conditions and improve the growth quality of the crystal.

[0024] In some technical solutions, the upper heater and the lower heater are both graphite heaters, and the graphite heaters are connected to metal electrodes through graphite rods and connected to external power supply lines to achieve heating and power control.

[0025] According to another aspect of the present invention, there is further provided a method for growing a crystal using the above-mentioned device, comprising the following steps:

[0026] According to the growth composition and final size requirements, multiple groups of raw materials, dopants and deoxidizers in predetermined proportions are mixed and loaded into a multi-rod crucible, and the crucible is placed on a tray;

[0027] Adjust the layout of the dual-zone heater, assemble the insulation structure, close the vacuum chamber, start the vacuum acquisition system to pump the vacuum chamber to a preset vacuum degree and maintain it, or replenish the preset atmosphere to a preset atmosphere pressure according to the crystal growth conditions;

[0028] Start the heating program, raise the temperature of the upper heater and the lower heater simultaneously to the preset desorption temperature of 200-400°C for dehydration, adsorption of oxygen and other volatiles, and maintain it for 1-5 hours, so that the moisture, adsorption of oxygen and other volatiles are fully removed; then raise the temperature to 700-1000°C for the reaction of the deoxidizer with the oxygen-containing components in the raw material, and maintain it for 1-10 hours;

[0029] Continue to adjust the temperature of the upper heater to 50-200°C higher than the melting point of the crystal, and raise the temperature of the lower heater to 200-300°C lower than the melting point of the crystal, and keep it for a period of time to allow the raw materials to fully melt, and then start to grow downward at a preset speed;

[0030] When it descends to a preset distance, it stops descending and starts a preset cooling program. When the temperature drops to room temperature, the vacuum acquisition system and the atmosphere control system are turned off, the furnace cavity is opened, and multiple ingots are taken out from multiple independent crucibles.

[0031] In some technical solutions, ingots of different sizes can be obtained in the same growth furnace; and / or,

[0032] In the same growth furnace, multiple non-doped and doped crystal rods with different components can be obtained, thereby realizing high-throughput screening of doping components and doping amounts.

[0033] The present invention adopts the above technical solution to have at least the following beneficial effects:

[0034] 1. The present invention forms a stable temperature field by adding a graphite insulation structure with a certain thickness to the device and arranging a dual-zone heater with upper and lower independent controls in the structure. In particular, the thermal stress accumulation caused by excessive temperature gradient changes during crystal growth and cooling is significantly reduced, thereby improving the crystal's ability to withstand component stress and reducing the risk of crystal cracking.

[0035] 2. Compared with the traditional multi-station crucible and the new porous crucible design, the multi-rod crucible of the present invention has a higher degree of freedom because the crucibles are independently detachable from each other. The split structure of the furnace shell is convenient for adjusting the structure inside the furnace. At the same time, the separate design of the graphite insulation layer makes the height of the upper and lower insulation layers flexible and adjustable to adapt to crucibles and crucible bases of different sizes, thereby achieving the growth of crystals of different diameters and lengths. The device can obtain non-doped and doped crystal rods of different sizes and components in the same furnace, realizing high-throughput screening of doped components and optimal doping amounts;

[0036] 3. The multi-rod crucible of the present invention is equipped with an explosion-proof valve structure, which can extract the atmosphere in the crucible when evacuating the vacuum, and the explosion-proof valve falls during the growth to keep the crucible relatively closed, greatly reducing the impact of mutual contamination between components in each crucible;

[0037] 4. The height and position of the upper and lower insulation layers and the insulation ring of the insulation structure of the present invention are adjustable, providing flexible adjustment space, so that the device can adapt to crucibles of different specifications and growth requirements, ensuring precise control of the temperature gradient, reducing heat energy loss, and improving the insulation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings and their marks required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0039] Figure 1 It is a schematic diagram of the structure of the device for crystal growth of the present application;

[0040] Figure 2 In one embodiment of the present application, the lower heating temperature control is adjusted under the same conditions as the upper heating temperature control to obtain a crystal growth temperature curve;

[0041] Figure 3 This is a top view schematic diagram of a central graphite tray structure of 12 crystal rods in a single furnace in one embodiment of the present application;

[0042] Figure 4 This is a physical picture of a two-inch barium fluoride and yttrium-doped barium fluoride ingot grown under double heating conditions in an embodiment of the present application;

[0043] Figure 5 This is a physical picture of stress cracking of two inches of yttrium-doped barium fluoride grown under closed heating conditions to simulate single heating conditions in an embodiment of the present application;

[0044] Figure 6 This is a real picture of a 1-inch co-doped barium fluoride single crystal grown in one embodiment of the present device.

[0045] The meanings of the symbols in the figure are as follows:

[0046] 1—furnace cover, 2—upper furnace chamber shell, 3—lower furnace chamber shell, 4—furnace bottom plate, 5—insulation cover, 6—upper insulation barrel, 7—insulation ring, 8—lower insulation barrel, 9—upper heater, 10—lower heater, 11—multi-rod crucible, 12—base, 13—tray, 14—furnace shell lifting mechanism, 15—upper graphite support column, 16—lower metal support column, 17—vacuum pipe. DETAILED DESCRIPTION

[0047] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings and other implementation methods can be obtained based on these drawings without creative work.

[0048] In order to simplify the drawings, only the parts related to the invention are schematically shown in each figure, and they do not represent the actual structure of the product. In addition, in order to simplify the drawings and facilitate understanding, in some figures, only one of the parts with the same structure or function is schematically drawn or marked. In this article, "one" not only means "only one", but also means "more than one".

[0049] It should be further understood that the term “and / or” used in the specification and appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0050] In the description of the present application, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "axial", "radial", "circumferential", "lateral", "longitudinal" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0051] In this document, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0052] Example 1

[0053] like Figure 1 , showing a device for crystal growth, the device includes a vacuum furnace system, a dual-zone heater, a heat preservation structure, a multi-rod crucible assembly and a crucible lifting mechanism, wherein,

[0054] The vacuum furnace system is used to provide a controlled environment and has a cooling structure, specifically including a furnace cover 1, an upper furnace cavity shell 2, a lower furnace cavity shell 3, a furnace bottom plate 4 and a vacuum pipe 17 connected to the lower furnace cavity shell wall. The upper and lower furnace cavity shells, the furnace cover 1 and the furnace bottom plate 4 are all double-layer structures, and the internal interlayer is embedded with a cooling water channel to maintain temperature stability and prevent heat loss; the vacuum pipe 17 is connected to the system to achieve precise vacuum adjustment to ensure a controlled growth environment. The cavity pressure range is adjustable from vacuum, negative pressure to positive pressure during crystal growth.

[0055] The dual-zone heater includes two independently controllable upper heaters 9 and lower heaters 10. The upper and lower heaters are arranged in the furnace body to adjust the temperature of the upper and lower zones respectively to form the required temperature gradient. The upper and lower heaters are temperature controlled by temperature-controlled thermocouples placed on the outside thereof, and power control can also be performed directly. The diameter, length and relative position of the upper and lower heaters in the vacuum furnace body can be flexibly adjusted according to the size and number of the crucibles. Specifically, in one embodiment of the device, the upper and lower heaters are 150 mm long and 95 mm in inner diameter, and are respectively distributed on both sides of the insulation ring 7 in the vacuum furnace body.

[0056] The insulation structure includes an insulation cover 5 made of graphite, an upper insulation barrel 6, an insulation ring 7, a lower insulation barrel 8, an insulation base and a support ring; the insulation structure is used in conjunction with a dual-zone heater to form a stable distribution of an upper high-temperature zone, a middle gradient zone and a lower low-temperature zone. Figure 2 In order to control the dual-zone heater, while keeping the temperature of the upper heater 9 unchanged, the temperature field distribution at different positions obtained by adjusting the temperature control of the lower heater 10 is adjusted respectively.

[0057] The multi-rod crucible assembly is arranged in the temperature field within the insulation structure and has the characteristics of symmetrical arrangement, ensuring the mutual independence and stable operation of the multi-rod crucibles 11 to achieve the simultaneous growth of crystals of multiple components or different specifications; specifically, it includes a multi-rod crucible 11, a base 12 and a tray 13 connected in sequence from top to bottom, the multi-rod crucible 11 and the base 12 are combined by a mosaic structure, and the base 12 and the tray 13 are combined by threads; there is a temperature measuring thermocouple at the bottom of the crucible that moves with the crucible or moves freely.

[0058] The crucible lifting mechanism is connected to the multi-rod crucible assembly and is used to adjust the position of the crucible during the crystal growth process to optimize the temperature distribution and growth conditions; it specifically includes a support column and a descending transmission device (not shown in the figure), the support column is connected to the tray 13 and is connected to the descending transmission device, and the descending transmission device is used to drive the support column to move up and down to adjust the height of the multi-rod crucible 11 during the crystal growth process.

[0059] According to the present invention, through the temperature control of the upper and lower heaters in the upper and lower insulation layers in the insulation structure in the outer furnace cavity, a suitable temperature gradient is established in the middle gradient zone, and the temperature uniformity in the upper and lower insulation layers is guaranteed. Due to the existence of the multi-layer insulation structure, the internal temperature field is more stable, and the solid-liquid interface of the crystal is controlled to remain in the gradient zone at a suitable drop rate, which is conducive to reducing the accumulation of thermal stress during the growth process; for the growth of doped crystals, it is also conducive to reducing the accumulation of component stress of high-concentration doped ions in the uneven growth area, thereby reducing crystal cracking and facilitating the growth of large-sized, high-optical uniformity crystals.

[0060] According to the present invention, the relative positions of the multi-rod crucibles 11 in the temperature field are symmetrical, the insulation structure ensures the uniformity of the overall temperature field, the dual-zone heating ensures the stability of the growth process, and the symmetrical distribution of the multi-rod crucibles 11 without interfering with each other is conducive to the high-throughput simultaneous growth of doped barium fluoride crystals with different component concentrations, thereby reducing the time cost of the screening process.

[0061] Specifically, the multi-rod crucibles 11 of the same size can be symmetrically arranged on the tray 13, with the center of the crucible located on a concentric circle with the center in the middle of the tray. The crucibles can be arranged in a single circle, inner and outer circles, or multiple circles according to their size. Figure 3 The diagram is a top view of a central graphite tray structure for 12 crystal rods in a single furnace. In this embodiment, the symmetrical arrangement of the multi-rod crucible 11 on the tray 13 increases the uniformity of the system and the stability of the temperature field distribution, achieving consistency of multiple crystal growth conditions in the temperature field, facilitating high-throughput growth of crystals of multiple different components, improving component screening efficiency, and meeting the needs of efficient experiments and production.

[0062] Preferably, in the embodiment of the present application, the multi-rod crucible 11 is also provided with an explosion-proof valve structure. When the pressure difference between the inside and outside of the crucible is less than the valve gravity, the crucible is kept relatively closed, and the components can be isolated from each other to avoid the influence of mutual contamination between the components of the crucibles; when the vacuum is evacuated or the melt inside the crucible melts and generates gas, the pressure inside the crucible is relatively high, and the explosion-proof valve is lifted to release the gas in the crucible.

[0063] Specifically, the insulation cover 5, the upper insulation barrel 6, the insulation ring 7, the lower insulation barrel 8, the insulation base and the support ring in the insulation structure, the upper heater 9 and the lower heater 10 in the dual-zone heater, and the multi-rod crucible assembly are all made of graphite, and the support column in the crucible lifting mechanism is divided into an upper graphite support column 15 located inside the furnace chamber and a lower metal support column 16 located outside the furnace chamber, and cooling water is circulated inside the lower metal support column.

[0064] Preferably, in the embodiment of the present application, the insulation structure in the furnace cavity has a wall thickness of the insulation cover 5, the upper and lower insulation barrels, and the insulation ring 7 of not less than 30 mm, which can ensure radial uniform distribution of the temperature field under high temperature conditions, reduce thermal stress accumulation, and improve the stability and production efficiency of the growth process.

[0065] Specifically, the upper heater 9 and the lower heater 10 are both graphite heaters, which are connected to metal electrodes through graphite rods and connected to external power supply lines to achieve heating and power control. The metal electrodes are externally connected to water cooling that is insulated from the electrodes to achieve cooling of the electrodes.

[0066] Preferably, the vacuum furnace system of this embodiment further comprises a furnace shell lifting mechanism 14 connected to the furnace cover 1 and the upper furnace chamber shell 2. This design improves the operating convenience and safety of the device, facilitates loading and maintenance, and realizes flexible adjustment under different experimental conditions, protecting the growing crystals and equipment from abnormal pressure or operating risks.

[0067] Due to the split design of the furnace chamber, the adjustable space design of the insulation structure, and the adjustable design of the crucible and the crucible support structure of the present invention, according to the present invention, the upper and lower insulation layers in the graphite insulation structure are highly flexibly adjustable to adapt to crucibles and bases 12 of different sizes, thereby achieving the growth of crystals of different diameters and lengths.

[0068] Specifically, according to the present invention, the device also includes an atmosphere control system, which is connected to the vacuum furnace system. The vacuum furnace system provides and adjusts the required atmosphere environment through the atmosphere control system, so that the device can operate in a variety of environments such as vacuum, inert gas and fluorine-containing gas, ensuring that the atmosphere composition and pressure inside the cavity are stable within a preset range to adapt to different crystal growth conditions and improve the growth quality of the crystal.

[0069] The present invention provides a dual-zone heating device for obtaining crystal rods of different sizes in the same growth furnace, and can also be used to obtain multiple non-doped and doped crystal rods in the same growth furnace to achieve high-throughput doping concentration screening. Specifically, in one embodiment of the device, two-inch diameter crystal rods with four different doping concentrations are grown in the same furnace.

[0070] Example 2

[0071] Using the apparatus described in Example 1, four rods of two-inch yttrium-doped barium fluoride crystals were grown by dual-zone heating, and the yttrium doping concentrations of the four rods of barium fluoride crystals were 1at%, 2at%, 5at%, and 10at%, respectively.

[0072] (1) Weigh BaF according to the ratio 2 With YF 3 Raw materials, and then weigh 0.5wt% PbF 2 The raw materials are used as deoxidizers. After being mixed evenly, they are added into independent multi-rod crucibles 11 respectively. The crucible cover structure is screwed tight along the threads. The four-hole tray 13 is connected to the middle support rod by threads. The corresponding bases 12 of the four two-inch crucibles are connected to the tray 13 by threads. Then, the multi-rod crucibles 11 are placed one by one on the multiple bases 12 on the tray 13 in the vacuum descending furnace.

[0073] (2) Adjust the positions of the upper and lower heaters, assemble the insulation structure, close the vacuum chamber, and start the vacuum acquisition system to pump the vacuum chamber to the preset high vacuum degree of 1×10 -4 Pa;

[0074] (3) Start the heating program, raise the upper and lower heaters to the preset desorption temperatures of dehydration, adsorbed oxygen and other volatiles (upper heating 300°C, lower heating 200°C), and maintain for a period of time to fully remove moisture, adsorbed oxygen and other volatiles; then raise the temperature to the temperature at which the deoxidizer reacts with the oxygen-containing components in the raw material (upper heating 950°C, lower heating 700°C), and maintain for 1-10 hours; continue to raise the temperature of the upper heater 9 to 1418°C, and the lower heater 10 to 1168°C, and maintain for a period of time to fully melt the raw material, and then start to descend and grow at a preset speed of 2mm / h;

[0075] (4) When the furnace descends to a preset distance, the descent is stopped and a preset cooling program is started. When the temperature drops to room temperature, the vacuum acquisition system is turned off, the furnace cavity is opened, and a plurality of doped barium fluoride crystal ingots are taken out from a plurality of independent crucibles.

[0076] The obtained doped barium fluoride crystal has an equal diameter of ф50.8×100mm 3 The crystal was polished on the opposite side and the transmittance at 220nm was measured to be >80%. Figure 4This is a physical picture of the 2-inch barium fluoride and yttrium-doped barium fluoride crystals grown in one embodiment of the device.

[0077] Example 3

[0078] The apparatus described in Example 1 was used, and the growth method was the same as that in Example 2, except that the multi-rod crystal grown by dual-zone heating was a two-inch four-rod yttrium-doped barium fluoride crystal, and the yttrium doping concentrations were 5at%, 10at%, 15at%, and 20at%, respectively. The upper and lower heater temperatures in the descending growth stage were set to 1418°C / 1068°C; the growth atmosphere was nitrogen, and the preset atmosphere pressure was a slightly positive pressure of 1.3×10 5 Pa.

[0079] Example 4

[0080] The apparatus described in Example 1 was used, and the growth method was the same as that in Example 2, except that the multi-rod crystal grown by the dual-zone heating was a two-inch four-rod yttrium-doped barium fluoride crystal, and the yttrium doping concentrations were 7.5at%, 7.5at%, 15at%, and 15at%, respectively. The upper and lower heater temperatures in the descending growth stage were set to 1418°C / 968°C; the growth atmosphere was carbon tetrafluoride (CF 4 ), the preset atmosphere pressure is atmospheric pressure 1×10 5 Pa.

[0081] Example 5

[0082] The apparatus described in Example 1 was used, and the growth method was the same as that in Example 2, except that the lower heating was turned off to simulate the single heating growth conditions in the past. The multi-rod crystals grown by the single-zone heating were two-inch four-rod yttrium-doped barium fluoride crystals, and their yttrium doping concentrations were 7.5at%, 15at%, 7.5at%, and 15at%, respectively. In the descending growth stage, the temperatures of the upper and lower heaters were set to 1418°C / off. Figure 5 This is a physical picture of the stress cracking of 2-inch yttrium-doped barium fluoride obtained by simulating single heating growth with the lower heating turned off in this device embodiment, and Figure 4 Compared with the crystals grown under double heating conditions, Figure 5 Under the single heating condition, thermal stress accumulates in the crystal. At the same time, due to the high concentration of component selection, the crystal growth is more uneven, and more cracks are generated in the latter part of the crystal.

[0083] Example 6

[0084] The apparatus described in Example 1 was used, and the growth method was the same as that in Example 2, except that the multi-rod crystals grown by the dual-zone heating were two-inch two-rod calcium fluoride crystals and two-rod barium fluoride crystals, and the upper and lower heater temperatures in the descending growth stage were set to 1450°C / 1200°C; the growth atmosphere was argon, and the preset atmosphere pressure was a slight negative pressure of 10 3 Pa.

[0085] Example 7

[0086] The apparatus described in Example 1 was used, and the growth method was the same as in Example 2, except that the multi-rod crystal grown by dual-zone heating was a two-inch four-rod magnesium fluoride crystal, and the temperatures of the upper and lower heaters in the descending growth stage were set to 1311°C / 1061°C.

[0087] Example 8

[0088] The apparatus described in Example 1 was used, and the growth method was the same as that in Example 2, except that the multi-rod crystal grown by dual-zone heating was 12 rods of 1-inch single-doped and co-doped barium fluoride crystals, and different components of deoxidizers and doping components were added to different multi-rod crucibles. The components of the 12 crucibles were: BaF 2 Add 0wt% PbF 2 Deoxidizer, BaF 2 Add 0.1wt% PbF 2 Deoxidizer, BaF 2 Add 0.3wt% PbF 2 Deoxidizer, BaF 2 Add 0.5wt% PbF 2 Deoxidizer, BaF 2 Add 0.7wt% PbF 2 Deoxidizer, BaF 2 Single doped 1at% YF 3 And add 0.5wt% PbF 2 Deoxidizer, BaF 2 Co-doped with 1at% YF 3 with 1at% NaF and 0.5wt% PbF 2 Deoxidizer, BaF 2 Co-doped with 1at% YF 3 With 1at% KF and 0.5wt% PbF 2 Deoxidizer, BaF 2 Co-doped with 1at% YF 3 With 1at% LiF and 0.5wt% PbF 2 Deoxidizer, BaF 2 Co-doped with 2at% YF 3 With 2at% NaF and 0.5wt% PbF 2 Deoxidizer, BaF 2 Co-doped with 2at% YF 3 With 2at% KF and 0.5wt% PbF 2 Deoxidizer, BaF 2 Co-doped with 2at% YF 3 With 2at% LiF and 0.5wt% PbF 2Deoxidizer, the temperature of the upper and lower heaters in the descending growth stage is set to 1418℃ / 1168℃; the growth atmosphere is nitrogen trifluoride (NF 3 ), the preset atmosphere pressure is slightly negative pressure 10 3 Pa.

[0089] Example 9

[0090] The apparatus described in Example 1 was used, and the growth method was the same as that in Example 2, except that the multi-rod crystal grown by dual-zone heating was a one-inch nine-rod single-doped and co-doped barium fluoride crystal, and different components of deoxidizer and doping components were added to different multi-rod crucibles. The components of the nine crucibles were: BaF 2 Co-doped with 2at% YF 3 With 2at% NaF and 0.5wt% PbF 2 Deoxidizer, BaF 2 Co-doped with 2at% YF 3 With 2at% KF and 0.5wt% PbF 2 Deoxidizer, BaF 2 Co-doped with 2at% YF 3 With 2at% LiF and 0.5wt% PbF 2 Deoxidizer, BaF 2 Co-doped with 5at% YF 3 With 5at% NaF and 0.5wt% PbF 2 Deoxidizer, BaF 2 Co-doped with 5at% YF 3 With 5at% KF and 0.5wt% PbF 2 Deoxidizer, BaF 2 Co-doped with 5at% YF 3 With 5at%LiF and 0.5wt%PbF 2 Deoxidizer, BaF 2 Co-doped with 10at% YF 3 With 10at% NaF and 0.5wt% PbF 2 Deoxidizer, BaF 2 Co-doped with 10at% YF 3 With 10at% KF and 0.5wt% PbF 2 Deoxidizer, BaF 2 Co-doped with 10at% YF 3 With 10at%LiF and 0.5wt%PbF 2 Deoxidizer, the upper and lower heater temperatures in the descending growth stage are set to 1418℃ / 1168℃. Figure 6 This is a real picture of a 1-inch co-doped barium fluoride single crystal grown in one embodiment of the present device.

[0091] Table 1 shows the growth process parameters of the crystal in the embodiment of the present invention.

[0092]

[0093]

[0094] The above embodiments are only used to illustrate the present invention rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding application from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A device for crystal growth, characterized in that: The device comprises: A vacuum furnace system for providing a controlled environment and having a cooling structure; A dual-zone heater, comprising two independently controllable upper and lower heaters, the dual-zone heater being arranged in the furnace body and used to adjust the temperatures of the upper and lower zones respectively to form a desired temperature gradient; The heat preservation structure is arranged in the furnace cavity and cooperates with the double-zone heater to form an upper high-temperature zone, a middle gradient zone and a lower low-temperature zone, thereby ensuring the stability and uniformity of the overall temperature field; The multi-rod crucible assembly is arranged in the temperature field within the insulation structure and has the characteristics of symmetrical arrangement, ensuring the mutual independence and stable operation of the multi-rod crucibles to achieve the simultaneous growth of crystals of multiple components or different specifications; The crucible lifting mechanism, connected to the multi-rod crucible assembly, is used to adjust the position of the crucible during the crystal growth process to optimize the temperature distribution and growth conditions.

2. The device according to claim 1, characterized in that The multi-rod crucible assembly comprises a multi-rod crucible, a base and a tray which are sequentially connected from top to bottom; The crucible lifting mechanism includes a support column and a descending transmission device, the support column is connected to the tray and is connected to the descending transmission device, and the descending transmission device is used to drive the support column to move up and down to adjust the height of the multi-rod crucible during the crystal growth process; The bottom of the crucible is provided with a temperature measuring thermocouple which moves with the crucible or moves freely, so as to realize real-time temperature monitoring and feedback.

3. The device according to claim 2, characterized in that The multi-rod crucibles have the same size and are symmetrically arranged on the tray. The center of the crucible is located on a concentric circle whose center is in the middle of the tray. The crucibles can be arranged in a single circle, two inner and outer circles, or multiple circles according to their size.

4. The device according to any one of claims 1 to 3, characterized in that: The multi-rod crucible is provided with an explosion-proof valve. When the pressure difference between the inside and outside of the crucible is less than a preset threshold, the crucible is kept relatively closed. When the pressure difference exceeds the preset threshold, the explosion-proof valve automatically opens to release the gas in the crucible.

5. The device according to claim 1, characterized in that The insulation structure includes upper and lower insulation layers and an insulation ring. The height and position of the upper and lower insulation layers are adjusted according to multi-rod crucibles of different specifications. The height of the insulation ring is adjusted according to crucibles of different sizes and specific crystal growth requirements.

6. The device according to claim 5, characterized in that The insulation structure comprises an insulation cover, an upper insulation barrel, an insulation ring, a lower insulation barrel, an insulation base and a support ring, wherein the insulation cover, the upper insulation barrel and the insulation ring together form an upper insulation layer, and the insulation ring, the lower insulation barrel and the insulation base together form a lower insulation layer; and / or, The thermal insulation structure is made of graphite material; and / or, The thickness of the thermal insulation structure is not less than 30 mm.

7. The device according to claim 1, characterized in that The vacuum furnace body system mainly consists of a double-layer furnace cover, an upper furnace cavity shell, a lower furnace cavity shell and a furnace bottom plate, and is provided with a cooling water channel inside; the vacuum furnace body system also includes a furnace shell lifting mechanism connected to the furnace cover and the upper furnace cavity shell, and a vacuum pipe connected to the furnace cavity; and / or, The vacuum furnace system provides and adjusts the required atmosphere environment through the atmosphere control system.

8. The device according to claim 1, characterized in that The upper heater and the lower heater are both graphite heaters, and the graphite heaters are connected to metal electrodes through graphite rods and are connected to external power supply lines to achieve heating and power control.

9. A method for crystal growth using the device according to any one of claims 1 to 8, characterized in that: The following steps are involved: According to the growth composition and final size requirements, multiple groups of raw materials, dopants and deoxidizers in predetermined proportions are mixed and loaded into a multi-rod crucible, and the crucible is placed on a tray; Adjust the layout of the dual-zone heater, assemble the insulation structure, close the vacuum chamber, start the vacuum acquisition system to pump the vacuum chamber to a preset vacuum degree and maintain it, or replenish the preset atmosphere to a preset pressure according to the crystal growth conditions; Start the heating program, raise the temperature of the upper heater and the lower heater to the preset dehydration and air temperature of 200-400℃ at the same time, and keep it for 1-5h to fully remove the moisture and air; then raise the temperature to 700-1000℃, the temperature at which the deoxidizer reacts with the oxygen-containing components in the raw material, and keep it for 1-10h; Continue to adjust the temperature of the upper heater to 50-200°C higher than the melting point of the crystal, and raise the temperature of the lower heater to 200-300°C lower than the melting point of the crystal, and keep it for a period of time to allow the raw materials to fully melt, and then start to grow downward at a preset speed; When it descends to a preset distance, it stops descending and starts a preset cooling program. When the temperature drops to room temperature, the vacuum acquisition system and the atmosphere control system are turned off, the furnace cavity is opened, and multiple ingots are taken out from multiple independent crucibles.

10. The method according to claim 9, characterized in that In the same growth furnace, different sizes of ingots can be obtained; and / or, In the same growth furnace, multiple non-doped and doped crystal rods with different components can be obtained, thereby realizing high-throughput screening of doping components and doping amounts.

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