Center heating fluoride multi-crucible descent method crystal growth thermal field and crystal growth method thereof

Abstract

The invention relates to a center heating fluoride multi-crucible descent method crystal growth thermal field which comprises a furnace body provided with a vacuum inner cavity, a side peripheral heating body and a center heating body which are independently controlled are arranged in the vacuum inner cavity, and the side peripheral heating body is cylindrical and covers the periphery of the center heating body. The central heating body is arranged at the central position of the side peripheral heating body and is also located at the central position of the vacuum inner cavity, at least one arc-shaped crucible is arranged between the side peripheral heating body and the central heating body in the peripheral direction of the side peripheral heating body, and the crucible can be an integral annular crucible and is provided with a plurality of growth notches; the crucible can also be an annular crucible formed by splicing a plurality of groups of independent arc-shaped crucibles and is used for preparing a plurality of groups of fluoride crystals, and a descending mechanism for driving the crucible to ascend and descend is arranged in the furnace body. The crucible is arranged in the space between the central heating body and the side heating body, and the inner side and the outer side of the crucible are heated by the central heater and the side heater respectively, so that the temperatures of the front, back, left and right sides of the crucible are uniform, and low-cost and large-batch preparation of fluoride crystals is realized.

Description

Technical Field

[0001] The present application relates to the technical field of fluoride crystal preparation, and in particular to a centrally heated fluoride multi-crucible descending method crystal growth thermal field and a crystal growth method thereof. Background Art

[0002] Fluoride crystals are a type of optical crystal material with excellent performance. For example, calcium fluoride, magnesium fluoride, lithium fluoride, barium fluoride, etc. have wide-band and high-transmittance optical properties from deep ultraviolet to mid- and far-infrared, and are widely used in ultraviolet lasers, semiconductor lithography, high-magnification microscopy, and other fields.

[0003] Traditional fluoride crystal preparation methods are mainly crucible descent method and Czochralski method. Among them, the crucible descent method has become the mainstream technology for the industrial preparation of fluoride crystals due to its advantages such as good crystal quality and high degree of equipment automation. In the traditional crucible descent method, a cylindrical heater surrounds the crucible. As the size of the fluoride crystal continues to increase, the size of the crucible continues to increase synchronously during the crucible descent method. The temperature gradient between the center and edge of the crucible is large, that is, the radial temperature gradient of the crystal growth thermal field is too large, resulting in instability of the solid-liquid interface during the crystal growth process, resulting in crystal cracking or poor crystal quality.

[0004] At present, there is also a porous crucible descent method for preparing fluorides. This method is to process the original large-diameter crucible into a porous crucible, and multiple crystals grow synchronously during the crystal growth process. The advantage of this method is that the aperture can be designed according to the external dimensions of the product, and small-diameter crystals can be prepared at a faster crystal growth rate. However, as the size of the crucible continues to increase, there will also be a large temperature difference between the crystal growth holes at the edge of the crucible and the crystal growth holes in the center of the crucible. Because the heater is generally set on the side of the crucible, the fluoride growth rates in the crystal growth holes at different positions of the crucible will be inconsistent, and the crystals produced in the same furnace will have poor consistency, affecting the yield.

[0005] Therefore, there is an urgent need in the art for a centrally heated multi-crucible descending crystal growth thermal field solution to make the crucible radial temperature uniform and improve the crystal growth quality. Summary of the invention

[0006] In order to make the temperature uniform on the front and back and left and right sides of the crucible, the distance from the center to the edge of the crystal in the crucible is effectively reduced to make the radial temperature uniform, so as to achieve low-cost, high-quality and large-scale production of fluoride crystals.

[0007] The present application provides a centrally heated fluoride multi-crucible descending method crystal growth thermal field and a crystal growth method thereof, which adopts the following technical solutions: In the first aspect, the present invention provides a centrally heated fluoride multi-crucible descent method crystal growth thermal field, comprising a furnace body, the furnace body is provided with a vacuum inner cavity, the vacuum inner cavity is provided with independently controlled lateral heating elements and a central heating element, the lateral heating elements are cylindrical, the lateral heating element cover is provided on the periphery of the central heating element, the central heating element is placed at the center of the lateral heating elements and at the center of the vacuum inner cavity, at least one arc-shaped crucible is provided between the lateral heating elements and the central heating element in the circumferential direction of the lateral heating elements, the crucible can be used for the preparation of multiple groups of fluoride crystals, and a descent mechanism for driving the crucible to rise and fall is provided in the furnace body.

[0008] Optionally, the crucible may be an integral annular crucible provided with a plurality of growth notches, or may be an annular crucible formed by assembling a plurality of independent arc-shaped crucibles.

[0009] Optionally, the central heating element is a cylindrical graphite heater, the central heating element is coaxially arranged with the lateral heating elements, and the diameter of the central heating element is in the range of 100 to 150 mm.

[0010] Optionally, an external heat-insulating layer is provided around the inner periphery of the furnace body, and the side heating elements and the central heating element are both arranged in the external heat-insulating layer.

[0011] Optionally, an annular platform support is provided in the furnace body and is driven to rise and fall by the descending mechanism, and the crucible is provided on the annular platform support.

[0012] Optionally, a carbon felt insulation layer is provided outside the side heating element and the central heating element.

[0013] In the second aspect, the present invention provides a method for growing and preparing fluoride crystals, which uses the above-mentioned centrally heated fluoride multi-crucible descent method crystal growth hot field for growth and preparation, including the following steps: installing and loading the hot field; evacuating the inner cavity of the furnace body and filling it with a protective atmosphere; stably heating the inner cavity of the furnace body to an appropriate temperature through lateral heating and a central heating element to chemically treat the raw materials; the crystal grows as the crucible descends under a stable gas pressure; and the crucible is cooled and annealed.

[0014] Optionally, when the raw materials are subjected to chemical treatment, the heating rates of the side heating elements and the central heating element are controlled within the range of 100-150°C / h until the temperature in the crucible reaches 1480°C and the temperature is kept constant for two hours to ensure that all the raw materials in the crucible are melted.

[0015] Optionally, when the crystal grows as the crucible descends, the pressure in the crucible is controlled at 5×10 -3 Below Pa.

[0016] Optionally, when the crystal grows as the crucible descends, the crucible descent rate is controlled at 0.1-0.5 mm / h, the heating power of the side heating elements and the central heating element remains unchanged during the descent, and the total descent stroke of the crucible is 2 / 3 of the crucible height until the crystal growth ends.

[0017] In summary, the present application includes at least one of the following beneficial technical effects: The centrally heated fluoride multi-crucible descending method crystal growth thermal field of the present invention has the central heating element and the side peripheral heating element acting on the front and back of the crucible, and the two groups of heaters can be independently controlled and can be regulated by the heating power to achieve uniform temperature in the front and back and on the left and right sides of the crucible. The annular crucible design can effectively reduce the distance from the center to the edge of the crystal in the crucible, making the radial temperature uniform. It is especially suitable for the synchronous growth of multiple crystals of small and medium diameters of 4-6 inches, and can maintain a relatively high growth rate and effectively increase the feed amount under multiple crucibles. It is an effective solution for achieving low-cost and large-scale preparation of fluoride crystals. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the structure of a thermal field of a centrally heated fluoride multi-crucible descent method crystal growth method provided in this embodiment.

[0019] Figure numerals: 1, furnace body; 11, vacuum inner cavity; 2, lateral heating element; 3, central heating element; 4, crucible; 41, growth notch; 5, annular platform bracket; 6, descending mechanism; 7, external insulation layer. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the embodiment of the present application clearer, the technical scheme of the embodiment of the present application will be clearly and completely described in conjunction with the drawings of the embodiment of the present application. Obviously, the described embodiment is a part of the embodiment of the present application, not all of the embodiments. Based on the described embodiment of the present application, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of this application.

[0021] Unless otherwise defined, the technical terms or scientific terms used herein shall have the common meanings understood by persons with ordinary skills in the field to which this application belongs. The words "one" or "an" and the like used in the patent application specification and claims of this application do not indicate a quantity limitation, but indicate the existence of at least one.

[0022] The following is combined with Figure 1 This application is described in further detail.

[0023] The embodiment of the present application discloses a centrally heated fluoride multi-crucible 4-descent method crystal growth thermal field.

[0024] Reference Figure 1 A centrally heated fluoride multi-crucible 4 descending method crystal growth thermal field comprises a furnace body 1, a suction port is integrally formed on the furnace body 1 and connected to an external vacuum pumping device to form a vacuum cavity 11 in the furnace body 1, and independently controlled side peripheral heating elements 2 and central heating elements 3 are installed in the vacuum cavity 11, and the side peripheral heating elements 2 and the central heating elements 3 are both graphite heaters, the side peripheral heating elements 2 are cylindrical, and the side peripheral heating elements 2 are covered on the periphery of the central heating element 3, and the central heating element 3 is placed at the center of the side peripheral heating elements 2 and is located in the vacuum cavity At the center position 11, at least one arc-shaped crucible 4 is installed between the side heating element 2 and the central heating element 3 in the circumferential direction of the side heating element 2. The crucible 4 can be used for the preparation of multiple groups of fluoride crystals. The inner and outer sides of the crucible 4 are heated by the central heating element 3 and the side heating element respectively. At the same time, the heating power of the side heating element 2 and the central heating element 3 can be independently controlled to achieve uniform temperature of the front and back and left and right sides of the crucible 4. A descending mechanism 6 for driving the crucible 4 to rise and fall is installed in the furnace body 1, thereby realizing the descending method crystal growth operation of fluoride.

[0025] The crucible 4 can be an integral annular crucible 4 with a plurality of growth slots 41, or can be an annular crucible 4 composed of a plurality of independent arc-shaped crucibles 4, so as to ensure the mass production of fluoride crystals while ensuring the consistency of the growth quality of each crystal as much as possible.

[0026] The central heating element 3 can be a graphite heater of any shape. In the present embodiment, the central heating element 3 is preferably a cylindrical graphite heater. The central heating element 3 is coaxially arranged with the lateral heating element 2. The diameter of the central heating element 3 is in the range of 100 to 150 mm, which further ensures the consistency of the heating temperature of the inner wall side of each crucible 4 within the circumference of the central heating element 3.

[0027] Reference Figure 1 An annular platform bracket 5 is installed in the furnace body 1 and driven to rise and fall by a descending mechanism 6. The crucible 4 is installed and placed on the annular platform bracket 5. The descending mechanism 6 can be a cylinder driving mechanism, or a descending mechanism 6 driven by a screw or a slider, as long as it can achieve stable lifting of the annular platform bracket 5. This is the prior art and will not be described in detail.

[0028] Reference Figure 1 An external insulation layer 7 is installed around the furnace body 1, the side heating elements 2 and the central heating element 3 are installed in the external insulation layer 7, the lifting and telescopic part of the descending mechanism 6 passes through the external insulation layer 7, and the side heating elements 2 and the central heating element 3 are bonded and fixed with a carbon felt insulation layer to minimize the heat loss in the furnace body 1 during the crystal growth process, thereby ensuring the growth efficiency of the fluoride crystal.

[0029] The multi-crucible 4-vacuum descending furnace device for growing fluoride crystals of this embodiment is used to prepare the growth of crystals in the following manner: Step S1: Thermal field installation and loading.

[0030] Specifically, the fluoride raw material is placed in the crucible 4, and the thermal field components are installed one by one according to the thermal field structure.

[0031] Step S2, evacuating and filling with protective atmosphere.

[0032] Start the vacuum pump and evacuate the inner cavity of the furnace body 1 through the suction port until the pressure in the furnace body 1 drops to 5×10 -3 Pa or less, and the vacuum inner cavity 11 of the furnace body 1 is filled with a protective atmosphere to ensure the stability of crystal growth.

[0033] Step S3, heating the material.

[0034] Specifically, start the power supply, start the central heating element 3 and the side heating element for heating respectively, heat until the temperature of the temperature measuring point at the bottom of the crucible 4 rises to 1480°C, keep the temperature constant for 2 hours to ensure that all the raw materials in the crucible 4 are melted; adjust the temperature inside and outside the crucible 4 by adjusting the two sets of internal and external heaters to make the temperature inside and outside the crucible 4 consistent.

[0035] Step S4, crystal growth.

[0036] After the raw materials are melted and the gas pressure in the furnace is stable, the crucible 4 is controlled to descend by the descending mechanism 6 to start crystal growth. The descending rate of the crucible 4 is controlled at 0.1-0.5 mm / h. At this time, the heating power is maintained unchanged. The total descending stroke of the crucible 4 is 2 / 3 of the height of the crucible 4 until the crystal growth is completed.

[0037] Step S5, cooling and annealing.

[0038] After the crystal growth is completed, the crucible 4 is stopped from descending, and the crucible 4 is cooled to room temperature.

[0039] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A centrally heated fluoride multi-crucible descending crystal growth thermal field, comprising a furnace body, characterized in that: The furnace body is provided with a vacuum inner cavity, in which independently controlled lateral heating elements and central heating elements are provided, the lateral heating elements are cylindrical, the lateral heating element cover is provided on the periphery of the central heating element, the central heating element is placed at the center of the lateral heating elements and at the center of the vacuum inner cavity, at least one arc-shaped crucible is provided between the lateral heating elements and the central heating element in the circumferential direction of the lateral heating elements, the crucible can be used for the preparation of multiple groups of fluoride crystals, and a descending mechanism for driving the crucible to rise and fall is provided in the furnace body.

2. The centrally heated fluoride multi-crucible descending crystal growth thermal field according to claim 1, characterized in that: The crucible may be an integral annular crucible provided with a plurality of growth notches, or may be an annular crucible formed by assembling a plurality of independent arc-shaped crucibles.

3. The centrally heated fluoride multi-crucible descending crystal growth thermal field according to claim 1, characterized in that: The central heating element is a cylindrical graphite heater, which is coaxially arranged with the lateral heating elements, and the diameter of the central heating element is in the range of 100-150 mm.

4. The centrally heated fluoride multi-crucible descending crystal growth thermal field according to claim 1, characterized in that: An external heat-insulating layer is arranged around the furnace body, and the side heating elements and the central heating element are both arranged in the external heat-insulating layer.

5. The centrally heated fluoride multi-crucible descending crystal growth thermal field according to claim 1, characterized in that: An annular platform support is arranged in the furnace body and driven to rise and fall by the descending mechanism, and the crucible is arranged on the annular platform support.

6. The multi-crucible vacuum descending furnace device for growing fluoride crystals according to claim 1, characterized in that: The side heating elements and the central heating element are both provided with carbon felt insulation layers.

7. A method for growing and preparing fluoride crystals, characterized in that: The method of using the centrally heated fluoride multi-crucible descending crystal growth thermal field as described in any one of claims 1 to 6 for growth preparation comprises the following steps: Thermal field installation and charging; The inner cavity of the furnace is evacuated and filled with protective atmosphere; The inner cavity of the furnace body is stably heated to an appropriate temperature through the side heating elements and the central heating element to process the raw materials; The crystal grows as the crucible descends under a stable gas pressure; The crucible is subjected to temperature reduction annealing.

8. A fluoride crystal growth preparation method according to claim 7, characterized in that: When the raw materials are processed, the heating rates of the side heating elements and the central heating element are controlled within the range of 100-150°C / h until the temperature in the crucible reaches 1480°C and the temperature is kept constant for two hours to ensure that all the raw materials in the crucible are melted.

9. A fluoride crystal growth preparation method according to claim 7, characterized in that: As the crystal grows as the crucible descends, the pressure in the crucible is controlled at 5×10 -3 Below Pa.

10. A fluoride crystal growth preparation method according to claim 7, characterized in that: When the crystal grows with the crucible, the crucible descent rate is controlled at 0.1-0.5 mm / h. During the descent, the heating power of the side heating element and the central heating element remains unchanged. The total descent stroke of the crucible is 2 / 3 of the crucible height until the crystal growth ends.

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