An adaptive annealing crucible for large-size fluoride crystals

Abstract

An adaptive annealing crucible for large-size fluoride crystals includes: a crucible base having an inner ring located radially inward, an outer ring located radially outward, and a lower adaptive layer connecting the inner and outer rings; a crucible lid having an inner ring located radially inward, an outer ring located radially outward, and an upper adaptive layer connecting the inner and outer rings; an inner crucible cylinder composed of multiple segmented structures, movably and vertically disposed between the inner ring of the base and the inner ring of the lid; and the inner cylinder being capable of radial expansion and contraction; and a guiding structure for defining the direction of expansion and contraction of the inner cylinder. This invention solves the problem that crystals cannot freely expand and contract during annealing, resulting in the inability to release stress within the crystal.

Description

Technical Field

[0001] This invention belongs to the field of annealing technology for large-size fluoride crystals, specifically relating to an adaptive annealing crucible for large-size fluoride crystals. Background Technology

[0002] Fluoride crystals (calcium fluoride, barium fluoride, magnesium fluoride, etc.) are important optical materials with many advantages, including high ultraviolet transmittance (≥99.8%@193nm), wide transmission range (130nm~12μm), constant average and local refractive indices, high laser damage threshold, strong resistance to chemical corrosion, and ease of mass production. They are very suitable as optical window materials in the vacuum ultraviolet to infrared band and are also irreplaceable apochromatic lens materials. They are widely used in ultraviolet lithography, astronomical observation, aerial surveying, optical windows, reconnaissance, airborne optoelectronic radar, laser windows, and high-resolution optical instruments.

[0003] Currently, the mainstream method for growing large-size fluoride crystals is the crucible lowering method. This method uses a fully or semi-enclosed crucible, and the temperature is gradually reduced as the crucible is slowly lowered to achieve crystal growth. However, the unavoidable mechanical vibrations in this method cause temperature fluctuations at the solid-liquid interface and a large radial temperature gradient during crystal growth, which in turn leads to stress within the crystal.

[0004] To reduce internal stress in the crystal, annealing is typically performed in an annealing furnace after growth to further reduce crystal stress. Current annealing methods for fluoride crystals generally involve placing the ingot or a roughly machined sample of a certain size and shape directly into a crucible. A small number of large crystals are annealed using crushed crystal material as filler. However, the crucibles in existing technologies have simple structures and fixed sizes, making it inconvenient to place and remove crystals. Furthermore, the sidewalls of the annealing crucible are in direct contact with the crystal, or both are in contact with the crushed crystal material, without any buffer gap for expansion and contraction. During annealing, the crystal cannot freely expand or contract, preventing the release of internal stress and generating new stress. The presence of these stresses makes fluoride crystals prone to cracking during processing. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide an adaptive annealing crucible for large-size fluoride crystals. The adaptive annealing crucible of the present invention can provide a buffer gap for the expansion and contraction of the crystal during the crystal annealing process, effectively solving the problem that the crystal cannot expand and contract freely during the annealing process in the prior art, thus preventing the stress inside the crystal from being released.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] An adaptive annealing crucible for large-size fluoride crystals, comprising:

[0008] A crucible base plate having an inner ring located radially inward, an outer ring located radially outward, and a lower adaptive layer connecting the inner ring and the outer ring.

[0009] A crucible lid having an inner ring located radially inward, an outer ring located radially outward, and an upper adaptive layer connecting the inner ring and the outer ring;

[0010] The crucible inner cylinder is composed of multiple segmented structures joined together and is movably and vertically disposed between the inner ring of the base plate and the inner ring of the cover; and the crucible inner cylinder can expand and contract radially; and

[0011] A guiding structure is provided to define the direction of expansion and contraction of the inner cylinder of the crucible.

[0012] In one embodiment of the present invention, the inner cylinder of the crucible is preferably composed of 3 to 6 segmented structures spliced ​​together.

[0013] In one embodiment of the present invention, each of the segmented structures includes: a main body portion, an outer connecting portion located at one end of the main body portion, and an inner connecting portion located at the other end of the main body portion. The outer connecting portions and inner connecting portions of two adjacent segmented structures overlap and are connected. When the inner cylinder of the crucible expands or contracts, the plurality of segmented structures move radially within the lower adaptive layer and the upper adaptive layer, while the outer connecting portions and inner connecting portions slide relative to each other circumferentially. The outer connecting portions and inner connecting portions of two adjacent segmented structures are configured such that, when the inner cylinder of the crucible expands, the outer connecting portions and inner connecting portions are always in a connected state.

[0014] In one embodiment of the present invention, the inner ring of the chassis is higher than the lower adaptive layer, and the bottom of the inner cylinder of the crucible is fitted around the outer periphery of the inner ring of the chassis.

[0015] In one embodiment of the present invention, the inner ring of the lid is higher than the upper adaptive layer, and the top of the inner cylinder of the crucible is fitted around the outer periphery of the inner ring of the lid.

[0016] In one embodiment of the present invention, the guiding structure is a guide shaft, which has a fixing part and a guiding part. The fixing parts of multiple guide shafts are respectively fixedly connected to the upper and lower parts of the segmented structure along the axial direction of the inner cylinder of the crucible. The guiding parts of the multiple guide shafts are slidably connected to the outer ring of the cover and the outer ring of the base. The outer ring of the base and the outer ring of the cover are respectively provided with multiple guide holes, and the guiding parts of the multiple guide shafts are slidably inserted into the multiple guide holes. When the inner cylinder of the crucible expands or contracts, the multiple guide shafts slide within the guide holes, and the segmented structure moves within the lower adaptive layer and the upper adaptive layer along the sliding direction of the guide shafts.

[0017] In one embodiment of the present invention, each of the main body portions of the segmented structure has connecting holes at both ends, and the fixing portion of the guide shaft is connected to the connecting holes.

[0018] In one embodiment of the present invention, the connecting hole is a threaded hole, the fixing part is a screw, and the screw is threadedly connected to the threaded hole.

[0019] In one embodiment of the present invention, the guiding structure is a guide slider, and a plurality of guide sliders are respectively disposed at the top and bottom ends of the segmented structure along the axial direction of the inner cylinder of the crucible. The lower adaptive layer is provided with a lower guide groove that cooperates with the guide slider at the bottom end of the segmented structure, and the upper adaptive layer is provided with an upper guide groove that cooperates with the guide slider at the top end of the segmented structure. When the inner cylinder of the crucible expands or contracts, the plurality of guide sliders slide in the lower guide groove and the upper guide groove respectively, driving the plurality of segmented structures to move along the lower guide groove and the upper guide groove in the lower adaptive layer and the upper adaptive layer.

[0020] In one embodiment of the present invention, elastic materials for controlling the stable expansion and contraction of the inner cylinder of the crucible are added to the upper adaptive layer and the lower adaptive layer.

[0021] In one embodiment of the present invention, the elastic material is graphite felt or a spring.

[0022] In one embodiment of the present invention, the crucible lid is further provided with vent holes for discharging air and impurities from the adaptive annealing crucible. The diameter of the vent holes is preferably 1 mm to 3 mm.

[0023] In one embodiment of the present invention, the large-sized fluoride crystal is a calcium fluoride crystal.

[0024] As one embodiment of the present invention, based on the thermal expansion coefficient of calcium fluoride crystals and their conventional annealing temperatures, the adaptive annealing crucible of the present invention with the following specifications and dimensions is preferably used for annealing calcium fluoride crystals with a diameter of 200 mm to 500 mm.

[0025] The inner diameter of the crucible inner cylinder is preferably 220mm to 520mm, and the outer diameter is preferably 240mm to 580mm. At this time, the inner cylinder wall thickness (the thickness of the main body of the segmented structure) is 10mm to 30mm.

[0026] The diameters of the inner ring of the base and the inner ring of the lid are preferably the same as the inner diameter of the crucible inner cylinder, i.e., 220mm to 520mm. The inner diameters of the outer rings of the base and the lid are preferably 260mm to 640mm, and the outer diameters are preferably 280mm to 700mm. In this case, the thickness of the outer rings of the base and the lid (i.e., the wall thickness of the crucible base and the crucible lid) is 10mm to 30mm.

[0027] The widths (i.e., the ring width of the annular gap) of the lower adaptive layer and the upper adaptive layer are 20 mm to 60 mm. Considering that the inner cylinder of the crucible can be nested within the inner ring of the base and the inner ring of the cover, and that the calcium fluoride crystal will expand slightly in the axial direction, the inner ring of the base is preferably 2 mm to 5 mm higher than the lower adaptive layer, and the inner ring of the cover is preferably 2 mm to 5 mm higher than the upper adaptive layer.

[0028] Considering the issue of uniform heating of the crucible base and the crucible lid, the bottom thickness of the crucible base and the crucible lid is preferably the same as the wall thickness of the crucible base and the crucible lid, i.e., 10mm to 30mm.

[0029] The connecting hole is preferably located 20 mm from the top and bottom of each segment structure 110. The diameter of the connecting hole 120 and the diameter of the guide shaft are preferably 5 mm to 10 mm; the diameter of the guide hole is preferably 6 mm to 11 mm.

[0030] It is important to understand that the aforementioned adaptive annealing crucibles with specific dimensions are not only applicable to calcium fluoride crystals of a fixed size, but also to the annealing of crystals smaller than that fixed size. For example, an annealing crucible with an inner diameter of 220 mm is not only applicable to calcium fluoride crystals with a diameter of 200 mm, but is also suitable for the annealing of calcium fluoride crystals smaller than 200 mm.

[0031] Compared with the prior art, the present invention has the following beneficial technical effects:

[0032] 1. The inner cylinder of the crucible is composed of multiple segmented structures, which makes assembly and disassembly more convenient than traditional one-piece crucibles;

[0033] 2. By moving the segmented structure of the inner cylinder of the crucible to change the diameter of the crucible, the diameter of the crucible opening can be increased, which facilitates the placement and removal of crystals.

[0034] 3. The upper and lower adaptive layers between the inner cylinder of the crucible and the crucible lid and the crucible base can provide a buffer gap for the expansion and contraction of the crystal;

[0035] 4. An adaptive annealing crucible of appropriate size can be selected based on the size, coefficient of thermal expansion and annealing temperature of large-size fluoride crystals;

[0036] 5. By adding elastic material to the adaptive layer, the problem of insufficient stress release caused by crystal extrusion during annealing is effectively solved;

[0037] 6. By using a guiding structure to limit the expansion direction of the inner cylinder of the crucible, the expansion and contraction of the crystal proceeds along the direction defined by the guiding structure, which can effectively prevent the crystal from shifting during subsequent operations. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of the structure of a large-size fluoride crystal adaptive annealing crucible according to a specific embodiment of the present invention;

[0040] Figure 2 This is a schematic diagram of the inner cylinder of a large-size fluoride crystal adaptive annealing crucible according to a specific embodiment of the present invention;

[0041] Figure 3 This is a schematic diagram of the segmented structure of the inner cylinder of a large-size fluoride crystal adaptive annealing crucible according to a specific embodiment of the present invention.

[0042] Figure 4 This is a schematic diagram of the guide component of a large-size fluoride crystal adaptive annealing crucible according to a specific embodiment of the present invention;

[0043] Figure 5 This is a schematic diagram of the crucible base of a large-size fluoride crystal adaptive annealing crucible according to a specific embodiment of the present invention;

[0044] Figure 6 This is a schematic diagram of the crucible lid of a large-size fluoride crystal adaptive annealing crucible according to a specific embodiment of the present invention;

[0045] Figure 7 This is a cross-sectional view of a large-size fluoride crystal adaptive annealing crucible according to a specific embodiment of the present invention;

[0046] Figure 8 The stress birefringence values ​​of a large-sized calcium fluoride crystal after annealing using an annealing crucible according to a specific embodiment of the present invention are shown.

[0047] Figure 9 The stress birefringence values ​​after annealing large-sized calcium fluoride crystals using a conventional crucible are shown.

[0048] Explanation of reference numerals in the attached figures:

[0049] 100: Inner cylinder of crucible; 110: Split structure; 111: Main body; 112: Inner connecting part; 113: Outer connecting part; 120: Connecting hole;

[0050] 200: Guide structure, 210: Fixing part, 220: Guide part;

[0051] 300: Crucible lid, 320: Inner ring of lid, 330: Upper adaptive layer, 340: Outer ring of lid, 350: Vent hole;

[0052] 400: Crucible base plate; 420: Inner ring of the base plate; 430: Lower adaptive layer; 440: Outer ring of the base plate.

[0053] 310, 410: Guide holes. Detailed Implementation

[0054] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Furthermore, it should be understood that the specific embodiments described herein are only for illustration and explanation of the present invention and are not intended to limit the present invention. In the present invention, unless otherwise stated, directional terms such as "up," "down," "left," "right," "front," and "back" generally refer to up, down, left, and right in the actual use or working state of the device, specifically the drawing directions in the accompanying drawings.

[0055] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of embodiments of the present invention. Furthermore, the descriptions of each embodiment in the following embodiments have their own emphasis; for parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0056] like Figures 1 to 3 and Figure 7As shown, the present invention provides an adaptive annealing crucible for large-size fluoride crystals. The annealing crucible includes: an inner crucible cylinder 100, a crucible base 400, and a crucible lid 300. The inner crucible cylinder 100 is perpendicularly disposed between the crucible base 400 and the crucible lid 300 along the axial direction of the annealing crucible, and the inner crucible cylinder 100 can expand and contract within the crucible base 400 and the crucible lid 300 along the radial direction of the annealing crucible.

[0057] In one embodiment of the present invention, the crucible inner cylinder 100 can be an annular inner cylinder assembled from multiple arc-shaped segmented structures 110. Each segmented structure 110 has a main body 111 and inner connecting portions 112 and outer connecting portions 113 located at both ends of the main body 111. The outer connecting portions 113 of two adjacent segmented structures 110 overlap and are connected to the inner connecting portions 112. More preferably, the outer connecting portions 113 and inner connecting portions 112 of two adjacent segmented structures 110 are configured to always be in an overlapping connection state when the crucible inner cylinder expands or contracts. According to the structure of the present invention, it can be ensured that the material inside the crucible inner cylinder 100 does not leak out.

[0058] like Figure 1 , Figure 5 , Figure 6 and Figure 7 As shown, preferably, the crucible base 400 includes: an inner ring 420 located radially inward of the crucible base 400, an outer ring 440 located radially outward of the crucible base 400, and a lower adaptive layer 430 (i.e., an annular gap between the inner ring 420 and the outer ring 440) located between the inner ring 420 and the outer ring 440 and connecting the inner ring 420 and the outer ring 440. One embodiment, as... Figure 5 and Figure 7 As shown, the inner ring 420 of the base is specifically a frustum that protrudes slightly from the bottom of the crucible base 400 along the axial direction of the annealing crucible and toward the crucible cover 300. The inner ring 420 of the base is higher than the lower adaptive layer 430, and the outer ring 440 of the base is higher than the inner ring 420 of the base. The outer ring 440 of the base is specifically the outer wall of the crucible base 400.

[0059] Preferably, the crucible lid 300 includes an inner lid ring 320 located radially inner to the crucible base 400, an outer lid ring 340 located radially outer to the crucible base 400, and an upper adaptive layer 330 (i.e., an annular gap between the inner lid ring 320 and the outer lid ring 340) connecting the inner lid ring 320 and the outer lid ring 340 and located between the inner lid ring 320 and the outer lid ring 340. In one embodiment, as... Figure 6 and Figure 7As shown, the inner ring 320 of the lid is specifically a frustum that protrudes slightly from the top of the lid 300 along the axial direction of the annealing crucible and toward the crucible base plate 400. The inner ring 320 is higher than the upper adaptive layer 330, and the outer ring 340 is higher than the inner ring 320. The outer ring 340 is specifically the outer wall of the crucible lid 300.

[0060] Preferably, the inner cylinder 100 of the crucible is disposed between the inner ring 420 of the base and the inner ring 320 of the lid. Specifically, the top of the inner cylinder 100 is fitted around the outer periphery of the inner ring 320 of the lid, and the bottom of the inner cylinder 100 is fitted around the outer periphery of the inner ring 420 of the base. During the annealing process of the large-sized fluoride crystal, the segmented structure 110 of the inner cylinder 100 can move within the lower adaptive layer 430 and the upper adaptive layer 330 along the radial direction of the annealing crucible. At the same time, the outer connecting part 113 and the inner connecting part 112 slide relative to each other along the circumferential direction of the inner cylinder 100, thereby realizing the expansion and contraction of the inner cylinder 100.

[0061] As one embodiment of the present invention, such as Figure 1 , Figure 2 , Figure 4 and Figure 7 As shown, the annealing crucible also includes a guide structure 200 capable of limiting the radial expansion and contraction of the inner crucible cylinder 100. Preferably, in some embodiments, the guide structure 200 may be a structure disposed between the inner crucible cylinder 100 and the crucible base 400 and between the inner crucible cylinder 100 and the crucible cover 300, which allows the inner crucible cylinder 100 to expand and contract radially.

[0062] In another implementation, such as Figure 2 , Figures 4 to 7 As shown, the guide structure 200 is a columnar guide shaft with a fixing part 210 and a guide part 220. Preferably, the main body 111 of the segmented structure 110 is provided with a connecting hole 120 fixedly connected to the fixing part 210, and the outer ring 340 of the cover and the outer ring 440 of the base are provided with guide holes 310 and 410, respectively. The guide part 220 of the guide structure 200 is slidably inserted into the guide holes 310 and 410. More preferably, the fixing part 210 is threadedly connected to the connecting hole 120. When the inner cylinder 100 of the crucible expands or contracts, the guide part 220 slides in the guide holes 310 and 410, thereby restricting the movement of the segmented structure 110 in the lower adaptive layer 430 and the upper adaptive layer 330 along the sliding direction of the guide structure, so as to restrict the expansion and contraction direction of the inner cylinder 100 of the crucible.

[0063] In other embodiments, the guide structure 200 may also include guide sliders (not shown) respectively disposed at the top and bottom ends of the main body 111 of the segmented structure 110 along the axial direction of the inner cylinder 100; a lower guide groove (not shown) cooperating with the guide slider at the bottom end of the main body 111 and extending within the lower adaptive layer 430 along the radial direction of the annealing crucible; and an upper guide groove (not shown) cooperating with the guide slider at the top end of the main body 111 and extending within the upper adaptive layer 330 along the radial direction of the annealing crucible. When the inner cylinder 100 of the crucible expands or contracts, the plurality of guide sliders slide within the lower guide groove and the upper guide groove respectively, thereby restricting the movement of the plurality of segmented structures 110 within the lower adaptive layer 430 and the upper adaptive layer 330 along the directions specified by the lower guide groove and the upper guide groove, so as to restrict the expansion and contraction direction of the inner cylinder 100 of the crucible.

[0064] Example 1

[0065] Figures 1 to 3 and Figure 7 As shown, Embodiment 1 of the present invention provides an adaptive annealing crucible for large-size fluoride crystals. This adaptive annealing crucible is preferably used for annealing calcium fluoride crystals with a diameter of φ200mm × 55mm. The annealing crucible includes: an inner crucible cylinder 100, a crucible base 400, a crucible lid 300, and a guide structure 200. The inner crucible cylinder 100 is perpendicularly disposed between the crucible base 400 and the crucible lid 300 along the axial direction of the annealing crucible. The guide structure 200 consists of multiple guide shafts connecting the inner crucible cylinder 100 and the crucible base 400, and the inner crucible cylinder 100 and the crucible lid 300 along the radial direction of the annealing crucible. The inner crucible cylinder 100 is used to place the calcium fluoride crystal, and a gap exists between the calcium fluoride crystal and the inner wall of the inner crucible cylinder 100 for adding padding material to remove impurities.

[0066] Preferably, the crucible inner cylinder 100 is an annular inner cylinder assembled from three segmented structures 110. Each segmented structure 110 has a main body 111 and inner connecting portions 112 and outer connecting portions 113 located at both ends of the main body 111. The outer connecting portions 113 of two adjacent segmented structures 110 overlap and are connected to the inner connecting portions 112. More preferably, the outer connecting portions 113 and inner connecting portions 112 of two adjacent segmented structures 110 are configured to always be in an overlapping connection state when the crucible inner cylinder expands or contracts, so as to ensure that the material inside the crucible inner cylinder 100 does not leak out.

[0067] like Figure 1 , Figures 5 to 7As shown, the crucible base 400 includes: an inner ring 420 located radially inward, an outer ring 440 located radially outward, and a lower adaptive layer 430 (i.e., an annular gap between the inner ring 420 and the outer ring 440) located between the inner ring 420 and the outer ring 440 and connecting them. Specifically, the inner ring 420 is a frustum protruding from the bottom of the crucible base 400 along the axial direction of the annealing crucible and toward the crucible cover 300. The inner ring 420 is higher than the lower adaptive layer 430, and the outer ring 440 is higher than the inner ring 420. The outer ring 440 is specifically the outer perimeter wall of the crucible base 400.

[0068] The crucible lid 300 includes: an inner ring 320 located radially inward, an outer ring 340 located radially outward, and an upper adaptive layer 330 (i.e., an annular gap between the inner ring 320 and the outer ring 340) located between the inner ring 320 and the outer ring 340 and connecting the inner ring 420 and the outer ring 440 of the base plate. Specifically, the inner ring 320 is a frustum protruding from the top of the crucible lid 300 along the axial direction of the annealing crucible and toward the crucible base plate 400. The inner ring 320 is higher than the upper adaptive layer 330, and the outer ring 340 is higher than the inner ring 320. Specifically, the outer ring 340 is the outer wall of the crucible lid 300. The crucible inner cylinder 100 is disposed between the inner ring 420 of the base plate and the inner ring 320 of the lid.

[0069] Specifically, the top of the inner cylinder 100 is fitted around the outer periphery of the inner ring 320 of the lid, and the bottom of the inner cylinder 100 is fitted around the outer periphery of the inner ring 420 of the base. During the annealing process of the large-sized fluoride crystal, the segmented structure 110 of the inner cylinder 100 can move within the lower adaptive layer 430 and the upper adaptive layer 330 along the radial direction of the annealing crucible, while the outer connecting part 113 and the inner connecting part 112 slide relative to each other along the circumferential direction of the inner cylinder 100, thereby realizing the expansion and contraction of the inner cylinder 100.

[0070] Furthermore, based on the thermal expansion coefficient of calcium fluoride crystals and their conventional annealing temperature, the radial expansion dimension of a calcium fluoride crystal with a diameter of φ200mm×55mm during the annealing process is approximately 5mm. Considering that the calcium fluoride crystal needs to be wrapped with padding material within the inner cylinder 100 of the crucible during annealing, the dimensions of the adaptive annealing crucible in this embodiment are preferably as follows: the inner diameter of the inner cylinder 100 is preferably 220 mm, and the outer diameter is preferably 240 mm. In this case, the inner cylinder wall thickness (the thickness of the main body of the segmented structure 110) is 10mm; the length of the inner connecting portion 112 and the outer connecting portion 113 of the segmented structure 110 is preferably 10mm, and the thickness is preferably 5mm. Of course, the present invention is not limited to this; other sizes of the inner cylinder 100 can be selected according to the size of the calcium fluoride crystal, as long as it ensures that the calcium fluoride crystal can expand and contract normally within the adaptive annealing crucible of the present invention. The inner connecting part 112 and the outer connecting part 113 of the segmented structure 110 can also be set to other different sizes, as long as it can be ensured that the inner connecting part 112 and the outer connecting part 113 are always in an overlapping connection state during the expansion process of the inner cylinder 100 of the crucible. The present invention is not limited thereto.

[0071] Furthermore, the diameters of the inner ring 420 of the base and the inner ring 320 of the lid are preferably the same as the inner diameter of the inner cylinder 100 of the crucible, i.e., 220 mm, so that the inner cylinder 100 of the crucible is nested between the inner ring 420 of the base and the inner ring 320 of the lid in a form that is close to the inner ring 420 of the base and the inner ring 320 of the lid; the inner diameters of the outer ring 440 of the base and the outer ring 340 of the lid are preferably 260 mm and the outer diameters are preferably 280 mm; at this time, the width of the lower adaptive layer 430 and the upper adaptive layer 330 (i.e., the ring width of the annular gap) is 20 mm; at the same time, considering that the inner cylinder 100 of the crucible can be nested in the inner ring 420 of the base and the inner ring 320 of the lid and that the axial direction of the calcium fluoride crystal will also expand slightly, the inner ring of the base is preferably 2 mm higher than the lower adaptive layer, and the inner ring of the lid is preferably 2 mm higher than the upper adaptive layer.

[0072] like Figures 1 to 7 As shown, in this embodiment, the guide structure 200 consists of multiple guide shafts, each having a fixing part 210 and a guiding part 220. The upper and lower parts of the main body 111 of the segmented structure 110 are respectively provided with connecting holes 120 for fixing and connecting the guide structure 200. The fixing part 210 is threadedly connected to the connecting hole 120. The outer ring 340 of the cover and the outer ring 440 of the base are provided with guide holes 310 and 410. The guiding part 220 of the guide structure 200 is slidably inserted into the guide holes 310 and 410. When the inner cylinder 100 of the crucible expands or contracts, the guiding part 220 slides within the guide holes 310 and 410, thereby restricting the movement of the segmented structure 110 within the lower adaptive layer 430 and the upper adaptive layer 330 along the sliding direction of the guide structure.

[0073] The connecting hole 120 is preferably located 20 mm from the top and bottom of each segment structure 110. The diameter of the connecting hole 120 and the diameter of the guide shaft are preferably Φ5 mm; the diameter of the guide hole is preferably Φ6 mm.

[0074] Preferably, the upper adaptive layer 330 and the lower adaptive layer 430 contain an elastic material for controlling the stable expansion and contraction of the crucible inner cylinder 100, wherein the elastic material is preferably graphite felt or a spring.

[0075] Furthermore, such as Figure 6 and Figure 7 As shown, the crucible lid 300 is provided with a vent hole 350 for venting air and impurities from the inner cylinder of the crucible. The preferred diameter of the vent hole 350 is Φ1mm.

[0076] Example 2

[0077] The difference between this embodiment and embodiment one lies in the specific structure of the guide structure. Specifically, in this embodiment, the guide structure 200 consists of multiple guide sliders (not shown), which are respectively disposed at the top and bottom of the segmented structure 110 along the axial direction of the inner cylinder 100 of the crucible. The lower adaptive layer 430 is provided with a lower guide groove (not shown) that cooperates with the guide slider at the bottom of the segmented structure 110 and extends along the radial direction of the annealing crucible. The upper adaptive layer 330 is provided with an upper guide groove (not shown) that cooperates with the guide slider at the top of the segmented structure 110 and extends along the radial direction of the annealing crucible. When the inner cylinder 100 of the crucible expands or contracts, the multiple guide sliders slide in the lower guide groove and the upper guide groove respectively, thereby restricting the movement of the multiple segmented structures 110 in the lower adaptive layer 430 and the upper adaptive layer 330 along the directions specified by the lower guide groove and the upper guide groove.

[0078] The dimensions of each structure of the adaptive annealing crucible in the above embodiments are merely a preferred embodiment of the present invention and should be considered as exemplary rather than limiting. As long as sufficient expansion and contraction gaps can be provided for the crystal, different sizes of annealing crucibles can be selected according to the crystal to be annealed, and the effects of the present invention can be achieved.

[0079] like Figure 8 As shown, in a specific embodiment of the present invention, the stress birefringence of a calcium fluoride crystal with a diameter of φ200mm×55mm after annealing is demonstrated using the adaptive annealing crucible of Embodiment 1 or Embodiment 2. The stress birefringence of a calcium fluoride crystal with a diameter of φ200mm×55mm after annealing is reduced to 4.9nm / cm using the adaptive annealing crucible of the present invention.

[0080] In another specific embodiment of the present invention, a conventional crucible (e.g., a cylindrical crucible) is used, and the same annealing process is employed to anneal calcium fluoride crystals with a diameter of φ200mm × 55mm. After testing, the following results were obtained: Figure 9 The stress birefringence values ​​shown indicate that the maximum stress birefringence of calcium fluoride crystals after annealing using a conventional crucible is 15.47 nm / cm. Comparing the two sets of data above, the adaptive annealing crucible of this invention can effectively improve the uniformity of large-size calcium fluoride crystals after annealing.

[0081] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0082] 1. The inner cylinder of the crucible is composed of multiple segmented structures, which makes assembly and disassembly more convenient than traditional one-piece crucibles;

[0083] 2. By moving the segmented structure of the inner cylinder of the crucible to change the diameter of the crucible, the diameter of the crucible opening can be increased, which facilitates the placement and removal of crystals.

[0084] 3. The upper and lower adaptive layers between the inner cylinder of the crucible and the crucible lid and the crucible base can provide a buffer gap for the expansion and contraction of the crystal;

[0085] 4. An adaptive annealing crucible of appropriate size can be selected based on the size, coefficient of thermal expansion and annealing temperature of large-size fluoride crystals;

[0086] 5. By adding elastic material to the adaptive layer, the problem of insufficient stress release caused by crystal extrusion during annealing is effectively solved;

[0087] 6. By using a guiding structure to limit the expansion direction of the inner cylinder of the crucible, the expansion and contraction of the crystal proceeds along the direction defined by the guiding structure, which can effectively prevent the crystal from shifting during subsequent operations.

[0088] The above provides a detailed description of the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

[0089] Throughout this specification, the terms "an embodiment," "embodiment," or "specific embodiment" refer to a particular feature, structure, or characteristic described in connection with an embodiment that is included in at least one embodiment of the invention, but not necessarily in all embodiments. Therefore, the various representations of the phrases "in one embodiment," "in an embodiment," or "in a specific embodiment" in different places throughout the specification do not necessarily refer to the same embodiment. Furthermore, a particular feature, structure, or characteristic of any specific embodiment of the invention can be combined with one or more other embodiments in any suitable manner. It should be understood that other variations and modifications of the embodiments described and illustrated herein may be based on the teachings herein and will be considered part of the spirit and scope of the invention.

[0090] It should also be understood that one or more of the elements shown in the figures may be implemented in a more separate or more integrated manner, or may even be removed because they are inoperable in certain circumstances or provided because they may be useful for a particular application.

[0091] Furthermore, unless otherwise expressly stated, any arrows in the accompanying drawings should be considered illustrative only and not limiting. Additionally, unless otherwise stated, the term "or" as used herein is generally intended to mean "and / or". Where a term is anticipated to provide a separation or combination capability that is unclear, a combination of components or steps will also be considered as indicated.

Claims

1. A self-adapting annealing crucible for large size fluoride crystals, characterized in that, Comprise: a crucible base having a base inner ring on the radial inner side, a base outer ring on the radial outer side, and a lower adaptive layer connecting the base inner ring and the base outer ring to form an annular gap between the base inner ring and the base outer ring; a crucible cover having a cover inner ring on the radial inner side, a cover outer ring on the radial outer side, and an upper adaptive layer connecting the cover inner ring and the cover outer ring to form an annular gap between the cover inner ring and the cover outer ring; a crucible inner cylinder composed of a plurality of split structures, movably vertically arranged between the lower adaptive layer and the upper adaptive layer; and the crucible inner cylinder can expand and contract in the radial direction of the crucible inner cylinder within the lower adaptive layer and the upper adaptive layer; and a guide structure that defines the direction of expansion and contraction of the crucible inner cylinder, so that the crucible inner cylinder can expand and contract in the radial direction of the crucible inner cylinder.

2. The large-size fluoride crystal adaptive annealing crucible according to claim 1, wherein the split structure comprises a main body portion, an outer connecting portion at one end of the main body portion, and an inner connecting portion at the other end of the main body portion, and the outer connecting portion and the inner connecting portion of adjacent two split structures are connected in an overlapping manner; the outer connecting portion and the inner connecting portion of adjacent two split structures are configured to be in a connected state at all times when the crucible inner cylinder expands.

3. The self-adapting annealing crucible for large size fluoride crystals of claim 2, wherein, When the crucible inner cylinder expands or contracts, a plurality of split structures move in the radial direction within the lower adaptive layer and the upper adaptive layer, while the outer connecting portion and the inner connecting portion slide relative to each other in the circumferential direction.

4. The large-size fluoride crystal adaptive annealing crucible according to claim 1, wherein the base inner ring is higher than the lower adaptive layer, and the bottom of the crucible inner cylinder is fitted into the periphery of the base inner ring; the cover inner ring is higher than the upper adaptive layer, and the top of the crucible inner cylinder is fitted into the periphery of the cover inner ring.

5. The large-size fluoride crystal adaptive annealing crucible according to any one of claims 1-4, wherein the guide structure is a guide shaft, the guide shaft has a fixed portion and a guide portion, a plurality of fixed portions of the guide shaft are respectively fixedly connected to the upper and lower portions of the split structure in the axial direction of the crucible inner cylinder, and a plurality of guide portions of the guide shaft are respectively slidably connected to the cover outer ring and the base outer ring; a plurality of guide holes are respectively provided on the base outer ring and the cover outer ring, and a plurality of guide portions of the guide shaft are respectively slidably inserted into a plurality of guide holes; when the crucible inner cylinder expands or contracts, a plurality of guide shafts slide in the guide holes.

6. The large-size fluoride crystal adaptive annealing crucible according to any one of claims 1-4, wherein the guide structure is a guide slider, and a plurality of guide sliders are respectively arranged at the top end and the bottom end of the split structure in the axial direction of the crucible inner cylinder. The lower adaptive layer is provided with a lower guide sliding groove matched with the guide sliding block at the bottom end of the split structure, and the upper adaptive layer is provided with an upper guide sliding groove matched with the guide sliding block at the top end of the split structure, When the inner cylinder of the crucible expands or shrinks, the plurality of guide sliding blocks slide in the lower guide sliding groove and the upper guide sliding groove respectively.

7. The large-size fluoride crystal adaptive annealing crucible according to claim 5, wherein, The upper adaptive layer and the lower adaptive layer are added with elastic materials for controlling the expansion and shrinkage of the inner cylinder of the crucible.

8. The large-size fluoride crystal adaptive annealing crucible according to claim 6, wherein, The upper adaptive layer and the lower adaptive layer are added with elastic materials for controlling the expansion and shrinkage of the inner cylinder of the crucible.

9. The large-size fluoride crystal adaptive annealing crucible according to claim 7 or 8, wherein, The elastic material is graphite felt or spring.

10. The large-size fluoride crystal adaptive annealing crucible according to claim 1, wherein, The crucible cover is further provided with a gas permeable hole for discharging air and impurities in the inner cylinder of the crucible.

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