A preparation device and method for centrally shaped fluoride optical crystal

Abstract

A preparation device for a center-shaped fluoride optical crystal comprises a graphite crucible, a graphite shaped piece is arranged at the center of the graphite crucible, the length direction of the graphite shaped piece is parallel to the height direction of the graphite crucible, a first connection structure is arranged at one end of the graphite shaped piece, a second connection structure is arranged in the graphite crucible, and the first connection structure and the second connection structure are detachably connected. The present invention utilizes the characteristics that the fluoride optical crystal material and the graphite material are non-wettable and the thermal expansion coefficient is relatively large. The present invention aims at the demand for fluoride optical crystals with complex geometric structures, and according to the growth characteristics of fluoride crystals, proposes a method for growing shaped crystals, which can realize one-time molding of fluoride crystals with shaped geometric structures, and can directly grow fluoride optical crystals with shaped geometric structures in the center, thereby avoiding the subsequent cumbersome crystal processing process, greatly reducing the difficulty of crystal processing, and improving the crystal utilization rate and yield rate.

Description

Technical Field

[0001] The invention relates to the field of physics, in particular to the field of crystal growth, and in particular to a preparation device and method for a central heteromorphic fluoride optical crystal. Background Art

[0002] Calcium fluoride crystals have extremely high transmittance from the vacuum ultraviolet band to the infrared band. They also have the characteristics of low dispersion and high laser damage threshold, so they are widely used as window and lens materials. As achromatic lens materials for astronomical telescopes and window materials for ultra-strong laser devices, calcium fluoride crystals play an irreplaceable role. Magnesium fluoride (MgF 2 ) and barium fluoride (BaF 2 ) crystal is also a common fluoride optical crystal material, and is often used as optical prisms, lenses, windows, etc. in various optical systems. Fluoride crystals can be grown by the pulling method, temperature gradient method, and crucible descent method. Among the many crystal growth methods, the crucible descent method has become the preferred method for growing fluoride crystals due to its advantages such as stable temperature field and easy control. Using this method, Hellma has successfully grown large-size calcium fluoride crystals of 440mm. After the growth of fluoride crystals, large thermal stress will remain. In subsequent crystal processing, the crystals must be cut, formed, polished, etc. During the processing, the crystals are prone to cracking, resulting in reduced crystal utilization. With the continuous expansion of fluoride optical crystals in the field of optical applications, the demand for complex and special-shaped crystal components continues to rise, and the processing of fluoride optical crystals with soft and brittle characteristics brings great challenges.

[0003] Take the traditional processing scheme for machining a calcium fluoride crystal component with a circular hole as an example: first, the blank is selected and cut, then the circular hole is slowly ground using a CNC machine tool (engraving machine), and finally polished into a component. Since calcium fluoride crystals are soft and brittle crystals and are easy to dissociate, the engraving machine process can easily cause the crystal to collapse and break or even crack, resulting in processing failure; on the other hand, in order to meet the processing accuracy, it can only be processed in a single piece, which has low processing efficiency and is not conducive to large-scale production.

[0004] Fluoride crystals can be grown by the Czochralski method, the temperature gradient method, and the crucible descent method. The temperature gradient method and the crucible descent method are the most suitable technologies for large-scale production. In order to increase production capacity, crystal preparation technology is developing in the direction of growing larger sizes and growing more crystals in multiple crucibles, but there are few reports on the growth technology of crystals with special geometric structures. For such needs, the traditional solution is to achieve this through post-crystal processing, which undoubtedly increases the crystal production cycle and production cost.

[0005] Due to the low thermal conductivity and relatively large thermal expansion coefficient of fluoride crystals, the laser processing scheme has limited sample size and complex process, which also limits the application of this method.

[0006] The problems existing in the prior art are summarized as follows:

[0007] 1. Fluoride optical crystals, such as calcium fluoride, barium fluoride, magnesium fluoride, etc., are soft and brittle crystals, easy to crack during processing, and have a low processing yield rate. When used, such crystals often need to be processed into components with special-shaped geometric structures (such as round, square / triangle, etc.) in the center, which further increases the difficulty of processing.

[0008] 2. With the development of processing technology, modern processing technologies such as high-precision processing centers and laser processing have gradually been introduced into the crystal processing industry. However, there are still problems such as low processing yield and low processing efficiency for fluoride soft and brittle crystals. Summary of the invention

[0009] The purpose of the present invention is to provide a device for preparing a center-shaped fluoride optical crystal, which is intended to solve the technical problem of the difficulty in processing center-shaped fluoride optical crystals in the prior art.

[0010] The invention discloses a device for preparing a centrally shaped fluoride optical crystal, comprising a graphite crucible, wherein a graphite shaped piece is arranged at the center of the graphite crucible, wherein the length direction of the graphite shaped piece is parallel to the height direction of the graphite crucible, a first connecting structure is arranged at one end of the graphite shaped piece, and a second connecting structure is arranged in the graphite crucible, wherein the first connecting structure and the second connecting structure are detachably connected.

[0011] Furthermore, the first connection structure is an external thread arranged at one end of the graphite special-shaped part, and the second connection structure includes a connection block, and the connection block is provided with a threaded hole, and the graphite special-shaped part is connected to the threaded hole through the external thread.

[0012] Furthermore, the graphite crucible comprises a crucible cover, and the connecting block is arranged on the lower side of the crucible cover.

[0013] Furthermore, the connecting block is arranged at the bottom of the graphite crucible.

[0014] Furthermore, the cross section of the graphite special-shaped part is circular or square, diamond, triangle or other special-shaped shapes.

[0015] The present invention also provides a method for preparing a central heteromorphic fluoride optical crystal using the above device, comprising the following steps:

[0016] Step 10: Place the fluoride crystal raw material into the graphite crucible, seal the crucible cover, and wait for the crystal to grow;

[0017] Step 20: During the crystal growth process, wait for the crystal and the graphite special-shaped part to separate by themselves. Since the high-temperature solution does not wet graphite and the fluoride crystal has a large thermal expansion coefficient, the crystal and the special-shaped part mold will separate by themselves;

[0018] Step 30: After the crystal growth is completed and the crystal and the graphite shaped part are separated by themselves, the graphite shaped part and the crucible cover are removed, and the crystal is taken out and processed as needed.

[0019] Compared with the prior art, the present invention has a positive and obvious effect. The present invention utilizes the characteristics of fluoride optical crystals (such as calcium fluoride, barium fluoride, magnesium fluoride, etc.) that they are non-wettable with graphite materials and have a relatively large thermal expansion coefficient. The present invention targets the needs of fluoride optical crystals with complex geometric structures and proposes a method for growing special-shaped crystals according to the growth characteristics of fluoride crystals. The method can realize one-time molding of fluoride crystals with special-shaped geometric structures and directly grow fluoride optical crystals with special-shaped geometric structures in the center, thus avoiding the subsequent cumbersome crystal processing process, greatly reducing the difficulty of crystal processing, and improving the crystal utilization rate and yield rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic structural diagram of a device for preparing a center-shaped fluoride optical crystal of the present invention.

[0021] Figure 2 The figure is a schematic diagram of the exploded structure of a device for preparing a central heteromorphic fluoride optical crystal of the present invention. DETAILED DESCRIPTION

[0022] Example 1

[0023] like Figure 1 and Figure 2 As shown, a preparation device for a center-shaped fluoride optical crystal of the present invention comprises a graphite crucible 1, a graphite shaped piece 2 is arranged at the center position of the graphite crucible 1, the length direction of the graphite shaped piece 2 is parallel to the height direction of the graphite crucible 1, a first connecting structure 3 is arranged at one end of the graphite shaped piece 2, a second connecting structure 4 is arranged in the graphite crucible 1, and the first connecting structure 3 and the second connecting structure 4 are detachably connected.

[0024] Furthermore, the first connection structure 3 is an external thread provided at one end of the graphite profiled part 2, and the second connection structure 4 includes a connection block 7, on which a threaded hole 6 is provided, and the graphite profiled part 2 is connected to the threaded hole 6 via the external thread.

[0025] Furthermore, the graphite crucible 1 comprises a crucible cover 5 , and a connecting block 7 is arranged at the lower side of the crucible cover 5 .

[0026] Furthermore, the connecting block 7 is arranged at the bottom of the graphite crucible 1 .

[0027] Furthermore, the cross section of the graphite shaped part 2 is circular, square, diamond, triangle or other shaped shapes.

[0028] The present invention also provides a method for preparing a central heteromorphic fluoride optical crystal, comprising the following steps:

[0029] Step 10: placing the fluoride crystal raw material into the graphite crucible 1, sealing the crucible cover 5, and waiting for crystal growth;

[0030] Step 20: During the crystal growth process, since the high temperature solution does not wet the graphite and the fluoride crystal has a large thermal expansion coefficient, it is necessary to wait for the crystal and the graphite shaped part to separate by themselves;

[0031] Step 30: After the crystal growth is completed and the crystal and the graphite shaped part are separated by themselves, the graphite shaped part 2 and the crucible cover 5 are removed, and the crystal is taken out and processed as needed.

[0032] Specifically, the graphite crucible 1 can be used in crystal growth methods such as a temperature gradient method and a crucible descent method.

[0033] Specifically, the graphite crucible 1, the crucible cover 5, the fluoride crystal raw material, etc. in this embodiment all adopt the well-known scheme in the prior art, which is well known to those skilled in the art and will not be described in detail here.

[0034] The working principle of this embodiment:

[0035] The present invention utilizes the characteristics of fluoride optical crystals (such as calcium fluoride, barium fluoride, magnesium fluoride, etc.) that they do not wet graphite materials and have a relatively large thermal expansion coefficient. Aiming at fluoride optical crystals with complex geometric structures, according to the growth characteristics of fluoride crystals, a method for growing special-shaped crystals is proposed, which can realize one-time molding of fluoride crystals with special-shaped geometric structures, and can directly grow fluoride optical crystals with special-shaped geometric structures in the center, avoiding the subsequent cumbersome crystal processing process, greatly reducing the difficulty of crystal processing, and improving crystal utilization and yield rate.

[0036] The graphite special-shaped part 2 is detachably connected to the graphite crucible 1, so that the graphite special-shaped part 2 can be easily installed and disassembled as well as replaced.

Claims

1. A device for preparing a centrally shaped fluoride optical crystal, It is characterized in that A graphite crucible is provided, wherein a graphite shaped piece is arranged at the center of the graphite crucible, the length direction of the graphite shaped piece is parallel to the height direction of the graphite crucible, a first connecting structure is arranged at one end of the graphite shaped piece, a second connecting structure is arranged in the graphite crucible, and the first connecting structure and the second connecting structure are detachably connected; The first connection structure is an external thread arranged at one end of the graphite special-shaped part, and the second connection structure includes a connection block, which is provided with a threaded hole, and the graphite special-shaped part is connected to the threaded hole through the external thread; the graphite crucible includes a crucible cover, and the connection block is arranged on the lower side of the crucible cover; the cross-section of the graphite special-shaped part is circular or square, diamond or triangle.

2. The device for preparing a center-shaped fluoride optical crystal according to claim 1, It is characterized in that The connecting block is arranged at the bottom of the graphite crucible.

3. A method for preparing a centrally shaped fluoride optical crystal using the device of claim 1, It is characterized in that The following steps are involved: Step 10: placing the fluoride crystal raw material into the graphite crucible, sealing the crucible cover, and waiting for the crystal to grow. The graphite crucible adopts the crystal growth method of the crucible descent method and the temperature gradient method; Step 20: During the crystal growth process, wait for the crystal and the graphite shaped part to separate by themselves; Step 30: After the crystal growth is completed and the crystal and the graphite shaped part are separated by themselves, the graphite shaped part and the crucible cover are removed, and the crystal is taken out and processed as needed.

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