A double-layer rotating inner baffle for crystal growth using hydrothermal temperature difference method

Abstract

The invention discloses a double-layer rotating inner baffle for crystal growth by a hydrothermal temperature difference method, which is placed in the inner cavity of a hydrothermal autoclave and comprises an upper baffle and a lower baffle of equal size and overlapping axis lines; the spacing between the upper baffle (1) and the lower baffle (3) is an adjustable spacing; the upper baffle (1) is provided with an upper baffle descending through hole (6-1) and an upper baffle ascending through hole (6-2); the lower baffle (3) is provided with a lower baffle descending through hole (6-3) and a lower baffle ascending through hole (6-4); the corresponding orthographic projections of the upper baffle descending through hole (6-1) and the lower baffle descending through hole (6-3) and the axis line of the upper baffle (1) have an angle greater than 0° to less than 90°. The invention changes the convection state of the mineralizer liquid by adjusting the spacing of the double-layer baffles and limiting the rotation angle of the upper and lower plate through holes, so that the crystal growth rate in the growth zone of the autoclave tends to be consistent, thereby improving the crystallization uniformity of the crystal.

Description

Technical Field

[0001] The invention relates to the technical field of hydrothermal crystal growth, in particular to an inner baffle located between a crystal growth zone and a raw material dissolution zone of an autoclave. Background Art

[0002] The hydrothermal temperature difference method is a widely used crystal growth technology. The main principle of this technology is to imitate the physical and chemical conditions of natural mineral formation in a sealed autoclave, and use the principle that mineralizers formed by water and chemical reagents of corresponding concentrations under high pressure and specific temperature can dissolve certain natural minerals. By artificially controlling the temperature difference between the upper and lower parts of the autoclave, the mineralizer aqueous solution that has dissolved the minerals in the bottom high-temperature area passes through a baffle with a certain opening rate in the autoclave, and rises to the crystal growth area with a relatively low temperature by convection, forming solute supersaturation, and crystallization growth occurs on the seed chip. Then the solution returns to the raw material dissolution area to continue dissolving the raw material. After a continuous dissolution-rise-crystallization-descent-re-dissolution reciprocating cycle, the raw material at the bottom eventually grows into the upper crystal.

[0003] The specific implementation method is: an inner baffle is set in the autoclave to divide the autoclave into a raw material dissolution zone (lower part) with a high temperature and a crystal growth zone (upper part) with a lower temperature. The raw material dissolution zone and the crystal growth zone of the autoclave are each provided with a corresponding heating device, and the temperature of the two zones is guaranteed by controlling the heating power. The outer diameter of the inner baffle maintains a gap with the inner wall of the autoclave, a mineralizer rising through hole is set at the edge of the inner baffle, and a mineralizer descending through hole is also set on the inner baffle. The raw material basket containing the raw material is immersed in the mineralizer solution, and the mineralizer solution is in direct contact with the raw material. The mineralizer solution that has dissolved the raw material convects to the crystal growth zone (low temperature zone) through the mineralizer rising through hole and the gap, forming an oversaturated state, and finally forming crystallization growth on the seed chip, and then the mineralizer returns to the raw material dissolution zone through the mineralizer descending through hole of the inner baffle to re-form the oversaturated dissolution.

[0004] In the traditional hydrothermal temperature difference crystal growth process, only a single-layer inner baffle is used. The opening rate of the single-layer inner baffle is calculated according to the inner diameter of the autoclave and the surface area of ​​the seed crystal sheet suspended above the autoclave. The mineralizer convection channel is realized by drilling holes in the inner baffle.

[0005] The disadvantage of a single-layer baffle is that it cannot control the convection state of the mineralizer in the autoclave. The mineralizer directly enters the low-temperature zone through the holes in the baffle and directly impacts the seed crystal, causing the crystal growth rate near the raw material dissolution zone to slow down, while the crystal growth rate in the upper part of the crystal growth zone to speed up, resulting in inconsistent crystal growth rates in the upper and lower parts of the same autoclave, causing a decrease in crystal uniformity and Q value indicators.

[0006] In addition, the distance between the single-layer inner baffle and the inner wall of the autoclave is fixed by the positioning column on the upper part of the seed crystal rack. The defect of this method is that due to the deformation of the seed crystal rack of 2.5-3 meters in length, the inner baffle may be non-concentric with the inner cavity of the autoclave, resulting in uneven radial convection, and ultimately causing different crystal growth rates in the diameter direction of the autoclave, affecting the uniformity of the crystal. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a double-layer rotating inner baffle plate for crystal growth by a hydrothermal temperature difference method which can improve the uniformity of crystal crystallization.

[0008] In order to solve the above technical problems, the present invention provides a double-layer rotating inner baffle for hydrothermal temperature difference method crystal growth, which is placed in the inner cavity of a hydrothermal autoclave and includes an upper baffle and a lower baffle of equal size and whose axis lines coincide with each other; the upper baffle is located directly above the lower baffle, and the spacing between the upper baffle and the lower baffle is an adjustable spacing, and a baffle connecting column is arranged between the upper baffle and the lower baffle, and the baffle connecting column is connected to the upper baffle and the lower baffle respectively;

[0009] At least two circles of mineralizer descending channels are arranged on the upper baffle plate, each circle of the mineralizer descending channels includes at least two upper baffle descending through holes evenly arranged, and a circle of mineralizer ascending channels is evenly arranged at the edge of the upper baffle plate, and the mineralizer ascending channels include at least two upper baffle ascending through holes evenly arranged; the mineralizer ascending channels are located at the periphery of the mineralizer descending channels;

[0010] The lower baffle plate is provided with a lower baffle plate descending through hole and a lower baffle plate ascending through hole respectively;

[0011] The diameter and number of the descending through holes of the lower baffle are the same as those of the descending through holes of the upper baffle.

[0012] The aperture and number of the rising through holes of the lower baffle are the same as those of the rising through holes of the upper baffle.

[0013] The positional relationship between each lower baffle descending through hole and each lower baffle ascending through hole is the same as the positional relationship between each upper baffle descending through hole and each upper baffle ascending through hole;

[0014] The angle between the corresponding orthographic projections of the upper baffle descending through hole and the lower baffle descending through hole and the axis line of the upper baffle is greater than 0° and less than 90°.

[0015] That is, the orthographic projection of the descending through hole of the upper baffle plate and the orthographic projection of the descending through hole of the lower baffle plate are rotated about the axis of the baffle plate to form an angle greater than 0° and less than 90°.

[0016] As an improvement of the double-layer rotating inner baffle for hydrothermal temperature difference method crystal growth of the present invention:

[0017] At least two sets of positioning bracket assemblies are evenly arranged at the edge of the upper baffle, and the positioning bracket assemblies are used to adjust the axis line of the upper baffle to coincide with the axis line of the hydrothermal autoclave cavity, so as to form a gap between the upper baffle and the side wall of the hydrothermal autoclave cavity.

[0018] As a further improvement of the double-layer rotating inner baffle for hydrothermal temperature difference method crystal growth of the present invention:

[0019] Each positioning bracket assembly includes a positioning bracket and a screw threadedly connected to the positioning bracket. The positioning bracket is fixedly connected to the upper baffle (for example, welded), and the gap between the upper baffle and the side wall of the hydrothermal autoclave cavity is made uniform by adjusting the screw.

[0020] That is, the gap between the entire double-layer rotating inner baffle plate and the inner cavity of the hydrothermal autoclave is made uniform by adjusting the screws.

[0021] As a further improvement of the double-layer rotating inner baffle for hydrothermal temperature difference method crystal growth of the present invention:

[0022] The sum of the hole areas of the descending through holes of the upper baffle is called the descending convection cross-sectional area of ​​the autoclave;

[0023] The sum of the hole area of ​​the upper baffle rising through hole and the gap area formed between the upper baffle and the side wall of the hydrothermal autoclave cavity is called the autoclave rising convection cross-sectional area;

[0024] The sum of the descending convection cross-sectional area of ​​the autoclave and the ascending convection cross-sectional area of ​​the autoclave accounts for 5%-8% of the cross-sectional area of ​​the inner cavity of the hydrothermal autoclave (this is called the baffle opening ratio).

[0025] As a further improvement of the double-layer rotating inner baffle for hydrothermal temperature difference method crystal growth of the present invention:

[0026] The descending convection cross-sectional area of ​​the autoclave = the ascending convection cross-sectional area of ​​the autoclave.

[0027] As a further improvement of the double-layer rotating inner baffle for hydrothermal temperature difference method crystal growth of the present invention:

[0028] The baffle connecting column is connected to the upper baffle and the lower baffle through threads.

[0029] As a further improvement of the double-layer rotating inner baffle for hydrothermal temperature difference method crystal growth of the present invention:

[0030] The adjustable distance between the upper baffle and the lower baffle is 80-150mm.

[0031] As a further improvement of the double-layer rotating inner baffle for hydrothermal temperature difference method crystal growth of the present invention:

[0032] A seed crystal rack connecting bracket for connecting the seed crystal rack is provided on the upper surface of the upper baffle.

[0033] As a further improvement of the double-layer rotating inner baffle for hydrothermal temperature difference method crystal growth of the present invention:

[0034] Each circle of the mineralizer descending channel includes four upper baffle descending through holes evenly arranged, and one circle of the mineralizer ascending channel includes four upper baffle ascending through holes evenly arranged;

[0035] The corresponding orthographic projections of the upper baffle plate descending through holes and the lower baffle plate descending through holes and the axis of the upper baffle plate are at an angle of 5° to 45°;

[0036] That is, the orthographic projection of the descending through hole of the upper baffle plate and the orthographic projection of the descending through hole of the lower baffle plate are rotated by 5° to 45° about the axis of the baffle plate.

[0037] As a further improvement of the double-layer rotating inner baffle for hydrothermal temperature difference method crystal growth of the present invention:

[0038] The aperture of the descending through hole of the upper baffle is 10 to 30 mm;

[0039] The aperture of the rising through hole of the upper baffle is 10 to 30 mm.

[0040] The double-layer rotating inner baffle for hydrothermal temperature difference method crystal growth of the present invention is equivalent to the upper baffle and the lower baffle being rotated at a certain angle, and a certain distance is maintained between the upper baffle and the lower baffle (the distance can be adjusted according to actual needs). Therefore, the mineralizer forms a buffer in the double-layer baffle, and at the same time, the through hole after the upper and lower plates rotate at an angle changes the state of the mineralizer directly impacting the bottom crystal in the growth zone, and according to the equal opening rate of the mineralizer rising and descending channels, the convection state of the mineralizer in the autoclave is effectively changed, and the area of ​​the mineralizer rising and returning (descending) channels is achieved to be consistent, so that the temperature difference in the crystal growth zone is reduced, and the crystal growth thickness is uniform, which solves the technical problem of thick crystals on the upper part of the autoclave and thin crystals on the lower part caused by the existing single-layer inner baffle process.

[0041] In the present invention, the positioning bracket assembly arranged at the edge of the upper baffle plate is used to adjust the distance between the inner wall of the autoclave and the baffle plate through screws, and ensure that the distance is equal all around. Compared with the structure of the prior art, the structure of the present invention has the following technical advantages: it can ensure the uniformity of the mineralizer rising channel, so that the seed sheets in all directions of the crystal growth zone are uniformly contacted with the supersaturated mineralizer solution, thereby forming a uniform growth rate and meeting the optical uniformity index of the crystal.

[0042] The double-layer baffle and the structure of the upper and lower plate through holes rotated at a certain angle adopted in the present invention can change the state of direct convection of the mineralizer, so that turbulence is formed in the double-layer baffle and a spiral convection rising state is formed through the rotating through holes, which effectively increases the contact area between the mineralizer and the seed chip, and at the same time, uniformly contacts with the seed chip in the entire growth area, achieving uniform crystallization, making the uniformity index of the crystal more consistent, and improving the crystal quality.

[0043] In summary, the double-layer rotating inner baffle for crystal growth by the thermal temperature difference method of the present invention changes the convection state of the mineralizer liquid by adjusting the spacing of the double-layer baffle and limiting the rotation angle of the through holes of the upper and lower plates, so that the crystal growth rate in the growth zone of the autoclave tends to be consistent, and the crystallization uniformity of the crystal is improved. The present invention can adapt to different hydrothermal crystal growth process conditions.

[0044] The present invention is applicable to all hydrothermal temperature difference crystal growth processes. For some crystal growth processes with negative dissolution temperature, i.e., crystal growth processes with the crystal growth zone at the lower part of the autoclave and the raw material dissolution zone at the upper part of the autoclave, it can be used by simply turning the double-layer rotating inner baffle upside down. That is, after the seed crystal rack is installed on the seed crystal rack connecting bracket located on the upper surface of the upper baffle, the seed crystal rack is placed downward and the double-layer rotating inner baffle is placed upward in the autoclave. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The specific implementation modes of the present invention are further described in detail below with reference to the accompanying drawings.

[0046] Figure 1 This is a schematic diagram of the double-layer rotating inner baffle structure of the present invention;

[0047] Figure 2 for Figure 1 A view of the upper baffle 1 in FIG.

[0048] Figure 3 for Figure 1 A view of the lower baffle 3 in FIG.

[0049] Figure 4 for Figure 1 main view. DETAILED DESCRIPTION

[0050] The present invention will be further described below in conjunction with specific embodiments.

[0051] Example 1: A double-layer rotating inner baffle plate for hydrothermal temperature difference method crystal growth is placed in the inner cavity of a hydrothermal autoclave, such as Figure 1 to Figure 4 As shown, it includes an upper baffle 1, a baffle connecting column 2 and a lower baffle 3; the upper baffle 1 is located directly above the lower baffle 3, and the axis (central axis) of the upper baffle 1 coincides with the axis of the lower baffle 3.

[0052] The upper baffle 1 and the lower baffle 3 are equal in size, that is, they have the same shape and size.

[0053] The upper baffle 1 is circular, and is provided with at least two concentric circles of mineralizer descending channels, each circle of which includes at least two upper baffle descending through holes 6-1 evenly arranged; a circle of mineralizer ascending channels is evenly arranged at the edge of the upper baffle 1, and a circle of mineralizer ascending channels includes at least two upper baffle ascending through holes 6-2 evenly arranged; the mineralizer ascending channels are located at the periphery of the mineralizer descending channels; the mineralizer ascending channels are concentric circles with the mineralizer descending channels. The apertures of all upper baffle descending through holes 6-1 are the same, and the apertures of all upper baffle ascending through holes 6-2 are the same.

[0054] like Figure 1 to Figure 3 As shown, three circles of mineralizer descending channels are provided on the upper baffle plate 1 in the form of concentric circles, and each circle of the mineralizer descending channel includes four upper baffle descending through holes 6-1 evenly arranged; therefore, a total of 12 upper baffle descending through holes 6-1 are provided on the upper baffle plate 1; one circle of the mineralizer ascending channel includes four upper baffle ascending through holes 6-2 evenly arranged, therefore, a total of four upper baffle ascending through holes 6-2 are provided on the upper baffle plate 1.

[0055] The upper baffle descending holes 6-1 on the adjacent circles of the mineralizer descending channels are rotated at an angle of 45°, and the upper baffle descending holes 6-1 on the outermost circle of the mineralizer descending channels and the upper baffle ascending holes 6-2 on the mineralizer ascending channels are rotated at an angle of 45°.

[0056] According to the above-mentioned upper baffle 1, a circular plate with the same structure, shape and size is set as the lower baffle 3; that is, 12 lower baffle descending through holes 6-3 and 4 lower baffle ascending through holes 6-4 are respectively set on the lower baffle 3; the aperture of the lower baffle descending through hole 6-3 is equal to the aperture of the upper baffle descending through hole 6-1, and the lower baffle ascending through hole 6-4 is equal to the aperture of the upper baffle ascending through hole 6-2. The positional relationship between each lower baffle descending through hole 6-3 and each lower baffle ascending through hole 6-4 is the same as the positional relationship between each upper baffle descending through hole 6-1 and each upper baffle ascending through hole 6-2.

[0057] The corresponding orthographic projections of the upper baffle descending hole 6-1 and the lower baffle descending hole 6-3 form a certain angle with the axis line, and the angle is 5 to 45°; that is, the orthographic projections of the upper baffle descending hole 6-1 and the lower baffle descending hole 6-3 are rotated 5 to 45° with the axis line of the baffle.

[0058] The sum of the hole areas of the upper baffle descending through hole 6-1 is called the autoclave descending convection cross-sectional area; the sum of the hole areas of the upper baffle ascending through hole 6-2 and the gap area formed between the upper baffle 1 and the side wall of the hydrothermal autoclave cavity is called the autoclave ascending convection cross-sectional area; the autoclave descending convection cross-sectional area + the autoclave ascending convection cross-sectional area = 5%-8% of the autoclave cavity cross-sectional area, which is called the baffle opening rate. And, the autoclave descending convection cross-sectional area = the autoclave ascending convection cross-sectional area.

[0059] The upper baffle 1 is connected to the lower baffle 3 via a baffle connecting column 2; the baffle connecting column 2 is located between the upper baffle 1 and the lower baffle 3, and the distance between the upper baffle 1 and the lower baffle 3 is an adjustable distance, and the adjustable distance is 80-150mm.

[0060] The implementation of adjustable spacing can be easily realized by technicians in this industry, for example, it can be specifically as follows:

[0061] The baffle connecting column 2 is a bolt with threads at both ends, and the outer diameter of the thread at the upper end is smaller than the column diameter of the baffle connecting column 2, thereby forming a step surface that serves as a limit. Four positioning nuts 7-2 are evenly arranged on the lower baffle 3, and the bottoms of the four baffle connecting columns 2 are fixedly connected to the lower baffle 3 by threaded connection. The upper baffle 1 is provided with four positioning through holes 7-1 corresponding to the four baffle connecting columns 2. After the top of the baffle connecting column 2 passes through the positioning through hole 7-1, it is fixed with the corresponding nut, thereby realizing the fixed connection between the baffle connecting column 2 and the upper baffle 1; at this time, the lower surface of the upper baffle 1 contacts the step surface. The distance between the upper baffle 1 and the lower baffle 3 can be adjusted by replacing baffle connecting columns 2 of different lengths.

[0062] At least two sets of positioning bracket assemblies 5 are evenly arranged at the edge of the upper baffle 1, and the positioning bracket assemblies 5 are used to adjust the upper baffle 1 to coincide with the axis of the hydrothermal autoclave, so that a uniform gap is formed between the side wall of the upper baffle 1 and the side wall of the inner cavity of the hydrothermal autoclave. Figure 1 to Figure 3 As shown, a total of 4 sets of positioning bracket assemblies are provided.

[0063] Each set of positioning bracket assembly 5 includes a positioning bracket and a screw 51 threadedly connected to the positioning bracket; the positioning bracket is welded and fixed to the upper baffle 1, and the double-layer rotating inner baffle (upper baffle 1, lower baffle 3) is made to coincide with the axis of the hydrothermal autoclave by adjusting the screw 51 on the positioning bracket assembly 5.

[0064] A seed crystal rack connecting bracket 4 for connecting the seed crystal rack is provided on the upper surface of the upper baffle plate 1. The seed crystal rack connecting bracket 4 is located in the area enclosed by the mineralizer ascending channel and the outermost mineralizer descending channel.

[0065] When the double-layer rotating inner baffle of the present invention is actually used:

[0066] A raw material basket containing raw materials and a mineralizer solution are pre-set in the inner cavity of the hydrothermal autoclave, and the raw materials are immersed in the mineralizer solution. First, according to actual needs, set the distance between the upper baffle 1 and the lower baffle 3, then fix the seed crystal rack with the seed crystal plate suspended on the seed crystal rack connecting bracket 4, and then place the entire double-layer rotating inner baffle in the inner cavity of the hydrothermal autoclave. At this time, the lower baffle 3 is placed on the raw material basket. Then, by adjusting the screws 51 on the positioning bracket assembly 5 (the top of the screw 51 is against the inner wall of the hydrothermal autoclave), it is ensured that the edge of the double-layer baffle is evenly spaced from the inner wall of the autoclave; that is, it is ensured that the double-layer rotating inner baffle coincides with the axis of the inner cavity of the hydrothermal autoclave. The side wall of the upper baffle 1 maintains a gap of 2-4mm with the inner wall of the hydrothermal autoclave, so that the mineralizer rises to the crystallization zone through the gap. That is, the gap, the upper baffle rising through hole 6-2, and the lower baffle rising through hole 6-4 together form an ascending channel for the mineralizer; and the upper baffle descending through hole 6-1 and the lower baffle descending through hole 6-3 together form a descending channel for the mineralizer.

[0067] The area above the double-layer rotating inner baffle is the crystal growth area, and the area below the double-layer rotating inner baffle is the raw material dissolution area. The outer wall of the metal hydrothermal autoclave is provided with a resistance heating belt. The mineralizer in the autoclave receives the heat energy from the autoclave wall and convects upward along the rising channel of the mineralizer into the crystal growth area to form a supersaturated state, thereby forming crystallization growth on the seed sheet, and then returns to the raw material dissolution area through the descending channel of the mineralizer.

[0068] The upper baffle 1 and the lower baffle 3 are both made of 2mm thick 304 stainless steel; the column diameter of the baffle connecting column 2 is φ6mm.

[0069] Experiment 1: In a φ380×4630 (effective height) mm autoclave, a double-layer rotating baffle with a baffle opening ratio of 6.66% was used, and the openings of the upper and lower plates were rotated 45° about the center of the baffle circle (i.e., the orthographic projection of the upper baffle descending hole 6-1 and the orthographic projection of the lower baffle descending hole 6-3 were rotated 45° about the axis of the baffle), the temperature of the dissolution zone was 375°C, the temperature of the growth zone was 340°C, the upper baffle descending hole 6-1, the upper baffle ascending hole 6-2, the lower baffle descending hole 6-3, The apertures of the rising through holes 6-4 of the lower baffle are all 20 mm, and the distance between the upper baffle 1 and the lower baffle 3 is 60 mm; the seed crystal shape in the crystal growth zone is 70×210 mm (70 mm is the positive electric axis direction, that is, the width direction of the crystal; 210 mm is the mechanical axis direction, that is, the height direction of the crystal), totaling 250 pieces, the raw material in the raw material dissolution zone is molten quartz, the mineralizer is sodium hydroxide and sodium carbonate, the concentrations of which are 1.0 N and 0.15 N, and the growth pressure is 145 MPa.

[0070] After 62 days, the thickness of the crystals in the growth zone (in the direction of the optical axis, perpendicular to the width direction) was 28 mm on average for the top layer and 24 mm on average for the bottom layer. There were 99 first-level inclusions, 81 second-level inclusions, and 70 third-level inclusions.

[0071] Note: Inclusions are identified according to the national standard GB / T7895-2008 "Artificial Optical Quartz Crystal" 4.5.

[0072] Experiment 2: Change the rotation angle in Experiment 1 from 45° to 30°, and the rest is the same as Experiment 1.

[0073] The results are as follows: the average thickness of the top layer of the growth zone crystal is 30mm, and the average thickness of the bottom layer is 23mm. There are 90 first-level inclusions, 82 second-level inclusions, and 78 third-level inclusions.

[0074] Experiment 3: Change the rotation angle in Experiment 1 from 30° to 0°, and the rest is the same as Experiment 1.

[0075] The results are as follows: the average thickness of the top layer of the growth zone crystal is 31mm, and the average thickness of the bottom layer is 22mm. There are 80 first-level inclusions, 78 second-level inclusions, and 92 third-level inclusions.

[0076] Comparative experiment 1: The double-layer rotating baffle in experiment 1 is changed to only the upper baffle 1, that is, the use of the baffle connecting column 2 and the lower baffle 3 is eliminated, and the upper baffle 1 is directly placed on the raw material basket. The rest is the same as experiment 1.

[0077] The results are as follows: the average thickness of the top layer of the growth zone crystal is 33mm, and the average thickness of the bottom layer is 21mm. There are 78 first-level inclusions, 72 second-level inclusions, and 100 third-level inclusions.

[0078] Finally, it should be noted that the above examples are only some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and there are many variations. All variations that can be directly derived or associated with the content disclosed by a person skilled in the art should be considered as the protection scope of the present invention.

Claims

1. A double-layer rotating inner baffle plate used for hydrothermal temperature difference method crystal growth is placed in the inner cavity of a hydrothermal autoclave, and is characterized by: The invention comprises an upper baffle (1) and a lower baffle (3) of equal size and with coincident axial lines; the upper baffle (1) is located directly above the lower baffle (3), and the distance between the upper baffle (1) and the lower baffle (3) is adjustable; a baffle connecting column (2) is arranged between the upper baffle (1) and the lower baffle (3), and the baffle connecting column (2) is respectively connected to the upper baffle (1) and the lower baffle (3); At least two circles of mineralizer descending channels are provided on the upper baffle (1), each circle of the mineralizer descending channels comprises at least two upper baffle descending through holes (6-1) evenly arranged, and a circle of mineralizer ascending channels is evenly arranged at the edge of the upper baffle (1), the mineralizer ascending channels comprises at least two upper baffle ascending through holes (6-2) evenly arranged; the mineralizer ascending channels are located at the periphery of the mineralizer descending channels; A lower baffle plate descending through hole (6-3) and a lower baffle plate ascending through hole (6-4) are respectively provided on the lower baffle plate (3); The aperture and number of the lower baffle plate descending through holes (6-3) are the same as the aperture and number of the upper baffle plate descending through holes (6-1). The aperture and number of the lower baffle rising through holes (6-4) are the same as the aperture and number of the upper baffle rising through holes (6-2). The positional relationship between each lower baffle descending through hole (6-3) and each lower baffle ascending through hole (6-4) is the same as the positional relationship between each upper baffle descending through hole (6-1) and each upper baffle ascending through hole (6-2); The angle between the orthographic projections of the corresponding upper baffle descending through holes (6-1) and lower baffle descending through holes (6-3) and the axis of the upper baffle (1) is greater than 0° and less than 90°.

2. The double-layer rotating inner baffle for hydrothermal temperature difference method crystal growth according to claim 1 is characterized in that: At least two sets of positioning bracket assemblies (5) are evenly arranged at the edge of the upper baffle (1), and the positioning bracket assemblies (5) are used to adjust the axis center line of the upper baffle (1) to coincide with the axis center line of the hydrothermal autoclave cavity, so that a gap is formed between the upper baffle (1) and the side wall of the hydrothermal autoclave cavity.

3. The double-layer rotating inner baffle for hydrothermal temperature difference method crystal growth according to claim 2 is characterized in that: Each set of positioning bracket components (5) comprises a positioning bracket and a screw (51) threadedly connected to the positioning bracket. The positioning bracket is fixedly connected to the upper baffle (1). The gap between the upper baffle (1) and the side wall of the hydrothermal autoclave cavity is made uniform by adjusting the screw (51).

4. The double-layer rotating inner baffle for hydrothermal temperature difference method crystal growth according to claim 2 or 3, characterized in that: The sum of the hole areas of the descending through holes (6-1) of the upper baffle is called the descending convection cross-sectional area of ​​the autoclave; The sum of the hole area of ​​the upper baffle rising through hole (6-2) and the gap area formed between the upper baffle (1) and the side wall of the hydrothermal autoclave inner cavity is called the autoclave rising convection cross-sectional area; The sum of the descending convection cross-sectional area of ​​the autoclave and the ascending convection cross-sectional area of ​​the autoclave accounts for 5%-8% of the cross-sectional area of ​​the inner cavity of the hydrothermal autoclave.

5. The double-layer rotating inner baffle for hydrothermal temperature difference method crystal growth according to claim 4 is characterized in that: The descending convection cross-sectional area of ​​the autoclave = the ascending convection cross-sectional area of ​​the autoclave.

6. The double-layer rotating inner baffle for hydrothermal temperature difference method crystal growth according to claim 5 is characterized in that: The baffle connecting column (2) is connected to the upper baffle (1) and the lower baffle (3) through threads.

7. The double-layer rotating inner baffle for hydrothermal temperature difference method crystal growth according to claim 6 is characterized in that: The adjustable distance between the upper baffle plate (1) and the lower baffle plate (3) is 80-150 mm.

8. The double-layer rotating inner baffle for hydrothermal temperature difference method crystal growth according to claim 7 is characterized in that: A seed crystal rack connecting bracket (4) for connecting the seed crystal rack is provided on the upper surface of the upper baffle (1).

9. The double-layer rotating inner baffle for hydrothermal temperature difference method crystal growth according to any one of claims 1 to 8, characterized in that: Each circle of the mineralizer descending channel includes four upper baffle descending through holes (6-1) evenly arranged, and one circle of the mineralizer ascending channel includes four upper baffle ascending through holes (6-2) evenly arranged; The angle between the orthographic projections of the corresponding upper baffle descending through holes (6-1) and lower baffle descending through holes (6-3) and the axis of the upper baffle (1) is 5° to 45°.

10. The double-layer rotating inner baffle for hydrothermal temperature difference method crystal growth according to any one of claims 1 to 9, characterized in that: The aperture of the descending through hole (6-1) of the upper baffle plate is 10 to 30 mm; The aperture of the upper baffle rising through hole (6-2) is 10 to 30 mm.

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