Method for growing LSGM single crystal by Czochralski method

Abstract

The invention discloses a method for growing an LSGM single crystal by a pulling method, and belongs to the technical field of single crystal growth. The method provided by the invention comprises the following steps: proportioning La2O3, SrCO3, Ga2O3 and MgO according to a mass ratio of (60.5 to 62.0): (2.5 to 3.5): (36.2 to 38.2): (0.6 to 1.2), mixing, pressing, and then carrying out solid-phase sintering to obtain an LSGM blank; then growing the LSGM single crystal by adopting a pulling method; the atmosphere adopted in the growth process is a mixed atmosphere of oxygen, carbon dioxide and nitrogen, and the volume ratio of the oxygen to the carbon dioxide to the nitrogen is (0.5-2): (65-75): (25-35). According to the method, the problems of volatilization and decomposition of Ga2O3 in the process of growing the LSGM single crystal by the Czochralski method are effectively solved, and the high-quality LSGM single crystal meeting the requirement of the substrate can be grown.

Description

Technical Field

[0001] The present invention relates to the technical field of single crystal growth, and in particular to a method for growing LSGM single crystals by the Czochralski method. Background Art

[0002] The information disclosed in the background art of the present invention is only intended to increase the understanding of the overall background of the present invention, and is not necessarily regarded as an admission or an implication in any form that this information constitutes the prior art that has become well-known to those of ordinary skill in the art.

[0003] LSGM (La 0.95 Sr 0.05 Ga 0.95 Mg 0.05 O 3-δ ) is a fast ion conductor material with a perovskite structure, which endows it with good ion transport performance and chemical stability, exhibits excellent pure oxygen ion conductivity in the medium temperature range, and is widely used in fields such as solid oxide fuel cells (SOFCs) and solid oxide electrolyzers (SOECs). At present, the research reports on the preparation of LSGM single crystals are extremely limited.

[0004] The patent with publication number CN107268073A reported a method for growing LSGM fast ion conductor single crystals by the Czochralski method. In this patent, LSGM single crystals with a diameter of 2 inches were successfully grown by the Czochralski method in an argon atmosphere. Ghislain et al. (Journal of The Electrochemical Society, 2016, 163: F1189 - F97) successfully grew LSGM single crystals with a diameter of 20 mm and a length of about 35 mm by the Czochralski method in a nitrogen atmosphere at a pulling rate of 2.5 mm / h and a rotation speed of 20 rpm.

[0005] However, the inventors found that when nitrogen or argon is used as the growth atmosphere, the stability of Ga2O3 is poor, and the volatilization and decomposition phenomena are serious at high temperatures, resulting in a decrease in the content of Ga2O3 in the raw materials, and the decomposed Ga will form an alloy with the iridium crucible and the mold, resulting in the loss of precious metals. Therefore, how to provide a growth method that can inhibit the decomposition of Ga and obtain high-quality LSGM single crystals is an urgent problem to be solved. Summary of the Invention

[0006] In view of this, the present invention provides a method for growing LSGM single crystals by the Czochralski method. The present invention can grow high-quality and large-size LSGM single crystals quickly and stably, and effectively slow down the iridium loss.

[0007] The present invention provides a method for growing LSGM single crystals by the Czochralski method, including the following steps:

[0008] La2O3, SrCO3, Ga2O3 and MgO are mixed in a mass ratio of (60.5-62.0):(2.5-3.5):(36.2-38.2):(0.6-1.2), pressed after mixing, and then solid-phase sintered to obtain LSGM blanks;

[0009] Then, the LSGM single crystal is grown by the Czochralski method; the atmosphere used in the growth process is a mixed atmosphere of oxygen, carbon dioxide and nitrogen, and the volume ratio of oxygen, carbon dioxide and nitrogen is (0.5-2):(65-75):(25-35).

[0010] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0011] The present invention grows LSGM single crystals by the Czochralski method in a mixed atmosphere of oxygen, carbon dioxide and nitrogen. At the same time, a slight excess of Ga2O3 raw material is used to compensate for the high-temperature volatilization loss. This effectively overcomes the volatilization and decomposition problems of Ga2O3 during the Czochralski method for growing LSGM single crystals, and effectively slows down the loss of the iridium crucible, so that high-quality LSGM single crystals that meet substrate requirements can be grown. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute undue limitations thereon. It is obvious that one of ordinary skill in the art could derive other drawings based on these drawings without inventive effort.

[0013] Figure 1 is a sample photo of the LSGM single crystal of Example 1 of the present invention;

[0014] Figure 2 is the X-ray Laue diffraction pattern of the lower part of the equal-diameter portion of the LSGM single crystal of Example 1 of the present invention;

[0015] Figure 3 is the X-ray Laue diffraction pattern of the lower part of the equal-diameter portion of the LSGM single crystal of Example 1 of the present invention;

[0016] Figure 4 is the X-ray diffraction pattern of the LSGM single crystal of Example 1 of the present invention and the LSGM blank obtained by high-temperature sintering in step (1);

[0017] Figure 5 This is the X-ray Laue diffraction pattern of the equal diameter portion of the LSGM single crystal of Comparative Example 1 of the present invention;

[0018] Figure 6It is the X-ray Laue diffraction pattern of the isodiametric part of the LSGM single crystal in Comparative Example 2 of the present invention;

[0019] Figure 7 It is the X-ray Laue diffraction pattern of the isodiametric part of the LSGM single crystal in Comparative Example 3 of the present invention;

[0020] Figure 8 It is the conductivity change diagram of the LSGM single crystals in Example 1 and Comparative Examples 1-3 of the present invention at different temperatures. Detailed implementation manners

[0021] It should be noted that the following detailed descriptions are all exemplary and are intended to provide further explanations of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0022] The present invention provides a method for growing LSGM single crystals by the Czochralski method, which includes the following steps:

[0023] Mix La2O3, SrCO3, Ga2O3 and MgO according to the mass ratio of (60.5-62.0):(2.5-3.5):(36.2-38.2):(0.6-1.2), press after mixing, and then perform solid-phase sintering to obtain an LSGM blank;

[0024] Then grow the LSGM single crystal by the Czochralski method; the atmosphere used in the growth process is a mixed atmosphere of oxygen, carbon dioxide and nitrogen, and the volume ratio of oxygen, carbon dioxide and nitrogen is (0.5-2):(65-75):(25-35).

[0025] The present invention discovers that when growing LSGM single crystals in a pure nitrogen or pure argon environment, the stability of Ga2O3 is poor, the volatilization and decomposition phenomena are serious at high temperatures, and the quality of the obtained LSGM single crystals is poor. The present invention has obtained the optimal atmosphere conditions for growing LSGM single crystals by the Czochralski method through a large number of experiments. Under the condition of a mixed atmosphere of oxygen, carbon dioxide and nitrogen in a specific ratio and with a slight excess of Ga2O3 raw materials, the volatilization and decomposition problems of Ga2O3 in the process of growing LSGM single crystals by the Czochralski method can be effectively overcome, and the loss of the iridium crucible can be effectively slowed down, and high-quality LSGM single crystals meeting the substrate requirements can be grown.

[0026] The purities of La2O3, SrCO3, Ga2O3 and MgO used in the present invention are above 99.99%. The present invention does not impose special restrictions on the sources of the above raw materials with such purities. They can be obtained commercially, or the commercially obtained raw materials with lower purities can be purified to obtain high-purity raw materials. The present invention does not impose special restrictions on the specific purification steps, and those skilled in the art can use common means in the art for purification.

[0027] In the present invention, the rotation speed of the mixing process is 30 - 50 rpm, and the mixing time is 40 - 100 h. In one or more embodiments of the present invention, this mixing process is carried out in a mixer. The longer mixing time ensures that the four reactants are fully mixed, which is beneficial to the subsequent reaction and is also beneficial to the preparation of high-quality LSGM single crystals with high homogeneity. The present invention does not impose special restrictions on the pressing process. For example, it can be pressed into a block by a hydraulic press or into a columnar rod by isostatic pressing, and those skilled in the art can choose according to actual needs.

[0028] In the present invention, the process of solid-phase sintering is specifically as follows: The pressed solid is sintered in an air atmosphere at 1100 - 1300 °C for 60 - 100 h.

[0029] In the present invention, the specific process of growing LSGM single crystals by the Czochralski method is as follows: The LSGM blank is placed in a crystal growth furnace. After vacuum pumping, a mixed atmosphere of oxygen, carbon dioxide and nitrogen is filled. The LSGM blank is heated and melted, and then necking, shoulder formation, equal-diameter growth and tailing are carried out. After the crystal grows to the required size, the crystal is lifted off and cooled to room temperature to obtain the LSGM single crystal.

[0030] In the present invention, the filling pressure of the mixed atmosphere of oxygen, carbon dioxide and nitrogen is 1 - 1.1 bar, and more preferably one atmosphere.

[0031] In the present invention, the LSGM blank is placed in an iridium crucible in the crystal growth furnace; the iridium crucible has good high-temperature resistance and thermal deformation resistance; however, during the growth of LSGM single crystals, the decomposed Ga may form an alloy with the iridium crucible and the mold, resulting in its loss. The present invention effectively overcomes the problems of volatilization and decomposition of Ga2O3 through the regulation of the atmosphere, and thus effectively slows down the loss of the iridium crucible.

[0032] In the present invention, the LSGM blank is placed in the crystal growth furnace and vacuum is pumped to a vacuum degree of (0.5 - 2)×10 -4 Pa.

[0033] The present invention does not impose special restrictions on the heating method for heating and melting the LSGM blank. The present invention preferably uses intermediate-frequency induction heating.

[0034] The present invention does not impose special restrictions on the specific necking, shoulder broadening, equal-diameter growth, and finishing stages, and the conventional Czochralski process in the art can be used. Preferably, in the necking process of the present invention, the LSGM seed crystal is introduced and necked under the condition of 1-3 °C higher than the melting point of the LSGM melt; the LSGM seed crystal is selected as the seed crystal with the <110> direction. After selecting the seed crystal with the <110> direction, the present invention further includes the steps of cutting, ultrasonic cleaning, and drying.

[0035] In the present invention, the pulling speeds in the necking, shoulder broadening, equal-diameter growth, and finishing stages are 0.8-1.2 mm / h, and the rotation speeds are 5-20 rpm.

[0036] In the present invention, after the crystal grows to the required size, the temperature is raised by 15-30 °C, held at a constant temperature for 20-40 min, and then the crystal is lifted off. In the present invention, the cooling rate in the process of cooling to room temperature is 10-30 °C / h.

[0037] The technical solution of the present invention will be further elaborated below in conjunction with specific embodiments. The present invention does not impose special restrictions on the sources of the reagents used in the following embodiments, and commercially available products well-known to those skilled in the art can be used. The purities of La2O3, SrCO3, Ga2O3, and MgO in the following embodiments are all 99.99%.

[0038] Example 1

[0039] This example provides a method for growing LSGM single crystals by the Czochralski method. Specifically, it includes the following steps:

[0040] (1) Selection and treatment of raw materials

[0041] La2O3, SrCO3, Ga2O3, and MgO are proportioned according to the mass ratio of 61.1:2.9:36.5:0.8, and then the above four raw materials are fully mixed for 72 hours and pressed into tablets. Then, the temperature is raised to 1200 °C at a heating rate of 50 °C / h and sintered at a high temperature for 72 h to obtain an LSGM blank for standby.

[0042] (2) Selection of seed crystal

[0043] The LSGM seed crystal is selected as the seed crystal with the <110> direction, cut, ultrasonically cleaned, and dried for standby.

[0044] (3) Growing LSGM single crystals by the Czochralski method

[0045] The LSGM blank in step (1) is loaded into an iridium crucible in the crystal growth furnace, and the crucible size is Φ60 mm × 60 mm; the inside of the crystal growth furnace is evacuated to 1×10 -4Pa, oxygen, carbon dioxide and nitrogen were filled to one atmosphere, and the volume fractions of oxygen, carbon dioxide and nitrogen were 1%, 70% and 29% respectively; the LSGM blank was heated and melted by medium-frequency induction heating.

[0046] The LSGM seed crystal was inserted and necked down at 2 °C above the melting point of the melt. When the diameter of the seed crystal was reduced to 2 mm, shoulder release was carried out. After equal-diameter growth, it entered the finishing stage; the pulling speeds in the necking-down, shoulder release, equal-diameter growth and finishing stages were: 1 mm / hour, and the rotation speed was: 10 revolutions per minute.

[0047] After the crystal grew to the required size, the temperature was raised by 20 °C and kept constant for 30 minutes, and the crystal was lifted out of the melt.

[0048] After lifting out the crystal, the temperature was decreased to room temperature at a rate of 15 °C / h, and the LSGM single crystal was obtained.

[0049] The LSGM single crystal prepared in this example is as Figure 1 shown.

[0050] The growth direction and single-crystallinity of the LSGM single crystal prepared in this example were tested by X-ray Laue diffraction method, and the results are as Figure 2 and Figure 3 shown. Figure 2 and Figure 3 are the diffraction spot patterns measured on the near (110) plane, and the test points are respectively at the upper and lower parts of the equal-diameter part of the crystal. From Figure 2 and Figure 3 , it can be seen that the distribution law of the diffraction spots is clear and obvious, and the crystal quality is good; the diffraction pattern is consistent with the theory, and the patterns of the upper and lower parts are the same, indicating that the directional growth of the crystal is achieved.

[0051] X-ray diffraction tests were respectively carried out on the prepared LSGM single crystal and the LSGM blank prepared by high-temperature sintering in step (1). The results are as Figure 4 shown. The black line is the standard PDF card of the LaGaO3 crystal, the 2nd line is the test result of the raw material after high-temperature sintering, and the 1st line is the test result of the prepared LSGM single crystal. From Figure 4 , it can be seen that there are no impurity peaks in the LSGM blank after high-temperature sintering and the prepared LSGM single crystal.

[0052] Example 2

[0053] This example provides a method for growing LSGM single crystal by the Czochralski method. The specific steps are as follows:

[0054] (1) Selection and treatment of raw materials

[0055] La2O3, SrCO3, Ga2O3 and MgO were proportioned according to the mass ratio of 61.9:2.8:37.1:0.9, and then the above four raw materials were fully mixed for 72 hours and pressed into tablets. Then, it was heated to 1200 °C at a heating rate of 50 °C / h for high-temperature sintering for 72 h to obtain the LSGM blank for standby.

[0056] (2) Selection of seed crystal

[0057] The LSGM seed crystal was selected as the seed crystal in the <110> direction, cut, ultrasonically cleaned, and dried for standby.

[0058] (3) Growing LSGM single crystal by the Czochralski method

[0059] The LSGM blank in step (1) was loaded into an iridium crucible in the crystal growth furnace, and the crucible size was Φ60 mm × 60 mm; the inside of the crystal growth furnace was evacuated to 1×10 -4 Pa, and oxygen, carbon dioxide and nitrogen were filled to one atmosphere, and the volume fractions of oxygen, carbon dioxide and nitrogen were 2%, 72% and 26% respectively; the LSGM blank was heated and melted by medium-frequency induction heating.

[0060] The LSGM seed crystal was inserted and necked down at 2 °C above the melting point of the melt. When the diameter of the seed crystal was reduced to 2 mm, shoulder release was carried out. After equal-diameter growth, it entered the finishing stage; the pulling speeds in the necking down, shoulder release, equal-diameter growth and finishing stages were: 2 mm / hour, and the rotation speed was: 10 revolutions per minute.

[0061] After the crystal grew to the required size, the temperature was raised by 20 °C and kept constant for 30 minutes, and the crystal was withdrawn from the melt.

[0062] After the crystal was withdrawn, it was cooled to room temperature at a rate of 15 °C / h, and the LSGM single crystal was obtained.

[0063] Example 3

[0064] This example provides a method for growing LSGM single crystal by the Czochralski method. The specific steps are as follows:

[0065] (1) Selection and treatment of raw materials

[0066] La2O3, SrCO3, Ga2O3 and MgO were proportioned according to the mass ratio of 60.9:3.1:36.9:0.8, and then the above four raw materials were fully mixed for 72 hours and pressed into tablets. Then, it was heated to 1200 °C at a heating rate of 50 °C / h for high-temperature sintering for 72 h to obtain the LSGM blank for standby.

[0067] (2) Selection of seed crystal

[0068] The LSGM seed crystal is selected as a <110>-oriented seed crystal, cut, ultrasonically cleaned, dried, and then reserved for use.

[0069] (3) Grow the LSGM single crystal by the Czochralski method

[0070] Load the LSGM blank from step (1) into an iridium crucible in the crystal growth furnace. The size of the crucible is Φ60mm×60mm; evacuate the crystal growth furnace to 1×10 -4 Pa, and fill it with oxygen, carbon dioxide, and nitrogen to one atmosphere. The volume fractions of oxygen, carbon dioxide, and nitrogen are 1%, 70%, and 29% respectively; heat and melt the LSGM blank by medium-frequency induction heating.

[0071] Lower the LSGM seed crystal and neck it down at 2°C above the melting point of the melt. When the diameter of the seed crystal is reduced to 2 mm, start shoulder broadening, and enter the finishing stage after equal-diameter growth; the pulling speeds in the necking-down, shoulder-broadening, equal-diameter growth, and finishing stages: 1 mm / hour, and the rotation speed: 13 revolutions per minute.

[0072] After the crystal grows to the required size, raise the temperature by 20°C, keep it at a constant temperature for 30 minutes, and lift the crystal out of the melt.

[0073] After lifting the crystal out of the melt, cool it down to room temperature at a rate of 15°C / h to obtain the LSGM single crystal.

[0074] Example 4

[0075] This example provides a method for growing LSGM single crystals by the Czochralski method. The specific steps are as follows:

[0076] (1) Selection and treatment of raw materials

[0077] Mix La2O3, SrCO3, Ga2O3, and MgO according to a mass ratio of 61.0:2.9:36.7:1.0, then fully mix the above four raw materials for 72 hours, and press them into tablets. Then, raise the temperature to 1200°C at a heating rate of 50°C / h and sinter at a high temperature for 72 h to obtain the LSGM blank, which is reserved for use.

[0078] (2) Selection of seed crystal

[0079] The LSGM seed crystal is selected as a <110>-oriented seed crystal, cut, ultrasonically cleaned, dried, and then reserved for use.

[0080] (3) Grow the LSGM single crystal by the Czochralski method

[0081] Load the LSGM blank from step (1) into an iridium crucible in the crystal growth furnace. The size of the crucible is Φ60mm×60mm; evacuate the crystal growth furnace to 1×10 -4Pa, oxygen, carbon dioxide and nitrogen are filled to one atmosphere, where the volume fractions of oxygen, carbon dioxide and nitrogen are 0.8%, 68% and 31.2% respectively; the LSGM blank is heated and melted by medium-frequency induction heating.

[0082] The LSGM seed crystal is inserted and necked down at 2 °C above the melting point of the melt. When the diameter of the seed crystal is reduced to 2 mm, shoulder broadening is carried out. After equal-diameter growth, it enters the finishing stage; the pulling speeds in the necking-down, shoulder-broadening, equal-diameter growth and finishing stages: 2 mm / hour, rotation speed: 10 revolutions per minute.

[0083] After the crystal grows to the required size, the temperature is raised by 20 °C and kept constant for 30 minutes, and the crystal is withdrawn from the melt.

[0084] After the crystal is withdrawn, it is cooled to room temperature at a rate of 15 °C / h, and the LSGM single crystal is obtained.

[0085] Example 5

[0086] This example provides a method for growing LSGM single crystals by the Czochralski method. The specific steps are as follows:

[0087] (1) Selection and treatment of raw materials

[0088] La2O3, SrCO3, Ga2O3 and MgO are proportioned according to a mass ratio of 61.0:3.0:36.8:0.9. Then the above four raw materials are fully mixed for 72 hours and pressed into tablets. After that, it is heated to 1200 °C at a heating rate of 50 °C / h and sintered at high temperature for 72 h to obtain the LSGM blank for standby.

[0089] (2) Selection of seed crystal

[0090] The LSGM seed crystal is a <110>-oriented seed crystal, which is cut, ultrasonically cleaned and dried for standby.

[0091] (3) Growing LSGM single crystals by the Czochralski method

[0092] The LSGM blank in step (1) is loaded into an iridium crucible in the crystal growth furnace, and the crucible size is Φ60 mm × 60 mm; the inside of the crystal growth furnace is evacuated to 1×10 -4 Pa, oxygen, carbon dioxide and nitrogen are filled to one atmosphere, where the volume fractions of oxygen, carbon dioxide and nitrogen are 1%, 70% and 29% respectively; the LSGM blank is heated and melted by medium-frequency induction heating.

[0093] Lower the LSGM seed crystal at a temperature 2°C higher than the melting point of the melt and neck it down. When the diameter of the seed crystal is reduced to 3 mm, start shoulder broadening, and after isodiametric growth, enter the finishing stage. The pulling speeds in the necking-down, shoulder-broadening, isodiametric growth, and finishing stages are: 2 mm / hour, and the rotation speed is: 10 revolutions per minute.

[0094] After the crystal grows to the required size, raise the temperature by 20°C, keep it at a constant temperature for 30 minutes, and lift the crystal out of the melt.

[0095] After lifting the crystal out, cool it to room temperature at a rate of 15°C / h to obtain the LSGM single crystal.

[0096] Comparative Example 1

[0097] Compared with Example 1, the difference in this comparative example is that in this comparative example, the volume fractions of oxygen, carbon dioxide, and nitrogen are 0.5%, 80%, and 19.5% respectively.

[0098] The X-ray Laue diffraction pattern of the LSGM single crystal prepared in this comparative example is as Figure 5 shown. It can be seen that the distribution pattern of the diffraction points is not as Figure 2 and Figure 3 clear as that in, indicating that the crystal quality prepared in this example is inferior to that of Example 1.

[0099] Comparative Example 2

[0100] Compared with Example 1, the difference in this comparative example is that in this comparative example, the atmosphere in the crystal growth furnace is oxygen and carbon dioxide, and the volume fractions of oxygen and carbon dioxide are 1% and 99% respectively.

[0101] The X-ray Laue diffraction pattern of the LSGM single crystal prepared in this comparative example is as Figure 6 shown. It can be seen that the distribution pattern of the diffraction points is not as Figure 2 and Figure 3 clear as that in, indicating that the crystal quality prepared in this example is inferior to that of Example 1.

[0102] Comparative Example 3

[0103] Compared with Example 1, the difference in this comparative example is that in this comparative example, the atmosphere in the crystal growth furnace is pure nitrogen.

[0104] The X-ray Laue diffraction pattern of the LSGM single crystal prepared in this comparative example is as Figure 7 shown. It can be seen that the distribution pattern of the diffraction points is not as Figure 2 and Figure 3 clear as that in, indicating that the crystal quality prepared in this example is inferior to that of Example 1.

[0105] Test Example

[0106] The conductivity of the LSGM single crystals prepared in Example 1 and Comparative Examples 1 to 3 was measured at different temperatures, and the results are as Figure 8 shown. It can be seen that the LSGM single crystal prepared in Example 1 has the most excellent electrical conductivity.

[0107] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for growing LSGM single crystals by the Czochralski method, characterized in that, It includes the following steps: Weigh La2O3, SrCO3, Ga2O3 and MgO according to the mass ratio of (60.5 - 62.0):(2.5 - 3.5):(36.2 - 38.2):(0.6 - 1.2), mix them and then press, and then carry out solid-phase sintering to obtain an LSGM blank; Then use the Czochralski method to grow LSGM single crystals; the atmosphere used in the growth process is a mixed atmosphere of oxygen, carbon dioxide and nitrogen, and the volume ratio of oxygen, carbon dioxide and nitrogen is (0.5 - 2):(65 - 75):(25 - 35).

2. The method according to claim 1, wherein The rotation speed of the mixing process is 30 - 50 rpm, and the mixing time is 40 - 100 h.

3. The method according to claim 1, characterized in that The specific process of the solid-phase sintering is as follows: place the pressed solid in an air atmosphere at 1100 - 1300 °C and sinter for 60 - 100 h.

4. The method according to claim 1, characterized in that The specific process of growing LSGM single crystals by the Czochralski method is as follows: place the LSGM blank in a crystal growth furnace, evacuate and then fill it with a mixed atmosphere of oxygen, carbon dioxide and nitrogen, heat and melt the LSGM blank, and then carry out necking, shoulder formation, equal-diameter growth and tailing. After the crystal grows to the required size, lift the crystal out and cool it to room temperature to obtain the LSGM single crystal.

5. The method according to claim 4, characterized in that, The charging pressure of the mixed atmosphere of oxygen, carbon dioxide and nitrogen is 1 - 1.1 bar.

6. The method according to claim 4, wherein Place the LSGM blank in an iridium crucible in a crystal growth furnace; evacuate to a vacuum degree of (0.5 - 2)×10 -4 Pa.

7. The method according to claim 4, wherein The pulling speed in the necking, shoulder formation, equal-diameter growth and tailing stages is (0.8 - 1.2) mm / h, and the rotation speed is 5 - 20 rpm.

8. The method according to claim 4, wherein After the crystal grows to the required size, raise the temperature by 15 - 30 °C, keep it at a constant temperature for 20 - 40 min, and then lift the crystal out.

9. The method according to claim 4, wherein The cooling rate in the process of cooling to room temperature is 10 - 30 °C / h.

10. The method according to claim 4, characterized in that, The necking process is to insert the LSGM seed crystal and carry out necking at a temperature 1 - 3 °C higher than the melting point of the LSGM melt; the LSGM seed crystal is a <110>-oriented seed crystal.

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