Method for growing large-size rare earth ion-doped garnet series crystals by wide-seed guiding mode

Abstract

The application discloses a method for growing large-size garnet series crystals by a wide-seed guide mode, which does not carry out a necking and a shoulder releasing process, reduces the risk of crystal cracking, improves a crystallization rate, shortens a growth time, and can stably grow large-size rare earth ion doped garnet series crystals with a size of more than six inches and high quality.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of crystal growth, and particularly relates to a method for growing large-size rare earth ion doped garnet series crystals by a wide-seed guided mode method. BACKGROUND

[0002] The growth principle of the guided mode method is to place a mold with a capillary gap in the middle of a crucible, and the solution rises to the upper surface of the mold by capillary action and forms a liquid film, and then the seed crystal is pulled down for growth. By adjusting the shape and size of the mold, single crystals of specific shape and size can be directly grown, which has the advantages of fast growth speed and low growth cost. In order to meet the strategic needs of rare earth ion doped garnet crystals in the fields of scintillation and laser, large-size high-quality crystals of more than six inches are needed, but there is a risk of cracking when growing large-size crystals by the guided mode method.

[0003] Narrow seeds are often used in the growth of crystals by the guided mode method. The width and thickness of the narrow seed are much smaller than the width and thickness of the top of the mold. During the growth of the crystal, necking and shoulder setting are needed to enter the stable growth stage. However, the shoulder crystal area increases exponentially with time during the shoulder setting stage, and the rapid increase in the shoulder area of the crystal leads to faster heat dissipation, resulting in thermal strain exceeding the critical strain value and causing the crystal to crack.

[0004] Using a wide seed for growth, the width of the wide seed is equal to the width of the mold, and the thickness is basically the same as the thickness of the mold. During the growth of the crystal, there is no necking and shoulder setting step, which solves the problem of excessive thermal stress during the shoulder setting process that causes the crystal to crack. The wide seed and the thermal field structure together establish a temperature field suitable for the growth of large-size crystals.

[0005] Patent document CN104962994A discloses a method for growing a specific size of rare earth doped gallium-containing garnet series crystal by the guided mode method, which can quickly grow a crystal of a specific size. However, it is explicitly stated that the length of the grown crystal is 4 inches, which is much smaller than the large-size crystal of more than 6 inches grown by the present application. At the same time, patent document CN104962994A explicitly states that the growth process requires seeding, necking, shoulder setting and constant diameter steps, and the materials of the crucible and the mold are iridium gold. SUMMARY

[0006] In view of the problems of difficulty in shoulder setting and easy cracking of large-size single crystals by the guided mode method in the prior art, the present application provides a process method for growing large-size garnet series crystals by a wide-seed guided mode method. This method does not perform necking and shoulder setting processes, which reduces the risk of cracking of the crystal, improves the crystallization rate and shortens the growth time, and can stably grow high-quality, large-size rare earth ion doped garnet series crystals.

[0007] The technical solution of the present application is as follows:

[0008] This invention provides a method for growing large-size rare-earth ion-doped garnet series crystals using a wide-seed crystal guiding method, wherein the molecular formula of the rare-earth ion-doped garnet series crystals is Re:A3B5O. 12 Re = Yb, Nd, Ce, A = Y, Lu and Y / Lu solid solutions, B = Al, Ga and Al / Ga solid solutions, characterized by including the following steps:

[0009] Step 1. Selection and processing of raw materials: According to the molecular formula Re:A3B5O 12 According to the stoichiometric ratio, the raw materials Re2O3, A2O3 and B2O3 are weighed and then mixed, pressed and sintered to obtain polycrystalline blocks;

[0010] Step 2. Crystal growth:

[0011] Step 2.1 Heat and melt the polycrystalline material block, and maintain it at superheat;

[0012] Step 2.2 Lower the wide seed crystal to bring it into contact with the mold;

[0013] The width W of the wide seed crystal S Thickness T S With the width W of the mold D Thickness T D Satisfying condition W S = W D And 80%T D T S T D ;

[0014] Step 2.3 After 10-30 minutes, the crystal is grown at a constant diameter at a pulling rate of 5-30 mm / h.

[0015] Step 2.4 After crystal growth is completed, the crystal is heated and then removed from the furnace, and then cooled to room temperature within 12-20 hours.

[0016] Step 2.5 After high-temperature annealing, heat the mixture in air to 1000-1300℃ and hold it at that temperature for 10-20 hours, then slowly cool it to room temperature.

[0017] The process of mixing, pressing, and burning materials in step 1 is specifically as follows:

[0018] Step 1.1 According to the molecular formula RE:A3B5O 12 Stoichiometry: Weigh out the raw materials Re2O3, A2O3, and B2O3.

[0019] After mixing the materials in the mixer for 20-40 hours, press them in the cold isostatic press for 3-6 hours.

[0020] Step 1.2 Place the pressed raw material into an alumina crucible, and place the alumina crucible into an annealing furnace for calcination at a temperature of 1000-1500℃ for 10-15 hours to obtain polycrystalline material blocks.

[0021] Preferably, in step (1), the materials are mixed in a mixer for 20-40 hours.

[0022] Preferably, in step (1), the powder is pressed in a cold isostatic press for 3-6 hours.

[0023] Preferably, in step (1), the specific process of calcination is to put the pressed raw material into an alumina crucible, and then place the alumina crucible into an annealing furnace for calcination at a temperature of 1000-1500℃ for 10-15 hours.

[0024] Preferably, in step (2), the entire growth process is carried out in a flowing atmosphere, which is an inert gas, such as argon.

[0025] Preferably, the mold in step (2) is a sheet-shaped molybdenum mold, which is placed in the center of the molybdenum crucible.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] 1) Large-size crystal growth requires large-size molds. During the growth process, the radial temperature gradient at the top of the mold is difficult to control, and an unsuitable temperature gradient on the upper surface of the mold increases the difficulty of crystal shoulder formation. Using a wide seed crystal with the same width as the mold eliminates the necking and shoulder formation steps, solving the problem of excessive thermal stress leading to crystal cracking during shoulder formation. Simultaneously, using a wide seed crystal allows for temperature field control, establishing a suitable temperature gradient for crystal growth, increasing the crystallization rate of single crystals larger than six inches, reducing growth costs, shortening the growth cycle, and producing high-quality crystals with better uniformity, free of cores and sidewalls, thus reducing material costs in processing.

[0028] 2) Compared to patent CN104962994A, the crystals grown in this invention are over 6 inches in length, while those grown in patent CN104962994A are only about 4 inches in length. The difficulty of crystal growth technology is directly proportional to the intended crystal growth size. Different crystal sizes require significantly different furnace, crucible, and mold sizes. This invention breaks through the technical barrier of growing large-size rare-earth ion-doped garnet crystals over 6 inches using the guided mold method. Furthermore, unlike patent CN104962994A, this invention uses a molybdenum crucible, while patent CN104962994A uses an iridium crucible. In terms of growth cost, this patent uses the more cost-effective molybdenum material, significantly reducing the cost of crystal growth. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the equipment structure for growing garnet crystals using the guided mold method in Embodiment 1 of the present invention;

[0030] In the diagram: 1. Seed crystal rod, 2. Seed crystal chuck, 3. Crystal, 4. Mold, 6. Crucible lid, 7. Crucible, 8. Auxiliary heater, 9. Main heater.

[0031] Figure 2 This is a schematic diagram of the mold in Embodiment 1 of the present invention.

[0032] Figure 3 This is a schematic diagram of the garnet single crystal state during the growth process of Embodiment 1 of the present invention.

[0033] Figure 4 This is a magnified view of a portion of the boundary between the wide seed crystal and the mold in Embodiment 1 of the present invention, wherein the width of the wide seed crystal is W. S Thickness T S The width of the top of the mold is W. D Thickness T D There exists a relation W S =W D And T D =T S .

[0034] Figure 5 The image shows the XRD pattern of the ytterbium-doped yttrium aluminum garnet single crystal obtained by the guided-mode method in Example 1 of this invention. Detailed Implementation

[0035] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several adjustments and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0036] Example 1

[0037] The method for growing large-size yttrium aluminum garnet single crystals using the wide-seed crystal guiding mode includes the following steps:

[0038] (1) According to the molecular formula (Yb) 0.3 Y 0.7 )3Al5O 12 According to the stoichiometric ratio, weigh raw materials Y2O3, Yb2O3 and Al2O3 with a purity of 5N, mix them in a mixer for 30 hours, press them in a cold isostatic press for 4 hours, put the raw materials into an annealing furnace and sinter at 1200℃ for 15 hours, and then take out the polycrystalline material block.

[0039] (2) Place the material block into the crucible 8 in the center of the furnace and use auxiliary heaters 9 and 10 to melt the polycrystalline material block. After the raw material is completely melted, keep it superheated. Use the seed crystal chuck 2 to fix the wide seed crystal 3 and control the seed crystal rod 1 to lower the wide seed crystal 3. The wide seed crystal 3 is the same width as the mold 6 and its thickness is the same as the thickness of the mold 6. After the seed crystal 3 contacts the mold 6, the liquid film 5 thickness is appropriate. After 15 minutes, the crystal is pulled into the constant diameter growth stage, and the pulling rate is 18 mm / h. After the crystal growth is completed, the temperature is raised and the crystal is removed. After 15 hours, the crystal is cooled to room temperature and then taken out of the furnace. The removed crystal is placed in a muffle furnace for high-temperature annealing to reduce thermal stress. The temperature is raised to 1100°C in the air atmosphere and kept constant for 16 hours. Then, the temperature is slowly lowered to room temperature.

[0040] Example 2

[0041] The method for growing large-size lutetium aluminum garnet single crystals using the wide-seed crystal guiding method includes the following steps:

[0042] (1) According to the molecular formula Lu3Al5O 12 According to the stoichiometric ratio, weigh raw materials Lu2O3 and Al2O3 with a purity of 5N, mix them in a mixer for 30 hours, press them in a cold isostatic press for 4 hours, put the raw materials into an annealing furnace and sinter at 1300℃ for 12 hours, and then take out the polycrystalline material block.

[0043] (2) Place the material block into the crucible 8 in the center of the furnace and use auxiliary heaters 9 and 10 to melt the polycrystalline material block. After the raw material is completely melted, keep it superheated. Use the seed crystal chuck 2 to fix the wide seed crystal 3 and control the seed crystal rod 1 to lower the wide seed crystal 3. The wide seed crystal 3 is the same width as the mold 6 and its thickness is 80% of the thickness of the mold 6. After the seed crystal 3 contacts the mold 6, the liquid film 5 is of appropriate thickness. After 18 minutes, the crystal is pulled into the constant diameter growth stage and the pulling rate is 23 mm / h. After the crystal growth is completed, the temperature is raised and the crystal is removed. After 17 hours, the crystal is cooled to room temperature and then removed from the furnace. The removed crystal is placed in a muffle furnace for high-temperature annealing to reduce thermal stress. The temperature is raised to 1200°C in the air atmosphere and kept constant for 18 hours. Then, the temperature is slowly lowered to room temperature.

[0044] Example 3

[0045] The method for growing large-size ytterbium-lutetium aluminum garnet single crystals using the wide-seed crystal guiding mode includes the following steps:

[0046] (1) According to the molecular formula (Yb) 0.2 Lu 0.8 )3Al5O 12 According to the stoichiometric ratio, weigh out raw materials Yb2O3, Lu2O3 and Al2O3 with a purity of 5N, mix them in a mixer for 30 hours, press them in a cold isostatic press for 4 hours, put the raw materials into an annealing furnace and sinter at 1300℃ for 14 hours, and then take out the polycrystalline material block.

[0047] (2) Place the material block into the crucible 8 in the center of the furnace and use auxiliary heaters 9 and 10 to melt the polycrystalline material block. After the raw material is completely melted, keep it superheated. Use the seed crystal chuck 2 to fix the wide seed crystal 3 and control the seed crystal rod 1 to lower the wide seed crystal 3. The wide seed crystal 3 is the same width as the mold 6 and its thickness is 90% of the thickness of the mold 6. After the seed crystal 3 contacts the mold 6, the liquid film 5 is of appropriate thickness. After 20 minutes, the crystal is pulled into the constant diameter growth stage and the pulling rate is 20 mm / h. After the crystal growth is completed, the temperature is raised and the crystal is removed. After 18 hours, the crystal is cooled to room temperature and then removed from the furnace. The removed crystal is placed in a muffle furnace for high-temperature annealing to reduce thermal stress. The temperature is raised to 1100°C in the air atmosphere and kept constant for 18 hours. Then, the temperature is slowly lowered to room temperature.

[0048] Example 4

[0049] The method for growing large-size Nd:YAG single crystals using the wide-seed crystal guiding mode includes the following steps:

[0050] (1) According to the molecular formula (Nd 0.1 Y 0.9 )3Al5O 12 According to the stoichiometric ratio, weigh out raw materials Nd2O3, Y2O3 and Al2O3 with a purity of 5N, mix them in a mixer for 30 hours, press them in a cold isostatic press for 4 hours, put the raw materials into an annealing furnace and sinter at 1300℃ for 15 hours, and then take out the polycrystalline material block.

[0051] (2) Place the material block into the crucible 8 in the center of the furnace, and use auxiliary heaters 9 and 10 to melt the polycrystalline material block. After the raw material is completely melted, keep it superheated. Use the seed crystal chuck 2 to fix the wide seed crystal 3, and control the seed crystal rod 1 to lower the wide seed crystal 3. The wide seed crystal 3 is the same width as the mold 6, and its thickness is the same as the thickness of the mold 6. After the seed crystal 3 contacts the mold 6, the liquid film 5 is of suitable thickness. After 20 minutes, the crystal is pulled into the constant diameter growth stage, and the pulling rate is 25 mm / h. After the crystal growth is completed, the temperature is raised and the crystal is removed. After 20 hours, the crystal is cooled to room temperature and then taken out of the furnace. The removed crystal is placed in a muffle furnace for high-temperature annealing to reduce thermal stress. The temperature is raised to 1300℃ in the air atmosphere and kept constant for 18 hours. Then, it is slowly cooled to room temperature.

[0052] Comparative Example 1

[0053] Narrow seed crystals were used, with the width and thickness of the seed crystal being much smaller than the width and thickness of the top of the mold. The pulling rates of the crystal during the necking and shoulder-forming stages were 20 mm / h and 30 mm / h, respectively. After exiting the furnace, cracks were found in the crystal. The crystal underwent necking and shoulder-forming, and the rapid increase in the shoulder area during the shoulder-forming stage led to increased thermal stress, causing the cracks.

[0054] Therefore, when growing large-size rare-earth ion-doped garnet series crystals, this invention requires a wide seed crystal with the same width as the mold, wherein the width of the wide seed crystal is W. S Thickness T SThe width of the top of the mold is W. D Thickness T D There exists a relation W S =W D And 80% .

Claims

1. A method for growing large-size rare-earth ion-doped garnet series crystals using a wide-seed crystal guiding method, wherein the molecular formula of the rare-earth ion-doped garnet series crystals is Re:A3B5O. 12 Re = Yb, Nd, Ce, A = Y, Lu and Y / Lu solid solutions, B = Al, Ga and Al / Ga solid solutions, characterized in that, Includes the following steps: Step 1. Selection and processing of raw materials: According to the molecular formula Re:A3B5O 12 According to the stoichiometric ratio, raw materials Re2O3, A2O3 and B2O3 are weighed and processed through mixing, pressing and calcining to obtain polycrystalline blocks; Step 2. Crystal growth: Step 2.1 Heat and melt the polycrystalline material block, and maintain it at superheat; Step 2.2 Lower the wide seed crystal to bring it into contact with the mold; The width W of the wide seed crystal S Thickness T S With the width W of the mold D Thickness T D Satisfying condition W S = W D and ; Step 2.3 After 10-30 minutes, the crystal is grown at a constant diameter at a pulling rate of 5-30 mm / h. Step 2.4 After crystal growth is completed, the crystal is heated and then removed from the furnace, and then cooled to room temperature within 12-20 hours. Step 2.5 After high-temperature annealing, heat the mixture in air to 1000-1300℃ and hold it at that temperature for 10-20 hours, then slowly cool it to room temperature.

2. The method for growing large-size rare-earth ion-doped garnet series crystals using the wide-seed crystal guiding mode according to claim 1, characterized in that, The process of mixing, pressing, and burning materials in step 1 is specifically as follows: Step 1.1 According to the molecular formula Re:A3B5O 12 Stoichiometry: Weigh out the raw materials Re2O3, A2O3, and B2O3. After mixing the materials in the mixer for 20-40 hours, press them in the cold isostatic press for 3-6 hours. Step 1.2 Place the pressed raw material into an alumina crucible, and place the alumina crucible into an annealing furnace for calcination at a temperature of 1000-1500℃ for 10-15 hours to obtain polycrystalline material blocks.

3. The method for growing large-size rare-earth ion-doped garnet series crystals using the wide-seed crystal guiding method according to claim 1, characterized in that, The crystal growth process in step 2 is carried out in a flowing atmosphere, which is an inert gas.

4. The method for growing large-size rare-earth ion-doped garnet series crystals using the wide-seed crystal guiding mode according to claim 1, characterized in that, The mold is a sheet-shaped molybdenum mold. In step 2, during the furnace loading process before crystal growth, a molybdenum crucible containing raw materials is placed in the center of the furnace, a molybdenum mold is placed in the center of the molybdenum crucible, and a molybdenum crucible cover is placed on the molybdenum crucible.

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