JP4312341B2 - Method for producing plate of oxide single crystal, seed crystal used therefor and seed crystal holder - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a plate of oxide single crystal, a seed crystal used for the method, and a seed crystal holder.
[0002]
[Prior art]
Lithium potassium niobate single crystals and lithium potassium niobate-lithium potassium tantalate solid solution single crystals are attracting attention as single crystals for blue light second harmonic generation (SHG) devices for semiconductor lasers. This can be generated up to the 390 nm ultraviolet region, so by using such short wavelength light, a wide range of applications such as optical disk memory, medical use, photochemistry use, and various optical measurement applications are possible. is there. In addition, since the single crystal has a large electro-optic effect, it can be applied to an optical storage element or the like using the photorefractive effect.
[0003]
However, for example, in the second harmonic generation element application, if the composition of the single crystal varies even slightly, the wavelength of the second harmonic oscillated from the element varies. For this reason, the specification of the composition range required for the single crystal is strict, and it is necessary to suppress the composition variation within a narrow range. However, since there are many constituent components such as three or four components, it is generally very difficult to grow a single crystal at a high speed while controlling the ratio of each constituent component to be constant.
[0004]
In addition, in optical applications, particularly second harmonic generation applications, it is necessary to propagate laser light having a short wavelength of, for example, around 400 nm with a power density as high as possible in a single crystal. In addition, it is necessary to minimize optical damage at this time. In this way, it is essential to suppress optical damage, but for this purpose, the crystallinity of the single crystal needs to be good.
[0005]
In addition, lithium niobate and lithium potassium niobate can be substituted between cations, thereby generating a solid solution in which cations are dissolved. For this reason, in order to grow a single crystal having a specific composition, it is necessary to control the composition of the melt. From such a background, a double crucible method and a method for growing crystals while supplying raw materials have been studied, centering on the CZ method and the TSSG method. For example, Kitamura et al. Tried to grow a stoichiometric lithium niobate single crystal by combining an automatic powder feeder with the double crucible CZ method (J. Crystal Growth, 116 (1992), p. 327). ). However, with these methods, it is difficult to increase the crystal growth rate.
[0006]
As a method for growing the single crystal as described above at a constant composition ratio, the present applicant has proposed a μ pulling-down method in, for example, Japanese Patent Application Laid-Open No. 8-319191. In this method, for example, a raw material made of lithium potassium niobate is accommodated in a platinum crucible, melted, and the melt is gradually and continuously drawn downward from an opening of a nozzle attached to the bottom of the crucible. In addition, the μ pulling method can grow a single crystal at a higher speed than the CZ method or the TSSG method. Moreover, the composition of the melt and the single crystal to be grown can be controlled by continuously growing the single crystal while adding the raw material for growing the single crystal to the raw material melting crucible.
[0007]
[Problems to be solved by the invention]
However, there is still a limit to continuously growing a high-quality single crystal plate (single crystal plate-like body) at a high speed by using the μ reduction technique.
[0008]
The inventor first contacts the melt with the oxide single crystal fiber (seed crystal), pulls down the melt, and adjusts the temperature of the melt and the ambient temperature of the fiber. Tried to form. Then, the width of the shoulder portion is gradually increased, and when the width of the shoulder portion reaches a desired value, the temperature of the nozzle portion or the like is slightly increased, and the increase in the width of the shoulder portion is stopped. As a result, a plate-like body having a constant width is continuously pulled out from the end of the shoulder. According to this method, cracks hardly propagate from the vicinity of the joint interface between the seed crystal and the plate-like body.
[0009]
However, in this growing method, it takes a long time until the width of the shoulder reaches a certain value, and the shoulder is basically wasted. For this reason, mass production of the plate-like body is difficult and the production cost is increased.
[0010]
On the other hand, the present inventor considers growing a plate-like body having substantially the same cross-sectional dimension (width) as the seed crystal by bringing the seed crystal into contact with the melt and pulling down the seed crystal. did. In this case, the above-described problems associated with shoulder growth can be avoided. However, in this case, high-precision matching is required between the lattice constant of the seed crystal and the lattice constant of the plate-like body. That is, it is necessary to control the difference between the lattice constant of the seed crystal and the lattice constant of the plate-like body to usually 0.1% or less in the direction of each crystal axis. The lattice constant of the plate-like body can be controlled to some extent by controlling the ratio of each component in the raw material powder charged into the crucible and the electric power supplied to the crucible, nozzle part, and after heater. However, in the actual manufacturing process, the lattice constant of the plate-like body may fluctuate or fluctuate due to some unknown cause, which causes cracks to develop from the vicinity of the joint interface between the seed crystal and the plate-like body, In some cases, it was a defective product.
[0011]
An object of the present invention is to enable continuous and stable growth of a plate having good crystallinity when growing a plate of oxide single crystal by a micro-pulling down method. That is.
[0012]
[Means for Solving the Problems]
As a result of various searches for a method for growing a plate of oxide single crystal by the micro-pulling down method, the present inventor formed a plurality of connecting portions between the seed crystal and the melt, and lowered the melt by lowering the seed crystal. By pulling down the crucible from the crucible opening, separate shoulders are formed on the contact parts, and these shoulders are grown and connected to each other to form a plate-like body, thereby producing high quality crystallinity. It has been found that a plate-like body having can be produced continuously.
[0013]
Here, by generating a plurality of contact portions between the seed crystal and the melt, the contact area between the various crystals and the melt is reduced, unlike the case where a plate-like seed crystal is used. Therefore, the tolerance for the difference between the lattice constants of the crystal axes of the various crystals and the crystal constants of the crystal axes of the shoulders at each contact portion is the tolerance when the plate-like seed crystal is used. Bigger than. For this reason, it is hard to generate | occur | produce a crack in a plate-shaped object, and the yield at the time of manufacture increases.
[0014]
In the present invention, each shoulder portion gradually grows and is connected to an adjacent shoulder portion to generate a plate-like body. Here, the time required for each shoulder to contact and connect to the adjacent shoulder is much shorter than when a fiber-like seed crystal is used, and the length of the shoulder is also much shorter.
[0015]
The difference (lattice mismatch) between each lattice constant of each crystal axis of the seed crystal and each crystal axis of each shoulder is preferably 1.0% or less, and 0.5% or less. More preferably.
[0016]
At this time, each lattice constant of each crystal axis of each shoulder can be adjusted by controlling the ratio of each component in the crucible. For example, in lithium potassium niobate, the lattice constant of each crystal axis in the grown plate can be changed by slightly changing the relative ratio of niobium, lithium and potassium in the crucible.
[0017]
The lattice constant is measured using an X-ray diffractometer (Philips MRD diffractometer).
[0018]
Preferably, the seed crystal is an integral seed crystal cut from a bulk single crystal material. In order to generate a plate having good crystallinity, it is necessary to strictly match the crystal orientation of the seed crystal at each connection portion. When the seed crystal is an integral seed crystal cut from the bulk single crystal material, the crystal orientation of the seed crystal at each connection portion is uniquely determined by the crystal orientation of the bulk single crystal material. . In the present invention, the seed crystals can be separated from each other. However, in this case, it is necessary to perform a complicated procedure to strictly align the crystal orientation of the seed crystal in each connection portion.
[0019]
Particularly preferably, the seed crystal includes a plurality of protrusions for forming a plurality of connecting portions and a connecting portion for connecting the plurality of protrusions, and grooves are formed between adjacent protrusions. Yes.
[0020]
The present inventor also paid attention to the form of the holding portion of the seed crystal. That is, in the micro pulling-down method, the seed crystal is usually fixed so as not to move by adhering the fiber seed crystal to the holder. However, especially when using a wide seed crystal, it is better to grasp and grasp the seed crystal using the elasticity of a metal plate or the like than to bond and fix the seed crystal so that it does not move. It was discovered that cracks are unlikely to occur in the body.
[0021]
Therefore, according to the present invention, the oxide single crystal raw material is melted in the crucible, the seed crystal is brought into contact with the melt, and the seed crystal is pulled down to lower the melt from the opening of the crucible. A seed crystal holder for use in generating a crystal, comprising: at least a pair of gripping arms for gripping the seed crystal; and an elastic plate for biasing the gripping arm while gripping the seed crystal. The present invention relates to a seed crystal holder.
[0022]
The elastic plate is not particularly limited, but a metal plate is preferable in order to give just the right urging force, and in particular, a heat resistant alloy such as Inconel that has little deterioration in characteristics even when used at high temperatures is preferable. The gripping arm is preferably made of a material having a required rigidity and low elasticity, and more preferably made of ceramics such as alumina.
[0023]
FIG. 1 is a schematic cross-sectional view showing a manufacturing apparatus for growing a single crystal, FIG. 2 is a front view showing a seed crystal 15, and FIG. 3 is a front view showing a holder 16 for the seed crystal 15. . 4 to 6 are schematic views showing a process for growing the plate-like body 32. FIG.
[0024]
A crucible 7 is installed inside the furnace body. An upper furnace 1 is installed so as to surround the crucible 7 and its upper space 5, and a heater 2 is embedded in the upper furnace 1. A nozzle portion 13 extends downward from the lower end portion of the crucible 7. The nozzle portion 13 includes an elongated connecting pipe portion 13a and an elongated plate-like extended portion 13b at the lower end portion of the connecting tube portion 13a. However, FIG. 1 shows a cross section of the plate-like extended portion 13b. The shapes of the connecting pipe portion 13a and the plate-like extended portion 13b can be variously changed. Also, the combination of both can be freely changed. An elongated opening 13c is formed at the lower end of the plate-like extended portion 13b, and the vicinity of the opening 13c is a single crystal growing portion 27. The lower furnace 3 is installed so as to surround the nozzle portion 13 and the surrounding space 6, and the heater 4 is embedded in the lower furnace 3. Both the crucible 7 and the nozzle portion 13 are formed of a corrosion-resistant conductive material.
[0025]
One electrode of the power source 10 is connected to the position A of the crucible 7 by the electric wire 9, and the other electrode of the power source 10 is connected to the lower end B of the crucible 7. One electrode of the power source 10 is connected to the position C of the connecting pipe portion 13a by the electric wire 9, and the other electrode is connected to the lower end D of the plate-like extended portion 13b. These energization mechanisms are separated from each other, and are configured so that the voltage can be controlled independently.
[0026]
An after heater 12 is provided in the space 6 at an interval so as to surround the nozzle portion 13. In the crucible 7, the intake pipe 11 extends upward, and an intake port 22 is provided at the upper end of the intake pipe 11. The intake 22 protrudes slightly from the bottom of the melt 8.
[0027]
The upper furnace 1, the lower furnace 3, and the after-heater 12 are heated to appropriately determine the temperature distribution in the spaces 5 and 6, supply the raw material of the melt into the crucible 7, and supply power to the crucible 7 and the nozzle unit 13. To generate heat. In this state, in the single crystal growing portion 27, the melt slightly protrudes from the opening 13c.
[0028]
The seed crystal 15 includes a plurality of, for example, seven projections 15b and a flat plate-like connecting portion 15a that connects the bottoms of the projections 15b. The seed crystal 15 is an integral product cut out from a bulk single crystal raw material. A groove 15c is formed between adjacent protrusions 15b.
[0029]
In the present embodiment, the bottom surface 15f of the seed crystal 15 is not bonded to the holder, and the pair of side surfaces 15e of the seed crystal 15 is held by the holder 16 of FIG. The holder 16 has a slit 18 formed at each tip of each gripping arm 17, and each side surface 15 e of the seed crystal 15 is accommodated and held in each slit 18. Each gripping arm 17 is attached to the elastic plate 21 by a bolt 20 and a nut 19. The elastic plate 21 is attached to the holding bar 23 by a bolt 25, and the holding bar 23 is bonded to the holding bar 24. The interval G between the slits 18 is preferably 1-2 mm smaller than the interval (width) E between the pair of side surfaces 15e of the seed crystal 15, thereby urging each gripping arm 17 inward. To do.
[0030]
In this state, as shown in FIG. 4, the seed crystal 15 is moved upward, and each contact surface 15d of the seed crystal 15 is brought into contact with the melt protruding from the opening 13c. Reference numeral 28 denotes a contact portion. A uniform solid phase liquid phase interface (meniscus) is formed between the upper end portion of the seed crystal 15 and the melt 30 drawn downward from the nozzle portion 13. Next, as shown in FIG. 5, the seed crystal 15 is pulled down. As a result, each shoulder 31 is continuously formed on the upper side of each projection 15b, and is drawn downward. Reference numeral 35 denotes a connection portion between each shoulder portion and the seed crystal.
[0031]
The width of each shoulder 31 gradually increases from the seed crystal 15 toward the crucible 7. The angle of each shoulder 31 is determined by the type and composition of the crystal. When the shoulder portions 31 come into contact with each other, the temperature of the nozzle portion is slightly increased to stop the expansion of the width of each shoulder portion 31. At this point, the shoulders 31 come into contact with each other and are connected as shown in FIG. Reference numeral 33 denotes a joining portion of adjacent shoulder portions. Thereafter, as shown in FIG. 6, the plate-like body 32 having a constant width is continuously drawn out.
[0032]
In the seed crystal, the width W of the groove is preferably 2 mm or more, which can prevent the melt from flowing into the groove due to capillary action. Moreover, it is preferable to make the width W of a groove | channel into 5 mm or less, and, thereby, the crack in the junction part 33 of each shoulder part 31 can be suppressed much more favorably.
[0033]
In the seed crystal, the depth F of the groove is preferably 3 mm or more, which can effectively prevent the melt from being filled in the groove. The depth F of the groove is preferably 10 mm or less, whereby the mechanical strength of each protrusion 15b can be increased and the waste of the seed crystal can be prevented.
[0034]
The oxide single crystal is not particularly limited. For example, lithium potassium niobate (KLN), lithium potassium niobate-lithium potassium tantalate solid solution (KLTN: [K ₃ Li _2-x (Ta _y Nb _1-y ) _{5+ x} O _{15 + 2x} ]), lithium niobate, lithium tantalate, lithium niobate-lithium tantalate solid solution, Ba _1-X Sr _X Nb ₂ O ₆ , Mn—Zn ferrite, Nd, Er, Yb Examples thereof include YVO ₄ substituted with yttrium aluminum garnet, YAG, Nd, Er, and Yb.
[0035]
【Example】
Example 1
A single crystal production apparatus as shown in FIG. 1 was used to produce a lithium potassium niobate single crystal plate according to the present invention. Specifically, the temperature in the entire furnace was controlled by the upper furnace 1 and the lower furnace 3. The temperature gradient in the vicinity of the single crystal growing portion 27 can be controlled by supplying power to the nozzle portion 13 and generating heat from the after heater 12. As a mechanism for lowering the single crystal plate, a mechanism for lowering the single crystal plate was mounted while uniformly controlling the pulling speed within a range of 2 to 100 mm / hour in the vertical direction.
[0036]
A seed crystal 15 made of lithium potassium niobate was used. The width E of the seed crystal 15 is 32 mm, the width of each protrusion 15 b is 2 mm, the width W of the groove 15 c is 3 mm, the number of protrusions is 7, the height of the connecting portion 15 a is 5 mm, and the depth of the groove F was 5 mm. The total seed crystal thickness was 1 mm. Regarding the lattice constant of the seed crystal, the length of the a-axis was 12.59 angstroms, and the length of the c-axis was 4.00 angstroms. The ratio of potassium, lithium and niobium was 30:16:54 in terms of mol ratio. The half width of the X-ray rocking curve of the 0 0 4 reflection of the seed crystal was 60 seconds (measuring device: MRD diffractometer manufactured by Philips).
[0037]
The seed crystal 15 was held by the holder 16 of FIG. 3, and the holding bar was connected to the pulling mechanism. However, the elastic plate 21 was formed of an Inconel plate having a thickness of 0.1 mm. Each gripping arm 17 was formed of an alumina plate.
[0038]
Potassium carbonate, lithium carbonate and niobium pentoxide were mixed at a molar ratio of 30:25:45 to produce a raw material powder. This raw material powder was supplied into a crucible 7 made of platinum, and the crucible 7 was set at a predetermined position. The temperature of the space 5 in the upper furnace 1 was adjusted to a range of 1100 to 1200 ° C., and the raw material in the crucible 7 was melted. The temperature of the space 6 in the lower furnace 3 was uniformly controlled to 500 to 1000 ° C. Predetermined electric power was supplied to the crucible 7, the nozzle part 13, and the after heater 12, and single crystal growth was performed. At this time, the temperature of the single crystal growing part could be 980 ° C. to 1150 ° C., and the temperature gradient in the single crystal growing part could be controlled to 10 to 150 ° C./mm.
[0039]
The crucible 7 had an oval planar shape, a major axis of 50 mm, a minor axis of 10 mm, and a height of 10 mm. The length of the connecting pipe part was 5 mm. The cross-sectional dimension of the plate-like extended portion 13b was 1 mm × 50 mm. The size of the opening 13c was 1 mm long × 50 mm wide. In this state, the seed crystal 15 was pulled down at a speed of 10 mm / hour.
[0040]
As a result, the lower part of the bandage gradually crystallized, and each shoulder 31 was generated. When the lowering was continued further, the area of the shoulder 31 gradually increased and eventually joined each other. At this time, by adjusting the temperature of the nozzle portion 13, the expansion of the width of each shoulder portion 31 was stopped, and the plate-like body 32 was generated. The width of the plate-like body 32 was 35 mm. It took 20 minutes for the plate 32 to form.
[0041]
While supplying the same amount of raw material as the crystallized melt into the crucible 7, the crystal growth is continued, and when the total length of the shoulder 31 and the plate 32 reaches 60 mm, the plate is inserted into the nozzle portion. Disconnected from 13 and cooled. When the lattice constant of the shoulder portion of the collected plate was measured, the a-axis length was 12.57 angstroms and the c-axis length was 4.03 angstroms. The ratio of potassium, lithium and niobium was 30:18:52 in terms of mol ratio. The difference in lattice constant (lattice mismatch) between the shoulder and the seed crystal was 0.2% on the a-axis and 0.8% on the c-axis. Cracks at the joint between the seed crystal 15 and the shoulder 31 did not occur. The full width at half maximum of the X-ray rocking curve at the shoulder 31 was 50 seconds.
[0042]
(Example 2)
The same results as in Example 1 were obtained for the lithium potassium niobate-lithium potassium tantalate solid solution single crystal plate.
[0043]
(Example 3)
A plate of lithium niobate was grown in the same manner as in Example 1. However, seed crystal 15 made of lithium niobate was used. The seed crystal was obtained by cutting out a lithium niobate single crystal having a coincident melt composition grown by the Czochralski method. The pulling orientation of the seed crystal was parallel to the X axis, and the growth plane orientation was parallel to the Z axis. Regarding the lattice constant of the seed crystal, the length of the a-axis was 5.150 angstroms, and the length of the c-axis was 13.864 angstroms. The ratio of lithium to niobium was 48.6: 51.4 in terms of mol ratio. 0 0 of seed crystal
The half width of the 12-reflection X-ray rocking curve was 12 seconds.
[0044]
Lithium carbonate and niobium pentoxide were mixed at a molar ratio of 58:42 to produce a raw material powder. This raw material powder was supplied into a crucible 7 made of platinum, and the crucible 7 was set at a predetermined position. The temperature of the space 5 of the upper furnace 1 was adjusted to a range of 1200 to 1300 ° C., and the raw material in the crucible 7 was melted. The temperature of the space 6 in the lower furnace 3 was uniformly controlled to 500-1000 ° C. Predetermined electric power was supplied to the crucible 7, the nozzle part 13, and the after heater 12, and single crystal growth was performed. At this time, the temperature of the single crystal growing part could be set to 1200 to 1250 ° C., and the temperature gradient in the single crystal growing part could be controlled to 10 to 150 ° C./mm. The pulling rate of the seed crystal was 30 mm / hour. The volume of the crystallized lithium niobate was measured every unit time, this volume was converted to a weight, and a raw material powder of lithium niobate having a weight equal to the converted weight was supplied into the crucible. However, the lithium niobate powder supplied later in this way is prepared such that the molar ratio of lithium to niobium is 50:50, unlike the raw material powder first melted. When the shoulder portions 31 joined, the temperature of the nozzle portion 13 was adjusted, and a plate-like body 32 having a width of 50 mm was grown.
[0045]
The growth was continued while supplying the raw material powder of lithium niobate until the total length of the shoulder portion 31 and the plate-like body 32 reached 60 mm. Next, the plate-like body was separated from the seed crystal 15 and cooled.
[0046]
When the composition of the shoulder portion of the recovered plate-like body was analyzed by the inductively coupled plasma method, the ratio of lithium to niobium was 50:50 in molar ratio, which was consistent with the stoichiometric composition. When the lattice constant of the plate-like body was measured, the a-axis length was 5.148 angstroms and the c-axis length was 13.857 angstroms. The difference in lattice constant (lattice mismatch) between the shoulder and the seed crystal was 0.04% on the a-axis and 0.05% on the c-axis. Cracks did not occur at the joint between the seed crystal and the shoulder. The half width of the X-ray rocking curve at the shoulder was 12 seconds.
[0047]
(Example 4)
A plate-like body was grown in the same manner as in Example 3. However, the seed crystal was processed so that the pulling orientation of the seed crystal was parallel to the Z axis and the orientation of the growth surface was parallel to the X axis. The seed crystal, each a-axis length at the shoulder, c-axis length, and the half-value width of the X-ray rocking curve were all the same as in Example 3. In addition, no crack was generated at the joint surface between the shoulder and the seed crystal.
[0048]
(Comparative Example 1)
A plate-like body 32 was grown in the same manner as in Example 1. However, a fiber-shaped seed crystal having an end face of 1 mm × 1 mm and a length of 5 mm was used as a seed crystal. As a result, it took 4 hours for the width of the shoulder 32 to reach 35 mm. The shoulder length reached 40 mm.
[0049]
【The invention's effect】
As described above, according to the present invention, when a plate-like body of oxide single crystal is grown by the micro-pulling down method, a plate-like body having good crystallinity can be continuously and stably improved. I can cultivate well.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing a growing apparatus that can be used in an embodiment of the present invention.
FIG. 2 is a front view showing a seed crystal 15;
FIG. 3 is a front view showing a seed crystal holder 16;
FIG. 4 is a schematic diagram showing one step of a plate-like body growing process, in which a contact surface 15d of each protrusion 15b is in contact with a melt 30;
FIG. 5 is a schematic diagram showing one step of a plate-like body growing process, in which shoulder portions 31 are pulled out above the respective protrusions 15b.
FIG. 6 is a schematic diagram showing one step of the plate-like body growing process, and the shoulder portions 31 above the protrusions 15b merge to form an integrated plate-like body 32. FIG.
[Explanation of symbols]
7 Crucible 8 Melt in crucible 13 Nozzle part 13b Plate-like extension part of nozzle part 13c Opening of plate-like extension part 13b 15 Seed crystal 15a Connection part 15b Protrusion 15c Groove 15d Protrusion contact surface 16 Holder 17 Holding arm 18 Slit DESCRIPTION OF SYMBOLS 21 Elastic plate 28 Contact part of seed crystal and melt 30 Melt 31 which protrudes from nozzle part of crucible 31 Shoulder part 32 Plate body 33 Merge part 35 Connection part of seed crystal and shoulder part E Width of seed crystal 15 F Depth of groove 15c G Gap spacing of gripping arm W Width of groove 15c

Claims (6)

A method for producing a plate of oxide single crystal,
The raw material of the oxide single crystal is melted in a crucible, and a seed crystal is brought into contact with the melt. At this time, a plurality of contact portions between the seed crystal and the melt are formed, and the seed crystal is pulled down. The melt is pulled down from the opening of the crucible to form separate shoulders on the contact portion, and the shoulders are grown and connected to each other to form the plate-like body. The manufacturing method of the plate-shaped body of an oxide single crystal characterized by the above-mentioned.   2. The method for producing a plate-like body according to claim 1, wherein the seed crystal is an integral seed crystal cut out from a bulk single crystal material.   The seed crystal includes a plurality of protrusions for forming the plurality of contact portions and a connecting portion for connecting the plurality of protrusions, and a groove is formed between the adjacent protrusions. The method for producing a plate-like body according to claim 1 or 2, characterized in that   The width | variety of the said groove | channel is 2 mm or more and 5 mm or less, The manufacturing method of the plate-shaped object of Claim 3 characterized by the above-mentioned. A raw material of the oxide single crystal is melted in a crucible, a seed crystal is brought into contact with the melt, and the seed crystal is pulled down to lower the melt from the opening of the crucible. A seed crystal for generating a body,
A plurality of protrusions to be brought into contact with the melt; and a connecting portion for connecting the plurality of protrusions, and a groove is formed between the adjacent protrusions, and the width of the groove is 2 mm or more and 5 mm. characterized in that it is less, the seed crystal for use in the manufacture of the plate-like body of the oxide single crystal.   The seed crystal according to claim 5, wherein the seed crystal is an integral seed crystal cut from a bulk single crystal material.

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