JPH06135800A - Production of single crystal - Google Patents

Abstract

PURPOSE:To produce a YAG single crystal excellent in crystallinity and having a long straight shell part by controlling an after heater effect while reducing the deterioration of the refractory and without lowering the stabilizing effect in the growth conditions and making the temp. gradient in the pulling-up direction gentle and linear. CONSTITUTION:In the production of an Yttrium-aluminum-garnet single crystal by the Czochralski method, the single crystal is grown by using a growth device provided with a metallic disk 15 arranged at the upper end of a heating crucible 11 filled with a molten material 14, capable of intercepting the IR radiation, with the whole or a part at the center made into a truncated cone having the apex in the vertical direction of the molten material and having an opening of enough size to pass the grown crystal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to yttrium-aluminum-garnet (hereinafter YAG) containing active ions used for materials for solid-state lasers by the Czochralski method.
The present invention relates to a method for producing a single crystal, which relates to a method for producing a single crystal having good crystallinity and a long straight body.

[0002]

2. Description of the Related Art Among YAG single crystals containing active ions, particularly yttrium aluminum containing neodymium
Garnet (hereinafter referred to as Nd ⁺³ : Y ₃ Al ₅ O ₁₂ ) single crystal is the most industrially useful solid-state laser material at present, and is used in various laser oscillators. Normal X: Y ₃ Al ₅
A YAG single crystal represented by a chemical formula of O ₁₂ (X is Nd ^+3, etc.) is manufactured by a Czochralski method of a high frequency heating method using a crucible made of iridium (hereinafter referred to as Ir) metal or the like. However, since the melting point is extremely high at about 1970 ° C., aluminum oxide (Al ₂ O ₃ ) or zirconium oxide (Zr ₂ O ₃ ) having a high melting point and high purity is provided around the crucible filled with the raw material melt and above the melt surface. It is necessary to keep it warm by covering it with a refractory or powder. The composition of these refractory materials is an important growth condition in the growth of YAG single crystals.

When used in the vicinity of a high temperature melt and crucible, these refractories cause deterioration such as cracking. Refractory placed close to the top of the melt has a temperature environment close to the maximum operating temperature limit of the refractory material, and deterioration easily proceeds,
In particular, the heat retention is severely deteriorated. This deterioration of the refractory causes changes in single crystal growth conditions such as temperature gradient, which is an obstacle to growth. In order to prevent this, in the case of conventional YAG single crystal growth, in general, a metal disc made of Ir metal or the like having a circular hole in the central portion is provided between the melt and the refractory or in place of the refractory. To place. This metal disc has little heat retention but does not have deformation deterioration and plays a role of stably blocking infrared radiation from the melt throughout the growing process, reducing the deterioration of refractory and stabilizing the growing conditions. ing.

However, as the growth progresses and the melt surface descends, and the crucible wall area on the melt surface increases, the adverse effect of the metal disk arrangement appears. That is, generally, an increase in the area of the crucible wall that does not conduct heat to the melt results in a so-called after-heater effect that reduces the temperature gradient above the melt and makes crystal growth difficult. Particularly in the case of YAG single crystal growth, since the refractory material is originally grown with a relatively large temperature gradient and the heat resistance of the refractory material is lost as the growth progresses, the high frequency power must be gradually increased to maintain the melt temperature. , This effect is likely to appear at the final stage of growth. When a metal disk is placed, the radiation is suppressed and the metal disk itself is also induction heated, so the heat dissipation to the upper side is relatively small in the vicinity of the melt, and the after-heater effect tends to appear more and more. Become. As a result, there is a problem that the crystallization rate of the melt is reduced, the length of the straight body portion is reduced, or the crystallinity is deteriorated. In addition, since the temperature gradient drastically changes at the position of the metal disk, there is a problem that the single crystal is cracked during the growth.

[0005]

The object of the present invention is to solve the above problems and control the after-heater effect without impairing the effects of reducing the deterioration of refractory and stabilizing the growth conditions by disposing the metal shielding plate. In addition, the present invention provides a method for producing a YAG single crystal having good crystallinity and a long straight body by making the temperature gradient in the pulling direction a gentle linear gradient.

[0006]

In order to solve the above-mentioned problems, the present invention has a truncated cone shape having an opening at the center and the center of the disk having an apex in the vertical direction of the melt. This is a method for producing a single crystal by a device in which a certain metal disk is placed above a crucible.

That is, the present invention is a method for producing an yttrium-aluminum-garnet single crystal using the Czochralski method, which is capable of blocking infrared radiation disposed at the upper end of a heating crucible filled with a raw material melt. A disk made of metal whose whole or part of the center has a truncated cone shape having apexes in the vertical direction of the raw material melt, and which has an opening of a size that allows the grown crystal to pass through. In the method for producing a single crystal, which is characterized by growing using a growing apparatus provided, and in the method for producing a single crystal described above, an even number of a plurality of radial directions at a portion which becomes a frustum-shaped portion of a metal disk. A metal disk having a notch and having a frustum-shaped portion alternately bent in the vertical direction of the raw material melt so that the apex of the frustum-shaped portion comes in the vertical direction of the raw material melt was provided. Raise using a raising device It is a manufacturing method of a single crystal characterized by.

[0008]

When a conventional disc-shaped metal shielding plate is arranged on the upper part of the crucible, it exhibits a temperature gradient as shown in FIG. 4 (a). The area where the metal disk 16 is open has good heat conduction upward, and the area covered by the metal disk 16 also blocks infrared radiation from the melt 14 surface and the crucible 11 wall, and goes outside. Heat dissipation is reduced. This makes it possible to increase the relative temperature difference between the center of the melt surface and the vicinity of the crucible wall, which contributes to the increase of natural convection. However, especially when the disk is a flat surface, the temperature change in the vertical direction near the metal disk is large, and therefore, when the grown crystal passes through this region, cracks easily occur due to heat shock. However, as in the present invention, the metal disk 15 having a structure in which the upper and lower surfaces of the metal shield plate are projected like a frustum.
Then, by making the vicinity of the opening of this metal disk into a truncated cone shape having an apex in the vertical direction, as shown in FIG. 4B, a portion having a sharp temperature gradient is eliminated and a gentle temperature gradient is obtained. It is possible to prevent cracking due to heat shock.

[0009]

EXAMPLE Next, as an example, the method of the present invention was used to
A case where a single crystal of neodymium-doped yttrium-aluminum-garnet represented by d ⁺³ : Y ₃ Al ₅ O ₁₂ is manufactured will be described. FIG. 1 is an explanatory diagram illustrating the configuration of a growing device used in the method of the present invention. FIG. 2 shows a disk made of Ir metal used in the method of the present invention, FIG. 2 (a) is a top view, and FIG. 2 (b) is a side sectional view. As shown in FIGS. 1 and 2, the apparatus for growing a single crystal used in the embodiment of the present invention is provided with an atmosphere gas inlet 2 and an atmosphere gas outlet 3 at the top and bottom of a furnace body 1, and an alumina refractory material 6 An Ir metal crucible 11 is arranged in a state where the periphery thereof is covered with the zirconia powder 9, and a melt 14 of a single crystal raw material exists inside the crucible 11. The grown crystal 13 grown at the tip of the seed crystal fixed to the crystal rotary pull-up shaft is in contact with the upper surface of the melt. A work coil 10 for heating is provided between the alumina refractory 6 and the furnace body,
Further, an alumina refractory material and a zirconia refractory material are arranged above the alumina refractory material 6. Further, the metal disk (Ir metal disk 15 in this embodiment) which is a feature of the present invention is Ir.
At the upper end of the metal crucible 11, the apex of the truncated cone of the disk 15 is arranged in the vertical direction of the melt.

Next, high-purity yttrium oxide, aluminum oxide and neodymium oxide powders were weighed and mixed in a required ratio. 9000 g of the raw material was melted into an Ir metal crucible 11 having a diameter of 150 mm, a depth of 150 mm and a thickness of 2 mm. The Ir metal disk 15 has an outer diameter of 170 mm × inner diameter of 80 mm × thickness of 1 mm and has a disk shape as shown in FIG. The weight of crystal pulled up is about 1500 g. In consideration of the melt surface descent distance and the length between the upper end of the Ir metal crucible 11 and the surface of the melt 14, the heights of the Ir metal disk 15 from the upper and lower ends to the upper and lower ends are 3 cm each. About 2 kg of a pellet-shaped raw material having the same composition as the previously prepared melt was added into the Ir metal crucible, and the raw material was heated and melted to about 1950 ° C. The seed crystal was brought into contact with the melt surface from above by a usual method using the above-described growing apparatus shown in FIG. 1, and the seed crystal was gradually pulled up by the crystal rotary pulling shaft 4 to grow the crystal. Diameter 6
Nd ⁺³ : YAG with 0 mm and length of 200 mm and good crystallinity
A single crystal was obtained. Next, in the above-mentioned embodiment, as shown in FIG.
Is divided by a plurality of diametrical cuts (8 places in this example), and the pieces are alternately folded back and forth to form a comb-shaped frustum shape, which is then changed to the metal shielding disk 15. As a result, the yield was slightly lower than that of the previous example, but the production of the shielding metal disk 15 was simplified, and the yield was improved as compared with the case where the conventional disk 16 was used.

[0011]

As described above, according to the method of the present invention, the arrangement of the metal disks does not deteriorate the refractory and does not impair the effect of stabilizing the growth conditions.
The after-heater effect is suppressed, and it becomes possible to manufacture an economical YAG single crystal having good crystallinity and a long straight body.

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating a configuration of a growing device used in a method for manufacturing a single crystal according to an embodiment of the present invention.

FIG. 2 is the I used in the method of the embodiment of the invention shown in FIG.
r shows the shape of a metal disk, FIG. 2 (a) is a top view, FIG.
(B) is a front sectional view.

FIG. 3 shows the shape of an Ir metal disk used in the method of another embodiment of the present invention, FIG. 3 (a) is a top view and FIG. 3 (b).
Is a front sectional view.

FIG. 4 shows the distribution of isotherms in the vertical and horizontal directions of the melt surface of the crucible and the temperature distribution in the vertical direction of the central part when a metal disk is arranged. FIG. FIG. 4 (b) shows the case where the Ir metal disk according to the present invention is arranged, when the disk making is arranged.

[Explanation of symbols]

1 Furnace Body 2 Atmospheric Gas Inlet 3 Atmospheric Gas Exhaust 4 Crystal Rotating Pulling Shaft 5 Alumina Refractory (Cylindrical) 6 Alumina Refractory (Crucible) 7 Zirconia Refractory (Cylindrical) 8 Zirconia Refractory (Disc) 9 Zirconia powder 10 Work coil 11 Crucible 12 Seed crystal 13 Growing crystal 14 Melt 15 Disk 16 (Conventional) disk 17 Frustum-shaped portion 18 Curve (dashed line) 19 showing the vertical temperature distribution in the center of the crucible 19 Isotherm

Claims (2)

[Claims] 1. A method for producing a yttrium-aluminum-garnet single crystal using the Czochralski method, which is a metal disk arranged at an upper end of a heating crucible filled with a raw material melt and capable of blocking infrared radiation, The whole or a part of the shape of the center is a frustum shape having an apex in the up-down direction of the raw material melt, and a growing device equipped with a metal disk having an opening of a size through which a grown crystal can pass. A method for producing a single crystal, which comprises growing the single crystal. 2. The method for producing a single crystal according to claim 1, wherein the frustum-shaped portion of the metal disk has an even number of radial notches, and the frustum-shaped portion is used as a raw material. Alternating in the vertical direction of the melt, a single crystal characterized by growing using a growing device equipped with a metal disk configured so that the apex of the frustum-shaped portion comes in the vertical direction of the raw material melt Manufacturing method.