JPH0822794B2 - Crystal growth method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a crystal growth method under microgravity, and relates to a high temperature material used for a gas turbine or the like, an energy conversion material used for solar thermal power generation, or a semiconductor material. The present invention relates to a method for growing various crystals such as, for example, under microgravity.

[Conventional technology]

The fourth aspect of the conventional crystal growth method under microgravity
This will be described with reference to FIGS.

FIG. 4 is an explanatory view of a mode in which a Ni alloy is manufactured under microgravity (hereinafter abbreviated as μG) by a so-called Britzmann method using a temperature gradient furnace. In FIG. 4, 1 is an ampoule, 2 is a cartridge, 3 is an electric furnace, and 4 is a cooler. FIG. 5 is an enlarged view of a part of FIG. 4 and is an explanatory view around the ampoule 1. The Ni alloy sample is first solidified into a cylindrical shape by a sintering method, and as shown in FIG. It is filled in the ampoule 1. At this time, the diameter di of the sample 5 should be as close as possible to the inner diameter of the ampoule 1. As shown in FIG. 4, the ampoule 1 is made of a quartz material, and is further loaded into a ceramic cartridge 2 which is made of ceramics.

The cartridge 2 and the ampoule 1 are mounted on the electric furnace 3, and all the samples are once brought into a molten state by heating. After that, the ampoule 1 is gradually moved to the right at a constant speed. Since there is the cooler 4 on the right side, the sample starts to solidify from the right end of the ampoule 1. This situation is shown in FIG. Since this operation is performed under μG, the melted sample is almost concentric with ampoule 1,
The diameter dm is smaller than di due to volume contraction. When this solidifies and becomes like 7 on the right side, the volume increases again and the diameter ds
And the diameter is almost the same as the initial diameter di, and ampoule 1
It almost adheres to the inner wall.

As shown in FIG. 6, the molten sample 6 is a liquid column having a free liquid surface, and is heated on the left side and cooled on the right side, so that there is a temperature difference between the left and the right. For this reason, there is a difference in the surface tension on the left and right, and so-called surface tension convection occurs in which the liquid flows from the left to the right on the surface and from the right to the left inside.

Manufacturing under μG means manufacturing in outer space, or manufacturing in weightless flight by an aircraft, a rocket or the like.

[Problems to be Solved by the Invention]

In the conventional crystal growth method under μG, due to the above-mentioned surface tension convection, there is a problem that the crystal structure is disturbed at the solidification interface, resulting in many defects and high quality cannot be obtained.

In view of the above-mentioned state of the art, the present invention aims to provide a crystal growth method capable of preventing or almost preventing surface tension convection under μG to obtain a high quality crystal.

[Means for solving the problem]

The present invention is as follows: (1) A solid initial sample is filled in a circular tube-shaped ampoule, heated and once melted, and then re-solidified by cooling to obtain a desired material crystal under microgravity. In the method to be carried out, a crystal growth method characterized in that a plurality of ring-shaped spacers are intermittently provided on the outer circumference of the initial sample, and (2) a solid initial sample is filled in a circular tube-shaped ampoule and heated. Then, after melting once, re-solidify by cooling to obtain the required material crystals in a method under microgravity, in which a microparticle material that is not melted at the operating temperature is filled between the initial sample and the ampoule. The crystal growth method is characterized by

[Action]

In the first invention, the free surface of the sample melt is divided by the spacers, so that the individual free surfaces become smaller, the temperature difference between both ends on each free surface becomes smaller, and the surface tension convection decreases. Therefore, solidification proceeds in a state where the influence of convection is small, and high quality crystals can be obtained.

In the second aspect of the present invention, since a group of fine particles adheres to the free surface when the sample is melted, surface tension convection is less likely to occur, and solidification proceeds without or with little convection, resulting in a good quality crystal To be

[Embodiment 1] One embodiment of the first invention will be described with reference to FIG. In FIG. 1, the same parts as those in FIG. 4 are designated by the same reference numerals. FIG. 1 (a) shows the state of the initial sample.

The spacer 8 is formed by molding a non-melting material such as quartz or graphite into a small two-divided ring shape, and embedding this in a groove provided intermittently on the circumference of the surface of the initial sample 5 to form an outer diameter of the spacer 8. And the outer diameter of the initial sample 5 are adjusted to be almost equal. The state in which the initial sample 5 thus adjusted is loaded in the ampoule 1 is shown in FIG.

FIG. 1 (b) shows a state during crystal production. Ampoule 1
The entire sample is heated, and the initial sample 5 becomes a molten sample 6, but a partially solidified sample 7 is being formed at the cooling end (right side). At this time, the initial sample 5
Becomes a columnar liquid column, and because of microgravity, the whole is separated from the inner surface of the ampoule 1 to form a free surface. However, since this has a ring as shown in FIG. 1 (b), S ₁ , S ₂ ,
It becomes a free surface divided like. Free surface S ₁
For example, the free surface S ₁ is a continuous liquid surface only between the spacers 8-1 and 8-2. Spacer 8-
Since the difference between the temperature of the liquid in 1 and the temperature of the spacer 8-2 is relatively small (compared to the case of FIG. 6), the surface tension convection generated based on this is also small, and FIG. 1 (b) As shown by the streamline in the arrow, the convection remains small in the vicinity of the surface and cannot affect the solidification interface. Therefore, the crystals obtained by solidification are of good quality.

Next, another example of the embodiment of the first invention will be described with reference to FIG. FIG. 2 shows the state during crystal production. Also in FIG. 2, the same parts as those in FIG. 4 are designated by the same reference numerals.

A plurality of ring-shaped spacers 8 are mounted on the outer circumference of the cylindrical initial sample 5. While at the time of initial sample 5 molten liquid had close contact with the spacer 8 inside, initially such that increasing further space Atsuta part space from the connexion between the spacer, S _1, S ₂ · ·
Form a free surface like. As a result, the same effect as the previous example can be obtained.

As yet another aspect, although not shown in place of the spacer in FIG. 2, even if the outer periphery of the initial sample is coated with a cylindrical body having a large number of through holes in the vertical direction, the same effect as that of the spacer described above is obtained. Can play.

[Embodiment 2] An embodiment of the second invention will be described with reference to FIG. FIG. 3 shows a state during crystal production. In FIG. 3, those parts which are the same as those corresponding parts in FIG. 4 are designated by the same reference numerals.

The fine particle filler 9 is a ceramic material such as Al ₂ O ₃ or Y ₂ O ₃ , and is made of a material that does not melt at the operating temperature of this Ni alloy production. The diameter of the fine particles is in the range of about 0.2 to 100 μm, and these are filled around the initial sample 5 at an appropriate filling rate. Although the gap between the sample 6 and the ampoule 1 widens in the molten sample 6, the fine particle filler 9 adheres to the liquid surface, so that there is an interfacial tension between the liquid and the solid particle surface. Then the surface tension will disappear. Since the interfacial tension between the solid and the liquid hardly changes due to the temperature difference, there is no difference between the left and right of the molten sample 6, and accordingly the liquid cannot move.

The above describes the case where the Ni alloy is manufactured as a high-temperature material as an example, but in addition to this, it is also applicable to the manufacturing of semiconductors used as energy conversion materials, or electronic materials, superconducting materials, etc. Although described, the zone melting method can be similarly applied in addition to this.

〔The invention's effect〕

The present invention reduces or eliminates surface tension convection, resulting in high quality crystals.

[Brief description of drawings]

1 and 2 are explanatory views of one embodiment of the present invention, FIG. 3 is an explanatory view of another embodiment of the present invention, and FIGS. 4 to 6 are explanatory views of a conventional method.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsumi Ueya 7-14 Wadamiyadori, Hyogo-ku, Kobe, Hyogo Prefecture Nishiryo Engineering Co., Ltd.

Claims (2)

[Claims] 1. A method in which a solid initial sample is filled in a circular tube-shaped ampoule, which is heated and once melted, and then resolidified by cooling to obtain a desired material crystal under microgravity. 2. A crystal growth method, wherein a plurality of ring-shaped spacers are intermittently provided on the outer periphery of the initial sample. 2. A method in which a solid initial sample is filled in a circular tube-shaped ampoule, which is heated and once melted, and then re-solidified by cooling to obtain a desired material crystal under microgravity. 2. A crystal growth method characterized in that a fine particle material which is infusible at an operating temperature is filled between the initial sample and the ampoule.