JPH0316987A - Ampul for crystal growth by bridgman technique - Google Patents

Abstract

PURPOSE:To accomplish inhibition of Marangoni convection development by forming asperities on the inner surface of an ampul to finely divide the free level in melt solidification into sections. CONSTITUTION:Asperities 5 with recesses 4 several mu to several tens mu in size are formed on the inner surface of an ampul 1 for crystal growth by Bridfman technique. The ampul 1 is then encapsulated with a solid sample having such a volume as to be capable of almost fully filling even to the recesses 4 due to the expansion through its melting, followed by heating to effect filling almost of the recesses 4 with the resulting melt 2. The ampul 1 is then cooled at its one end to afford the melt 2 with temperature gradient, a solidified region 3 is gradually formed from the cooling side, and the free level F formed on the melt 2 is finely divided through the recesses 4 to effect inhibition of Marangoni convection development, thus making the interface P of a crystal flat.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an ampoule for lengthening Bridgman crystals.

[Conventional technology 1] Due to the development of space exploration in recent years, various research efforts have been conducted to create materials with uniform crystal structures that are difficult or impossible to obtain on Earth in the microgravity of space. As a container for obtaining a material with a uniform structure, a Bridgman crystal growth ampoule l as shown in FIG. 3 has been proposed.

Bridgman Crystal Growth Ampoule L is made of an insulating material such as carbon, quartz, or poron nitride and has a substantially long cylindrical shape, and is a material that aims to obtain a uniform crystal structure when used. After the sample is sealed in the ampoule i in a solidified state, the whole is first heated in a heating furnace capable of providing a temperature gradient to melt the sample sealed inside, and then the sample sealed inside is melted by the heating furnace. In order to give the sample melt 2 a temperature gradient, it is gradually cooled from one end side in the lengthwise direction of the ampoule l, thereby solidifying it and growing a solidified portion 3.

[Problems to be Solved by the Invention] However, in the conventional ampoule 1 described above, as shown in FIG. Free liquid level F
is formed, which causes the problem of Marangoni convection M caused by surface tension.

In other words, when a sample is melted and then cooled and solidified from one end, the surface tension is small on the high temperature liquid surface (melt liquid 2 side) and large on the low temperature liquid surface (solidified part 3 side). , the liquid molecules are pulled toward the lower temperature side and move, and as the molecules on the surface move, the molecules inside are gradually dragged along and begin to move, creating a flow throughout.

When such Marangoni convection M occurs, temperature unevenness occurs on the solidification surface, and the crystal interface P becomes curved as shown in Figures 3 and 4, and the distribution of components varies depending on the location.
Problems arise in the non-uniformity of the crystal structure, such as crystal orientation, and in addition, in the product obtained by the conventional ampoule 1, only the central part can be used as a relatively uniform crystal structure. Yield becomes very poor.

The present invention was made by focusing on the above-mentioned conventional problems.
An object of the present invention is to provide an ampoule for Bridgman crystal growth that makes it possible to suppress the occurrence of Marangoni convection by finely dividing the free liquid surface of the melt during solidification within the ampoule. There is.

[Means for Solving the Problems] The present invention provides a Bridgman crystal growth method characterized in that fine irregularities are formed on the inner surface of the ampoule to finely divide the free surface formed in the melt. It comes in ampoules.

[Function] When the melted sample fills up to the grooves on the uneven surface and is solidified by cooling, the free liquid surface is divided into small pieces due to the melt filling the grooves. This suppresses the occurrence of Marangoni convection.

[Implementation example] Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 show one embodiment of the present invention, and the third
, 4 and 4 indicate the same parts.

In the present invention, the inner surface of the Bridgman crystal growth ampoule 1 is formed with an uneven surface 5 having grooves 4 of several microns to several tens of microns. At this time, the pitch of the grooves 4, the volume of the grooves 4, etc. can be set arbitrarily.

On the other hand, the internal volume of the ampoule 1 described above is
Be sure to calculate this in advance, including the following.

When using the ampoule {having the uneven surface 5 on its inner surface, first prepare a solid sample having a volume that can almost completely fill the groove 4 by expansion due to melting, and then insert the solid sample into the ampoule l. After enclosing the solid sample in a container, it is heated in a heating furnace to melt the solid sample.

At this time, the melt 2, which is the solid sample, fills most of the recess 4.

Subsequently, when the heating device 1 cools the ampoule 1 from one end side in order to give a temperature gradient to the melt 2, a solidification part 3 is gradually formed from the cooling side.

At this time, since the melt 2 has entered the grooves 4, the free liquid surface F5 formed in the melt 2 is finely divided by each groove 4, which prevents the occurrence of Marangoni convection. It will be blocked.

When the Marangoni convection is prevented from occurring in this manner, the interface P of the crystal becomes a plane, the distribution of components becomes uniform, and the crystal structure becomes uniform.

Furthermore, the uniformity of the crystal structure significantly improves the product yield.

Note that the Bridgman crystal growth ampoule of the present invention is not limited to the above-described embodiments, and instead of forming an uneven surface with grooves, a mesh screen may be arranged along the inner surface of the ampoule. It goes without saying that similar uneven surfaces may be formed by using the same method, and that various other changes can be made without departing from the gist of the present invention.

[Effects of the Invention] As explained above, according to the Bridgman crystal lengthening ampoule of the present invention, it is possible to solidify while suppressing the occurrence of Marangoni convection 6, so that the distribution of components is made uniform and the crystal structure is improved. This makes it possible to achieve an excellent effect of producing high-quality products with a high yield.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an embodiment of the present invention, FIG. 2 is an enlarged detailed view of the part ■ in FIG. 1, FIG. 3 is a cross-sectional view of an example of a conventional Bridgman crystal growth ampoule, and FIG. The figure is an enlarged detailed view of the part ■ in FIG. 3. 1 is a Bridgman crystal growth ampoule, 2 is a melt, 3 is a solidified portion, 4 is a groove, 5 is an uneven surface, and F is a free liquid level.

Claims (1)

[Claims] 1) A Bridgman crystal growth ampoule characterized by having a fine uneven surface formed on the inner surface of the ampoule to finely divide the free liquid surface formed in the melt.