JPH042683A - Production of rutile single crystal - Google Patents

Abstract

PURPOSE:To enable the production of a large-sized rutile single crystal using a floating zone process by specifying the growing axis of the crystal. CONSTITUTION:In the production of a rutile single crystal by floating zone process, the direction of the growing axis of the crystal (the direction of arrow shown by solid line) is set to be [001] axis. The angle between the direction of the crystal growth axis and the [001] axis of the seed crystal 2 (the direction of arrow shown by dotted line) is preferably >=15 deg. (especially <=3 deg.). In the figure, 1 is supporting rod; 3 is raw material rod; 4 is floating material; 5 is crystal heating apparatus.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Industrial Application Field) The present invention relates to a method for producing rutile (T, 02) single crystal.

(Prior technology) Rutile single crystal is attracting attention as a high-precision optical component.
Various manufacturing methods have already been proposed.

For example, Japanese Patent Publication No. 2-5720 states that in order to obtain high-quality rutile crystals, it is necessary to crystallize only one type of crystal phase during solidification of the melt, and to do so, it is necessary to grow crystals from the melt. When doing so, it is proposed that the oxygen partial pressure in the atmosphere during crystal growth should be in the range of 3 x 10-2 atmospheres or less.

(Problem to be Solved by the Invention) When applying the above-mentioned conventional method, for example, using the floating zone method, the diameter of the rutile single crystal is 15o++n.
When growing plants up to about φ, there is almost no problem using only the method described as a conventional example.

However, if the diameter is 15IIIφ or more, the conventional method cannot produce crystals.

That is, in the floating zone method, floating bodies are formed by heating between the seed crystal and the raw material rod, but as the crystal diameter increases, the amount of floating bodies increases and the weight increases. This is because surface tension cannot hold the floating body and the floating body will fall down.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method for producing a rutile single crystal by which large-sized crystals can be obtained.

[Structure of the invention] (Means and effects for solving the problem) In order to achieve the above object, the present invention provides rutile (T102)
When manufacturing single crystals using the floating zone method,
The growth axis direction of the crystal was set to be the [001] axis.

Figure 1 is a detailed view of the vicinity of the floating body, showing a heated state in which a seed crystal 2 is attached to a holding rod 1 and a floating body 4 is placed between it and a raw material rod 3, and a part of the crystal is kept warm. It is covered by the device 5. Note that the dotted line arrow indicates the [001] axis direction of the seed, and the solid line arrow indicates the crystal growth direction. The angle between the direction of the crystal growth axis and the [001] axis of the seed crystal is 15
The range is preferably up to 3°, preferably 3° or less. On the other hand, if the angle is 30° or more, it is very difficult to hold the floating body.

Here, it is an experimental fact that when the [001] axis of the seed is used as the crystal growth axis, floating bodies are easily retained, but it is not clear why the floating bodies are easily retained.

However, among the crystal planes of rutile, the one that is easy to grow is (1
10) plane, that is, the axial direction where growth is slow, or the [110] axial direction. That is, [
001] In the case of axial growth, (110) facets appear anywhere on the solid-liquid interface. When grown in other axial directions, (110) facets are formed within the solid-liquid interface, and the solid-liquid interface becomes a floating body. This is thought to be because the shape is difficult to hold.

(Example) Examples will be described below.

Commercially available T,02 (99,98%) powder was heated at 11 On/c.
Rubber press molded into a rod shape with hydrostatic pressure of a, and heated to 1400″C.
Sintered in air. This is loaded as a raw material into a condensing floating method single crystal production device using a spheroidal mirror.
The axial direction of the seed crystal was set as the [001] axial direction. A crystal heat insulator was installed near the floating body. Then, CO2 was introduced into the crystallization chamber to control the oxygen partial pressure in the atmosphere.
Continue to flow at a flow rate of 21/min until the end of crystal growth, and perform crystal growth according to the conventional floating zone method.
Blue-black crystals were obtained. The growth conditions in this case are that the rotation speed of the raw material rod and the seed crystal is 25 times/min in opposite directions,
The crystal growth rate was 3 times/hour. 8 of the obtained crystals
As a result of annealing in air at 00°C for 48 hours, a slightly yellowish transparent crystal was obtained. A sample with planes parallel to the growth direction and the vertical direction was cut out from this crystal, optically polished, and then examined using a polarizing microscope. As a result, no distortion, bubbles, or subgrain composition were detected, and it was a high-quality rutile single crystal. It turned out that.

In addition, we prepared two seed crystals, one at 45° and the other at 90° with respect to the growth direction, and tried to grow the crystal by performing exactly the same operation as above, but it was not possible to hold the floating body. Crystals could not be grown because they would fall down.

[Effects of the Invention] As explained above, according to the present invention, when producing a rutile single crystal by the floating zone method, the crystal growth axis direction is the [001] axis, so that the crystal diameter is 15 nmφ. Larger rutile single crystals can now be obtained.

[Brief explanation of drawings]

FIG. 1 is a detailed view of the vicinity of the floating body during crystal growth. 1... Holding rod 2... Seed crystal 3...
Raw material rod 4...Floating body 5...Crystal heat retention device Patent applicant Norio Ishii, Patent attorney representing Chichibu Cement Co., Ltd.

Claims (2)

[Claims] (1) A method for producing a rutile single crystal using a floating zone method, characterized in that the crystal growth axis direction is the [001] axis. (2) The method for producing a rutile single crystal according to claim 1, characterized in that the angle formed between the direction of the crystal growth axis and the [001] axis of the seed crystal is within a range of up to 15°.