JPH09227295A - Ferrite single crystal manufacturing method - Google Patents

Abstract

(57) Abstract: When manufacturing a ferrite single crystal by a double crucible method, the unmelted raw material in the upper crucible 1 is suppressed, composition segregation is small, and a ferrite single crystal having good crystallinity is stable. Up to the right length. SOLUTION: The spout pipe 4 of the upper crucible 1 is provided in the vertical direction, and the inner diameter of the spout pipe 4 is restricted to 4 to 12 mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the production of ferrite single crystals, and more particularly to improvements in the method for producing ferrite single crystals by the Bridgman method.

[0002]

2. Description of the Related Art Conventionally, the Bridgman method, which is easy to operate and simple in equipment, has been widely used as a method for producing a ferrite single crystal. The Bridgman method uses a temperature gradient to promote crystallization, and one end of a molten sample melted in a platinum crucible is cooled to crystallize and gradually grows. It is a thing. According to such a Bridgman method, not only ferrite single crystals but also large single crystals of metals, salts, etc. can be produced, and industrially, optical materials, magnetic materials, semiconductors, various alloys, etc. It is used to produce single crystals.

However, in the above-mentioned Bridgman method, when the width of the melting zone (melt zone) in the crucible becomes large, a large amount of platinum constituting the crucible is melted into the melted sample, and is grown into the grown single crystal. Many will be mixed. Moreover, composition segregation occurs in which the composition of crystals generated at the front end and the rear end of the crucible is different.

Therefore, a double crucible method has been proposed which uses an upper crucible for melting raw materials and a lower crucible for growing a single crystal.

In this double crucible system, an upper crucible having a spout pipe at the lower end and a lower crucible are arranged in two steps, and a rod-shaped raw material suspended from above is arranged in the upper crucible. Load it. Then, the upper crucible and the lower crucible are passed through a furnace having a constant temperature gradient. At this time, the raw materials are successively melted from the lower end in the upper crucible, and the melted molten sample is supplied to the lower crucible so that the width of the melt zone in the lower crucible becomes constant. A single crystal is grown from the supplied molten sample.

Here, in such a double crucible system,
The molten sample melted in the upper crucible flows down from the spout pipe provided at the lower end of the upper crucible and is supplied to the lower crucible. As shown in FIG. 6, this spout pipe is provided obliquely with respect to the vertical direction so that the spout 11 a of the pipe approaches the inner wall of the lower crucible 12, and the molten sample from the spout 11 a is placed in the lower crucible 12. It is designed to flow down the inner wall of the. This is for the purpose of preventing the melted surface of the melt zone from being disturbed by dropping the melted sample directly into the melt zone.

[0007]

However, in such a double crucible system, not all of the raw materials loaded in the upper crucible are supplied to the lower crucible, but the inner wall of the upper crucible and the inner wall of the spout pipe. In addition, some unmelted residue remains. In particular, recently, in order to improve the quality of the grown single crystal ferrite, the supply rate of the molten sample to the lower crucible has been slowed down, and such unmelted residue is more likely to occur. Here, if the raw material remains unmelted in the upper crucible, the following inconvenience occurs.

First, if the raw materials remain unmelted in the upper crucible,
Therefore, the total amount of the molten sample supplied to the lower crucible becomes smaller. Therefore, the single crystal ingot becomes shorter than a predetermined length, which leads to a decrease in the yield of the single crystal ingot.

Further, the crucible is usually continuously used a plurality of times. At this time, if the raw material remains unmelted in the upper crucible, it is necessary to reduce the amount of the raw material to be loaded by the amount of unmelted material after the first use and after the second use, which makes the operation complicated. .

Further, since the unmelted raw material and the newly loaded raw material are melted differently, the timing at which the molten sample is supplied from the upper crucible to the lower crucible is deviated, which causes the melt zone width to vary and the single crystal ingot. The quality is deteriorated.

Therefore, the present invention has been proposed in view of such conventional circumstances, and a ferrite single crystal which suppresses unmelted raw materials in the upper crucible, has a small composition segregation, and has good crystallinity is obtained. It is an object of the present invention to provide a method for producing a ferrite single crystal that can be grown with a stable length.

[0012]

In order to achieve the above object, the inventors of the present invention have conducted extensive studies, and as a result, in the unmelted portion of the ferrite raw material in the upper crucible, the spout pipe provided in the upper crucible is It was found that the unmelted ferrite raw material can be suppressed by providing this spout pipe in the vertical direction. Further, until now, when the spout pipe was provided in the vertical direction, it has been a problem that the molten raw material drops directly into the melt zone, causing disturbance in the melt zone, but the feed rate of the ferrite raw material is slow. Under the present circumstances, it was found that such turbulence of the melt zone hardly occurs, and no problem occurs even if the spout pipe is provided in the vertical direction.

The present invention has been completed on the basis of such knowledge, and an upper crucible having a spout pipe at the lower end and a lower crucible are used. The crucible and the lower crucible are passed through a furnace having a temperature gradient, and the ferrite raw material melted in the upper crucible is supplied to the lower crucible through the spout pipe, while growing the ferrite single crystal in the lower crucible. Is provided in the vertical direction, and the inner diameter of this spout pipe is 4 mm to 12 mm.

When the spout pipe is vertically provided in the upper crucible and the inner diameter thereof is regulated as described above, the amount of the ferrite raw material left unmelted in the upper crucible is suppressed, the composition segregation is small, and the ferrite single crystal having good crystallinity is small. The crystal grows with a stable length.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the method for producing a ferrite single crystal of the present invention will be described below.

In order to manufacture a ferrite single crystal, as shown in FIG. 1, a platinum crucible in which an upper crucible 1 and a lower crucible 2 are arranged in upper and lower two stages is prepared.

The upper crucible 1 is for melting a raw material and supplying the molten raw material to the lower crucible 2. The upper crucible 1 has a cylindrical portion into which the rod-shaped raw material 3 suspended from above is inserted, and a spire portion having a steeple shape by gradually reducing the diameter below the cylindrical portion, The spout pipe 4 extends vertically from the apex of the steeple. The inner diameter of the spout pipe 4 is in the range of 4 mm to 12 mm. Upper crucible 1
The molten sample melted in (1) flows down from this spout pipe 4 and is supplied to the lower crucible 2.

On the other hand, the lower crucible 2 is for crystal growth of the supplied molten raw material. The lower crucible 2 is composed of a cylindrical portion and a pointed portion which is pointed by gradually reducing the diameter below the cylindrical portion.

In order to grow a ferrite single crystal by using the above two crucibles, the ferrite raw material 3
Is hung from above and inserted into the upper crucible 1. Then, the upper crucible 1 and the lower crucible 2 on which the raw material 3 is set are set in the furnace with a certain distance therebetween.

Next, the temperature of the furnace is increased to gradually increase the temperature from the upper side to the lower side as shown in FIG. 1, and when a certain temperature is exceeded, a temperature gradient is gradually decreased. . In the temperature gradient, point X is the melting start temperature of the raw material and point Y is the crystallizing temperature of the raw material. Then, the upper crucible 1 and the lower crucible 2 are gradually lowered in this furnace.

First, in the process of lowering each crucible,
As shown in FIG. 2, when the lower end of the raw material 3 reaches point X in the furnace where the melting start temperature of the raw material 3 is reached, the raw material 3
Melts and flows down from the spout pipe 4 of the upper crucible 1 to the lower crucible 2, and a melt zone 5 in a molten state is formed in the lower crucible 2.

Subsequently, the crucibles 1 and 2 are further lowered, and when the lower end of the lower crucible 2 reaches the point Y where the furnace temperature is the crystallization temperature, as shown in FIG. Is cooled to a temperature below the crystallizing temperature, and a single crystal starts to crystallize.

Further, when the crucibles 1 and 2 are gradually lowered, as shown in FIG. 4, the raw material 3 melted from the upper crucible 1 is successively supplied to the lower crucible 2 and from the lower end of the melt zone 5. Single crystals 6 are sequentially crystallized.

Then, when the single crystal has grown into the shape of the ingot 6, the movement of each of the crucibles is stopped in the state shown in FIG. 5, and gradually cooled to take out the rod-shaped ingot 6 from the lower crucible 2. .

When the raw material is melted in the upper crucible 1 and supplied to the lower crucible 2 in this way, the melting of the raw material and the growth of the single crystal are performed in different crucibles.
The width d of the melt zone 5 of the lower crucible 2 can be adjusted to be constant. Therefore, it is possible to grow a single crystal while suppressing the mixture of platinum and the composition segregation constituting the crucible.

Further, in particular, in this embodiment, the spout pipe 4 of the upper crucible 1 is provided in the vertical direction, and the inner diameter of the spout pipe 4 is 4 mm to 12 mm.

When the spout pipe 4 extends in the vertical direction in this way, the pouring spout extends obliquely so as to approach the inner wall of the lower crucible, as compared with the shape of the pipe. The length is short. Therefore, as the length of the spout pipe is shorter, the amount of the molten raw material left unmelted on the inner wall surface of the pipe can be suppressed. Further, in the spout pipe provided in the vertical direction, the molten raw material flows more easily than in the spout pipe provided in the oblique direction, which also suppresses unmelted residue.

Therefore, various inconveniences caused by the unmelted portion, that is, a decrease in the yield due to the single crystal ingot becoming shorter than a predetermined length and a deterioration in the quality of the single crystal ingot due to the fluctuation of the feed rate of the molten raw material are prevented. At the same time, it is not necessary to adjust the amount of the raw material in consideration of the unmelted residue, and the quality and productivity of the ferrite single crystal are improved.

However, in order to obtain such an effect, it is necessary that the inner diameter of the spout pipe is 4 mm to 12 mm. When the inner diameter of the spout pipe is less than 4 mm, it becomes difficult for the molten raw material to flow in the pipe, the unmelted raw material increases in a large amount, the feed rate of the molten raw material varies, and a grown crystal has a different phase. Will end up. If the inner diameter of the spout pipe exceeds 12 mm,
Since the area of the inner wall surface of the pipe increases, the amount of the molten raw material that remains attached to the inner wall surface of the pipe and remains unmelted increases.

[0030]

EXAMPLES Specific examples of the present invention will be described based on experimental results.

Example 1 As the upper crucible, a spout pipe having an inner diameter of 4 mm provided in the vertical direction was used.
An n-Zn ferrite single crystal was grown.

Examples 2 and 3 Mn-Zn ferrite single crystals were grown in the same manner as in Example 1 except that the inner diameter of the spout pipe of the upper crucible was changed as shown in Table 1.

Comparative Example 1 and Comparative Example 2 As in Example 1, except that the inner diameter of the spout pipe of the upper crucible was set to a value outside the predetermined range (4 to 12 mm) as shown in Table 1. An Mn-Zn ferrite single crystal was grown.

Comparative Example 3 As the upper crucible, a pipe having an inner diameter of 8 mm and a spout pipe obliquely provided was used.
A Zn-based ferrite single crystal was grown.

The above Examples 1 to 3 and Comparative Examples 1 to
Table 1 shows the unmelted amount of the ferrite raw material generated in Comparative Example 3, the length of the grown single crystal ingot, and the evaluation results of crystallinity.

In the crystallinity of Table 1, ◯ indicates that the single crystal ingot has no heterogeneous phase, and Δ indicates that the heterogeneous phase has occurred. However, the cross sectional area occupied by the heterogeneous phase is 10% or less of the ingot cross sectional area. In some cases, x indicates that the cross-sectional area occupied by the different phase exceeds 10% of the ingot cross-sectional area.

The ingot length was set to 270 mm, and the allowable range of error was 3 to 4 mm.
As a rough estimate, the allowable range of the undissolved amount of the ferrite raw material is 50 g or less.

[0038]

[Table 1]

As can be seen from Table 1, in Examples 1 to 3 in which the upper crucible provided with the spout pipe having an inner diameter of 4 to 12 mm in the vertical direction was used, the unmelted residual amount of the ferrite raw material was small. Suppressed, a single crystal ingot of a predetermined length is grown with good crystallinity.

On the other hand, in Comparative Example 3 in which the spout pipe provided obliquely was used as the upper crucible,
Although the inner diameter of the spout pipe is the same as that in this case, the unmelted ferrite raw material is larger than in Example 2 in which the pipe direction is vertical. Therefore, the grown single crystal ingot is 12 mm shorter than that in the case of Example 2, and the crystal has a different phase.

From this, it is understood that the pouring port pipe of the upper crucible should be provided in the vertical direction rather than the oblique direction in order to suppress unmelted ferrite raw material.

However, even when the spout pipe is provided in the vertical direction, the unmelted amount of the ferrite raw material largely varies depending on the inner diameter of the pipe.

In Comparative Example 2 in which the inner diameter of the spout pipe was increased to 16 mm, a large amount of raw material remained in the spout pipe, and the ingot length was shortened by 7 mm as compared with the first or second embodiment.

Further, in Comparative Example 1 in which the inner diameter of the spout pipe is reduced to 2 mm, it is difficult for the molten raw material to flow from the spout pipe, and much unmelted residue remains. Moreover, many different phases were generated in the crystals, suggesting that the supply of the molten raw material was discontinuous.

From the above, the inner diameter of the spout pipe is 4
It has been found necessary to be within the range of -12 mm.

[0046]

As is apparent from the above description, in the present invention, when a ferrite single crystal is grown by the double crucible method, a spout pipe is provided vertically as an upper crucible, and the spout pipe Inner diameter is 4mm-1
Since the diameter of 2 mm is used, it is possible to reduce the amount of the ferrite raw material left undissolved in the upper crucible, and it is possible to grow a ferrite single crystal having a small composition segregation and good crystallinity with a stable length. .

[Brief description of drawings]

FIG. 1 is a schematic view showing a step of growing a ferrite single crystal in order and showing a raw material preparation step.

FIG. 2 is a schematic diagram showing a process of starting melting of raw materials.

FIG. 3 is a schematic diagram showing a single crystal crystallization initiation process.

FIG. 4 is a schematic diagram showing a single crystal growth process.

FIG. 5 is a schematic view showing a termination process of single crystal crystallization.

FIG. 6 is a schematic diagram showing a spout pipe of an upper crucible used in a conventional double crucible system.

[Explanation of symbols]

 1 Upper crucible 2 Lower crucible 3 Ferrite raw material 4 Spout pipe 5 Melt zone 6 Ferrite single crystal

Claims (1)

[Claims] 1. An upper crucible having a spout pipe at a lower end and a lower crucible are used. A ferrite raw material is loaded in the upper crucible, and the upper crucible and the lower crucible are passed through a furnace having a temperature gradient to obtain an upper crucible. While growing the ferrite single crystal in the lower crucible while supplying the ferrite raw material melted in the lower crucible through the spout pipe, install the upper crucible spout pipe in the vertical direction and set the inner diameter of this spout pipe to 4 mm. The method for producing a ferrite single crystal is characterized in that it is set to 12 mm.