JPS60231491A - Manufacture of single crystal - Google Patents

Abstract

PURPOSE:To grow high-quality single crystal excellent in crystallizability and uniformity of the composition by passing slowly a crucible holding the melt contained raw material through the inside of a furnance having temp. gradient while rotating the crucible acceleratedly and deceleratedly. CONSTITUTION:A crucible (made of platinium) 1 incorporated with raw material is decended through the inside of a furnace 2 in which the temp. gradient typically showed at the right side of the figure is formed with a heating heater and the raw material incorporated in the crucible 1 is competely melted to make melt 3 and the melt 3 is stitted and made uniform composition through rotating the crucible 1 acceleratedly and deceleratedly in the X direction shown by an arrow. Then, at the point of time at which the lower end of the crucible 1 is reached the point A being crystallizing temp., the melt 3 is cooled below the crystallizing temp. to grow single crystal 4. The decending of the crucible 1 is continued and it is slowly cooled to obtain rod-shaped high-quality single crystal 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a single crystal, and more particularly to an improvement in the method for producing a single crystal using the Bridgman method.

[Background technology and its problems]

Conventionally, various methods have been known for producing various single crystals, but the Bridgman method, which is easy to operate and requires simple equipment, is particularly widely used. The Bridgman method uses temperature gradients to advance crystallization. For example, a platinum crucible containing a molten sample is moved through a furnace with a temperature gradient while rotating at a constant rate, and one end of the molten sample is moved. It is cooled to crystallize and then gradually grows. According to this Bridgman method, it is possible to create large single crystals of salts, etc., rather than metals, and it is also possible to produce single crystals of optical materials, magnetic materials, semiconductors, various alloys, etc. industrially. It is used to.

However, in the BuIJ and Ziman methods mentioned above, all raw materials are melted in advance in a crucible and then gradually cooled from the tip of the crucible to grow a single crystal, so it is especially difficult to use multi-component raw materials. In this case, so-called compositional segregation occurs, and there is a drawback that the composition of the crystals produced differs between the front end and the rear end of the crucible. In general, for multi-component raw materials, in a phase diagram showing the relationship between the composition and melting point, the liquid phase is the temperature at which the liquid phase and solid phase are in equilibrium, unless it is the eutectic point. This is due to the fact that the line does not match the solidus line drawn regarding the composition of the solid phase. If compositional segregation occurs in the crystal and the composition differs depending on the location, the physical properties will also differ, making it difficult to ensure a desired quality. For example, in a magnetic material such as ferrite, the magnetic permeability changes if the crystal composition differs, and when the obtained single crystal is processed into a magnetic head, it is difficult to determine whether the crystal used is the tip or the rear end of the single crystal. Performance will vary greatly depending on the

Furthermore, when a single crystal is produced by the Bridgman method described above, so-called low-angle grain boundaries with small angle deviations are likely to occur, and the crystallinity of the obtained single crystal may be deteriorated.

[Purpose of the invention]

The present invention was proposed in view of the above-mentioned circumstances, and aims to provide a method for producing a single crystal that can grow a high-quality single crystal with excellent crystallinity and uniform composition.

[Summary of the invention]

That is, the feature of the method for producing a single crystal according to the present invention is that while growing a single crystal by gradually passing a melt containing raw materials through a furnace having a temperature gradient, the melt is held. The single crystal is grown by accelerating and decelerating the rotation of the crucible, whereby the melt is constantly stirred and the composition of the melt remains constant, so the composition of the growing single crystal is also controlled uniformly. It is. What should be further noted is that by performing the above-mentioned acceleration and deceleration rotation, the low-angle grain boundaries of the obtained single crystal disappear, and the crystallinity is improved.

〔Example〕

Hereinafter, a method for producing a single crystal according to the present invention will be explained with reference to the drawings. , FIG. 1 shows an example of an apparatus for realizing single crystal production by the Bridgman method.

In FIG. 1, the crucible 1 is made of platinum,
Further, a temperature gradient as schematically shown on the right side of FIG. 1 is formed in the furnace 2 by a heater.

First, when the crucible 1 made of platinum is gradually lowered into the furnace 2, the raw material in the crucible 1 is completely melted and becomes a melt 3.

Subsequently, when the crucible 1 is lowered further, the lower end of the crucible 1 reaches A where the temperature inside the furnace 2 is the crystallization temperature.
At this point, the melt 3 is cooled below the crystallization temperature and a single crystal 4 begins to crystallize.

Finally, the crucible 1 continues to descend until all of the melt 3 becomes a single crystal 4, and is gradually cooled to form a rod-shaped single crystal 4.
Take out.

At this time, in the present invention, the crucible 1 is subjected to acceleration and deceleration rotation in the direction of the arrow X in the figure. This acceleration and deceleration rotation is achieved, for example, by repeating the operation of gradually increasing the rotation speed and gradually lowering the rotation speed when it reaches a predetermined rotation speed. It may be rotation, or it may be acceleration and deceleration forward and reverse rotation that repeats forward rotation and reverse rotation.

By applying acceleration and deceleration rotation to the crucible 1 in this manner, the crystallinity, compositional uniformity, etc. of the obtained single crystal are significantly improved.

For example, as shown in Fig. 2A to Fig. 2C in crucible 1,
A single crystal of ferrite was produced by subjecting it to rotation.

In addition, FIG. 2 A shows a case (comparative example) in which rotation is given at a constant speed at a rotation speed of 6 rpm, and FIG. 2 B11-10 to 8
FIG. 2C shows a case where forward rotation with acceleration and deceleration is applied in the range of 0 to 8 rpm (Example 1), and FIG.

The appearance of the surface of the single crystal obtained in each example and comparison flJ is shown in FIGS. 3A to 3C. FIG. 3A shows a single crystal obtained in a comparative example, in which low-angle grain boundaries were observed, and the width of each low-angle grain boundary was about 5 mm. FIG. 3B shows the single crystal obtained in Example 1, in which narrower low-angle grain boundaries than in the previous comparative example were observed, and the width was about 1 mm. FIG. 3C shows the single crystal obtained in Example 2, in which no low-angle grain boundaries were observed.

FIG. 4 shows the relationship between the rotation ΔR applied to the crucible 1 and the width of the low-angle grain boundary of the obtained single crystal.

Note that the above ΔR indicates the amount of change in the rotational speed of rotation, and for example, in the comparative example, ΔR−0°, and in Example 1, ΔR28. In Example 2, ΔR216.

It can be seen from Figure 4 that as ΔR increases, the width of the low-angle grain boundaries becomes narrower, and when ΔR≧16, the low-angle grain boundaries of the single crystal obtained completely disappear. .

Next, Figures 5 to 5C show the permeability-temperature characteristics of the obtained single crystal. In each of these figures, curve a is the magnetic permeability-temperature characteristic at the tip of the obtained single crystal, curve A is the magnetic permeability-temperature characteristic at the center of the obtained single crystal, and curve C is the magnetic permeability-temperature characteristic at the rear end of the obtained single crystal. The magnetic permeability temperature characteristics of each are shown.

Figure 5 shows the magnetic permeability-temperature characteristics of the single crystal obtained in the comparative example. The temperature at which the magnetic permeability of the rear end portion reaches a maximum is approximately 60°C, whereas the temperature at which the magnetic permeability of the rear end portion reaches a maximum is approximately 170°C. From this, it is presumed that compositional segregation occurs in the single crystal obtained in the above comparative example, and the composition differs greatly depending on each part.

FIG. 5B shows the magnetic permeability temperature characteristics of the single crystal obtained in Example 1, and each curve 8 to curve C almost coincide with each other, but the temperature at which the magnetic permeability reaches its maximum is reached at the tip and the rear. It can be seen that there is some misalignment at the edges. For example, the temperature at which the magnetic permeability at the tip reaches its maximum is 1100°C, while the temperature at which the magnetic permeability at the rear end reaches its maximum is 180°C.
It is.

From this, it is presumed that in this implementation ψ131, although the compositional segregation is considerably improved, there is a slight deviation in the composition.

FIG. 5C shows the magnetic permeability temperature characteristics of the single crystal obtained in Example 2, and each curve 8 to curve C agree well.
It can be seen that the temperatures at which the magnetic permeability is maximum also match well in each part. From this, it is presumed that in Example 2, compositional segregation was eliminated and the composition of the resulting single crystal was made uniform.

FIG. 6 shows the relationship between the rotation ΔR given to the crucible 1 and the temperature difference ΔT between the temperature at which the magnetic permeability is maximum at the leading end and the temperature at which the magnetic permeability is maximum at the rear end of the resulting single crystal.

As shown in Fig. 6, as ΔR increases, the temperature difference Δ
T decreases, and compositional segregation gradually improves.

I understand that. In particular, when ΔR≧16, the above temperature difference ΔT
It is therefore presumed that uniformity of the crystal composition has been achieved.

〔Effect of the invention〕

As described above, in the method for producing a single crystal according to the present invention, acceleration and deceleration rotation is applied to the crucible that holds the melt when growing a single crystal by the Bridgman method, so that the composition of the melt can be changed. Uniformity is achieved, and therefore the resulting single crystal has excellent compositional uniformity, and furthermore, crystallinity is greatly improved.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of an apparatus used to realize the single crystal manufacturing method according to the present invention. Figure 2 Figure 2 to Figure 2 C are drawings schematically showing changes in the rotational speed given to the crucible, Figure 2 Figure 2 Figure 2 is a comparative example,
FIG. B shows one embodiment of the present invention, and FIG. 2C shows another embodiment. Figures 3 to 3C are schematic 9A+1 views showing the surface appearance of the vinegar crystals obtained, and Figure 4 shows the amount of change ΔR in the rotational speed given to the crucible and the amount of the single crystal obtained. FIG. 3 is a characteristic diagram showing the relationship between the widths of tilt grain boundaries. Figures 5 to 5C show the tip and center portions of the single crystals obtained. FIG. 5 is a characteristic diagram showing a comparison of magnetic permeability and temperature characteristics at the rear end portion, where FIG. 5 shows a single crystal obtained in a comparative example, and FIG. 5 B shows a single crystal obtained in an example of the present invention. , and FIG. 5C show the magnetic permeability-temperature characteristics of single crystals obtained in other embodiments of the present invention. Figure 6 shows the relationship between the amount of change ΔR in the rotational speed given to the crucible and the temperature difference ΔT between the temperature at which the magnetic permeability is maximum at the leading end and the temperature at which the magnetic permeability is maximum at the rear end of the resulting single crystal. FIG. 1... Crucible 2... Furnace 3... Melt 4... Single crystal patent applicant Sony Corporation representative Patent attorney Mimi Koike 1) Sakae Mura - Figure 1 Figure 2 (A) Figure 6

Claims (1)

[Claims] When growing a single crystal by gradually passing a melt containing raw materials through a furnace with a temperature gradient, the single crystal is grown while accelerating and decelerating the rotation of the crucible that holds the melt. Characteristic single crystal production method