JPH03141187A - Growing method of single crystal - Google Patents

Abstract

PURPOSE:To obtain single crystal having a slight crystal defect and deposit of different phase with a simple magnetic field-imparting device by flowing direct electric current in a coil for magnetic field around metallic crucible in growing oxide single crystal with Bridgman method with imparting magnetic field to melt including the metallic crucible. CONSTITUTION:Raw material oxide is charged in a metallic crucible 1 and electricity of electric heater 6 in a melting furnace 5 is turned on, then the raw material is melted by heating to obtain a melt 9. Next, the metallic crucible 1 is gradually lowered in the furnace with the elevator device 10 to grow single crystal. In said method, a coil 4 for magnetic field is wound on the metallic crucible 1 through insulator and connected to direct current electric source 8 with lead wires 2 and 3, then single crystal is grown with flowing direct electric current. By this method, elution of deposit of the metallic crucible component into melt 9 is prevented without requiring expensive electromagnet of a large scale to afford single crystal having extremely slight migration of crucible component without crystal defect.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an improvement of the Bridgman method for growing a single crystal of an oxide such as Mn-Zn ferrite using a metal crucible such as a platinum crucible.

(Prior art) Conventionally, when growing single crystals of oxides such as Mn4n ferrite, it is difficult to chemically react with these high melting point materials (and
A method of growing these compounds by melting them in a metal crucible with a higher melting point has been adopted. However, in reality, components of the metal crucible are often eluted and mixed into the melt as impurities, significantly reducing the quality of the single crystal. That is,
Crystal defects may occur due to the inclusion of impurities,
Because the metal precipitates as a different phase, the metal that has been precipitated as a different phase may fall off during the manufacturing process such as cutting and grinding the single crystal ingot, and the fallen metal fine particles may damage the single crystal, causing negative effects such as impairing dimensional accuracy. There were drawbacks such as variations in surface roughness, etc., which deteriorated product quality and yield.

(Problem to be solved by the invention) Conventionally, to solve this problem, a magnetic field is applied to the molten material including the crucible to suppress the convection of the molten material, and at the same time, the single crystal is grown while suppressing the diffusion of the crucible components mixed as impurities. A method has been adopted to prevent the contamination of crucible components by growing the crucible.

(Japanese Patent Publication No. 58-41795, Japanese Patent Application Publication No. 59-21593,
Hei 1) Yo.

metal p30. No. 3'86). However, these methods require a strong magnetic field of usually several hundred to several thousand oersteds to suppress the convection of the melt, making them expensive and large-scale. There were disadvantageous problems with patents featuring its stones.

The object of the present invention is to improve such drawbacks and provide an extremely high-quality single crystal in which metal crucible components are less mixed into the crystal, and crystal defects and foreign phase precipitation are less.

(Means for Solving the Problem) In order to solve the problem, the present inventors focused on the physical properties of crucibles and melts and the influence of magnetic fields, and as a result of various studies, they arrived at the present invention. The gist is that when growing oxide single crystals using a metal crucible,
This is a single crystal growth method characterized by providing a magnetic field coil around the straight body of a metal crucible and flowing a direct current to grow a single crystal while applying a magnetic field to the molten oxide.

The present invention will be explained in detail below.

Generally, the metal crucible components and the molten material have different electrical conductivities, and therefore, in a magnetic field, the metal crucible components receive a force of a different magnitude than the molten material. The present invention takes advantage of this phenomenon, and attempts to prevent the metal crucible components from diffusing into the melt by applying a magnetic field to the metal crucible containing the melt. It has been shown that a large magnetic field of hundreds to thousands of Oersteds is not necessary to suppress the convection of the melt, and that even a magnetic field of several tens of Oersteds is sufficient to prevent the diffusion of metal crucible components. I found it.

Therefore, there is no need for a large-scale and expensive electromagnet as was conventionally said.In the present invention, a coil is wound around the straight body of the metal crucible while insulating it from the metal crucible, and a direct current is passed through it. It was confirmed that mixing of crucible components can be controlled using a magnetic field. In this method, a longitudinal magnetic field is generated with respect to the metal crucible. The electromagnetic force acting on an electrically conductive substance moving in a magnetic field is at its maximum when the direction of movement is perpendicular to the magnetic field. That is, when the crucible component eluted from the metal crucible attempts to head toward the center of the crucible, the electromagnetic force acts most strongly in the direction that attempts to prevent it. Although this method generates a magnetic field of only a few tens of Oersteds,
This is sufficient in terms of suppressing the diffusion of metal crucible components.

The present invention will be explained in comparison with the conventional method using drawings.
In FIG. 3, a single-crystal raw material oxide is charged into a metal crucible 1 using a conventional method, and electricity is applied to an electric heater 6 of a melting furnace 5 to raise the temperature and melt it to form a molten material 9. Next, the metal crucible is gradually lowered in the furnace by the crucible lifting device 10, and the growth of a single crystal is started by slow cooling from the inverted conical part of the metal crucible.The temperature control is continued until the single crystal reaches the melt surface. become In contrast, in the present invention, as shown in FIG. 1, a magnetic field coil 4 is wound around a metal crucible 1 via an insulator, and connected to a DC power source 8 through a lead wire 2.3 to supply a DC current. By growing a single crystal while flowing the melt, the metal crucible components are prevented from elution and precipitation into the melt.

The scope of application of the present invention is Mn-Zn as a single crystal material.
Examples include ferrite and GGG. Examples of metal crucible materials include Pt, Pt-Ru, Ru, and Ir.

Hereinafter, specific embodiments of the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

(Example, Comparative Example) A 21φ platinum wire was wound 40 times around the straight body of a platinum crucible (100% purity) while being insulated with ceramics (alumina) to obtain a magnetic field coil. Mn-Zn ferrite (MnO-25 mol%, Zn0 25 mol%, Fe
3,600 gr of powder (50 mol%)
It was placed in a melting furnace and heated to 1700°C to melt it. Next, a direct current of 10 A was applied to the melt through a magnetic field coil to apply a magnetic field of 23.50 oersted at the center of the crucible while gradually lowering the melt into the crucible to grow a single crystal.

This single crystal was cut perpendicularly to the growth direction, and the amount of platinum mixed and precipitated observed at five locations on the cut surface using a projector was measured as the number of particles. The average values of the results are shown in Table 1, and the schematic diagram of the platinum precipitation state in the cross section of the single crystal is shown in Table 2 (2-1
) shown in the figure. Separately, Mn-Zn ferrite single crystals were grown under the same conditions as in the example except that no magnetic field was applied, and the amount of precipitated platinum mixed was measured.
2-2) Expressed in the figure.

Table 1 As shown in Table 1, it can be seen that the amount of precipitated platinum mixed in was smaller in the example in which the growth was performed while applying a magnetic field to As shown in the cross-sectional view taken in the vertical direction, Example (2-1)
In the figure, platinum particles were precipitated concentrated around 3 to 5 mm from the crucible side, indicating that the magnetic field prevented the platinum particles from diffusing to the center of the crucible.

(Effects of the Invention) When growing a single crystal of an oxide using a metal crucible, the present invention provides a magnetic field coil around the straight body of the metal crucible and flows a direct current to apply a magnetic field to the molten oxide. This is a single crystal growth method characterized by growing a single crystal while giving a By preventing this, it is possible to produce a high-quality single crystal with extremely few crystal defects without installing an expensive and large electromagnet, and it is extremely useful in industry.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of an embodiment of the present invention;
The figure is an explanatory diagram of the conventional method. FIG. 2 shows the present invention (2-
1) is a cross-sectional view of a single crystal produced by the conventional method (2-2), and is a schematic diagram showing the distribution of crucible components precipitated in the single crystal. The main symbols in the figure are as follows.

Claims (1)

[Claims] When growing oxide single crystals using a metal crucible,
A single crystal growth method characterized by providing a magnetic field coil around the straight body of a metal crucible and flowing a direct current to grow a single crystal while applying a magnetic field to a molten oxide.