JP2000344593A - Crucible for growing single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deformation of the form of a crucible and to inhibit the mixing of a crucible material into a growing crystal by growing an oxide single crystal in an oxygen atmosphere at a specified temp. using the crucible obtained by covering the whole surface of a crucible main body made of a high melting point metal or an oxide, with platinum. SOLUTION: A crucible for growing a single crystal, especially, an oxide single crystal is obtained by covering the whole surface of a crucible main body made of a high melting point metal or an oxide with a platinum layer 2. As the high melting point metal, iridium, rhodium or tungsten hard to form an intermetallic compound with platinum is preferable, and as the oxide, aluminum oxide or zirconium oxide is suitable. Further, the covering of the crucible with platinum is carried out by sticking a platinum plate or dry or wet plating to form the platinum layer 2 on the crucible main body 1. The crucible thus obtained can be used for growing the oxide single crystal in an oxygen atmosphere at 1,400 to 1,770 deg.C without occurrence of deformation and contamination.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a crucible for growing a single crystal, and more particularly to a crucible for melting a raw material used for growing an oxide single crystal.

[0002]

2. Description of the Related Art Crucibles made of platinum or iridium, which are noble metals, are widely used as crucibles for melting raw materials used for growing oxide single crystals. The crucible material is selected according to the melting temperature of the melt or solution of the material to be grown and the reactivity with the raw materials. Platinum and iridium generally have reactivity with oxides and are widely used as crucible materials. From the viewpoint of the melting temperature, when growing a single crystal from a raw material having a melting temperature of 1400 ° C. or lower, platinum which is rich in workability and inexpensive is often selected. Further, when growing a single crystal from a material having a melting temperature of 1770 ° C. or higher, in which the platinum starts to soften or melt and cannot maintain the shape of the crucible, an iridium crucible is selected. In the range of 1400 ° C. to 1770 ° C., which is in the middle of the above temperature range, crucibles mainly made of four kinds of materials are widely used. In particular,
(1) Platinum with severe deformation of crucible with reduced strength, (2)
Platinum-rhodium alloys and platinum-iridium alloys whose melting points are raised, (3) zirconium oxide-added platinum whose strength is higher than platinum, and (4) iridium for high temperatures.

However, each of the crucibles used at the intermediate temperature has the following disadvantages. In the case of a platinum crucible, the shape of the crucible is remarkably deformed due to repeated melting and solidification of the raw material due to repeated use, and the number of times of use of growing a single crystal of the crucible is remarkably reduced as compared with the number of uses of 1400 degrees or less. In the case of a platinum crucible to which zirconium oxide is added, the melting point of the crucible material does not change, so that when used at 1600 ° C. or higher, the mechanical strength is reduced similarly to the platinum crucible, and the crucible shape is severely deformed. In the case of a platinum-rhodium alloy crucible,
Rhodium dissolves into the raw material and mixes with the grown crystal. Platinum-
In the case of an iridium alloy or an iridium crucible, the use atmosphere is limited to an inert atmosphere such as nitrogen, argon, and helium. In an oxygen atmosphere, the crucible material is severely oxidized and cannot be used.

[0004] Therefore, in view of the number of times a single crystal is grown in a crucible and suppression of contamination of the grown single crystal with impurities, a platinum-iridium alloy or iridium has been widely used as a crucible material.

[0005]

However, since the grown single crystal is an oxide, it contains oxygen as a constituent element. When an oxide single crystal is grown in an inert atmosphere such as nitrogen, the amount of oxygen taken into the grown single crystal is often insufficient, and crystal quality deterioration due to a crystal defect called oxygen deficiency has been a problem.

In the present invention, when growing an oxide single crystal,
An object of the present invention is to provide a crucible for growing a single crystal in which the shape of a crucible is not deformed in an oxygen atmosphere in a temperature range of 1770 ° C. or lower and the crucible material is not mixed into a grown crystal.

[0007]

In order to solve the above-mentioned problems, a single crystal growing crucible according to the present invention has a base having a crucible body made of a high melting point metal, and the entire surface of the crucible body is coated with platinum. It is characterized by having done.

The second crucible for growing a single crystal according to the present invention is characterized in that the base material has an oxide crucible body, and the entire surface of the crucible body is covered with platinum.

The present invention is characterized in that the substrate has a structure in which the melting point does not lower than that of platinum due to the reaction with platinum and the substrate has a high mechanical strength and the entire surface of the substrate is coated with platinum that can withstand an oxygen atmosphere. And

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION As a base material having a low reaction temperature with platinum at a working temperature range of 1770 ° C. or lower, a metal material that does not generate an intermetallic compound with platinum is preferable. That is, it is desirable to use a high-melting-point metal which forms a solid solution with platinum as a base material. From this point of view, iridium,
Rhodium and tungsten were selected. In addition, if the effect of suppressing the crucible breakage due to the ductility peculiar to the metal is neglected, it is also possible to select an oxide crucible represented by highly filled alumina as the base material. When the operating temperature range is 1400 ° C. or lower, a platinum crucible is generally used from the viewpoint of economy, but it goes without saying that a crucible having this configuration can also be used. Aluminum oxide or zirconium oxide is selected as such an oxide.

The method of coating may be a method in which a platinum plate is adhered to a previously prepared crucible main body or a method in which a platinum layer is formed on a previously prepared crucible main body by dry plating or wet plating.

In addition, when a high-frequency heating method is selected as a method for heating the raw material melt, it is desirable to form a region that contributes to heating by an eddy current generated in the surface layer of the crucible with a uniform material. Specifically, the heating area of the crucible can be calculated from the surface of the crucible by the following formula using skin depth (S
Kin Depth) D (cm) (CS Dun)
can, R .; H. Hopkins and R.A. Maz
Elsky, Journal of Crystal
Growth, 11 (1971) 50).

D = 3570 (ρ / fμ) 1/2 Here, ρ, f, and μ are resistivity (unit: Ωc
m), the applied high frequency (unit Hz), and the effective magnetic permeability. From this formula, platinum skin depth (Ski) heated to 1600 ° C by a high-frequency transmitter with an applied frequency of 125 kHz
n Depth) D can be calculated as 0.8 mm. In the single crystal growing crucible of the present invention having a platinum-substrate-platinum cross-sectional structure, the thickness of the platinum layer outside the crucible body that contributes to heating preferably has a thickness equal to or greater than the skin depth D calculated by the above equation. . Because, when the thickness of the platinum layer outside the substrate crucible is less than the skin depth D, a high frequency is applied to both the crucible body and the platinum layer outside the crucible body, but an eddy current bias occurs due to a difference in resistivity, This is because it may cause crucible damage.

[0014]

Embodiment 1 Embodiment 1 will be described below. FIG. 1 is a schematic diagram illustrating a single crystal growing crucible used in the present invention. 1 is a crucible body and 2 is a platinum layer. In this example, the base material of the crucible body was iridium.

Outer shape 60 mm, height 60 mm, wall thickness 1.5
A crucible was prepared by coating the entire surface of a crucible body made of iridium with a thickness of 0.5 mm inside the crucible body and 1.0 mm outside the thickness of the crucible body. The produced crucible was once heated to 1400 ° C., and the iridium crucible body 1 and the surface platinum layer 2 were fixed.

The crucible thus prepared was treated with Sr having a melting point of 1550 ° C.
_It was used for growing _0.61 Ba _0.39 Nb ₂ O ₆ single crystal. For the heating, a high frequency transmitter with an applied frequency of 125 kHz was used.
When growing a single crystal in an oxygen atmosphere of 1 atm of oxygen,
No oxidation occurred on the crucible surface, and no crucible deformation occurred. When the same experiment was performed using a platinum crucible having an outer shape of 60 mm, a height of 60 mm, and a wall thickness of 3 mm, no oxidation of the crucible occurred, but the crucible was deformed from the first time and could only be used for five times of single crystal growth. In addition, damage due to high-frequency current concentration may occur. On the other hand, the iridium crucible covered with platinum did not show signs of oxidation and deformation even when used for 50 single crystal growths.

[0017]

Embodiment 2 Hereinafter, Embodiment 2 will be described. FIG. 1 is a schematic diagram illustrating a single crystal growing crucible used in the present invention. 1 is a crucible body and 2 is a platinum layer. In this example, the base material was rhodium.

External shape 60 mm, height 60 mm, wall thickness 1.5
A crucible was prepared by coating the entire surface of a crucible body made of platinum having a thickness of 0.5 mm inside the crucible body and a thickness of 1.0 mm outside the crucible body. The produced crucible was once heated to 1400 ° C. to fix the rhodium crucible body 1 and the surface platinum layer 2. Melting point of melting point 1550 ° C
Sr _0.61 Ba _0.39 Nb ₂ O ₆ single crystal. For the heating, a high frequency transmitter with an applied frequency of 125 kHz was used. When the single crystal was grown in an oxygen atmosphere of 1 atm of oxygen, no oxidation occurred on the crucible surface and no crucible deformation occurred.

[0019]

Third Embodiment Hereinafter, a third embodiment will be described. FIG. 1 is a schematic diagram illustrating a single crystal growing crucible used in the present invention. 1 is a crucible body and 2 is a platinum layer. In this embodiment, the base material is tungsten.

Outer dimensions 60 mm, height 60 mm, wall thickness 1.5
A crucible in which the entire surface was covered with platinum having a thickness of 0.5 mm inside the crucible body and a thickness of 1.0 mm outside the crucible body was formed on a tungsten crucible body having a thickness of 1.0 mm. The produced crucible was once heated to 1400 ° C. to fix the tungsten crucible body 1 and the surface platinum layer 2 together. Melting point of melting point 15
It was used for growing Sr _0.61 Ba _0.39 Nb ₂ O ₆ single crystal at 50 ° C. For the heating, a high frequency transmitter with an applied frequency of 125 kHz was used. When the single crystal was grown in an oxygen atmosphere of 1 atm of oxygen, no oxidation occurred on the crucible surface and no crucible deformation occurred.

[0021]

Embodiment 4 Hereinafter, Embodiment 4 will be described. FIG. 2 is a schematic diagram illustrating a single crystal growing crucible used in the present invention. 1 is a crucible body and 2 is a platinum layer. In this example, the substrate was aluminum oxide.

External shape 60 mm, height 60 mm, wall thickness 1.5
mm, the inside thickness of the crucible body is 0.5 mm, and the outside thickness of the crucible body is 1.0 m
A crucible whose entire surface was covered with platinum of m was prepared. The temperature of the produced crucible was once raised to 1400 ° C. to fix the base aluminum oxide crucible body 1 and the surface platinum layer 2. Sr _0.61 Ba _0.39 with high frequency heating type pulling device
It was used for growing Nb ₂ O ₆ single crystals. For the heating, a high frequency transmitter with an applied frequency of 125 kHz was used. In order to prevent the raw material from being damaged by swelling during cooling of the melt, the raw material filling amount was set to 20% of the crucible capacity. When the single crystal was grown in an oxygen atmosphere of 1 atm of oxygen, no oxidation occurred on the crucible surface and no crucible deformation occurred. When a platinum crucible is used, holes are often generated in the crucible due to local concentration of high-frequency current. However, in the case of the crucible of the present embodiment, although the platinum layer on the outer wall side of the aluminum oxide crucible body through which the high-frequency applied current flows showed a change in platinum layer thickness indicating softening, the wettability between the aluminum oxide crucible body and platinum was observed. No holes were formed. Also, no change was observed in the platinum on the inner wall side of the aluminum oxide crucible main body, and the function of the crucible could be maintained.

[0023]

As described above, the present invention makes it possible to grow an oxide single crystal in an oxygen atmosphere at a temperature range of 1770 ° C. or less, and has no deformation in the crucible shape. There is an effect of providing a crucible for growing a single crystal in which no mixing occurs.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a crucible for growing a single crystal used in Examples 1 and 2 of the present invention.

FIG. 2 is a schematic sectional view of a single crystal growing crucible used in Examples 3 and 4 of the present invention.

[Explanation of symbols]

 1 Crucible body 2 Platinum layer

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Akiyuki Tate 3-19-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo F-term in Japan Telegraph and Telephone Corporation 4G077 MA02

Claims (5)

[Claims] 1. A crucible for growing a single crystal, wherein a substrate has a crucible body made of a high melting point metal, and the entire surface of the crucible body is coated with platinum. 2. The crucible for growing a single crystal according to claim 1, wherein said refractory metal is any one of iridium, rhodium and tungsten. 3. A crucible for growing a single crystal, wherein the substrate has a crucible body made of oxide, and the entire surface of the crucible body is coated with platinum. 4. A crucible for growing a single crystal according to claim 3, wherein said oxide is aluminum oxide or zirconium oxide. The crucible for growing a single crystal according to any one of claims 1 to 4, wherein the crucible is used in a temperature range of 1400 to 1770 ° C and in an oxygen atmosphere.