JPH0597573A - Method for growing single crystal of oxide - Google Patents

Abstract

PURPOSE:To prevent the melting of a Pt (or a Pt alloy) crucible of maintaining growing melt in growing an oxide crystal such as garnet single crystal film or ferrite single crystal by liquid-phase epitaxial(LPE) method or Bridgman(Br) method. CONSTITUTION:In a method for solidifying and growing single crystal from a melt 3 prepared by heating and melting an oxide raw material packed into a metallic crucible 1, an electrode 2 made of a material different from the metallic crucible 1 is immersed in the melt 3, electric voltage obtained by subtracting an electric potential difference corresponding to thermoelectromotive force generating between the crucible 1 and the electrode 2 at the temperature of the melt 3 from potential difference between the crucible 1 and the electrode 2 immersed in the melt 3 is kept approximately zero to grow a single crystal of oxide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for growing an oxide single crystal grown from a melt held in a metal container such as a metal crucible in oxygen or air atmosphere.

[0002]

2. Description of the Related Art Czochralski (CZ) method and flux (Flux) are typical methods for growing oxide single crystals.
Method, or Bridgman method, etc. are known, but for growing an oxide garnet single crystal film that is useful for applications such as magnetic bubble memory, microwave element, magneto-optical element, liquid phase epitaxial ( LPE) method is used.
In any of the growing methods described above, a container for holding the raw material melt is required in any method, but it is common to use a noble metal for the material of the container when growing an oxide single crystal. .. This is because the above conditions are at a high temperature and in an oxidizing atmosphere, so a material having a high melting point and excellent corrosion resistance is required.

[0003]

However, when an oxide garnet single crystal film is grown by the LPE method for use as a microwave element and a magneto-optical element, the melt of a Pt crucible used as a container is brought into contact with the melt. It was found that the part that was melted melted in the melt. For magneto-optical elements,
It is known that when Pt melted in the melt is mixed in the film, light absorption is increased (“Japan Applied Magnetics Society”, V
OL. 10, No. 2, (1986) P.I. 161). In addition, Pt contributes to the film defect (“J, Mag
n, Soc, Jpn "VOL. 11, SI (1987)
P. 347), it is known that the optical characteristics of the defective portion are deteriorated ("Japan Applied Magnetics Society", VOL. 10, N).
o. 2, (1986) P.I. 147). On the other hand, even when a ferrite single crystal was grown by using the Br method, the Pt—Rh alloy crucible used as the container was melted and the Pt was mixed into the crystal, so that the growth yield was greatly reduced. Therefore, Pt crucible (or alloy mainly composed of Pt)
Melting is a very serious problem.

[0004]

The present invention relates to a method for growing an oxide single crystal in which a single crystal is solidified and grown from a melt obtained by heating and melting an oxide raw material filled in a metal container such as a metal crucible. An electrode made of a different material is contacted with or immersed in the melt, and a voltage obtained by subtracting a potential difference corresponding to a thermoelectromotive force generated between the metal container and the electrode from a potential difference between the metal container and the electrode is obtained. This is a method for growing an oxide single crystal, which is characterized in that it is maintained at substantially zero.

The present inventors previously proposed that the material of the electrode is the same as that of the metal crucible, the electrode is immersed in a molten liquid, and the potential difference between the crucible and the electrode is kept substantially zero (Japanese Patent Application No. However, if the material of the electrode is different from that of the crucible, a thermoelectromotive force is easily generated between the crucible and the electrode. For example, the R type thermocouple according to the new JIS standard is 13.0% Rh-bal.
Although this is a combination of Pt material and 100% Pt material, the standard thermoelectromotive force of this thermocouple at about 800 ° C is about 7.9 m.
v. Therefore, when each material of the present thermocouple is used as an electrode and a crucible material, it can be easily analogized that a thermoelectromotive force is easily generated between them. However, when it is used as a thermocouple, it is general that the temperature measuring part is sufficiently contacted with or welded to remove the contact resistance. The positional relationship between the electrode and the crucible in the present invention changes variously depending on the shape of the electrode and the crucible, the type of crystal, and the like, but it is not preferable to contact them. Therefore, the thermoelectromotive force generated between the electrode and the crucible in the present invention is much smaller than that in the case where the thermocouple is constructed. However, if the potential difference in the melt is not so large, the effect of thermoelectromotive force cannot be ignored. The results of measuring the potential difference in the melt for growing the bismuth-substituted garnet film at various temperatures are shown in Table 1. The potential difference at about 800 ° C. is about 2 m.
It is about v.

[Table 1] Since the thermoelectromotive force at 800 ° C. of the above-mentioned R type thermocouple is about 7.9 mv, the electromotive force is much larger than the potential difference. The potential difference shown in Table 1 was measured by connecting the electrode inserted in the melt to the positive terminal of the measuring instrument and connecting the crucible side to the negative terminal.

From the above viewpoint, the present invention is characterized by the above-mentioned configuration. An example of the circuit implemented in the present invention is shown in FIG.

[0007]

EXAMPLES The present invention will be described below with reference to examples. (Example 1) a magneto-optical element as a raw material component and _{application, Bi 2 O 3, Tb 4} O 7, Gd 2 O 3, Fe 2 O 3, Pb
Approximately 500 g of O and B ₂ O ₃ are weighed and mixed to obtain approximately 1
A 00 cc Pt crucible was filled. After placing the crucible in a growth furnace in the atmosphere and homogenizing at about 1100 ° C, about 7
The temperature was maintained at 90 ° C. 13% Rh-ba in the melt
While inserting an electrode of 1Pt alloy and measuring the potential difference between the electrode and the crucible, the voltage is controlled so that the potential difference obtained by subtracting the thermoelectromotive force from the potential difference at that time is zero, and the potential difference is about 36.
It was held for hr. Then, as a result of measuring the melting amount of the crucible, it was found to be about 0.12 g reduction.

(Example 2) Bi ₂ O ₃ , Tb ₄ O ₇ , Gd ₂ O ₃ and Fe ₂ were used as raw material components for a magneto-optical element.
Weighs about 3,200 g of O ₃ , PbO, and B ₂ O ₃ in total.
The mixture was mixed and filled in a Pt crucible of about 700 cc. The crucible was placed in a growth furnace in the atmosphere, homogenized at about 1100 ° C, and then maintained at a temperature of about 790 ° C. 13 in the melt
% Rh-balPt alloy electrode is inserted and the potential difference between the electrode and the crucible is measured, and the voltage is controlled so that the potential difference obtained by subtracting the thermoelectromotive force from the potential difference at that time becomes zero, and the film is grown for about 36 hr. did. As a result of observing the film surface having a film thickness of about 490 μm with an optical microscope of 50 to 1000 times, the defect density was about 2 cells / cm ² .

(Comparative Example 1) Bi ₂ O ₃ , Tb ₄ O ₇ , Gd ₂ O ₃ and Fe ₂ were used as raw material components for a magneto-optical element.
A total amount of about 500 g of O ₃ , PbO, and B ₂ O ₃ was weighed and mixed, and filled in a Pt crucible of about 100 cc. The crucible was placed in a growth furnace in the atmosphere, homogenized at about 1100 ° C., cooled to about 790 ° C., and held for about 36 hours. Then, as a result of measuring the melting amount of the crucible, it was found to be about 1.52 g of decrease.

Comparative Example 2 Bi ₂ O ₃ , Tb ₄ O ₇ , Gd ₂ O ₃ and Fe ₂ were used as raw material components for a magneto-optical element.
Weighs about 3,200 g of O ₃ , PbO, and B ₂ O ₃ in total.
The mixture was mixed and filled in a Pt crucible of about 700 cc. The crucible was placed in a growth furnace in the atmosphere, homogenized at about 1100 ° C., and then grown at about 790 ° C. for about 36 hr. Film thickness about 4
As a result of observing the film surface of 90 μm with an optical microscope of 50 to 1000 times, the defect density was about 860 cells / cm ² .

[0011]

According to the present invention, melting of the Pt crucible is remarkably suppressed, so that the amount of Pt mixed in the film is reduced and the light absorption is reduced. The floating Pt in the melt is reduced and the Pt core is reduced. The practical value is extremely large because the film defects are reduced, the crucible life is extended, the magneto-optical characteristics are improved, the device yield is improved, and the cost is greatly reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a circuit relating to voltage control of the present invention.

[Explanation of symbols]

 1 crucible 2 electrode 3 melt 4 operational amplifier

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toru Abe 5200 Sankejiri, Kumagaya City, Saitama Hitachi Metals Co., Ltd.

Claims (2)

[Claims] 1. A method for growing an oxide single crystal in which a single crystal is solidified and grown from a melt obtained by heating and melting an oxide raw material filled in a metal container, wherein an electrode made of a material different from that of the metal container is brought into contact with the melt. Immersion, the potential difference between the metal container and the electrode, the voltage obtained by subtracting the potential difference corresponding to the thermoelectromotive force generated between the metal container and the electrode is maintained at substantially zero oxide single Crystal growth method. 2. The metal container is a metal crucible.
A method for growing an oxide single crystal as described in 1.