JPH085752B2 - Terbium aluminate single crystal and method for producing the same - Google Patents

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a terbium aluminate single crystal and a method for producing the same. More specifically, the present invention relates to a terbium aluminate single crystal useful as a superconducting device, a solid-state laser oscillation material scintillator material, and the like, and a method for producing the same.

2. Description of the Related Art In recent years, with the development of high-temperature oxide superconducting technology, there is a growing interest in high-performance superconducting thin films for application to electronic materials and electronic magnetic devices. Inorganic oxide single crystals have been attracting attention as a substrate for realizing this thin film, and various types have already been studied. For example, as a single crystal such as a substrate for a high temperature oxide superconducting thin film, MgO produced by the immersion arc melting method, SrTiO ₃ produced by the Bernoulli method, LaGaO ₃ produced by the Czochralski method (CZ method) , LaAl
O ₃ , NdGaO ₃ , LaGaO _{3 and the} like are known. However, all the single crystals known to date have drawbacks, for example MgO produced from immersion arc melting.
In the case of a single crystal, it is very difficult to obtain a high quality crystal because subgrains are present in the single crystal due to the fact that a seed crystal, which is a characteristic of the immersion arc melting method, is not used. Furthermore, in the production of a single crystal using such an immersion arc melting method, there is a problem that the single crystal cannot be grown to an arbitrary size. Further, in the case of SrTiO ₃ single crystal produced by Bernoulli method, since the dislocation density of SrTiO ₃ is relatively large, there is a problem that it is difficult to form a good high temperature oxide superconducting thin film. Even if it is desired to increase the diameter of the crystal, the limit is about 20 to 30 mmφ, so there is a limit to the use of SrTiO ₃ single crystal. Recently, the importance of higher crystal quality and larger diameter has been recognized, so that the CZ method, which is one of the melting and solidifying methods, is generally used instead of the immersion arc melting method or the Bernoulli method. We have reached the goal of using the CZ method to produce LaGaO ₃ , LaAl
O ₃ and NdGaO ₃ are grown. However, even with this CZ method, there are still problems to be solved. That is, using this CZ method, LaGaO ₃ and LaAl
When producing single crystals of O ₃ , these LaGaO ₃ and LaAlO
₃ has a phase transition point between room temperature and 1000 ° C. Therefore, when the temperature reaches the phase transition point when forming a high temperature oxide superconducting thin film or the like by the gas phase or liquid phase method, Twin crystals may occur in the single crystal due to the phase transition, and the compatibility between the high temperature oxide superconducting thin film and the single crystal may be impaired. Also,
When producing a NdGaO ₃ single crystal using this CZ method, NdGaO ₃
Although there are no twins in GaO _{3 due} to the phase transition, cracks are likely to occur in the NdGaO ₃ crystal, which may make growth difficult. As described above, in the conventional single crystal of the high-temperature oxide superconducting thin film substrate, the single crystal has an arbitrary diameter,
It has been extremely difficult to obtain a high-quality single crystal free from subgrains, twins, cracks and the like. This invention has been made in view of the above circumstances, eliminates the drawbacks of the conventional single crystal, it is possible to grow to an arbitrary diameter,
Furthermore, it is an object of the present invention to provide a high quality single crystal capable of forming a high temperature oxide superconducting thin film having good crystallinity as a substrate and a method for producing the same.

In order to solve the above problems, the present invention provides a terbium aluminate single crystal containing at least terbium, aluminum and oxygen. Further, the present invention also provides a manufacturing method characterized by growing the terbium aluminate single crystal by a melt solidification method.

In other words, according to the present invention, the conventional MgO, SrTi
Providing terbium aluminate single crystal instead of O ₃ , LaGO ₃ , LaAlO _3, NdGaO _3, etc., thereby providing high quality single crystal with arbitrary diameter useful as a substrate for high temperature oxide superconducting thin film It is possible. Further, in the present invention, Nd
By adding active elements such as ³ +, Cr ³ +, Ti ³ + and Ce ³ +, it is possible to provide the above single crystal useful as an oscillation material for a solid-state laser or the like. Furthermore, in the present invention,
The following formula

The preferred embodiment is a single crystal represented by the formula: or a single crystal thereof having no absorption peak in the visible region. When a single crystal is grown by melting and solidification, it is possible to reduce the growth atmosphere by using, for example, hydrogen or carbon monoxide, or a mixed gas of hydrogen or carbon monoxide mixed with a neutral gas such as nitrogen or argon. It is possible to control the valence of terbium, and as a result, it is possible to grow a colorless and transparent terbium aluminate single crystal which has few cracks due to strain and has no absorption in the visible region. Terbium oxide, which is a raw material for terbium aluminate single crystal, has a structure of Tb ₄ O ₇ (a mixture of Tb ³ + and Tb ⁴ +), and therefore terbium aluminate single crystal is grown in a neutral or oxidizing atmosphere. , Tb ⁴ + is easily incorporated into the crystal, which causes distortion and coloring. Therefore, the present invention provides very high quality and versatile single crystals. It is colorless and transparent, has little absorption in the visible region, and is useful as a material for laser hosts and the like. Of course, in addition to the CZ method, a FZ method, a Bernoulli method, an EFG method or the like may be used.
Hereinafter, the present invention will be described in detail with reference to examples.

Example 1 A single crystal was grown by the CZ method using high frequency induction heating. Terbium oxide and aluminum oxide in an atomic ratio of 1:
The mixture adjusted to 1 was placed in an iridium crucible, melted in a nitrogen + 20% hydrogen atmosphere, and grown by the CZ method. The growth conditions are pulling direction (001) and crystal rotation speed 20r.
About 50% of the charged weight was pulled up at pm and a pulling rate of 4.0 mm / hr to obtain a single crystal. The obtained crystal was free of cracks and twins, and had a size of 25 mmφ × 100 mm. The crystal was colorless and transparent, and no absorption peak was observed in the visible region. As a result of chemical analysis of this, the atomic ratio was Tb: Al = 1.0: 1.0. Example 2 Using terbium oxide, yttrium oxide, aluminum oxide and gallium oxide as raw materials, a mixture adjusted to have a pulling composition of (Tb _0.9 Y _0.1 ) (Al _0.9 Ga _0.1 ) O ₃ was placed in an iridium crucible. It was melted in a nitrogen + 5% CO atmosphere and grown by the CZ method. As the growth conditions, about 50% of the charged weight was pulled up at a pulling direction (001), a crystal rotation speed of 20 rpm, and a pulling rate of 4.0 mm / hr to obtain crystals. The crystals obtained are free of cracks and twins and have a size of 25.
The crystal of mmφ × 100 mm was colorless and transparent, and no absorption peak was observed in the visible region. As a result of chemical analysis of this, the chemical formula of the pulled crystal is (Tb _0.9 Y _0.1 ) (Al _0.9
Ga _0.1 ) O ₃ .

As described in detail above, according to the present invention, for example, the following excellent effects can be obtained. 1) There is no phase transition containing at least three elements of terbium, aluminum and oxygen, and therefore a high quality terbium aluminate single crystal is obtained. 2) A conventionally existing CZ method can be applied as a crystal growth method, and a high-quality terbium aluminate single crystal having an arbitrary shape is provided. 3) Suitable for forming a high temperature oxide superconducting thin film by liquid phase or vapor phase growth and controlling the lattice constant,
It can be adapted to the lattice constants of all kinds of high temperature oxide superconducting thin films, and is highly versatile as a substrate single crystal. 4) By performing the single crystal growth method in a reducing atmosphere, the valence of terbium can be controlled, and it can be used as a material in a versatile field such as a laser host that is colorless and transparent and has no absorption peak in the visible region. And

Claims (5)

[Claims] 1. At least terbium, aluminum,
And a terbium aluminate single crystal containing oxygen. 2. The terbium aluminate single crystal according to claim 1, which is represented by the following formula: 3. The terbium aluminate single crystal according to claim 1, wherein the single crystal has no absorption peak in the visible region. 4. A method for producing a terbium aluminate single crystal, which comprises growing the terbium aluminate single crystal according to claim 1 by a melt solidification method. 5. The method for producing a terbium aluminate single crystal according to claim 4, wherein the terbium aluminate single crystal is grown in a reducing atmosphere.