JPS63310799A - Production of oxide superconducting crystal - Google Patents

Abstract

PURPOSE:To obtain a multicomponent oxide superconductor in the form of a bulk crystal of high quality by using kyropouls method. CONSTITUTION:A Pt heater 2 is arranged to the inside of an alumina shielding material 1 and a Pt crucible 3 is supported on a base 4 at the center of the Pt heater. The base 4 is integrated with a supporting rod 5 connected to the outside of a furnace and is revolvable. A thermocouple 6 is provided to the base and a flux comprising a liquid mixture consisting of, for example, BaCO3 and B2O3 is formed in the crucible 3. A soln. 7 contg. Y2O3 and CuO dissolved therein is formed. After allowing the soln. to stand at about 1,200-1,300 deg.C for about 10hr, the temp. of the soln. is set at about 900-1,000 deg.C by cooling, then, a seed crystal of YCuO single crystal attached to a tip of a pulling shaft 8 is dipped in the soln. 7 and the seed crystal is allowed to be accustomed to the soln. Thereafter, a crystal 9 is pulled up with a specified low cooling velocity. In this stage, gaseous O2 is fed through a pipe 12 to the surface of the soln. 7. By this method, a YBa2Cu3O7-delta crystal having good quality is prepd. at relatively low temp., accordingly, without causing phase transition.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for producing a multi-component oxide superconducting crystal.

(Prior Art) Recently, multi-component oxide superconductors with a perovskite structure have attracted attention as high-temperature superconductor materials that exhibit superconductivity at temperatures as high as liquid nitrogen temperatures. The typical oxide superconductor reported so far is YBa 2 Cu
3O7-4 and (La, Ba) 2 Cu 04
-y etc. These oxide superconducting materials can be produced using sintering methods,
It is obtained by a vapor deposition method, a sputtering method, etc.

When applying these oxide superconductors to specific devices in the future, it is necessary to maintain a high and stable superconducting transition temperature, obtain a large critical current, and achieve excellent uniformity and reliability of device characteristics. It is strongly desired to realize this as a single-crystal substrate or a single-crystal layer with a relatively large area. For manufacturing this type of oxide superconducting single crystal, it is possible to use the Czochralski method (CZ method) as in the case of dielectric oxide single crystals. However, in the CZ method using a crystalline material melt, crystal growth occurs at a very high temperature, and the oxide superconductor undergoes a phase transition, making it impossible to obtain the desired superconductor.

(Problems to be Solved by the Invention) As described above, when applying multi-component oxide superconducting materials to devices, it is desired to make them into single crystals, but the reality is that there is no method for this until now.

In view of the above-mentioned points, an object of the present invention is to provide a method for producing an oxide superconducting crystal that makes it possible to obtain a multi-component oxide superconductor as a high-quality bulk crystal.

[Structure of the Invention] (First Step for Solving the Problems) The method of the present invention comprises preparing an oxide mixture containing an oxide of at least one metal element among the constituent elements of a desired multi-component oxide superconductor. It is characterized by pulling a multi-component oxide superconducting crystal using a flux solution using the Kiporas method.

For example, to pull a Y Ba 2 Cu 3 O7-J crystal, a BaO-B 2 O 3 mixture is used as a flux. In this case, the atomic ratio is Ba/(Ba +B
) is about 0.2 to 0.5, then 1000
A liquid phase can be obtained at a relatively low temperature below ℃.

(Function) According to the present invention, by using the Kiporus method, CZ
Crystal growth is possible at a sufficiently lower temperature than in the conventional method, and phase transition of the superconductor is effectively prevented. Thereby, a desired oxide superconductor crystal bulk having good uniformity of superconducting transition temperature and large critical current can be obtained with good reproducibility. By using the oxide superconducting crystal obtained according to the present invention, various superconducting devices can be manufactured with good reproducibility.
become capable.

(Example) The present invention will be explained in detail below.

FIG. 1 shows an embodiment of a crystal pulling apparatus. In this example, YBa is used as the multi-component oxide superconducting crystal.
2 Pull up the Cu 3O7-a crystal. In FIG. 1, reference numeral 1 denotes an alumina shield material, in which a platinum heater 2 is placed, and a platinum crucible 3 is placed on a support base 4 at the center thereof. The support stand 4 is integrated with a support rod 5 connected to the outside of the furnace, and is rotatable. 6 is a thermocouple. In crucible 3, Ba CO3 B203 mixture 1
A flux consisting of Y203 (50 to 70 mol % of B203) is formed, and a solution 7 in which Y203 and CuO are dissolved is formed.

FIG. 2 is a phase diagram of the Ba0B, +03 system, and by selecting an appropriate molar ratio in this system, a liquid phase state can be obtained at about 900°C. Therefore, by using this system as a flux, YBa 2 Cu 3O-r
-a It is possible to obtain a solution for pulling crystals.

In this way, a desired solution 7 is formed in the crucible 3, and after being left at 1200 to 800°C for about 10 hours, the solution temperature is lowered and set to 900 to 1000°C.

Then, a Y attached to the tip of the pulling shaft 8 is added to this solution 7.
Seed crystals made of CuO1l crystals are immersed in the solution and thoroughly soaked in the seed crystals. After that, 0.1-0.5℃/h
The crystal 9 is pulled up at a low cooling rate. During this pulling, oxygen gas is supplied to the surface of the solution 7 via the gas introducing vibrator 12 at a rate of about 100 m/min. 10 is a light entrance window for internal observation, and 11 is an internal observation window.

In this way, according to this example, high-quality Y can be produced at a relatively low temperature, and therefore without phase transition, by the Kiporas method using a flux containing Ba, which is one of the constituent metal elements of YBa da Cu3O7-a.
It is also possible to pull Ba 2 Cu 3 O7-a crystals. In this example, by supplying oxygen gas during crystal pulling, it is possible to prevent the generation of oxygen defects in the solution and in the grown crystal.

Next, the thus obtained Y Ba 2 Cu 3 C) ta crystal was sliced to form a mirror-polished substrate, which was further coated with Y B
An example will be described in which an epitaxial wafer is formed in which an a 2 Cu 3 O7-6 crystal layer is grown by liquid phase growth.

The need for such epitaxial wafers is particularly
This occurs when the substrate crystal deviates from the desired composition and does not exhibit superconducting properties, or when uniform superconducting properties cannot be obtained within the city.

FIG. 3 shows the main structure of the liquid phase growth apparatus.

21 is a platinum crucible, in which Ba CO3-B
203 (20 to 50 mo1%) mixed solution is used as a flux, and a solution 22 is prepared by dissolving YCuO powder therein. Y
Ba 2 Cu 3O7-a crystal substrate 23 is supported by support rod 2
The substrate is held by a substrate holder 25 provided at the tip of the substrate 4 and brought into contact with the solution 22, and while rotating at a high speed of 50 to 100 rpm, liquid phase epitaxial growth is performed at a cooling rate of 0.1° C./h or less. 26 is a thermocouple.

As a result, as shown in FIG. 4, 20 to 3
An epitaxial wafer on which a uniform Y Ba 2 Cu 3 O 7-a single crystal layer 27 of 0 μm is formed is obtained.

FIG. 5 shows the wafer (2cjl) obtained in this way.
The superconducting transition temperature of the Y Ba 2 Cu 3 O□-a crystal layer of Φ) is shown at all five points in the radial direction. It can be seen that the temperatures at which the electrical resistance is zero are within the range of 30 to 38 at all five points, and that superconducting epitaxial wafers with excellent uniformity have been obtained.

In the above example, Ba CO3-B203 mixed liquid was used as the flux, but BaO-B2O3 mixed liquid, HBaO-B2O3 mixed liquid, B203-Ba B20
A BaO-B2O3-based flux such as a 4 11Na 20 mixed solution can be used. Further, in the above embodiment, the case where Y Ba 2 Cu 3 O 7-4 crystal was pulled was explained, but instead of Y, Yb, Ho, Dy, and Eu were used.

Er, Tll1. The present invention is also effective when other rare earth elements such as Lu are included;
-0 system, Sr -La -Cu-0 system, and further S
The present invention is also effective in producing multi-component oxide superconducting crystals having other perovskite structures, such as those substituted with , Ca, or the like.

The pond water invention can be implemented with various modifications without departing from the spirit thereof.

[Effects of the Invention] As described above, according to the present invention, a multi-component oxide is produced by the Kiporas method using as a flux an oxide mixture containing at least one metal element among the constituent elements of a desired oxide superconductor. Bulk crystals of superconductors can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a Y Ba 2 Cu 3 Ot-a crystal pulling apparatus according to an embodiment of the present invention, FIG. 2 is a phase diagram of Ba 0-B2o3 system, and FIG. 3 is a diagram showing a Y Ba 2 Cu 3 Oy-a crystal pulling apparatus. A diagram for explaining the epitaxial growth method of crystals, Figure 4 shows the obtained YBa
FIG. 5 is a diagram showing an epitaxial wafer of 2Cu 3O7-J crystal, and FIG. 5 is a diagram showing the results of measuring the superconducting transition temperature distribution of the epitaxial wafer. 1... Alumina shield material, 2... Platinum heater,
3... Platinum crucible, 4... Support stand, 5... Support rod, 6... Thermocouple, 7... Solution, 8... Pulling shaft, 9... Y Ba 2 Cu 3O7 -a crystal, 10... light irradiation window for internal observation, 11... internal observation window, 12... gas introduction vibrator, 21...
Platinum crucible, 2...solution, 23-...YBa 2
Cu 3O f-a crystal group number, 24-... support rod, 2
5... Holder, 26... Thermocouple, 2701. YB
a2Cu3O7-a crystal layer. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 4 17 (K) Figure 5

Claims (4)

[Claims] (1) A multi-component oxide superconducting crystal is pulled by the Kiporas method using a solution containing an oxide mixture containing an oxide of at least one metal element among the constituent elements of the desired multi-component oxide superconductor as a flux. A method for producing an oxide superconducting crystal characterized by (2) The multi-component oxide superconductor is ABa_2Cu_3O_7_-_δ (A is Y, Yb,
2. The method for producing an oxide superconducting crystal according to claim 1, wherein the flux is a BaO-B_2O_3-based mixed liquid. (3) The multi-component oxide superconductor is ABa_2Cu_3O_7_-_δ (A is Y, Yb,
(one selected from Ho, Dy, Eu, Er, Tm, and Lu), the flux is a BaO-B_2O_3-based mixed liquid, and the composition of the flux is Ba/B_2O_3 in atomic ratio.
The method for producing an oxide superconducting crystal according to claim 1, wherein (Ba+B) is 0.2 or more and 0.5 or less. (4) When pulling the multi-component oxide superconductor crystal,
The method for producing an oxide superconducting crystal according to claim 1, wherein oxygen gas is supplied near the surface of the solution.