JPS63274682A - Preparation of oxide superconducting material - Google Patents

Abstract

PURPOSE:To maintain a stable superconducting characteristic even on or near the surface of an oxide superconducting material or in the inside thereof by adding a halogen element into the above-mentioned material and forming a film, then subjecting the material to a heat treatment. CONSTITUTION:The halogen element is added into the oxide superconducting material (e.g.: YBa2Cu3O6-8) to fill part or the whole of oxygen vacancy. The halogen element such as F element is added to the vacancy having some oxygen vacancy in particular and having the superconducting characteristic of the highest Tco (temp. at which electric resistance is zero) to fill the vacancy, by which the perovskite structure of the molecules is more stabilized. The film such as silicon nitride film is simultaneously formed on the surface of the oxide superconducting material and F is particularly added to the surface or near the same and the part thereof is heat-treated to dispose the added F in the adequate atomic configuration. In addition, the film is heat-treated to form the more complete blocking layer and the insulating film is denatured by oxidizing said film in the metal or semiconductor.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Application of the Invention The present invention relates to a method for producing an oxide superconducting (also referred to as superconducting, but hereinafter referred to as superconducting) material.

The present invention aims to improve the physical properties near the surface, which are particularly important in devices using the surface of an oxide superconducting material. Furthermore, the aim is to stabilize oxide superconducting materials that are intended to be applied to bulk (internal) superconducting magnets, etc., particularly with respect to oxygen vacancy.

"Prior Art" Recently, oxide superconducting materials have been attracting attention. This is IB
Ba-La-C made at M8M Zurich
Its origins lie in the development of u-0-based oxide superconducting materials. In addition, intoleum-based oxide superconducting materials are also known, and their potential for application in solid-state electronic devices at liquid nitrogen temperatures has become clear.

On the other hand, superconducting materials using metals such as NblGe are well known. Attempts have been made to construct solid-state electronic devices such as Josephson elements using this metallic superconducting material.

A Josephson element using this metal was almost ready for practical use after several years of research. However, this superconductor has T
ca c (temperature at which a low resistance atmosphere occurs) is extremely low at 23, necessitating the use of liquid helium, and is not sufficiently practical.

On the other hand, since this metallic superconducting material is made entirely of metal, it is possible to make the material components completely uniform both on the surface and in the interior (bulk).

``Conventional problems'' However, when examining the properties of oxide superconducting materials, which have been attracting attention recently, it was found that the properties near the surface (approximately 200 m depth from the surface) deteriorated (reliability) compared to the inside. It was found that a decrease in sexual performance is likely to occur.

It has been found that the reason for this is that oxygen in the oxide superconducting material is extremely easily degassed near the surface. Furthermore, when heated at 250 to 500°C in a vacuum, even the oxygen inside is easily degassed, causing more oxygen vacancy (a hole in which atoms at the atomic level are pulled out of their normal arrangement is called a void or vacancy). It turned out that it was. It has been found that whether this oxygen is in an ideal state or in a deficient state is a fundamental issue in determining whether a material can have superconducting properties or merely have normal conducting properties. .

For this reason, the present invention provides superconducting properties on or near the surface of this oxide superconducting material, as well as inside the material, and also has an ideal oxygen vacancy concentration, heat resistance, process resistance (vacuum resistance), etc. It was designed to be stable even when stored inside a container.

"Means for Solving the Problem" According to the present invention, a halogen element is added to an oxide superconducting material, and the halogen element is filled into part or all of the oxygen vacancy to offset it. In particular, by adding a halogen element such as fluorine to this vacancy and filling it with a certain degree of oxygen vacancy, which has the highest TCO superconducting property, it is possible for this molecule to make the vervskite structure more stable. It is. As a result, the present invention, which has heat resistance and process resistance and is particularly effective for thin film materials with a large surface area, simultaneously forms a film on the surface of the oxide superconducting material. Before or after this process, a halogen element, especially fluorine, is added to the surface or its vicinity by a method such as ion implantation or thermal oxidation, and the whole is heat-treated to arrange the added fluorine in an appropriate atomic arrangement. urge In addition, this film is subjected to heat treatment to form a more complete blocking layer, and in the case of a metal or semiconductor, this film is oxidized and transformed into an insulating film. Furthermore, by performing solid phase-solid phase diffusion (diffusion of oxygen from the solid coating into the other solid oxide superconducting material) of the oxygen in this coating, on or near the surface, -i, approximately 200 The aim is to optimize the oxygen concentration in areas up to the depth of a person.

The film used for this purpose may be an insulating film of silicon nitride, aluminum nitride, aluminum oxide, tantalum oxide, titanium oxide, or the like.

Further, as this film, a metal or a semiconductor which becomes an oxide insulating film after oxidation treatment can also be used. That is, metals include aluminum, titanium, tantalum, copper, valume, and intrium, and semiconductors include silicon and germanium. These can be converted into aluminum oxide, titanium oxide, tantalum oxide, copper oxide, barium oxide, and ifthurium oxide by oxidation.

Further, silicon may be replaced with silicon oxide, and germanium may be replaced with germanium oxide.

The present invention is effective for both oxide superconducting materials having a table left structure and those having a thin film structure. In particular, when these materials have a thin film structure, the oxidized erectile ft conductive material can be formed by screen printing,
It is formed using a sputtering method, an MBE (molecular beam epitaxial) method, a CvD (vapor phase reaction) method, a photo-CVO method, or the like.

As an example of the components of the oxide superconducting material, (AI-
X Bx)ycuzOi+(x=O~1.1~2.
0-4.0 preferably 2.5-3.5. z = 1~
4, preferably 1.5 to 3°5, W=4 to IO, preferably 6 to 8). A is Y (indolium),
Gu (gadolinium), Yb (ytterbium), Eu
(europium), Tb (terbium), Dy (dysprosium), Ho (holmium).

Er (erbium), Tm (thulium), Lu (lutetium).

Selected from Sc (scandium) or one or more of the other elements in Group A of the Periodic Table. B is Ra (radium), Ba (barium), and Sr (strontium).

It is selected from group IIa of the periodic table of elements Ca (calcium), Mg (magnesium), and Be (beryllium). In particular, (YBaz)CusOi~ is a specific example thereof. was used.

Further, as A, a rank nide element or an actinide element other than the above-mentioned elements in the periodic table of elements can be used.

In the present invention, a halogen element such as fluorine is added to the oxide superconducting material in an amount of 1/100 to 200 of the vacancy.
In addition to adding a concentration of χ to improve heat resistance and process resistance, we also added a deterioration prevention film (buffsivation film) to the surface of this material to prevent degassing of oxygen that should originally exist in the material. Let it form.

If the thickness of the insulating film is such that a tunnel current of 5 to 50 people can flow through it, another superconducting material can be disposed on the top surface of this insulating film to form a Joffson element.

Also, as a coating for pansivation, it costs 100 to 20,000.
It can be used as a film to prevent deterioration as it is human-thick.

That is, in the present invention, after a halogen element such as fluorine is also added to an oxide superconducting material, these are heat-treated in an inert gas, air, or oxygen at 250 to 500°C, for example, 500°C, for 2 to 50 hours, for example, 5 hours. give By doing so,
Fluorine added by ion implantation or oxygen added in addition to fluorine can be arranged in an appropriate coordination, and the surface can also be made into a stable superconducting material. The reason why the temperature is set at such a relatively low temperature is that at such a low temperature, deoxygenation occurs more easily than in the superconducting material, and fluorine is more likely to be disposed in the vacancy through which oxygen escapes.

As a result, when the temperature is maintained at liquid nitrogen temperature, the oxygen concentration on this surface can also be maintained at an ideal state. That is, a passivation film can be made.

``Effect'' As described above, it has been reported that the superconducting state disappears for unknown reasons near the surface of oxide superconducting materials (epsilon axis deterioration problem is eliminated, and the superconducting state on the surface can be effectively used stably for a long period of time. I can now do it.

Furthermore, by uniformly adding it to the inside, the superconducting properties previously obtained can be fixed.

Hyper? ! In terms of conductive properties, it is important that the TCO is higher and that it can be used at higher current densities. However, even if such sufficiently high TCO and current density are obtained, deterioration occurs due to being left in a vacuum or continuing to flow a large current. The halogen element shown in the present invention is used to an extent that offsets oxygen vacancy (1/1 of vacancy).
By adding a halogen element (at a concentration of 00 to 200x), it was possible to stabilize the TCO. In addition, the flow density was increased to over 1500 A/cm'', three times that without additives, and it was possible to preserve it.

As a result, it has become possible to operate devices using this surface, particularly Josephson elements, stably and with high reliability for a long period of time.

The present invention will be explained below with reference to the drawings.

"Example 1" FIG. 1 shows the manufacturing process of an example of the present invention and the relative characteristics of the oxygen concentration distribution related thereto.

In Figure 1 (A), YBa is an example of an oxide superconducting material.
zCu106~. shows. The copper content can be 3 or less. Tablet such superconducting materials.

The starting material (Fig. 1 (A) (1)) was formed by forming a monocrystalline or polycrystalline structure 7 on a sheet or thin film. When this was held in a vacuum device and the atmosphere was evacuated, its Oxygen near the surface (1°) is degassed, causing deterioration in electrical characteristics within the range of approximately 200 people.

That is, the oxygen concentration corresponding to FIG. 1(A) is shown in FIG. 1(D).
Shown below. In the figure, region (1) has a normal oxygen concentration. Further, the area (1゛) indicates an insufficient area. This depth depends on the type, structure, and density of the superconducting material, but
-1000 people, -m about 200 people.

A silicon nitride film is applied to the upper surfaces of these by a photo-CVO method (exciting a reactive gas using ultraviolet light or laser light to form a film on the surface to be formed) by 5 to 50 people, for example 20 people.
Formed to the thickness of a person. Furthermore, ion implantation was performed on this. The accelerating voltage was lowered to 10 to 30 KV, and oxygen was added to keep the oxygen concentration constant. Heat treatment at 350℃
I went there for 2 hours. Further, fluorine, which is a halogen element of the present invention, was doped with an acceleration voltage of 10 to 500 KV and an average doping concentration of 1/100 to 200x of the oxygen vacancy, for example, 3 XIO"cm.

Furthermore, the whole was heat-treated in oxygen at 250 to 500°C, for example, 350°C, for about 30 minutes.

By carrying out such heat treatment, fluorine enters the oxygen vacancy inside as well, as shown in FIG. 1(E).
We were able to make structural deterioration of the oxide superconducting material with the verbucite structure less likely to occur.

The sample prepared in this example was removed from the heated state and stored again in vacuum at 350°C for 5 hours.

The addition of fluorine prevented oxygen depletion near the surface and in the bulk of the superconducting material, making it possible to create a highly reliable device.

"Effects" As shown in the present invention, the surface of the produced oxide part':4 conductive material has extremely microscopic recesses when viewed under an electron microscope, and voids exist deep inside the recesses. Therefore, the upper surface appears to be extremely large.In order to passivate this surface, it is necessary to coat fluorine, which has the highest electronegativity, in a single layer or in a scattered manner to improve heat resistance. It was extremely effective. In addition, these surfaces and microscopic cavities can be filled with halogen elements. A method of modifying superconducting materials closely related to this has been extremely effective because it can simplify the manufacturing process.

As a result, the fluorine-added oxide superconducting material was left in vacuum at 300° C. for 5 hours. Oxide materials without fluorine have no superconducting properties at all. However, in the film to which fluorine was added according to the present invention, superconductivity was stably maintained at a TCO of 79.

In the present invention, the term oxide superconducting material is used. However, it is clear from the technical concept of the present invention that the crystal structure may be polycrystalline or single crystalline.

In the examples of the present invention, fluorine was shown as an example of the halogen element. However, iodine and bromine may also be added in the same way as fluorine.

Note that in the past, oxygen was injected into the superconducting material by ion implantation or the like after forming a film. However, on the contrary, oxygen is added to the surface of the superconducting material in advance by ion implantation, etc., then a film is formed, and then the added oxygen is heated and oxidized to form an atomic coordination suitable for forming superconductivity. It is also effective to place the

In the present invention, an example is shown in which fluorine is newly added to a material that has already been formed. However, when producing this superconducting material, fine grain materials of yttrium oxide, barium carbonate, and copper oxide are used for -m, and these are blended and fired repeatedly to form a table left. When forming a thin film, the tablet is used as a sputtering target to form a thin film on the surface to be formed. However, in such starting materials YFs,
YbFs.

Fluorine may be added in advance using TbF, LaF, in part or in whole. Also, instead of this fluoride, chloride,
Brominated compounds may also be used.

However, the idea of the present invention is to create the oxygen vacancy necessary to form superconductivity at the required temperature, and then add a halogen element to it.

Therefore, in order to increase the TCO, it is more preferable to add it after forming the oxide superconducting material.

[Brief explanation of the drawing]

FIG. 1 shows the manufacturing method of the present invention and the distribution of oxygen concentration. (A) CC) (E) Midori 11]

Claims (1)

[Claims] 1. A step of adding a halogen element to an oxide superconducting material, a step of forming a film on the oxide material before or after the step, and a step of performing heat treatment after the previous step. A method for producing an oxide superconducting material, characterized by having the following. 2. A method for producing an oxide superconducting material according to claim 1, characterized in that fluorine, which is a halogen element, is added by an ion implantation method. 3. In claim 1, the heat treatment is performed at a temperature of 250 to 250
A method for producing an oxide superconducting material, characterized in that it is carried out at a temperature of 500°C. 4. In claim 1, the oxide superconducting material has a sufficiently high T_C before adding a halogen element.
A method for producing an oxide superconducting material having _O or the highest current density, characterized by adding a halogen element to the oxide superconducting material.