JPS63303846A - Production of superconducting material - Google Patents

Abstract

PURPOSE:To obtain an extremely dense ceramic superconducting material in a short time and at low cost by pulverizing a calcined material contg. a group IIIa element, a group IIa element, and Cu, adding elementary halogen to said powder, and molding to a specified shape and heating the molded product. CONSTITUTION:A starting material consisting of a compd. of a group IIIa element (e.g. Yb2O5), a compd. of a group IIa element (e.g. BaCO3), and a Cu compd. (e.g. CuO) is calcined in oxidizing atmosphere such as atmospheric air. Fine powder having <=10mum mean particle radius is obtd. by pulverizing obtd. oxide. Then, said elementary halogen is added to said fine powder by exposing said fine powder to a liquid or gas contg. the elementary halogen such as F, and the treated powder is compression molded. During the compres sion molding, the material is oxidized at 500-1,000 deg.C, for example, 750 deg.C, in oxidizing atmosphere such as atmospheric air to obtain thus an oxide supercon ductor contg. elementary halogen.

Description

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

"Conventional technology" Conventionally, superconducting materials include elements such as mercury and lead, and NbN.

Alloys such as Nb3Ge+ Nb3Ga or Nb5(Al
Metal compounds such as e, aGeo, z) are used. However, the Tc (superconducting critical temperature) of these was up to 25K.

On the other hand, ceramic-based superconducting materials have attracted attention in recent years. This material was first obtained from IBM's Zurich laboratory.
It has been reported as an a-La-Cu-0 (baraquo)-based oxide high temperature superconductor, and has been further known as LSCO (cupric acid-lanthanum strontium).

``Conventional problems'' However, the possibility of superconductivity in these oxide ceramics is based on the vervskite structure, and its T
The limit for c was also 30K.

For this reason, there has been a strong demand to further increase Tc and Tco and to operate at the desired liquid nitrogen temperature (77K) or higher.

"Means to Solve the Problem" The present invention sought a new type of material that would exhibit superconductivity at such high temperatures. As a result, Tc (the temperature at which superconductivity begins) is also 100-260K.

It has become clear that the temperature at which the electrical resistance becomes zero can be increased to 90 to 260K.

The superconducting oxide material of the present invention is (AI-X Bx)yc
uzOwX=O~Ly=2.0~4.0 preferably 2.5~3.5゜z=LO~4.0 preferably 1.5
~3.5. W=4.0 to 10.0, preferably 6 to 8, which can generally be expressed. A is the periodic table of elements, so-called m
One or more elements in group a, B is Ba
The element is selected from one or more elements of group IIa in the periodic table of elements, such as (valium) or strontium (Sr).

In the present invention, A is a material of the above-mentioned ma group, especially intrum group (Eu, Gd, Tb, Dy, Ho,
Er.

Tm, Yb1Lu, 5CIY) are used.

The present invention is characterized by a so-called hot press method in which starting materials such as halides, oxides, or carbonates are mixed and heated and pressed. Furthermore, in the present invention, pressure is applied once and temporary firing is performed. This is further pulverized. This fine powder is exposed to a liquid or gas containing a halogen element, such as fluorine or chlorine, and the halogen element is added into the powder. After that, it is pressurized again to form a tablet, and the final firing is performed.

At this time, there is a step of pressurizing at the same time.

In the general formula of the present invention, preferably expressed as )l
The value of +)'+L- is generally a distribution that makes it easy to adjust the components.

The present invention is a patent application filed by the inventor entitled "Method for producing superconducting ceramics" (Patent application filed on March 25, 1986).
2-072486) was further improved, and its Tco was greatly improved by adding a halogen element to the oxygen vacancy.

"Operation" The new type of acid/arsenic superconducting material of the present invention can be made very easily. In particular, these 3
By using an oxide with a purity of N or 4N, grinding it into a fine powder using a ball mill, and mixing it, it becomes stoichiometrically (At
-XBx)ycuzow's X+y+ZIW values can be arbitrarily changed and controlled.

Another feature of the present invention is that it does not require the use of particularly expensive equipment to produce such superconducting materials.

The present invention will be described below with reference to Examples.

"Example 1" As an example of the present invention, Yb was used as A and Ba was used as B.

The starting material is ytterdium oxide (Y
b205), BaC03 was used as the Ba compound and CuO was used as the copper compound. These were obtained from Kojundo Kagaku Kogyo Co., Ltd. and used as fine powders with a purity of 99.95χ or higher. Furthermore, x = 0.67 (A:B = 1:2
), y=3. I chose z = 3 and w = 6 to 8 as much as possible.

Mix these thoroughly in a mortar and seal in capsules, weighing 30kg.
/cm” load to make it into a tablet (size 10a+
-φ×3111I11). Further, in an oxidizing atmosphere, e.g. air at 500-1000°C, e.g. 800°C at 700°C.
Heat oxidation was performed for a period of time. This step was called pre-firing.

This was then ground and mixed in a mortar. The average powder radius of the powder was adjusted to be 10 μm or less, preferably 0.5 μm or less.

To add a halogen element such as fluorine to this fine powder, it was immersed in a solution of ammonium fluoride dissolved in a fluorocarbon solution. At this time, pressurize to about 2 atmospheres, and then pressurize to about 2 atmospheres.
When heated to about 00°C, fluorine is easily impregnated into the material, particularly into the oxygen vacancy. Then, the fluorine in the CFC and the fluorine in the ammonium fluoride were able to be impregnated into the surface and inside of the fine powder.

Furthermore, this is enclosed in a capsule and the amount is 10~3000Kg/c.
Oxidize in an oxide atmosphere, for example, air, at 500 to 1000°C, for example, 750°C, while applying a pressure of, for example, 50 Kg/cm (Talev), and carry out main firing for 1 to 10 hours.
For example, a so-called hot press method was used in which the process was carried out for 2 hours and then slowly cooled.

This tablet mainly has a vervskite structure, but other new structures were also observed at the same time.

Next, this sample was heated in 0z-Ar with reduced oxygen (600-1100°C, 3-30 hours, e.g. 750°C).
, 20 hours) for reduction. At this time, do not apply pressure.
Rather, it is preferable to use atmospheric pressure or reduced pressure in order to increase Tco. Then, the new structure became more clearly observed.

Using this sample, the relationship between resistivity and temperature was investigated. Then Tc on cent becomes 230, Tco becomes 2
25K could be observed.

When the pressurizing step and the subsequent heating step were performed without adding fluorine, which is the halogen element of the present invention, the Tc onset was 981 and the Tco was 91. Therefore, fluorine is considered to have a great effect on increasing Tco.

"Example 2" In this example, Y and yb were used as A in a ratio of 1:1. Moreover, Ba was used as B. Starting material is YF
3. YbF3 was used, BaCO3 was used as Ba, and CuO was used as the copper compound. The rest is the same as in Example 1.

235 as Tc on cent, 231 as Tco
I was able to get K.

"Example 3" In Example 1, YF was used as A. Further, after being once pulverized, this fine powder was exposed to hydrogen fluoride gas. This atmosphere was maintained at 300° C. and a pressure of 50 kg/c for 3 hours. Furthermore, as shown in Example 1,
I turned it into a tablet left again.

As a result, the Tc onset could be further improved by 3 to 5″x.

In the present invention, intrum family (E u + G
a + Tb.

oY, Hd, Er+ Tm, yb, Lu, S
Using the element c, V) as a fluoride as a starting material,
A composite oxide material is particularly effective in increasing Tco. In particular, materials selected from these (AI-X
Bx) Adding a monovalent halogen element such as fluorine, chlorine, bromine, or iodine to this position in order to fill the vacancy of the general formula 0 represented by ycuzow is also effective in greatly increasing the critical current. there were.

"Example 4" This example is a modification of Example 3, but an element of the yttrium group, such as Y, was added as an oxide. However, these were dissolved in an excess sulfuric acid potassium solution as double salts of the R, (Sol) and zsOa (R is yttrium element) type, and this was added to the pre-calcined powder used in Example 1 to produce the present invention. The halogen element shown in was added to the vacancy position. Furthermore, after this, main firing was performed in the same manner as in Example 1. Then, in this method of adding the solution after pre-calcination, the amount added can be precisely controlled. As a result, Tc could be further improved by up to 8 compared to Example 1.

"Effects" The present invention has made it possible to produce ceramic superconductors extremely precisely and in a short time, which was previously considered impossible.

Furthermore, by adding a halogen element to the position of the oxygen vacancy, it has become possible to increase (improve) Tco and also improve the critical current density.

In addition, the oxide superconducting material represented by the molecular formula of the present invention has a layered structure in which the copper oxide has a layered structure, and the layered structure also has a one-layer or two-layer structure within one molecule, as the presumed mechanism of superconductivity. It is presumed that carriers are superconducting within this layer.

An embodiment of the present invention is made into a tablet. However, instead of making a table left, the powder after preliminary firing or main firing is dissolved in a solvent containing fluorine, the solution is coated on a substrate, etc., and this is fired in an oxidizing atmosphere containing a halogen element. Furthermore, by performing main firing in a reducing atmosphere after that, it is possible to obtain a thin film of oxide superconducting material.

The present invention has made it possible to easily produce superconductors at low cost.

Claims (1)

[Claims] 1. A material containing elements Group IIIa, Group IIa, and copper of the periodic table is heated and fired to transform it into an oxide superconducting material and then powdered;
After exposing the powder to a liquid or gas containing a halogen element and adding the halogen element into the powder, the oxide material is shaped into a predetermined shape, or heat-treated while being shaped, thereby forming an oxide containing a halogen element. 1. A method for producing a superconducting material, the method comprising forming a superconducting material. 2. A method for producing a superconducting material according to claim 1, wherein the liquid containing a halogen element contains hydrogen fluoride, ammonium fluoride, or fluorocarbon. 3. A method for producing a superconducting material according to claim 1, wherein the gas containing a halogen element contains nitrogen fluoride, fluorine, and hydrogen fluoride.