JPH01239054A - Production of oxide superconductor - Google Patents

Abstract

PURPOSE:To readily produce a wire or filmy molded item having excellent superconducting properties, by quenching with forming after melting of a raw material to obtain amorphous state and heat-treating, in a production of a superconductor of Bi-Sr-Ca-Cu-O based oxide. CONSTITUTION:Respective compounds of Bi, Sr, Ca and Cu are molten at least 900 deg.C to obtain a melt composed of Bi, Sr, Ca, Cu and O. Obtained melt is quenched, with forming to a fixed shape, to an amorphous molded item, then the molded item is heat-treated at 600-880 deg.C to impart superconducting properties together with crystallization. By the method, raw materials are readily formed to various shape such as a wire or a filmy molded item and crystallite size is controlled by changing of heat-treating condition, a fine and dense texture is obtainable and an oxide superconductor having excellent superconducting properties.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for producing a Bj-Sr-Ca-Cu-0-based superconductor, which has particularly excellent formability, is dense, and has superconducting properties. This invention relates to a method for producing an excellent oxide superconductor.

(Prior Art) In recent years, oxide superconductors with high critical temperatures that exhibit superconductivity even at liquid nitrogen temperatures have been discovered, and this has had a great impact on industry. A typical example is Y-Ha-
Cu-0 based oxide superconductors are well known. In other words, although this oxide superconductor has a high critical temperature of -183°C (90K), it is not resistant to atmospheric moisture or carbon dioxide gas, and is extremely unstable in the environment, making it difficult to put into practical use. In addition, the proportion of oxygen components varies greatly depending on the manufacturing conditions, and the superconducting properties change accordingly, so it is necessary to strictly control the manufacturing conditions in order to obtain a desired result.

Furthermore, in order to put oxide superconductors into practical use, it is extremely important to easily produce molded products such as wire rods and films. By the way, as a method for producing molded products such as wires and films made of the Y-Ba-Cu-Q based oxide superconductor mentioned above, there is a sintering method in which powdered products of this oxide superconductor are fired. It has been known. However, since the sintering method has poor moldability, it has been difficult to obtain molded products such as wire rods and membranes.

Near the mountain pass, a new type of high temperature that does not contain rare earth elements (90
-105 grade) Bi-Sr-Ca-C as a superconductor
A u-0 based oxide superconductor has been reported (see Solid State Physics Vol. 23 (1988) March issue, pp. 34-35). This oxide has excellent stability against atmospheric moisture, carbon dioxide, etc., has a constant oxygen content, and has stable superconducting properties.

However, this oxide superconductor, for example, Y-Ba-
Compared to Cu-0-based oxide superconductors, it has stronger anisotropy and tends to form mica-like crystals, so it is difficult to obtain wire rods or film-like molded products with excellent superconducting properties by firing oxide powder. This is extremely difficult.

(Problems to be Solved by the Invention) As a result of various studies to obtain molded products such as wire rods and films made of Bi-Sr-Ca-Cu-0 based oxide superconductors, the present inventors have discovered the present invention. The object of the present invention is to obtain a 1-Sr-Ca-
An object of the present invention is to provide a method for easily manufacturing a Cu-0 based oxide superconductor.

(Means for Solving the Problems) That is, the present invention provides a method for producing a Bi-3r-Ca-Cu-0 based oxide superconductor in which a bismuth compound, a strontium compound, a calcium compound and a copper compound are
The product is melted at a temperature of 00°C or higher to form a melt consisting of bismuth, strontium, calcium, copper and oxygen, and the resulting melt is rapidly cooled while shaping into a predetermined shape to form an amorphous molded product. The molded product is heated to 600 to 88
This is a method for producing an oxide superconductor, characterized by crystallizing it by heat treatment in a temperature range of 0°C.

Bismuth compounds, strontium compounds, calcium compounds, and copper compounds in the present invention refer to oxides, hydroxides, chlorides, carbonates, nitrates, etc. containing the respective elements, which are usually used when manufacturing oxide superconductors. Any compound of each element to be used may be used, but bismuth oxide (Bi203) and strontium carbonate (SrC) are particularly suitable.
Oa), calcium carbonate (CaCO,) and copper oxide (
Cub) is preferably used, and these compounds have a raw material composition ratio of, for example, Bi:Sr:Ca:Cu
=1:1:1:2 or 2:(3-X):X:2(X
are mixed at a ratio such that the ratio is 0.4 to 0.9). The melting conditions include heating to a temperature of 900° C. or higher. The crucible used for melting is alumina,
Zirconia, platinum, gold, etc. can be used, and gold is preferable.

Next, the obtained melt is quenched while being shaped into a predetermined shape, but the quenching conditions are not particularly stipulated, and the melt may simply flow out into the air or into water.
At that time, it is necessary to shape it into a predetermined shape. For example, wire rods can be obtained by extruding the molten material through a nozzle into air or water, as well as films and ribbons.

A tape or film-like product can be obtained by pouring it onto a plate or roller surface, or by pouring it out between the nip of a twin roller. The molded product thus obtained is amorphous and is a type of insulator having a high electrical resistance value.

This amorphous molded body is heat-treated to precipitate superconducting crystals to form a molded product made of an oxide superconductor. The heat treatment conditions are 600 to 8 in air.
Crystallization can be performed by heating in a temperature range of 80° C. and then allowing it to cool. If the temperature range is below 600℃, the crystals cannot be fully separated and the amorphous remains, resulting in poor superconducting properties.On the other hand, if the temperature is above 880℃, the molded product will soften and melt, making it difficult to maintain its shape. It needs to be in range.

By appropriately changing the heat treatment conditions, it is possible to adjust the crystal size, make it finer and denser, and improve the superconducting properties.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Examples of raw material compounds include Bi, 0. ．． SrC03, CaCO
3 and CuO, the composition ratio of the raw materials is Bi:Sr:Ca:Cu
= 1:1:1:2 ratio. After mixing uniformly, place in an alumina crucible and heat at 950℃ in air.
Melts at a temperature of This melt was poured onto a quartz plate and rapidly cooled to obtain a plate-shaped molded product. This plate-shaped molded product had a blackish brown color, was amorphous, and was an insulator. The X-ray diffraction pattern of this product is shown in FIG. Next, this material is subjected to heat treatment. The heat treatment conditions include heating at 800° C. in air for 24 hours, and then cooling to crystallize. The X-ray analysis pattern is shown in FIG. When the electrical resistance value of this crystallized plate-shaped compact with respect to temperature was examined, it was found that it had superconducting properties as shown in FIG.

(Effect of the invention) As described above, the present invention provides Bi-Sr-Ca-Cu-
When manufacturing molded products made of 0-based oxide superconductors,
Since it is a melting method in which raw materials are melted and then molded, it is easy to mold them into various shapes such as wire rods and film-like materials.

-Turn it into an amorphous state by rapidly cooling it after melting,
By heat-treating it, it crystallizes and imparts superconducting properties, so the crystal size can be controlled by freely changing the heat-treating conditions, making it possible to make it finer and more dense, resulting in extremely good oxidation properties with superconducting properties. This produces effects such as obtaining a physical superconductor.

[Brief explanation of the drawing]

FIG. 1 shows Bx, , Sr1? according to the present invention. cal,
Figure 2 shows the X-ray diffraction pattern of a rapidly cooled Cu2tox melt; Figure 2 shows the X-ray diffraction pattern of a crystallized product obtained by heat-treating the substance; Figure 3 shows its superconducting properties. be.

Claims (1)

[Claims] In the method for producing a Bi-Sr-Ca-Cu-O based oxide superconductor, a bismuth compound, a strontium compound,
A calcium compound and a copper compound are melted at a temperature of 900°C or higher to form a molten material consisting of bismuth, strontium, calcium, copper, and oxygen, and the resulting molten material is shaped into a predetermined shape and rapidly cooled to form an amorphous state. 1. A method for producing an oxide superconductor, the method comprising: forming a molded article;