JPS63288943A - Production of superconducting material - Google Patents

Abstract

PURPOSE:To produce a superconducting material having high critical temp., high purity, and uniform compsn. by exposing a molded body of fluorides of constituting elements of a superconducting material to oxidizing atmosphere and forming a specified compound oxide on the surface of the molded body. CONSTITUTION:Each fluoride or compound fluoride 3 of (A) >=one element selected from the group IIa of the periodic table, (B) >=one element selected from the group IIIa of the periodic table, and (C) >=one element of the groups Ib, IIb, IIIb, IVb, and VIIIa of the periodic table is charged to a crucible 2 mounted in a heating furnace 1. After melting and mixing the charged materials, the materials are poured into a mold 4 and cooled by allowing to stand to obtain thus a molded body of compound fluoride 3. The molded body 3 is then held in a vessel 6 mounted in a heating furnace 1 and melted by heating. The melt is extruded through a nozzle 5, then exposed to oxidizing atmosphere. Thus a compound oxide expressed by the formula (wherein 1<=w; x<=5; 1<=y<=15; 1<=z<=20) is formed on at least the surface of the molded body.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a novel production method that allows continuous production of superconducting materials with a high superconducting critical temperature.

Conventional technology Under superconducting phenomena, materials exhibit complete diamagnetic properties, and no potential difference appears even though a finite steady-state current flows inside them. Therefore, various applications of superconductors as transmission media with no power loss have been proposed.

That is, its application fields include power fields such as MHD generation, power transmission, and power storage, power fields such as magnetic levitation trains and electromagnetic propulsion ships, and NMR as ultra-sensitive sensors for magnetic fields, microwaves, radiation, etc. .

There are many fields that can be mentioned, such as pi-meson therapy, measurement fields such as high-energy physics experimental equipment, etc.

Furthermore, in the field of electronics, typified by Josephson devices, this technology is expected to not only reduce power consumption but also realize devices that operate at extremely high speeds.

By the way, superconductivity was once a phenomenon observed only at extremely low temperatures. That is, Nb3, which is said to have the highest superconducting critical temperature Tc among conventional superconducting materials,
Even in Ge, an extremely low temperature of 23.2 K was considered to be the limit of superconducting critical temperature for a long time.

Therefore, conventionally, in order to realize the superconducting phenomenon, superconducting materials have been cooled to below Tc using liquid helium with a boiling point of 4.2. However, the use of liquid helium imposes an extremely large technical burden and cost burden due to cooling equipment including liquefaction equipment, which has hindered the practical application of superconducting technology.

However, in recent years, it has been reported that sintered bodies containing oxides of La group elements or IIIa group elements can become superconductors at extremely high Tc, and the practical application of superconducting technology using non-low-temperature superconductors has suddenly begun. is about to be promoted. In the examples that have already been reported, it is thought that they have a crystal structure similar to that of perovskite oxides (La, Ba)
2CUO4 or [sha.

Examples include complex oxides such as Sr]2cuo<. In these materials, a significantly higher Tc than conventional ones of 30 to 50 was observed, and furthermore, oxides of Ba and ySCu, which are thought to have a so-called pseudo-perovskite crystal structure such as an orthorhombic structure, were observed. It has also been reported that sintered bodies have a Tc of 70 or more.

If materials that exhibit superconductivity at such high temperatures are used, it is possible to use cooling media such as liquid hydrogen, liquid nitrogen, etc., which are easy to use and inexpensive, which reduces the technical and cost savings for cooling. It becomes possible to utilize the superconducting phenomenon without any burden.

Problems to be Solved by the Invention However, as mentioned above, materials that exhibit superconductivity at liquid nitrogen temperatures are currently obtained as sintered bodies, which have extremely poor properties in terms of workability and mechanical strength. are doing. Therefore, it is virtually impossible to create a member with a complicated shape.

Also, when considered as a transmission medium for electric power or current,
It is essential to process superconducting materials into long materials such as wire rods or tape materials, but the materials mentioned above cannot withstand processes such as side-bottom wire drawing, which poses a major challenge in the practical application of superconducting technology. ing.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a novel manufacturing method capable of solving the problems of the prior art described above and industrially manufacturing a composite oxide superconducting material having a high Tc.

A means for solving the problem, that is, according to the present invention, an element α which is one or more types selected from Group IIa of the Periodic Table, an element β which is one or more types selected from Group IIa of the Periodic Table, Periodic table Ib.

The respective fluorides or composite fluorides with one or more elements T selected from groups I[b, II[b, IVa and VIIIa are melted and mixed, then molded, and the molded product is placed in an oxidizing atmosphere. By exposing at least the surface of the molded body to the general formula: Aw B)l CuyOz (where element A is an element selected from group IIa of the periodic table, and element B is an element selected from group IIIa of the periodic table). One selected element, element C is Ib, IIb of the periodic table.
, Ib, and one type of element selected from the VIIIa group, and w, x, and yXz are each 1≦W≦5.1≦X≦5, ■
A method for manufacturing a superconducting material is provided, which is characterized by forming a composite oxide having the following formula: ≦y≦15, ■≦2≦20.

Function The method for manufacturing a superconducting material according to the present invention is characterized in that the superconducting material is formed by casting. That is, by once melting the raw materials, uniform mixing and free molding are achieved.

According to a feature of the present invention, a fluoride or composite fluoride of an element forming a superconducting material is used as the raw material. this is,
■A group, IIIa group, Ib group, ■ forming superconducting materials
The oxides of each element of group b, group b, group IVa, and group VIIIa have extremely high melting points, so when these are melted and mixed, metal elements with relatively low melting points, oxygen, etc. are volatilized. This is because the composition of the product changes. In this regard, fluorides of these elements generally have a low melting point, making it possible to effectively control the composition.

In addition, various casting techniques such as a method using a mold or a method of extruding from a nozzle can be applied to molding the raw material melt.

By placing the formed body of the constituent element fluoride of the superconducting material thus formed in an oxidizing atmosphere such as oxygen gas, the general formula: Aw Bll Cu, Ox (however, element A
is an element selected from group na of the periodic table, element B is an element selected from group 1a of the periodic table, and element C is an element selected from group 1a of the periodic table, and element C is an element selected from group 1a of the periodic table. w, xSy, and z are each an element selected from the group 1≦W≦5.1≦X≦5.1≦y≦15.1≦2≦
A composite oxide superconductor represented by the following formula (a number satisfying 20) can be formed on the surface of the molded body. In addition, in this step, it is also preferable to heat the material in order to promote the reaction of oxygen.

The present invention will be described in more detail with reference to examples below, but what is disclosed below is only one example of the present invention and does not limit the technical scope of the present invention in any way. In the following description, the superconducting critical temperature is Tc, and the phase transition end temperature at which the electrical resistance of the superconductor becomes completely zero is Tc.
The difference between i, Tc and Tci is indicated as ΔT.

Embodiment FIGS. 1(a) and 2) are diagrams for supplementary explanation of the operation of this embodiment.

2 mo each of BaFSYFs and Cu F 2 powders
The raw material fluoride 3 was mixed at a ratio of 1 mol: 3 mol, placed in a carbon crucible 2 placed in a heating furnace 1, and heated to 1000°C, as shown in Figure 1(a). After melting, this was maintained and stirred for 30 minutes. Subsequently, this fluoride melt was poured into a cylindrical mold 4 coated with Au, as shown in Fig. 1 et al., and allowed to cool.

The composite fluoride rod 3 thus obtained was placed in a container 6 equipped with a nozzle 5 placed in a heating furnace 1, and heated to 900°C.
After heating, the wire was extruded through a nozzle 5 with a diameter Q of 2 mm to obtain a wire rod. Note that the nozzle 5 was protected by a N2 gas stream for cooling.

Furthermore, while exposing the wire thus obtained to 02 gas, 9
The mixture was heated to 50°C and reacted for 12 hours.

A 30 cm piece of the obtained wire was cut and used as a sample to measure the critical temperature Tc and Tci. The measurement was carried out by attaching electrodes with Ag conductive paste to both ends of the sample according to the standard method, and after cooling it to 50K in a Tarabiostat and confirming that the electrical resistance was completely zero, the resistance was increased while gradually increasing the temperature. The change in was measured. Resistance measurement was performed using a DC four-point probe method, and temperature was measured using a calibrated Au(Fe)-Ag thermocouple.

As a result of measurement, the above-mentioned wire showed a Tc of 109 and a Tci of 81.

Also, heated to 900℃? Judging from the results of thermogravimetric measurements conducted in H2 gas, this wire has a depth of approximately 10 mm from the surface.
It is thought that the composite oxide is formed up to μm.

Effects of the Invention As described in detail above, the method for manufacturing a superconducting material according to the present invention is capable of forming a superconducting material having a high critical temperature into a free shape due to its characteristic method of manufacturing by casting.

Further, by supplying the raw material as a fluoride, casting can be performed at a relatively low temperature, so that contamination of the superconducting material due to volatilization of metal elements or melting of the crucible, mold, etc. is reduced. Therefore, 1. A high-quality superconducting material with a uniform composition and few impurities can be obtained.

Furthermore, since the constituent elements are mixed in a liquid phase state, a member with a uniform composition and high density can be obtained.

Such a method of the present invention can be applied in a wide range of ways, not only for manufacturing wire rods and plate materials, but also for manufacturing magnetic shielding materials and the like.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) and FIG. 2 are diagrams for explaining the present invention in detail, and schematically depict the operations in each step. [Main reference numbers] 1... Heating furnace, 2... Carbon crucible, 3... Fluoride raw material (rod), 4... Mold, 5... Nozzle, 6... Container

Claims (5)

[Claims] (1) Element α, which is one or more elements selected from Group IIa of the Periodic Table, element β, which is one or more elements selected from Group IIIa of the Periodic Table, and Ib, IIb, IIIb, and IVa of the Periodic Table. and
The respective fluorides or composite fluorides with one or more elements γ selected from group VIIIa are melted and mixed, then molded, and the molded product is exposed to an oxidizing atmosphere to improve at least the surface of the molded product. General formula: A_wB_xCu_yO_z (However, element A is an element selected from group IIa of the periodic table, element B is an element selected from group IIIa of the periodic table, and element C is an element selected from group IIIa of the periodic table. Table Ib, IIb, II
One type of element selected from groups Ib and VIIIa w, x
, y, and z are respectively 1≦w≦5, 1≦x≦5, 1≦y≦
15. A method for producing a superconducting material, which comprises forming a composite oxide represented by the formula (a number satisfying 1≦z≦20). (2) The method for manufacturing a superconducting material according to claim 1, wherein in the oxidation step, the molded body is heated. (3) The element α is Ba, the element β is Y, and the element γ is Cu according to any one of claims 1 to 3. Continuous manufacturing method for superconducting materials. (4) The element α is Ba, the element β is La, and the element γ is Cu. Method for manufacturing superconducting materials. (5) The element α is Sr, the element β is La, and the element γ is Cu. Method for manufacturing superconducting materials.