JPH01131087A - Production of superconducting substance - Google Patents

Abstract

PURPOSE:To produce a superconducting substance resistant to the deterioration of characteristics while preventing the reaction of a sintered material with water, by coating a calcined material and/or sintered material of a prescribed mixed raw material powder with a water-proofing material. CONSTITUTION:A mixed raw material powder is prepared by mixing Y2O3, BaCO3 and CuO or La2O3, SrCO3 or BaCO3 and CuO in wet state at a ratio to give a composition of Y, Ba and Cu falling within the hatched range of the figure. The mixed raw material powder is compression molded, dried at <=150 deg.C and calcined at <=800 deg.C for 6-48hr. The calcined material is pulverized in wet state in the presence of an alcoholic liquid and sintered under compression-molding to obtain a superconducting substance composed of the sintered material. The calcined material and/or the sintered material are coated with a water-proofing material composed of an organic material (e.g., PVC) or a metallic material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing superconducting materials, and more particularly to improvements in conventional methods for producing superconducting materials.

[Conventional technology and its problems]

As is well known, new research on superconducting materials is currently being actively conducted, and superconducting materials such as Y-Ba-Cu-〇 series and L
Substances such as a-5r-Cu-0 series and La-Ba-Cu-0 series are already known. In particular, research on Y-Ba-Cu-0-based superconducting materials is progressing, and research is currently being actively carried out toward practical application.

The conventional manufacturing method for these superconducting materials is Y-Ba-C.
A typical example of the u-0 system is shown in FIG. That is, first, raw material powders, usually powders of yttrium oxide, copper oxide, and barium carbonate, are mixed in predetermined amounts. During mixing, an alcohol such as ethanol is added and wet mixing is performed to prevent the coexistence of water as much as possible. After drying, the mixture is mixed again if necessary, dried, and then pressure-molded to form granules or pellets. Next, this is calcined at around 9 (10°C), cooled, and then crushed, and the crushed product is wet-mixed.

Then, after drying, it is press-molded and sintered. The superconducting pulverized product obtained here is put into a suitable shape, such as a wire rod or a thin film (tape), for practical use.

[Problem that the invention seeks to solve]

The present inventors have been conducting intensive research on the manufacturing method of this type of superconducting material, and in this research, when manufacturing this type of superconducting material, in particular It has been found that the properties of the superconducting material obtained vary greatly depending on the amount of . For example, Y-Ha-Cu-0 system will be explained below as an example of a superconducting material that is a sintered body.

When a superconducting material absorbs water, it changes as shown in the following formula, and the superconducting material changes in quality.

2 YBazCu30b + 3 H20→YzBaC
u o3+ 3Ba(OR)z +5CuO+! 40□
Therefore, the problem to be solved by the present invention is to solve the above-mentioned problems of superconducting materials based on the presence of water.

[Means for solving problems]

This problem can be solved by covering the calcined or sintered body with a waterproof material.

That is, the present invention provides a method for producing a superconducting material by mixing predetermined raw material powders, calcining the calcined body, pulverizing the calcined body, then molding the body, and sintering the resulting molded body. The present invention relates to a method for producing a superconducting material characterized by coating a calcined body or (and) a sintered body with a waterproof material.

[Function and structure of the invention]

In the present invention, the above-mentioned reaction between the calcined body and/or sintered body and water is prevented by coating the calcined body or (and) the sintered body with a waterproof material, which may lead to superconductivity. It is possible to prevent deterioration of the properties of substances.

Waterproof materials used in the present invention include organic materials and inorganic materials. Examples of the former include sheets and films made of various waterproof substances as well as sheets and films treated with hydrophobic substances. Examples of waterproof materials include silicone compounds and various fluororesins, and more specifically silicone foils, polydimethylsiloxane, halogenated ethylene, and propylene polymers. Examples of the halogenated ethylene polymer include tetrafluoroethylene, monochlorotrifluoroethylene, dichlorodifluoroethylene, etc. alone or in copolymers with other polymers.

Typical examples of inorganic materials include metal films and foils. In this case, the metal film or foil itself is different from the mold used for calcination, and the metal film or foil itself is different from the mold used for calcination. It does not require any conditions required for this purpose, and is used solely for the purpose of waterproofing these sintered or calcined bodies. Therefore, in principle, the waterproof material used in the present invention is not used as a mold, and is clearly distinguished in this respect.

The method of the present invention will be explained below in order of steps.

First, a raw material powder is prepared. The raw material is appropriately selected depending on the type of the desired superconducting substance. For example, in the case of Y-Ba-Cu-0, yttrium oxide,
Using barium carbonate, copper oxide, and La-3r-Cu
In the case of -0 series, lanthanum oxide, strontium carbonate, and copper oxide are used. In the case of La-Ba-Cu-0 type, lanthanum oxide, barium carbonate, and copper oxide are used. These raw material powders are mixed in the desired composition ratio,
For example, in the case of the Y-Ba-Cu-0 system, these raw materials are blended in advance so that the composition of the target superconducting material obtained is as shown in FIG.

The raw material powders are then mixed, and this mixing is usually done in a wet manner by adding a liquid from outside the water, such as an alcohol such as ethanol. This is based on the reason that coexistence of water is undesirable. Wet mixtures can be air dried (
, or may be heated at a temperature of around 150'C or less. This wet mixing is repeated as necessary. By repeating this process, each component can be mixed uniformly, and the above-mentioned liquid is added to this dry product and wet mixing is repeated again. By repeating this process, the particle size of the raw material powder can be adjusted and the particle size of the raw material powder can be adjusted, making it easier to obtain the optimum filling particle size during molding.

Next, the raw material powder is pressure molded, and if necessary, after drying, the molded product is calcined. Note that during pressure molding, it is desirable to remove alcohol, etc. from the raw material powder, and for this purpose, it is usually dried. Pressure molding is usually performed to form pellets, but the shape is not limited to pellets and may be any shape that can be easily calcined. The molded body obtained here is then calcined. This calcination is performed for the purpose of uniformly mixing each component at the molecular level by reaction diffusion at high temperatures, and the temperature is appropriately determined depending on the type and blending ratio of the raw material powder used. In the case of Ba-Cu-0 system, it is usually 8 (10
°C or higher, preferably 850 to 950 °C, especially 9 (1
Preferably it is around 0°C. The calcining time depends on the temperature, but is usually about 6 to 48 hours, preferably about 12 to 24 hours.

The calcined body is then wet-pulverized again. The liquid agent used at this time is usually an alcohol-based agent such as ethanol, which is not available near water, and the grinding is carried out in a state where as little moisture as possible is absorbed during the grinding. After drying, sintering is performed. For sintering, a suitable mold is filled with the pulverized material, and the pulverized material is sintered while applying pressure if necessary.

At this time, unlike calcination, sintering is necessary and is carried out at a temperature at which the pulverized material is sufficiently sintered.

In the present invention, the sintered body is covered with a waterproof material and stored. Further, the calcined body may be covered with a waterproof material and stored as necessary while being subjected to the next sintering.

〔Example〕

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

Example I Production of Y1Ba2Cu+Ox (where X is 6 to 7): Y2O3, BaCO3, and C with a purity of 99.9% by weight or more
uO 1. O: 3.5: 2.1 (weight ratio)
The powder was wet mixed in a mortar in the presence of ethanol, and after air drying, the powder was filled into a mold and molded into pellets of about 10φ x 5 vsm using a hand press at a pressure of 1 (10 kg/cJ), and then 9 (10 ” The calcined product was calcined in the atmosphere for 24 hours at C and cooled in a furnace.The resulting calcined product was crushed in ethanol, and immediately thereafter, using an iron mold, it was heated to 510 kg/cm under reduced pressure.
Form into pellets (same size as above) at a pressure of 95
Sintering was performed at 0°C for 24 hours. The sintered product was wrapped in a polymonochlorotrifluoroethylene film and stored for 3 months.

Next, this was crushed and the superconducting point was measured. The measurement results were a critical temperature of 93K and a critical current density of 270A/cm2 measured in liquid nitrogen (77K).

Example 2 Production of Yo, a Bao, 7 Cu, oy (y is 2 to 3): In Example 1, the blending ratio of raw materials was changed to Y203:Ba
C(h:CuO=1.O: 4.L:
2. 3, and the temperature during sintering was 9 (10 °C), and the sintered product was wrapped in a polymonochlorotrifluoroethylene film and stored for 3 months.Then, it was crushed and the superconducting point was measured.The measurement results are Critical temperature 92K, critical current density measured in liquid nitrogen (77K) 2508/cm”
Met.

Comparative Examples 1 and 2 In Examples 1 and 2, the sintered products were left as they were in the atmosphere for 3 months, and then pulverized and the superconducting point was measured. These measurements have a critical temperature of 79 K and 78 K, respectively, and a critical current density of 13 A/c measured in liquid nitrogen (77 K).
m2.7 A/cm2.

[Brief explanation of the drawing]

Figure 1 is a ternary composition diagram of Y, Ba and Cu;
The figure is a flow sheet showing an example of a conventional method for manufacturing superconducting materials. (and above) Patent applicant Mitsubishi Cable Industries, Ltd.

Claims (10)

[Claims] (1) In a method for producing a superconducting material by mixing predetermined raw material powders, calcining the calcined body, pulverizing the calcined body, and then molding the calcined body, and sintering the obtained molded body, the above-mentioned calcined body or (and) a method for producing a superconducting material, which comprises coating a sintered body with a waterproof material. (2) The manufacturing method according to claim (1), wherein the waterproof material is an organic material. (3) The manufacturing method according to claim (1), wherein the waterproof material is a metallic material. (4) The manufacturing method according to claim (2), wherein the organic material is a halogenated polymer. (5) Claim 4, wherein the halogenated polymer is polyvinylidene chloride, polyvinylidene fluoride, chlorosulfonated polyethylene, polymonochlorotrifluoroethylene, tetrafluoroethylene, trifluoroethylene, or polyvinyl fluoride. manufacturing method. (6) When mixing the specified raw material powder, wet-mix it,
Claim No. 1 (1) characterized in that it is then dried.
The manufacturing method described in ). (7) The manufacturing method according to claim (1) or (2), wherein the calcined body is wet-mixed and then dried when pulverizing the calcined body. (8) Claim No. 1, wherein the predetermined raw material powder is a mixed powder of yttrium oxide, copper oxide, and barium carbonate.
The manufacturing method according to any one of Items to Items (3). (9) The manufacturing method according to any one of claims (1) to (3), wherein the predetermined raw material powder is a mixed powder of lanthanum oxide, strontium carbonate or barium carbonate, and copper oxide powder. (10) The raw material powders are blended so that the composition of yttrium, barium, and copper of the obtained superconducting material falls within the shaded range in the ternary composition diagram shown in FIG. The manufacturing method according to scope item (1) or item (4).