JPH01272011A - Superconductive material - Google Patents

Abstract

PURPOSE:To aim at increasing critical current density by mixing superconductive ceramic powder having a specific particle diameter with a solvent, binder, plasticizer, deflocculant and penetrant to form a paste, and applying it on a supporting body and sintering it. CONSTITUTION:A paste that is produced as a result of mixing superconductive ceramic powder having a particle diameter in range from 0.1mum or more to less than 1mum with a solvent, binder, plasticizer, deflocculant and penetrant, is applied on a supporting body, sintered, thus a superconductive material shaped in a thin membrane of 5mum or more in its thickness is produced. If the particle diameter of the superconductive ceramic particles is less than 0.1mum, it is extremely difficult to disperse the particles evenly in the paste because then primary particles may strongly aggregate together. On the other hand, if the particle diameter exceeds 1mum, any thin superconductive ceramic membrane having a higher density can not be formed and its critical current density becomes smaller. Water or methyl ethyl ketone, etc., may be used as a solvent, acrylic polymer, etc., as a binder, butyl ethylene phthalate, etc., as a plasticizer, phosphate, etc., as a deflocculant and alcohol, as a penetrant.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a superconducting material comprising a support and a thin film of superconducting ceramics formed on the support.

(Prior art) Recently, composite oxides mainly containing lanthanide elements such as La and Y, alkaline earth metal elements, copper, etc. have been developed to have a high criticality at liquid hydrogen temperature (20K) or liquid nitrogen temperature (77K). It is attracting attention as a superconducting ceramic with a temperature Tc.

Among them, some Y-Ba-Cu-0-based superconducting ceramics have a Tc higher than the liquid nitrogen temperature.
It is expected that it will be put to practical use in a wide range of fields.

These Y-Ba-Cu-0-based high-temperature superconducting ceramics also become superconducting when cooled with an inexpensive coolant such as liquid nitrogen, so Nb-Ti-based superconductors, which only exhibit a superconducting state in liquid helium, If it can be used in superconducting magnets instead of alloys, it would have great economic benefits.

However, in order to make these superconducting ceramics into practical superconducting materials, they must be able to be processed into wires, thin films, etc.

One such material is one in which a thin film of superconducting ceramic is formed on a support.

As a method for forming a thin film of superconducting ceramics on a support, vapor phase methods such as CVD and sputtering have been used so far.

Since the gas phase method has the problem of requiring large-scale equipment, various easier thin film forming methods have been developed.

Examples of such thin film forming methods include paste and coating methods.

The paste coating method involves adding a solvent to superconducting ceramic powder,
Binders, plasticizers, peptizers 1. This is a method for producing a thin film of superconducting ceramics, in which a paste made by mixing a wetting agent and a wetting agent is applied onto a support and sintered.

Conventionally, in the paste coating method, the particle size of the superconducting ceramic powder used in the paste was large, 1 to 5 μm, and therefore the critical current of the formed superconducting ceramic thin film was as small as several + A/cd.

(Technical means for solving the problem) The present invention provides a superconducting ceramic film made by forming a thin film of superconducting ceramics on the surface of a support by conventional methods such as vapor phase coating, liquid phase coating, and paste coating. This is a superconducting material that solves the drawbacks of superconducting materials.

The present invention provides superconducting ceramic powder with a particle size of 0.1 am or more and less than 1 μm, a solvent, a binder, a plasticizer, a peptizer,
It is a superconducting material obtained by applying a paste made by mixing a wetting agent and a wetting agent onto a support and sintering it.

If the particle diameter of the superconducting ceramic particles in the paste used for manufacturing the superconducting material of the present invention is smaller than 0.1 μm, the agglomeration of the particles is too strong, making it difficult to uniformly disperse the particles in the paste. This is not desirable because it becomes extremely difficult.

On the other hand, if the particle size of the superconducting ceramic particles in the paste is 1 μm or more, a thin film of superconducting ceramic with high density cannot be obtained, and therefore the critical current density is also low, which is not preferable.

Although the method for obtaining superconducting ceramic particles having a particle size of 0.1 am or more and less than 1 am is not particularly limited, the following method is used as an example.

(a) Co-precipitation method (b) Multi-stage wet method (C) Wet-dry method (d) Hydrothermal method (e) True gel method (f) Flux method Next, these methods will be explained.

(a) Co-precipitation method: A solution of a metal compound corresponding to each component of the target superconducting ceramic and a precipitate forming agent are mixed to form a coprecipitate. This coprecipitate is then pre-sintered.

(b) Multi-stage wet method: When a solution of a metal compound corresponding to each component of the target superconducting ceramic is brought into contact with a precipitate forming agent to form a coprecipitate, the precipitate formation is divided into several stages. This is the way to do it. After forming a coprecipitate, temporary sintering is performed.

(C) Wet-dry method: A solution of a metal compound corresponding to a part of the components of the target superconducting ceramic is brought into contact with a precipitate to form a coprecipitate. Next, compounds corresponding to the remaining components are mixed into this coprecipitate by a dry mixing method. This mixture is pre-sintered.

(d) Hydrothermal method: This is a method in which the coprecipitate formed by the coprecipitation method is hydrothermally treated using an autoclave or the like. After the hydrothermal treatment, the coprecipitate is pre-sintered.

(e) Sol-gel method Hydroxycarboxylic acid and glycols are added to an aqueous solution of metal nitrates corresponding to each component of the target superconducting ceramic to form a coprecipitate. The generated coprecipitate is thermally decomposed at 300 to 400°C and then pre-sintered.

(") Flux method A metal compound corresponding to each component of the target superconducting ceramic and a flux are mixed using a dry mixing method, and this mixture is pre-sintered. The flux includes an alkaline earth metal or an alkaline earth metal. halides are commonly used.

In these methods, temporary sintering is preferably performed at 500 to 950°C.

The solvent, binder, plasticizer, peptizer, and wetting agent used in the paste can be selected from those commonly used when fine ceramics are made into a paste and molded by a doctor blade method or a casting method. Examples of this include those shown in the following examples.

[Container 1] Aqueous: Water (Can contain nonionic surfactants and allocols as antifoaming agents.) Non-aqueous: methyl ethyl ketone, acetone, ethanol,
Benzene, prochloromethane, butanol, diacetone, propatool, methyl isobutyl ketone, toluene,
Trichlorethylene, xylene, isopropanol, denatured alcohols, esters.

[Binding agent] Water-based acrylic polymer, acrylic polymer enylzidine, polyethylene oxide, hydroxyethyl cellulose, methyl cellulose, polyvinyl alcohol, isocyanate, water-based urethane, methacrylic acid copolymer salt, wax emulsion, ethylene-vinyl acetate copolymer Polymer emulsion.

Non-aqueous: cellulose acetate, cellulose butyrate, cellulose acetate butyrate, nitrocellulose, petroleum resin, polyethylene, polyacrylic acid ester, polymethyl methacrylate, polyvinyl alcohol,
Polyvinyl butyral, vinyl chloride, polymethacrylate, ethyl cellulose, abietic acid resin.

[Plasticizer 1 Water-based Nibutyl ethylene phthalate, Dibutyl phthalate, Ethyl toluene sulfamide, Glycerin, Polyalkyl glycol, Triethylene glycol, Tri-N-
Butyl phosphate, vetriol, polyol.

Non-aqueous Nibutylbenzyl phthalate, dibutyl phthalate, butyl stearate, dimethyl phthalate, phthalate ester mixture, polyethylene glycol Eft conductor, tricresol phosphate.

[Peptizer] Water-based: phosphate, phosphoric acid complex salt, allylsulfonic acid, natural sodium salt, acrylic oligomer.

Non-aqueous: fatty acids, fatty acid esters, glycerin triesters, unsaturated fatty acids, fish oil, synthetic surfactants, benzenesulfonic acid, octadiene.

[Wetting agent] Water-based: octylphenoxyethanol, alcohol,
Nonionic surfactant.

Non-aqueous: alkylaryl polyether alcohol, polyethylene glycol alkyl ether, polyethylene glycol aryl ether, polyoxyethylene ester, glycerin esters, alcohols.

As the support for the superconducting material of the present invention, those conventionally used in paste coating methods can be used.

Examples of such supports include wires, tubes, plates, fibers, woven fabrics, nonwoven fabrics, films, porous metal substrates, and porous ceramic substrates.

Application of the paste on the support described in -F can also be performed by a known method. Examples of such methods include screen printing and doctor blading.

The paste is preferably applied to a thickness such that the thickness of the superconducting ceramic thin film after sintering is 5 μm or more.

After applying the paste on the support, it is dried to remove the solvent in the paste, and then the support is heated at 200°C to 50°C.
Heating to 0° C. removes binders, plasticizers, peptizers, and wetting agents by evaporation and thermal decomposition. Next, this support is heated to 500-950''C to sinter the layer of superconducting ceramic powder formed on the surface of the support to form a thin layer of superconducting ceramic Jf9.

(Effects of the present invention) The superconducting material of the present invention can be manufactured without using large-scale equipment such as a vapor phase method. In addition, superconducting materials manufactured by liquid phase coating have a critical current density of 1 OOA/CI
! With the above, several tens of A/cd of material using the conventional paste method
shows a much larger value than .

(Example) Examples of manufacturing the superconducting material of the present invention are shown below.

Reference example 1 Yttrium chloride (YCf2.6H,O) 0.1 mol,
Barium chloride (B a CI! 2-2 H, O) 0.2
mole, and copper chloride (CuCI!, .2H,O) 0.3
mol was dissolved in 11 mol of water. To this solution, 5QOd of 2M aqueous sodium hydroxide solution was added to perform neutralization and precipitate formation. This coprecipitate slurry was hydrothermally treated at 250°C for 4 hours in an autoclave.

After the hydrothermal treatment, the coprecipitate was washed with water until no Na'' ions were detected and then dried.

This coprecipitate was pre-sintered at 850°C for 2 hours.

When the crystal structure of the obtained powder was examined by X-ray diffraction, it was found to be an oxygen-deficient layered perovskite structure of YB a zCLl:107-X.

Moreover, the average particle diameter of this powder was 0.1 to 0.3 μm.

Reference Example 2 0.1 mole of yttrium chloride (ycz2.6H,O) and 0.05 mole of barium chloride (BaCfz.2H□0) were dissolved in water 11, and 3N ammonium carbonate aqueous solution 11 was added thereto. A precipitate formed.

This coprecipitate was washed with distilled water, dried, and
Temporary sintering was carried out at ℃.

This sintered powder contains 0.0% barium carbonate (B a Co).
15 mol and basic copper carbonate [CuzCO2(OH)210
．． 15 mol was added and mixed in a ball mill.

After mixing in a ball mill, this powder was pre-sintered in air at 800°C.

When the crystal structure of this powder was investigated by X-ray diffraction, it was found that Y
B az Cu 30? It was found that it has an oxygen-deficient layered perovskite structure.

Moreover, the average particle diameter of this powder was uniform at 0.3 to 0.5 μm.

Example 1 For 100 parts of superconducting ceramic powder of Reference Example 1,
34 parts of toluene as a solvent, 10 parts of polyvinyl butyral as a binder, and 4 parts of dibutyl phthalate as a plasticizer.
5 parts, and 0.9 parts of oleic acid as a peptizer,
A paste was made.

After thoroughly removing bubbles from this paste using vacuum defoaming,
It was coated onto a 00x100x1 alumina plate to a thickness of 30 μm using a doctor blade.

After drying this alumina plate, it was heat treated at 400°C to remove organic substances, and then sintered at 900°C for 2 hours. The thickness of the obtained superconducting ceramic thin film was about 25 μm.

The critical temperature of this thin film is 85, and the field current density is +50
It was A/cd.

Examples 2 to 5 The same superconducting ceramic powder, binder, plasticizer, and peptizer as in Example 1 were used, but the type of solvent and the ratio of the binder to the superconducting ceramic powder were changed. We prepared superconducting materials by applying them to various supporting soils. The results are shown in Table 1.

Example 6 The superconducting ceramic powder of Reference Example 2 was coated on an alumina substrate in the same manner as in Example 1, dried, heat treated, and sintered to form a thin model of superconducting ceramic.

The critical temperature of this thin film is 93, and the critical current density is 152.
It was A/cd.

Table 1 Comparative Example 1 Yttrium oxide (Y2O,) 0.05 mol, barium carbonate (B a CO:+) 0.2 mol, oxidized steel (Cu
b) 0.3 mol was added to water 502 and thoroughly mixed using a ball mill to prepare a mixed powder.

The mixed powder was separated from the suspension containing the mixed powder by filtration, and this powder was placed in a drier to dry it to remove water.

After drying this powder, it was pre-sintered at 850°C in air. The pre-sintered mixed powder was pulverized with a ball mill. Temporary sintering and crushing were repeated four times.

When this powder was observed using a transmission electron microscope, it was found that the particle size was 1 to 5 μm and the particle size distribution was nonuniform.

This powder was applied onto an alumina plate support in the same manner as in Example 1, and after drying, heat treatment and firing were performed to create a superconducting material in which a thin film of superconducting ceramic was formed on the alumina plate support. .

The critical temperature of this superconducting material is 85%, and the critical flow density is 3%.
0 A/ct! Met.

Comparative Example 2 In the same manner as in Reference Example 1, Y component, Ba component, and Cu
A coprecipitate consisting of the components was prepared and pre-sintered at 1000°C. The particle size of the obtained superconducting ceramic powder was 1 to 3 μm.

A paste of the above superconducting ceramic powder was prepared using the same solvent, binder, plasticizer, and peptizer as in Example 1. This paste was applied onto an alumina substrate with a doctor blade to a thickness of 25 μm. The heat treatment and sintering after drying were also performed in the same manner as in Example 1. The obtained superconducting material has a critical temperature of 85 and a critical current density of 45 A.
It was just a CD.

Comparative Example 3 A superconducting material was produced in the same manner as in Example 1, except that the coating thickness on the alumina substrate was 2 μm. The critical temperature of this superconducting material is 30, and the critical current density is IOA.
/c+! It was nothing more than

Claims (3)

[Claims] (1) A superconducting material characterized in that a thin film of 5 μm or more in thickness, made of superconducting ceramic powder with a particle size of 0.1 μm or more and less than 1 μm, is formed on a support. (2) The superconducting material according to claim 1, wherein the superconducting ceramic thin film has a thickness of 5 μm or more. (3) A method for producing a superconducting material, which comprises applying a superconducting ceramic paste having a particle size of 0.1 μm or more and less than 1 μm onto a support, and heating and firing the paste.