JPH0340957A - Production of superconductor and its molded material - Google Patents

Abstract

PURPOSE:To efficiently produce the oxide superconductor having excellent characteristics by extrusion-molding a mixture of the flaky oxide superconductor crystal grains having a specified width-to-thickness ratio and an org. high molecular binder and sintering the molded product. CONSTITUTION:When a Bi-Pb-Sr-Ca-Cu-O-based superconductor, for example, is produced as the oxide superconductor, the powders of Bi2O3, PbO, SrCO3, CaCO3 and CuO as the raw material are mixed in a specified ratio, the mixture is calcined at 700-850 deg.C for about 12hr, the calcined material is crushed, the obtained powder is pelletized, and the pellets are sintered at 830-870 deg.C to obtain the pellets of Bi-Pb-Sr-Ca-Cu-O-based oxide superconductor. The pellets are recrushed to obtain flaky crystal grains having >=10 width-to-thickness ratio, and 50-100 pts.wt. of an org. high molecular binder such as PVA is added to 100 pts.wt. of the grains and mixed. The mixture is extrusion-molded into a rod, and the rod is sintered at 800-900 deg.C to produce the oxide superconductor having a high critical temp. and a high critical current density.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing a superconductor, which comprises extruding a material containing an oxide superconductor and sintering the molded body, and a molding material for the extrusion molding. .

BACKGROUND OF THE INVENTION Providing an oxide S conductor processed into a practical form such as a wire rod has become an important issue.

Conventionally, methods for producing superconductors include filling a metal pipe with oxide superconductor powder, plastically processing this filling into a desired shape, and then sintering it; A method of forming a vapor deposited layer has been proposed.

However, the method using metal pipes has the problem of having a large number of steps and being inferior in manufacturing efficiency, and the method of forming a vapor deposition layer requires advanced vapor deposition technology and equipment, resulting in poor manufacturing efficiency). There was a problem in that it was difficult to obtain large products such as long objects.

Problems to be Solved by the Invention In view of these problems, the present inventor came up with the idea of using an extrusion molding method, and as a result of intensive research to achieve that method, the inventor prepared a molded material containing an oxide superconductor. We succeeded in developing a method for extruding this into a predetermined shape and sintering the molded body. However, although this development method can overcome the above-mentioned problems, it has been found that the superconductor obtained is inferior in superconducting properties, particularly in critical current density.

The object of the present invention is to solve the problem of superconducting properties and to develop a method for manufacturing a superconductor using an extrusion molding method that can be put into practical use.

Means for Solving the Problems The present invention overcomes the above problems by using an oxide superconductor with a special crystalline form.

That is, the present invention involves extrusion molding a mixture containing tabular crystal grains having a radius/thickness ratio of 10 or more made of an oxide superconductor and a binder made of an organic polymer, and sintering the molded body. A method for producing a superconductor, characterized by comprising a mixture comprising tabular crystal grains having a width/thickness ratio of 10 or more made of an oxide superconductor and a binder made of an organic polymer. The present invention provides a molding material for extrusion molding.

By holding the crystal particles of the active oxide superconductor with a binder made of an organic polymer, a molding material for forming a superconductor that can be extruded can be obtained.

In this case, by using tabular crystal grains with a width/thickness ratio of 10 or more as the oxide superconductor, when extruded, the width direction of the oxide superconductor particles can be oriented in the extrusion direction. During sintering, crystal grains grow predominantly in the direction of their orientation. Current flows more easily in the width (length) direction of the tabular crystal of an oxide superconductor than in the thickness direction.
As a result, a superconductor is formed in which current flows easily in the longitudinal direction (extrusion direction).

Examples of Constituent Elements of the Invention There are no particular limitations on the oxide superconductor used in the present invention, such as 6 YBa2 Cu30a or Yt-bBabC.
Y-based oxide superconductor such as ubc, Bat-dKtiB
i Ba-based oxide superconductor such as O3, Nd2-ac
Nd-based oxide superconductor such as e@Cu04-f, B i
2-tPbt Sr2 Ca2 Cu30h or Bi2
Sr2 Cat-IY, B like CL1208-J
i-based oxide superconductor, other La-based oxide superconductor, T
I-based oxide superconductors, Pb-based oxide superconductors, etc., those in which components such as Y are replaced with other rare earth elements, or those in which components such as Ba are replaced with other alkaline earth metals, or Any known materials can be used, such as those in which the O component is replaced with F or the like. The oxide superconductor can be produced by, for example, mixing raw materials at a predetermined composition ratio using a wet mixing method such as a coprecipitation method or a sol-gel method, or any other suitable mixing method, and then calcining or sintering the mixture. It can be obtained by subjecting it to a crystallization treatment to form a superconductor.

The oxide superconductor used is a tabular crystal grain having a width/thickness ratio of 10 or more, which can be obtained, for example, by pulverizing the sintered body described above. The particle size is preferably 100 μm or less, especially 50 μm or less based on the width or length direction.

The molding material for extrusion molding of the present invention can be obtained by mixing tabular crystal grains of an oxide superconductor with a binder made of an organic polymer. For mixing, an appropriate kneader such as a roll or a pressure kneader may be used. During mixing, appropriate regulators such as organic plasticizers, auxiliaries, and solvents may be used in combination.

The organic polymer used may be any organic polymer as long as it can provide the fluidity necessary for extrusion molding as a mixture with the tabular crystal grains of the oxide superconductor. Generally, polyvinyl alcohol,
Thermoplastic resins such as polyethylene glycol, polyvinyl butyral, and polymethyl methacrylate, rubber-based polymers, and the like are used.

In addition, examples of plasticizers used as necessary include phthalic acid esters such as dibutyl phthalate, diethyl phthalate, and dioctyl phthalate, fatty acid esters,
Polyethylene glycol derivatives, glycerin, polyalkyl glycols, etc., and auxiliary agents include natural fish oil, benzenesulfonic acid, phosphates, fatty acids such as glycerin triolate, synthetic surfactants, paraffin wax, stearic acid, etc. However, as a solvent, for example,
Alcohols such as methanol and ethanol, aromatic hydrocarbons such as toluene, xylene and benzene, trichloroethylene, dichloroethylene, methyl ethyl ketone, acetone and the like are used.

The appropriate amount of the organic polymer binder used is 5 to 100 parts by weight per 100 parts by weight of the tabular crystal grains of the oxide superconductor. If the amount used is less than 5 parts by weight, the molded product will have poor shape retention and will be easily broken when handled, while if it exceeds 100 parts by weight, it will be difficult to obtain a dense superconductor.

In the manufacturing method of the present invention, the molded material containing tabular crystal grains of an oxide superconductor is extruded, and the molded product is sintered to obtain a superconductor.

As the extrusion molding machine, an appropriate one such as a screw type or a ram type may be used. The molding form may be arbitrary, such as string-like or tape-like. The sintering temperature may be determined as appropriate depending on the type of oxide superconductor, etc. -Generally 700-1200℃
It is. When sintering the molded body, it may be degreased in advance to remove organic components. Further, appropriate secondary processing may be performed, such as winding the molded body around a support. The sintering atmosphere is determined depending on the oxide superconductor. The sintering time is typically 200 hours or less, especially from 2 to 150 hours, but is not limited thereto. The sintering process integrates the crystal grains of the oxide superconductor to form the desired superconductor.

Effects of the Invention According to the present invention, since an oxide superconductor consisting of tabular crystal grains with a radius/thickness ratio of 10 or more is used, a superconductor having excellent superconducting properties such as critical current density can be efficiently produced using an extrusion molding method. It can be manufactured as follows. It is also easy to manufacture large-sized superconductors.

Examples Bi2O3, PbO5SrCO3, CaCO3 and Cu
A predetermined amount of O powder is mixed and calcined at 750 to 850°C for 12 hours.
- molded into pellets and heated at 830 to 870°C for 50
After time sintering treatment, B12-t Pbr 5r2Ca2
A superconductor pellet consisting of Cu 30 h (t −0,6) was obtained.

The pellets are then crushed to a width/thickness ratio of (0 to 50).
To obtain tabular crystal grains with a particle size of 0.1-10 μm, 100 parts by weight of these were mixed with 50 parts by weight of polyvinyl alcohol, 5 parts by weight of dibutyl phthalate, and 20 parts by weight of toluene in a pressure kneader to form a molding material. The obtained molded material was then fed to an extruder with an L/D of 12, and extruded at various temperature settings from 80 to 180°C to obtain an outer shape of 1. A superconductor consisting of a series of rods was obtained by sintering the string at 800 to 900°C. The sintering time is 12 to 1
00 hours.

The critical temperature in the longitudinal direction of each superconductor obtained is 1
00 to 105, and the critical current density is 3000 to 1
0000 A/ctj (77,3K).

The critical temperature is determined by measuring the change in electrical resistance due to salinity using the four-terminal method under a current density of 0, 1 A/cj without cooling with liquid helium.
This is the temperature when .

In addition, the critical current density was determined by gradually increasing the current value while cooling the power lead with liquid nitrogen, measuring the change in voltage between the voltage terminals due to the applied current using the four-terminal method, and measuring the voltage at 1 μV / cm with an x-y recorder. This is the value obtained by dividing the current value when the appears by the cross-sectional area of the superconductor.

Comparative Example B i 2- consisting of crystal grains with a width/thickness ratio of less than 10
tPbt Sr2 Caz CL130h (t =
A molding material was prepared according to the example except that 0.6) was used, and an extrusion molded product and a sintered product were obtained using this material.

The critical temperature in the longitudinal direction of each superconductor obtained was 10
0 to 105, which was almost the same as in the example, but 1,
The critical current density is lO~50 A/cd (77,3K
) was low.

Claims (2)

[Claims] 1. A superconductor characterized by extrusion molding a mixture of tabular crystal grains having a width/thickness ratio of 10 or more made of an oxide superconductor and a binder made of an organic polymer, and then sintering the molded body. How the body is manufactured. 2. 1. A molding material for extrusion molding, comprising a mixture comprising tabular crystal grains having a width/thickness ratio of 10 or more made of an oxide superconductor and a binder made of an organic polymer.