JPH0238358A - Production of oxide superconductor - Google Patents

Abstract

PURPOSE:To obtain an oxide superconductor having high critical current density by placing a molded article of mixed powder of a specific element, Ba and Cu in a furnace and burning the molded article while introducing oxygen into the furnace and applying a magnetic field. CONSTITUTION:In a method of producing an oxide superconductor of R-Ba-Cu-O (R element such as Eu, Gd, Tb, By, Ho, Er or Tm having high magnetic susceptibility among group IIIa elements of the periodic table). Namely, mixed powder containing the element R, Ba and Cu in a given ratio is prepared and the mixed powder is subjected to pressure molding to prepare a molded article. The molded article is placed in a furnace capable of preparing an oxygen existing atmosphere in the interior and a magnetic field generator is used. Then oxygen is sent to the furnace and the molded article is sintered while applying a magnetic field to the interior of the furnace by the magnetic field generator to give the aimed superconductor.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method of manufacturing an oxide superconductor with a high critical current density using magnetic force.

"Prior Art" In recent years, oxide-based ceramic superconducting materials have been developed as new superconducting materials different from conventional intermetallic compound-based superconducting materials or alloy-based superconducting materials. This type of oxide-based superconducting material has an extremely high critical temperature at which it transitions from a normal conductive state to a superconducting state, and some materials can maintain their superconducting state by cooling with liquid nitrogen. , various research and development efforts are underway in terms of its application.

Conventionally, in order to manufacture this type of oxide superconductor, compound powder of each element constituting the oxide superconductor (for example, when manufacturing a Y-B a-Cu-0 based oxide superconductor, Y , 03 powder, BaCO3 powder and CuO powder)
were mixed in a predetermined ratio, then calcined to remove unnecessary components, and further heat treated to obtain an oxide superconductor.

[Problems to be Solved by the Invention] However, this type of oxide superconductor has a problem in that the critical current density is much lower than the value required from a practical standpoint.

One of the reasons for this is that oxide superconductors are created by compacting powder and sintering compacts, so the density of the sintered compact is lower than the theoretical density, and the internal Due to the presence of countless pores, the bonding between the superconductor crystal grains is not satisfactory, and the presence of many bonding points between the superconductor crystal grains inside the sintered body reduces the number of current paths. It is assumed that there is.

Another reason is that the oxide superconductor has a layered structure based on perovskite, and Cu in the basic lattice
Since the −0 plane is responsible for superconductivity, in order to exhibit anisotropy that allows current to flow easily in a specific direction of the crystal, when a sintered body is manufactured as described above, the inside of the sintered body It is assumed that the crystal orientation becomes disordered, the number of current paths decreases, and the critical current density does not improve.

The present invention was made in order to solve the above problem by focusing on the disordered crystal orientation of conventional sintered bodies, and provides a method for manufacturing an oxide superconductor with a high critical current density. The purpose is to

"Means for Solving the Problems" In order to solve the problems, the present invention provides R-BaCu-
0 (However, R is Eu of Group IIIa elements of the periodic table.
, Gd, Tb, Dy, Ho, Er, Tm, and other elements with high magnetic susceptibility. ) system oxide superconductor, in which the A element, B element and Cu
A mixed powder containing O and O in a predetermined ratio is created, and this mixed powder is press-molded to create a molded body. At the same time, a heating furnace whose interior can be adjusted to an oxygen-rich atmosphere, and an outside of this heating furnace are used. A method in which a molded body is placed inside the heating furnace using a magnetic field generator installed in the heating furnace, oxygen is sent into the heating furnace, and the molded body is sintered while applying a magnetic field inside the heating furnace with the magnetic field generator. It is.

"Effect" The magnetic field generated in the heating furnace by the magnetic field generator orients the elements with high magnetic susceptibility contained inside the sintered body, and a solid phase reaction occurs in conjunction with this element, resulting in good orientation. oxide superconductor is produced.

"Example" FIG. 1 shows an example of a processing apparatus suitable for carrying out the method of the present invention, and this processing apparatus 1 mainly consists of a cylindrical heating furnace 2 and a magnetic field generator 3. ing. The heating furnace 2 has a heater embedded in its peripheral wall so that the inside can be heated to a desired temperature. Further, a lid body 4 is detachably provided at the end of the heating furnace 2, and a ventilation pipe 5 for intake and exhaust is inserted through each lid body 4, and each ventilation pipe 5 has a flow path 6.
is connected to the oxygen gas supply source 7 via the oxygen gas supply source 7, circulates oxygen gas through the oxygen gas supply source 7, the flow path 6, and the heating furnace 2, and generates an oxygen gas flow inside the heating furnace 2. is now possible.

To practice this invention and produce an oxide superconductor, starting materials are first prepared. As this starting material, an oxide superconductor, a material containing an element constituting the oxide superconductor, or a mixture thereof is used.

ii? As the oxide superconductor, R-Ba-Cu
-0 (However, A is 100u, Gd, Tb, Dy, I-(o
, Er, and Tm. ) series are used. Examples of materials containing elements constituting the oxide superconductor include powders containing the elements R, Ba, and Cu;
Alternatively, these calcined powders can be used. The powders used here include oxide powders, chloride powders,
These are compound powders or alloy powders such as carbonate powders, sulfide powders, and fluoride powders. For example, as the copper oxide powder, Cuo, CUtO, C1130tCuiOt, etc. can be used.

A mixed powder can be obtained by mixing these powders so that each element is in a predetermined ratio. In addition, to prepare the mixed powder, the above-mentioned powder method is usually used, but the method is not limited to this method. Each element is coprecipitated as an oxalate, and the precipitate is dried to form a powder. It is also possible to apply a coprecipitation method to form a mixed powder. In addition, alkoxide compounds, oxyketone compounds, cyclopentadienyl compounds, etc. of the above-mentioned necessary elements are mixed in a predetermined ratio to form a liquid mixture, and water is added to this liquid mixture to hydrolyze it to form a sol, A sol-gel method may be applied in which this sol-like substance is heated to gel, and the gel is heated to form a solid phase and then ground to obtain a mixed powder.

Here, if the mixed powder contains unnecessary components such as carbon, the mixed powder is calcined. This calcining process involves heating the mixed powder to 700% in an oxygen gas atmosphere or air.
This is done by heating to ~1000°C for about 1-100 hours.

Next, the mixed powder or calcined powder is compacted into a desired shape by compaction processing such as press working or isostatic extrusion to obtain a compact. Note that calcination treatment may be performed at the stage of forming this molded body.

Next, this molded body is placed inside the heating furnace 2 shown in FIG. Oxygen gas is circulated via a gas supply source 7.

In addition, the heater of the heating furnace 2 is energized to heat the inside of the heating furnace 2 to 850 to 950°C, and the magnetic field generator 3 is operated to apply 0.1 to ) is applied. The strength of the magnetic field applied at this time is 0
．． 5-5T is preferred.

After the above treatment has been carried out for about 1 to 100 hours, the supply of electricity to the heater of the heating furnace 2 is stopped and the molded body is gradually cooled.

Through the above operations, a solid phase reaction progresses inside the molded body, and
An n-Ba-Cu-0 based oxide superconductor is produced. In addition, since oxygen gas is supplied to the inside of the heating furnace 2, sufficient oxygen can be supplied during sintering of the oxide superconductor, making it possible to manufacture an oxide superconductor without oxygen deficiency. can. Furthermore, since the element R contained in the compact is an element with high magnetic susceptibility, it is oriented during sintering by the magnetic field generated inside the heating furnace 2. Therefore, as the solid phase reaction progresses, the elements are oriented and an oxide superconductor is produced, resulting in an oxide superconductor with good orientation. Therefore, an oxide superconductor with a well-organized crystal structure and a high critical current density can be obtained.

"Manufacturing Example" An oxide superconductor with a composition of Y + B atc 11307-6 and Eu, an oxide superconductor with a composition of B atc u307-5, an oxide superconductor with a composition of Ho + B atc t++07-5, and E r, B atc Ll!
An oxide superconductor having a composition of 107-5 was manufactured.

As starting materials, B a CO3 powder and CuO powder, Y
, 0. Powder or E auto 3 powder or Hoe
'3 powder or ErzO3 powder was mixed to have the above composition to prepare each mixed powder, and these mixed powders were press-molded to a width of 3 mm, a length of 20 mm, and a thickness of 2 m.
After forming into a plate shape of m, it was heated at 900℃ in the atmosphere for 2
A calcining treatment was performed by heating for 4 hours. Next, the first calcined item
In an oxygen gas stream using the apparatus shown in the figure, 950
It was sintered by heating at ℃ for 24 hours. Note that during this sintering, various samples were manufactured by increasing or decreasing the strength of the magnetic field applied to the compact.

Table 1 shows the results of measuring the critical temperature and critical current density for each sample.

From the results shown in Table 1, it was revealed that the critical temperature and critical current density were improved by applying a magnetic field during sintering. That is, it has been found that it is possible to adjust the crystal orientation of the oxide superconductor by applying a magnetic field during sintering, and in that case, the critical temperature and critical current density can be improved.

Furthermore, from the results shown in Table 1, the strength of the magnetic field when sintering this type of oxide superconductor is preferably 0.5 T or more.

"Effects of the Invention" As explained above, the present invention provides a method for applying a magnetic element to a magnetic field in order to apply a magnetic field when sintering a compact formed by compacting a raw material for an oxide superconductor containing an element with high magnetic susceptibility. Since crystals can be generated according to the oriented elements, an oxide superconductor with uniform crystal orientation can be produced. Furthermore, since oxygen is sent into the heating furnace during sintering, an oxide superconductor can be produced without oxygen shortage. Therefore, by carrying out the present invention, it is possible to obtain an oxide superconductor having excellent properties such as high critical temperature and high critical current density.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a processing apparatus suitable for use in carrying out the present invention. ... Processing device, 2... Heating furnace, 3... Magnetic field generator, 4... Lid, 5... Ventilation pipe, 6... Channel, 7
...Oxygen gas supply device.

Claims (1)

[Claims] R-Ba-Cu-O (where R is Eu, Gd, Tb, Dy, Ho, Er, T among the IIIa group elements of the periodic table)
Indicates one or more elements with high magnetic susceptibility, such as m. )
In the method for producing a oxide superconductor of the oxide superconductor, a mixed powder containing the above-mentioned elements R, Ba, and Cu in a predetermined ratio is created, and this mixed powder is pressure-molded to create a molded body, and the inside is Using a heating furnace that can be adjusted to an oxygen-rich atmosphere and a magnetic field generator installed outside the heating furnace, a molded body is installed inside the heating furnace, oxygen is sent into the heating furnace, and the magnetic field generator is installed. A method for producing an oxide superconductor, comprising sintering a compact while applying a magnetic field inside a heating furnace.