JPH01108157A - Production of oxide superconducting material - Google Patents

Abstract

PURPOSE:To uniformly and sufficiently feed a small quantity of oxygen and enable production of a stabilized material, by filling a precursor in a hollow vessel and passing an O2-containing gas through the interior thereof in heat- treating the precursor, such as powdery form, providing an oxide superconductor. CONSTITUTION:A powdery, granular or massive precursor 10, containing elements constituting an oxide superconductor expressed by the formula A-B-Cu- O (A is one or more of group IIIa elements, such as Sc, Y, Ce, Yb, Er, Ho and Dy; B is one or more group IIa elements, such as Ca, Sr and Ba) and capable of providing the oxide superconductor by subjecting the precursor to heat treatment is prepared. The precursor 10 is then filled in a hollow vessel 11 having a gas feed port (11a) and a discharge port (11b) and a gas containing O2 is then fed from the feed port (11a) into the vessel 11, passed through interstices between particles of the precursor 10 in the vessel and then discharged from the discharge port (11b). The interior of the vessel 11 is simultaneously heated to heat-treat the precursor 10.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to magnetic levitation trains, nuclear fusion reactors, single crystal pulling devices,
Materials for superconducting magnets used in magnetic separation devices, medical devices, magnetic propulsion ships, etc., or Josephson elements, S
Q LJ I l) (Supcrconducti
n.

Quantum Interference Devi
'! of oxide superconducting materials used as sputtering targets for the production of thin film superconducting materials such as ce), materials for printed circuit board wiring, etc. Regarding the 1m method.

[Prior Art]' Recently, oxide-based superconducting materials have been discovered as new superconducting materials that can maintain a superconducting state at high temperatures exceeding liquid nitrogen temperatures.

This type of oxide superconducting material has the general formula A・-B-Cu-
O (However, A is Y, Sc, La, Ca, Yb.

l~10. Periodic table such as Er, DV [1 [represents one or more elements of group A, B is represented by M (represents one or more elements of group IIa of the periodic table such as 1, Ca, 3r, 3a)] It is an oxide that is

As an example of a method for manufacturing this type of superconducting material, a mixed powder is prepared by mixing the powder containing the above-mentioned element He, the powder containing the Moeki B element, and the copper oxide powder at a predetermined component ratio. A known method is to directly heat-treat this mixed powder, or heat-treat a compact formed by compacting the mixed powder to form a sintered body, and then crush this sintered body to obtain a superconducting material. ing. In addition, a method of powdering nitrate M salt, etc. obtained from a solution containing the above-mentioned helium elements and a chemical method such as a coprecipitation method or a sol-gel method, and then decomposing and reacting it by heat treatment to form an oxide superconductor. It has been known.

In addition, in the superconducting material obtained by the above-mentioned manufacturing method,
For example, it is known that a Y-Ba-Cu-0 system mixed in a ratio of Y:Ba:Cu = 1:2:3 has a critical temperature of about 90°C.

Furthermore, the Y-Ba-Cu-0 based superconducting material is
The properties of the oxygen-deficient perovskite structure, especially the orthorhombic structure in which oxygen atoms are located at specific positions in the crystal lattice, are excellent, so the heat treatment atmosphere for producing the superconducting material is It is known that superconducting materials with excellent properties can be stably produced by selecting an atmosphere containing oxygen gas and supplying sufficient oxygen during heat treatment.

By the way, in the conventional method of heat-treating the mixed powder or molded body, as shown in FIGS. 4 and 5, a precursor 1 such as a raw material powder or a molded body is placed in a boat-shaped container 2. put the container 2 into the heating furnace 3,
A common method is to heat it by blowing oxygen gas into it.

[Problem that the invention seeks to solve]

However, the flow resistance of the oxygen gas is higher when it passes through the space between the container 2 and the furnace wall of the heating furnace 3 than when it passes through the gap between the precursor 1 and the platform where the heat treatment was performed using this method. Because of its small size, the precursor 1 mainly flows around the container 2 and is discharged as shown by the arrow in FIG. 5 inside the heating furnace.
It is known that it does not flow sufficiently through the gap between... Therefore, not only is the amount of oxygen contributing to the sintering reaction of the building block 1 insufficient, making it impossible to produce a superconductor with excellent properties, but also the properties of the produced superconductor may partially differ depending on the oxygen supply, resulting in There was a problem that the quality of the product deteriorated.

Furthermore, if the flow rate of oxygen gas supplied to the heating furnace 3 is increased in order to increase the acid system that contributes to the reaction, not only will the consumption of oxygen gas increase, but also the oxygen gas will transfer the heat inside the heating furnace 3 to the outside. This has the drawback of lowering the thermal efficiency of the heating furnace and increasing fuel costs. Furthermore, even if the precursor 1 is coarsely pulverized to enlarge the pores between the pulverized particles so that the oxygen gas can easily pass through the pores between the precursors 1 and 2, most of the oxygen gas is transferred to the container 2 and heated. It has been found that the liquid flows through the furnace walls of the furnace 3.

In order to solve the above problems, the present invention aims to solve the above problems.
-O (However, A is SC, Y, Ce, Yb.

1 of Group 11a elements of the periodic table such as Er, Ho, Dy, etc.
The oxide superconductor contains the elements constituting the oxide superconductor shown in Table 1 (B represents one or more elements of the fla group of the periodic table, such as Ca, 3r, 3a, etc.), and can be made into an oxide superconductor by heat treatment. A powdered, granular, or lumpy precursor is prepared, and a hollow container equipped with a gas inlet [1] and an outlet is filled with the precursor, and a gas containing oxygen is introduced into the container from the inlet. After passing through the gaps between the precursors inside the feeding container, the precursors are discharged from the outlet and the inside of the container is heated to heat-treat the precursors.

[For production]

Since the hollow container is filled with a precursor and the oxygen-containing gas is passed through the container, the oxygen gas reliably passes through the gaps between the precursors. Therefore, oxygen is uniformly and sufficiently supplied to the precursor during heat treatment, and a superconducting material with stable quality is produced.

The present invention will be explained in more detail below.

To produce an oxide superconducting material by applying the method of the present invention, first, raw material powder is prepared. This raw material powder is one containing elements constituting the oxide superconducting material, and the period is 11! A mixed powder consisting of a powder containing a group 1ea element in Table 1, a powder containing a group 1a element of the periodic table, and a copper oxide powder, or a powder obtained by calcining this mixed powder is used.

Periodic Table 1 used here [As group a element powder, Sc
, Y, La, Ce, Pr, Nd, Pm, S
m.

Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb.

Carbonate powder, oxide powder, chloride powder of each element of lu,
Compound powders such as sulfide powders and fluoride powders or alloy powders, and powders of Group Ia elements of the periodic table.
Carbonate powder, oxide powder, chloride powder, sulfide powder of each element Be, Ca, Ma-, Bo, Sr,
These include compound powders such as fluoride powders, or alloy powders. Further, as the copper oxide powder, CIO, Cu
20. Copper oxide powders such as CO203 and Cu403 powders are used.

Then, raw material powder is prepared using these powders, and this raw material powder is used as al! I! For IJ, one type each can be selected from the periodic table 1EA group element powder and the periodic table 1 [a group element powder, or two or more types can be selected. Further, such raw material powder may be purified by a method such as a coprecipitation method or a sol-gel method.

In addition, when carbonate or carbon content is contained in these raw material powders, the raw material powders are subjected to a calcining treatment.

This calcining treatment is performed to thermally decompose the carbonate or carbon content in the raw material powder into an oxide, and is usually
It is preferable to perform heating treatment at a temperature of 0 to 950° C. for about 1 to 100 hours as many times as necessary.

Next, the raw material powder obtained in this manner is molded using a pressure means such as hydrostatic pressing, and then this molded body is coarsely pulverized to form coarse particles with a particle diameter of several culms (Fig. 1). A precursor 10 as shown is obtained. Next, this precursor 10 is filled into a container 11 shown in FIG.

The container 11 is cylindrical and made of a heat-resistant material such as high-purity alumina, and a net 12 having a mesh smaller than the particle size of the precursor 10 can be attached to the bottom of the container 11 . Note that the upper and lower parts of the container 11 are open,
The lower opening is the gas inlet 11a and the upper opening is the exhaust port 11.
It has become b.

Once the net 12 is attached to the bottom of the container 11, the precursor 10 is filled above the net 12.

Next, this container 11 is placed in a vertical heating furnace.

Then, oxygen gas is supplied to the container 1 from the inlet 11a of the container 11.
The precursor 10 inside the container 11 is forcibly blown into the interior of the container 11 by a vertical furnace, and the oxygen gas is passed through the gap between the precursors 10 and discharged from the exhaust port 11b.
... to 850 to 1100°C for about 1 to 100 hours, and when the heat treatment is completed, the precursor 10
Cool slowly to air temperature. Through the above treatment, each element inside the precursor 10 undergoes a diffusion reaction and an oxide superconductor is produced.

In the heat treatment process described above, after the oxygen gas blown into the interior of the container 2S11 passes through the net 12, the precursor 10
Since the oxygen gas passes through the gaps between the precursors 10 and is then exhausted from the exhaust port 11b, the oxygen gas reliably passes through the gaps between the precursors 10 and the precursors 10 have sufficient free oxygen. You will have to react in person. This improves the production efficiency of superconductors, making it possible to obtain superconducting materials of uniform quality, while also making it possible to shorten the time required for heat treatment, which has the effect of reducing manufacturing costs.Also, Because superconductors can be produced efficiently in this way, the flow rate of oxygen gas can be lower than when using a conventional horizontal furnace, which reduces production costs by reducing the amount of expensive oxygen gas used. In addition, since the flow ω of oxygen gas can be reduced, the amount of heat taken from the heating furnace by the oxygen gas can be reduced, and the thermal efficiency of the heating furnace is improved.

N/13, the position of the inlet port 11a and the exhaust port 11b may be reversed, and the oxygen may flow downward.

The oxide superconducting material produced as described above is filled into a metal tube and used to produce a #IA conductive wire, or to form a superconducting thin film by compressing the superconducting material and subjecting it to heat treatment. Sputtering target for formation
J3! It is also used for superconducting grass roots, etc., which is formed by screen printing a superconducting paste made by dispersing superconducting powder in a vehicle on a substrate or the like.

In the example 43 of J3, previous) E, a cylindrical container was used as the container to be filled with the precursor 10, but the shape of the container 11 is not limited to the cylindrical shape. Any shape may be used as long as it has an opening 11b and can be filled with the precursor 10.

[Example 1] Y2O3 powder, BaCuz powder, and CuO powder were mixed into Y:
Mix in a ratio of Ba:Cu=1:2:3,
This mixed powder was calcined by heating at 925° C. for 12 hours, and then molded by an isostatic pressing method. Next, this compact was coarsely pulverized to a particle size of 2 to 511Il11, and then filled into an alumina porcelain tubular container having an inner diameter of 100 mrrr.

At this time, a platinum net was attached to the bottom of the tubular container so that the coarse particles could be held by this net. Next, the tube container was placed in an upright position so that the net was on the lower side, and inserted into a vertical electric furnace.W gas was fed into the electric furnace at a rate of 5 nozzles per minute, and heated at 950°C. Heat treatment was performed by heating for 24 hours. After the heating was completed, the mixture was slowly cooled for 20 hours to obtain an oxide superconducting material.

When the critical temperature characteristics of this oxide superconducting material were measured by an electrical resistance method, the electrical resistance became zero at 93° C. as shown by curve A in FIG. In addition, using a precursor having the same composition as the above precursor, it was stored in a boat-shaped container in a conventional horizontal furnace and heat-treated (the obtained oxide superconducting material was The critical temperature characteristics were shown.

As is clear from the comparison of the two, the superconducting material fabricated using the method of the present invention is superior to that fabricated using the conventional method! It was revealed that the ins temperature range was narrower than that of the superconducting material produced in No. 11, and that the superconducting material was homogeneous and had high characteristics.

In addition, when the critical temperature characteristics of the aforementioned oxide superconducting material were measured by the AC inductance method, the results shown in curve C in Figure 3 were obtained, and the super T1 conductive material obtained under the same heat treatment conditions in a normal horizontal furnace was obtained. It was found that a narrower transition temperature width was obtained compared to the broken line 1] indicating the characteristics of the material, and that a homogeneous superconducting material with high characteristics was obtained.

[Example 2] A superconductor precursor powder prepared by a coprecipitation method was calcined at 550°C, further crushed, and after isostatic pressing, coarsely crushed again to obtain particles with a particle size of 2 to 5 #11. I got it.

This granule was placed in the same vertical furnace as that used in Example 1, and heat-treated at 950°C for 20 hours while flowing oxygen at a rate of 1 minute per minute. A superconducting material was obtained by cooling.

The obtained superconducting material exhibited a critical temperature of 93K. Note that this critical temperature is the same value as the critical temperature of a superconducting material obtained by heat-treating the same precursor as above in a conventional horizontal furnace under the same condition while flowing 5 J/min of oxygen. Therefore, it has been found that by carrying out the method of the present invention, it is possible to reduce the amount of oxygen gas supplied during heat treatment.

[Example 3] 20g Y powder, 3a CO3 powder, and CuO powder
:Ba:Cu=1:2:3 mixed powder was subjected to isostatic pressing and coarsely pulverized to obtain coarse particles of 2 to 5 al. The coarse particles were placed in the same vertical furnace as in Example 1, and heat-treated at 950°C for 24 hours while flowing oxygen at a rate of 2'' per minute.
After cooling for 0 hours, an oxide superconducting material was obtained.

The oxide superconducting material produced in this example showed the same critical temperature characteristics as the superconducting material produced by repeating the same heat treatment three times in a conventional horizontal furnace.

That is, it has been revealed that by implementing the method of the present invention, superconducting materials can be produced more efficiently than conventional methods.

(Effects of the Invention) As explained above, the present invention is characterized in that a powdered, granular or lumpy precursor of an oxide superconductor is filled into a hollow container, and a gas containing oxygen is introduced from the inlet of the container to form the precursor. Since this is a method of heat treatment while passing through the voids between the precursors, the elements inside the precursor can be efficiently reacted with sufficient oxygen, making it possible to produce homogeneous oxide superconducting materials. In addition, since the oxygen-containing gas is forced to pass through the gaps between the precursors, the number of M devices used during heat treatment can be reduced and the heat treatment time can be shortened compared to conventional methods. This has the effect of reducing the manufacturing cost of oxide superconducting materials.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an example of a container used to carry out the present invention, FIG. Figure 3 shows the critical temperature characteristics of the oxide superconducting material produced in Example 1 measured by the inductance method, and Figures 4 and 5
The figures show the state in which a precursor is installed inside a heating furnace in a conventional method, with FIG. 4 being a cross-sectional view and FIG. 5 being a longitudinal cross-sectional view. 10... Precursor, 11... Container, 11a... Inlet port, 11b...
Outlet, 12... Net body.

Claims (1)

[Claims] A-B-Cu-O (where A is Sc, Y, Cc, Yb
, Er, Ho, Dy, etc., and B represents one or more elements of Group IIa of the periodic table, such as Ca, Sr, Ba, etc.
A powdered, granular, or lumpy precursor containing an element constituting an oxide superconductor represented by one or more of group elements) and which becomes an oxide superconductor by heat treatment is prepared, and a gaseous precursor is prepared. A hollow container equipped with an inlet and an outlet is filled with a precursor, and a gas containing oxygen is introduced into the container from the inlet and passes through the gap between the precursors inside the container, and then from the outlet. A method for producing an oxide superconducting material, which comprises discharging the precursor and heat-treating the precursor by heating the inside of the container.