JPH0269320A - Production of thallium type superconductor - Google Patents

Abstract

PURPOSE:To obtain a Tl type superconductor having high critical temp. and high critical current density by heat-treating a laminated body contg. all components of Tl, Ca, Ba, Cu, end O by laminating layers contg. Tl2O3, CaO, and a Ba-Cu compd. CONSTITUTION:A laminated body contg. all components for Tf, Ca, Ba, Cu, and O is prepd. by laminating >=2 layers contg. one or two among Tl2O3, CaO, and a Ba-Cu compd. in each layer. Each element is diffused by heat-treating the laminated body to obtain a target superconductor having a compsn. for providing a Tl-Ca-Ba-Cu-O type superconductor. A Tl-Ca-Ba-Cu-O type oxide superconductor having a critical temp. >=100K and high critical current density is obtd. by the above described method by diffusing each element and allowing each element to react with each other. Since the thickness of each layer can be regulated to a desired value, the proportion of Tl, Ca, Ba, Cu can be adjusted desirably and an oxide superconductor having superior characteristics is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method for producing a Tl-based superconductor, which is known to have a high critical temperature.

"Prior Art" In recent years, various oxide-based super II conductors have been discovered whose critical temperature (T c ) when transitioning from a normal conducting state to a super W1 conducting state exceeds the liquid nitrogen temperature. This type of oxide superconductor is based on Y-B a-Cu-0 or Bi
-S r-Ca-Cu-0-based oxides, etc. Y-Ba-Cu-0-based superconductors exhibit a critical temperature of over 90K, and B i-S r-Ca-Cu −
It is known that 0-series superconductors exhibit a critical temperature of over 100K.

``Problems to be Solved by the Invention'' However, recently, A. M. Hermann et al. of the University of Arkansas in the United States have discovered that the electrical resistance of T I-Ca- It has become clear that a B a-Cu-0-based superconductor has been discovered, and based on this knowledge, research institutions around the world are proceeding with research to produce Tl-based superconductors.

This Tl-based oxide superconductor was developed by Heraann et al.
NATtlRE VOL! 321G MARCll 1
As is clear from the contents published in 988 and other publications, TltCa+, sBa+Cu5Os, s+X (T
c=103K), T l*G atB al Cuao
X (T c = 106K), T ImC
atB atc uao X (T c=
102K), which shows the composition and critical temperature.

As explained above, various oxide superconductors are being discovered, but it is desirable for superconductors to have low resistance at higher temperatures and to exhibit a higher critical current density. Various manufacturing methods have been attempted to improve the critical temperature and critical current density of the Tl-based oxide superconductor.

The present invention was made in view of the above background, and an object of the present invention is to provide a method for manufacturing a Tl-based oxide superconductor having a high critical temperature and high critical current density.

"Means for Solving the Problems" In order to solve the problems, the present invention uses TlzOs and Ca.
Tl, Ca, Ba, Cu, and O by laminating two or more layers containing one or two of O and Ba-Cu compounds.
By creating a laminate having all of the above and heat-treating this laminate to diffuse each element, T I-Ca-B
This produces an oxide superconductor having a composition of a-Cu-0.

"Effect" T1.0, each element of CaO and B a-Cu compound diffuses and reacts between each layer of the laminate, resulting in T I-Ca-B a
An oxide superconducting layer having a composition of -Cu-0 is generated.

"Example" FIGS. 1 and 2 are for explaining a first example of the present invention. In this example, a B a -Cu compound layer 1 is formed, and this compound layer 1 is formed. On top, Ca0 layer 2 and Tl2
03 Layers 3 are sequentially laminated to form the laminate shown in FIG.

To form the compound layer 1, a Ba-Cu compound is deposited on a core material such as a substrate or a wire using various methods such as CVD (chemical vapor deposition), physical vapor deposition such as sputtering, and thermal spraying. It can be created by forming a layer consisting of. Note that when forming the Ba-Cu compound II, B jl! CusO5 powder, Ba+C
A paste-like coating liquid may be prepared by dispersing u*04 powder or the like in a vehicle, and this may be applied onto the substrate by screen printing, spray coating, or the like. In addition, Ca0 layer 2 and T LO, X! The screen printing method described above can also be used to form J3.

Note that the paste can be manufactured by the method described below.

First, BatCu3 was used as a powder to be dispersed in a vehicle.
When using 0g powder, Ba:Cu:O=2+
B a COy powder and CuO powder are weighed and mixed so that 3=5, and this mixed powder is calcined by heating at 500 to 1000°C for several hours to several IO hours in an oxygen gas atmosphere. The calcined material may be pulverized to make the particle size uniform. Also, as a powder, Ba+Ct+sO+
When powder is used, BaCO5 powder and CuO powder are weighed so that the ratio of Ba2Cu:0 is 1:3:4, and the same treatment as above is performed. The vehicle for dispersing these powders may be a mixture of a hydrophilic binder such as polyvinyl alcohol or polyethylene glycol, or a hydrophobic binder such as ethyl cellulose, polyvinyl acetate, or Chroman resin, as necessary. can.

Once the laminate A is formed, the laminate A is heated to a temperature of 850 to 920 in an oxygen atmosphere such as an oxygen gas stream.
°C, more preferably 0.1 to several 10 at 870 to 890 °C
Heat treatment is performed by heating for a period of time.

Through this heat treatment, the elements contained in each layer 1, 2.3 are destroyed, and each element reacts in the area centered on the Cu0 layer 2, resulting in a composition of Ti a-B a-Cu-0. An oxide superconducting layer as shown in FIG.

is generated, and oxide superconductor B is obtained.

The oxide superconductor B manufactured as described above is B a-
Since the Cu compound layer 1, CuO 12, and each element of the TLOs layer 3 are generated by diffusion reaction, it exhibits a high critical temperature exceeding 100 K and a high critical current density.

In addition, during the Moeki heat treatment, Tl, Ca and [3a and C
Since Tl has the lowest melting point among u, Tl
A portion of the superconducting layer 4 tends to evaporate, and Tl in the generated superconducting layer 4 tends to decrease. Therefore, when creating a laminate, a TlzOs layer 3 is added in order to compensate for the shortage due to the evaporation of Tl.
The Tl shortage can be solved by making the thickness of the layer thicker than other layers.

In addition, by adjusting the thickness of the B a-Cu compound layer I, the thickness of the Ca0 layer 2, and the thickness of T 110 sN 3 to desired values, Tl, Ca, Ba, and C contained in the laminate can be adjusted.
The ratio of u can be set to a desired value, and by adjusting the thickness of each layer, oxide superconductors B with different characteristics can be manufactured.

In addition, in the above example, Ba-Cu compound fil
Ga0 layer 2 and T ItOaJi 3 were formed on top of the Ba-Cu compound layer! on top of 7 ilo sNJ 3
It is also possible to form a laminate by forming Ca0JI2 thereon.

3 and 4 are for explaining a second embodiment of the present invention. In this example, a Ba-Cu compound layer 6
A mixture Fm7 of CaO and Times is formed on this B a-Cu compound layer 6 to create a laminate C shown in FIG.

Next, the laminate C was treated under the same heat treatment conditions as described above.
Heat treated.

Through this heat treatment, 1 mG of the elements of the B a-Cu compound and the elements of the mixed layer 7 are diffused to form T Ica-B a-Cu-0 at the boundary between the B a-Cu compound layer 6 and the mixed layer 7.
By producing the oxide superconducting layer 8 having the following composition, the oxide superconductor shown in FIG. 4 can be obtained.

FIG. 5 and FIG. 6 are for explaining the third embodiment of the present invention, and in this example, Ba-Cu compound and Ca
A mixed FgJ10 of O is formed, and on this mixed layer Ic, T
l□0. Layer 11 is formed to create a laminate E shown in FIG.

Next, the laminate E was processed under the same heat treatment conditions as described above.
Heat treated.

Through this heat treatment, the elements of the mixed layer 10 and Tito, J
By diffusing elements Ill to form a mixed layer IO and a Tlto1 layer I
An oxide superconducting layer I2 having a composition of T I-Ca-B a-Cu-0 is formed at the boundary portion of K, and an oxide superconductor F shown in FIG. 6 can be obtained.

FIGS. 7 and 8 are for explaining the fourth embodiment of the present invention. In this example, CaO 115 is formed, and a mixed Ji 16 consisting of Times and a Ba-Cu compound is formed on this CaO layer 15. A laminate G shown in FIG. 7 is formed by forming the laminate G.

Next, the laminate G was treated under the same heat treatment conditions as described above.
Heat treated.

Through this heat treatment, the elements of Ca0JiI5 and the elements of the mixed layer 16 are diffused, and an oxide superconducting layer I7 having a composition of T I-Ca-B a-Cu-0 is generated at the boundary between the Ca0 layer +5 and the mixed layer 16. As a result, an oxide superconductor (2) shown in FIG. 8 can be obtained.

By carrying out the second to fourth embodiments described above, it is possible to manufacture an oxide superconductor with excellent characteristics as in the first embodiment.

"Manufacturing Example" Four types of W2B bodies were created by forming various layers on an AlvOs substrate using a screen printing method, and these laminates were heated at 880°C for 1 hour in oxygen gas to prepare samples. Oxide superconductors of No. 1 and No. 4 were manufactured. Table 1 shows the results of measuring the critical temperature (Tc) (temperature at zero resistance) and critical current density (Jc) of each of the obtained oxide superconductors. Also, as a comparative example, Times, CaO, and Bat
Table 1 also shows the characteristics of the oxide superconductor of sample No. 5, which was formed by forming a mixed layer of CusOs on a substrate and performing heat treatment under the same conditions as above.

In Table 1, the oxide superconductor shown in diffusion method (a) is B
It was manufactured by forming TltOsl on the a-Cu compound layer and then heat-treating it. Further, in the oxide superconductor shown in the diffusion method (b), as in the case described in the second embodiment, Times and C
It was manufactured by forming a mixed layer of aO and then heat-treating it. The oxide superconductor shown in diffusion method (c) was manufactured by forming a TlmOs layer on a mixed layer of Ba-Cu compound and CaO and then heat-treating it, as in the case described in the third embodiment. be. Further, the oxide superconductor shown in the diffusion method (d) is produced by forming a mixed layer of Tit's and Ba-Cu compound on the CaO layer and then heat-treating the same as described in the fourth embodiment. It was manufactured by

Furthermore, in Table 1, the preparation composition indicates what ratio of Tl, Ba, Ca, and Cu was contained in the entire laminate, and in this example,
The charging composition was adjusted by adjusting the thickness of each layer.

In Table 1, the characteristics of each oxide superconductor are listed as values measured for a 30 μm thick portion of an oxide superconductor layer produced by a diffusion reaction.

From the results shown in Table 1, T I,0, CaO and Ba
Oxide super 7I of sample No. 5 obtained by heat treating a layer in which all tCu=05 were mixed! It was found that the critical current density of the oxide superconductor of sample 1.2.3.4, which was manufactured by diffusing these elements from layers containing each layer, was higher than that of the conductor.

Therefore, it has been revealed that by carrying out the present invention, it is possible to produce a Tica-Ba-C,u-0 based oxide superconductor with a high critical current density.

"Effects of the Invention" As explained above, the present invention has the advantage that Tl5O3, CaO and B
Since heat treatment is applied to a laminate made up of layers containing one or two a-Gu compounds, each element exhibits a critical temperature of 100K or higher by causing a diffusion reaction, and the critical current density is also high. An oxide superconductor having a composition of B a-Cu-0 can be produced. In addition, since the thickness of each layer of the laminate can be set to a desired value, an oxide superconductor with good characteristics can be produced by adjusting the ratio of Tl, Ca, Ba, and Cu to a desired value. There is.

[Brief explanation of the drawing]

1 and 2 show a first embodiment of the present invention. FIG. 1 is a cross-sectional view of a laminate, FIG. 2 is a cross-sectional view of an oxide superconductor, and FIGS. 3 and 4 are a cross-sectional view of an oxide superconductor. Embodiment 2 of the present invention is shown; FIG. 3 is a sectional view of a laminate, FIG. 4 is a sectional view of an oxide superconductor, and FIGS. 5 and 6 are sectional views of a third embodiment of the invention. 5 is a sectional view of the laminate, FIG. 6 is a sectional view of the oxide superconductor, and FIGS. 7 and 8 show a fourth embodiment of the present invention. A cross-sectional view of the laminate, and FIG. 8 is a cross-sectional view of the oxide superconductor. Figure 1 Figure 2 Figure 3 Figure 4 Δ, C, E, G...Laminated body, B, D, F, H... Oxide superconductor, 1- B a-
Cu compound layer, 2-Ca0F3.3...Tl, 0. E
J, 6-Ba-Cu compound layer, 7. Mixed layer, 10... Mixed layer, 1 1-T I2O
s layer, 15-=CaOl, 16... mixed layer, 4.8.12.17... oxide superconducting layer. Figure 5 Figure 6

Claims (1)

[Claims] Two or more layers containing one or two of Tl_2O_3, CaO, and Ba-Cu compounds are laminated to form Tl and C.
A laminate containing all of a, Ba, Cu, and O is created, and this laminate is heat treated to diffuse each element,
A method for producing a Tl-based superconductor, which comprises producing an oxide superconductor having a composition of Tl-Ca-Ba-Cu-O.