Method for manufacturing oxide superconducting article

A method for manufacturing a superconducting article, comprising the steps of: forming a first layer comprising a mixture of LnBa.sub.2 Cu.sub.3 O.sub.x and Ln.sub.2 BaC oxid, on the surface of a substrate, said Ln being an optional rare earth element; then locally and sequentially/heating and melting the first layer to locally and sequentially form a molten pool of the mixture of the first layer, and causing the molten pool of the first layer to locally and sequentially solidify, thereby arranging the a-b plane of the crystal of the mixture of the first layer in parallel with the surface of the substrate; then forming a second layer comprising a mixture of at least CuO and BaCuO.sub.2 on the surface of the first layer; and then melting the mixture of the second layer to cause the resultant melt of the mixture of the second layer to diffusion-react with Ln.sub.2 BaCu oxide, in the first layer so as to convert the first and second into a film of a superconducting substance comprising LnBa.sub.2 Cu.sub.3 O.sub.x, in which the a-b plane of the crystal thereof is arranged in parallel with the surface of the substrate; thereby manufacturing a superconducting article comprising the substrate and the film of the superconducting substance formed on the surface of the substrate.

REFERENCE TO PATENTS, APPLICATIONS AND PUBLICATIONS PERTINENT TO THE 
INVENTION 
As far as we know, there is available the following prior art document 
pertinent to the present invention: 
"Japanese Journal of Applied Physics", Vol. 27, No. 8, pages L1501-L1503, 
published on Jul. 22, 1988. 
The contents of the prior art disclosed in the above-mentioned prior art 
document will be discussed hereafter under the heading of the "BACKGROUND 
OF THE INVENTION". 
FIELD OF THE INVENTION 
The present invention relates to a method for manufacturing a 
superconducting article comprising a substrate and a film of a 
superconducting substance formed on the surface of the substrate. 
BACKGROUND OF THE INVENTION 
Superconducting materials have already been practically applied in the form 
of a superconducting magnet in a particle accelerator, a medical 
diagnosing instrument and the like. Potential applications of the 
superconducting materials include an electric power generator, an energy 
storage device, a linear motor car, a magnetic separator, a nuclear fusion 
reactor, a power transmission cable, and a magnetic shielder. In addition, 
a superconducting element using the Josephson effect is expected to be 
applied in such fields as an ultra-high speed computer, an infrared sensor 
and a low-noise amplifier. The magnitude of the industrial and social 
impacts which would be exerted upon the practical realization of these 
applications, is really unmeasurable. 
One of the typical superconducting materials so far developed is an Nb-Ti 
alloy which is widely used at present as a magnetizing wire. The Nb-Ti 
alloy has a critical temperature, i.e., a critical temperature from which 
a superconductive state occurs (hereinafter simply referred to as "Tc") of 
9K. As a superconducting material having a "Tc" considerably higher than 
that of the Nb-Ti alloy, a compound-type superconducting material has been 
developed, including an Nb.sub.3 Sn (Tc: 18K) and V.sub.3 Ga (Tc: 15K) 
which are now practically employed in the form of wire. 
As a superconducting material having a "Tc" further higher than those of 
the above-mentioned alloy-type and compound-type superconducting 
materials, a composite oxide type superconducting material containing a 
Cu.sub.x O.sub.y -radical has recently been developed. For example, a 
Y-Ba-Cu-O type superconducting material has a "Tc" of about 93K. Since 
liquid nitrogen has a temperature of 77K, liquid nitrogen available at a 
lower cost than liquid helium can be used as a cooling medium for the 
composite oxide type superconducting material. Development of a 
superconducting material having a high "Tc" applicable at a temperature of 
liquid nitrogen urges further expectations for the foregoing fields of 
application. In the actual application, however, problems are how to 
process a superconducting material in the form of a film or a wire, and at 
the same time, how to increase a critical current density (hereinafter 
simply referred to as "Jc") of the superconducting material. 
In order to increase the "Jc" of a superconducting material, it is 
necessary, when using the superconducting material in the form of a film, 
to make the structure of the film dense with a single superconducting 
phase. 
A method for manufacturing a superconducting article, in which the "Jc" of 
a film of a superconducting material can be increased by making the 
structure of the film of the superconducting material dense with a single 
superconducting phase, is disclosed in the "Japanese Journal of Applied 
Physics", Vol. 27, No. 8, pages L1501-L1503, published on Jul. 22, 1988 
(hereinafter referred to as the "prior art"). The prior art is described 
below with reference to the drawings. 
FIG. 1 is a schematic descriptive view illustrating the former half steps 
of the method of the prior art for manufacturing a superconducting 
article, and FIG. 2 is a schematic descriptive view illustrating the 
latter half steps of the method of the prior art for manufacturing the 
superconducting article. 
First, a sheet-shaped substrate 1 comprising Y.sub.2 BaCu oxide, is 
prepared. Then, a mixture of CuO and BaCO.sub.3, in which the ratio of 
copper (Cu) to barium (Ba) is Cu:Ba=5:3 in molar ratio, is primary-fired 
at a temperature of 800.degree. C. for 24 hours, cooled, and pulverized 
into a powder. The powder of the thus primary-fired mixture is then 
secondary-fired at a temperature of 900.degree. C. for 24 hours, cooled, 
and pulverized into a powder to prepare a powdery material for a film. 
Subsequently, the thus prepared powdery material for a film is mixed with 
ethyl alcohol to prepare a slurry for a film. 
Then, the thus prepared slurry for a film is applied onto the surface of 
the substrate 1, and dried to form a film 2 comprising Ba-Cu oxides on the 
surface of the substrate 1, as shown in FIG. 1. 
Then, the substrate 1, on the surface of which the film 2 has thus been 
formed, is heated in an electric furnace to melt the film 2 to cause the 
resultant melt of the Ba-Cu oxides in the film 2 to diffusion-react with 
Y.sub.2 BaCu oxide, in the substrate 1, thereby converting the film 2 into 
a film 3 of a superconducting substance comprising YBa.sub.2 Cu.sub.3 
O.sub.x, as shown in FIG. 2. 
Then, the film 3 of the superconducting substance thus produced is cooled 
to a room temperature, thereby manufacturing a superconducting article 
comprising a non-reacting substrate 1 and the film 3 of the 
superconducting substance formed on the surface of the non-reacting 
substrate 1, as shown in FIG. 2. 
The above-mentioned prior art has the following effects: Since the film 3 
of the superconducting substance comprising YBa.sub.2 Cu.sub.3 O.sub.x is 
produced through the diffusion-reaction of the resultant melt of the Ba-Cu 
oxides in the film 2 with Y.sub.2 BaCu oxide, in the substrate 1, the 
structure of the film 3 of the superconducting substance is dense with a 
single superconducting phase, thus permitting manufacture of a 
superconducting article having a high "Jc". 
However, the above-mentioned prior art has the following problems: 
(1) When the film 3 of the superconducting substance comprising YBa.sub.2 
Cu.sub.3 O.sub.x is produced on the surface of the substrate 1 through the 
diffusion-reaction of the resultant melt of the Ba-Cu oxides in the film 2 
with Y.sub.2 BaCu oxide, in the substrate 1, the film 3 of the 
superconducting substance expands in volume, causing cracks in the film 3 
of the superconducting substance and resulting in seriously deteriorated 
superconducting properties of the superconducting article including a 
largely decreased "Jc". 
(2) In order to further increase "Jc" of a superconducting article, it is 
necessary to arrange the a-b plane of the crystal of the superconducting 
substance of the film 3 in parallel with the surface of the substrate 1. 
The reason is that the a-b plane of the crystal of the superconducting 
substance permits the easiest flow of electric current. According to the 
above-mentioned prior art, however, the a-b plane of the crystal of the 
superconducting substance of the film 3 shows diverse and various 
orientations. 
The above-mentioned problems (1) and (2) occur also in the case where the 
film 3 of a superconducting substance is produced by means of a compound 
containing an optional rare earth element other than "yttrium" (Y) in the 
above-mentioned Y.sub.2 BaCu oxide and YBa.sub.2 Cu.sub.3 O.sub.x. Such an 
optional rare earth element is hereinafter represented by "Ln". 
SUMMARY OF THE INVENTION 
An object of the present invention is therefore to provide a method for 
manufacturing a superconducting article, which permits prevention, when 
producing a film of a superconducting substance comprising LnBa.sub.2 
Cu.sub.3 O.sub.x on the surface of a substrate through the 
diffusion-reaction, of the occurrence of cracks in the film of the 
superconducting substance, and arrangement of the a-b plane of the crystal 
of the superconducting substance of the film in parallel with the surface 
of the substrate, and as a result allows the manufacture of a 
superconducting article having excellent superconducting properties. 
In accordance with one of the features of the present invention, there is 
provided a method for manufacturing a superconducting article, 
characterized by comprising the steps of: 
forming a first layer comprising a mixture of LnBa.sub.2 Cu.sub.3 O.sub.x 
and Ln.sub.2 BaCu oxide, on the surface of a substrate, said Ln being an 
optional rare earth element, and the content ratio of said Ln.sub.2 BaCu 
oxide in said first layer being within the range of from 5 to 80 wt. % 
relative to the total amount of LnBa.sub.2 Cu.sub.3 O.sub.x and Ln.sub.2 
BaCu oxide; then 
locally and sequentially heating and melting said first layer to locally 
and sequentially form a molten pool of said mixture of said first layer, 
and causing said molten pool of said first layer to locally and 
sequentially solidify, thereby arranging the a-b plane of the crystal of 
said mixture of said first layer in parallel with the surface of said 
substrate; then 
forming a second layer comprising a mixture of at least CuO and BaCuO.sub.2 
on the surface of said first layer, said second layer having a melting 
point within the range of from 800.degree. to 1,000.degree. C., which is 
lower than the melting point of said first layer; then 
melting said mixture of said second layer, and keeping the molten state of 
said second layer for a period of time of from 1 minute to 4 hours in an 
oxygen-containing atmosphere to cause the resultant melt of said mixture 
of said second layer to diffusion-react with Ln.sub.2 BaCu oxide, in said 
first layer, thereby converting said first layer and said second layer 
into a film of a superconducting substance comprising LnBa.sub.2 Cu.sub.3 
O.sub.x, in which the a-b plane of the crystal thereof is rranged in 
parallel with the surface of said substrate; and then 
cooling said film of said superconducting substance thus produced to a room 
temperature, thereby manufacturing a superconducting article comprising 
said substrate and said film of said superconducting substance formed on 
the surface of said substrate.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
From the above-mentioned point of view, extensive studies were carried out 
to develop a method for manufacturing a superconducting article, which 
permits prevention, when producing a film of a superconducting substance 
comprising LnBa.sub.2 Cu.sub.3 O.sub.x on the surface of a substrate 
through the diffusion-reaction, of the occurrence of cracks in the film of 
the superconducting substance, and arrangement of the a-b plane of the 
crystal of the superconducting substance of the film in parallel with the 
surface of the substrate, and as a result allows for the manufacture of a 
superconducting article having excellent superconducting properties. 
As a result, the following findings were obtained: 
(1) Cracks occur in the film of the superconducting substance comprising 
LnBa.sub.2 Cu.sub.3 O.sub.x because the film of the superconducting 
substance expands in volume when the film of the superconducting substance 
comprising LnBa.sub.2 Cu.sub.3 O.sub.x is produced on the surface of the 
substrate through the diffusion-reaction. Cracks can therefore be 
prevented from occurring in the film of the superconducting substance 
comprising LnBa.sub.2 Cu.sub.3 O.sub.x, by reducing the amount of 
LnBa.sub.2 Cu.sub.3 O.sub.x produced through the diffusion-reaction to 
reduce the amount of expansion in volume of the film of the 
superconducting substance comprising LnBa.sub.2 Cu.sub.3 O.sub.x. 
(2) It is possible to arrange the a-b plane of the crystal of the film of a 
superconducting substance comprising LnBa.sub.2 Cu.sub.3 O.sub.x in 
parallel with the surface of the substrate by locally and sequentially 
heating and melting the film, formed on the surface of a substrate, 
comprising a mixture of LnBa.sub.2 Cu.sub.3 O.sub.x and Ln.sub.2 BaCu 
oxide, to locally and sequentially form a molten pool of the mixture of 
the film, and causing the molten pool to locally and sequentially 
solidify. 
The present invention was made on the basis of the above-mentioned findings 
(1) and (2). Now, an embodiment of the method of the present invention for 
manufacturing a superconducting article is described below with reference 
to the drawings. 
FIG. 3 is a schematic descriptive view illustrating a first step in an 
embodiment of the method of the present invention for manufacturing a 
superconducting article; FIG. 4 is a schematic descriptive view 
illustrating a second step in the embodiment of the method of the present 
invention for manufacturing the superconducting article; FIG. 5 is a 
schematic descriptive view illustrating a third step in the embodiment of 
the method of the present invention for manufacturing the superconducting 
article; and FIG. 6 is a schematic descriptive view illustrating a fourth 
step in the embodiment of the method of the present invention for 
manufacturing the superconducting article. 
In the embodiment of the method of the present invention for manufacturing 
a superconducting article, a first layer 5 comprising a mixture of 
LnBa.sub.2 Cu.sub.3 O.sub.x and Ln.sub.2 BaCu oxide, is formed in the 
first place on the surface of a substrate 4, as shown in FIG. 3, by means 
of the known plasma metallizing method or the like. The substrate 4 
comprises any one of ceramics, silver, nickel and a nickel-based alloy, 
which hardly react with a superconducting substance comprising LnBa.sub.2 
Cu.sub.3 x. The content ratio of Ln.sub.2 BaCu oxide, in the first layer 5 
should be within the range of from 5 to 80 wt. % relative to the total 
amount of LnBa.sub.2 Cu.sub.3 O.sub.x and Ln.sub.2 BaCu oxide. 
The content ratio of Ln.sub.2 BaCu oxide, in the first layer is limited 
within the above-mentioned range for the following reason: With a content 
ratio of Ln.sub.2 BaCu oxide, of under 5 wt. %, the amount of Ln.sub.2 
BaCu oxide, in the first layer 5 is insufficient relative to the amount of 
a mixture of a second layer described later, so that a non-reacting 
fraction of the mixture of the second layer remains in a film described 
later of a superconducting substance comprising LnBa.sub.2 Cu.sub.3 
O.sub.x, which film is to be formed on the surface of the substrate 4, 
thus causing deterioration of superconducting properties of the film of 
the superconducting substance. With a content ratio of Ln.sub.2 BaCu 
oxide, of over 80 wt. %, on the other hand, the excessive amount of 
Ln.sub.2 BaCu oxide, makes it impossible to prevent cracks from occurring 
in the film of the superconducting substance comprising LnBa.sub.2 
Cu.sub.3 O.sub.x, which cracks are caused by the expansion in volume of 
the film during formation thereof. 
Then, as shown in FIG. 4, a heater 6 using a laser beam or electric 
resistance heat is installed above the substrate 4. The first layer 5 is 
locally and sequentially heated and melted by continuously moving the 
heater 6 in parallel with the surface of the substrate 4, thereby locally 
and sequentially forming a molten pool 5A of the above-mentioned mixture 
of the first layer 5, and the thus formed molten pool 5A of the mixture of 
the first layer 5 is caused to locally and sequentially solidify. With the 
progress of solidification of the molten pool 5A, Ln.sub.2 BaCu oxide and 
LnBa.sub.2 Cu.sub.3 O.sub.x are recrystallized. The a-b plane of the 
crystal of the thus recrystallized Ln.sub.2 BaCu oxide, and LnBa.sub.2 
Cu.sub.3 O.sub.x grows in parallel with the surface of the substrate 4 
along with the progress of solidification of the molten pool 5A. As a 
result, a reformed first layer 5B is formed, which comprises a mixture of 
Ln.sub.2 BaCu oxide, and LnBa.sub.2 Cu.sub.3 O.sub.x, in which the a-b 
plane of the crystal permitting the easiest flow of electric current is 
arranged in parallel with the surface of the substrate 4, on the surface 
of the substrate 4. Instead of continuously moving the heater 6 in 
parallel with the surface of the substrate 4, the substrate 4 may be 
continuously moved in parallel with the heater 6. 
Then, as shown in FIG. 5, a second layer 7 having a melting point within 
the range of from 800.degree. to 1,000.degree. C. is formed by means of 
the known plasma metallizing method on the surface of the reformed first 
layer 5B. The second layer 7 comprises a mixture of at least CuO and 
BaCu0.sub.2. A typical second layer 7 comprises a mixture of CuO, 
BaCuO.sub.2 and BaO. In this case, the ratio of copper (Cu) to barium (Ba) 
in the second layer 7 should be within the range of Cu:Ba=1:0.10 to 0.95 
in molar ratio. Another example of the second layer 7 comprises a mixture 
of CuO, BaCuO.sub.2, BaO, Y.sub.2 O.sub.3 and YBa.sub.2 Cu.sub.3 O.sub.7. 
In this case, the ratio of copper (Cu) to barium (Ba) and yttrium (Y) in 
the second layer 7 should be within the range of Cu:Ba:Y=1:0.10 to 
0.95:0.001 to 0.330 in molar ratio. Any of these mixtures of the second 
layer 7 diffusion-reacts with Ln.sub.2 BaCu oxide, in the reformed first 
layer 5B, and as a result, the reformed first layer 5B and the second 
layer 7 are converted into a film of a superconducting substance 
comprising LnBa.sub.2 Cu.sub.3 O.sub.x, as described below. 
Then, the mixture of the second layer 7 is melted, and the molten state of 
the second layer 7 is kept for a period of time of from 1 minute to 4 
hours in an oxygen-containing atmosphere to cause the resultant melt of 
the mixture comprising at least CuO and BaCuO.sub.2 of the second layer 7 
to diffusion-react with Ln.sub.2 BaCu oxide, in the reformed first layer 
5B, thereby converting the reformed first layer 5B and the second layer 7 
into a film 8 of a superconducting substance comprising LnBa.sub.2 
Cu.sub.3 O.sub.x, as shown in FIG. 6. The arrangement of the a-b plane of 
the crystal of the mixture comprising Ln.sub.2 BaCu oxide, and LnBa.sub.2 
Cu.sub.3 O.sub.x of the reformed first layer 5B is never transformed even 
by the above-mentioned diffusion-reaction. Therefore, there is formed, on 
the surface of the substrate 4, the film 8 of the superconducting 
substance comprising LnBa.sub.2 Cu.sub.3 O.sub.x, in which the a-b plane 
of the crystal is arranged in parallel with the surface of the substrate 
4. 
The period of time of keeping the molten state of the second layer 7 is 
limited within the range of from 1 minute to 4 hours for the following 
reason: With a period of time of the molten state of the second layer 7 of 
under 1 minute, the resultant melt of the mixture of the second layer 7 
cannot be caused to sufficiently diffusion-react with Ln.sub.2 BaCu oxide, 
in the reformed first layer 5B. With a period of time of the molten state 
of the second layer 7 of over 4 hours, on the other hand, conversion of 
the reformed first layer 5B and the second layer 7 into the film 8 of the 
superconducting substance comprising LnBa.sub.2 Cu.sub.3 O.sub.x does not 
progress further. 
The thus produced film 8 of the superconducting substance is then cooled to 
a room temperature, thereby manufacturing a superconducting article 
comprising, as shown in FIG. 6, the substrate 4 and the film 8 of the 
superconducting substance formed on the surface of the substrate 4. 
According to the embodiment of the method of the present invention for 
manufacturing a superconducting article, as described above, the reformed 
first layer 5B previously contains LnBa.sub.2 Cu.sub.3 O.sub.x in a 
prescribed amount, and this reduces the amount of LnBa.sub.2 Cu.sub.3 
O.sub.x produced through the diffusion-reaction of the melt of the mixture 
of the second layer 7 with Ln.sub.2 BaCu oxide, in the reformed first 
layer 5B. As a result, the amount of expansion in volume of the film 8 of 
the superconducting substance comprising LnBa.sub.2 Cu.sub.3 O.sub.x is 
reduced, thus preventing cracks from occurring in the film 8 of the 
superconducting substance. In addition, since the a-b plane of the crystal 
of the superconducting substance comprising LnBa.sub.2 Cu.sub.3 O.sub.x of 
the film 8 formed on the surface of the substrate 4 is arranged in 
parallel with the surface of the substrate 4, it is possible to 
manufacture a superconducting article having a very high "Jc". 
Now, the method of the present invention for manufacturing a 
superconducting article is described in more detail by means of examples 
with reference to FIGS. 3 to 6. 
EXAMPLE 1 
A mixture comprising CuO, BaCO.sub.3 and Y.sub.2 O.sub.3, in which the 
ratio of copper (Cu) to barium (Ba) and yttrium (Y) was Cu:Ba:Y=2:1.5:1.5 
in molar ratio, was primary-fired at a temperature of 900.degree. C. for 
10 hours, cooled and pulverized into a powder. The powder of the thus 
primary-fired mixture was then secondary-fired at a temperature of 
920.degree. C. for 10 hours, cooled and pulverized into a powder. The 
powder of the thus secondary-fired mixture was then tertiary-fired at a 
temperature of 950.degree. C. for 10 hours, cooled and pulverized into a 
powder to prepare a powdery material for a first layer, having an average 
particle size within the range of from 26 to 44 .mu.m. The thus prepared 
powdery material for the first layer comprised a mixture of YBa.sub.2 
Cu.sub.3 O.sub.x and Y.sub.2 BaCu oxide, and the content ratio of Y.sub.2 
BaCu oxide, in the powdery material for the first layer was 40 wt. % 
relative to the total amount of YBa.sub.2 Cu.sub.3 O.sub.x and Y.sub.2 
BaCu oxide. 
On the other hand, a mixture comprising CuO and BaCO.sub.3, in which the 
ratio of copper (Cu) to barium (Ba) was Cu:Ba=2:1 in molar ratio, was 
primary-fired at a temperature of 900.degree. C. for 10 hours, cooled and 
pulverized into a powder. The powder of the thus primary-fired mixture was 
then secondary-fired at a temperature of 920.degree. C. for 10 hours, 
cooled and pulverized into a powder. The powder of the thus 
secondary-fired mixture was then tertiary-fired at a temperature of 
950.degree. C. for 30 minutes, cooled and pulverized into a powder to 
prepare a powdery material for second layer, having an average particle 
size within the range of from 26 to 44 .mu.m. The thus prepared powdery 
material for the second layer comprised a mixture of CuO, BaCuO.sub.2 and 
BaO. 
Then, the powdery material for the first layer prepared as described above 
was blown by means of the known plasma metallizing method onto the surface 
of a substrate 4 comprising a nickel-based alloy and having a surface area 
of 1 cm.sup.2 and a thickness of 1 mm, to form a first layer 5 having a 
thickness of 50 .mu.m on the surface of the substrate 4, as shown in FIG. 
3. 
Then, as shown in FIG. 4, a heater 6 comprising a laser beam source having 
an output of 0.5 KW was installed above the substrate 4, and the heater 6 
was continuously and horizontally moved in parallel with the surface of 
the substrate 4 at a speed of 1 m/minute while irradiating a laser beam 
from the heater 6 onto the first layer 5 formed on the surface of the 
substrate 4. As a result, the first layer 5 was locally and sequentially 
heated and melted to locally and sequentially form a molten pool 5A of the 
mixture comprising YBa.sub.2 Cu.sub.3 O.sub.x and Y.sub.2 BaCu oxide, of 
the first layer 5 on the surface of the substrate 4, and the thus formed 
molten pool 5A of the above-mentioned mixture of the first layer 5 was 
locally and sequentially solidified. Consequently, a reformed first layer 
5B comprising the above-mentioned mixture, in which the a-b plane of the 
crystal permitting the easiest flow of electric current was arranged in 
parallel with the surface of the substrate 4, was formed on the surface of 
the substrate 4. 
Then, the powdery material for the second layer prepared as described above 
was blown by means of the known plasma metallizing method onto the surface 
of the reformed first layer 5B, to form a second layer 7 having a 
thickness of 50 .mu.m on the surface of the reformed first layer 5B, as 
shown in FIG. 5. 
Then, the substrate 4, on the surface of which the reformed first layer 5B 
and the second layer 7 were thus formed, was heated to a temperature of 
950.degree. C. in an electric furnace having an interior atmosphere of air 
to melt the second layer 7, and the molten state of the second layer 7 was 
kept for 30 minutes. This permitted the diffusion-reaction of the 
resultant melt of the mixture comprising CuO, BaCuO.sub.2 and BaO of the 
second layer 7 with Y.sub.2 BaCu oxide, in the reformed first layer 5B, 
whereby the reformed first layer 5B and the second layer 7 were converted 
into a film 8 of a superconducting substance comprising YBa.sub.2 Cu.sub.3 
O.sub.x having a thickness of 70 .mu.m, as shown in FIG. 6. 
The substrate 4, on the surface of which the film 8 of the superconducting 
substance was thus produced, was slowly cooled in an electric furnace to a 
room temperature. 
Thus, a superconducting article was manufactured, which comprised the 
substrate 4 comprising a nickel-based alloy and the film 8 of the 
superconducting substance comprising YBa.sub.2 Cu.sub.3 O.sub.x, the a-b 
plane of the crystal of which was arranged in parallel with the surface of 
the substrate 4, formed on the surface of the substrate 4, as shown in 
FIG. 6. 
Investigation of the thus manufactured superconducting article revealed 
that the structure of the film 8 of the superconducting substance was 
dense with a single superconducting phase, and the superconducting article 
had a "Jc" of 3,200 A/cm.sup.2. 
EXAMPLE 2 
A mixture comprising CuO, BaCO.sub.3 and Y.sub.2 O.sub.3, in which the 
ratio of copper (Cu) to barium (Ba) and yttrium (Y) was 
Cu:Ba:Y=2.4:1.7:1.3 in molar ratio, was primary-fired at a temperature of 
900.degree. C. for 10 hours, cooled and pulverized into a powder. The 
powder of the thus primary-fired mixture was then secondary-fired at a 
temperature of 920.degree. C. for 10 hours, cooled and pulverized into a 
powder. The powder of the thus secondary-fired mixture was then 
tertiary-fired at a temperature of 950.degree. C. for 10 hours, cooled and 
pulverized into a powder to prepare a powdery material for a first layer, 
having an average particle size within the range of from 26 to 44 .mu.m. 
The thus prepared powdery material for the first layer comprised a mixture 
of YBa.sub.2 Cu.sub.3 O.sub.x and Y.sub.2 BaCu oxide, and the content 
ratio of Y.sub.2 BaCu oxide, in the powdery material for first layer was 
25 wt. % relative to the total amount of YBa.sub.2 Cu.sub.3 O.sub.x and 
Y.sub.2 BaCu oxide. 
On the other hand, a mixture comprising CuO, BaCO.sub.3 and Y.sub.2 
O.sub.3, in which the ratio of copper (Cu) to barium (Ba) and yttrium (Y) 
was Cu:Ba:Y=26:13:1 in molar ratio, was primary-fired at a temperature of 
900.degree. C. for 10 hours, cooled and pulverized into a powder. The 
powder of the thus primary-fired mixture was then secondary-fired at a 
temperature of 920.degree. C. for 10 hours, cooled and pulverized into a 
powder. The powder of the thus secondary-fired mixture was then 
tertiary-fired at a temperature of 950.degree. C. for 30 minutes, cooled 
and pulverized into a powder to prepare a powdery material for a second 
layer, having an average particle size within the range of from 26 to 44 
.mu.m. The thus prepared powdery material for the second layer comprised a 
mixture of CuO, BaCuO.sub.2, BaO, Y.sub.2 O.sub.3 and YBa.sub.2 Cu.sub.3 
O.sub.7. 
Then, the powdery material for the first layer prepared as described above 
was blown by means of the known plasma metallizing method onto the surface 
of a substrate 4 comprising a nickel-based alloy and having a surface area 
of 1 cm.sup.2 and a thickness of 1 mm, to form a first layer 5 having a 
thickness of 50 .mu.m on the surface of the substrate 4, as shown in FIG. 
3. 
Then, as shown in FIG. 4, a heater 6 comprising a laser beam source having 
an output of 0.5 KW was installed above the substrate 4, and the heater 6 
was continuously and horizontally moved in parallel with the surface of 
the substrate 4 at a speed of 1 m/minute while irradiating a laser beam 
from the heater 6 onto the first layer 5 formed on the surface of the 
substrate 4. As a result, the first layer 5 was locally and sequentially 
heated and melted to locally and sequentially form a molten pool 5A of the 
mixture comprising YBa.sub.2 Cu.sub.3 O.sub.x and Y.sub.2 BaCu oxide, of 
the first layer 5 on the surface of the substrate 4, and the thus formed 
molten pool 5A of the above-mentioned mixture of the first layer 5 was 
locally and sequentially solidified. Consequently, a reformed first layer 
5B comprising the above-mentioned mixture, in which the a-b plane of the 
crystal permitting the easiest flow of electric current was arranged in 
parallel with the surface of the substrate 4, was formed on the surface of 
the substrate 4. 
Then, the powdery material for the second layer prepared as described above 
was blown by means of the known plasma metallizing method onto the surface 
of the reformed first layer 5B, to form a second layer 7 having a 
thickness of 50 .mu.m on the surface of the reformed first layer 5B, as 
shown in FIG. 5. 
Then, the substrate 4, on the surface of which the reformed first layer 5B 
and the second layer 7 were thus formed, was heated to a temperature of 
950.degree. C. in an electric furnace having an interior atmosphere of air 
to melt the second layer 7, and the molten state of the second layer 7 was 
kept for 30 minutes. This permitted the diffusion-reaction of the 
resultant melt of the mixture comprising CuO, BaCuO.sub.2, BaO, Y.sub.2 
O.sub.3 and YBa.sub.2 Cu.sub.3 O.sub.7 of the second layer 7 with Y.sub.2 
BaCu oxide in the reformed first layer 5B, whereby the reformed first 
layer 5B and the second layer 7 were converted into a film 8 of a 
superconducting substance comprising YBa.sub.2 Cu.sub.3 O.sub.x having a 
thickness of 70 .mu.m, as shown in FIG. 6. 
Then, the substrate 4, on the surface of which the film 8 of the 
superconducting substance was thus produced, was slowly cooled in the 
electric furnace to a room temperature. 
Thus, a superconducting article was manufactured, which comprised the 
substrate 4 comprising a nickel-based alloy and the film 8 of the 
superconducting substance comprising YBa.sub.2 Cu.sub.3 O.sub.x, the a-b 
plane of the crystal of which was arranged in parallel with the surface of 
the substrate 4, formed on the surface of the substrate 4, as shown in 
FIG. 6. 
Investigation of the thus manufactured superconducting article revealed 
that the structure of the film 8 of the superconducting substance was 
dense with a single superconducting phase, and the superconducting article 
had a "Jc" of 3,300 A/cm.sup.2. 
According to the method of the present invention, as described above in 
detail, it is possible to manufacture a superconducting article having 
excellent superconducting properties, in which, when a film of a 
superconducting substance comprising LnBa.sub.2 Cu.sub.3 O.sub.x is 
produced on the surface of a substrate through the diffusion-reaction, 
cracks are prevented from occurring in the film of the superconducting 
substance, and the a-b plane of the crystal of the superconducting 
substance of the film is arranged in parallel with the surface of the 
substrate, thus providing industrially useful effects.