Plastically deformable high temperature superconductive material and method of manufacturing formed body thereof

There are disclosed a high temperature superconductive material which can be plastically deformed, processed optionally into predetermined configurations and industrially mass produced and a method of manufacturing a formed body of the high temperature superconductive material. Mixed is a powder raw material which is mainly composed of: 10 to 50 mol % of at least one amide or nitride of alkali metal of Li, Na or K; 10 to 60 mol % of cyanide containing at least one metal selected from aluminum, copper, silver or gold; 5 to 50 mol % of at least one pure metal selected from aluminum, copper, silver or gold; and 10 mol % or less of at least one alkaline earth metal selected from Be, Mg, Ca, Sr or Ba. The powder raw material is pressed, and heated and sintered at the temperature of 673 K to 1553 K. In this manner, obtained is the plastically deformable high temperature superconductive material which can be optionally processed through forging, rolling and the like. Also, the obtained high temperature superconductive material has a critical temperature of 40 K to 80 K and a current density of 10000 A/cm.sup.2 or more.

BACKGROUND OF THE INVENTION 
1. Field of The Invention 
The present invention relates to a high temperature superconductive 
material and a method of manufacturing a formed body of the material. 
The high temperature superconductive material is formed into a 
predetermined configuration through rolling, forging, drawing, extruding 
or another processing, and can broadly be applied to an electric power, 
energy or electronic apparatus and other fields. The invention especially 
relates to a high temperature superconductive material suitable for a 
linear motor car, a high-speed computer, a magnet, an electricity 
generator, an electric motor, power supply, power storage and the like and 
to a method of manufacturing a formed body of the high temperature 
superconductive material. 
2. Prior Art 
A superconductive phenomenon was discovered in the beginning of the 
20.sup.th century, and an oxide superconductor, with which a 
superconductive phenomenon could occur at a high temperature of 30 K, was 
found in 1986. Since then a superconductor field has been enlarged. 
However, the oxide superconductor is not plastically deformable, and has a 
bad workability. By bending the oxide superconductor only once, it is 
broken. Even if the oxide superconductor can be bent successfully, it is 
instantly broken after the bent portion is slightly straightened. 
Therefore, the oxide superconductor cannot be processed into a coil or the 
like. Such property is still a disturbance to the practical use of the 
oxide superconductor. Therefore, researchers in the world have been 
devoted to improving and researching the oxide superconductor. 
Since it is very difficult to process a formed body of such oxide 
superconductor, coils or the like cannot be industrially mass produced. 
The oxide superconductor cannot be used in various applications. 
SUMMARY OF THE INVENTION 
Wherefore, an object of the invention is to provide a plastically 
deformable high temperature superconductive material which can be 
optionally processed into a predetermined configuration and can be 
industrially mass produced and to provide a method of manufacturing a 
formed body of the high temperature superconductive material. 
To attain this and other objects, the invention provides a plastically 
deformable high temperature superconductive material made of a powder raw 
material. The powder raw material is mainly composed of 10 to 50 mol % of 
at least one amide or nitride of an alkali metal selected from Li, Na or 
K; 10 to 60 mol % of cyanide containing at least one metal selected from 
aluminum, copper, silver or gold; 5 to 50 mol % of at least one pure metal 
selected from aluminum, copper, silver or gold; and 10 mol % or less of at 
least one alkaline earth metal selected from Be, Mg, Ca, Sr or Ba. The 
powder raw material is mixed and sintered under pressure to form the 
plastically deformable high temperature superconductive material. 
According to the invention, at the time of sintering, at least one amide 
compound of the alkali metal selected from Li, Na or K is heated and 
pyrolytically decomposed to form ammonia and the nitride of alkali metal. 
Ammonia is combined with the cyanide of aluminum, copper, silver or gold 
to form a stable ammine complex. On the other hand, the nitride of the 
alkali metal is combined with the pure metal of aluminum, copper, silver 
or gold to form a sintered material composed of metal-compound and metal. 
As a result, since the ammine complex and the sintered material composed of 
metal-compound and metal formed at the time of the sintering under 
pressure provide a good plastic workability, various predetermined 
configurations such as linear materials, plate materials, tubular 
materials or the like can be processed. Additionally, electrons can pass 
with a minimum electric resistance through the electrically stable ammine 
complex and the sintered material composed of metal-compound and metal. 
Here, the content of the amide is 10 to 50 mol %. If the content is less 
than 10 mol %, the quantity of ammonia generated as a decomposition 
product of the amide compound is excessively small. Therefore, a 
sufficient quantity of ammine complex cannot be prepared. On the other 
hand, if the content exceeds 50 mol %, the quantity of ammonia is 
excessively large. Then, blow holes are made in the formed body. 
Additionally, the content of cyanide is 10 to 60 mol %. The content less 
than 10 mol % is insufficient for preparing ammine complex. On the other 
hand, the content exceeding 60 mol % is more than necessary for preparing 
ammine complex. The cyanide is left as it is. Then, the electric 
resistance is increased. 
Further, the content of the pure metal is 5 to 50 mol %. If the content is 
less than 5 mol %, the quantity of the pure metal is excessively small for 
forming the sintered material composed of metal-compound and metal. Then, 
the electric resistance is increased. On the other hand, if the content 
exceeds 50 mol %, the physical properties of the metal are exhibited too 
much. Even if cooling is performed in any manner, the electric resistance 
is inhibited from decreasing. 
Additionally, the content of the alkaline earth metal is 10 mol % or less. 
If the content exceeds 10 mol %, an excess quantity of nitride thereof is 
generated. Then, the electric resistance increases. 
As aforementioned, the ammine complex and the sintered material composed of 
metal-compound and metal can be plastically deformed and optionally 
processed. Also, electrons can pass with a minimum electric resistance 
through the electrically stable ammine complex and the sintered material 
composed of metal-compound and metal. 
Also, the invention provides a method of manufacturing a formed body of a 
plastically deformable high temperature superconductive material formed of 
a powder raw material. The powder raw material is mainly composed of 10 to 
50 mol % of at least one amide or nitride of alkali metal selected from 
Li, Na or K; 10 to 60 mol % of cyanide containing at least one metal 
selected from aluminum, copper, silver or gold; 5 to 50 mol % of at least 
one pure metal selected from aluminum, copper, silver or gold; and 10 mol 
% or less of at least one alkaline earth metal selected from Be, Mg, Ca, 
Sr or Ba. The powder raw material is stirred in inert gas atmosphere, 
mashed and uniformly mixed. Subsequently, a metal capsule is filled with 
the powder raw material. By pressing and heating the metal capsule in a 
vacuum or in an inert gas atmosphere, the raw material is sintered. 
According to the invention, the powder raw material is stirred in the inert 
gas atmosphere, mashed and mixed to form the powder raw material with a 
uniform composition. In the process, the powder raw material is not 
oxidized. Also, after filling the capsule with the powder raw material, 
the capsule is heated and sintered under pressure in a furnace in the 
non-oxidizing vacuum or the inert gas atmosphere. At this time, the stable 
ammine complex and the sintered material composed of metal-compound and 
metal are formed. Since the ammine complex and the sintered material 
composed of metal-compound and metal are superior in plastic workability, 
they can be processed into various configurations. 
In the method of manufacturing the formed body of the plastically 
deformable high temperature superconductive material, the sintering is 
performed by heating the metal capsule in the inert gas atmosphere in a 
range of temperatures from 673 K to 1553 K for a period of time from 0.5 
to three hours. 
According to the invention, the sintering under pressure is performed in 
the range of temperatures from 673 K to 1553 K. Therefore, more stable 
ammine complex and sintered material composed of metal-compound and metal 
can be obtained. 
Here, the temperature range in which the superconductive material is 
sintered under pressure is from 673 K to 1553 K. If the temperature is 
less than 673 K, no ammine complex is generated. Additionally, at 1553 K a 
sufficiently stable ammine complex can be obtained. The temperature does 
not need to be higher than 1553 K. 
The period of time for heating is set from 0.5 to three hours. Within 0.5 
hour, a uniform heat cannot be obtained for the superconductive material. 
On the other hand, when heating is performed for three hours, a 
sufficiently uniform heat can be obtained. Then, more heat is unnecessary. 
In the method of manufacturing the formed body of the plastically 
deformable high temperature superconductive material, the formed body 
which was sintered under pressure is further rolled, forged, drawn or 
extruded to form a predetermined configuration. 
According to the invention, since the high temperature superconductive 
material having the ammine complex and the sintered material composed of 
metal-compound and metal is used, linear materials, plate materials, 
tubular materials or other formed bodies can be industrially mass produced 
optionally. 
In the method of manufacturing the formed body of the plastically 
deformable high temperature superconductive material, a stainless steel 
capsule or a copper capsule is used as the metal capsule. After the 
capsule is filled with the powder raw material and sintered, by rolling, 
forging, drawing or extruding the capsule, a coating layer of stainless 
steel or copper is formed on a surface of the high temperature 
superconductive material. 
According to the invention, since the material and the capsule are 
processed together with the material put in the capsule, a good yield is 
provided. Additionally, boundary surfaces of the coating layer and the 
high temperature superconductive formed body closely contact to each other 
through processing, and are prevented from peeling off during processing 
and operation. Further, since the coating layer of a soft material, e.g., 
stainless steel or copper is formed on the surface, the high temperature 
superconductive material can be easily wound like a coil configuration. 
The surface of the layer is thus durable. The coating layer serves as a 
protective layer for the metal which is easily oxidized in the atmosphere, 
and as a shielding material for the metal which easily reacts with 
moisture in the atmosphere.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
An embodiment will be described with reference to the accompanying 
drawings. In the embodiment there is provided a high temperature 
superconductive material which is plastically deformable, can be freely 
processed in a predetermined configuration and which can be industrially 
mass-produced. There is also provided a method of manufacturing a formed 
body of the high temperature superconductive material. 
In the method, as shown in FIG. 1, at step S1 19.8 mol % of pure copper 
powder mashed to 200 mesh or less and 1 mol % of Ca powder finely ground 
in an argon gas atmosphere are mixed and stirred in a mortar in the argon 
gas atmosphere. Subsequently at step S2, 29.7 mol % of Li amide powder and 
49.5 mol % of copper cyanide powder are also placed in the mortar and 
stirred for 15 hours by using a stirring mixer in the argon gas 
atmosphere. These powder raw materials are uniformly intermixed. 
Subsequently, at step S3 the mixed powder is pressed in the argon gas 
atmosphere under the pressure of 2000 MPa to form a block which has a 
configuration matched with an inner configuration of a capsule. At step S4 
the capsule of stainless steel is filled with the block. The capsule is 
deaerated and sealed. At step S5 the capsule with the block held therein 
is transferred into a hot press chamber, in which the capsule is pressed 
under the pressure of 50 to 250 MPa, preferably 150 MPa and sintered in 
the argon gas atmosphere at a temperature of 673 K to 1553 K, preferably 
1423 K for 0.5 to three hours, preferably three hours. Finally, a sintered 
body of plastically deformable high temperature superconductor is obtained 
at step S6. 
In the method, at the time of sintering, ammine complex and sintered 
material composed of metal-compound and metal are formed. The sintered 
body is plastically deformable, and can be freely processed into a 
predetermined configuration. Also, electrons can pass with a minimum 
electric resistance through the electrically stable ammine complex and the 
sintered material composed of metal-compound and metal. 
Additionally, the ammine complex has a chemical composition of, for 
example, Cu.sub.4 (NH.sub.3).sub.2 (CN).sub.4, and makes up 47.6 mol % of 
the entire sintered body. 
Measurement results of the electric resistance of the sintered body are 
shown in FIG. 2. In the measurement, a 0.144 cm wide, 0.099 cm thick and 
2.33 cm long test piece was used. The test piece was gradually cooled from 
a room temperature. By applying an electric current of 10 mA to the test 
piece, the electric resistance was sequentially measured. 
As a result, the electric resistance of 0 .OMEGA. cm was indicated at the 
temperature of 40 K, and further a value close to 0 .OMEGA. cm was 
indicated at the temperature of 80 K. Additionally, by slightly reducing 
the blending ratio of the cyanide, 80 K or higher critical temperature can 
be obtained. 
In the same manner as the aforementioned sintered body, a 0.02 cm wide, 
0.025 cm thick and 2.0 cm long test piece was prepared. When an electric 
current of 5 A was supplied, the test piece was normal without generating 
heat. At this time, the current density was 10000 A/cm.sup.2. 
Further, a coating layer or capsule layer was scraped from the sintered 
body. Then, the sintered body was forged with a press or a hammer, and 
bent or straightened. However, no crack was made on surfaces and inner 
faces of the formed body of the high temperature superconductive material. 
The sound formed body was obtained. For the appearance of the formed body, 
it had a copper color and a specific weight of 8.2. Consequently, linear 
materials, plate materials, tubular materials or other formed bodies can 
be industrially mass-produced optionally. 
Additionally, the sintered body covered with the stainless steel capsule 
was forged with a press or a hammer, then bent or straightened. A sound 
high temperature superconductive formed body with no crack could be 
obtained. In this case, the processing is performed with the sintered body 
put in the capsule. Therefore, a good yield can be provided. Additionally, 
the boundary surfaces of the coating layer and the superconductive 
material closely contact to each other through the processing. Therefore, 
these are not peeled off from each other during processing and operation. 
Further, the coating layer of a soft stainless steel is formed on the 
surface of the sintered body. Therefore, the sintered body can be wound 
like a coil configuration. The surface is durable. The coating layer also 
protects the metal liable to be oxidized in the high temperature 
superconductive material from the atmosphere, and further shields the 
metal liable to react with moisture from the atmosphere. 
Qualitative values as X-ray analysis data of the sintered body prepared in 
the aforementioned processes will be described with reference to FIG. 3. 
FIG. 3A shows X-ray intensities; FIG. 3B shows X-ray peaks; FIG. 3C shows 
the state in which copper is detected; FIG. 3D shows the state in which 
CuCN is detected; FIG. 3E shows the state in which Li.sub.3 N is detected; 
and FIG. 3F shows the state in which Ca.sub.3 N.sub.2 is detected. Here, 
large waveforms which appear among small waveforms indicative of X-ray 
intensities completely coincide with waveforms indicative of peak data and 
waveforms of copper. It is indicated that copper is a main component. 
Although it is not shown, in FIG. 3A, by large peaks, it can be seen from 
the positions of small peaks that other components such as CuCN, Li.sub.3 
N and Ca.sub.3 N.sub.2 are included as well. 
According to the embodiments, the high temperature superconductor sintered 
body can be freely processed through forging, rolling, drawing, extruding 
and the like. Additionally, since the sintered body can be easily formed 
in a linear, plate, tubular, annular or another predetermined 
configuration, it can be practically used in various broad fields. 
An innovation is brought especially in a linear motor car, a high-speed 
computer, a magnet, an electricity generator, an electric motor, power 
supply, power storage or the like. Then, great innovation and improvement 
are established in an electric power or energy field or an electric or 
electronic field. 
While the preferred embodiment of the invention has been described, it is 
to be understood that the invention is not limited thereto, and may be 
otherwise embodied within the scope of the following claims. 
For example, in the embodiment, pure copper powder is used as the pure 
metal. Even if pure aluminum powder, pure silver powder or pure gold 
powder is used, the same effect can be obtained as the pure copper powder. 
Also in the embodiment, Ca powder is used as the alkaline earth metal. 
Even if Be powder, Mg powder, Sr powder or Ba powder is used, the same 
effect can be obtained as the Ca powder. Further in the embodiment, Li 
amide powder is used as the amide. Even if Na amide powder or K amide 
powder is used, the same effect can be obtained as the Li amide powder. 
Also in the embodiment, copper cyanide powder is used as the cyanide. Even 
if silver cyanide powder or gold cyanide powder is used instead, the same 
effect can be obtained as the copper cyanide powder. 
Additionally, in the embodiment, after the pure copper powder and the Ca 
powder are mixed and stirred in the inert gas, the Li amide powder and the 
copper cyanide powder are mixed in the inert gas. Alternatively, these 
powder materials can be mixed and stirred altogether in the inert gas. 
Further in the embodiment, the stainless steel capsule is used as the metal 
capsule. Even the use of a copper capsule has the same effect as the 
stainless steel capsule. 
Also in the embodiment, the high temperature superconductive material is 
sintered with a hot press. Alternatively, the burning can be performed 
with hot isostatic press (HIP).