JPH0214868A - Production of superconductor - Google Patents

Abstract

PURPOSE:To easily obtain a stable superconductor containing three specific kinds of components and having high critical temperature without causing cracking, etc., by mixing and calcining two kinds of the components, mixing the other component to the mixture and forming and calcining the composition. CONSTITUTION:A superconductor of formula A1-A2-A3-O (A1 is Y; A2 is Sr or Ca; A3 is Cu, Zn, Ni, Co, Fe, Pd, Ag or Cd) (10<=A1<=60atom.%; 20<=A2<=50 atom.%; 30<=A3<=65atom.%) is produced by selecting two components from A1, A2 and A3 and mixing the powder of the selected components. The mixed powder is calcined, pulverized and then mixed with the powder of the remaining component. The obtained mixture is compression molded and subjected to main calcination in an oxidizing atmosphere at 950-1200 deg.C to obtain a superconductor consisting of a sintered product having a K2NiF4 structure containing rhombic crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a so-called superconductor whose electrical resistance becomes zero at a certain temperature, and particularly to a superconductor which exhibits superconductivity above the temperature of liquid nitrogen.

B0 Summary of the Invention The present invention involves mixing powders, calcining the mixture, pulverizing the processed powder, and mixing other powders to obtain a mixed powder. It is a sintered body obtained by main firing in an oxidizing atmosphere, and the liquid nitrogen temperature (absolute temperature 77 degrees)
The above is a method for manufacturing a superconductor exhibiting superconductivity.

C0 Conventional Technology Since the discovery of superconductivity by Kamerling Onnes in 1911, various research and development efforts have been underway to put it into practical use. Criticality 171 for practical use? L degree (
The higher the temperature ('re), the lower the cooling cost, so there is intense competition to develop superconducting materials with the potential for superconductivity at higher temperatures.

Most of the superconducting materials that have been revealed so far have been cooled to liquid helium temperatures (Tc approximately 4, -269°C); There must be. Helium is a rare and expensive material, and the cost of cooling it down to its critical temperature is extremely high, making it the main reason for delaying the spread of superconducting materials.

Very recently, research and development into superconducting materials has progressed worldwide, and materials that break with conventional concepts are appearing.

The highest Tc of superconducting materials known so far is niobium 3
The temperature was only 22.3K for germanium (N bs Ge), but lanthanum/strontium/copper oxide (in which part of La (lanthanum) is replaced with Ba (barium))
With LaS r)y Cuo 4, it was announced that the superconducting phenomenon began at 37, exceeding the previous limit, and that the electrical resistance became zero at 33, followed by the same (La-5r-Cuba) at the beginning of this year. It was announced that 54K was achieved with a system based on the same material, and 85K with the same material.Furthermore, the name of the material was only disclosed as "monooxide," but a new material believed to be based on lanthanum, strontium, and the same oxide was announced. by T
It was announced that he had achieved c77K. Furthermore, in recent years,
Barium, ytterbium, and copper oxides with temperatures exceeding 100K.

It has been announced that a superconducting material made of yttrium-based copper oxide has been discovered.

D0 Problems to be solved by the invention As mentioned above, the temperature of liquid helium is 4.2 at normal pressure. The cooling cost was extremely high, which was an obstacle to practical application. Also, if it is 77 or higher, you can use liquid nitrogen,
It is desired to develop a superconducting material with a Tc of 77 or higher because it is advantageous in all respects compared to the use of liquid helium and is extremely easy to put into practical use. The current situation is that it has just started.

In view of these points, the present invention seeks to provide a method for manufacturing a superconductor that becomes superconducting in 77 or more steps.

E9 Means and Functions to Solve Problems If superconductors can be used with liquid nitrogen cooling, power.

Focusing on the fact that it can be used in a wide range of fields such as transportation and energy conversion, as a result of repeated experiments such as blending and firing various materials, Y
It has been found that a sintered body having a NiF structure can be obtained when the elemental composition of -3r-Cu-0 includes orthorhombic crystals that cause a superconducting phenomenon.

Moreover, it is not limited to the elements strontium (Sr) and copper (Cu), but any element with a similar ionic radius,
It was also found that a sintered body capable of producing a superconducting phenomenon could be obtained.

Zunawachi, ■Yttrium (Y), which is the first component (A1).

(2) A second component (A2) consisting of at least one element among Sr and Ca, which are elements with similar ionic radii.

■ Elements copper (Cu) and zinc (Z) with similar ionic radii
n), nickel (N i ), cobalt (Co), iron (
Fe).

Palladium (Pd), silver (A g ), cadmium (C
d) The third component (A2
).

These A1. It has been found that a sintered body having a 2NiF4 structure including orthorhombic crystals can be obtained by causing a superconducting phenomenon with the main component (An) consisting of elements belonging to At and As and oxygen (0).

However, A forms the main component (An) of the sintered body.

If the composition of A2A2 is within the range of A, 10≦Δ1≦60 atomic%, At, 20≦At≦50 atomic%, and A3, 30≦A3≦65 atomic%, the liquid has a KtNtF* structure including orthorhombic crystals. We have discovered that a superconductor with zero resistance can be obtained by cooling with nitrogen.

That is, three components (A + , A t , A 2)
A mixed powder is prepared by mixing multiple types of powder mainly composed of elements belonging to two of the components (for example, A I, A!), and this mixed powder is pre-fired at a temperature lower than the temperature of the main firing, The obtained calcined product is pulverized to make a processed powder, and this processed powder is mixed with a powder mainly composed of elements belonging to the remaining one component (for example, A2) to make a mixed powder. By pressurizing a molded body and sintering this molded body in an oxidizing atmosphere at a temperature of 950°C to 1200°C, the main component (An) consisting of AI A2 As and oxygen (0) are separated. and contains orthorhombic crystals
We have discovered that a superconductor with zero resistance can be easily obtained by cooling with liquid nitrogen having an eN i F 4 structure.

In addition, in AI At A3 in the sintered body,
A1 is less than 10 atom% iiJ, A2 is more than 60 atom%,
Less than 20 atomic % and more than 50 atomic % When A3 is less than 30 atomic % and more than 65 atomic %, it has been impossible to obtain a sintered body in which superconductivity occurs in liquid nitrogen.

In addition, powders mainly composed of elements belonging to each component (A5. It is something.

F. Example Hereinafter, the present invention will be explained based on examples.

First, as a starting material, yttrium oxide (Y,
The powder of strontium carbonate (SrCO5) having 1 mol% of the powder of 03) as the second component (A2) was
mo1%, copper oxide (Cub) present in the third component (A3)
) are each weighed to give a ratio of 56 mo1%.

Then, using these powders, mix - calcining -> pulverize -
The mixing and main firing operations were performed, and the powders were mixed and combined as follows.

Next, since the manufacturing method was explained in detail in each Example and B, the following description will be made using Example 1 as a representative.

First, powders of Y and 03 and powders of 5rCOs are thoroughly mixed in a ball mill, etc., and ethyl alcohol and cobblestones are added and mixed thoroughly for several hours, and the resulting slurry is heated to approximately 100°C.
Dry at a temperature of

Next, the mixed powder obtained by drying is placed in an alumina container and heat-treated in an oxidizing atmosphere at a temperature of approximately 900°C, which is lower than the temperature of the main firing in the subsequent process, for approximately 2 hours (so-called pre-calcination).
do.

Next, the baked powder obtained becomes hard as the powders react with each other, so transfer it to the milk drum set in the Laikaiki,
Add alcohol and grind in a wet process to obtain a fine processed powder.

Then, CuO powder is added to the processed powder obtained and thoroughly mixed in a ball mill, water and cobblestones are added, and the mixture is thoroughly mixed for several hours, and the resulting slurry is dried at a temperature of about 100°C.

Next, to the mixed powder obtained by drying, polyvinyl alcohol is added as a binder in the form of an aqueous polyvinyl alcohol solution so that the amount is 1% by weight based on the mixed powder. After further adding water or alcohol and thoroughly kneading, dry and sieve to obtain granulated powder of 150 mesh or less.

Next, after filling this granulated powder into a mold, 700 kg
Compression molded at a pressure of about / cm2 to an outer diameter of 40 m.
m, a molded body with a thickness of about 6 mm is made.

Next, this molded body is placed in a sintering machine and heated in an oxidizing atmosphere at a temperature of about 1050° C. (a temperature higher than the pre-firing temperature of the multilayer) for several hours to obtain a sintered body (ceramics).

The sintered body obtained by the above manufacturing method is
The sintered body was cut into a shape with a thickness of 4 mm, a thickness of 4 mm, and a length of 40 mm, and electrodes were provided as shown in FIG. 1 to measure the resistance of the sintered body by a four-terminal method.

Therefore, FIG. 1 is an explanatory diagram for measuring the resistance value, and shows terminals a for passing a current to both ends of the sintered body S in the direction of the force applied by the hand;
A' is provided, and a voltage terminal B' is provided inside it for measuring the resistance value.Place this in a liquid nitrogen cryostat, and run a stabilized current of 1 ampere through terminals a and a' to connect the terminals. Measure the voltage between terminals A and B' with a voltmeter (V), and measure the resistance value by the voltage drop between terminals A and B'.

Note that A indicates an ammeter.

FIG. 2 shows the measurement results, and it was confirmed that the superconducting phenomenon started at an absolute temperature of 91 K, and that the electrical resistance became zero at about 89 K.

In addition, an example carried out by the same means as Example 1-
In the sintered bodies of Example 2 and Example 3, the superconducting phenomenon started at an absolute temperature of about 91, similar to the case of Example 1, and
It was confirmed that the electrical resistance became zero at 9K.

In addition, Y t O3 is 5no1% or less ii'4,30mo
Exceeds 1%, 5rCOs is less than 20mo1% id4,50m
Exceeding o1%, CuO less than 30mo1%, 65mo1%
In excess, it was not possible to obtain a sintered body that produced superconductivity.

In short, the first component (A1) is 5 to 30 mo in terms of starting material.
1%, the second component (A2) is 20 to 50 mo1%, and the third component (A2) is 30 to 65 mo1%, it has been found that a sintered body with zero resistance can be obtained in liquid nitrogen.

That is, the component An (AIAt) constituting the sintered body
A3) In O, A1 At A3,
A, is lO~60 at%, nuclear reactor 20~50 at%,
If A3 is 30 to 65 at%, Kf containing orthorhombic crystals
fiNiI? It was found that a superconductor having 4 structures can be obtained.

Furthermore, the composition conditions and manufacturing conditions of Example-1 were investigated by changing the temperature of preliminary sintering of Y2O3 powder and 5rCO0 powder to 900 °C and the temperature of main sintering with addition of CuO powder. As a result, the desired superconductor could be reliably obtained by main sintering at a temperature of 950°C-t200°C.

However, if the temperature is lower than 950°C or higher than 1200°C, a sintered body that produces the desired superconducting phenomenon cannot be stably obtained.

In addition, as a result of setting the main firing temperature to about 1050°C and changing the temperature of the preliminary firing of Y2O3 powder and SrCO3 powder, it was found that heating at a temperature of about 800°C or higher and below the main firing temperature (about CuO
It has been found that during main firing after adding powder, the reaction is gradual and a sintered body of stable quality without cracking or distortion can be obtained.

From the above, first, under the conditions below the main firing temperature,
Mix multiple types of powders mainly composed of elements belonging to one component group, pre-calcined (heat treated), and add powders mainly composed of elements belonging to the remaining component groups to the processed powder obtained by pulverizing the mixture. It has been found that if the obtained mixed powder is used for main firing, a sintered body of stable quality, that is, a super 7 [conductor] can be obtained.

Effects of the G9 Invention The superconductor according to the present invention as described above has a temperature of liquid nitrogen (
It becomes completely superconducting at 77K).

Moreover, the starting material in the sintered body of An(AI A2 A3) O is the first component (A1) mainly composed of yttrium (Y), which has an ionic radius approximately the same as that of the element represented by strontium (Sr). Using powder of a material consisting of a second component (A2) mainly consisting of an element that exists in the present invention, and a third component (A3) mainly consisting of an element whose ionic radius is approximately the same as that of an element represented by copper (Cu). During the preliminary firing, a mixed powder consisting of multiple types of powder corresponding to two of the three components (groups) is mixed at a temperature lower than the temperature of the main firing (950 to 1200°C). The powder is obtained by heat treatment (preliminary firing), and then the powder is mixed with powder corresponding to the remaining components (group) and then the final firing is performed, so there is no cracking or distortion, and the properties are stable. A fired body, that is, a superconductor, can be easily obtained.

The currently discovered superconductor requires cooling of helium gas with a liquefied coolant. The high cost of liquefaction has been a barrier to the practical application of superconducting materials.

However, liquid nitrogen can be used anywhere and cheaply by hand.
The conventional barriers to practical application have been completely removed, and the present invention exhibits extremely excellent effects, such as being able to be used in fields such as electrical resistance 5 and precision measurement elements, particularly related to electric power, transportation, etc., and other fields such as energy conversion.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram for explaining the method of measuring the resistance value of the sintered body of the present invention, and Figure 2 is the absolute temperature (K) of the sintered body of the present invention.
) is a characteristic curve diagram of the resistance value (10-3 Ωcm) versus 4-Ωcm. a, a'...terminals for current supply, b, b'...voltage measurement terminals, S...sintered body.

Claims (1)

[Claims] The first component (A_1) has the element Y, and the second component (A_1) has the element Y.
A_2) contains at least one element among Sr and Ca, and the third component (A_3) contains Cu, Zn, Ni, Co. Fe
, Pd, Ag, and Cd, and select any two of the three components (A_1, A_2, A_3) and select the elements belonging to these components. A step of mixing multiple types of main powder to obtain a mixed powder, pre-calcining the mixed powder at a temperature lower than the main firing temperature, and pulverizing the pre-calcined product to obtain a processed powder; A step of mixing the powder and a powder mainly composed of elements belonging to the remaining components to obtain a mixed powder, and pressurizing the mixed powder to obtain a molded body, and heating the molded body in an oxidizing atmosphere at 950°C ~1200
K_2NiF containing orthorhombic crystals by main firing at a temperature in the range of ℃
a step of forming a sintered body having a _4 structure, the sintered body is composed of components A_1, A_2, A_3 and oxygen (0), and the configuration of A_1-A_2-A_3 is such that A_1 is 10 A method for producing a superconductor, characterized in that ≦A_1≦60 atomic %, A_2 satisfies 20≦A_2≦50 atomic %, and A_3 satisfies 30≦A_3≦65 atomic %.