JPS63288954A - Production of superconductor - Google Patents

Abstract

PURPOSE:To produce a superconductor exhibiting superconductivity at above the b.p. of liquid N2 by calcining a molded body obtd. by compression molding a powder mixture consisting of Y oxide Ba oxide, and Cu oxide in oxidizing atmosphere. CONSTITUTION:A binder is mixed with a powder mixture consisting of Y oxide (e.g. Y2O3), Ba oxide (e.g. BaO), and Cu oxide (e.g. CuO), and a molded body is prepd. by compression molding the obtained mixture. Then, the molded body is calcined at 950-1,200 deg.C in oxidizing atmosphere, and a Y-Ba-Ca-O superconductor consisting of 10<=Y<=60atom.%, 20<=Ba<=50atom.%, and 30<=Cu<=65 atom.% is obtained.

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 at temperatures above liquid nitrogen temperature.

B1 Summary of the Invention The present invention provides yttrium (Y) and barium (Ba) formed using powders of yttrium oxide, barium oxide, and copper oxide as starting materials.

A method for manufacturing a superconductor which is a sintered body consisting of copper (Cu) and oxygen (O) and exhibits superconductivity at a liquid nitrogen temperature (absolute temperature of 77 degrees Celsius) or higher.

C1 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. For practical use, the critical temperature ('rc)
The higher the temperature, 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 are used after being cooled to liquid helium temperature (Tc approximately 4, -269°C), which requires cooling with a coolant made from liquefied helium gas. 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 on superconducting materials has been progressing in the financial world, and materials that break with conventional concepts are appearing.

The highest 'I' c of the superconducting materials known so far was 22.3K for niobium 3 germanium (Nb3Ge), but some of the La (lanthanum) was replaced with Ba (barium 2.). With lanthanum, strontium-12, and copper oxide (I, aSr) tcuo4, superconductivity began in 1937, exceeding the previous limits, and it was announced that electrical resistance became zero in 1933, and then this year Initially, it was announced that 54K was achieved using the same La-8r-CuO4 system, and that 85K was achieved using the same material. Furthermore, although the name of the substance is only disclosed as "oxide", lanthanum and
It was announced that T, c77K had been achieved using a new substance believed to be based on strontium oxides. Furthermore, in recent years, barium, ibuterbium, and copper oxides that exceed 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 advantageous in all respects compared to the use of liquid Heliu-11 and is extremely easy to put into practical use, so 'rc is 7.
Although the development of superconducting materials as described above is desired, the current situation is that, as mentioned above, the development has only just begun.

In view of these points, it is an object of the present invention to provide a method for manufacturing a superconductor that becomes superconducting in 77 or later.

Means and functions to solve the E1 problem If superconductors can be used with liquid nitrogen cooling, electricity can be generated.

Focusing on the fact that it can be used in a wide range of fields such as transportation and energy conversion, we conducted repeated experiments with various material formulations, firing temperatures, etc., and found that it could be used in a wide range of fields such as transportation and energy conversion.
A sintered body consisting of the components of Cu) and oxygen (O), where Y in one component of the sintered body, Y B a Cu, is 10≦
It has been found that a superconductor with zero resistance can be obtained by cooling with liquid nitrogen as long as Y≦60 atomic %, B, 20≦Da≦50 atomic %, and Cu 30≦Cu≦65 atomic %.

That is, a mixed powder obtained by mixing yttrium oxide powder, barium oxide powder, and copper oxide powder is pressurized to form this molded body in an oxidizing atmosphere and 1200℃
By sintering in a range of We discovered that if a superconductor is formed, a superconductor with zero resistance can be easily obtained by cooling with liquid nitrogen.

In addition, in Y-Ba-Cu, if Y/J<IO atomic %, Ba exceeding 60 atomic % is less than 20 atomic %, Cu exceeding 50 atomic % is less than 30 atomic, or exceeds 65 atomic %, superconductivity can be achieved with liquid nitrogen. It was not possible to obtain a sintered body in which .

F. Examples The present invention will be explained below based on examples. First, starting materials are yttrium oxide (Y=03) powder, barium oxide (Bao) powder, and copper oxide (Cub) powder each having a particle size of 10 μm or less.

respectively 20ao1%, 30mo1%, 50mo1%
Weigh it so that

Next, these powders are mixed using a ball mill or the like, and ethyl alcohol and cobblestone are added thereto and thoroughly mixed for several hours, and the resulting slurry is dried at a temperature of about 100''C.

In addition, when water is present in barium oxide, BaO + HtO
→ Alcohol is used because a large amount of heat is generated by the reaction of Ba(OH)t.

Next, polyvinyl alcohol is added as a binder in the form of a polyvinyl alcohol solution so that the amount is 1% by weight based on the raw material powder. After further adding alcohol and thoroughly kneading, the mixture is dried and sieved to obtain granulated powder having a size of 150 mesh or less.

Next, after filling this granulated powder into a mold, 700 kg/a
Compression molded with a pressure of about x”, outer diameter 40xm, thickness approx.
Make a molded body of xx.

Next, this molded body is placed in a firing oven and heated in an oxidizing atmosphere.
A sintered body (ceramics) is obtained by heating at a temperature of about 1050° C. for several hours.

The sintered body obtained by the above manufacturing method was cut into a shape of 4If in the middle, 4xyt in thickness, and 1011z in length. Electrodes were provided as shown in Figure 1, and the sintered body was cut out by the four-terminal method. Resistance was measured.

That is, FIG. 1 is an explanatory diagram for measuring the resistance value, in which terminals a for passing current through both ends of the sintered body S in the longitudinal direction,
A' is provided, and inside it is a voltage terminal for measuring the resistance value. 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.

Figure 2 shows the measurement results, with an absolute temperature of approximately 93
It was confirmed that the superconducting phenomenon began at about 89K, and that the electrical resistance became zero.

Similar experiments were conducted with other composition ratios, so the description will include the above-mentioned examples.

However, Example 1 in the table shows the above.

Note that Y, 0. was less than 501o1%, BaO in excess of 30mo1% was less than 20mo1%, CuO in excess of 50mo1% was less than 30111o1%, and 65Ilo was more than 1%, it was not possible to obtain a sintered body that produced superconductivity.

In short, yttrium oxide (Y, 03) in terms of starting material
is 5 to 30 moI%, barium oxide (Bad) is 20
~50 mo1%, copper oxide (Cub) 30-65 mo
It was found that if the concentration was 1%, the resistance would be zero with liquid nitrogen.

That is, in Y-Ba-Cu, which is a component constituting the sintered body, Y is 10 to 60 at%, and Ba is 20 to 50 at%.
It has been found that a superconductor can be obtained if the Cu content is 30 to 65 atomic %.

Furthermore, y, o3=20mo of the composition conditions of Example I mentioned above.
1%, Ba0=30mo1%, CuO=50mo1%
As a result of investigating the sintering temperature by changing the sintering temperature, 950
The desired superconductor could be obtained by sintering at a temperature of 1200°C to 1200°C.

However, at temperatures below 950°C and above 1200°C, it was not possible to obtain a sintered body that produced the desired superconducting phenomenon.

G1 Effects of the Invention As described above, the superconductor according to the present invention has a temperature of liquid nitrogen (
It becomes completely superconducting at 77K).

Furthermore, powders of yttrium oxide, barium oxide, and copper oxide are used as starting materials for the sintered body of Y-Ba-Cu-0, and in addition, powders of yttrium oxide, barium oxide, and copper oxide are used as starting materials, and in addition, powders of 950~ Because it is sintered at a temperature of 1200℃,
A dense superconductor with stable characteristics can be easily obtained.

The currently discovered superconductor requires cooling with a coolant made from liquefied helium gas, and the temperature of liquid helium is 4.2, and it is a rare and expensive material, and the cost of liquefying it is high. This 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 it has extremely excellent effects, such as being able to be used in fields such as electrical resistance, precision measurement elements, and other energy conversion related to electricity, transportation, etc.

[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). a, a'... Current supply terminal, b, b'...
・Voltage measurement terminal, S...Sintered body. −Masu■5 ξ

Claims (1)

[Claims] A step of mixing yttrium oxide powder, barium oxide powder, and copper oxide powder to obtain a mixed powder; and a step of pressurizing the mixed powder to obtain a compact. , a step of firing the molded body in an oxidizing atmosphere at a temperature in the range of 950°C to 1200°C to form a sintered body, and the sintered body contains yttrium (Y), barium (Ba). , consisting of copper (Cu) and oxygen (O) components, and Y-Ba
-The component ratio in Cu is yttrium (Y) to 10≦Y≦60 atomic% barium (
Ba) is 20≦Ba≦50 atomic% Copper (Cu) is 30≦C
A method for producing a superconductor, characterized in that u≦65 atomic %.