JPS63291849A - Production of superconductor - Google Patents

Abstract

PURPOSE:To obtain a superconductor capable of exhibiting superconductivity, especially at liquid N2 temperature or above, by firing a compact of a blended powder of Y oxide powder, Ba hydroxide power and Cu oxide powder in an oxidizing atmosphere. CONSTITUTION:Powder of an Y oxide (Y2O3) is thoroughly mixed with powder of Ba hydroxide [Ba(OH)2] and powder of Cu oxide (CuO) in a ball mill, etc. The resultant blended powder is then filled in a metallic mold and compacted under about 700kg/cm<2> pressure to provide a compact, which is then placed in a firing device and fired at about 1,050 deg.C temperature in an oxidizing atmosphere for several hour to afford the aimed superconductor consisting of a sintered compact. The above-mentioned sintered compact is required to consist of Y, Ba, Cu and O and have composition ratios of 10<=Y<=60atom.%, 20<=Ba<=50atom.% and 30<=Cu<=65atom.% in Y-Ba-Cu. The superconductor of this invention completely attains a superconducting state at liquid N2 temperature (77K).

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.

B8 Summary of the Invention The present invention was formed using yttrium oxide, barium hydroxide, and copper oxide powders as starting materials. Yttrium (Y), barium (Ba), copper (Cu)
The present invention provides a method for producing a superconductor which is a sintered body consisting of the following components:

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 application, the higher the critical temperature (Tc), the lower the cooling cost, so there is intense competition to develop superconducting materials with the potential for superconducting 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 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 (NbsGe), but lanthanum/strontium/copper oxide (L a
With S r) *Cuo 4, the superconducting phenomenon began at 37, exceeding the previous limit, and it was announced that the electrical resistance had become zero at 33, followed by the same <La at the beginning of this year.
-9r-Cubs type 54K, and the same material type 85K
It was announced that it had been achieved. Furthermore, although the name of the substance is only disclosed as "oxide," Tc77K is produced by a new substance that is thought to be based on lanthanum, strontium, and the same oxide.
It was announced that the goal had been achieved. Furthermore, in recent years, 100K
barium, ibuterbium, and copper oxide.

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

D9 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.

E7 Means and Actions 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, we have repeatedly experimented with various material formulations, firing temperatures, etc.
) and oxygen (O), and in Y-Ba-Cu, which is a component of the sintered body, Y is 10≦Y≦60 atomic%, Ba is 20≦Ba≦50 atomic%, and Cu is 30≦ It has been found that a superconductor with zero resistance can be obtained by cooling with liquid nitrogen as long as Cu≦65 atomic %.

That is, a mixed powder obtained by mixing yttrium oxide powder, barium hydroxide powder, and copper oxide powder is formed by pressing, and this molded body is heated in an oxidizing atmosphere at 950°C. By sintering in the range of ~1200℃,
Yttrium (Y), barium (Ba), copper (Cu),
It has been shown that if a sintered body consisting of Y-Ba-CU and oxygen (O) is formed and the Y-Ba-CU component is within the above-mentioned range, a superconductor with zero resistance can be easily obtained by cooling with liquid nitrogen. I found it.

In addition, in Y-Ba-Cu, when Y is less than IO atomic %, Ba is less than 20 atomic % in excess of 60 atomic %, Cu is less than 30 atoms in excess of 50 atomic %, and Cu is in excess of 65 atomic %, superconductivity occurs in liquid nitrogen. A sintered body could not be obtained.

F. Examples The present invention will be explained below based on examples. First, as starting materials, yttrium oxide (Ytos) powder with a particle size of 10 μm or less, barium hydroxide (Ba
(OH) z) powder, copper oxide (CuO) powder,
20so1% and 30mo1% respectively.

Weigh it so that it is 50+++o1%.

Next, these powders are thoroughly 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, since barium hydroxide has solubility in water, it is necessary to perform mixing and granulation using a water-free solvent (for example, ethyl alcohol).

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 to 9/a
Compression molded with a pressure of about x”, outer diameter 40wx, 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 with a thickness of 4 x z and a length of 40 m.
The resistance of the sintered body was measured by a four-probe method using electrodes as shown in the figure.

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, and a voltage terminal B' is provided.This is placed in a liquid nitrogen cryostat, and a stabilized current of 1 ampere is passed through terminals a and a' to connect the terminals. Measure the voltage between terminals S and B' with a voltmeter (v), and measure the resistance value by the voltage drop between terminals S 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. is less than 5 mo1%, Ba (OH) exceeding 30 mo1%, is less than 20 mo1%, CuO is less than 30!101%, exceeding 65 mo1%,
It was not possible to obtain a sintered body that produced superconductivity.

In short, yttrium oxide (Y, O8) in terms of starting material
is 5 to 30 mo1%, barium hydroxide (Ba(oH)
t) is 20 to 50 mo1%, copper oxide (CuO) is 30
It was found that if it was ~65 mo1%, 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, YtO,=20mo under the composition conditions of Example 1 described above.
1%, Ha(OH)*=30@o1%, CuO=50m
As a result of investigating 1% o by changing the sintering temperature,
The desired superconductor could be obtained by sintering at a temperature of 950°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.

Effects of the G9 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 hydroxide, 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 hydroxide, and copper oxide are used as starting materials. Since it is sintered at a temperature of ~1200°C, 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 is available everywhere and cheaply.
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 drawings]

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.
) shows a characteristic curve diagram of the resistance value (10-"Ωam). a, a'... terminal for current supply, b, b'...
Voltage measurement terminal, S... sintered body.

Claims (1)

[Claims] A step of mixing yttrium oxide powder, barium hydroxide powder, and copper oxide powder to obtain a mixed powder, and a step of pressurizing the mixed powder to obtain a compact. and 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, the sintered body containing yttrium (Y), barium (Ba ), copper (Cu) and oxygen (O), 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 %.