JPH0465342A - Superconductor and its production - Google Patents

Abstract

PURPOSE:To improve the critical temp. and current density of the semiconductor by incorporating an oxide consisting essentially of Bi, Sr, Ca and Cu, Ag and Pd into the total composition. CONSTITUTION:A starting material obtained by mixing Bi, Sr, Ca and Cu in the atomic ratio of 2:2:1:2 or 2:2:2:3 or the material, in which 10-30mol% of the Bi is replaced by Pb, is mixed with methanol and crushed in a ball mill, and the product is dried at 100 deg.C for 24hr. The material is placed on an alumina burning plate, calcined at about 800 deg.C for about 24 hr in the atmosphere using an electric furnace, then wet-crushed and dried. The powder for synthesis is placed on an alumina burning plate, heated at about 840 deg.C for about 50hr in a low-oxygen-pressure atmosphere at O:N=1:10 to obtain a bismuth-based superconductor. The material is wet-crushed and mixed with 10-35wt.% Ag (e.g. silver powder having 0.8mum average grain diameter) and 0.1-2wt.% Pd (e.g. Pd powder having 1.0mum average grain diameter), the mixture is pelletized at about 147MPa and sintered at about 840 deg.C for 10hr in the atmosphere to obtain the superconductor.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a superconductor and a method for manufacturing the same.

(Prior art) As a conventional superconductor, on January 20, 1988, 88! ! A B1-8r-Ca-CuO-based oxide superconductor whose main components are bismuth, strontium, Cal/Rum, and copper discovered by joint researchers is generally known;
The critical temperature at which the electrical resistance of the a-Cu -0-based oxide superconductor becomes zero (hereinafter referred to as T'3erO) is 10K, and Tl-Ba-Ca whose main components are thallium, barium, calcium, and copper It is known that it is the second highest after the -CuO system.

On the other hand, the B1-8r-Ca-Cu-0-based oxide superconductor is characterized by being less toxic than the Tl-Ba-Ca-Cu-0-based oxide superconductor; There are also 2223 phases.

2212 phase when Tg0 is 80 or 22 when T0 is 20
There is a drawback that 01 phase is easily generated.

Later, the Japanese Journal of Applied Physics
of Applied Physics) Vol.
No. 27.6 (June 1988), L1041-L10
B1-Pb-8 with lead added as shown on page 43
It has been revealed that a large amount of 2223 phase can be obtained in the r-Ca-Cu-0-based oxide superconductor.

(Problem to be solved by the invention) However, the above B1-Pb-8r-Ca-Cu-0
oxide superconductor (hereinafter referred to as bismuth-based superconductor)
ii, a small amount of 2212 phase in addition to 2223 phase.

Foreign phases such as CazPbO4 tend to remain, and long firing is required to increase the content of the 2223 phase.

Among the above-mentioned different phases, the 2212 phase has a low THero of about 80, but it can be easily generated and can be applied at liquid nitrogen temperature (77 K). However, if a large amount of CazPbO<, which is not a superconductor, remains, there is a problem that the superconductor content decreases, causing a decrease in critical current density (hereinafter referred to as Jc).

Furthermore, there is a problem that F)Jc tends to decrease due to the application of a magnetic field, and it is also difficult to increase the density of the sintered body, and there has been a strong demand for improvement in the bonding between particles.

An object of the present invention is to provide a superconductor and a method for manufacturing the same that are free from the above-mentioned problems.

(!!Means for Solving the Problem) The present invention provides an oxide containing bismuth, strontium, calcium, and copper as main components, and a composition containing 10 to 3 silver in the entire composition.
The amounts of silver and palladium shown above are added to a superconductor containing 5% by weight and 0.1 to 2% by weight of palladium, and a mixed powder of bismuth, strontium, calcium, and copper, mixed uniformly, and then fired. Concerning a method for manufacturing superconductors.

In the present invention, there is no particular restriction on the blending ratio of bismuth, strontium, calcium, and copper, but B
i: Sr: Ca: Cu: If the atomic ratio is 2:2:12 or 2:2:2:3, it will easily form a superconductor, so if it is preferably 1% and 2:2:2:3, then the 10～
It is preferable to replace 30% of lead with lead because a superconductor with a high Tg0 can be obtained.

The amount of silver added is in the range of 10 to 35% by weight in the total composition. If it is less than 10% by weight, the effect as an auxiliary agent for uniformizing the effect of adding palladium is low, and if it exceeds 35% by weight, the effect is reduced. However, the volume fraction of the superconductor decreases.

The amount of palladium added is in the range of 0.1 to 2% by weight in the whole composition, and if it is less than 0.1% by weight, palladium has little effect of increasing Jc and improving magnetic field characteristics, and 2% by weight.
If the value exceeds 1, the disadvantage is that it becomes expensive.

Among the raw materials constituting the superconductor, silver is not particularly limited as long as silver powder, oxidized scissors, silver chloride, nitrate scissors, etc. are used, and the material becomes silver units after firing.

Palladium is also available in addition to palladium powder.

There is no particular restriction as long as palladium oxide or the like is used and the material becomes pure palladium after firing.

Other raw materials listed above such as bismuth, lead, strontium,
There are no particular restrictions on the raw materials (starting raw materials) containing calcium and copper; for example, oxides, carbonates, oxalates,
One or 211 of acetates, nitrates, metal alkoxides, etc.
The above is used.

There are no particular restrictions on the method of mixing the raw materials shown above, but 1
For example, 9 A method in which a ball mill made of synthetic resin is filled with balls coated with synthetic resin, a solvent such as ethanol, and raw materials and wet-mixed, a coprecipitation method in which a coprecipitated product is obtained after dissolving the raw materials in a solvent, and an alkoxide method. A sol-gel method or the like can be used in which a sol is prepared by hydrolyzing raw materials such as, and the sol is turned into a gel.

The firing temperature and firing time are appropriately selected depending on the blending ratio of each raw material and the atmosphere, but Bi: Sr: Ca:
When Cu has an atomic ratio of 2:2:1:2, it is 810 to 90
5 to 50 hours at a temperature of 0°C, Bi: Sr: Ca
・If Cu is approximately 2:2:2°3 and some of the bismuth is replaced with lead, 845 soil at 20°C, preferably 84
5. It is preferable to bake at a temperature of 10° C. for 20 to 200 hours.

There are no particular restrictions on the method of adding chains and palladium, but 2. For example, using fine powder of a raw material containing silver and palladium, a dry or wet method using a ball mill, mortar, etc., with a mixed powder of raw materials containing bismuth, strontium, calcium, and copper. One method is to mix and homogenize. Another method is to add an aqueous solution of raw materials containing silver and palladium to a mixed powder of raw materials containing bismuth, strontium, calcium, and copper, and then uniformly heat the solution.

(Example) The present invention will be explained in detail below.

Example 1 Bismuth trioxide (manufactured by Kojundo Kagaku Kenkyusho, purity 99.9%), -lead oxide so that the ratio of bismuth, lead, strontium, calcium, and copper was as shown in Table 1 in atomic ratio. (yellow) (manufactured by Wako Tsumugi Pharmaceutical.

Reagent %li&), strontium carbonate (rare metallic crack, purity 99.9%), calcium carbonate (manufactured by Kojundo Kagaku Kenkyusho, purity 99.9%), and cupric fluoride (manufactured by Kojundo Kagaku Kenkyusho, purity 99.9ch).

It was used as a starting material.

Next, the above starting materials were coated with a synthetic resin in a synthetic resin ball mill, filled together with steel balls and methanol, and mixed and pulverized for 60 hours at 50 revolutions per minute. After this, remove the crushed material from the ball mill and
After drying at 0°C for 24 hours, this was placed on an alumina baking plate and calcined in the air at 800°C for 24 hours using an electric furnace.
Then, it was coarsely ground in a mortar and poured into a synthetic resin ball mill together with Luconia moxibustion balls and methanol.

It was pulverized for 48 hours at 50 revolutions per minute and dried to obtain a powder for synthesis.

Thereafter, the synthesis powder was placed on an alumina baking plate, heated in an electric furnace at a temperature of 840°C for 50 hours in a low oxygen pressure atmosphere with a volume ratio of 02:N2''1:10, and then cooled to form a bismuth-based powder. A superconductor was synthesized.Then, it was coarsely pulverized in a mortar, and then filled in a 9-synthetic resin ball mill with zirconia balls and methanol, and pulverized for 48 hours at 50 revolutions per minute to obtain a pulverized product. This crushed material89
9% by weight of silver powder (manufactured by Noble Metals, product name AY-6080)
, average particle size 0.8 μm) and 0.1 weight % palladium powder (manufactured by Tokuriki Chemical Co., Ltd., average particle size 1.0 μm) were added, and the mixture was further mixed for 5 hours to make it uniform.

After drying, the obtained powder was heated to a diameter of 30 cm under a pressure of 147 MPa.
After molding into pellets with a thickness of IIm, the pellets were fired at 840° C. for 10 hours in the air to obtain a superconductor.

Example 2 Bismuth, strontium, carunium, and copper arsenate were weighed so as to have the atomic ratio shown in Table 1, and the same steps as in Example 1 were followed to synthesize a bismuth-based superconductor. The raw materials shown above were from the same manufacturer as in Example 1. same as below.

Next, the bismuth-based superconductor obtained above was wet-pulverized in the same manner as in Example 1, and 74.25% by weight of this pulverized material was mixed with 25% by weight of the same silver powder and palladium powder as used in Example 1. Added 0.75% by weight.

Following the same steps as in Example 1, superconductors were produced.

Example 3 Bismuth, lead, strontium, calcium, and copper were weighed so as to have the composition shown in Table 1 in atomic ratio, and the same steps as in Example 1 were followed to synthesize a bismuth-based superconductor.

Next, the bismuth-based superconductor obtained above was wet-pulverized in the same manner as in Example 1, and 69.4% by weight of this pulverized material was mixed with 30% by weight of silver powder and palladium powder similar to those used in Example 1. 0.6% by weight was added, and the same steps as in Example 1 were carried out to obtain a superconductor.

Example 4 34% by weight of silver powder similar to that used in Example 1 and 2% by weight of palladium powder were added to 64% by weight of the ground material obtained in Example 2, and the same steps as in Example 1 were carried out. Through this process, a superconductor was obtained.

Comparative Example 1 10% by weight of the same silver powder as that used in Example 1 was added to 90% by weight of the pulverized material obtained in Example 1, and the same steps as in Example 1 were carried out to obtain a superconductor.

Comparative Example 2 25% by weight of silver powder similar to that used in Example 1 was added to 75% by weight of the pulverized material obtained in Example 2, and the same steps as in Example 1 were carried out to obtain a superconductor.

Comparative Example 3 30% by weight of silver powder similar to that used in Example 1 and 2% of palladium powder were added to 67.5% by weight of the pulverized material obtained in Example A.
．． A superconductor was obtained by adding 5% by weight and following the same steps as in Example 1.

Comparative Example 4 34% by weight of silver powder and 3% by weight of palladium powder similar to those used in Example 1 were added to 63% by weight of the pulverized material obtained in Example 2, and the same steps as in Example 1 were carried out. A superconductor was obtained.

Next, the superconductor obtained in each example and comparative example was
It was processed into a rectangular parallelepiped with a width of 3 m and a thickness of 1 m, and the temperature change in resistance was measured using a four-terminal method to determine TZero. Jc at liquid nitrogen temperature (77,3K) using the same sample as above.
6, and 'Jco, as in a magnetic field of 0.05 Tesla in liquid nitrogen.

These measurement results and Jc (ratio of LO5 to Jc6) are shown in Table 1.

Note that in the above composition, the amount of O (oxygen) is determined by the amount of copper and the oxidation state of copper. However, it was not possible to measure the oxidation state strictly and accurately, so it was expressed as X in the present invention.

Also, Example 1. In Comparative Example 1 and Comparative Example 3, 25 molti in bismuth was replaced with lead, and in Example 3.

The composition was such that 20 molti of bismuth was replaced with lead.

Table 1 shows superconductors that are examples of the present invention.

When T: ero is 80 or more, it is shown that the decrease in Jc due to the application of a magnetic field is small. On the other hand, the superconductor of the comparative example has r):erO of 79 or higher.

It is shown that the decrease in Jc is large due to the application of a magnetic field.

(Effect of the invention) Superconductor Jf1 according to the invention. T: The decrease in erO is small, and the decrease in Jc due to the application of a magnetic field is small.

Agent: Patent attorney Kuninobu Wakabayashi!

Claims (1)

[Claims] 1. A superconductor comprising an oxide containing bismuth, strontium, calcium and copper as main components, and a total composition containing 10 to 35% by weight of silver and 0.1 to 2% by weight of palladium. body. 2. The superconductor according to claim 1, wherein a part of bismuth is replaced with lead. 3. A method for producing a superconductor, which comprises adding silver and palladium in the amounts shown in claim 1 to a mixed powder of bismuth, strontium, calcium, and copper, mixing the mixture uniformly, and then firing.