JPH0442815A - Oxide superconductor and its production - Google Patents

Abstract

PURPOSE:To improve critical temperature by weighing each raw material containing Ag, Pd, Bi, Pb, Sr, Ca, Mg, Ba and Cu, blending and burning to give a composition containing Ag and Pd and shown by a specific formula. CONSTITUTION:Each raw material powder of metal, oxide, carbonate or sulfate of Ag, Pd, Bi, Pb, Sr, Ca, Mg, Ba and Cu is weighed to give a given atomic ratio and the raw materials are blended. Then the blended powder is calcined at 780-870 deg.C, ground, molded and burnt in the atmosphere or in a low oxygen pressure atmosphere at 800-870 deg.C to give an oxide superconductor containing 10-35wt.% Ag and 0.1-2wt.% Pd, comprising a composition shown by the formula (A is 0.01-0.35, B is 0.6-1.3, B' is 0.3-0.9, C is 0.010.3 and D is 0.01-0.3 and figure is atomic ratio) and having a high critical temperature.

Description

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

(Conventional technology) As a conventional oxide superconductor, in 1988.

There is a Bi-8r-Ca-Cu-Q-based oxide superconductor whose main components are bismuth, strontium, calcium, and copper, which was discovered by the above-mentioned research staff at the Institute of Metals and Materials Technology. 8r -Ca -Cu
O-based oxide superconductors are a critical source with zero electrical resistance.
(hereinafter referred to as T-ero) is around 10K, and T/
-Ba-Ca-Cu-0-based oxide superconductor is known to have the second highest content.

Bi-8r-Ca-Cu-0 based oxide superconductor is TI! -Ba-Ca-Cu~0-based oxide superconductor, it has a characteristic of being less toxic than the 0-based oxide superconductor, but in the crystal phase, Tcer0 is 110 and Tonal 2223 phase Lt) Mo, T tongue er' is 80 and 2212 phase. Alternatively, there is a drawback that a 2201 phase with Ter0 of 20 is likely to be generated. Later, the Japanese Journal Op Applied
Fish 7 Kusu (Japanese Journal
of Applied Physics) Vol, 2
7, No. 6 (published June 1988).

As shown on pages L1041 to L1043, lead was added and fc Bi -Pb -8r -Ca -Cu -0
2 in the oxide superconductor (hereinafter referred to as Bi-based superconductor)
It became clear that a large amount of 223 phase was obtained.

(Problem to be solved by the invention) It takes a long time to generate a lot of 2223 phase.

For example, 100 hours of firing is required.

On the other hand, Bi-based superconductors contain Ca 2 P in addition to the 2223 phase.
Different phases such as b 041 Pb Cu 02 tend to remain.

Ca, Pb04. When a different phase such as PbCuO2 coexists in the 2223 phase, there is a problem that the superconductor content decreases and the critical current density (hereinafter referred to as Jc) decreases.

In addition, compared to Bi-based superconductors and Y-Ba-Cu-Q-based superconductors, there is a problem in that Jc is more likely to decrease when a magnetic field is applied, which is disadvantageous in terms of application to superconducting electromagnets and superconducting magnetic shielding materials. . Furthermore, it is difficult to increase the density of the sintered body, and there has been a strong demand for improvement in the connections between the nine particles.

The object of the present invention is to provide an oxide superconductor and a method for producing the same that are free from the above-mentioned problems.

(Means for Solving the Problems) The present invention contains 10 to 35% by weight of silver and 0.1% by weight of palladium.
~2% by weight, and has the general formula Bi+-APbASrnCan'Mgo Bap
Cuto*ct! s Ox (however, A=0.01~0.
35. B=0.6~1.3, B'=0.3~0.9
．． C=0.01-0.3. D=0.01-0.3. (Numbers represent atomic ratios) An oxide superconductor with the composition shown below, and silver, palladium, bismuth, and lead so as to have the above composition.

The present invention relates to a method for producing an oxide superconductor in which raw materials containing strontium, calcium, magnesium, barium, and copper are weighed, mixed, and then fired.

In the present invention, in addition to silver powder, silver oxide, silver chloride, silver nitrate, etc. can be used as the silver, and there is no particular restriction as long as it becomes a simple substance 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.

Silver is required to be contained in the oxide superconductor in a range of 10 to 35% by weight, and if it is less than 10% by weight, the effect as an auxiliary agent for uniformizing the effect of adding palladium is low;
If the amount exceeds 5% by weight, this effect is obtained, but the volume fraction of the superconductor decreases.

On the other hand, palladium is 0.1 to 2% by weight in the oxide superconductor.
If the content is less than 0.1% by weight, the effects of increasing Jc and improving the magnetic field characteristics by palladium will be small, and if it exceeds 2% by weight, the disadvantage will be that it becomes expensive.

There are no particular restrictions on the raw materials containing bismuth, lead, strontium, calcium, magnesium, barium, and copper in addition to the above components, but for example, one of oxides, carbonates, nitrates, etc., or one of Vi2i or more may be used.

General formula Bi l-PbASrBCaB' Mgc B
In aDCuto thCLtsQx, the atomic ratio of AI- is set in the range of 0.01 to 0.35, and if it is less than 0.01, a medium-temperature phase near gZero of 80 tends to be generated, so a high-temperature phase near 10K is generated. The amount decreases,
If it exceeds 0.35, C is formed by an oxide of lead and calcium.
A large amount of foreign phases such as a2Pb04 is generated, and T%el''o decreases.

The atomic ratio of B is in the range of 0.6 to 1.3, and if it is less than 0.6, the range of firing conditions in which a high-temperature phase is generated is narrow, and the electrical resistance stabilizes at around 110 and becomes zero. If it exceeds 1.3, foreign phases other than superconductors are likely to be generated, and rpZero decreases.

B' is in the range of 0.3 to 0.9 in terms of atomic ratio; if it is less than 0.3, no significant effect will be observed, and if it exceeds 0.9, a different phase other than the superconductor is likely to be produced.

The atomic ratio of C and D is in the range of 0.01 to 0.3.

If it is less than 0.01, no significant effect can be expected, and 0.3
If the value exceeds 100%, a different phase other than the superconductor is likely to be generated.

There are no particular restrictions on the method of mixing the raw materials.

For example, a method of filling a synthetic resin-coated ball mill with a solvent and raw materials such as Cypol, ethanol, and methanol and wet-mixing the same, a coprecipitation method of obtaining a coprecipitated product after dissolving the solvent Nakae raw materials, A sol-gel method or the like can be used in which a sol is prepared by hydrolyzing a raw material such as an alkoxide, and the sol is turned into a gel.

In the present invention, calcining is performed if necessary after mixing.

In the calcination conditions, the calcination temperature and time are appropriately selected depending on the blending ratio of each raw material, etc.
Preferably, the calcination is carried out for 20 to 200 hours, and the calcination atmosphere is not particularly limited and may be in the air, oxygen atmosphere, vacuum, reducing atmosphere, or the like.

There are no particular restrictions on crushing and molding, and conventionally known methods may be used.

Regarding the firing conditions, the firing temperature is appropriately selected depending on the blending ratio of each raw material, etc.
It is light and heavy to be fired for ~60 hours, and the firing atmosphere is air, air current, or low oxygen pressure atmosphere (with an oxygen content of 1 to 20 volumes, preferably 2 to 20 volumes).
It is preferable to bake within the range of .

The amount of O (oxygen) in the composition of the present invention is determined by the amount of CuO and the oxidation state of Cu. However, it is not possible to accurately measure the oxidation state, so it is represented by X in the present invention.

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

Examples 1-5 1:' Sumath, lead, strontium, magnesium.

Pisfus trioxide (manufactured by Kojun Kagaku Kenkyushin, purity 99.9%) and strontium carbonate (manufactured by Rare Metallic, purity 99.9) were prepared so that the ratio of barium, calcium and copper was as shown in Table 1 in atomic ratio. %).

Magnesium oxide (manufactured by Kojundo Kagaku Kenkyu, purity 99.9)
%), barium carbonate (newly manufactured by High Purity Chemical Research).

Calcium carbonate (manufactured by Kojundo Kagaku Kenkyushin, purity 99.9%), and cupric oxide (manufactured by Kojundo Kagaku Kenkyushin, purity 99.9%) were weighed and used as starting materials.

Next, the above starting materials were filled in a synthetic resin ball mill together with steel balls coated with synthetic resin and methanol, and mixed for 72 hours at 50 revolutions per minute. After drying, place it in an alumina sagger and heat it in the air at 800°C using an electric furnace.
After being calcined for 0 hours and then coarsely ground in a mortar, it was placed in a synthetic resin ball mill together with zirconia balls and ethyl acetate to have the composition shown in Table 1 in terms of atomic ratio (lead monoxide) (yellow).

(purity: 99.9%) was weighed out and filled, mixed 24 hours a day at 50 revolutions per minute, and then dried to obtain a composition for oxide superconductor.

After this, the composition for oxide superconductor was press-molded at a pressure of 147 MPa, and then Ox:N! at a volume ratio of 0! =1:1
The material for an oxide superconductor with a thickness of 11 m1 was obtained by firing at 835 °C for 100 hours in a low oxygen pressure atmosphere of 0.0 °C.

After that, the above-mentioned oxide superconductor material was coarsely pulverized in a mortar, then filled in a synthetic resin ball mill with zirconia balls and ethyl acetate, and pulverized for 48 hours at 50 revolutions per minute, followed by silver powder and palladium. Add the powder so that it has the composition shown in Table 1.

Mixed for an additional 5 hours until uniform. The silver powder is made by China Precious Metals, and the palladium powder is made by Iiriki Honten, and both have a purity of 9.
A powder having a size of 9.9 inches or more and an average particle size of 2±1 μm was used.

After drying, the obtained powder was heated to a diameter of 30 mm under a pressure of 147 MPa.
After forming into pellets with a thickness of 1 m, the pellets were fired at 480° C. for 10 hours in the air to obtain oxide superconducting sintered bodies.

Comparative examples 1 to 6 Weigh each raw material so that it has the composition shown in Table 1.

An oxide superconductor was obtained through the same steps as in the example series.

Next, the oxide superconductor obtained in each example and comparative example was
It was processed into a rectangular parallelepiped of 0 g x @ 3 mm x 1 stroke in thickness, and the temperature change in resistance was measured using the four-probe method to determine Tlero. Furthermore, using the same sample as above, JCO was measured at liquid nitrogen temperature (77.3 K), and Jcαoi was measured in liquid nitrogen in a magnetic field of 0.05 Tesla. These measurement results and the ratio of JcllLo5 to Jco are shown in Table 1.

Claims (2)

[Claims] 1. 10-35% by weight of silver and 0.1-2% of palladium
Contains weight%, and general formulas ▲ Numerical formulas, chemical formulas, tables, etc. ▼ (However, A = 0.01 ~ 0.35, B = 0.6 ~ 1.3,
B'=0.3~0.9, C=0.01~0.3, D=0
．． An oxide superconductor having a composition of 01 to 0.3 (numbers represent atomic ratios). 2. Silver, palladium,
A method for producing an oxide superconductor, which comprises weighing raw materials including bismuth, lead, strontium, calcium, magnesium, barium, and copper, mixing them, and then firing them.