JPH04104940A - Oxide superconductor and production thereof - Google Patents

Abstract

PURPOSE:To provide the subject superconductor improved in magnetic field dependency by mixing raw materials containing Tl, Ba, Ca, Cu, Pt and/or Pd so as to contain the Pt and/or Pd and to form a composition represented by the specific formula, and subsequently firing the composition. CONSTITUTION:The respective powdery raw materials of Ba, Ca, and Cu are weighed in prescribed amounts, mixed with each other, preliminarily fired and subsequently ground. The ground mixture is mixed with a prescribed amount of a powdery Tl raw material and ground to form a composition for oxide superconductors. The composition is press-molded and fired in a lidded ceramic container to prepare a material for the oxide superconductors. The material is ground and homogeneously mixed with prescribed amount of Pt powder and/or Pd powder. The mixture is press molded and subsequently fired at 800-900 deg.C in the atmosphere to provide an oxide superconductor containing the Pt and/or the Pd in an amount of 0.1-5wt.%, having a composition of the formula (A=1.6 to 2.2, B=1.8 to 2.4, 0.9<=B/A<=1.4; the numbers are each an atomic ratio) and improved in the dependency of the superconductive characteristics on magnetic field.

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) Tr-Ba-Ca-Cu-0 based oxide superconductor.

Generally, starting materials including thallium (T/), barium (Ba), calcium (Ca), copper (Cu), etc. are mixed simultaneously or Ba-Ca-Cu-0, Ba-Cu
It can be obtained by mixing a compound such as -0, Ca -0sCu-0 and a T//compound to prepare a raw material for a superconductor, and then molding and firing the raw material.

TI! -Ba-Ca-Cu-0 based oxide superconductor.

It is known that this material has a high critical temperature (hereinafter referred to as Tc) of 120° C. or higher.

(Problem to be solved by the invention) However, T/-Ba-Ca produced by the above method
-Cu-0 based oxide superconductors (hereinafter referred to as T/based superconductors) have many voids and are difficult to obtain with high density. For this reason, the connections between crystal grains are poor, and superconducting properties such as Tc *critical current density (hereinafter referred to as Jc) are reduced,
In addition, mechanical strength and the like are also reduced.

In addition to the heat treatment process, as a method to improve the above drawbacks,
A generally known method is to introduce processes such as rolling, crushing, and press forming, combine these processes, and repeat the process several times. If this method is used, the superconducting properties such as *TC and Jc can be improved to some extent, but this method increases the number of manufacturing steps.

The problem is that it is complex.

Furthermore, Tj compounds easily evaporate and are expensive.

Therefore, it is important to suppress the evaporation of T/.

When the heat treatment process increases, TI! It is difficult to suppress the evaporation of T/, and composition shifts are likely to occur due to the evaporation of T/.

In general, it is said that Jc is more likely to decrease when a magnetic field is applied than T/based superconductors and Y-Ba-Cu-0 based oxide superconductors. Improve problems such as.

It is essential to introduce a stop point for magnetic flux.

An object of the present invention is to provide an oxide superconductor in which *TC+JC, etc. do not decrease, or even if it decreases, it decreases only slightly, and the magnetic field dependence of Jc is improved, and a method for producing the same.

(Means for Solving Problem 11) As a result of various studies on the above-mentioned drawbacks, the present inventors found that by incorporating platinum and/or palladium into a conventional Tr-based superconductor, + T: ero, Jc, etc. They discovered that this method is effective in improving magnetic field characteristics, etc., and completed the present invention.

The present invention contains 0.1 to 5% by weight of platinum and/or palladium.
and has the general formula Tl 1.4-2BaACanCuz
s~a, 5Ox (however, A=1.6~22.B=1.
8-44.0.9≦B/A≦1.4. After weighing the oxide superconductor having the composition shown in (numbers represent atomic ratios) and each raw material containing platinum and/or palladium and thallium, barium, calcium and copper so as to have the above composition, and then mixing them. This invention relates to a method for producing an oxide superconductor to be fired.

In the present invention, there are no particular limitations on the raw materials (starting raw materials) containing thallium, barium, calcium, and copper, which are the main components constituting the oxide superconductor.

For example, one of these oxides, carbonates, nitrates, oxalates, etc.
A species or two or more species may be used.

General formula Tl1.4~2BaACai+Cuzs~11
．． At 60X.

Thallium has an atomic ratio in the range of 1.4 to 2, and outside this range it forms a high temperature phase with Tc of 120 or more (T/x
Batcatcus Oto phase, 2223 phase) production amount decreases.

The atomic ratio of barium prisoners is said to be in the range of 1.6 to 22.

If it deviates from this range, crystal phases other than the superconductor phase are likely to be formed, and the superconductor content decreases.

Calcium (B) has an atomic ratio in the range of 1.8 to 24, and if it is less than 1.8, the amount of high temperature phase produced decreases.

If it exceeds 24, crystal phases other than the superconductor phase tend to form, and the superconductor content decreases.

Copper has an atomic ratio in the range of 28 to &6; when it is less than 28, the amount of high-temperature sum produced decreases, and when it exceeds λ6, the superconductor content decreases.

Platinum and/or palladium is present in the oxide superconductor at a concentration of 0.
It is required to be contained in the range of 1 to 5 weight, and 0
．． If it is less than 1 weight, platinum and/or palladium will have little effect on improving magnetic field characteristics.

If the weight exceeds 5 -, there will be a disadvantage that it will be expensive.

As platinum, 9M platinum or the like may be used in addition to platinum powder, and there are no particular limitations as long as the material becomes pure platinum 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.

There are no particular restrictions on the method of adding platinum and/or palladium, but for example, they can be mixed and homogenized in a dry or wet manner with the powder of the oxide superconductor material using a ball mill, sieve machine (automatic mixer), mortar, etc. There are methods such as adding an aqueous solution of platinum and/or palladium to the material for an aluminide superconductor and then uniformly heating the solution.

There are no particular restrictions on the mixing method; 9 For example, there is a method of dry mixing in a sieve machine. 9 A ball coated with a synthetic resin is filled in a synthetic resin 7-ball mill with a solvent such as ethanol, methanol, etc. and raw materials.

Wet mixing is preferred.

Firing is preferably performed in a closed container.

As the closed container, it is preferable to use a container made of ceramics such as alumina or magnesia.

The firing temperature is appropriately selected depending on the blending ratio of each raw material, but it is preferable to fire in the range of 800 to 900°C, and the firing atmosphere is in the air, in an air stream, or in a low oxygen pressure atmosphere (oxygen It is preferred that the firing be carried out at a content in the range of 1 to 20 volumes, preferably 2 to 20 volumes.

In the composition of the present invention, the amount of 0 (aI element) is determined by the amount of CuO and the oxidation state of Cu. However, the oxidation state of K cannot be measured strictly and accurately, so it is expressed by X in the present invention.

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

Example 1 Bad (manufactured by Kojundo Kagaku Kenkyusho, purity 99% or higher) and Cab (manufactured by Kojundo Kagaku Kenkyusho, purity 9) were prepared so that the ratios of barium, calcium and copper were as shown in Table 1 in atomic ratio.
9.996) and Cub (manufactured by Kojundo Kagaku Kenkyusho, purity 9
9.9%) was weighed and used as a starting material.

Thereafter, the above starting materials were mixed for 30 minutes using a strainer. The obtained mixed powder was preliminarily calcined at 900° C. for 10 hours in the air using an electric furnace.

The mixture was ground for 30 minutes using a grinder.

Next KT Mu Os (manufactured by High Purity Chemical Research, purity 99.9%)
were weighed so as to have the composition shown in Table 1, added to the above-mentioned pulverized material, mixed uniformly in a mortar, and pulverized to obtain a composition for oxide superconductor.

The obtained composition for oxide superconductor was pressed with a 100%
A molded product with a thickness of 2 m was obtained by molding at a pressure of MPa. This molded body was then fired at 870° C. for 3 hours in an alumina container with a lid to obtain a material for an oxide superconductor.

After pulverizing the obtained oxide superconductor material into a powder in a mortar, platinum powder (manufactured by Tokuriki Honten, purity 99.9g) and/or palladium powder (manufactured by Tokuriki Honten, purity 99.91G) was first ground. It was weighed so as to have the composition shown in the table, added to the above-mentioned pulverized powder, and mixed uniformly in a mortar.

The obtained powder was molded into pellets with a diameter of 20 m and a thickness of 1 cm using a mold press at a pressure of 150 MPJl, and then 87 cm in the air.
An oxide superconductor was obtained by firing at 0° C. for 5 hours.

Next, add the oxide superconductor obtained above to a length of 20 cm x width of 1 cm.
It was processed into a rectangular parallelepiped with a thickness of 1 m, and the temperature change in electrical resistance was measured using the four-terminal method to determine Tc.

Also, using the same sample as above, liquid nitrogen temperature (77K)
At the same time, JCO was measured at liquid nitrogen temperature and Jc (11) was measured in a magnetic field of 0.1 Tesla.These results are shown in Table 1 below. There is little decrease in Tc compared to oxide superconductors,
It is also shown that Jc does not decrease and the decrease in Jc due to the application of a magnetic field is small (effects of the invention) The oxide superconductor of the present invention does not decrease in Tc, Jc, etc. The decrease in Jc due to the application of a magnetic field is very small, and it is an industrially very suitable oxide superconductor.

6-+Ding Knee Agent Patent Attorney Kuni Wakabayashi 11’

Claims (2)

[Claims] 1. Contains 0.1 to 5% by weight of platinum and/or palladium, and has the general formula Tl_1_. _4_～_2Ba_ACa_
BCu_2_. ＿８＿～＿３＿． _6O_X (However, A=
1.6-2.2, B=1.8-2.4, 0.9≦B/A
An oxide superconductor having a composition of ≦1.4 (numbers represent atomic ratios). 2. A method for producing an oxide superconductor, which comprises weighing raw materials containing platinum and/or palladium, thallium, barium, calcium, and copper so as to have the composition according to claim 1, and then mixing and firing.