JPH0465345A - Oxide superconductor composition, production of oxide superconductor raw material using the same and production of oxide superconductor - Google Patents

Abstract

PURPOSE:To obtain an oxide superconductor composition capable of easily obtaining a superconductor having a high content of a high-temp. phase by mixing Bi, Pb, Sr, Ca, Cu, Mg and Ba in a specified ratio, then calcining and crushing the mixture. CONSTITUTION:The raw materials each consisting essentially of bismuth, lead, strontium, calcium, copper, magnesium and barium in an atomic ratio of (1.2 to 22):(0.2 to 1):(1.4 to 2.2):(1.6 to 2.4):(2.8 to 4):A:B (where A<=1 and B<=0.6) are weighed. The raw materials are mixed, calcined and crushed to obtain the desired oxide superconductor raw material. The raw material is sintered to obtain an oxide superconductor.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a composition for an oxide superconductor, a method for producing a raw material for an oxide superconductor using the composition, and a method for producing an oxide superconductor.

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

A Bi-8r-Ca-Cu-0-based oxide superconductor whose main components are bismuth, strontium, calcium, and copper, discovered by the above-mentioned research staff at the Institute of Metals and Materials Technology, and the substitution or addition of these elements. B1-8r -CJL -Cu containing bismuth, strontium, calcium, steel and magnesium as main components obtained by
- Mg-0 based oxide superconductor, Bi whose main components are bismuth, lead, strontium, calcium and steel -
Pb-8r-Ca-Cu-0-based oxides [4 substances, Bi-Pb-8r whose main components are bismuth, lead, strontium, calcium, steel, and barium
-Ca-Cu-Ba-Oio acid oxidized superconductor ring is generally known.

(Problem to be Solved by the Invention) However, in the above-mentioned bismuth-based oxide superconductor, a high-temperature phase with a critical temperature (hereinafter referred to as yzero) near 110, a medium-high phase near 80, etc. are likely to be generated simultaneously. It is difficult to convert the phase to a single phase.

That is, among bismuth-based oxide superconductors, Bi -8r
-Ca-Cu-0-based oxide superconductors have the disadvantage that high-temperature phases are easily formed, and crystal phases other than the medium and superconductor phases are likely to form. M
The g-0 series oxide superconductor is 1, for example, Japanese
Journal of Applied Physics (Jap
anese Journal of AppliedP
hysics) Vol. 1, 27, No. 12 (1988
Published in December).

As shown on pages L2330 to L2332, as the Mg content increases, 7zero decreases, which is a drawback.

Furthermore, the Bi-Pb-8r-Ca-Cu-0 based oxide superconductor has a narrow firing temperature range in which many high-temperature phases are formed.
The drawback is that it is difficult to obtain a product with a high content of high-temperature sum.

Furthermore, Bai-Pb-8r-Ca-Cu-0 system
The added Bi-Pb-8r-Ca-Cu-Ba-0 based oxide superconductor was described in Japanese Journal of Applied Physics (Japanese J
our own of Applied Physics
) Vo1, No. 27.12 (published December 1988),
As shown in the negative values of L2296 to L2299, the addition of Ba increases Tzero.

Bacuo2. BaB10
．． This has the disadvantage that different phases such as the following are generated.

On the other hand, as a means of investigating the formation state and content of superconductors, there is a method of evaluating the actual content of superconductors by identifying the crystal phase by X-ray diffraction and measuring magnetic susceptibility.

However, with X-ray diffraction, although it is possible to identify the crystalline phase, it is difficult to determine whether the material exhibits superconductivity or to measure the absolute amount of the superconducting phase.

When measuring magnetic susceptibility, foreign matter other than the superconductor phase may be measured as a high-temperature phase due to the shielding effect, so it is necessary to use the X@ diffraction method to identify the crystal phase and measure the magnetic susceptibility. Must be.

In the present invention, the sintering bias region in which many high-temperature phases are generated is expanded based on the evaluation of the superconductor content determined from powder X-ray diffraction and magnetic susceptibility. That is, the present invention provides a composition for superconducting compounds that can easily obtain a composition with a high content of high-temperature phase, a method for producing raw materials for oxide superconductors using the composition, and a method for producing oxide superconductors. The purpose is to

(Means for Solving the Problems) In order to achieve the above object, the present inventors have conducted extensive research and found that in addition to raw materials (starting raw materials) containing bismuth, strontium, calcium, and copper, lead, magnesium, and barium are used. A composition containing raw materials (starting materials) added or replaced is used as an oxide superconductor composition, and by manufacturing an oxide superconductor using the composition, the superconductor content in the high temperature phase can be reduced. The present inventors have discovered that the firing temperature range in which the temperature is high and a large number of high-temperature phases are formed is widened, and the present invention has been completed.

The present invention includes bismuth, lead, strontium, calcium,
The main components are copper, magnesium and barium, and their atomic ratio is bismuth:lead nystrontium:calcium:N4:magnesium:barium from 1.2 to Z2:0.
2-1:1.4-Z2:1.6-44:28-42A:
A composition for an oxide superconductor that is B (where A≦1.8≦0.6), bismuth, lead, and strontium so as to have the above composition.

A method for producing a raw material for an oxide superconductor, in which each raw material containing calcium, steel, magnesium, and barium is weighed, mixed, calcined, and crushed; and an oxide superconductor, in which the raw material for an oxide superconductor is fired. Concerning the manufacturing method.

In the present invention, the main components constituting the composition for oxide superconductor are bismuth, lead, nutronotium, calcium, steel,
There are no particular restrictions on the raw materials (starting raw materials) containing magnesium and barium.

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

In the present invention, bismuth has a W ratio of 1.2 to Z2.
Preferably, it is in the range of 1.3 to zO, and if it deviates from this range, crystal phases other than the mesophilic phase and superconductor phase are likely to be generated.
It becomes difficult to obtain a superconductor containing many high-temperature phases.

Lead has an atomic ratio of 0.2 to 1, preferably ¥i0.3 to 0.8
If it deviates from this range, crystal phases other than the intermediate phase and superconductor phase are likely to be generated, making it difficult to obtain a superconductor containing a large amount of high-temperature phase.

Strontium has an atomic ratio in the range of 1.4 to 2-2, preferably 1.5 to 2, and if it deviates from this range, a crystalline phase other than a mesotemperature phase or a superconductor phase is likely to be generated.

It becomes difficult to obtain a superconductor containing many high-temperature phases.

Calcium has an atomic ratio of 1.6 to Z4, preferably 1.8
-22.2 If it deviates from this range, crystal phases other than the intermediate temperature phase and the superconductor phase are likely to be generated.

It becomes difficult to obtain a superconductor containing many high-temperature phases.

Steel has an atomic ratio of 28 to 4, preferably z9 to a, 6. If the atomic ratio is outside this range, a medium temperature phase or a crystalline phase other than the superconductor phase is likely to be formed, and a superconductor containing a large number of high temperature phases cannot be obtained. It becomes difficult to get caught.

Magnesium (A) has an atomic ratio of 1 or less, preferably 0,
It is set in the range of 1 to 0.6, and if it exceeds 1, the superconducting properties tend to deteriorate, such as a decrease in rpzero.

Barium (B) has an atomic ratio of α6 or less, preferably 0.0
It is set in the range of 8 to 0.4, and if it exceeds 0.6, crystal phases other than the superconductor phase tend to form.

Although there are no particular restrictions on the mixing method, it is preferable to fill a ball mill made of synthetic resin with a ball coated with synthetic resin, a solvent such as ethanol or methanol, and raw materials, and perform wet mixing.

Although the calcination temperature is appropriately selected depending on the blending ratio of each raw material, it is preferable to calcinate in the range of 750 to 900°C, and the atmosphere is air.

Calcination can be performed in an oxygen atmosphere, a vacuum, a reducing atmosphere, etc., and there are no particular limitations.

There are no particular restrictions on pulverization (any conventionally known method).

For example, it may be ground using a mortar or the like, or it may be wet ground by filling a synthetic resin ball mill with zirconia balls, a solvent such as ethanol or methanol, and raw materials.

The firing temperature is appropriately selected depending on the blending ratio of each raw material, but it is preferable to perform the firing in the range of 800 to 900°C, and the firing atmosphere is air, air current, or low oxygen pressure atmosphere (oxygen-containing). It is preferable to perform firing in a range of 1 to 20 volumes, preferably 2 to 20 bodies per side.

Among the crystal phases of the superconductor layer, the Takatsuki phase refers to the crystal phase (B115r2Ca, Cu,
01° phase), and the Zhongtan phase is a crystalline phase (B 1lsr, CaCu
20B phase).

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

Example 1 Bismuth, lead, strontium, calcium.

Bismuth trioxide (manufactured by Wako Tsumugi Kogyo Co., Ltd., purity 99.9%) and -lead oxide (yellow, manufactured by Kojundo Kagaku Kenkyusho) were added so that the ratio of copper, magnesium and barium was as shown in Table 1 in atomic ratio. , pure 999.9%).

Strontium carbonate (manufactured by Kojundo Kagaku Kenkyushin, purity 99.
9%), calcium carbonate (high purity chemical research new product, pure 99%)
9.99%), cupric oxide (manufactured by Rare Metallic, purity 9)
9.9%), magnesium oxide (manufactured by Rare Metallic, purity 99.99%), and barium carbonate (Kojundo Kagaku Kenkyusho stage, purity 99.9%) were weighed and used as starting materials.

Next, the above starting materials were filled into a synthetic resin ball mill together with steel balls coated with synthetic resin and methanol, and mixed and pulverized at 50 revolutions per minute for 60 hours.

After drying, the pulverized product was placed on an alumina baking plate and calcined for 12 hours in the air at the temperature shown in Table 1 using an electric furnace, and then roughly pulverized in a mortar and then placed in a synthetic resin ball mill with zirconia balls, The mixture was filled with methanol, pulverized 24 hours a day at 50 revolutions per minute, and then dried to obtain a raw material for an oxide superconductor.

Thereafter, the raw material for the oxide superconductor was press-molded with a mold at a pressure of 49 MPa, and then fired for 90 hours at the firing temperature shown in Table 1 in a low oxygen pressure atmosphere with a volume ratio of Oz:Nz=1:10. An oxide superconductor was obtained.

Next, the obtained oxide superconductor was crushed in a mortar.

As a powder sample.

Measure the inductance change rate using a powder sample,
The superconductor content at 77K was determined. The results are shown in Table 1.

As is clear from Table 1, the oxide superconductor using the composition for oxide superconductor according to the 9th embodiment of the present invention has many high-temperature phases as determined from the inductance change rate and the superconductor content at 77KK. It can be seen that it is easy to generate.

Implementation row 2 The raw materials for oxide superconductors of Fragrance 18 and Fragrance 41 obtained in Example 1 were press-molded in a mold at a pressure of 49 MPa, and then subjected to a low oxygen pressure of Ox:N, -1:10 at a volume ratio of 1. Each oxide superconductor was obtained by firing in an atmosphere for 90 hours at the firing temperature shown in Figure 1.

Next, the obtained oxide superconductor was crushed in a mortar to obtain a powder sample.

The obtained powder sample was subjected to powder X-ray diffraction to determine the high yz
ero phase (B i, S r2 Ca2Cu3 o1o
(0010) plane of the phase) and the middle Tzero phase (Bi, 5rl
The diffraction peak intensity ratio with the (008) plane of CaxCu30s phase was determined. Using this diffraction Be equation, we can examine the formation of superconductor phases affected by the firing process using the powder X-ray diffraction method! This shows I.

FIG. 1 shows the relationship between the diffraction peak intensity ratio and the firing temperature.

Next, regarding the similar powder sample obtained above.

The superconductor content at 77K was determined in the same manner as in Example 1, and the relationship between the firing temperature and the superconductor content at 77K was investigated. The results are shown in FIG.

As is clear from FIGS. 1 and 2, the oxide superconductor of the present invention using the raw material for an oxide superconductor according to the present invention has 7
From the superconductor content at 7K, it can be seen that the firing temperature range in which many high-temperature phases are obtained is wide, and the content of high-temperature phases is high.

(Effects of the Invention) According to the present invention, it is possible to obtain an oxide superconductor that has a wide sintering temperature range in which many high-temperature phases are produced and has a high content of high-temperature phases. A raw material for a phosphoric oxide superconductor can be obtained using a composition for an oxide superconductor that provides a core composition and a core composition.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between diffraction peak intensity ratio and firing temperature, and FIG. 2 is a graph showing the relationship between superconductor content and firing temperature at 77K. Agent Patent Attorney Kuni Wakabayashi"'v:X""4"-,,
j Firing temperature (°C) Fig. 1

Claims (1)

[Claims] 1. Bismuth, lead, strontium, calcium, copper,
The main components are magnesium and barium, with an atomic ratio of bismuth:lead:strontium:calcium:copper:magnesium:barium from 1.2 to 2.2:0.2.
1:1.4~2.2:1.6~2.4:2.8~4:A
:B (however, A≦1, B≦0.6).A composition for an oxide superconductor. 2. After weighing each raw material containing bismuth, lead, strontium, calcium, copper, magnesium, and barium so as to have the composition according to claim 1, and then mixing, calcining,
A method for producing a raw material for an oxide superconductor, which comprises pulverizing. 3. A method for producing an oxide superconductor, which comprises firing the raw material for an oxide superconductor according to claim 2.