JPH01201025A - Oxide superconducting material - Google Patents

Abstract

PURPOSE:To obtain the title material outstanding in temperature difference, stability and economy, predominant in alkaline earth element-Bi-Cu-O, by further incorporating a crystal phase consisting of specified ratio of these elements. CONSTITUTION:The objective material constituted mainly of ABiCuO (A is at least one kind of alkaline earth element), incorporated with such a crystal phase that the atom. ratio A/Bi/Cu is such as to be 1.9-2.5, 1.1-1.7 and 2 for A, Bi and Cu, respectively (approximately 5/3/5). For higher quality of said superconducting material, a mixture of the two kinds of the element A with the respective ion radii of >=1Angstrom and <1Angstrom should be used. Also, great quantities of such rare earth elements and alkaline earth elements as to cause instability in the final superconducting material are not present in unstable forms in said material, thus protecting said material from erosion or the like due to water.

Description

[Detailed description of the invention] Industrial applications The present invention relates to oxide superconducting materials.

Conventional technology In recent years, YBaCuO-based materials have been reported as superconducting materials.
Various experimental studies are being conducted. As a result, it has become known that this material is very unstable and has major drawbacks such as a large difference between the starting temperature and the completion temperature of superconducting state. Furthermore, since it uses large amounts of rare earth elements, it is expensive and susceptible to market fluctuations, making it economically unstable. Improvements in all of these areas are desired.

Furthermore, very recently, new materials based on 5rBiCuO have been reported. However, details regarding these are currently unknown.

Problems to be Solved by the Invention The object of the present invention is to provide a material that does not have the problems of temperature difference, stability, and economy as described in E.

Means for Solving the Problem AB i consists of constituent elements mainly consisting of CuO (A contains at least one or more elements of the alkali royal family), and further has an atomic ratio of A / B i / Cu of 2
When A is 1.9 to 2.5 and Bi is 1.1 to 1.
7 and contains at least a crystalline phase that can be described as approximately 5/315 to 3/2/3. In order to obtain even higher characteristics, elements with an ionic radius of A of 1 angstrom or more and elements with an ionic radius of 1 angstrom or less are mixed.

It does not contain large amounts of rare earth elements or alkaline earth elements, which can cause operational instability, in an unstable form, so it does not suffer from water erosion. In addition, it is presumed that the solid solution range is wide, and this may be because it does not contain many impurity phases, which also seems to be helpful for stability. Furthermore, this seems to help reduce the above-mentioned temperature difference. By first mixing the alkaline earth elements with ionic radii of 1 angstrom or more and those with ion radius of 1 angstrom or less, an appropriate distance between the elements is achieved. It is estimated that excellent characteristics have been obtained.

Furthermore, it is also excellent in economical efficiency as it does not contain any rare earth elements that are expensive and unstable in supply.

EXAMPLE When conducting additional tests on common recent YBaCuO-based materials, we found that even with the optimum composition of 123 (Y/Ba/Cu ratio), the transition temperature is approximately 90.
However, it was shown that the above-mentioned temperature difference was very large, nearly 10 degrees, and it was also shown that if the composition was slightly changed, an impurity phase would be generated and the characteristics would change.

On the other hand, according to studies conducted by the present inventors, the new material has stable and excellent properties as shown below.

A group of MgCa having an ionic radius of 1 angstrom or less, at least one kind from each of the groups Sr and Ba, and B.
i, Cu-containing oxide has the king ratio A/B i/
Weigh the Cu so that it is approximately 5/315.3/2/3 or close to it, then mix it uniformly, calcinate it at 800 to 850 degrees, and then crush it, mold it, and then bake it at 83 degrees Celsius.
It was done from 0 to 870 degrees. The results obtained are shown in Table 1.

As is clear from Table 1, all of the temperature differences mentioned above are small, below 5 degrees (and the transition temperatures are stable at about 100 degrees or above).Furthermore, when elements from the two groups mentioned above are mixed, It has been shown that the transition temperature is 20 to 30 degrees when used alone, but it is more than 100 degrees.Furthermore, it is left in a high temperature and high humidity environment (60 degrees and 60%) for one month. In the moisture resistance test, the so-called YBaCu material turned white and collapsed considerably, whereas the surface of this material only slightly turned white, indicating that it is very stable.

As can be seen from Table 1, basically the composition is 2.3.4.5
It has been shown that the range approximately surrounded by (15) is particularly excellent.

In addition, even those in which alkaline earth group elements are replaced, such as Nos. 11, 12, and 13, show good characteristics.

Furthermore, the results of X-ray analysis show that crystal phases with a single composition ratio of 3/2/3 or 5/315 exist over a fairly wide range (currently under investigation, but the lattice constant is a = 5.4 angostroms, b=27.0 Ongostrom, c=15.3
It is superficially described as an angostromal orthorhombic crystal, and when combined with the results of transmission electron microscopy, it is estimated to consist of a pseudo-tetragonal superlattice with a unit cell of 5.4 angostroms. ), and it was confirmed that it is very easy to intersect between walls on the 0 side.

Effects of the Invention According to the present invention, it is possible to provide a material that has excellent moisture resistance and a wide solid solution range (the above-mentioned temperature difference is small) and has excellent stability and reproducibility, and is widely applicable to superconducting devices. can be done.

Claims (3)

[Claims] (1) Consists of constituent elements mainly consisting of ABiCuO (A contains at least one type of element of the alkaline earth group), and furthermore, the atomic ratio of A/Bi/Cu is 1. 9 to 2.5, Bi in the range of 1.1 to 1.7, and containing at least a crystal phase that can be described as approximately 5/3/5. (2) Consists of constituent elements mainly consisting of ABiCuO (A contains at least one type of element of the alkaline earth group), and furthermore, the atomic ratio of A/Bi/Cu is 1. 9 to 2.5, Bi in the range of 1.1 to 1.7, and containing at least a crystal phase that can be described as approximately 3/2/3. (3) The oxide superconducting material according to claim 1 or 2, characterized in that A contains elements with an ionic radius of 1 angstrom or more and elements with an ionic radius of 1 angstrom or less.