JPS63274654A - Production of superconductive material - Google Patents

Abstract

PURPOSE:To prepare effectively a superconductive material having oxygen vacancy in perovskite crystal structure in a short time by grinding down a powder mixture consisting of an inorg. salt of Ba, CuO, and an inorg. salt or a rare earth element admixed with an org. solvent, calcining the ground product under specified conditions, then carrying out final calcination and oxygen treatment. CONSTITUTION:Each specified amt. of an inorg. salt of Ba, CuO, and an inorg. salt of a rare earth element is weighed and mixed. The mixture is ground down after adding an org. solvent and the ground product is calcined at >=800 deg.C. After crushing again, the product is compression-molded. The compression- molded product is calcined finally at >= the first calcination temp., it is then treated at >= the final calcination temp. for 1-8hr in O2 atmosphere. By this process, a superconductive material consisting of a compsn. expressed by the formula (wherein M is Y, Sc, La, Lu, Yb, Tm, Er, Ho, Dy, Gd, Pr, Nd, Eu, Tb, or Sm; x is 1-3; y is 0.01-1.5; z is 0-3) and having oxygen vacancy in perovskite type crystal structure is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for manufacturing a superconducting material, and particularly to a method for manufacturing a superconducting material having an oxygen-deficient perovskite crystal structure.

(Prior art) Superconductors known so far require cooling with low-temperature liquid helium (boiling point 4.2K), which increases cooling costs and ultimately creates a superconducting state. The disadvantage was that the scale of the system was also smaller. Furthermore, the uneven distribution of helium as a resource has hindered the widespread use of superconductors.

However, superconductors whose critical temperature Tc (transition initiation temperature) exceeds the liquid nitrogen temperature (boiling point 77 K) have recently been reported.
Chu et al.'s group reported that barium with a critical temperature of 94
reported the discovery of yttrium-copper-oxygen oxides (Phys, Rev, Letter,
vol, 5B, P90B-909, 1987).

Furthermore, Kitazawa et al.'s group at the University of Tokyo has found that the critical temperature is 95% for barium-ytterbium-copper-oxygen oxides.
The group of Takagi et al., also at the University of Tokyo, reported a critical temperature of 95 for barium-erbium-copper-oxygen oxides (in both cases,
Jap, Journal of Appl, Phys
,, vol. 26. April issue, 1987).

Furthermore, the second component of the above three types of oxides is scandium, ruthenium, thulium, holmium, dysprosium,
Even in the case of oxides substituted with gadolinium or the like, a critical temperature of about 90°C has been reported.

These various superconductors all have the general formula;% formula% However, in the formula, M is YSSc, La, Lu, Yb.

is a rare earth element of at least Ift selected from the group of Tm, Er, Ho, Dy5Gd and Sm, and X is 1 to
3, y is 0.01 to 1.5, and z is θ to 3.

In this case, although the reason is not clear, the deficient Ti oxygen is extremely important, and the manner of its vacancies and the vacancy density are determined by the critical temperature (Tc) of the superconducting material and the transition width temperature ΔTc (the electrical resistivity is near Tc). It is estimated that it directly affects the temperature interval at which the rate of change is 90% and 10% when changing from normal value to zero resistance, and it is important to treat the superconducting material after firing with oxygen at high temperature. gender has come to be recognized.

(Problems to be Solved by the Invention) However, since calcination usually involves preliminary calcination and main calcination, further oxygen treatment requires time and effort in sample preparation, so it is not possible to shorten this manufacturing process time. It was wanted.

Therefore, a first object of the present invention is to provide a method for manufacturing a superconducting material having an rII element-deficient perovskite crystal structure, which reduces the manufacturing process time.

A second object of the present invention is to provide a method for controlling the degree of @ element defects in an oxygen-deficient perovskite superconducting material.

(Means for Solving the Problems) The above aspects of the present invention have the general formula BaxMyCu3O9
- A method for producing a superconducting material having an oxygen-deficient perovskite crystal structure consisting of a composition of After that, heat it to 800℃
The above is pre-calcined, crushed again, compression molded, main-fired at a temperature not lower than the main-calcination temperature, and then treated in an oxygen atmosphere for 1 to 8 hours at a temperature not lower than the main-calcination temperature. This was achieved by a method for producing superconducting materials characterized by:

In the above general formula, M is Y, Sc, La5Lu 1Y
b ,, T m SE r s Ho s D y
1G d SP r 1M of a rare earth element selected from the group of 1Nd, Eu%Tb and Sm;
is 1-3, y is 0.01-[5,2 is 0-3.

When manufacturing a superconductor with such a composition, it is preferable to use the highest possible purity of barium inorganic salt and copper oxide, as they can be obtained relatively easily. Regarding rare earth elements, it is extremely complicated to obtain pure products for each element, and there are no particular adverse effects from using mixtures of rare earth elements, so mixtures of rare earth elements are used as raw materials. It is preferable.

A mixture of these raw materials can be prepared by a known powder method or coprecipitation method.

The obtained mixture is usually pre-calcined before the main firing. In the present invention, the pre-calcination is carried out at approximately 800°C-90°C.
It is preferable to carry out the firing at 0°C for 3 to 10 hours.Then, the mixture after preliminary firing is crushed again and compression molded, and the main firing is carried out at 100°C.
3-12 at a temperature below 0℃ and not lower than the pre-calcination.
Compression molding, which is carried out for a long time, can be carried out to the extent that the superconductor can maintain its shape, but usually a pressure of about 1000 kg/cm2 is applied. The molded body is further subjected to oxygen treatment in an oxygen atmosphere at a temperature o-too °C higher than the main firing for 1-8 hours, preferably 2-6 hours, and then the temperature is gradually lowered to return to room temperature. .

In this case, the time for the r11 discard treatment is shorter as the treatment temperature is higher, and longer as the treatment temperature is lower, but in any case, the treatment time is in the range of 1 to 8 hours.

It is difficult to understand that the M elementary treatment time should not be too long, assuming that oxygen treatment diffuses oxygen into the crystal at the same time as crystal annealing and adjusts the amount of deficient oxygen, but conventional , from the meaning of annealing, rI! It is also possible to assume that because the elementary treatment was performed at a lower temperature than the main firing temperature, oxygen was supplied again more than necessary due to the sufficiently long oxygen treatment.

Since the conventional oxygen treatment time was usually 10 hours or more, the present invention can save at least 2 to 3 hours of time spent on the manufacturing process.

(Effects of the Invention) As described in detail above, according to the present invention, at least the time for Mi treatment can be reduced compared to the conventional method, and the time spent on the manufacturing process can be reduced accordingly. Since the oxygen treatment temperature is higher than both the preliminary firing and final firing temperatures, it is also possible to shorten the preliminary firing and final firing times, and therefore the overall manufacturing time can be significantly shortened. Not only that, but the performance of the resulting superconductor can also be improved.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

Example.

Ba2Ln (md) as a composite metal oxide superconductor
Cu309>' was exploded as follows.

However, here, Ln (md) means a medium rare earth element mixture having the following composition.

Y: 10.3 atomic% Pr: 1.8 Nd: 11.3 Sm: 33.4 Eu: 4.0 Gd: 23.1 Tb: 1.7 Others: 13.8 0.015 mol of target product obtained Baco3
(99,9%) , Y2 (CO3) 3 (99
゜9%), CuO (99,99%), Ln (md
) The carbonate was weighed.

Ethanol was added to the mixed powder, wet-mixed in a mortar, placed in a crucible, and calcined at 900°C for 5 hours.
Grind again and press at a pressure of about 1000 kg/cm2 to make 2 pellets, and each pellet is further heated to 900°C.
The final firing was carried out for 3 hours.

Next, one of the resulting pellets was treated with oxygen at 950° C. for 1 to 2 hours, and the other was treated with oxygen for 5 hours, and the critical temperature of each pellet was measured.

The results obtained are shown in Table 1.

Table 1 Sample Oxygen Treatment Tc As is clear from the results in Table 1 (it was demonstrated that Tc was improved by oxygen treatment at a higher temperature than the pre-firing and main firing temperatures and for a shorter time than before). .

Claims (1)

[Claims] 1) In a method for producing a superconducting material having a composition of the general formula BaxMyCu_3O_9^-z and having an oxygen-deficient perovskite crystal structure, an organic solvent is added to a mixed powder of an inorganic salt of barium, copper oxide, and an inorganic salt of a rare earth element. After adding and grinding, this is calcined at 800℃ or higher,
A superconductor characterized in that it is crushed again, compression molded, main fired at a temperature not lower than the pre-calcination temperature, and then treated in an oxygen atmosphere at a temperature not lower than the main firing temperature for 1 to 8 hours. method for producing a magnetic material (in the formula, M is Y, Sc, L
a, Lu, Yb, Tm, Er, Ho, Dy, Gd, Pr
, Nd, Eu, Tb, and Sm, x is 1 to 3, and y is 0.0.
1-1.5, z is 0-3).