JP2587651B2 - Production method of superconducting material - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for producing a superconducting material, and more particularly to an improvement on a conventional method for producing a superconducting material.

[Conventional technology and its problems]

As is well known, new research on superconducting materials is currently being actively conducted, and Y-Ba-Cu-O-based and La-
Substances such as Sr—Cu—O and La—Ba—Cu—O are already known. In particular, research is progressing on Y-Ba-Cu-O-based superconducting materials, and research for practical use is being actively conducted.

The conventional ordinary method for producing these superconducting materials is described as Y-Ba-Cu-
FIG. 2 shows an O system as a representative example.
That is, first the raw material powder, usually yttrium oxide, copper oxide,
And a predetermined amount of each powder of barium carbonate. In mixing, an alcohol such as ethanol is added and wet-mixed in order to prevent coexistence of water as much as possible. After drying, the mixture is mixed again if necessary, dried, and then subjected to pressure molding to form granules or pellets. Next, this is calcined at about 900 ° C., cooled and then pulverized, and the pulverized material is wet-mixed. Then, after drying, it is pressed and sintered.

[Problems to be solved by the invention]

The present inventors have been enthusiastically studying the method for producing this kind of superconducting material, but in this study, when producing this kind of superconducting material, particularly when the adsorbed moisture of the calcined body or its pulverized material is reduced. It has been found that the properties of the obtained superconducting material vary greatly depending on the amount. As we continue our research,
It has been found that the lower the adsorbed water content of the calcined body or its pulverized material, the higher the superconducting transition temperature of the obtained superconducting substance. More specifically, as shown in FIG. 3, the actual resistance of the obtained superconducting material decreases as shown by the solid line, and the temperature at which the resistance becomes 0 becomes a gentle curve as shown by arrow A. . The longer the length of the curve, the lower the temperature at which the resistance becomes zero, which is undesirable. Therefore, it is preferable that the length of the curve be as short as possible. Hereinafter, this curved portion is defined as “tail pull”. In other words, it was found that the more the adsorbed moisture of the calcined body or its pulverized material, the longer the "tail pull". The problem to be solved by the present invention is therefore to avoid this "tailing" phenomenon or to make it as short as possible.

[Means for solving the problem]

This problem can be solved by treating the ground material of the calcined body with a liquid medium capable of removing water by azeotropic distillation at a low temperature, followed by drying and subsequent treatment according to a known method.

That is, the present invention relates to a method for producing a superconducting material by mixing a predetermined raw material powder, calcining, then pulverizing the calcined body, molding and sintering the obtained molded body to produce a superconducting material. The method according to claim 1, wherein the pulverized material is treated with a liquid medium capable of removing water by azeotropic distillation with water at a low temperature and then dried.

[Function and Configuration of the Invention]

In the present invention, it is possible to remove the water adsorbed in the pulverized material of the calcined body by treating the pulverized material of the calcined body with the above-described liquid medium, and hence, the superconductor of the target object The "tailing" phenomenon of the material can be prevented or significantly reduced.

 The method of the present invention will be described below in the order of steps.

First, a raw material powder is prepared. As a raw material, a raw material is appropriately selected according to a kind of a desired superconducting substance. For example, in the case of Y-Ba-Cu-O system, yttrium oxide, barium carbonate and copper oxide are used, and in the case of La-Sr-Cu-O system, lanthanum oxide, strontium carbonate and copper oxide are used. I do. In the case of La-Ba-Cu-O system, lanthanum oxide, barium carbonate, and copper oxide are used. These raw material powders are mixed in a desired composition ratio, for example, Y-Ba-
In the case of Cu-O system, these raw materials are previously blended so that the composition of the obtained target superconducting substance is as shown in FIG.

This raw material powder is then mixed, and the mixing at this time is usually performed by a wet method, and is performed by adding a liquid other than water, for example, an alcohol such as ethanol. The reason is based on the fact that coexistence of water is undesirable. The wet mixture may be naturally dried, or may be heated at a temperature of about 150 ° C. or lower. If necessary, the above liquid medium is added to the dried product, and wet mixing is repeated again. By repeating the process, the particle size of the raw material powder is adjusted, and there is an effect that the optimum filling particle size at the time of molding is easily obtained.

Next, the raw material powder is subjected to pressure molding, and if necessary, after drying, the molded body is calcined. At the time of pressure molding, it is desirable to remove alcohol and the like in the raw material powder, and therefore, drying is usually performed. The pressure molding is usually performed into pellets, but the shape is not limited to the pellets, and may be any shape as long as it is easily calcined. The molded body obtained here is then calcined. This calcination is performed for the purpose of reacting the raw material powder and obtaining a substance capable of exhibiting a superconducting phase, and the temperature is appropriately determined according to the type and the mixing ratio of the raw material powder used,
For example, in the case of Y-Ba-Cu-O system, usually 800 ° C. or higher,
Preferably it is 850 to 950 ° C, especially around 900 ° C.
The calcination time is usually 6 to 48 hours, preferably about 12 to 24 hours, depending on the temperature.

The calcined body is usually wet ground. The liquid medium used at this time is a normal alcohol-based medium other than water, for example, ethanol, and is used in a state in which moisture is not adsorbed as much as possible during pulverization.

The major feature of the present invention is that the ground material of the calcined body is treated with a liquid medium capable of removing water by azeotropic distillation with water at a low temperature. As the liquid medium used at this time, typically, alcohols such as methyl alcohol, ethyl alcohol, and butyl alcohol can be exemplified, and chloroform, methyl acetate, and the like can be exemplified. Note that the low temperature generally means a temperature of 98 ° C. or less, preferably 90 ° C. or less, and particularly about 50 ° C. or less.

As the treatment using the liquid medium, a means for immersing the pulverized material in the liquid medium is typical and most preferable, but other means such as spraying may be applied. The reason why the immersion means is preferable is that the crushed material may be immersed as it is during the next molding and sintering,
This is based on the fact that even if the period during this period is prolonged, re-water absorption of the pulverized material can be effectively prevented.

After drying, sintering is performed. For sintering, an appropriate mold is filled with the pulverized material, and the pulverized material is sintered while applying pressure as necessary.
At this time, unlike calcination, sintering is required, and the crushing is performed at a temperature at which the sinter is sufficiently sintered.

〔Example〕

 Hereinafter, the method of the present invention will be described in detail with reference to examples.

Example 1 Production of Y ₁ Ba ₂ Cu ₃ O _X (where _X is 6 to 7): purity 99.9
Weight percent or more of Y ₂ O ₃ , BaCO ₃ , and CUO are mixed at 1: 3.5: 2.1 (weight ratio) in a mortar in the presence of ethanol in a mortar, and the powder is filled in a natural drying mold, and the pressure is 100 kg / cm. Form into pellets of about 10φ × 5mm using a hand press in ² , then 900
The mixture was calcined in the air at 24 ° C. for 24 hours and cooled in a furnace. The obtained calcined body was pulverized in ethanol and subsequently stored in ethanol for one month. Immediately afterwards, use an iron mold and
It was formed into a pellet (same size as above) at a pressure of 0 kg / cm ² and sintered at 950 ° C. for 24 hours in the atmosphere. As a result, the temperature at which the resistance began to drop rapidly was 90K, and the temperature at which the resistance was completely zero was 88K, and there was almost no "tail pull" phenomenon.

Example _{2 Y 0.3 Ba 0.7 Cu 1 O} y (y is 2-2.5) Preparation of a blending ratio of the raw material In the embodiment _{1 Y 2 O 3: BaCO 3} : CuO =
1: 4.1: 2.3, and the temperature at the time of sintering was 900 ° C., and the others were treated in the same manner as in Example 1. The measurement results showed that the temperature at which the resistance began to drop rapidly was 89 K, and the resistance was completely zero. The temperature was 87K, and there was almost no "tail pull" phenomenon.

Comparative Examples 1 and 2 In Examples 1 and 2, the calcined body was pulverized and then stored in the air for one month, and the others were treated in the same manner as in Examples 1 and 2.

The results of these measurements showed that the temperature at which the resistance began to drop rapidly was 86K and 86K, respectively, and the temperature at which the resistance was completely zero was 77K and 78K, and the "tail pulling" phenomenon was remarkable.

[Brief description of the drawings]

FIG. 1 is a ternary composition diagram of Y, Ba and Cu, FIG. 2 is a flow sheet showing an example of a conventional method for producing a superconducting material, and FIG. 3 is a relationship between resistance and temperature of the superconducting material. FIG.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Masayoshi Yoshikawa 8 Nishinocho, Higashimukaijima, Amagasaki City, Hyogo Prefecture Inside Mitsubishi Cable Industries, Ltd. (56) References JP-A-63-239153 (JP, A) JP-A-63 −307155 (JP, A)

Claims (6)

(57) [Claims] 1. A method for producing a superconducting material, comprising mixing a predetermined raw material powder, calcining, and then pulverizing the calcined body to form a molded body, and sintering the obtained molded body. A method for producing a superconducting material, comprising: treating a pulverized product of a fired body with a liquid medium capable of removing water by azeotropic distillation with water at a low temperature, and then drying the resultant. 2. The method according to claim 1, wherein said predetermined raw material powder is mixed by wet mixing and then dried. 3. The method according to claim 1, wherein said liquid medium is an alcohol type liquid medium. 4. The method according to claim 1, wherein the predetermined raw material powder is a mixed powder of yttrium oxide, copper oxide, and barium carbonate. 5. The method according to claim 1, wherein the predetermined raw material powder is a mixed powder of lanthanum oxide, strontium carbonate or barium carbonate, and copper oxide. . 6. A patent characterized in that the raw material powders are blended so that the composition of yttrium, barium and copper of the obtained superconducting substance falls within the range shown by hatching in the ternary composition diagram shown in FIG. Claim (1) or (4)
Production method described in the section.