JPH01131025A - Production of oxide based superconducting material - Google Patents

Abstract

PURPOSE:To obtain a superconducting material capable of readily providing a sheet having a wide area and carrying out machining and forming, by mixing specific metallic alkoxides in a solvent, hydrolyzing the alkoxides, impregnating ceramic paper with the hydrolyzates and calcining the impregnated paper. CONSTITUTION:Alkoxides or acetylacetonates of at least the total three metals of one or more elements of Mg, Ca and Ba of group IIa elements of the periodic table, one or more elements selected from Sc, Y and lanthanoids of group IIIa elements and copper are homogeneously mixed in a solvent and then hydrolyzed. A sheet of ceramic paper is then impregnated with resultant mixture of hydrolyzates, formed and then calcined. Alternatively, a sheet of formed ceramic paper is impregnated with the above-mentioned mixture of the hydrolyzates and calcined. The applied ceramic paper preferably consists essentially of at least one of alumina fiber, alumina silicate fiber, mullite fiber, spinel fiber, beryllia fiber, boron fiber, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a metal oxide (ceramic)-based high-density superconducting material.

[Conventional technology]

Conventionally, metal-based materials have been most commonly known as superconducting materials, and among these, Nb3Ge has the highest superconducting transition temperature (critical temperature) of 23.2. On the other hand, metal oxide-based superconducting materials generally have a lower critical temperature than metal-based materials, about 13 degrees.

On the other hand, recently La-3r-Cu-
0 series (approximately 40K) and Y-Ba-Cu-0 series (approximately 90K)
K) oxide-based superconducting material was discovered. As methods for manufacturing these oxide-based superconducting materials, the so-called dry (powder) method and coprecipitation method are generally widely used.

The dry method is a method in which powdered reagents of oxides and carbonates such as La, Y, Ba, and 5rSCu are mechanically mixed using a mortar or mill, and then fired to obtain a sintered body of the oxide. The coprecipitation method is a method in which the nitrates of the metals mentioned above are uniformly mixed and dissolved in an aqueous solution, and then oxalic acid or ammonia is added to obtain a mixed precipitate of each metal at the same time.

However, these methods cannot produce film-like high-temperature superconductors. Therefore, in order to obtain an oxide-based superconducting film, attempts have been made to use conventional thin film forming methods such as sputtering, vapor deposition, and CVD.

Among these is the Japanese Journal of Applied Fixtures.
l of Applied Physics) vol.
, 26. No. 4゜PL410 (1987) and the same v.
o1.26. No, 5. As described in PL738 (1987) J, etc., the sputtering method is the most common and widely used. The sputtering method uses targets such as La-3r-Cu-0 and Y-Ba.
-A thin film of these oxides is deposited on a heated substrate by bombarding a fired body of Cu-0 or other oxides with ionized Ar or a mixed gas of Ar and 02, followed by firing to make a superconducting film. That is what it is.

[Problem that the invention seeks to solve]

However, in the conventional sputtering method, vacuum system,
Requires expensive and large-scale equipment including a reactor, high-frequency power supply and its control device, gas flow controller, etc.
It is not suitable for forming a film with a large area, and there are problems in that the composition of the formed film often deviates from the intended one. Further, bulk oxide-based superconducting materials have problems such as being difficult to shape both before and after firing.

The present invention has been made in order to solve the above-mentioned problems, and it is an oxide-based superconductor that can be easily spread through a sheet-like superconducting material with a wide area and that can be easily processed and formed. The purpose is to clarify the manufacturing method of materials.

[Means for solving problems]

The present invention is directed to Hg1Ca, which is one of the elements of Group A of the Periodic Table.

A total of at least 3 of each of one or more elements selected from Sr and Ba, one or more elements selected from Sc of the Ma group elements, Y and lanthanoids, and copper.
Mix metal alkoxides or acetylacetonates homogeneously in a solvent and then hydrolyze them, impregnate ceramic paper with the mixture of the resulting hydrolyzed products, and then mold and bake them, or The present invention relates to a method for producing an oxide-based superconducting material, which comprises impregnating a molded ceramic paper with a mixture and firing the mixture.

[For production]

The alkoxide or acetylacetonate of each element used in the present invention is homogeneously dissolved, dispersed or suspended in a suitable solvent, and the mixture of these hydrolysis products is prepared into a ceramic material! Oxide-based superconducting materials having arbitrary shapes and dimensions can be produced by impregnating a sheet of ceramic paper with a mixture of hydrolysis products and firing it, or by processing and molding a ceramic paper, impregnating it with a mixture of hydrolysis products and firing it. can be obtained.

[Example] Metals used in the present invention (Mg, Ca, Sr, Ba,
There are no particular limitations on the alkoxides of Sc, Y, lanthanoids, and Cu), and they can be homogeneously dissolved in the solvent described below.
Any structure or form can be used as long as it can be dispersed or suspended. That is, the metal alkoxide can be used regardless of the number of carbon atoms in the alkoxy group and even if the alkoxide is derived from a polyhydric alcohol. Preferred specific examples of such alkoxy groups include, for example, methoxy group, ethoxy group,
Examples include, but are not limited to, propoxy group, isopropoxy group, butoxy group, tertiary butoxy group, and secondary butoxy group. Further, there is no particular limitation on the number of alkoxy groups bonded to the metal element, as long as at least one of these groups is bonded.

The metal acetylacetonato used in the present invention is not particularly limited, and the metal has at least one acetylacetonato group.
Any structure or form may be used as long as it is a compound that has two bonds and can be homogeneously dissolved, dispersed, or suspended in the solvent described below.

In the present invention, the predetermined metal alkoxides or metal acetylacetonates are homogeneously mixed in a solvent and then hydrolyzed to obtain a mixture of hydrolysis products.

However, since metal alkoxides and metal acetylacetonates generally have different hydrolysis conditions and rates, they cannot be used simultaneously in the present invention, and it is necessary to use only one of them.

Note that the term "homogeneous" as used herein is a concept that includes not only uniformity such as a solution, but also a state that can be used as a substantially uniform product such as an emulsion or dispersion. .

H (alkoxide or acetylacetonate of one or more elements selected from J, Ca, Sr, and Ba (hereinafter referred to as group a compound), Sr, 'Y, and one or more elements selected from lanthanoids) There is no particular limitation on the mixing ratio of Cu alkoxide or acetylacetonate (hereinafter referred to as lla group compound) and Cu alkoxide or acetylacetonate (hereinafter referred to as Cu-containing compound), and the desired oxide-based superconducting material It may be used in any composition ratio as long as it can be obtained, but
For example, when using y as the ma group element, Ira
Group-based compounds/Y-containing compounds/Cu-containing compounds-2 to 10
/ 1 / It is preferable to mix at a ratio of about 3 to 10 (metal atomic ratio), and when La is used as the a group element, (Ua group compound, La-containing compound)/Cu-containing compound-271 ( It is preferable to mix the metals at the same atomic ratio. Note that there is no particular limitation on the ratio of the IIa group compound to the [a-containing compound.

The solvent used in the present invention can be suitably used for hydrolysis, such as methyl alcohol, ethyl alcohol, isopropyl alcohol, butyl alcohol, benzene, toluene, xylene, tetrahydrofuran, diethyl ether, diphenyl ether, anisole, ethyl acetate, butyl acetate. , methyl ethyl ketone, methyl isobutyl ketone, isoamyl alcohol, diacetone alcohol, etc. are preferably used.

There are no particular limitations on the concentration of metal alkoxide or metal acetylacetonate, the method of adding water, or the conditions for hydrolysis, but the amount of water added during hydrolysis is It is sufficient if the amount is in excess of the stoichiometric amount for hydrolyzing metal acetylacetonate, but it is preferably in large excess, and the temperature is preferably 60° C. or higher. As the water to be added, ion-exchanged water, distilled water, etc. that do not contain metal ions are used.

Depending on the element, the hydrolysis product may be a metal oxide, but in general it is often an amorphous hydrate or hydroxide, which is heated at a relatively low temperature (200 to 500°C) by calcination. Most of them become metal oxides.

The resulting mixture of hydrolysis products is brown or black in color and is in the form of a sol in which the hydrolysis products of each metal alkoxide or metal acetylacetonate are homogeneously dispersed.

Next, the superconducting material is changed by impregnating a ceramic paper with the mixture of the hydrolysis products as described above, then shaping and firing, or by impregnating the shaped ceramic paper with the mixture of the hydrolysis products and firing.

Note that there are no particular limitations on the method of forming the ceramic paper.

The ceramic paper is not particularly limited, but preferably has a thickness of 100 to 500 g/-rd and a basis weight of 50 to 250 g/-rd, and alumina! It is preferable that the main component is at least one of the following: l miscellaneous, alumina silicate m fiber, mullite fiber, spinel fiber, beryllia fiber, boron [t, boron nitride m fiber, silicon nitride fiber, aluminum nitride fiber, etc. The binder preferably includes cellulose fibers, polyvinyl alcohol fibers, polyvinyl butyral i1m, vinylon fibers, polyester fibers, cellulose acetate fibers, and the like. The binder is preferably microfibrillated to a fiber diameter of 1 AIm or less, and is preferably added in an amount of 10% by weight or less based on the above-mentioned main components. Such ceramic paper is manufactured under the paper-making conditions disclosed in detail in JP-A-60-81399 (invention name: inorganic paper) and JP-A-60-81398 (invention name: nialumina vapor). You can wander around.

There are no particular limitations on the method for impregnating the ceramic paper with the mixture of the hydrolyzed products, but examples include a coating method using a brush, a spray method, a dipping method, and a printing method. There is no particular limitation on the amount of the mixture of hydrolysis products to be impregnated, but it is preferable to impregnate the mixture so that the amount of the mixture of hydrolysis products after drying is 10 to 50% by weight based on the total weight.

There are no particular limitations on the firing method or firing conditions; for example, ceramic paper impregnated with a mixture of hydrolyzed products is air-dried or heated and dried in an oven at approximately 800-950°C for approximately 1-10 hours. After pre-firing, it may be baked at about 850 to 1100°C for about 1 to 24 hours. The atmosphere for firing may be either air or oxygen atmosphere, and the firing process can be carried out at any humidity and any number of times. According to studies conducted by the present inventors, it appears that materials with better superconducting properties can generally be produced by carrying out the process in an atmosphere rich in oxygen. This is presumed to be because oxides of each metal element are more likely to be produced when the compounds used are thermally decomposed and then fired in an oxygen-rich atmosphere.

Example 1 The composition of the target oxide-based superconducting material is YBa2Cu3
Acetylacetonate of each of Y 1Ba and Cu (total 10 g) was heated at 80°C in a predetermined ratio so that O7
It was dissolved (partially suspended) in 500 ml of ethyl alcohol. Distilled water 3- to which a small amount (11d) of ammonia water (111 degrees 10%) was added was gradually added to 10% of this solution.
Hydrolysis was carried out by dropwise addition over a period of minutes to obtain a mixture of hydrolysis products in the form of a sol.

After concentrating this sol to 100-mH diameter approximately 3ρ
, a paper with a thickness of 300 ρ, made from short alumina fibers (manufactured by Mitsubishi Chemical Corporation) with a fiber length of 200 to 800 ρ and cellulose microfibrillated to a fiber diameter of about 10 ρ or less (HFC ■ manufactured by Daicel) as an organic binder. Amount: 80g
Alumina paper (containing 5% by weight of cellulose) with a size of 100# Length 100 rin, diameter 10
It was molded into a cylindrical shape and air-dried for 5 hours. Next, after preliminarily firing in air at 500°C for 2 hours, the product was fired at 950°C for 3 hours in an oxygen stream to obtain a fired product.

Four electrodes were formed on this sample at intervals of 1.5 seconds using indium, the sample was placed in a cryostat, and the temperature change in resistivity was measured by a four-terminal method while gradually cooling with liquid helium. The measurement results are shown in Figure 1.

As shown in FIG. 1, the resistivity decreases rapidly at 98.5 and shows zero resistance at 95.5. In addition, the critical current density is 212 at the liquid nitrogen temperature (77.4K).
It showed 7A/c4.

Example 2 The mixture of the sol-like hydrolyzed products obtained in Example 1 was concentrated to 100° and was placed on the same alumina paper as in Example 1 with a size of 30# x 900°. It was impregnated in the same manner and air-dried for 5 hours to obtain a ribbon-shaped alumina-metal oxide gel sheet.

As shown in FIG. 2, this ribbon-like sheet (1) was spirally wound around a cylindrical ceramic (2) having a diameter of 50 mm, and then sintered under the same conditions as in Example 1.

When the cylindrical ceramic was removed, the spiral oxide-based superconducting material could be seen.

When the temperature change in resistivity of the obtained superconducting material and the critical current density at the temperature of liquid nitrogen were measured, it was found that the superconducting material had good superconducting properties comparable to those of Example 1.

Example 3 The mixture of sol-like hydrolysis products obtained in Example 1 was concentrated to 100%, and the weight after drying was 3% of the total weight.
0% on one side of the same alumina paper as in Example 1 with a size of 50 # x 900 m, repeat coating and drying 10 times, and dry naturally for 5 hours to form alumina-metal. I got an oxide gel sheet.

After this sheet was rolled as shown in FIG. 3, it was fired under the same conditions as in Example 1. This results in a superconducting layer (3
) and an alumina layer, that is, an insulating layer (4), were formed in a coiled form.

When the temperature change in resistivity of the obtained superconducting material and the critical current density at the temperature of liquid nitrogen were measured, it was found that the superconducting material had good superconducting properties comparable to those of Example 1.

Example 4 The composition of the oxide-based superconducting material that is the final sintered body is YB.
a2C11307, barium butoxide,
Yttrium butoxide and copper butoxide (3 g in total) were uniformly dissolved in 11 parts of n-butyl alcohol. This solution was allowed to stand at room temperature for 10 days and was gradually hydrolyzed with water vapor in the air to obtain a sol of a mixture of hydrolysis products.

After concentrating this sol to 100 d, it was impregnated into the same alumina paper as in Example 1 by the depping method, and molded under the same conditions as in Example 1.
After firing, a cylindrical oxide-based superconducting material was obtained.

When the temperature change in resistivity of the obtained superconducting material and the critical current density at the temperature of liquid nitrogen were measured, it was found that the superconducting material had good superconducting properties comparable to those of Example 1.

〔Effect of the invention〕

As described above, according to the present invention, a total of at least three elements selected from Mg, Ca, sr, and Ba, one or more elements selected from Sc, Y, and lanthanoids, and copper, respectively. Metal alkoxides or acetylacetonates are homogeneously mixed in a solvent and then hydrolyzed, the resulting mixture of hydrolyzed products is impregnated into ceramic paper, formed, dried and fired, or the mixture of hydrolyzed products is By impregnating shaped ceramic paper, drying, and firing, it is possible to obtain an oxide-based superconducting material with arbitrary shape and dimensions, high critical temperature, narrow transition width, and large critical current density. This effect is achieved.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the temperature dependence of resistivity of the oxide superconducting material obtained in Example 1 of the present invention, Fig. 2 is an explanatory diagram of the molding process of Example 2 of the present invention, and Fig. 3 FIG. 3 is an explanatory diagram of the molding process of Example 3 of the present invention. Agent Masuo Oiwa 1st
Mouth temperature (K)

Claims (4)

[Claims] (1) Mg, Ca, and Sr of group IIa elements of the periodic table
and Ba, one or more elements selected from Group IIIa elements Sc, Y, and lanthanoids, and copper. The mixture of hydrolysis products is homogeneously mixed and then hydrolyzed in a ceramic paper, and the resulting mixture of hydrolysis products is impregnated into a ceramic paper, which is then shaped and fired, or the mixture of hydrolysis products is impregnated into a shaped ceramic paper. A method for producing an oxide-based superconducting material, which comprises firing. (2) The main components of ceramic paper are alumina fiber, alumina silicate fiber, mullite fiber, spinel fiber,
The method for producing an oxide-based superconducting material according to claim 1, which is at least one of beryllia fiber, boron fiber, boron nitride fiber, silicon nitride fiber, and aluminum nitride fiber. (3) Claims (1) or (2), wherein the ceramic paper contains microfibrillated fibers with a fiber diameter of 1 μm or less as a binder in an amount of 10% by weight or less based on the main component ceramic. A method for manufacturing the oxide-based superconducting material described above. (4) The binder is cellulose fiber, polyvinyl alcohol fiber, polyvinyl butyral fiber, vinylon fiber,
The method for producing an oxide-based superconducting material according to claim (3), which is at least one of polyester fibers and cellulose acetate fibers.