JPH0230615A - Production of oxide superconductor - Google Patents

Abstract

PURPOSE:To obtain a superconductor with high homogeneity densely containing a desired crystalline phase by using a powdery raw material prepared by hydrolyzing a mixture solution of copper and rare earth element alkoxides with a barium nitrate and/or nitrite aqueous solution in production of a Ba-rare earth element-Cu-based oxide superconductor. CONSTITUTION:In production of a Ba-rare earth element-Cu-based superconductor, a powdery raw material prepared by hydrolyzing a mixture solution of copper and rare earth element alkoxides with a Ba(NaO3) aqueous solution and/or a Ba(NO2)2 aqueous solution is used. As the above-mentioned alkoxides, 1-6C alkoxides or ones of alcohols represented by general chemical formula: HO(CH2CH2O)nR (N is 1-6 integer; R is hydrogen atom, 1-15C alkyl group or aromatic group) are preferable. As the solvent for preparation of the alkoxide solution, e.g. i-propanol, n-butanol, benzene or toluene can be preferably utilized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing a Ba-rare earth element-Cu-0 based oxide superconductor.

(Prior Art) It has been known to obtain oxide-based ceramics by using a metal alkoxide as a raw material, hydrolyzing it to obtain a homogeneous powder, and firing the powder. The oxide obtained by this method has the advantages of being highly pure and highly homogeneous, capable of being sintered at low temperatures, and easily molded into fibers, films, etc. Many manufacturing methods using this method have also been proposed for oxide superconductors.

(Problem to be Solved by the Invention) However, according to this method, when producing a superconductor containing barium, Ba (Oll) 2 produced by hydrolysis of barium alkoxide is converted into the popular CO When doing so, BaC0a is easily generated by reacting with CO□ generated from the remaining organic matter. Since this BaC0* has low reactivity and does not decompose unless heated to a temperature above aOO°C, the desired superconductor crystal cannot be obtained unless the resulting powder is fired at a high temperature of 800°C or higher. For this reason, grain growth tends to occur during firing, resulting in problems such as failure to improve critical current density when formed into a sintered body. Furthermore, even if a homogeneous raw material powder is obtained, segregation of Ba occurs due to the formation of BaC, so there is also the problem that compositional homogeneity is impaired.

(Means for Solving the Problems) The present invention was made to solve the above-mentioned problems, and in a method for producing a Ba-rare earth element-Cu-0 based oxide superconductor, rare earth elements and Mixed alkoxide solution of Cu is mixed with BafNO*)z aqueous solution and/or Ba
The present invention provides a method for producing an oxide superconductor characterized by using a raw material powder prepared by hydrolysis with an aqueous fNO2)2 solution.

Hereinafter, the manufacturing method of the present invention will be explained step by step. First, a mixed alkoxide solution is prepared in which copper alkoxide and rare earth element alkoxide (hereinafter explained using yttrium as an example) are uniformly dissolved in a solvent in the same composition ratio as the desired oxide superconductor.

The copper alkoxide and yttrium alkoxide are preferably soluble in a solvent, and include methoxide, ethoxide, n-propoxide, i-propoxide, n-butoxide, i-butoxide, 5ec-butoxide, Ler
t-butoxide, n-bentoxide, 5ee-bentoxide, 1-bentoxide, ter L-bentoxide,
Alkoxides having 1 to 6 carbon atoms, such as alkoxides of alcohols represented by the general formula 1 group (CII, C1□0)nR, are preferable. Here, n is an integer from 1 to 6 and R
is a hydrogen atom, an alkyl group having 1 to 15 carbon atoms, or an aromatic group. Particularly preferred are 1-propoxide, methoxide, ethoxide, n-propoxide, 5
ec-butoxide, l-butoxide, LerL-butoxide, n-butoxide, 2-ethoxyethoxide, 2-
Butoxyethoxide, 2-i-propoxyethoxide,
2-butoxyethoxide, 2-i-butoxyethoxide, 2-5ec-butoxyethoxide, 2-LerL-
They are butoxyethoxide, 2-(2-methoxyethoxy)ethoxide, and 2-(2-ethoxyethoxy)ethoxide.

The solvent is not particularly limited as long as it sufficiently dissolves the metal alkoxide and does not react with the metal alkoxide to liberate metal components in the form of ions or the like. Preferred solvents include methanol, ethanol, i-propanol, n-propanol, n-butanol, i-butanol, 5ec-butanol, LerL-butanol, 2-methoxyethanol, 2-ethoxyethanol,
2-propoxyethanol °, 2-1-propoxyethanol, 2-butoxyshetanol, 2-1-butoxyshetanol, 2-5ec-butoxyshetanol, 2-t
Alcohols such as art-butoxycetanol, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)ethanol, aromatic hydrocarbons such as benzene, toluene, xylene, tetrahydrofuran, dioxane, methyl ether, ethyl Ethers such as ether, propyl ether, butyl ether, diglyme,
Aliphatic hydrocarbons such as n-hexane, n-hebutane, and n-octane; amides such as dimethylformamide, dimethylacetamide, and N-methylpyrrolidone; and amines such as ethanolamine, jetanolamine, and triethanolamine. Can be mentioned. Particularly preferred are i-propertool, n-butanol, 5ec-butanol, 2
-methoxyethanol, 2-ethoxyethanol, 2-
i-propoxyethanol, benzene, toluene, xylene, tetrahydrofuran, dioxane, ethanolamine, jetanolamine, and triethanolamine.

Next, add Ba (NOpl) to the mixed alkoxide solution described in -.
- and/or an aqueous solution containing Ba (No2)2 is added to hydrolyze the alkoxide. The aqueous solution is added such that the amount of barium relative to copper and yttrium in the alkoxide solution is the same as the composition of the desired oxide superconductor. As a result of hydrolysis, oxides, hydroxides or hydrates of copper and yttrium are obtained. Regarding barium, Ba (NO,) 2 and/or Ba (NO2) 2 are uniformly dispersed or partially dissolved in the hydrolysis product. By distilling off the solvent under normal pressure or reduced pressure, an amorphous raw material powder in which copper, yttrium, and barium components are uniformly dispersed at a very fine level can be obtained.

Since barium exists in the form of nitrate or nitrite in this raw material powder, BaCO5 is not produced by reacting with CO2 in the air or CD□ generated during firing. Therefore, by heating and firing at 500 to 1000°C, a homogeneous oxide superconductor can be obtained at a relatively low temperature and in a short time. Firing should be done in an oxidizing atmosphere (
For example, it is preferable to carry out in an oxygen and/or ozone atmosphere).

After firing, the obtained oxide superconductor can be shaped using a dry press or the like, and then heated and sintered. In this case as well, since the fired product is homogeneous and fine, it can be easily sintered at a relatively low temperature.

In addition, BaSO4, BaBrz, Ba
It is possible to suppress the formation of BaC01 by using C12nalz and BaFz, but in this case, S, Or, C1,1, and F remain, respectively, even after heating and firing, so this is inappropriate. BaClO4 and the like are also unsuitable for the same reason. Naturally, Ba(Oil)i cannot be used either.

The above explanation has been given using yttrium as an example of a rare earth element, but other elements include Yb, llo, Er, Sc, 1
．． a.

Nd, Pm, Sm, Eu, Gd, Tb, D
It is preferable to use y, Tm, and Lu alone or in combination, since an oxide superconductor with good characteristics can be obtained.

A particularly preferred composition of the oxide superconductor is BaxY
+-1lcuds-y (0< x < I, ≦y
≦1.5).

(Example) Copper alkoxide and yttrium alkoxide shown in Table 1 were each dissolved in a solvent to obtain a solution having the concentration shown in Table 1. These were mixed under a nitrogen atmosphere so that the molar ratio of Cu:Y was 3:1 to prepare a mixed alkoxide solution.

This was stirred at 60°C for 1 hour, then at 80°C for 2 hours, cooled to room temperature, and stirred with Ba (NOs) 2 aqueous solution (8% by weight) or Ba (NOal z aqueous solution (35%)).
% by weight) was added dropwise so that the molar ratio of Ba:Y was 2:1, and stirring was continued for 1 hour. This was further heated to 60℃ for 1 hour.
Subsequently, after stirring at 80'C for 2 hours, the solvent was distilled off under reduced pressure to obtain a raw material powder.

A part of this raw material powder was collected and thermogravimetrically analyzed (30 to 1
000℃, temperature increase rate IO℃/min, oxygen atmosphere), no large decrease in 81 was observed above 800℃ for any of the powders, confirming that BaC0:+ was not generated during firing. It was done.

Next, the raw material powder was dried at 120° C. for 1 hour, and then fired at 800° C. for 10 hours in an oxygen atmosphere. The obtained powder is
According to X-ray diffraction, most of them are BazYCu30t-δ
It was confirmed that it consisted of crystals (0<δ<0.5).

This powder was further applied at a pressure of 400 kg/cm for 10
After dry press molding into a disc shape of mmφ x 2mm,
The critical temperature (Tc) of the obtained sintered body was measured after firing at 0° C. for 10 hours. The results are summarized in Table 1.

(Comparative example) Toluene solution of copper 2-ethoxyethoxide (0.12M
), toluene solution of yttrium n-butoxide (0
, 35M) 2- of barium 2-ethoxyethoxide
CIJ ethoxyethanol solution (0.4M): Y
:Ba=3 :I : They were mixed in a nitrogen atmosphere so as to have a molar ratio of 2 to prepare a mixed alkoxide solution.

After stirring this at 60° C. for 1 hour and at 80° C. for 2 hours, water was added dropwise for hydrolysis. This was further heated to 60℃ for 1 hour.
After stirring at 80°C for 2 hours, the solvent was distilled off under reduced pressure to obtain a powder.

When this powder was subjected to the same thermogravimetric analysis as in the example, a large decrease in 1n content of about 10% was observed from 800°C to 950°C. This weight loss is presumed to be due to the decomposition of the BacL produced in part.

Next, this powder was dried at 120° C. for 1 hour, and then fired at 800° C. for 10 hours in an oxygen atmosphere.

The obtained powder was found to be BaaYCu307-δ as a result of X-ray diffraction.
(0≦δ≦0.5) There are almost no crystals, and instead Ba
CO5 crystals were confirmed.

(Effects of the Invention) According to the production method of the present invention, the oxide superconductor is obtained through a solution containing the necessary metal components, so it has extremely high homogeneity, and the oxide superconductor contains the desired crystalline phase at high density. A physical superconductor is obtained. The raw material powder of the present invention is homogeneous and highly active, and since BaC01 is not generated during sintering, a crystalline phase exhibiting superconductivity can be obtained at low temperatures, and the sintering temperature is also low.

According to the production method of the present invention, a homogeneous oxide superconductor containing a high proportion of the desired crystalline phase, high density, and no cracks etc. can be obtained. is obtained.

Claims (2)

[Claims] (1) In the manufacturing method of Ba-rare earth element-Cu-O system oxide superconductor, mixed alkoxide solution of rare earth element and Cu is mixed with Ba(NO_3)_2 aqueous solution and/or B
A method for producing an oxide superconductor, characterized by using a raw material powder prepared by hydrolysis with an a(NO_2)_2 aqueous solution. (2) Rare earth elements are Y, Yb, Ho, Er, Eu, Sc
, La, Nd, Pm, Sm, Gd, Tb, Dy, Tm,
The method for producing an oxide superconductor according to claim 1, wherein the oxide superconductor is one or more selected from the group consisting of Lu.