JPH0621034B2 - Copper alkoxide manufacturing method and superconducting powder manufacturing method using the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a copper alkoxide and a method for producing a raw material powder for a high temperature superconducting ceramic material using the copper alkoxide produced by this method. More specifically, it relates to a method for producing a raw material powder of an oxygen-deficient perovskite type high temperature superconducting ceramic material by an alkoxide method.

[Prior Art] YBa ₂ Cu ₃ O _7-y (y is the oxygen deficiency amount) is known as an oxygen-deficient perovskite-type high-temperature superconducting ceramic material. Conventionally, the raw material powder of YBa ₂ Cu ₃ O _7-y is obtained, for example, by yttrium oxide, barium carbonate, and copper oxide starting materials are pulverized and mixed in a mortar, and the mixture is calcined to cause a solid-phase reaction. .

When a raw material powder for a high temperature superconducting ceramic material is prepared by the alkoxide method, which is one of the liquid phase reactions, one of the starting materials, copper alkoxide, is replaced with copper chloride and sodium alkoxide as shown in the following formula. It is produced by the reaction.

_{CuCl 2 + 2NaOR → Cu (OR} ) 2 + 2NaCl ...... (1) starting such process is yttrium oxide material powder by [Problems to be Solved by the Invention solid phase reaction (R is an alkyl group having 1 or 2 carbon atoms) Even if the raw materials are carefully pulverized and mixed and calcined, the obtained powder has poor composition uniformity and is unlikely to be fine particles. Microscopically observing the high temperature superconducting ceramic material obtained by firing this raw material powder, there are many voids (pores), so the flow of macroscopic transport current is obstructed and superconducting properties cannot be improved. .

In the conventional synthesis of copper alkoxide by the alkoxide method, unreacted or by-produced sodium ions such as NaCl are left as impurities in the copper alkoxide. The alkali metal impurities such as sodium adversely affect the properties of the high temperature superconducting ceramic material. For this reason, it has not been possible to adopt the conventional alkoxide method by liquid phase reaction in which all powder compositions are dissolved in an organic solvent for the production of superconducting powder.

An object of the present invention is to provide a method for producing a copper alkoxide which is highly pure without alkali metal impurities and obtains a copper alkoxide soluble in an organic solvent. It is to provide a method for producing a superconducting powder capable of producing a raw material powder of a high-temperature superconducting ceramic material composed of fine particles.

[Means for Solving the Problems] The present inventors have found that methyl alcohol, ethyl alcohol,
The inventors have found that copper alkoxides that are insoluble in organic solvents such as normal butyl alcohol, benzene, xylene, and torunene are soluble only in secondary butyl alcohol, and have completed the present invention.

That is, the method for producing a copper alkoxide of the present invention is to react an organic solution of an alkaline earth metal alkoxide with an organic solution of copper acetate to produce a precipitate containing a copper alkoxide,
In this method, the precipitate is dissolved in secondary butyl alcohol, the by-products are removed from the butyl alcohol solution, and then the copper alkoxide is extracted.

Further, the method for producing the superconducting powder of the present invention comprises mixing a secondary butyl alcohol solution of copper alkoxide prepared by the above-mentioned method of producing copper alkoxide with an organic solution of an alkaline earth metal alkoxide and an alkoxide of yttrium or lanthanoid element. The mixed organic solution is hydrolyzed to form a precipitate, and the precipitate is dried and then calcined to obtain a superconducting powder.

The present invention will be described in more detail.

(a) Synthesis of copper alkoxide Alkaline earth metal alkoxide is alkaline earth metal (B
e, Mg, Ca, Sr, Ba, Ra) is made by reacting with alcohol. The following formula is an example in which the alkaline earth metal is Ba and the alcohol is butyl alcohol.

Ba + 2BuOH → Ba (OBu) ₂ + H ₂ (2) The reaction between the alkaline earth metal alkoxide and copper acetate converts them into alcohol, benzene, xylene, and
It is carried out by preparing an organic solution dissolved in an organic solvent such as toluene and mixing it in a stoichiometric ratio.

Ba (OBu) ₂ ＋ Cu (OAc) ₂ → Ba (OAc) ₂ ＋ Cu (OBu) ₂ …… (3) Next, after removing the solvent of this organic solution by evaporation, etc.,
The precipitate produced by this reaction is dissolved in secondary butyl alcohol. The secondary butyl alcohol is used as a solvent here because only this alcohol has the property of dissolving copper alkoxide, and barium acetate, which is a by-product, is insoluble in this alcohol and It can be easily removed.

By-product barium acetate is removed from the secondary butyl alcohol solution of copper alkoxide by a suitable method such as filtration or centrifugation, whereby a secondary butyl alcohol solution of copper alkoxide is obtained. When the copper alkoxide is obtained in the form of powder, the solvent tert-butyl alcohol is removed by evaporation, followed by drying and calcination.

(b) Synthesis of superconducting powder Superconducting powder of the present invention is a copper alkoxide and an alkaline earth metal alkoxide and yttrium or lanthanoid element (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, L
The starting material is the alkoxide of u). The superconducting powder of the present invention can be obtained by using a lanthanoid element alkoxide instead of the yttrium alkoxide.

The copper alkoxide needs to be used in the form of a solution of copper alkoxide in tert-butyl alcohol obtained by removing by-products from the tert-butyl alcohol solution in (a). Unlike copper alkoxides, other alkaline earth metal alkoxides and yttrium or lanthanide element alkoxides are soluble in many organic solvents such as methyl alcohol, ethyl alcohol, normal butyl alcohol, benzene, xylene, and toluene. Although the above-mentioned organic solvent can be used as the solvent, it is preferable to use sec-butyl alcohol which is a solvent for the copper alkoxide because the work is easy. The above alkoxide organic solvent is mixed in such a manner that the metal atoms of each alkoxide have the following formula.

Y (or Ln): M: Cu = 1: 2: 3 (4) (Ln is a lanthanoid element, M is an alkaline earth metal) The hydrolysis of the mixed organic solution is decarbonated distilled water or diluted ammonia water. It is performed by adding another alkaline aqueous solution.

This addition produces a powdery precipitate. This precipitate is removed from the mother liquor by a suitable method such as filtration, centrifugation, evaporation of the mother liquor, and the like. The taken-out precipitate is dried under reduced pressure or atmospheric pressure at room temperature to around 100 ° C. until the solution adhering to the surface of the precipitate is almost evaporated. The dried precipitate is calcined at a temperature range of 500 ° C to 1000 ° C under atmospheric pressure to form a ceramic powder.

Since this ceramic powder does not require addition of other cations or anions due to hydrolysis of alkoxide, it has high purity and a uniform composition, and is a fine particle having a particle size of several tens of tens to several hundred liters. Since it is synthesized with a predetermined atomic ratio, it has an oxygen-deficient perovskite type crystal structure represented by orthorhombic YBa ₂ Cu ₃ O _7-y or LnBa ₂ Cu ₃ O _7-y .

[Advantages of the Invention] As described above, according to the present invention, the copper alkoxide could not be produced without impurities by the alkoxide method because copper alkoxide was insoluble in many organic solvents. By finding that dibutyl alcohol is soluble in copper alkoxide, it is possible to obtain a high-purity copper alkoxide containing no alkali metal impurities.

By mixing this secondary butyl alcohol solution of copper alkoxide with the organic solvent of other alkoxide, YBa ₂ Cu was prepared by the alkoxide method for all the compositions of the raw material powder.
A raw material powder of an oxygen-deficient perovskite type high temperature superconducting ceramic material such as ₃ O _7-y or LnBa ₂ Cu ₃ O _7-y can be produced.

According to the production method of the present invention using this alkoxide method, it is possible to obtain a ceramic powder having high purity and extremely close to a target atomic ratio and excellent in composition uniformity and having high-temperature superconducting properties.

[Examples] Next, examples of the present invention will be described.

<Example 1> High-purity metal barium and normal butyl alcohol were directly reacted under reflux to synthesize barium normal butoxide. An ethanol solution of copper acetate was mixed with the butanol solution of barium normal butoxide in a stoichiometric ratio, and the mixture was refluxed at 80 ° C. for 1 hour to produce a precipitate composed of copper alkoxide and barium acetate.

When the mother liquor was removed by evaporation and the residual precipitate was added with secondary butyl alcohol and stirred, the copper alkoxide precipitate was dissolved, and barium acetate was not dissolved and precipitation continued. This by-produced barium acetate was removed by a centrifuge to obtain a solution of copper alkoxide in tert-butyl alcohol.

Further, the mother liquor was removed by evaporation, and the obtained powdery copper alkoxide was dried to obtain a copper alkoxide powder.
When the particle size of this powder was measured by an electron microscope, it was 0.
The particles were 01 to 0.1 μm. As a result of chemical analysis, it was a highly pure substance with impurities of 0.1% or less.

<Example 2> The secondary butyl alcohol solution of the copper alkoxide obtained in Example 1 was added with the secondary butyl alcohol solution of yttrium alkoxide and barium alkoxide, and the mixture was stirred.
Mix by refluxing at ° C. At this time, the respective alkoxides were mixed so that the atomic ratio was Y: Ba: Cu = 1: 2: 3.

Decarboxylated distilled water was added dropwise to the mixed solution under reflux to hydrolyze it to obtain a precipitate. The precipitate was taken out by removing the mother liquor by evaporation and dried at 70 ° C. for 12 hours to obtain a powder.

The obtained powder was calcined at 920 ° C. for 1 hour, and its crystal structure was examined by X-ray diffraction to find that it was orthorhombic YBa ₂ Cu ₃ O _7-y . This calcined powder was further subjected to composition analysis for each powder by an energy dispersive X-ray analyzer, and the standard deviation thereof was calculated. The results are shown in the table.

Further, the calcined powder was pressure-molded into pellets and sintered in an oxygen atmosphere at 920 ° C. for 3 to 5 hours at a temperature lowering temperature of 100 / ° C. hr. The Meissner effect, which is a superconducting property of this sintered body, was measured. As shown in the figure, the resistance value became 0 at 92K.
In the figure, the horizontal axis is temperature and the vertical axis is specific resistance.

<Comparative Example> Yttrium oxide, barium carbonate, and copper oxide were carefully pulverized and mixed in a mortar so as to have a predetermined atomic ratio, and the mixture was calcined and solid-phase reacted to obtain a powder. An energy dispersive X-ray analyzer is used to analyze the composition of each powder,
The standard deviation was calculated. The results are shown in the table.

It can be seen from the table that the powder of this example has a standard deviation of about one order of magnitude smaller than copper of the comparative example with respect to copper and barium, which indicates that the powder synthesized by the alkoxide method is more uniform than the powder synthesized by the solid phase method. understood.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing temperature dependence of electric resistance of a ceramic sintered body according to an example of the present invention.

Claims (3)

[Claims] 1. A step of reacting an organic solution of an alkaline earth metal alkoxide with an organic solution of copper acetate to produce a precipitate containing a copper alkoxide, and a step of dissolving the precipitate in secondary butyl alcohol. And a step of removing a by-product from the secondary butyl alcohol solution and then extracting a copper alkoxide. 2. A step of reacting an organic solution of an alkaline earth metal alkoxide with an organic solution of copper acetate to produce a precipitate containing a copper alkoxide, and a step of dissolving the precipitate in secondary butyl alcohol. A step of mixing a secondary butyl alcohol solution of copper alkoxide from which by-products have been removed from the secondary butyl alcohol solution with an organic solution of an alkaline earth metal alkoxide and a yttrium alkoxide, and hydrolyzing the mixed organic solution. And a step of producing a precipitate, and a step of drying the precipitate and then calcining to obtain a superconducting powder. 3. A step of reacting an organic solution of an alkaline earth metal alkoxide with an organic solution of copper acetate to produce a precipitate containing copper alkoxide, and a step of dissolving the precipitate in secondary butyl alcohol. A step of mixing a secondary butyl alcohol solution of copper alkoxide from which the by-products are removed from the secondary butyl alcohol solution with an organic solution of an alkaline earth metal alkoxide and a lanthanoid element alkoxide; and mixing the mixed organic solution with water. A method for producing a superconducting powder, which comprises: a step of decomposing to generate a precipitate; and a step of drying the precipitate and then calcining to obtain a superconducting powder.