JPH01176206A - Production of precursor of compound oxide - Google Patents

Abstract

PURPOSE:To obtain the title fine and uniform precursor useful as a superconducting material, functional material, etc., by hydrolyzing under a specific condition. CONSTITUTION:One or more alkoxides of rare earth elements (e.g. Y or Sm), one or more alkoxides of alkaline earth metals (e.g. Cu, Ti, Zr, Cr, Mo or Fe) and one or more alkoxides of transition metals except lanthanides are dissolved in an organic solvent (e.g. ethanol), blended and hydrolyzed with 0.5-2mol. based on the sum of alkoxy groups of the metal alkoxides of one or more amines such as (di)(tri)ethanolamine and/or one or more amides formamide, dimethylamide, (dimethyl)acetamide, crotonamide or N,N- diethylpropanamide and water and the solvent is removed by evaporation.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing a multicomponent ceramic precursor. More specifically, the present invention relates to a method for producing a composite oxide precursor that is a suitable raw material for producing oxide ceramics, such as superconducting materials. The composite oxide derived from the composite oxide precursor obtained by the present invention is expected to be used as a functional material in the electronics field including the above-mentioned superconducting material.

(Prior Art) Multi-component ceramics are usually manufactured by mixing powders of oxides of each component or their precursors, molding, and then firing. The oxides of each component are mixed in order to obtain pure oxides, to easily obtain oxides with a predetermined particle size, and to easily obtain raw materials with a predetermined composition. ing. Then, the mixture of oxide powders of each component undergoes a phase reaction by firing to produce a multi-component ceramic having a predetermined composition. For example, superconducting material YBa2C
The u3O7-x sintered body is produced by pulverizing and mixing powders of yttrium oxide, barium carbonate, and copper oxide in a mortar and firing them at a high temperature to cause a phase reaction between them (for example,
Superconducting Materials Chemistry Symposium Abstracts October 1987
2 pages, etc.)

The method of starting from powders of oxides of each of the above components or their precursors has the drawback that sintering occurs during firing, and even if a phase reaction occurs, the reaction is slow and the composition is not uniform. Efforts have been made to use oxides with a more uniform composition, and methods have also been proposed in which oxides are made from salts obtained by coprecipitation and used as raw materials. For example, for the purpose of compositional uniformity and fine particle formation, a salt produced by a wet co-precipitation method in which oxalate is simultaneously formed as a precipitate by adjusting the pH of a solution in which yttrium, barium, and copper salts are dissolved is used as a raw material. (Problem to be solved by the invention, etc.) (Problem to be solved by the invention) However, the conventional method using a phase reaction starting from powder of each component Because it is difficult to ultra-fine the starting raw material powder, there are problems with composition uniformity, structure densification, and refinement, and composition control is difficult, and in the case of superconducting materials, grain boundaries containing impurities cause Superconducting properties tend to deteriorate.

In addition, in the wet co-precipitation method using oxalic acid described above, differences in pH values when the components of yttrium, barium, and copper form precipitates cause a decrease in yield, deviation in composition, etc. Although raw material powder with a uniform and finer structure can be obtained compared to the above-mentioned surface phase method, it has little effect on superconducting properties, particularly on critical current density Jc, and many problems still remain. The reasons why the critical current density is still one to two orders of magnitude lower than the practical level include the influence of grain boundaries and the low density of ceramics.

An object of the present invention is to provide a method for producing a composite oxide precursor that solves the problems of the prior art.
An object of the present invention is to provide a method for producing a system precursor.

(Means for Solving the Problems) The present invention has been made by conducting research to solve the problems of the conventional method, and by eliminating at least one kind of rare earth element alkoxide, alkaline earth metal alkoxide, and lanthanide. (The present invention was based on the discovery that a composite oxide precursor having a fine and uniform composition can be obtained by mixing and reacting transition metal alkoxides in an organic solvent in the presence of amines and/or amides and water. completed.

That is, the present invention was developed as a result of various studies aimed at uniformly dispersing each component with a stoichiometric composition in ultrafine particles produced by hydrolysis of metal alkoxides. We have found that the addition of amines and/or amides is effective in improving the easy hydrolysis of transition metal alkoxides other than lanthanides and lanthanides, and the formation of precipitate particles by each alone.

Examples of rare earth element alkoxides include yttrium and samarium alkoxides, alkaline earth metal alkoxides include barium, strontium, and calcium alkoxides, and transition metal alkoxides other than lanthanides include, for example, copper. , titanium, zirconium, chromium, molybdenum, manganese, iron, cobalt, nickel, zinc, cadmium, and other alkoxides.

The amines used in the present invention include, for example, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, propylamine, butylamine, tert-butylamine, cyclohexylamine, benzylamine, aniline, diphenylamine,
Examples include triphenylamine, ethanolamine, jetanolamine, triethanolamine, N,N-dimethylcyclohexylamine, piperidine, and N-ethylaniline, with preference given to ethanolamine, diethanolamine, and triethanolamine.

Examples of amides include formamide, acetamide, dimethylamide, dimethylacetamide, crotonamide, and N,N-diethylpropanamide.

The amount of the amine added is preferably 0.5 to 2 times the number of moles of the total number of alkoxy groups in each metal alkoxide compound.

When mixing and reacting the various alkoxides with amines and/or amides, the presence of water causes the metal alkoxide to be hydrolyzed and a composite oxide precursor to be formed. Methods of adding water to make it exist include gradually adding diluted water to an organic solvent, blowing water vapor or a gas containing water vapor into the solution, and using moisture in the air. It will be done. The addition of water is preferably carried out after the briquette reaction in which the amines and/or amides are mixed with the various alkoxides described above.

The mixing and reaction of the above amines and/or amides is carried out in an organic solvent, and it is preferable that the various alkoxides and the amines and/or amides be dissolved in the organic solvent, such as methanol. , ethanolopeprobanol, etc. are used.

(Action) The amines and amides used in the reaction act on the alkoxy group of each alkoxide of rare earth elements, alkaline earth metals, and transition metals other than lanthanides, and by partially substituting or coordinating with these alkoxides, the alkoxides can be modified. It is presumed that it stabilizes and suppresses the rate of hydrolysis. As a result, the hydrolysis steps of rare earth element alkoxide, alkaline earth metal alkoxide, and transition metal alkoxide overlap, leading to the formation of uniform composition particles.

(Example) Hereinafter, the present invention will be specifically explained with reference to Examples.

The invention is not limited to this example only.

Example 1 0.5 g of yttrium ethoxide, 0 barium ethoxide
．． 95g, copper ethoxide 0.96g ethanol 40g
0rrdl, and add 1 ml of jetanolamine to this solution.
．． 54 g was added and thoroughly stirred at room temperature or below in a N2 stream. To this was added 0.49 g of water to carry out a hydrolysis reaction to obtain a uniform colloidal sol. The solid substance (gel) obtained by evaporating the solvent of this sol was heated to 110℃ for 2 hours.
After drying for 4 hours, it was calcined in air at 500°C for 4 hours, then molded into pellets at a pressure of 500 kg/cd, and calcined in an oxygen stream at 700°C for 24 hours. The particle size of the powder after firing at 500°C was as fine as about 5000A. Furthermore, the obtained sintered body was relatively dense with 80% of the theoretical density. The black sintered body after firing is YB with perovskite composition.
a, Cu, 0. It was confirmed by X-ray diffraction measurement that it was a -x orthorhombic sintered body.

Comparative Example 1 Using yttrium oxide, barium carbonate, and copper oxide as raw materials,
The mixture was weighed and mixed so that Y:Ba:Cu was 1:2:3, calcined in oxygen at 950°C for 24 hours, and then ground in an automatic mortar for 2 hours to form a powder with an average particle size of about 2 μm. , 1t/cr
After compression molding at 1 t/caf, cold isostatic wire forming at 7 t/caf, and sintering at 950° C. for 24 hours. The sintered body is [u2Y2
YBa2C containing some compositions such as 0s and BaCuO2
It was confirmed by X-ray diffraction measurement that it was a u3O7-x orthorhombic sintered body. Similarly, sintering was carried out at a firing temperature of 700°C, but no formation of YBa2Cu30t-x orthorhombic crystals was observed, and the density of the sintered body was approximately 70% of the theoretical value.
It was low.

Comparative Example 2 Cu powder, Ba (NO3) 2, Y2O as test reagents
3 are all 3N nitric acid solutions, and the molar ratio is Y:Ba:
The ratio of Cu was adjusted to 1:2:3 and mixed. A precipitated salt was produced in this solution at pH 4.6 using an ethanol solution of oxalic acid, filtered, dried at 110°C for 24 hours, calcined in air at 500°C for 4 hours, and then heated to 500°C.
It was molded into a pellet at a pressure of kg/cIIl and calcined at 800° C. for 24 hours in an oxygen stream.

The sintered body after firing was measured using X-ray diffraction, and YBa
, Cu, 0. -x Orthorhombic pattern could not be confirmed.

(Effects of the Invention) An oxide powder having very fine unit particles can be obtained from the composite oxide precursor of the present invention, and this oxide powder crystallizes quickly and is easily sintered. For example, superconducting material YBa2Cu
-0 series, even when fired at a low temperature of 700°C, YBa,
Cu30. A -x orthorhombic composition was obtained, and a relatively dense sintered body was obtained. In addition, there is no deviation in composition or decrease in yield as in the conventional phase method and coprecipitation method. By using this powder, conventional YBa2Cu, 0. It is expected that the critical current density (Jc), which has been a drawback of -x superconducting sintered bodies, will be significantly improved, and it is expected that practical application to superconducting wires and the like will be achieved.

In addition, the sol itself, in which fine colloidal particles are suspended, obtained in the intermediate stage is used to coat the substrate, screen print, etc., and by adding heat treatment (relatively low temperature) to this, excellent superconducting properties are achieved. YBa2Cu
30. -x film, it is possible to obtain a thick film.

Furthermore, according to the present invention, it is possible to obtain a composite oxide precursor that is a raw material for functional ceramics other than superconducting materials.

Claims (3)

[Claims] (1) Mixing and reacting at least one rare earth element alkoxide, alkaline earth metal alkoxide, and transition metal alkoxide other than lanthanide in an organic solvent in the presence of amines and/or amides and water. A method for producing a composite oxide precursor, characterized in that: (2) The above amine is at least one compound selected from ethanolamine, diethanolamine, and triethanolamine, and the amount thereof is 0.5 to 2 times the number of moles of the total number of alkoxy groups in each metal alkoxide compound. A method for producing a composite oxide precursor according to claim 1. (3) The above amides are formamide, dimethylamide,
The method for producing a composite oxide precursor according to claim 1, wherein the compound is at least one compound selected from acetamide, dimethylacetamide, crotonamide, and N,N-diethylpropanamide.