JPH0653563B2 - Method for producing complex oxide - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a composite oxide, and particularly to a method for producing a composite oxide suitable for obtaining an oxide-based superconducting material. The present invention also relates to a method for producing a composite oxide which is a functional material used in the electronics field.

[Conventional technology]

A superconducting material such as YBa ₂ Cu ₃ O _7-X sintered body has been conventionally used as Y ₂ O ₃ , Ba.
It is manufactured by pulverizing and mixing Co ₃ and CuO powder in a mortar, firing at high temperature, and solid-phase reaction thereof. In addition, for the purpose of homogeneity of composition and micronization, for example, by adjusting the pH of a solution in which a salt of yttrium, barium, and copper is dissolved, a coprecipitation method of wet type such that a precipitate is simultaneously formed as an oxalate is formed. It is known to obtain a metal salt and calcine this to produce a composite oxide.

[Problems to be solved by the invention]

However, the conventional method of starting from powder of each component and using solid phase reaction has a problem in homogeneity of composition, densification of structure, and miniaturization because it is difficult to make the starting material powder ultrafine, and In order to obtain a uniform phase, it is necessary to repeat calcination and pulverization, and the superconducting properties tend to deteriorate.

Further, also in the wet coprecipitation method using oxalate, due to the difference in pH value when each component of yttrium, barium and copper forms a precipitate, problems such as decrease in yield and deviation of composition occur, Although a raw material powder having a finer structure can be obtained as compared with the mixed solid-phase method of (1), the effect on the superconducting properties, particularly the critical current density Jc is small, and many problems remain.

Further, a Atsushi Nobori from room temperature at the firing to the firing temperature, have been used in conventional heating, performed at a heating rate of about 3 ° C. / min, for heating rate is slow, in the middle firing BaCuO ₂ Impurity phase that is not superconducting phase such as. Also,
In the production of complex oxides by solid-state reaction, the starting raw material powder is not ultrafine powder, so it is necessary to maintain the firing temperature for a long time to promote diffusion in order to obtain a superconducting phase, but YBa ₂ Cu ₃ When O _7-X is held at the firing temperature for a long time, an impure phase often appears.

In order to eliminate the drawbacks due to the solid phase reaction, the present inventors first dissolved one or more kinds of ethylenediaminetetraacetic acid compounds of metal elements in water to form a uniform solution, and evaporated the water to form a gel. The inventors have invented a method for producing a complex oxide in which a substance is obtained and then fired (Japanese Patent Application No. 63-7207).
No. 5), it was found that even in this method, the generation of the impure phase is unavoidable at the above-mentioned temperature rising rate used in the conventional firing.

[Means for solving problems]

The present inventor has conducted research in order to solve the above problems, and when the temperature is rapidly raised in the above-described manufacturing method, an impure phase is not formed during firing, and thus a complex oxide containing no impure phase is obtained. I found that I could do it. The temperature rising rate in the rapid temperature rising is in the range of 20 ° C / min to 200 ° C / min.

That is, the present invention comprises dissolving an ethylenediaminetetraacetic acid compound of one or more kinds of metal elements in water to form a uniform solution, evaporating water to obtain a gel-like substance, and then firing the gel-like substance. In the method for producing a complex oxide, the temperature rising rate in firing the gel-like substance is 20 ° C / min to 200 ° C.
The method is a method for producing a complex oxide, characterized in that the temperature is rapidly raised at a rate of / min.

Further, during the firing, the holding time at the firing temperature is preferably 2 hours or less, and in such a case, only a single phase is produced and an impure phase is not formed.

As the ethylenediaminetetraacetic acid compound of the metal element used in the present invention, tetraacetic acid compounds such as yttrium, barium, copper, aluminum, titanium, zirconium, bismuth, calcium, strontium, iron, cobalt, nickel, zinc and lanthanum are used. For the production of superconductors, yttrium, barium, copper or calcium, strontium, bismuth, copper or lanthanum, barium, copper ethylenediaminetetraacetic acid compounds are preferred. The ethylenediaminetetraacetic acid compound of the metal element used in the present invention can be used alone in the case of ethylenediaminetetraacetatobarium titanate or the like.

The concentration of the ethylenediaminetetraacetic acid compound of the metal element in the aqueous solution must be equal to or lower than the saturated solubility of the compound to form a uniform solution, but it is preferably as high as possible in order to evaporate water. Evaporation of water from the aqueous solution of the ethylenediaminetetraacetic acid compound of the metal element can be carried out by a conventional method. For example, heating or vacuum evaporation can be performed, but heating is preferably maintained at a temperature of around 80 ° C.

The rate of temperature rise, the firing temperature, and the holding time at that temperature when firing a gel-like substance obtained by the evaporation of water from an aqueous solution of an ethylenediaminetetraacetic acid compound of a metal element depend on the type of the target complex oxide. There are suitable values for each,
When a gel-like substance obtained from a mixed aqueous solution of ethylenediaminetetraacetic acid compounds of yttrium, barium, and copper is fired to produce a superconductor, the temperature rising rate is 30 ° C / min.
A firing temperature of 800 ° C. and a holding time of 1 hour are preferable.

In addition, the firing temperature in the firing can be made lower than in the case of the solid-phase reaction or the coprecipitation method, and the target composite oxide can be obtained at 720 ° C to 950 ° C. In addition, during the firing, it is not necessary to keep the firing temperature for a long time, and if the firing temperature is held for a long time, an impure phase is generated. Therefore, the holding time is 2 hours or less. Then, in the firing, the object is obtained even if the temperature is raised and the temperature is lowered immediately after reaching the above-mentioned firing temperature.

A thin film or thick film of a superconductor having excellent superconducting properties can be obtained by coating the substrate with the uniform solution, evaporating water to form a gel-like substance, and baking the gelled substance.

INDUSTRIAL APPLICABILITY The method for producing a composite oxide of the present invention is effective for producing functional ceramics other than superconducting materials and structural ceramics.

[Work]

A gel-like substance obtained by dissolving an ethylenediaminetetraacetic acid compound of one or more metal elements in water to form a uniform solution, and evaporating the water has two or more metal elements uniformly dispersed. Therefore, a homogeneous composite oxide can be obtained by firing this gel-like substance. Moreover, in the calcination, calcination at a low temperature, rapid temperature increase, and holding at the calcination temperature for a short period of time make it possible to easily obtain a composite oxide with good productivity.

In the method of solid-phase reaction in the case of producing a superconducting material, it is necessary to repeat calcination-pulverization in order to obtain a uniform phase. -No need to repeat grinding. In addition, since the metal elements are evenly dispersed during firing, it is possible to produce the target product by rapidly raising the temperature and holding it at the firing temperature for a short time. Based on this, for example, YBa ₂ Cu ₃ O _7-X is fired. In that case, an impure phase such as BaCuO ₂ does not appear and the YBa ₂ Cu ₃ O _7-X single phase can be easily produced.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples.
The present invention is not limited to the following examples unless it exceeds the gist.

Example 1 Ethylenediaminetetraacetatoammonium ammonium salt 0.01 mol Ethylenediaminetetraacetatoammonium ammonium salt 0.02 mol Ethylenediaminetetraacetatoammonium cuprate
Weigh 0.03 mol, put it in a beaker and dissolve with 100 ml of water to make a uniform solution. The solution is placed in a hot air drier (80 ° C.) and allowed to evaporate throughout the day to give a gel-like substance. It was taken out of the beaker, placed on a quartz boat, heated in air at a temperature rising rate of 30 ° C./min to 800 ° C., kept at that temperature for 1 hour for firing, and then cooled in a furnace. Thus, 5.7 g of ultrafine powder made of a complex oxide of yttrium, barium and copper was obtained. The powder was examined by X-ray diffraction. The X-ray diffraction graph is shown in FIG. The powder is in a YBa ₂ Cu ₃ O _7-X orthorhombic single phase. Further, the powder was pressure-molded at 1000 kg / cm ² , and the compact was subjected to main firing at 900 ° C. for 8 hours while flowing oxygen 1 / min to obtain a superconducting bulk body.

Comparative Example Commercially available Y ₂ O ₃ , BaCO ₃ , and CuO powders were weighed so that the molar ratio was 1: 2: 3, mixed well in a mortar, and heated in air at a heating rate of 3 ° C / min. It was heated to 950 ° C., kept at that temperature for 12 hours, and then fired by furnace cooling.
The powder obtained was examined by X-ray diffraction. The X-ray diffraction graph is shown in FIG. According to FIG. 2, an impure phase exists.

〔The invention's effect〕

According to the present invention, a homogeneous composite oxide containing no impure phase can be obtained.

In the present invention, an ethylenediaminetetraacetic acid compound of one or more metal elements is dissolved in water to form a uniform solution,
The gel-like substance obtained by evaporating water has a metal element uniformly dispersed therein, so that the temperature can be rapidly raised during firing, and the firing temperature is low and the holding time is also long. A short and homogeneous composite oxide is obtained. further,
It is obtained as an ultrafine powder, and the firing temperature may be relatively low when the powder is molded and then subjected to main firing.

For example, in the superconducting material Y-Ba-Cu-O system, YBa ₂ Cu ₃ can be obtained by holding the temperature rising rate of 30 ° C / min of 800 ° C for 1 hour.
A composition of O _7-X orthorhombic crystal was obtained, which did not cause compositional deviation and decrease in yield as in the conventional solid phase method and wet coprecipitation method. And this can obtain a significant improvement in the critical current density Jc.

Further, a thin film or a thick film of a superconductor having excellent superconducting properties can be obtained by coating the above-mentioned homogeneous solution on a substrate, evaporating water to form a gel-like substance, and baking it.

Furthermore, this method for producing a composite oxide is effective for producing functional ceramics other than superconducting materials and structural ceramics.

[Brief description of drawings]

FIG. 1 shows an X-ray diffraction graph of a Y—Ba—Cu—O-based complex oxide obtained by the method for producing a complex oxide of the present invention, and FIG. 2 shows a conventional solid-phase method. Y-Ba-Cu
The X-ray-diffraction graph of -O type complex oxide is shown.

Continuation of the front page (56) Reference JP 64-65003 (JP, A) JP 64-65007 (JP, A) JP 63-310721 (JP, A) JP 64-11977 (JP , A) JP 64-24016 (JP, A) JP 63-307113 (JP, A)

Claims (2)

[Claims] 1. A composite comprising one or two or more kinds of ethylenediaminetetraacetic acid compounds of metal elements dissolved in water to form a uniform solution, water is evaporated to obtain a gel-like substance, and then the mixture is fired. In the method for producing an oxide, the method for producing a complex oxide is characterized in that the rate of temperature rise during firing of the gelled substance is a rapid temperature rise of 20 ° C / min to 200 ° C / min. 2. The method for producing a complex oxide according to claim 1, wherein a holding time at a firing temperature in firing the gel-like substance is 2 hours or less.