JPH01179721A - Manufacturing method for high-temperature superconducting ceramic raw material powder - Google Patents

Abstract

PURPOSE:To obtain easily sinterable powder for the raw material for the title ceramic by coprecipitating from a soln. contg. a rare earth compd., an alkaline earth compd., and a Cu compd. with a precipitant, and precalcining the coprecipitate. CONSTITUTION:Each soln. contg. (A) a compd. of a rare earth element such as Sc, Y, or lanthanoids, etc., (B) a compd. of an alkaline earth metal such as Ca, Ba, Sr, etc., and (C) a compd. of Cu such as copper chloride, copper nitrate, etc., is mixed, pref. in 1:(1-3):(1-4) atomic proportion of A:B:C, and a coprecipitate is formed by dropping a precipitant such as aq. soln. of cautic alkali, ammonia, etc. to the mixture while applying ultrasonic wave vibration (pref. 10W-1kW, for 1-100min). The coprecipitate is filtered, washed, and dried, then presintered at 500-950 deg.C. The raw material powder having >=5.1g/cm<3> density and larger critical current density than conventional products is obtd. by sintering the obtd. presintered product, after compression-molding, at 700-950 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing rare earth element-alkaline earth element-copper oxide based high temperature superconducting ceramic raw material powder.

(Prior art and its problems) Among rare earth element-alkaline earth element-copper oxide ceramics, those having an oxygen-deficient layered perovskite structure are superconducting materials with a high critical temperature of 90 or higher. has become well known and is expected to be applied in many fields.

These rare earth element-alkaline earth element-copper oxide-based high-temperature superconducting ceramics become superconducting even when cooled with an inexpensive coolant such as liquid nitrogen, so they only show superconducting state in liquid helium. If it can be used in superconducting magnets instead of Nb-Ti superconducting alloys, there will be great economic advantages.

However, the superconducting ceramics that have been made so far have a low critical current density of several + A/cffl, which is 1/200 to 1/200 of that of the Nb-Ti superconducting alloys conventionally used for boat fishing.
The drawback was that it was only 400.

Another problem was that the temperature range of the transition from normal conductivity to superconductivity was wide and lacked steepness.

It has been pointed out that one of the causes of these problems is that superconducting ceramics are porous and have a low density.

Hitherto, rare earth element-alkaline earth element-copper oxide-based high-temperature superconducting ceramics have been made by pressurizing and sintering raw material powders prepared by dry or wet mixing.

In the dry mixing method, powders of oxides or carbonates of the constituent components of superconducting ceramics, such as Y2O3, BaC0=,
Using CuO powder as a starting material, it is ground and mixed using a ball mill, crusher, pestle, mortar, etc., and then sintered.
This is a method for preparing raw material powder for superconducting ceramics.

On the other hand, the wet mixing method uses the same starting materials as the dry mixing method.
This is a method in which a solvent that does not react with the starting materials and does not substantially dissolve them is added and mixed mechanically.

Both of the above heating methods are technically easy and highly safe methods, but the obtained raw material powder has a large particle size of 1 to 5 μm or more, the particle size distribution is not uniform, and there is also a large variation in components. .

Therefore, high-temperature superconducting ceramics made by sintering this raw material powder have a problem of low density and low critical current density.

(Technical Means for Solving Problems) The present invention is a method for producing easily sinterable superconducting ceramic raw material powder, which solves the drawbacks of conventional mixing methods.

The present invention includes (1) bringing a solution of a rare earth element compound, an alkaline earth element compound, and a copper compound into contact with a precipitant while applying ultrasonic vibration to form a coprecipitate; Rare earth elements characterized by temporary sintering
Method for producing alkaline earth element-copper oxide-based high-temperature superconducting ceramic raw material powder, and (2) forming a coprecipitate by contacting a solution of a rare earth element compound, an alkaline earth element compound, and a copper compound with a precipitate forming agent A method for producing rare earth element-alkaline earth element-copper oxide-based high-temperature superconducting ceramic raw material powder, characterized by applying ultrasonic vibration to the coprecipitate solution and then pre-sintering the coprecipitate. be.

In the present invention, the rare earth element refers to at least one kind of rare earth element selected from Sc, Y, and the lanthanum series elements of the periodic table, and a specific example of the lanthanum series element is La.
, Nd, Sm, Eu, Gd and Er. In the present invention, the alkaline earth element refers to at least one kind of alkaline earth element selected from the mA group of the periodic table, and specific examples thereof include Ca, Ba, and Sr.

In addition, the high temperature superconducting ceramic in the present invention contains a portion of copper up to 50 mol% of other metals, such as V, Zr.
, , Nb, Mo, , Hf, Ta, W, , Pb or Bi are also included.

The rare earth element compound, alkaline earth element compound, and copper compound used in the present invention include hydroxide, hydrochloride,
Examples include nitrates, organic acid salts, and alkoxides.

Preferred solvents for the above compounds include water, alcohols, ethers, ketones, esters, halogenated hydrocarbons, N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, and dimethylsulfoxide. used.

In the present invention, as the precipitant, an aqueous caustic alkali solution, aqueous ammonia, ammonium carbonate, amines, oxalic acid, water, etc. can be used. These precipitants may be used alone or in combination of two or more.

A precipitation forming agent is mixed with a solution of a rare earth element compound (hereinafter referred to as solution A), a solution of an alkaline earth element compound (hereinafter referred to as solution B), and a solution of a copper compound (hereinafter referred to as solution C) while applying ultrasonic vibration. to form a coprecipitate,
Alternatively, there is no particular restriction on the method of mixing a precipitant into a solution of the above compound to form a coprecipitate and applying ultrasonic vibration to the coprecipitate solution. For example, various methods such as those shown below may be used. Can be adopted.

(2) A method in which solutions A, B, and C are mixed in advance, and a precipitate forming agent is mixed therein while applying ultrasonic vibration. (2) A method in which solutions A, B, and C are mixed in advance, a precipitate is mixed therein to form a coprecipitate, and ultrasonic vibrations are applied to the coprecipitate solution.

(2) A method in which a precipitant is mixed with each of solutions A, B, and C while applying ultrasonic vibration, and then each coprecipitate solution is mixed. (2) A method in which a precipitant is mixed in each of solutions A, B, and C, and then ultrasonic vibration is applied to the mixed solution of each coprecipitate solution. (2) A method of mixing solution A and a precipitate forming agent while applying ultrasonic vibrations to form a coprecipitate, and adding solution C and a precipitate forming agent while applying ultrasonic vibrations to the coprecipitate. (2) A method of mixing solutions A and B with a precipitate to form a coprecipitate, adding solution C and a precipitate to the coprecipitate, and then applying ultrasonic vibration to the coprecipitate solution.

The atomic ratio of rare earth elements, alkaline earth elements, and copper in the coprecipitate obtained in the above step is rare earth element: alkaline earth element: copper - 1:0.5 to 4:1 to 5. It is preferable that the range is particularly rare earth element:alkaline earth element:copper=
A preferred range is 1:1 to 3:1 to 4.

Next, the ultrasonic vibrations applied in each of the above steps can be performed using various commercially available ultrasonic generators.

The solutions A, B, and C2 or the solution containing the coprecipitate are attached to an ultrasonic generator, and preferably the output is LOW to IK.
W, operate the oscillator for 1 to 100 minutes to crush and disperse the precipitated aggregates formed by ultrasonic vibration.

The solution containing the coprecipitate subjected to the ultrasonic vibration is filtered, and the coprecipitate is washed, dried, and then pre-sintered.

Preferably, the pre-sintering temperature is 500 to 950'C. If the pre-sintering temperature is lower than 500°C, the coprecipitate will not be sufficiently converted into an oxygen-deficient layered perovskite structure, and a good raw material powder for high-temperature superconducting ceramics will not be obtained. Further, if the pre-sintering temperature is higher than 950°C, it is not preferable because the coprecipitate may melt during the pre-sintering or the particles may become coarse.

By molding the raw material powder obtained by the method of the present invention under pressure and sintering it at 700 to 950°C, high-temperature superconducting ceramics can be obtained.

(Effects of the present invention) The rare earth element-alkaline earth element-copper oxide-based high temperature superconducting ceramic raw material powder obtained by the method of the present invention has a fine particle size distribution of less than 1 μm, and has a fine particle size distribution and component elements. It is a powder with a uniform compound composition. The superconducting ceramic obtained by sintering this raw material powder has a density of 5.
It is dense with a density of 1 g/c+f1 or more, and the critical current density is also larger than that of the conventional method.

(Example) Examples of the present invention are shown below.

Example 1 A solution of 0.4 mol of diethylamine dissolved in 300 ml of water was added to 300 d of 3N ammonia water to prepare a precipitate.

500 d of an aqueous solution of 0.2 mol of barium nitrate, 500 ml of an aqueous solution of 0.1 mol of yttrium nitrate. and chloride a0.
10 at a power of 80 W into each of 500 ml of a 3 molar aqueous solution.
While applying ultrasonic vibration for a minute, the above precipitant was added dropwise to form a precipitate.

The above three types of precipitation solutions were mixed and stirred, and then filtered, and the precipitates were washed with water and dried. This powder was pre-sintered at 750°C for 2 hours and ground in a ball mill to obtain a raw material powder.

When this raw material powder was molded using IT/cffl and fired at 900°C for 2 hours, a superconducting ceramic sintered body with a density of 5.43 g/cffl, a critical temperature of 96, and a critical current density of 350 A/cml was obtained. Ta.

Example 2 The precipitate forming agent of Example 1 was mixed with 500 m of an aqueous solution of 0.2 mol of barium nitrate and 50 ml of an aqueous solution of 0.1 mol of yttrium nitrate.
and 500 d of an aqueous solution of 0.3 mol of copper chloride to form a precipitate.

The above three types of precipitation solutions were mixed and stirred, and the
Apply ultrasonic vibration for a minute, then filter, wash the precipitate with water,
It was dried. This powder was pre-sintered at 750°C for 2 hours and ground in a ball mill to obtain a raw material powder.

This raw material powder was molded at It/afl and heated at 900°C for 2
After firing for an hour, a superconducting ceramic sintered body having a density of 5.20 g/afl, a critical temperature of 92, and a critical current density of 325 A/cm was obtained.

Example 3 Y ethoxide (Y(○C2H3), :l 0.1 mol,
Ba ethoxide (B a (OCzHs) z]0,
2 mol, Cu ethoxide (Cu (○C2H3)2))
0.3 mol in 1000 ml of ethanol).

Water was gradually added dropwise to this ethanol solution while applying ultrasonic vibration at an output of 100 W for 10 minutes to generate a coprecipitate.

The resulting solution containing the coprecipitate was filtered, and the precipitate was washed with water and dried. This powder was pre-sintered at 750°C for 2 hours and ground in a ball mill to obtain a raw material powder.

When this raw material powder was molded at 1 t/cf and fired at 900'C for 2 hours, a superconducting ceramic sintered body with a density of 5.40 g/cffl, a critical temperature of 95, and a critical current density of 365 A/c+fl was obtained. .

Example 4 Y ethoxide (Y (OCzHs) 3: 10.1 mol,
Ba ethoxide (B a (OCzHs) 2:] 0
, 2 mol, Cu ethoxide (Cu (OCzHs)
z) ) 0.3 mol was dissolved in 1000 mft of ethanol.

Water was gradually added dropwise to this ethanol solution to produce a coprecipitate.

The solution containing the obtained coprecipitate was heated for 30 minutes at an output of 100W.
Apply ultrasonic vibration for a minute, then filter, wash the precipitate with water,
It was dried. This powder was pre-sintered at 750°C for 2 hours and ground in a ball mill to obtain a raw material powder.

This raw material powder is lt, / cr? Shape with +, 90
When baked at 0'C for 2 hours, the density was 5.32g/c
ry, critical temperature 93, critical current density 330A/cff
1 of superconducting ceramic sintered bodies were obtained.

Example 5 The same procedure as Example 3 was carried out except that La epoxide was used instead of Y epoxide.

The density of the obtained high-temperature superconducting ceramic sintered body was 5.
35 g/cffl, critical temperature was 93, and critical current density was 325 A/c+fl.

Example 5 The same procedure as in Example 1 was conducted except that Ba ethoxide was partially replaced with Sr ethoxide.

The density of the obtained high-temperature superconducting ceramic sintered body was 5.
45g/crM, critical temperature is 97, critical current density is 3
It was 85A/cnT.

Comparative Example Yttrium oxide (Y2O,) 0.05 mol, barium carbonate (BaCO2) 0.2 mol, copper oxide (Cub) 0.
3 mol was added to water 50j2, mixed in a ball mill, filtered, and further placed in a dryer to remove moisture.

This mixed powder was pre-sintered at 850°C in air for 3 hours.

The pre-sintered mixed powder was ground in a ball mill and pre-sintered again. This operation was repeated four times to obtain a raw material powder.

When this raw material powder was molded at IT/CFFL and fired at 900°C for 2 hours, the density was 4, 1 g/c East H.
Only a superconducting ceramic having an m-field temperature of 90 and a critical current density of 35 A/cffl was obtained.

Claims (2)

[Claims] (1) A solution of a rare earth element compound, an alkaline earth element compound, and a copper compound is brought into contact with a precipitate forming agent while applying ultrasonic vibration to form a coprecipitate, and then the coprecipitate is pre-sintered. A method for producing rare earth element-alkaline earth element-copper oxide based high temperature superconducting ceramic raw material powder, characterized by the following. (2) A solution of a rare earth element compound, an alkaline earth element compound, and a copper compound is brought into contact with a precipitate forming agent to form a coprecipitate, and this coprecipitate solution is subjected to ultrasonic vibration, and then coprecipitation is performed. A method for producing rare earth element-alkaline earth element-copper oxide-based high-temperature superconducting ceramic raw material powder, which is characterized by pre-sintering a material.