JPH01176222A - Production of oxide based superconducting powder - Google Patents

Abstract

PURPOSE:To efficiently obtain the title fine and globular powder, by drying powder obtained by atomizing uniformly blended solution of raw material and then heating the atomized raw material and simultaneously collecting the powder by applying direct current voltage to the powder. CONSTITUTION:A solution obtained by dissolving each raw material constituting oxide based superconducting powder consisting of nitric acid salt of Y, Ba, Cu, etc. in a solvent, is blended so as to be desired composition ratio to afford uniform mixed solution 2, which is then atomized with an atomizing apparatus 3 consisting of supersonic vibrator having 0.7-3MHz frequency and the atomized raw material 4 is conveyed to a particle classifier 5 to give an atomizing raw material 6 having mum particle size. Then the raw material 6 is fed into a heating oven 7 controlled to 700-1,100 deg.C by a sensor 8 and heated to provide the oxide based superconducting powder 9. The powder 9 and a solvent are fed into a collecting part 15, where solvent is removed by heating to about 1,100 deg.C and simultaneously the powder is charged by applying direct current voltage having 1,000-20,000V and deposited on a collecting plate 16 to collect the aimed powder.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for producing fine, spherical oxide-based superconducting powder. It has been made so that it can be compiled well. .

(Prior art) YB consisting of alkaline earth metal, rare earth element, copper and oxygen
Oxide-based superconductors such as a2Cu3O7-x and La5r2Cu07-X have a high critical temperature (Tc) and are expected to be used for applications. The oxide-based superconductor has conventionally been made from carbonates of alkaline earth metals (Ba) and the like as starting materials;
A composite oxide is produced by adding N amount of rare earth element (Y, La, etc.) oxide and copper oxide to a desired composition, mixing while grinding, and pre-calcining the mixture thus obtained. It was produced by pulverizing and classifying the powder, forming the resulting mixed powder into a desired shape, and subjecting it to sintering.

(Problems with conventional technology) However, in order to increase the density of the oxide-based superconducting molded body obtained in this way and improve its superconducting properties, the contact area between each powder must be large, and the sintering process must be performed. It is desirable to use powders that are as fine and spherical as possible so that solid-phase diffusion can occur sufficiently between the powders.

However, in conventional mechanical grinding methods, in order to obtain such fine powder, it is necessary to repeat grinding and classification many times, which makes the process very complicated, and it is difficult to obtain such fine powder. The shape of the powder obtained was mainly a polygonal shape with a protruding tip, and it was difficult to obtain a spherical powder.

(Objective of the Invention) The present invention was developed as a result of intensive studies in view of the above points, and its purpose is to efficiently produce fine and spherical oxide-based superconducting powder using a relatively simple process. The purpose is to provide a manufacturing method.

(Means for Solving the Problems) The method for producing oxide-based superconducting powder of the present invention includes (A) Each raw material constituting the oxide-based superconducting powder is dissolved in a solvent to form a solution, and then mixed to a desired composition ratio to form a uniform mixed solution.The mixed solution is heated to a frequency of 0. A step of atomizing with an ultrasonic vibrator of 7 to 3 MH2, classifying the particles of the atomized raw material liquid into a desired particle system, and transporting the atomized raw material liquid; A step of heating the oxide-based superconducting powder to 700 to 1100°C in an oxygen atmosphere having an oxygen partial pressure of It is characterized in that it is manufactured through a step of introducing the powder into a collecting section heated and maintained at ℃ to remove the solvent, and collecting the oxide-based superconducting powder in the collecting section by charging it with a DC voltage of 1000~AOOOV. That is.

In the present invention, as a method of dissolving each raw material constituting the oxide-based superconducting powder in a solvent to form a solution, 1, for example, Y
, a method of dissolving nitrates such as Ba and Cu in water, a method of dissolving these alkoxides (for example, ethoxide, etc.) in alcohol, a method of using these halides (for example, chloride, etc.), and the like.

In the present invention, the mixed solution obtained by mixing these solutions to a desired composition ratio is atomized by applying ultrasonic vibration, thereby producing atomized particles that are fine and relatively uniform in size. This is what you get. In this case, the frequency is O,? MB?
If the frequency is less than 3MHr, the particle size will increase and the variation in diameter will also increase.If the frequency exceeds 3MHr, the mixed liquid will not be able to follow the vibrations of the ultrasonic vibrator and atomization will not be performed sufficiently. 0.7~3MHz
It is necessary to atomize using an ultrasonic vibrator.

After the atomized raw material liquid obtained in this way is classified into the desired particle size, it is transported to a heating furnace using oxygen gas, etc.
Oxide-based superconducting powder is formed by heating and the action of oxygen, but in order to sufficiently oxidize the atomized raw material liquid and create an optimal composition for developing a superconducting state, an oxygen partial pressure of 0.2 atmospheres or more must be applied. It is necessary to heat in an oxygen atmosphere with

Further, if the heating temperature is less than 700°C, the oxidation will be insufficient, and if it exceeds 1100°C, the superconducting powder will partially melt, so it is necessary to heat it within the range of 700-1100°C.

The oxide-based superconducting powder obtained by this thermal decomposition is introduced together with the solvent therein and the decomposed solvent into a collecting section heated and maintained at 200°C to 900°C to remove the solvent and remove the oxide-based superconducting powder in the collecting section. Superconducting powder 1000 ~ aooov
It is charged and collected using a DC voltage. In this case, if the voltage is less than 100 OV, the powder will not be charged and cannot be collected, and if it exceeds 8000 volts, the diffusion of charged particles will be poor and the yield will be reduced. It is preferable to charge the powder and collect it. If the collection unit is collected at room temperature without heating, the solvent in the oxide-based superconducting powder or the decomposed solvent will be collected as is in the collector. Therefore, in the present invention, the collector is heated and held at 200 to 900°C to remove the solvent and collect only the oxide superconducting powder.

Next, embodiments of the present invention will be specifically described using FIGS. 1 and 2. FIG. 1 is an explanatory diagram showing an example of the apparatus used to carry out the present invention, and this apparatus is composed of the following steps A, B, and C (corresponding to A, B, and C in FIG. 1). ing.

(A) A step of atomizing a liquid raw material for oxide-based superconducting powder to create a mist raw material liquid with uniform particle sizes.

(B) A step of turning the atomized raw material liquid into oxide-based superconducting powder.

(C) The oxide-based superconducting powder obtained in step B is introduced together with a solvent into a collecting section heated and maintained at 200°C to 900°C to remove the solvent and remove the oxide-based superconducting powder in the collecting section. Process of charging and collecting with DC voltage This A,
The steps B and C are continuous. - Each step of A to C will be explained in detail below. In step A of FIG. 4 is an atomization RT station for the solution 2; 4 is the atomized raw material for the oxide-based superconductor; 5 is a particle classifier for the raw material 4;

The starting material 2 of the oxide-based superconductor that has been made into a solution has a frequency of 0.
．． After being atomized by an atomizer M3 comprising a 7 to 3 MH2 ultrasonic vibrator to become fine atomized particles with relatively uniform size, the atomized particles are conveyed to the particle classifier 5 by a conveying gas. The atomized raw material 4 here becomes an atomized raw material 6 consisting of a group of particles with a particle size of about several pm, the particle size distribution of which is further controlled by the weight difference.

Step B in FIG. 1 is a step in which the atomized raw material 6 classified in step A is turned into oxide-based conductive powder. 7 is a heating furnace, and 8 is a temperature sensor (thermocouple, etc.) for the heating furnace 7. , 9 is an oxide-based superconducting powder mixed with water vapor. The atomized raw material 6 is measured by a sensor 8 such as a thermocouple at a temperature of 700-1100.
Oxygen gas whose flow rate is controlled by a flow rate controller 1 is introduced into a heating furnace 7 whose temperature is controlled within a range of 0.degree. C., and becomes an oxide-based superconducting powder 9 by heating and the action of oxygen. Incidentally, since water or alcohol is usually used as a solvent to dissolve the starting material of the oxide superconducting powder 9, the oxide superconducting powder 9 contains a considerable amount of water. Furthermore, a halide such as a chloride may be used as the solvent.

In step C of the first UgJ, the oxide-based superconducting powder 9 obtained in step B is introduced into the collecting section 15 together with a solvent.
200°C to 900°C using a heating device (not shown)
At the same time, the oxide-based superconducting powder in the collection section 15 is charged with a DC voltage of 1000 to 100V to deposit and collect the powder 14 on the collection plate 16.

The carrier gas oxygen gas is also discharged through the outlet 17.

(Function) In the method of the present invention, each raw material constituting the oxide-based superconducting powder 9 is dissolved in a solvent to form a solution, and then the frequency f
After atomizing with an ultrasonic vibrator of 7 to 3 MHz and classifying the particles of this atomized raw material liquid 6 into a desired particle system, the atomized raw material liquid 6 is made into an oxide-based superconducting powder.
It is possible to continuously obtain fine, uniform, and spherical oxide-based conductor particles through a relatively simple process.

In addition, in the manufacturing method of the present invention, the supplement @ 1115 is 200 to 9
Residual solvent, decomposed solvent, etc. in the oxide-based superconducting powder are removed by heating to 00°C, and the oxide-based superconducting powder is charged with a DC voltage in the collecting section 15 to remove the same powder. It becomes possible to collect.

(Example 1) Next, the present invention will be explained in more detail with reference to Examples. 1st
Oxide-based superconducting powder was manufactured by the method shown below using the apparatus shown in the figure. Starting materials include Y, Ba
and Cu nitrate i.e. Y (NO3)3 Fist 6H20
,Ba(NOs)? and Cu(NO3)2 11382
0 was collected in a molar ratio of Y:Ba:Cu=1:2:3, and mixed and dissolved in deionized water until the solution concentration was Y.
0.08 mol/l converted to Ba2Cu3O7-x
A mixed solution was used. Oxygen gas was used as the fluid transport gas, and the flow rate was 1.5 no/min.

The mixed solution of each of the raw materials is atomized by an atomizer 3 made of an ultrasonic vibrator with a frequency of 1.7 MHz, and large droplets of 10 m or more are aggregated and collected by a particle classifier 5, and particles with a particle size of less than 10 μm are collected. Only the droplets were transferred to the heating furnace 7 heated to 1000°C. Next, the oxide-based superconducting powder oxidized in the heating furnace 7 is introduced together with the residual solvent and the decomposed solvent therein into the collecting section 15 heated and maintained at a heating temperature of 700° C. to remove the solvent. Further, the oxide-based superconducting powder was charged with a DC voltage of 5 KV in the collecting section 15, and the powder was collected by the collecting plate 16 at #Ma.

When the polar shape of the obtained powder was observed using an operating electron microscope, it was found to be a fine spherical powder with an average particle size of 0.84 m. Moreover, the particle size was also uniform.

The x11 diffraction results of the superconducting powder are shown in Figure 2, and YBazCu30z with a perovskite structure.
A sharp peak of −x was observed, no heterophase (for example, Y2 BaCu0s-x, etc.) separate from the perovskite structure was observed, and only a small amount of impurities such as a single phase (CuO in this example) was observed.

Furthermore, when the Meissner effect and superconducting properties of the superconducting powder were measured, the Meissner effect was observed, the critical temperature (Tc) was 90'K, and the critical current density (
A value of 600 A/c 2 was obtained as JC), and it was found that the powder had superconducting properties almost equivalent to those of the oxide-based superconducting powder produced by the conventional method.

(Example 2) In the method of Example 1, the heating temperature of the collecting section 15 was set to 20
The oxide-based superconducting powder was collected while maintaining the temperature at 0°C. The SEM and X-ray diffraction results and superconducting properties of this superconducting powder were almost the same as in Example 1.

(Example 3) In the method of Example 1, Y and B were used as starting materials.
a and Cu flukoxide (e.g. ethoxide) as Y:
Weighed so that the molar ratio of Ba:Cu was 1:2:3,
These are dissolved in completely dehydrated ethanol, and the solution concentration is o, ooesoL/
A mixed solution having the following properties was used. When this mixed solution was atomized by the method shown in Example 1 to produce oxide-based superconducting powder, fine oxide-based superconducting powder having the same characteristics as in Example 1 was obtained. .

(Effect of the invention) The manufacturing method of the present invention has the following effects.

(1) Fine, spherical oxide superconducting powder can be produced in a relatively simple process, and this powder can be used to obtain a dense superconducting molded body with excellent superconducting properties.

(2) Solvents such as nitrate radicals, which have been difficult to remove, are also removed, and oxide-based superconducting powder can be collected efficiently.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of an apparatus used for carrying out the present invention, and FIG. 2 is a chart diagram showing an example of the results of X-ray diffraction of the oxide superconducting powder. 1 is a flow rate controller 2 is a solution-formed oxide superconductor raw material 3 is an atomizer 4 is an atomized raw material 5 is a particle classifier 6 is a mist raw material 7 is a heating furnace 8 is a temperature control sensor 9 is an oxide-based superconducting powder Figure 1

Claims (1)

[Scope of Claims] In producing an oxide-based superconducting powder consisting of an alkaline earth metal, a rare earth element, copper, and oxygen, (A) each raw material constituting the oxide-based superconducting powder is dissolved in a solvent to form a solution. After that, these are mixed to the desired composition ratio,
After making a uniform mixed solution, the mixed solution is heated to a frequency of 0.7 to
A process of atomizing with a 3 MHz ultrasonic vibrator, classifying particles of this atomized raw material liquid into desired particle sizes, and transporting the same,
(B) a step of thermally decomposing the atomized raw material liquid at 700 to 1100°C in an oxygen atmosphere having an oxygen partial pressure of 0.2 atm or more to obtain an oxide-based superconducting powder; (C) the step of B. The obtained oxide-based superconducting powder was heated at 200°C to 9°C with a solvent.
The oxide-based superconducting powder in the collecting part is introduced into the collecting part heated and maintained at 00°C to remove the solvent, and the oxide-based superconducting powder in the collecting part is
1. A method for producing oxide-based superconducting powder, characterized in that it is produced through a step of charging and collecting with a DC voltage of 000V.