JPH077192A - Formation of laminate of fine oxide particle - Google Patents

Abstract

PURPOSE:To allow formation of a laminate in which fine particle layers having different compositions are deposited sequentially by controlling the supply quantity of fine particles produced through thermal spray decomposition. CONSTITUTION:A solution of nitrate, for example, conditioned to have the composition of superconductor is fed through an atomizer to produce fine droplets which are reacted under specified conditions of temperature, atmosphere, and flow rate thus obtaining fine particles of superconductor. Fine particles synthesized at two thermal spray decomposition reaction sections are fed alternately to a capturing section where a laminate is produced. Each reaction section is provided with a solenoid valve, for example, and one valve is opened whereas the other valve is closed. At first, the fine particles are fed through the open valve to the capturing section and deposited on a filter. Upon elapse of a predetermined time, the valve is switched to deposit fine particles on the first fine particle layer. The operation is repeated to form a laminate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thick film / deposited film / graded laminated film of an oxide high temperature superconductor.

[0002]

The film formation method of a conventional ceramic multilayer film, ₍₁₎ powder graded composition filling method, ₍₂₎ particle injection sequence method, ₍
3) PVD method, CVD method and the like are known.

The method ₍ 1) is a method of stacking powders one by one in a mold, which can be easily carried out, but the width of the composition step is limited and fine control is difficult. Further, there is a problem that peeling or cracking is likely to occur in the discontinuous portion of the composition.

The method ₍ 2) is a method of depositing several kinds of suspensions having different ratios of mixed powders on a substrate with a spray nozzle so as to have a predetermined composition. In this case, there are problems of stable powder supply and restrictions on shape-imparting property and stacking area.

The PVD method (physical vapor deposition method) of ₍ 3) is a method of depositing a metal evaporated by heating on a substrate, and the CVD method (chemical vapor deposition method) is a gas phase reaction using a metal salt / organic metal gas as a raw material. By the method of precipitating the target fine particles on the base,
In each case, an attempt has been made to produce a laminated film by gradually changing the composition of raw materials supplied to the gas phase reaction. However, these methods have problems of reaction stabilization and reproducibility, low deposition rate, and cost.

[Problems to be Solved by the Invention] The present invention solves the drawbacks of the above method and provides a high temperature oxide superconducting method as a film forming method which enables uniform and fine control of the composition step width of a superconductor. It is intended for practical use as a thick film / deposited film / graded laminated film of the body.

[Means for Solving the Problems] In the present inventors, in the synthesis of ultrafine particles of an oxide high-temperature superconductor by a spray pyrolysis method, the ultrafine particles that already exhibit superconducting properties in an aerosol state after pyrolysis are comparatively produced. We paid attention to the fact that it can be directly synthesized easily. According to this method, the composition of the solution can be adjusted to synthesize the superconductor precursor fine particles and other fine particles having a partial composition of the superconductor.

By utilizing this feature and controlling the supply amount of the fine particles in the aerosol state with a valve or the like, it was thought that a relatively high-speed laminated film formation in which the composition step width was uniformly and finely controlled could be performed. It may also be possible to heat-treat the laminated film and cause the crystal grains to be oriented by the interaction of the respective layers by utilizing the solid phase diffusion reaction, thereby making it possible to produce a superconductor thick film having an anisotropic fine structure. As a result of repeated studies from the above viewpoints, the present invention has been achieved.

The present invention will be described in detail below. The present invention is ₍ 1) synthesis of two kinds of fine particles such as superconductor fine particles or precursor fine particles thereof / metal fine particles other than superconducting particles by a spray pyrolysis method, ₍ 2) control of flow of multi-component fine particles by a solenoid valve, etc. And film formation by filter-trap,
(Fig. 1).

In ₍ 1), a solution of nitrate or the like prepared so as to have a composition of a superconductor is made into fine droplets by an atomizing device, and this is made extremely small in a reaction zone under predetermined temperature, atmosphere and flow rate conditions. Drying-reaction-crystallization is caused within a short time to obtain superconductor fine particles. In the case of the superconductor precursor and other fine particles, a solution according to their composition is used.

In ₍ 2), each of the synthesized fine particles is alternately supplied to the collection section to form a laminated film. That is, as shown in FIG. 1, two spray pyrolysis reaction sections are provided with, for example, solenoid valves,
Open one valve and close the other. First, the open particles are sent to the collecting part and deposited on the filter. After a certain period of time, the valve is switched to stack the next fine particles on the first fine particle layer. By repeating this operation, a laminated film is formed.

The thickness of each layer to be laminated depends on the opening time of the solenoid valve and the size of the produced fine particles, and is from sub-μm to several ¹⁰ μm.
m is controllable.

[0013]

Example 1 A superconductor-silver laminated film was prepared for an yttrium-based superconductor. First, a nitrate solution was prepared in which the atomic ratio of yttrium, barium, and copper was ₁ ^: 2: 3. The solution concentration was 0. 03 ^m ol _{/ l.} Reaction zone temperature 7 00
The spray pyrolysis was carried out at 0 ° C. and the carrier gas flow rate was _{1 l /} min of oxygen. The obtained superconductor fine particles are filtered at the collecting part.
Deposited on top.

[0014] of silver switching the solenoid valve after a certain period of time ^0. 2 ^m ol
_{/ l} nitrate solution and the reaction zone - emission temperature ₆ ⁰ 0 ° C., to decompose evaporative a carrier gas flow of oxygen _1l per minute, laminating on the resulting silver particles previously deposited superconductor layer. The switching time of the solenoid valve was 1 hour. The cross-sectional observation of the obtained laminated film revealed that the superconducting layer was about ³⁰ μm thick and the silver layer was about ₅ μm.

It was found that by sintering the produced superconductor-silver laminated film, grain orientation parallel to the laminating interface occurs and the superconducting critical current characteristics are improved.

Example 2 With respect to a bismuth superconductor, a thick film having an anisotropic fine structure was produced. First, a nitrate solution was prepared in which the atomic ratio of bismuth and lead was ₂ ^: 1. Solution concentration
It was 0.0 ₇ ^m ol _{/ l.} The reaction zone - emission temperature ₆ ⁰ 0 ° C., carrier gas flow rate was spray pyrolysis as oxygen _1l per minute. The obtained superconductor precursor ₍ a ₎ fine particles were deposited on the filter in the collection part.

The switching solenoid valve after a predetermined time, strontium, calcium, copper _2: ^1: 2 become thus prepared solution concentration 0.0 ₇ ^m ol _{/ l} nitrate solution and the reaction zone - emission temperature ₆ ⁰ 0
C., spray pyrolysis at a carrier gas flow rate of oxygen of _{1 l /} min, and the obtained superconductor precursor ₍ b ₎ fine particles are laminated on the superconductor precursor ₍ a ₎ layer previously deposited. The switching time of the solenoid valve was ³⁰ minutes.

The cross-section of the obtained laminated film was a uniform laminated film having a superconductor precursor ₍ a ₎ layer of about ¹⁰ μm and a ₍ b ₎ layer of about ²⁰ μm (FIG. 2). By sintering this, grain growth occurred in the direction perpendicular to the stacking interface, and the crystal grains could be oriented.

[0019]

INDUSTRIAL APPLICABILITY As described above, the present invention enables stacked film formation in which the composition step width is uniformly and finely controlled as compared with other stacked film formation methods, and the critical current is improved by improving the film quality. The increase in density is expected to promote the practical application of superconducting materials such as thick films.

[Brief description of drawings]

FIG. 1 shows an apparatus configuration diagram of this method.

FIG. 2 shows an electron micrograph of a bismuth-based superconductor precursor ₍ a ₎ - ₍ b ₎ laminated film produced by the present method, instead of the drawing.

Claims (1)

[Claims] A yttrium-based / bismuth-based superconductor fine particle, a superconductor precursor fine particle, or a metal fine particle other than a superconductor is directly synthesized by a spray pyrolysis method, and the supply amount of these fine particles in an aerosol state is controlled to be different. A method for producing a laminated film in which a fine particle layer having a composition is sequentially deposited.