JPH03140472A - Production of built-up film of oxide fine particle - Google Patents

Abstract

PURPOSE:To form a dense thick film or a linear built-up film of a superconductor by spraying and pyrolyzing a soln. contg. necessary constitutional elements to synthesize fine particles for crystallizing the superconductor and spraying the fine particles on a base plate at high velocity and forming the dense built-up film on the base plate. CONSTITUTION:A metallic salt soln. or an organic acid soln. which contains the respective constitutional elements of Ba, Y and Cu for a Y-based superconductor or of Bi, Pb, Sr, Ca and Cu for a Bi-based superconductor is sprayed with a soln. atomizer 1 and spray pyrolyzed. The fine particles crystallized as the superconductor are directly synthesized. These fine particles being an aerosol state are sprayed on a base plate 7 from a nozzle 6 at high velocity by utilizing the pressure difference due to decompression or pressurization. A dense built-up film is formed on the room-temp. or heated base plate 7 by utilizing the inertia force of the fine particles. Thereby practical utilization of the superconductive material as the thick film or a wire rod is promoted.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to a method for producing a thick film, a linear deposited film, or a green compact of an oxide high temperature superconductor.

"Prior art and its disadvantages" Conventionally, methods for forming oxide high-temperature superconductors include (1)
Sputtering method, (2) evaporation method, (3) ion beam method, (4) CVD method, (5) spray pyrolysis method, (6) coated film pyrolysis method, (7) screen printing method, etc. are known. ing.

Among these, (1) to (4) are being researched as thin film production methods, and the secondary high-performance thin films (micron order or less) are produced at relatively low temperatures (minimum of about 500°C).
It has become possible to fabricate them on different substrates. However, these are designed with practical use in electronic devices in mind, and the allowable current amount is small. In order to apply Mi electric W bodies to fields where relatively large amounts of current flow in the form of wires or tape materials, or to provide shapes such as magnetic shields, it is necessary to make them into bulk bodies, or to use thick films or wires. It is necessary to produce a deposited film with a similar shape. Methods (4) to (7) are currently being researched as methods for producing thick films. The CVD method (4) uses a metal chloride and an organometallic gas as raw materials, and deposits a superconductor on a heated substrate by a gas phase reaction. The MOCVD method using organometallic gas has high expectations for not only thin films but also thick films due to advances in high-speed deposition technology, but there are problems with raw material gas control technology and cost. In the spray pyrolysis method (5), a metal salt solution is sprayed onto a substrate heated to about 400 to 500°C, this is repeated several times to deposit a precursor, which is then thermally decomposed and crystallized at a higher temperature. Although it is a thick film and can be formed relatively easily, there are problems in controlling the homogeneity and composition of the film. (6)
The coated film pyrolysis method is similar to the spray pyrolysis method, but a solution of naphthenic acid, metal alkoxide, etc. is applied to the substrate surface by dipping or the like, and then baked.

Similar to (5), there are many problems such as the problem of compositional homogeneity, the tendency for cracks to occur in the film, and the influence of residual carbon, and only a low critical current density has been obtained. In addition, all of these methods require a process to maintain the substrate temperature at a high temperature of 800°C to 900°C during film formation or as a boss annealing, which may cause reactions with the substrate or deterioration of substrate quality due to high temperatures. This has become a problem.

"Summary of the Invention" The present invention solves these drawbacks and provides a film forming method that can produce a dense thick film of Mi conductor and improve the film quality without heating the substrate or under low-temperature heating conditions. The aim is to commercialize oxide high-temperature superconductors as thick films.

In the process of researching methods for synthesizing ultrafine particles of oxide high-temperature superconductors, the present inventors decided to use spray pyrolysis to directly synthesize ultrafine particles that already exhibit superconducting properties in the aerosol state after thermal decomposition. This was a success, and we thought that this feature might be effective for film formation at room temperature or low-temperature heating conditions, and as a result of repeated studies, we arrived at the present invention.

The present invention will be explained in detail below.

The present invention has two configurations: (a) synthesis of superconductor ultrafine particles by spray pyrolysis; (b) film formation by in-situ deposition of the ultrafine particles synthesized in (a) by aerosol impact deposition. Consists of elements.

(Figure 1). First, (a) will be explained. We synthesize ultrafine particles of superconductors using spray pyrolysis. This is document 1
As described in detail in 2007, a residue of nitrate, etc., prepared to have the composition of a superconductor is made into minute droplets using an atomizer, and these are placed in a reaction zone under predetermined temperature, atmosphere, and flow conditions. Drying, thermal decomposition, and crystallization occur within an extremely short period of time (about a few seconds in the case of yttrium) to obtain ultrafine superconductor particles.

The superconducting properties of the produced superconductor are greatly influenced by the production conditions. For example, in the case of yttrium-based superconductors, 980
When the reaction is carried out at a temperature of ~1000°C using oxygen as a carrier gas at a flow rate of 0.7 to 0.8 liters per minute, the resulting fine particles have good crystallinity as determined by X-ray diffraction. is confirmed, and superconducting properties are confirmed by the temperature-magnetization characteristics in the state obtained as an aerosol (without subsequent heat treatment at high temperature) (Figure 2).

Next, (b) is the formation of a fine particle deposited film by the aerosol collision deposition method. This concept was proposed by Kashu et al. As a method of forming a dense film by spraying,
It is called the gas deposition method. In general, high-purity ultrafine metal particles have been problematic in that they are prone to oxidation and agglomeration during transition from generation to the next process, but film formation is now possible using differential pumping from a high-vacuum ultrafine particle generation chamber. Ultrafine particles are sent into a chamber in a suspended state, ejected from a nozzle at high speeds similar to the speed of sound, and are tightly deposited on a substrate using a strong force using the inertia of the particles. Therefore, in the case of ultrafine metal particles, it is possible to handle them while keeping the surface clean, which is effective in producing dense films. Kashu et al. also developed superconductors for yttrium-based superconductors by producing ultrafine metal particles of Y, Ba, and Cu to form a dense film using the method described above, and then heating the substrate to 850°C in oxygen. Although the film is being fabricated, it is not a superconductor at the stage of fine particle deposition, and requires crystallization and oxidation processes by heating at high temperatures.

Therefore, as a result of repeated studies considering the possibility of forming a film using a similar method using microparticles that have already been crystallized into the desired crystalline phase, the inventors of the present invention found that the crystals already formed in (a) can be used as a superconductor. By using ultrafine particles that have been completely processed, it has become possible to obtain a dense superconductor film that is already deposited on a substrate (FIGS. 3 and 4). The method for depositing particles is to transport the particles in an aerosol state from the particulate collection section in the final process of the system in (a) to a decompression chamber (several to 500 Torr or less) while controlling the pressure by differential pumping, and then to the nozzle. (Tip diameter 0.2~3m
0.0 m) from the nozzle tip using a differential pressure.
A method was adopted in which the material was deposited on a substrate placed at a distance of about 5 to 5 mm.

It should be noted that during the fine particle transport process, fine particles may adhere to the wall surface by one inch due to thermal deposition, and in that case, it is necessary to heat the transport pipe to about 100 to 200°C. In addition, the pressure difference between the process (a) and the process (b) is determined by the carrier gas flow rate in (a) and (IJ
) It is necessary to control the conditions to the optimum depending on the film formation state.

Further, by driving or rotating the substrate in one direction or in a plane direction using a low-speed motor, a superconductor can be obtained as a linear or film-like deposit. The film thickness can be easily controlled by the amount of particles fed per shell and the driving speed of the substrate.

This method eliminates the need for post-treatment heating of the substrate, but in order to improve the superconducting properties of the deposited film, it is necessary to heat the substrate to about 400-500'C to increase the bonding properties between crystal grains. There is.

(Reference 1) M, Awano et, aM Che
+n1stry Letters, 43 (1989) (Reference 2) Seibu Kashu: Metal, January 1989 issue P, 5
7 "Example" Next, the present invention will be described with reference to Examples.

(Example 1) A superconductor fine particle film was formed on an yttrium-based superconductor by the following method.

First, yttrium, barium, and copper have an atomic ratio of I:
A nitrate solution with a ratio of 2:3 was prepared. The solution concentration was 0.05 mol/I.

Reaction zone temperature 990°C, carrier gas flow rate 0 oxygen
．． 71 per minute and 1 spray pyrolysis. The obtained superconductor fine particles were transported to a vacuum chamber with a diameter of 0.5 m.
A film was formed on an MgO single crystal substrate using a nozzle of m. The board is 2
It was linearly driven at a speed of 0 mm/hour. The obtained film was a dense thick film with a density of 90% or more according to cross-sectional observation, and the average film thickness was 0.
．． It was 6 mm. By annealing in oxygen at 500° C. for 48 hours, superconducting properties of Tc=80r were exhibited.

(Example 2) A superconductor fine particle film was formed using the following method for a bismuth-based superconductor.

First, a nitrate solution α in which bismuth, lead, strontium, calcium, and copper were prepared in a ratio of 2:0.1:2:1.2:2.3 was prepared. Melt? α; Agricultural degree was 0.03 mol/I. Reaction zone temperature 750℃,
The carrier gas flow rate was 0.51 argon per minute, and spray pyrolysis was performed. The obtained superconductor (low Tc phase) fine particles were generally transported to a reduced pressure chamber and formed into a film on a zirconia polycrystalline substrate using a nozzle with a diameter of 1 mm. The board is 2On+m
It was linearly driven in the X direction at a speed of @ hours and in the X direction at a speed of 100 mm per minute. The obtained film was a dense thick film with a density of 90% or more as determined by cross-sectional observation, and the average film thickness was 0.2+nm. It showed superconducting properties of Tc=65I.

``Effects of the Invention'' As explained above, the present invention makes it possible to form a dense thick film or linear deposited film of a superconductor on a substrate under lower temperature conditions than in the conventional film formation method. This is expected to promote the practical application of superconducting materials as thick films or wires (wiring) by increasing the critical current density due to rough improvements in film quality.

Figure 1

[Brief explanation of the drawing]

FIG. 1 shows a diagram of the apparatus configuration of this method. FIG. 2 shows a transmission electron microscope image of the particle structure of ultrafine yttrium-based superconductor particles synthesized by the spray pyrolysis method. FIG. 3 shows a photograph of the film structure of the superconductor produced according to the present invention, taken as a scanning electron microscope image of a cross section of a linear deposited film. FIG. 4 shows the X-ray diffraction pattern of the yttrium-based superconducting film. In the figure, (000) represents a plane index corresponding to each diffraction peak of the superconducting phase, and YSZ represents a peak originating from the substrate. 2: Carrier gas inlet 3: Reaction zone 4: Pressure rA! ! Valve 6: Vacuum chamber 6: Nozzle 7 2 Substrates 8: X-Y and rotary drive unit 75 Vacuum pump Fig. 3 Fig. 2 VA 0.1jt, sn 1, Me. , Indication of the case 1999 Patent Application No. 281090 2 Title of the invention Method for manufacturing oxide fine particle deposited film 3 Person making the amendment Relationship to the case Patent applicant address 1-3-1 Kasumigaseki, Chiyoda-ku, Tokyo (11
4) Name Director of the Agency of Industrial Science and Technology Ken Sugiura 4, Designated Agent 0 θ 0 (0) 0 0 February 13, 1990 (shipment date 2 February 27, 1990) 6
, Number of claims increased due to amendment 07, By subject of amendment ■ ■ ■ Insert "ni" next to "on the board" in the third line of the third page of the paper specification. Delete "ni" from line 10 on page 7 of the statement. On page 11, line 12 of the specification, "This is a photograph of the membrane structure obtained by scanning electron microscopy." is corrected to "This is an AT mirror photograph showing the particle structure."

Claims (1)

[Claims] For yttrium-based superconductors, a metal salt solution or organic acid solution containing constituent elements of barium, yttrium, and copper, and for bismuth-based superconductors, bismuth, lead, strontium, calcium, and copper, is spray pyrolyzed. By directly synthesizing crystallized fine particles as a superconductor, the fine particles in an aerosol state are sprayed onto a substrate at high speed using the pressure difference caused by reduced or increased pressure, and the inertial force of the fine particles is used to create a dense deposit. A method in which films are prepared at room temperature or on heated substrates.