JPH03153502A - Formation of superconducting thin film - Google Patents

Abstract

PURPOSE:To form the thin film on a large-area substrate by bringing a pulverized superconducting material into a colloidal dispersion with the aid of a surfactant, electrolytically oxidizing the solubilized micelle and depositing the superconducting material on an electrode. CONSTITUTION:The superconductor material is pulverized so that the average diameter of the primary grains is controlled to <=5mum. The obtained fine grains are dispersed in an aq. soln. of the surfactant having a metallocene group by agitation, the dispersion is centrifugally separated to remove the large-diameter grains, and the supernatant liq. is obtained. The electrode is dipped in the supernatant liq., electrolytic oxidation is carried out at an electrolytic potential >=0.1-0.2V higher than the oxidation potential of the surfactant, and a superconductor thin film is deposited on the electrode.

Description

[Detailed Description of the Invention] [Industrial Application Field 1] The present invention relates to a method of forming a superconducting material into a thin film on an electrical conductor, and is applicable to coils, electrical wiring, thin film devices, etc. where superconducting thin films are required. It is applicable to the following fields.

[Prior Art] Since the discovery of oxide superconductors in recent years, efforts have been focused not only on the development of room-temperature oxide superconductors but also on the research and development of thinning superconductors.

In the method for producing oxide superconductors by radiation, the oxide containing the constituent elements that will serve as its precursor is thoroughly ground and mixed, and is fired after calcination and pressing steps, so superconductors of various shapes can be produced. This is because it was difficult to manufacture.

For industrial use, thinning is essential in many cases, for example, when used as wiring for an IC1 circuit board or as a structure for a thin film device.

For this reason, methods for thinning the film include sputtering, vapor deposition, C
Research and development on film thinning using dry film forming methods such as the VD method is progressing.

[Problems to be Solved by the Invention] However, in thinning the film using the above-mentioned prior art, (1) a dry film forming apparatus is used, and therefore a thin film cannot be formed on a large-area substrate.

2) Dry film forming equipment has low mass productivity, leading to increased costs.

3) As is clear from the principles of film formation such as sputtering, vapor deposition, and CVD, it is difficult to form a film with uniform physical properties within one surface.

4) Since a high temperature is required when forming a superconducting thin film, it is possible to form the film only on a highly heat-resistant substrate, and it causes thermal damage to films formed before the superconducting thin film is formed.

There were other issues.

[Means for solving the problem 1 In order to solve the above problem, micelles are electrolytically oxidized in a micelle electrolysis method in which micronized superconducting material is electrolytically deposited in a solution that is dispersed and colloidalized with a surfactant. The method is characterized in that a superconducting thin film is formed by depositing a superconducting material on the electrode.

The micelle electrolysis method is a wet method for forming films of organic pigments, etc., as described by Saji et al.
09,5881f19871. CheIIl, Le
tt 893 (198811) reported a method for electrolyzing micelles.

The superconductor used in the present invention may be any superconductor.

The present invention will be explained step by step below.

As a first step, the superconductor is sufficiently pulverized. At this time, -
The average particle size of the secondary particles is 5 μm or less, preferably 0.5 μm or less.
The diameter shall be 5 μm or less. This is because the smaller the primary particle size, the easier it is to form a dispersed colloid in the subsequent process.

As a second step, the primary particles of the superconductor are stirred and dispersed in an aqueous solution containing a surfactant and a supporting electrolyte.

The surfactant used in the electrolysis of the micelles of the present invention is electrochemically oxidized to be positively charged, and the positive electrode and the positively charged surfactant repel each other, causing collapse of the micelles and solubilization. It has the property of depositing superconductor particles on the positive electrode. Some such surfactants have metallocene groups.For example, a commercially available product is ferrocenyl-PEG (manufactured by Dojindo Chemical).
There is.

The concentration of the surfactant must exceed at least the critical micelle concentration, and is determined by the type of surfactant and the amount of superconductor particles added.

In the third step, an electrode is immersed in this dispersed colloidal solution and electrolysis is performed.The electrolytic potential differs depending on the type of surfactant, but is higher than the oxidation potential of the surfactant, preferably 0.
．． It is desirable to increase the potential by 1 to 0.2 V or more and perform the reaction-diffusion rate-determining potential, because this allows the highest film-forming rate and stabilizes the rate.

Examples will be described below.

[Example 1j As superconductors, Yx Os, Bag Cot.

A mixture of CuO with an elemental ratio of Y, Ba, and Cu of 1:2:3 was thoroughly ground and mixed, and 88
After rising to 0°C, it was held for 10 hours, lowered to 300°C in 6 hours, then lowered to room temperature in 3 hours, and thoroughly pulverized. This process was repeated three times to produce a pre-sintered powder. This calcined powder was raised to 940°C in 3 hours, held for 6 hours, lowered to 450°C in 6 hours, held for 4 hours, and then lowered to Tomitaki in 3 hours.The powder was further finely ground to reduce the average particle size. It was set to 0.5 μm.

After confirming that the fine particles were a superconductor having a structure of Y+ Bat Cut 0t-x, they were dispersed and made into colloids.

The dispersed colloid liquid had the following composition.

This aqueous solution was subjected to ultrasonic stirring for 2 hours to suspend electromotive conductor particles in the liquid.

Next, this suspension was centrifuged to sediment particles with large diameters, and a supernatant liquid was collected.

A platinum plate was immersed in the above-mentioned supernatant liquid, with glass with ITO used as a positive electrode and a negative electrode, and a saturated calomel electrode was further immersed as a reference electrode, and electrolysis was performed on the reference electrode at +0.5 V for 1 hour.

Through these operations, a uniform superconductor film (3000 mm thick) was obtained on the ITO.

[Example 2] A calcined powder was prepared in the same manner as in Example 1, and this was made into fine particles to have an average particle size of 0.4 μm.

A 6-dispersed colloidal solution obtained by dispersing and colloidizing these fine particles had the following composition.

Next, as a positive electrode, alumina ceramics (manufactured by Kyocera) was surface roughened using an abrasive and an ultrasonic generator.
The material used had been chemically etched and electroless silver plated.

The composition and conditions of electroless silver plating are as follows: A silver plating film with a thickness of 300 mm was formed.

As in Example 1, this positive electrode, a platinum negative electrode, and a saturated calomel electrode were immersed in the dispersed colloid liquid and electrolyzed at +0.5 V for 1 hour using the reference electrode. Through these operations, a pre-fired powder with a film thickness of 3000 mm was formed on the positive electrode.

This positive electrode was subjected to main firing under the same conditions as in Example 1.

As a result, the film of the calcined powder is Y+ BagCusOy−
It became a positive superconductor, and when its electrical resistance was investigated using the four-terminal method, the electrical resistance began to decrease at about 93, and completely became 0 at about 83. In addition, the adhesion of the film was measured in Example 1.
was higher than in the case of

[Effects of the Invention] As can be seen from the examples above, the use of the present invention is a feature of the wet coating method.

1) Formation of thin films on large-area substrates 2) High mass productivity 3) Formation of films with uniform in-plane physical properties has become possible even in superconducting thin films. In addition, Example 1
By forming a thin film using the method described above, it has become possible to form a film without thermal damage to the substrate and the films formed before the superconductor film is formed.

that's all

Claims (2)

[Claims] (1) The superconducting material is deposited on the electrode by electrolytically oxidizing the micelles in the micelle electrolysis method, in which micronized superconducting material is electrolytically deposited in a solution made by dispersing and colloidizing it with a surfactant and making it solubilized. Characteristic method for forming superconducting thin films. (2) The method for forming a superconducting thin film according to claim 1, characterized in that the precursor thin film is made superconducting by forming a precursor thin film on an electrode using a micronized precursor of a superconducting material and then baking the precursor thin film. .