JPH01161619A - Manufacture of superconductor thin film - Google Patents

Abstract

PURPOSE:To efficiently form a thin film by flame-coating an oxide superconductor on a substrate via a masking plate with a cutout section to form the thin film of the oxide superconductor. CONSTITUTION:When a melted oxide superconductor 2 is sprayed from a flame coating gun 1 for flame-coating plasma to a masking plate 3, for example, part of the sprayed superconductor 2 passes a cutout section 4 in the mode specified in the pattern shape formed by the cutout section 4 of the masking plate 3 and is stuck to the surface of a substrate 5 to form a thin film 6. No superconductor 2 is stuck to the surface of the substrate corresponding to portions other than the cutout section 4 of the masking plate 3, and no thin film is formed. The thin film 6 of the oxide superconductor with the necessary pattern is easily formed on the surface of the substrate 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for producing a superconductor thin film using an oxide superconductor.

(Prior Art) In recent years, since it was announced that layered perovskite-type oxides based on Ba-La-Cu-0 may have a high critical temperature, research on oxide superconductors has been conducted in various places. ing. Among them, defective perovskite type (L
n B a2c LI*Ot-a type) (represents an oxygen defect and is usually a number of 1 or less, A is YlLa, 5cSNds
Ss, Eus Gd5DY%Hos E r 5TI
Oxide superconductors with at least one element selected from Yb and Lu, and a part of Ba can be replaced with Sr, etc.) have a critical temperature of 90°C or higher, which is higher than the boiling point of liquid nitrogen, so they are extremely difficult to use. is attracting attention as a promising material.

Therefore, when manufacturing a wiring board using such an oxide superconductor, for example, the superconductor is attached to the surface of the substrate by plasma spraying to form a thin film in a predetermined pattern on the surface of the substrate. is considered.

In this method of forming a superconductor thin film, in order to form a thin film pattern, conventionally, a masking tape is pasted on the surface of the base, leaving the part where the thin film will be formed, that is, the part where the pattern will be formed, and the thin film is not formed. A method of forming a thin film by covering the exposed surface portion of the substrate with masking tape and depositing the superconductor by thermal spraying on the exposed surface portion of the substrate is being considered.

(Problems to be Solved by the Invention) However, when forming a superconductor thin film by thermal spraying, this method of forming a pattern of the thin film using masking tape involves placing the masking tape on the surface of the substrate in a predetermined manner. It is very troublesome to attach the masking tape leaving the pattern part left on the substrate and then peel it off from the substrate after thermal spraying the superconductor, and this masking tape must be attached and peeled off each time a second substrate is thermally sprayed. The problem is that it is very inefficient because it is necessary.

The present invention has been made based on the above-mentioned circumstances, and an object of the present invention is to provide a method for manufacturing a superconductor thin film that can easily form a predetermined pattern of an oxide superconductor thin film by thermal spraying.

[Structure of the Invention (Means and Effects for Solving the Problems)] In order to achieve the above-mentioned object, the method for producing a superconductor thin film of the present invention is to apply an oxide superconductor to a substrate through a masking plate having a cutout. The oxide superconductor is thermally sprayed to form a thin film of the oxide superconductor on the surface of the substrate.

Although many oxide superconductors are known, it is practically preferable to use a perovskite-type oxide superconductor that has a high critical temperature and contains a rare earth element.

The oxide superconductor containing a rare earth element and having a perovskite structure may be any material as long as it can realize a superconducting state, such as L n B a2c uso ? -J
type (δ represents an oxygen defect and is usually a number of 1 or less, A is Y,
La s Sc s Nd 5SIISEuSGds
Defect perovskite type having oxygen defects such as DFq Hos Ers Tll5yb and at least one element selected from Lu, a part of Ba can be replaced with Sr, etc., layered perovskite type such as 5r-Ln-Cu-0 system Examples include oxides having a perovskite type in a broad sense. In addition, rare earth elements are also defined in a broad sense, and S
It shall include c s Y and La systems. In addition to the Y-Ba-Cu system, typical systems include Y and Eu.

Dys Hos Ers TI, a system in which rare earth elements such as Ybq Lu are substituted, a Sc -Ba -Cu-0 system, and a system in which Sr is further substituted with Ba5Ca.

The oxide superconductor powder that is the raw material for the superconductor thin film of the present invention is produced, for example, as shown below.

First, the constituent elements of the perovskite oxide superconductor, such as YsBa%Cu, are thoroughly mixed.

During mixing, Y2.03, Eu202, Ba0
Oxides such as sCuO can be used as raw materials. In addition to these oxides, compounds such as carbonates, nitrates, and hydroxides that are converted into oxides after firing may be used. Furthermore, a shela salt obtained by a coprecipitation method or the like may also be used. The elements constituting the perovskite oxide superconductor are basically mixed so as to have a stoichiometric composition, but there may be a slight deviation depending on the manufacturing conditions. For example, in the Y-Ba-Cu-0 system, Y I l
The standard composition is Ba 2 sol and Cu 3 sol for 1 mol, but in practice, B 2 sol and Cu 3 sol are used for Y 1 mol.
A deviation of about a2±0.6 sol s Cu 3±0.2 sol is not a problem.

After thoroughly mixing the above-mentioned raw materials, 850 to 98
Fire at a temperature of about 0°C. This firing is preferably carried out in an oxygen atmosphere so that sufficient oxygen can be supplied.

Next, the superconducting properties can be improved by heat treatment or slow cooling to a temperature of about 300° C. in an oxygen-containing atmosphere, preferably oxygen. This heat treatment is usually carried out at a temperature of about 300 to 700°C for several hours. Next, this fired product is pulverized using a ball mill, a sand grinder, or other known means. At this time, the perovskite-type oxide superconductor is split from the cleavage plane and becomes fine powder. For pulverization, the average particle size (maximum axial length on the C-plane) is about 1 to 5751, and the axial ratio (ratio of particle size to thickness) is 3.
It is preferable to do this so that it becomes about .about.5. Note that, if necessary, the pulverized powder may be classified and used so as to fall within the above range.

The oxide superconductor powder obtained in this way has oxygen defects
Oxygen-deficient perovskite type (L n B a2
cu30 ta type) (δ is usually a number of 1 or less). In addition, Ba can also be replaced with at least one kind of S r s Ca, and roughly a part of Cu can be replaced with Tt, Vs
Substitution with Cr s Mns Fes Co5N1, Zn, etc. is also possible. These substituting elements for Cu element and Ba element enter the site in a substituted form, respectively. The amount of this substitution can be set as appropriate within a range that does not reduce the superconducting properties, but too much substitution will reduce the superconducting properties, so it should be less than 801io1, and more practically 20
o1% or less.

To further explain the manufacturing method of the present invention, the manufacturing method of the present invention uses the oxide superconductor powder obtained by the above method as a raw material, and transfers this powder to a substrate through a masking plate having cutouts in a predetermined pattern. by thermal spraying and awning,
This is a method of forming a thin film with a pattern of cutouts of a masking plate on the surface of a substrate.

Thermal spraying methods for depositing the oxide superconductor powder on the substrate include plasma spraying, gas spraying, gas explosion spraying, and the like. In plasma spraying, the temperature of the plasma atmosphere is 7,000 to 20,000°C, and the velocity of particles from the nozzle of the spray gun is several hundred meters per second, so the porosity of the thin film is low and it does not adhere to the substrate. has strong adhesion.

Furthermore, since the flame does not contain oxygen, a thin film can be formed on a substrate made of a heat-resistant material such as a high-melting point metal, carbide, or nitride. For these reasons, thermal spraying is suitable as a method for forming thin films of oxide superconductors.

As the masking plate, a plate made of a metal having good heat resistance and a high heat transfer coefficient, such as copper or a copper alloy, is used. Cutouts are formed on the masking plate in a pattern that is the same as and has a corresponding size to the pattern of the thin film formed on the substrate. This cutout is formed with extremely high precision by performing processing such as laser processing on the masking plate.

The masking plate is disposed between the thermal spray gun and the substrate on which the thin film is to be formed, facing the thermal spray gun and the substrate with a gap therebetween. The distance between the thermal spray gun and the masking plate and the distance between the masking plate and the substrate are set to appropriate sizes based on conditions such as the speed and diffusion range of the superconductor sprayed from the thermal spray gun.

As a result, the masking plate except the cutout of the base body is shielded from the thermal spray gun, and the part of the base body facing the cutout is exposed to the thermal spray gun.

In addition, in the method of the present invention, the material of the substrate on which the thin film is formed is not limited to metals in general, ceramics, etc., and can be freely selected depending on the use of the substrate.

Therefore, when spraying an oxide superconductor onto a substrate, the surface of the substrate must be coated at a temperature of, for example, 10. Finish it below. If necessary, roughen the surface by blasting, etc. Also,
During thermal spraying, the oxide superconductor powder has a particle size of 50 to 6
0. Keep it aligned.

This is because if the particle size of the oxide superconductor is uneven or larger than the above range, the superconductor will not completely melt during thermal spraying, and it will be sprayed onto the surface of the substrate in an uneven molten state. This is because the particles adhere to each other, making it impossible to form a homogeneous thin film.

As shown in FIG.
When the superconductor 2 is injected, a part of the injected superconductor 2 passes through the cutout 4 of the masking plate 3 and collides with and adheres to the base 5, while the other part of the superconductor 2 passes through the cutout 4 of the masking plate 3. It collides with the plate surfaces other than 4 and stops, and does not reach the base 5. Here, the superconductor 2 passes through the cutout 4 and adheres to the surface of the base 5 in a form defined by the pattern formed by the cutout 4 of the masking plate 3. Therefore, the superconductor 2 adheres in the same pattern as the cutout 4 of the masking plate 3 to form a thin film 6. Further, the superconductor 2 does not adhere to the surface of the base 5 corresponding to the portion other than the cutout portion 4 of the masking plate 3, and no thin film is formed. As a result, a thin film 6 of the oxide superconductor having the required pattern is formed on the surface of the substrate 5. Note that the thickness of the thin film 6 formed by one thermal spraying process is usually about 20 mm. Therefore, thermal spraying is performed multiple times as necessary to form a thin film 6 having a certain thickness. Further, by sequentially and continuously moving the base body 5 with respect to the masking plate 3 and sequentially and continuously spraying the superconductor onto the base body 5 with the thermal spray gun 1, a thin film 6 of the superconductor 2 is formed on the base body. can be manufactured in sequence.

Therefore, in the method for producing a superconductor thin film of the present invention, all that is required is to arrange the masking plate 3 having the cutout portions 4 with the required pattern before starting the thermal spraying operation, and then the thin film is applied to one substrate. There is no need to move the masking plate 3 each time a superconductor is formed, and it is possible to spray a large number of substrates 3 continuously to form a thin film 6 of oxide superconductor. There is no need for the troublesome effort of attaching and peeling off a masking tape to the substrate 1 every time a thin film is formed on the substrate 1, and thermal spraying can be carried out efficiently.

Further, as described above, the oxide superconductor powder used for thermal spraying needs to be made into fine particles, but when this fine-grained superconductor powder is injected from a thermal spray gun, it tends to spread. For this reason, by using a masking plate 3 with a cutout 4 formed in the center, only the center portion of the superconductor 2 sprayed from the thermal spray gun and diffused passes through the cutout 4 and is attached to the base 5.

The superconductor 2 sprayed and diffused from the thermal spray gun 1 has a strong spraying force at the center and a weak spraying force at the outer periphery, so the outer periphery of the superconductor 2 is blocked by a masking plate 3, and only the central part is exposed. A thin film 6 with strong adhesive strength can be formed by adhering to the substrate 5 through the cutout 4.

The formed thin film is subjected to a predetermined heat treatment to become a conductor exhibiting excellent superconducting properties.

Products in which thin films are formed by the manufacturing method of the present invention can be widely applied to products such as wiring boards that utilize the excellent properties of thin films made of oxide superconductors, such as wiring boards.

(Example) Examples of the present invention will be described.

First, 2 tao of Ba CO3 powder each having a particle size of 1 to 51
I, Y203 powder 0. 5mol, CuO powder 3
The mols were thoroughly mixed, calcined in the air at 900°C for 48 hours, and then pulverized. This pulverized product was reacted by firing in the atmosphere at 910°C for 30 hours, and then further pulverized in a ball mill and classified to obtain an average particle size of 1.5 tlJR.

A perovskite-type oxide superconductor powder with an axial ratio of 3 was obtained.

Next, a plurality of lead thin films were formed using this superconductor powder on the surface of a stainless steel substrate through a masking plate. The plasma spraying conditions were a current of 600 A, a voltage of 45 to 50 V, and the use of argon gas and hydrogen gas. Also, the distance 15 between the thermal spray gun and the base 5 is
01m.

The masking plate was made of steel and had a cutout with a lead pattern formed in the center.

The film thickness of one thermal spraying is about 10~20. It was sealed and thermal sprayed several times to form a thin film of about 200 Is. After thermal spraying, the thin film was subjected to a prescribed heat treatment.

The thin film produced in this way adhered firmly to the substrate and exhibited excellent superconducting properties.

According to this manufacturing method, it is only necessary to place a masking plate before thermal spraying, and there is no need to handle the masking plate afterwards, so efficiency is greatly improved compared to the conventional method using masking tape.

[Effects of the Invention] As explained above, according to the method for producing a superconductor thin film of the present invention, a thin film made of an oxide superconductor can be efficiently formed by thermal spraying.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the manufacturing method of the present invention. DESCRIPTION OF SYMBOLS 1... Thermal spray gun, 2... Superconductor, 3... Masking plate, 4... Cutout part, 5... Substrate, 6... Thin film. Applicant's agent Patent attorney Takehiko Suzue Figure 1

Claims (5)

[Claims] (1) A method for producing a superconductor thin film, which comprises spraying an oxide superconductor onto a substrate through a masking plate having a cutout to form a thin film of the oxide superconductor on the surface of the substrate. (2) Thermal spraying is plasma spraying. Claim 1
A method for producing a superconductor thin film as described in . (3) The method for producing a superconductor thin film according to claim 1 or 2, wherein the oxide superconductor is a perovskite-type superconductor containing a rare earth element. (4) The oxide superconductor contains Ln element (Ln is Y, La
, Sc, Nd, Sm, Eu, Gd, Dy, Ho, Er,
At least one element selected from Tm, Yb and Lu), Ba and Cu in an atomic ratio of substantially 1:2:3. The method for producing the superconductor thin film described above. (5) The oxide superconductor is LnBa_2Cu_3O_7
5. The method for producing a superconductor thin film according to claim 4, which has an oxygen-deficient perovskite structure represented by _-_δ (δ represents an oxygen defect).