JPH03279212A - Production of target material for forming oxide superconducting thin film - Google Patents

Abstract

PURPOSE:To inhibit formation of cracks by interposing oxide or carbonate powder other than Cu in constituent metallic elements of an oxide superconductor as a mold release agent between a carbon mold and raw material powder. CONSTITUTION:Y2O3 powder, BaCO3 powder and CuO powder are mixed at a prescribed molar ratio and the resultant mixture is calcined and then pulverized to prepare an RE-Ba-Cu-O-based oxide superconductor powder (RE is rare earth element) such as YBa2Cu3O7-delta. On the other hand, oxide or carbonate powder of an element such as Y2O3 powder other than Cu is kneaded with an aqueous solution of an acrylic acid ester copolymer, etc., to produce a slurry, which is subsequently applied to the contact surface of a carbon mold with a sample to a prescribed thickness and dried. The prepared oxide superconductor powder is then filled in the carbon mold, pressurized and heated to afford a target material for forming an oxide superconducting thin film without fixing to the carbon mold and forming cracks.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is directed to the production of a target material used when forming a copper-containing oxide superconducting thin film such as a Y-Ba-Cu-0 system by a sputtering method. Regarding the method.

(Prior Art) CVD methods, laser beam evaporation methods, reactive evaporation methods, sputtering methods, and the like are used to form oxide superconducting thin films. Among these methods, the sputtering method enables the formation of a large area, and therefore efforts are being made to establish a method for forming the same.

In this sputtering method, a target material is irradiated with ions or the like to knock out atoms or molecules constituting the target material to form a thin film on a predetermined substrate. When obtaining a thin film made of multiple oxides like the above-mentioned oxide superconductor, for example, a sintered body having the same composition as the thin film to be obtained is used as the target material, or a correction target is used in addition to the above target. set up,
A method is generally used in which the target is formed while controlling the amount of atoms or molecules generated from the target.

Conventionally, this type of target material has been produced by calcining and pulverizing powders of oxides of hexoxide superconductor constituent elements or oxide-forming compounds such as carbonates and nitrates as desired, followed by hot press firing or ordinary firing. The method is adopted.

(Problem to be solved by the invention) The characteristics required of such a target include high density itself (relative density of about 60% or more to the theoretical density) in order to increase the film formation rate, and dimensions. Since it is required to be able to produce products with the same shape, hot press firing is particularly used.

However, when firing at high temperatures in a hot press using a carbon mold, if copper or copper oxides are present in the sample, they will be reduced by the presence of carbon, causing the fatal problem that the sample will stick to the carbon mold. there were. Therefore, in order to avoid this sticking, it is considered to lower the firing temperature, but since the density of the sintered body decreases and the strength of the target itself decreases, there is a risk that cracks may occur during bonding with the support.

It is also possible to use a mold made of alumina, silicon carbide, etc., which is difficult to stick, instead of a carbon mold, but since the components of the mold will diffuse and mix into the sintered body, it will be difficult to obtain a good result if this is used as a target. It has a negative effect on the film.

(Object of the Invention) The present invention solves the above-mentioned problems, and provides a method for producing a target material for a superconductor thin film that prevents adhesion to a carbon mold and has high density and excellent dimensional stability. It is in.

(Means for solving the problems) As a result of repeated studies on the above problems, the inventors have found that
Sintering is achieved by interposing an oxide or oxide-forming compound powder of an element other than copper among the oxide superconductor-forming elements between the copper-containing sample powder and the carbon mold during hot press firing. There is no adhesion of the body to the carbon mold, and there is no contamination of impurities into the target material.
It was discovered that high-density targets can be stably manufactured because high-temperature firing is possible, leading to the present invention.

The target for forming an oxide superconducting thin film produced according to the present invention is mainly useful for forming RE-Ba-Cu-0-based (RE: rare earth element) oxide superconducting thin films, and therefore the oxide superconductor-forming element in the present invention refers to rare earth elements, alkaline earth elements, and copper elements.

To explain the manufacturing method of the present invention in detail, first, as a mixed powder for target formation, an oxide powder of the above-mentioned oxide superconducting thin film-forming element or a powder of carbonate, nitrate, etc. that forms an oxide by firing is obtained. Copper oxide or a combination of copper and one or more oxides of other thin film constituent elements can be used as an auxiliary target material during thin film formation. Mix in appropriate proportions.

This mixed powder is then hot-pressed directly or after being molded.

Further, it is preferable that the mixed powder is calcined and pulverized before being subjected to firing to create a powder having the same composition as the composite oxide sintered body to be obtained.

Next, hot press firing of the present invention will be explained with reference to FIG. In the figure, 1 is a die, 2 is a press punch, 3
is a sample, and die 1 and press punch 2 are carbon molds. According to the present invention, during firing, an oxide or carbonate of another element other than copper among the constituent elements of the oxide superconductor is used as a mold release material 4 between the die 1 and the powder sample 3 and the punch 2 and the sample 3. Fired with the help of Specifically, prior to firing, the above powder may be applied to the surface of each carbon mold to a thickness of about 0.1 to 1 mm using a brush, roller, or the like.

For example, when creating a target with a Y-Ba-Cu-○ composition or a Ba-Cu-○ composition, use Y2O3 or BaC0z powder as a mold release material, and
Hot press firing may be performed at a temperature of 0°C.

According to the above method, when the sintered body and the carbon mold are baked without using any mold release material in the conventional method, the sintered body and the carbon mold stick together and can hardly be taken out, whereas according to the above method of the present invention, the carbon mold There is hardly any adhesion to the sintered body, and although some mold release material adheres to the surface of the sintered body, it can be easily removed by light polishing.

The present invention will be explained in detail below.

(Example 1) CuO powder and BaC0z powder were weighed and mixed so that the molar ratio was 1=1, and then calcined and crushed in the air at 900°C for 5 hours, and then calcined again under the same conditions. It was pulverized with a jet mill to obtain BaCu○3 powder with an average particle size of 3 μm.

On the other hand, 10 g of Ba CO3 powder was placed in a mortar, and 5 cc of a 4% aqueous solution of an acrylic acid ester copolymer was added and kneaded to prepare a uniform slurry.

The obtained slurry was applied to a sample contacting surface of a carbon mold having a diameter of 105 mm to a thickness of 0.2 mm and dried.

The previously prepared BaCuO3 calcined powder was filled into the carbon mold described above, a pressure of 50 kg/cm2 was applied, and the temperature was raised by induction heating at a temperature increase rate of 20 °C/min to 400 °C.
After hot press firing at C for 20 minutes, the sintered body was cooled to room temperature and taken out from the carbon mold.

As a result, a BaCuO3 sintered body with a theoretical density ratio of 83% was obtained without any adhesion between the carbon mold and the sintered body or cracks in the sintered body.

Furthermore, although BaCuO3, a mold release agent, was attached to the surface of the sintered body, it could be easily removed by lightly polishing the surface.

(Comparative Example 1) Firing was performed in exactly the same manner as in Example 1 except that no mold release material was applied. As a result, the sintered body was firmly attached to the carbon mold and could not be taken out.

(Comparative Example 2) Firing was performed in the same manner as Comparative Example 1 except that the hot press firing temperature was 330°C. As a result, the sintered body was found to be solid despite the low firing temperature, and when the carbon mold was broken and the density of the sintered body was measured, it was 63%.

(Example 2) yz 03 powder, B a CO3 powder, CuO powder was 0
．． The mixture was weighed and mixed to have a molar ratio of 5:2:3, calcined in the air at 900"C for 10 hours, and then crushed. This was repeated three times to produce YBa zCu zc)t- with an average particle size of 3 gtn.
6 powder was obtained.

On the other hand, take 10 g of Y2O3 powder with an average particle size of 5 μm in a mortar, add 6 cc of a 4% concentration aqueous solution of acrylic acid ester copolymer, and 0.2 cc of ammonia water, and knead to form a uniform slurry. Created. The obtained slurry was applied to the sample contact surface of a carbon mold with a diameter of 0.
．． It was coated in a layer of 2 mm and dried.

The previously prepared YB a 2Cu 307-/powder was filled into the carbon mold, a pressure of 50 kg/cm2 was applied, and the temperature was raised by induction heating at a heating rate of 2 o''C/min.
After hot press firing at 600°C for 20 minutes, the sintered body was cooled to room temperature and taken out from the carbon mold. As a result, a YBazCuzC)ri sintered body with a theoretical density ratio of 65% was obtained without adhesion between the carbon mold and the sintered body or cracks in the sintered body.

Y2O3 powder as a mold release agent was attached to the surface of the sintered body, but it could be easily removed by lightly polishing the surface.

(Comparative Example 3) Firing was performed in exactly the same manner as in Example 2, except that no mold release material was applied and the firing temperature was set to 400°C. As a result, the sintered body was firmly attached to the carbon mold and could not be taken out. When the carbon mold was broken and the sintered body was taken out and its density was measured, it was found to be 42%.

(Effects of the Invention) As described in detail above, according to the present invention, hot-press carbon By interposing powders consisting of oxides and carbonates of elements other than copper among the constituent elements of the oxide superconductor between the mold and the sample, these powders act as a mold release agent, and the sample and carbon are bonded together. A high-density target sintered body can be obtained without sticking to the mold and without contaminating impurities.

Thereby, when an oxide conductive thin film is formed by a sputtering method, it is possible to improve the film formation rate and form a highly pure film.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram for explaining the manufacturing method of the present invention, and in the figure, 1 is a die, 2 is a punch, 3 is a sample, and 4 is a mold release material.

Claims (1)

[Claims] A method for producing a target material in which a carbon mold is filled with a sample made of an oxide powder or an oxide-forming compound powder containing at least a copper element among the metal elements constituting the oxide superconductor and then hot-press fired. A method for producing a target material for forming an oxide superconducting thin film, characterized in that an oxide or carbonate powder of an element other than copper among the metal elements constituting the superconductor is interposed between the superconducting metal elements and the powder as a mold release agent.