JPS63225528A - Production of superconductive compound oxide - Google Patents

Abstract

PURPOSE:To form a superconductive compound oxide to a thin film or wire and to enable to control its superconductivity at high temp., by producing a compound oxide of La, Sr and/or other metals, and Cr by the chemical vapor growth process. CONSTITUTION:A gaseous starting material consisting of at least an org. La compd. and/or a halide of La, an organometallic compd. of a metal M (at least one kind among Ca, Sr, Ba) and/or a halide of the metal M, an organocopper compd. and/or a halide of copper, contg. additionally an oxidizing agent is used as a gaseous reactant, and a compound oxide consisting primarily of a compd. expressed by the formula is formed on a substrate by the CVD process. In the formula, 0.02<x<0.20. By this method, a thin film or wire-shaped compound oxide having superconductivity at high temp. is produced easily. Moreover, the oxygen content in the compound oxide is controlled easily.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing a superconducting composite oxide. More specifically, the present invention relates to a method for producing a superconducting composite oxide using chemical vapor deposition (CVD).

(Prior art) In recent years, research has progressed on the practical application of superconductivity, which can generate a strong magnetic field without consuming almost any power, and its application to magnetic levitation trains, electric physics experiments, M)ID power generation, etc. has progressed. It has become possible. It goes without saying that the development of superconducting materials that exhibit superconducting phenomena at high critical temperatures (high critical temperatures) and research and development to increase critical current density have greatly contributed to this. Along with the development of new materials such as these, a method for manufacturing superconducting materials using chemical vapor deposition in addition to the usual solution treatment has been disclosed (
For example, Japanese Patent Publication No. 49-43812).

(Problems to be solved by the invention) Recently, (L a (1-x) S r
x) Mx) 2CuO4 complex oxide (x: 0.05~
0.10 atom%) was discovered to be a high-temperature superconductor with a critical temperature of 40 or higher
Letters (Chemistry Letters),
Pages 429-432, published January 24, (1987)
]. This superconductor is obtained by mixing lanthanum, strontium, copper oxides and/or carbonates, and firing the mixture in the same manner as in ordinary ceramic manufacturing methods.

However, unlike alloys, this material does not have malleability, and therefore, depending on the manufacturing method described above, it has the disadvantage that it cannot be made into a thin film or wire for practical use.

The inventors of the present invention have made extensive studies to solve these conventional drawbacks, and have found that by using the CVD method, it is possible to easily obtain the above-mentioned composite oxide, which is a high-temperature superconductor, in the form of a thin film or wire. They discovered that it is easy to control the amount of oxygen in a composite oxide, and thereby the properties as a high-temperature superconductor, and have arrived at the present invention.

Therefore, a first object of the present invention is to provide a method for producing a high temperature superconductor composite oxide in the form of a thin film or wire.

A second object of the present invention is to provide a method for producing a composite oxide suitable for controlling the high-temperature superconducting properties of the composite oxide.

(Means for solving the problem) The above aspects of the present invention include at least an organic lanthanum compound and/or a lanthanum halide, calcium,
A raw material gas containing an organometallic compound of at least one metal M selected from the group of strontium and barium and/or gold [a halide of M, an organocopper compound and/or a halide of copper, and an oxidizing agent] is used as a reaction gas. (L a (1-
x) Mx )2CuO4 (0.02<x<0.20)
This was achieved by a method for producing a superconducting composite oxide, which is characterized by forming a composite oxide containing as the main component.

Examples of the organic lanthanum compound used in the present invention include compounds such as cyclopentagenyl, acetylacetone, alkoxide, and phenyl. Among these, La-cyclopentagenyl compounds and La-acetylacetone compounds are preferred, and particularly La-cyclopentadienyl compounds are preferred.

As an organometallic compound of metal M selected from the group of calcium, strontium and barium.

For example, Ca-cyclopentagenyl compound, Ca-acetylacetone compound, Ca-alkoxide compound;
r-cyclopentagenyl compound, Sr-acetylacetone compound, Sr-alkoxide compound, Sr-alkyl compound; Ba-cyclopentagenyl compound% B
a-acetylacetone compound, Ba-alkoxide compound: Cu-cyclopentagenyl compound, Cu-acetylacetone compound, Cu-alkoxide compound, etc. can be mentioned. Among these, cyclopentagenyl compounds and acetylacetone compounds are particularly preferred.

As the metal M, strontium is particularly preferable from the viewpoint of raising the critical temperature.

If a small amount (at least a portion) of strontium is replaced with barium and/or calcium, the critical temperature will be lower than in the case of strontium, but it can be improved from the viewpoint of processability and cost performance of the superconductor. If workability and cost performance are important, other metals may be added as impurities.

Halogen compounds such as lanthanum, calcium, strontium, barium, copper, etc. that can be used in the present invention can be selected from among known compounds.
It is particularly preferred to use chlorine compounds and fluorine compounds.

The oxidizing agent used in the present invention is a gas at room temperature, and examples thereof include nitrogen chloride and carbon dioxide, but oxygen gas is particularly preferred from the viewpoint of ease of handling.

In the present invention, the raw material gas can be appropriately diluted with a carrier gas such as a rare gas, if necessary.

As the rare gas, argon gas is usually used from the viewpoint of cost, but of course it is not limited to this.

Furthermore, the amount of oxygen contained in the film can be adjusted by controlling the partial pressure of oxygen in the reaction gas. This allows the high-temperature superconductivity of the film to be controlled.

The chemical vapor deposition method (CVD) may be a v1ICvD method, a photo CVD method, or a plasma CVD method, but a thermal CVD method is particularly preferred in the present invention. The conditions for the thermal CVD method are a substrate temperature of 600°C to 1200°C, preferably 75°C.
The temperature is 0°C to 1100°C and the pressure inside the reaction chamber is 5 Torr.
r~760Torr, preferably 15Torr~100
Torr, and is preferably carried out with a large excess of oxygen. In particular, when the temperature is 800° C. or higher, sintering can be performed at the same time as film formation, which eliminates the need for a separate sintering process, which is preferable.On the other hand, the amount of Cu can be smaller than that of other metals.

As a method for turning the reactive gas into plasma, for example, in addition to various discharge methods such as glow discharge method using high frequency or low frequency, arc discharge method, etc., the method may be appropriately selected from known methods such as plasma jet method. The glow discharge method is particularly preferable from the viewpoints of simplicity of the apparatus and ease of controlling the plasma state. In this case, the power density is approximately 0.01W
/cm2~2 W/cm2 is preferable.

The pressure inside the reaction chamber is 0.05 Torr to 20T.

rr, preferably 0.2 Torr to 2 Torr, and the substrate temperature is 400° C. to 1200° C., but it is particularly preferable to set the temperature to 800° C. or higher, since the crystallization of the produced film will be good.

Below, the method of the present invention will be explained in more detail with reference to the drawings. Figure 1 shows an apparatus for growing a superconducting material on a substrate by the thermal CVD method. In Figure 0, symbols 1 and 3 are gas inlet ports, and lanthanum compounds and copper in sample containers 5 and 7 are shown. At the same time as heating the compound, a carrier gas is caused to flow, and these raw material gases are introduced from the gas inlet 3 into the previously evacuated reaction tube 10, and at the same time, oxygen gas is introduced as an oxidizing agent. The oxygen gas inlet may be provided independently.On the other hand, infrared rays emitted from the infrared imaging furnace 1 are concentrated on the strontium compound in the crucible 9 installed in the reaction tube to volatilize the strontium. carrier gas is introduced from gas inlet 1. In this way, the reaction gas mixed with the necessary raw material gas flows through the reaction tube and is exhausted using, for example, a turbomolecular pump and a rotary pump. The substrate 11 is an infrared image furnace 2
The reaction gas is placed in a region heated by
a (t-x)Srx)Mx)2CuO4 grows.

Regarding gas flow rate control and mixing methods, various pulps, flow meters, mixing chambers, etc. can be appropriately combined as known.

(Effects of the Invention) According to the present invention, since it can be made into a thin film or linear form from the beginning of manufacture, it is possible to put into practical use materials that exhibit high-temperature superconductivity but lack ductility or malleability and are difficult to put into practical use. This is extremely convenient. In addition, it is not only extremely easy to adjust the properties of a high-temperature superconductor simply by changing the partial pressure of oxygen, but it is also possible to virtually sinter it by keeping the substrate temperature high, making it possible to create an independent sintering process. Another advantage is that it can be omitted.

EXAMPLES The present invention will be explained in more detail below with reference to Examples, but the present invention is not limited thereto.

(Example) Example 1 Using a CVD apparatus as shown in Fig. 1, methylcyclopentadienyl lanthanum (La (C5H5)2CI(3)) was placed in a solid material container 5 kept at about 150°C, and was used as a carrier gas. Ar (argon) gas at 10 S CCM
(Standard cubic centisete
per m1nute: CC/min). On the other hand, copper acetylacetone was placed in the solid material container 7 kept at about 200°C, and Ar gas was added as a carrier gas at 603°C.
A commercial was played. In addition, 02 (oxygen) gas is used as an oxidizing agent at 11
005CC flowing, total 70φX7 from gas inlet port 3
The temperature of the flow path up to the 0 reaction tube introduced into the reaction tube 10 using a 00 mm quartz tube was adjusted to prevent metal compounds from adhering.

On the other hand, a graphite crucible 9 coated with 5iC (silicon carbide) is placed in the reaction tube, and the crucible is maintained at approximately 550°C in an infrared image furnace 13, and acetylacetone strontium (Sr(c5H702)2) is placed in the crucible. I put it in. Ar gas was introduced at 403 CCM from gas inlet 1 as a carrier gas for strontium acetylacetonate to be vaporized, and was evacuated using a turbo molecular pump and a rotary pump.

The above mixed gas was heated to approximately 850°C in an infrared image furnace I5.
A pressure of 20 T was applied on a quartz glass substrate on a susceptor (S i C coated graphite) heated to .

It was thermally decomposed at rr to produce a thin film with a thickness of about 1.5 μm.

When the magnetic susceptibility of the fabricated thin film was measured at low temperatures, the superconducting critical temperature was found to be approximately 39.

Example 2 Using the same CVD apparatus as in Example 1, methylcyclopentadienyl lanthanum (La (C5
H5)2CH3), solid material container 7 contains cyclopentadienyltriethylphosphine copper (Cu (C5H5)
P (C2) (5) 3) was added. The container temperatures were approximately 150°C and 120°C, respectively, and Ar was used as the carrier gas.
were each introduced into the reaction tube at about 1O.

Acetylacetone Ca was placed in a crucible in the reaction tube, and the temperature was raised to about 500° C. in an infrared image furnace 13, and about 405 CCM of Ar carrier gas was flowed through the gas inlet 1.

The above mixed gas was heated in an infrared image furnace 15.
A WI# film having a thickness of about 1° to 3 μm was produced by carrying out a thermal decomposition reaction on the surface of a quartz glass substrate on an iC-coated graphite susceptor at a substrate temperature of about 800° C. and a pressure of 20 Torr.

When the magnetic susceptibility of the produced thin film was measured at low temperature, the superconducting critical temperature was approximately 17.

[Brief explanation of the drawing]

FIG. 1 is an example of a conceptual diagram of a thermal CVD apparatus that can be used in the present invention. In the figure, numerals 1 and 3 are gas inlet ports, 5 and 7 are solid material containers, 9 is a crucible, 10 is a reaction tube, 11 is a substrate, and 13 and 15 are infrared image furnaces.

Claims (1)

[Claims] At least an organometallic compound of at least one metal M selected from the group consisting of an organolanthanum compound and/or a halide of lanthanum, calcium, strontium, and barium, and/or a halide of the metal M, an organocopper compound, and/or copper. (La_(_1_-_x_)M_x)2Cu was deposited on the substrate by chemical vapor deposition using a raw material gas containing a halide and an oxidizing agent as a reaction gas.
A method for producing a superconducting composite oxide, comprising forming a composite oxide whose main component is O_4 (0.02<x<0.20).