JPH0597409A - Production of oxide super conductor by cvd method - Google Patents

Abstract

PURPOSE:To accelerate the evaporation of a raw material compd. and to produce the oxide super conductor at a low raw material loss by adding a solid bidentate ligand having nearly the same evaporation temp. as the evaporation temp. of the raw material compd. into the raw material compd. CONSTITUTION:The raw material compd. contg. the constituting elements of the oxide super conductor, for example, a powder mixture 12 consisting of Y(DPM)3, Ba(DPM)2, Cu(DPM)2(DPM: 2,2,6,6-tetramethyl-3,5-heptanedione) is housed into a /N power feeder 3 and is transported by a carrier gas 2, such as Ar, to an evaporator 5. The powder mixture is heated and evaporated by a heater 4 and the evaporated gas 13 is introduced into a chamber (not shown in Fig.). The oxide super conductor film of a Y-Ba-Cu-O system, etc., is formed by a chemical reaction on the substrate surface. The bidentate ligand which is solid at ordinary temp. and has nearly the same evaporation temp. as the evaporation temp. of the raw material compd. is added into the above-mentioned raw material compd. in the above-mentioned process for production of the oxide super conductor by the CVD method. The compd., such as Ba(DPM)2, which is hardly evaporatable and the bidentate ligand are bonded and the evaporation thereof is accelerated in this way.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a chemical vapor deposition method (CV).
The present invention relates to a method for forming an oxide superconductor on a substrate by the method (D method), and to a method for promoting the vaporization of a compound that is difficult to vaporize such as a Ba compound to reduce the loss of raw material compounds.

[0002]

2. Description of the Related Art In recent years, oxide superconductors having a critical temperature (Tc) higher than the liquid nitrogen temperature (about 77 K) have been used, for example, Y-Ba-Cu-O system and Bi-Sr-Ca-Cu-O system.
System, oxide superconductors such as Tl-Ba-Ca-Cu-O system have been discovered. In order to apply these oxide superconductors to various superconducting devices such as electric power transportation, superconducting magnets, and superconducting devices, various studies have been conducted for their practical use.

One of the methods for producing such an oxide superconductor
As one of them, there is known a method of forming an oxide superconducting thin film on the surface of a base material by a thin film forming means such as a chemical vapor deposition method (CVD method). It is known that the oxide superconducting thin film formed by this thin film forming means has a large critical current density (Jc) and a material having excellent superconducting properties can be obtained. Further, the CVD method has been attracting attention as a means for forming a thicker film in a short time because of its high film forming speed.

The raw material compound used in the method for producing an oxide superconductor by the CVD method is an acetylacetone compound of each element constituting the oxide superconductor, a diketone compound such as a hexafluoroacetylacetone compound, or cyclopentadiene. An organometallic complex such as an enyl compound is used. For example, for producing a Y-Ba-Cu-O-based superconductor, 2,2,6,6 tetramethyl-3,5 of each element of Y, Ba and Cu is used. -Heptanedione (hereinafter referred to as DPM) compound, that is, Y (DPM) ₃ , BA (DP
M) ₂ and Cu (DPM) ₂ may be mentioned.

FIG. 2 shows a gas supply unit of a CVD apparatus as an example of a conventional CVD apparatus used for manufacturing an oxide superconductor. This gas supply unit is
M) ₃ , Ba (DPM) ₂ , Cu (DPM) ₂ mixed powder 1 mixed powder 1 for feeding a fixed amount by a carrier gas 2 such as argon gas, a powder feeder 3,
The vaporizer 5 is provided with a heater 4 for heating the mixed powder 2 conveyed from the powder feeder 3 to a vaporization temperature or higher thereof.

Mixed powder 1 set in powder feeder 3
Are sucked out by the carrier gas 2 and transported to the vaporizer 5. The mixed powder 1 conveyed to the vaporizer 5 is heated by a heater 4 and vaporized, and the vaporized gas 6 is supplied into a reaction chamber (not shown) together with a carrier gas.

[0007]

However, among the raw material compounds used in the production of oxide superconductors, particularly Ba (DPM) ₂ is in the temperature range from vaporization to decomposition (vaporization temperature). Area) is narrow, and thermal decomposition easily occurs while vaporizing, and an oxide superconductor having a specific composition such as Y ₁ Ba ₂ Cu ₃ O _7- x (Y: B
In order to obtain a composition in which the molar ratio of a: Cu is 1: 2: 3, the charging ratio of the Ba compound is Y: Ba: Cu = 1: 1.
0 or more: Must be set to 3. Therefore, there is a problem that a large amount of Ba compound is lost.

As a method for reducing such a loss of the Ba compound as much as possible, a method has been proposed in which tetrahydrofuran (hereinafter referred to as THF) gas is introduced into the vaporizer 5 together with the mixed powder as shown in FIG. .. That is, a carrier gas 9 such as Ar is supplied to a bubbler 8 containing THF 7 (liquid), and a gas 10 containing THF gas is supplied.
It is introduced into the vaporizer 5 together with the mixed powder 1, and the mixed powder is vaporized in the presence of THF. The vaporized gas 11 is supplied to the reaction chamber of the CVD device.

In this method, THF is mixed with Ba in the mixed powder.
By combining with (DPM) ₂ , vaporization is promoted and decomposition is suppressed. As a result, the raw material charging ratio for obtaining the composition of Y: Ba: Cu = 1: 2: 3 is 1: 2.1 to 2.5: 3.
It is improved to some extent. However, in this method, THF gas must be supplied while controlling the flow rate in a separate system, and it is difficult to form a film under constant conditions. The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for producing an oxide superconductor by a CVD method capable of easily forming a film while reducing the loss of a compound that is difficult to vaporize such as a Ba compound. There is.

[0010]

According to the present invention, a compound containing a constituent element of an oxide superconductor is vaporized and introduced into a chamber, and oxide superconductor fine particles are produced by a chemical reaction in the chamber, In a method for producing an oxide superconductor by a CVD method for forming an oxide superconducting thin film on a surface of a substrate provided in the chamber, a raw material compound is solid at room temperature and has a vaporization temperature similar to that of the raw material compound. The above problem was solved by adding a bidentate ligand which is a compound (1) to vaporize the raw material compound, and combine the compound that is difficult to vaporize with the bidentate ligand to promote the vaporization.

[0011]

[Function] In the compound containing the constituent elements of the oxide superconductor,
By adding a bidentate ligand that is solid at room temperature and has a vaporization temperature similar to that of the raw material compound, even among the raw material compounds for producing an oxide superconductor by the CVD method, it is difficult to vaporize and Ba easily decomposes. The bidentate ligand added to the compound or the like binds to form a coordination compound which is easily vaporized or hardly decomposed during vaporization, and vaporization of the compound is promoted.

[0012]

EXAMPLE FIG. 1 is a diagram for explaining an example of a method for producing an oxide superconductor according to the present invention. In this example, the case where the oxide superconductor is formed by using the gas supply unit configured with substantially the same components as the gas supply unit of the CVD apparatus shown in FIG. 2 is illustrated.

In this manufacturing method, for example, Y ₁ Ba ₂ Cu _{3 is used.}
When producing an oxide superconductor having a composition of O _7- x (Y: Ba: Cu molar ratio of 1: 2: 3), Y (DPM) ₃ , B
A mixed powder 12 obtained by adding and mixing a bidentate ligand to each compound powder of a (DPM) ₂ and Cu (DPM) ₂ is used.

Examples of the bidentate ligand include oxycarboxylic acids, dioxy compounds, oxioximes, oxyaldehydes (or their derivatives), diketones and their similar compounds, oxyquinones, troborones, N-oxide compounds and amino compounds. Carboxylic acids and similar compounds, hydroxylamines, oxines, aldimic acid, oxyazo compounds, nitrosonnaphthols, triazenes, biurets, formazanes and dithizones, piguanides, glyoximes, diamines and similar compounds, hydrazine derivatives, thioethers Of the various materials such as bisphenols, those that are solid at room temperature and have a vaporization temperature similar to that of the raw material compound are used, and for example, o-phenanthroline is preferably used.

By adding this bidentate ligand to a raw material compound for producing an oxide superconductor by the CVD method,
Among these compounds, a bidentate ligand is bonded to a material such as a Ba compound that is difficult to vaporize and decomposes to form a coordination compound that easily vaporizes or is difficult to decompose upon vaporization,
The vaporization of the compound is promoted.

The amount of the bidentate ligand added is appropriately set depending on the amount of the refractory compound such as Ba compound to be added.
For example, Y (DPM) ₃ : Ba (DPM) ₂ : Cu (DP
When each raw material compound is mixed in a ratio of M) ₂ = 1: 2: 3, it is preferable to add about 0.3 to 1.5 (weight ratio) to this mixture 1. When the amount of the bidentate ligand added is small, the bidentate ligands that are difficult to vaporize such as the Ba compound in each raw material compound are insufficient, and the effect of promoting the vaporization of the Ba compound or the like is sufficient. You will not be able to get it. On the other hand, even if the bidentate ligand is added excessively, the effect of promoting vaporization reaches a ceiling, and the required amount of oxygen, heat, etc. for decomposing the bidentate ligand added during the CVD film formation increases. Therefore, the film forming efficiency is deteriorated.

Y (DPM) ₃ , Ba (DPM) ₂ , Cu
The mixed powder 12 of each compound powder of (DPM) ₂ and the bidentate ligand is set in the powder feeder 3 as shown in FIG. Then, a carrier gas 2 such as argon gas is blown into the powder feeder 3 to suck out a fixed amount of the mixed powder and convey it to the vaporizer 5. The mixed powder 1 conveyed to the vaporizer 5 is heated by the heater 4 and vaporized. This vaporized gas 13 is C
A superconducting thin film is formed by being sent to a reaction chamber (not shown) of a VD device, causing a chemical reaction in the chamber to generate fine particles of an oxide superconductor, and depositing them on the surface of a base material placed in the chamber. .

As described above, by adding the bidentate ligand, which is a solid at room temperature and has a vaporization temperature similar to that of the raw material compound, to the mixed powder of the compound containing the element constituting the oxide superconductor. Among the raw material compounds for the production of oxide superconductors by the CVD method, the bidentate ligand added to the Ba compound or the like that is difficult to vaporize and decomposes easily binds, and easily vaporizes or is unlikely to decompose during vaporization. A coordination compound is formed,
The vaporization of the compound can be promoted. Therefore, it is possible to reduce the production loss of the compound that is difficult to vaporize. Further, as compared with the method of introducing THF gas, the structure of the gas supply unit can be simplified and the film forming operation becomes easy.

In the above-mentioned production example, the case where a Y-Ba-Cu-O-based superconductor is used as the oxide superconductor is taken as an example, but Bi-Sr-Ca-Cu-O-based and Tl-B are used.
It can also be applied to the production of other oxide superconductors such as a-Ca-Cu-O system.

(Experimental example) Y (DPM) ₃ , Ba (DP
M) ₂ and Cu (DPM) ₂ raw materials, Y: Ba: Cu =
The mixture was uniformly mixed in a ratio of 1: 2: 3 (molar ratio), and o-phenanthroline (bidentate ligand) was added at a ratio of 1 (weight ratio) to the mixed powder 1 of each compound. This powder was set in the feeder of the apparatus shown in FIG.
It was supplied to the vaporizer at a rate of g / min and heated to 260 ° C. in the vaporizer to generate vaporized gas.

A vaporized gas was introduced into the CVD chamber, and a Y-based superconducting thin film was formed on the surface of the Hastelloy tape base material placed therein. A 1 m long superconducting tape was manufactured by film formation for 1 hour. The superconducting thin film of the obtained superconducting tape is
It has a uniform composition, and the composition ratio of each constituent element is Y:
It was Ba: Cu = 1: 2: 3 (molar ratio). This superconducting tape had a critical temperature (Tc) of 77K or higher.

[0022]

As described above, according to the method for producing an oxide superconductor according to the present invention, the compound containing the constituent elements of the oxide superconductor of the CVD method is solid at room temperature and is about the same as the raw material compound. By adding a bidentate ligand having a vaporization temperature of, the bidentate ligand added to a Ba compound or the like that is difficult to vaporize and easily decomposes among the raw material compounds for producing an oxide superconductor by the CVD method Coordination compounds are formed which are bound to each other and are easily vaporized or hardly decomposed during vaporization, and the vaporization of the compound can be promoted. Therefore, it is possible to reduce the production loss of a compound that is difficult to vaporize such as a Ba compound. Further, as compared with the method of introducing the THF gas, the structure of the gas supply unit can be simplified and the film forming operation can be facilitated.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a gas supply unit of a CVD apparatus according to a method of the present invention.

FIG. 2 is a schematic configuration diagram showing a gas supply unit of a CVD apparatus for explaining a conventional gas supply method.

FIG. 3 is a schematic configuration diagram showing a gas supply unit of a CVD apparatus for explaining another example of the conventional gas supply method.

[Explanation of symbols]

2 ... Carrier gas, 3 ... Powder feeder, 4 ... Heater, 5
... vaporizer, 12 ... mixed powder, 13 ... vaporized gas

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akira Kagawa 1-5-1, Kiba, Koto-ku, Tokyo Within Fujikura Electric Wire Co., Ltd. Electric Wire Co., Ltd. (72) Inventor Toshio Inoue 20-1 Kitakanyama, Otaka-cho, Midori-ku, Nagoya-shi, Aichi Chubu Electric Power Co., Inc. Electric Power Research Laboratory (72) Inventor Akira Saji, Midori-ku, Nagoya-shi, Aichi 1 at 20 Kitakanzan, Takamachi character Chubu Electric Power Co., Inc.

Claims (1)

[Claims] 1. A substrate provided in the chamber, wherein a compound containing a constituent element of an oxide superconductor is vaporized and introduced into a chamber, and oxide superconductor fine particles are produced by a chemical reaction in the chamber. In the method for producing an oxide superconductor by the CVD method for forming an oxide superconducting thin film on the surface of, a bidentate ligand that is solid at room temperature in the raw material compound and has a vaporization temperature similar to that of the raw material compound. Is added to vaporize the raw material compound, the compound that is difficult to vaporize is bound to the bidentate ligand to accelerate the vaporization thereof, and a method for producing an oxide superconductor by the CVD method.