JP2822228B2 - Superconducting film production paste - Google Patents

Description

The present invention relates to a paste for producing a superconducting film, which is a material for producing a ceramic superconductor film.

[Prior art] Conventionally, a method for forming a ceramic-based superconductor includes a method using a thin film manufacturing technique such as an evaporation method, a sputtering method, and a CVD method, and a method using a solution method and a paste method. There was a method using a film manufacturing technique.

The vapor deposition method, the sputtering method, the CVD method, and the like are methods in which a metal or a compound is gradually laminated in a state of molecules, atoms, or ions using a vacuum device to form a film.

The solution method is a film formation method in which an acetylacetone complex salt, an alkyl metal compound, a metal alkoxide, an organic acid salt, or the like is dissolved in an organic solvent, and the obtained solution is applied to a film formation substrate and fired. This is a film forming method in which raw material fine powder produced by a coprecipitation method or the like is dispersed in an organic solvent, formed into a paste, applied to a film forming substrate, and fired.

[Problems to be Solved by the Invention] Evaporation, sputtering and CVD methods are thin and uniform in thickness, and have crystal orientation and superconductivity (critical temperature,
Critical current etc.). However, in this method, it is difficult to control a desired film composition and to increase the area of the film. Furthermore, since an expensive vacuum device or the like is required, it is difficult to reduce the cost in industrial production.

The solution method and the paste method are methods capable of obtaining a large-area film at low cost with uniformity and small composition deviation. However, the pastes produced so far have not only lacked stability at room temperature and controllability of viscosity, but also achieved the improvement in crystallinity and orientation of the film necessary for improving superconductivity. Was very difficult.

The present invention has been made in order to solve the above problems, and can form a film with a uniform component composition and film thickness. In addition, by changing the combination and mixing ratio of various organic binders and organic solvents, various coatings can be performed. Viscosity adjustment suitable for the conditions can be performed, and a ceramic superconducting film with excellent crystal orientation can be formed. In addition, a paste for preparing a superconducting film with excellent stability and storage stability is provided. Is what you do.

[Means for Solving the Problems] As means for solving the above problems, the present invention provides a superconducting film forming paste described in detail below.

(1) A paste for producing a superconducting film, comprising, as main components, an organic binder, an organic solvent and a ceramic superconductor, a surfactant as a dispersant added thereto, and uniformly mixed. A paste for producing a superconducting film, characterized in that the superconductor is a powder obtained by pulverizing a ceramic superconductor produced by a powder synthesis method to an average particle size of 15 μm or less by mechanical means.

(2) The superconducting film according to claim 1, wherein the organic binder is any one selected from the group consisting of a cellulose ether resin, a cellulose ester resin and an acrylic resin, or a mixture of two or more thereof. Preparation paste.

(3) The organic solvent is one or a mixture of two or more selected from the group consisting of lower and higher polyhydric alcohols having a boiling point of 150 ° C. or higher and ester solvents. Item 7. A paste for producing a superconducting film according to item 1.

(4) The ceramic-based superconductor has a formula: (La
_1-x M _x ) ₂ CuO _4-y [where M is any one selected from the group consisting of Mg, Ca, Sr, Ba, K and Na]; Formula: Ln ₁ Ba ₂ Cu ₃ O _7-y [Ln is Y, La, Nd, Sm, Eu, Gd, D
any one selected from the group consisting of y, Ho, Er, Tm, Yb, and Lu]; a compound represented by the formula: (Bi, Tl) _2-X (Sr, B
a) ₂ Ca _n-1 Cu _n O _{2n + 4} [where n is a natural number such as 1,2,3,4,5]
A compound represented by the formula: or other perovskite type
A superconducting compound having a crystal structure similar to or similar to ABX ₃ and having a BX ₂ plane in which X ions are coordinated with 4 to 6 B site ions, wherein A site ions include Na,
One or more of K, Rb, Ag, Mg, Ca, Sr, Ba, Bi, Tl, Pb, Sb and rare earth metals are selected, and B
One or more transition metals capable of taking a plurality of valence states are selected as site ions, and one or two of O, N, F, P, S and Cl are selected as X ions. The superconducting paste according to claim 1, wherein the above is a selected compound.

[Operation] The superconducting film-producing paste of the present invention having the above-mentioned structure is mechanically processed using a uniform ceramic superconductor produced by a powder synthesis method in a mortar, a ball mill, or the like so as not to lose its crystallinity. Since it is prepared using fine powder obtained by pulverization, it is possible to obtain a superconducting film having excellent crystallinity, orientation, and superconductivity (especially critical current density) after firing on a substrate. It is a new paste.

In addition, the superconducting film-forming paste of the present invention having the above-described structure has a surfactant as a dispersant added thereto.
A ceramic superconductor, which is one of the main components, is easily dispersed uniformly in an organic vehicle including an organic binder and an organic solvent. In a preferred embodiment of the present invention, since a solvent having a high boiling point of 150 ° C. or higher is used as the organic solvent, a paste with little change over time and excellent stability is provided. Incidentally, the surfactant used in the paste of the present invention, organic components such as an organic binder and an organic solvent, when the paste is fired at a temperature of 400 ° C. or more, which is the firing temperature required at the time of main firing after application. Since all are evaporated, there is no adverse effect on the obtained superconducting film.

Furthermore, the paste for producing a superconducting film of the present invention having the above-mentioned structure has a viscosity by changing the kind of the organic binder and the organic solvent, or the solid content of the paste (mixing ratio between the ceramic superconductor and the organic vehicle). Can be adjusted freely, so that brush painting, stamping, spraying,
Since a desired method can be freely selected from various application methods such as screen printing, spin coating, and doctor blade method, a uniform superconducting film can be formed without being limited by the shape of an object to be applied. .

 Hereinafter, the embodiment will be described in detail.

Example 1 In this example, Y ₁ Ba ₂ C was used as a ceramic-based superconductor.
This is an example of a method for producing a superconducting film-forming paste using u ₃ O _7-y .

An organic vehicle prepared by mixing 10% by weight of ethylcellulose, 30% by weight of terpineol, 50% by weight of dibutyl phthalate and 10% by weight of butyl carbitol acetate, and an organic vehicle manufactured by a powder synthesis method.
m-based ceramic superconductor Y ₁ Ba ₂ Cu ₃ O _7-y
Was mixed at a ratio of 3: 7 using three rollers. At this time, several percent of a phosphoric acid ester as a surfactant was added.

A part of this paste was sampled, and the change in weight with respect to temperature was measured. As a result, the weight was reduced from 190 ° C., and was stable at 400 ° C. or more and the initial weight of 70 wt%. Similar results were obtained even when the sampling location was changed (see FIG. 1).

The paste was applied on a MgO substrate by screen printing, baked at 1,000 ° C. for 10 minutes in an oxygen stream, and slowly cooled, whereby a uniform film having a thickness of 20 μm was obtained. When this film was measured by X-ray diffraction, a single-phase Y ₁ Ba ₂ Cu ₃ O _7-y having good crystallinity with C-axis orientation was observed (see FIG. 2). The critical temperature of this superconducting film was 90 K, and the critical current density was 2,000 A / cm ² . The substrate is YSZ, SrTiO ₃ , L
Similar results were obtained when aAlO ₃ or the like was replaced.

Example 2 In this example, Bi _2-x P was used as a ceramic-based superconductor.
This is an example of a method for producing a superconducting film-forming paste using b _x Sr ₂ Ca ₂ Cu ₃ O _10-y (x = 0.4).

An organic vehicle prepared by mixing 8% by weight of ethylcellulose, 32% by weight of terpineol, 50% by weight of dibutyl phthalate and 10% by weight of butyl carbitol acetate, and an organic vehicle manufactured by a powder synthesis method.
Bi _-x Pb _x Sr ₂ C
a ₂ Cu ₃ O _10-y using three rollers and fines (x = 0.4) 3: 7 were mixed in a ratio of. At this time, several percent of a phosphoric acid ester as a surfactant was added.

A part of this paste was sampled, and the change in weight with respect to temperature was measured. As a result, the weight was reduced from 190 ° C., and was stable at 400 ° C. or more and the initial weight of 70 wt%. Similar results were obtained even when the sampling location was changed.

This paste was applied on a MgO substrate by screen printing, baked at 870 ° C. for 10 minutes in an oxygen stream, and then slowly cooled, whereby a uniform film having a thickness of 20 μm was obtained. When this film was measured by X-ray diffraction, Bi in the C-axis oriented crystal having good single-phase _{2-x Pb x Sr 2 Ca} 2 Cu 3 O 10-y (x = 0.4) was observed (the (See FIG. 3). The critical temperature of this superconducting film was 110 K, and the critical current density was 3,000 A / cm ² . Similar results were obtained when the substrate was changed to YSZ, SrTiO ₃ , LaAlO ₃ or the like.

Example 3 In this example, Y ₁ Ba ₂ C was used as a ceramic-based superconductor.
This is an example of producing a paste in which the viscosity is changed by changing the mixing ratio of an organic binder and an organic solvent in a superconducting film-forming paste using u ₃ O _7-y .

Five kinds of organic vehicles prepared by mixing ethyl cellulose (10-X) wt%, terpineol (30 + X) wt%, dibutyl phthalate 50 wt%, butyl carbitol acetate 10 wt% in the range of X = 0 to 5 and mixing. In addition, it is produced by a powder synthesis method and has an average particle size of 3 μm
m-based ceramic superconductor Y ₁ Ba ₂ Cu ₃ O _7-y
And mixed with each other at a ratio of 3: 7 using three rollers. At this time, several percent of a phosphoric acid ester as a surfactant was added.

A part of each paste was collected, and the shear rate was 3 [s
^-1 ], the viscosity was measured to be 3 × 10 ⁵ to 1 × 10 ⁵
The viscosity could be changed to mPa · s. Similar results were obtained even when the sampling location was changed.

Further, these pastes were applied on a YSZ substrate by a doctor grade method, baked in an oxygen stream at 1,000 ° C. for 10 minutes, and gradually cooled to obtain uniform films each having a thickness of 20 μm. When this film was measured by X-ray diffraction, similarly, a single layer of Y ₁ Ba ₂ Cu ₃ O _7-y having good crystallinity with C-axis orientation was observed. The critical temperature of this superconducting film was 90 K, and the critical current density was 2,000 A / cm ² . The substrate is made of MgO, SrT
Similar results were obtained when iO ₃ , LaAlO _3, etc. were replaced.

Example 4 In this example, Y ₁ Ba ₂ C was used as a ceramic-based superconductor.
A method for producing a paste in which the average particle size of the ceramic-based superconductor Y ₁ Ba ₂ Cu ₃ O _7-y powder used in the paste for producing a superconducting film is changed using u ₃ O _7-y is illustrated. Things.

Ethyl cellulose 10wt%, terpineol 30wt%, dibutyl phthalate 50wt%, butyl carbitol acetate
10% by weight, and an organic vehicle prepared by mixing powder with an organic vehicle.
Each powder of the ceramic superconductor Y ₁ Ba ₂ Cu ₃ O _7-y crushed to μm was mixed at a ratio of 3: 7 using three rollers. At this time, several percent of a phosphoric acid ester as a surfactant was added.

These pastes were applied on a YSZ substrate by screen printing, baked in an oxygen stream at 1,000 ° C. for 10 minutes, and gradually cooled, whereby uniform films having a thickness of 20 μm were obtained. When this film was measured by X-ray diffraction, the average particle size was determined.
In the film having a thickness of 15 μm or less, Y ₁ Ba ₂ Cu ₃ O _7-y of C-axis oriented single phase having good crystallinity was observed (see FIG. 4). The critical temperature of this superconducting film is 90K, and the critical current density is 2,000A / cm
^{Was 2} . Similar results were obtained when the substrate was changed to MgO, SrTiO ₃ , LaAlO ₃ or the like.

Comparative Example 1 Ethyl cellulose 10 wt%, terpineol 30 wt%, dibutyl phthalate 50 wt%, butyl carbitol acetate
10 wt%, and a fine powder of a ceramic superconductor Y ₁ Ba ₂ Cu ₃ O _7-y having an average particle diameter of 1 μm or less prepared by a coprecipitation method using three rollers. : 7. At this time, several percent of a phosphoric acid ester as a surfactant was added.

A part of this paste was sampled, and the change in weight with respect to temperature was measured. As a result, the weight was reduced from 190 ° C., and was stable at 400 ° C. or more and the initial weight of 70% by weight. Similar results were obtained even when the sampling location was changed.

However, this paste was screen-printed with YSZ
When applied on a substrate, baked at 1,000 ° C for 10 minutes in an oxygen stream and slowly cooled, a uniform film with a thickness of 20 μm was obtained.
When this film was measured by X-ray diffraction, there was no orientation.
Y ₁ Ba ₂ Cu ₃ O _7-y was observed. The critical temperature of this superconducting film was 90 K, and the critical current density was 20 A / cm ² .

Comparative Example 2 10% by weight of ethylcellulose, 30% by weight of terpineol, 50% by weight of dibutyl phthalate, butyl carbitol acetate
10 wt%, and a ceramic superconductor Bi _2-x Pb _x Sr ₂ Ca ₂ Cu ₃ O _10-y (x = 0.4) having an average particle size of 1 μm or less, prepared by co-precipitation with an organic vehicle prepared by mixing 10 wt%. Was mixed at a ratio of 3: 7 using three rollers. At this time, several percent of a phosphoric acid ester as a surfactant was added.

A part of this paste was sampled, and the change in weight with respect to temperature was measured. As a result, the weight was reduced from 190 ° C., and was stable at 400 ° C. or more and the initial weight of 70 wt%. Similar results were obtained even when the sampling location was changed.

However, this paste was screen-printed with YSZ
When coated on a substrate, baked at 950 ° C. for 10 minutes in an oxygen stream, and slowly cooled, a uniform film having a thickness of 20 μm was obtained. However, when this film was measured by X-ray diffraction, there was no orientation. Bi
_2-x Pb _x Sr ₂ Ca ₂ Cu ₃ O _10-y (x = 0.4) was observed. The critical temperature of this superconducting film is 100K, the critical current density is 30A / cm
^{Was 2} .

Comparative Example 3 10% by weight of ethyl cellulose, 30% by weight of terpineol, 50% by weight of dibutyl phthalate, butyl carbitol acetate
10 wt%, and a fine powder of a ceramic superconductor Y ₁ Ba ₂ Cu ₃ O _7-y produced by a powder synthesis method and pulverized to an average particle size of 3 μm or less using a ball mill. The mixture was mixed at a ratio of 3: 7 using three rollers. At this time, no surfactant was added.

A part of the paste was sampled, and the change in weight with respect to temperature was measured. As a result, the weight decreased from 190 ° C., and was stable at 400 ° C. or more and the initial weight of 65% by weight. The results obtained when the sampling location was changed varied.

This paste was applied on a YSZ substrate by screen printing, baked in an oxygen stream at 1,000 ° C for 10 minutes, and then cooled slowly. As a result, a non-uniform film with a thickness of 10 to 20 μm was obtained. Y ₁ Ba
₂ Cu ₃ O _7-y was observed. The critical temperature of this superconducting film is 90
K, the critical current density was 200 A / cm ² .

[Effect of the Invention] The superconducting film-producing paste of the present invention having the above-mentioned structure is mechanically machined using a mortar, a ball mill, or the like so that the uniform ceramic superconductor produced by the powder synthesis method does not lose its crystallinity. Since a fine powder obtained by pulverization is used, it is possible to obtain a superconducting film having excellent crystallinity, orientation, and superconducting properties (particularly, critical current density) after firing on a substrate.

In the superconducting film-forming paste of the present invention having the above structure, a surfactant is added as a dispersant, so that the ceramic-based superconductor is uniformly dispersed in an organic vehicle prepared from an organic binder and an organic solvent. It is easy to be dispersed. In a preferred embodiment, the organic solvent is 15
Since a substance having a high boiling point of 0 ° C. or higher is used, the composition has excellent stability with little change over time. The organic components such as the surfactant, the organic binder and the organic solvent are completely evaporated during firing at a required temperature of 400 ° C. or more during the final firing after coating, so that the resulting superconductive It does not adversely affect the membrane.

Further, the paste for producing a superconducting film of the present invention having the above-described structure can freely adjust the viscosity by changing the kind of the organic binder and the organic solvent, and the solid content (mixing ratio between the ceramic-based superconductor and the organic vehicle). It can be adjusted to any of the various coating methods such as brush coating, stamping, spraying, screen printing, spin coating, doctor blade method, etc. A uniform superconducting film can be formed without limitation.

[Brief description of the drawings]

FIG. 1 is a graph showing a temperature-weight relationship for a superconducting film-forming paste of the present invention containing Y ₁ Ba ₂ Cu ₃ O _7-y as a ceramic-based superconductor. FIG. 2 is an X-ray diffraction diagram of a Y ₁ Ba ₂ Cu ₃ O _7-y superconductor thick film obtained using the superconducting film forming paste of the present invention. Figure 3 is a X-ray diffraction pattern of _{Bi 1.6 Pb 0.4 Sr 2 Ca 2} Cu 3 O 10-y superconducting thick film obtained using the superconducting film prepared paste for the present invention. FIG. 4 is a graph showing the relationship between the particle diameter and the orientation-dependent characteristics of the Y ₁ Ba ₂ Cu ₃ O _7-y superconductor thick film obtained using the superconducting film forming paste of the present invention. is there.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tadazaki Yuzo 1-8-2 Marunouchi, Chiyoda-ku, Tokyo Dowa Mining Co., Ltd. (72) Inventor Shigeo Nagaya 2-chome Rokuno, Atsuta-ku, Nagoya-shi, Aichi Prefecture No.4-1 International Superconducting Technology Research Center Nagoya Laboratory, Superconducting Engineering Laboratory (72) Inventor Masamichi Miyajima 2-4-1 Rokuno, Atsuta-ku, Nagoya-shi, Aichi Japan International Superconducting Technology Research Center Nagoya Laboratory, Superconductivity Engineering Laboratory (72) Inventor Izumi Hirabayashi 2-4-1 Rokuno, Atsuta-ku, Nagoya-shi, Aichi Nagoya Laboratory, Superconductivity Engineering Research Center, International Superconducting Technology Research Center (56) References JP-A-1-230404 (JP, A) JP-A-1-215702 (JP, A) JP-A-2-88407 (JP , A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C01G 1/00-57/00 H01B 12/00 H01L 39/00-39/24

Claims (4)

(57) [Claims] 1. A paste for producing a superconducting film, comprising an organic binder, an organic solvent and a ceramic superconductor as main components, a surfactant as a dispersant added, and uniformly mixed. The ceramic-based superconductor is a crystalline powder produced by pulverizing a ceramic-based superconductor produced by a powder synthesis method to a mean particle size of 15 μm or less and 1 μm or more by mechanical means, and its crystal is C A paste for producing a superconducting film, which is axially oriented. 2. The method according to claim 1, wherein the organic binder is at least one selected from the group consisting of a cellulose ether resin, a cellulose ester resin and an acrylic acid resin, or a mixture of two or more thereof. Paste for making conductive film. 3. The method according to claim 1, wherein the organic solvent is one or a mixture of two or more selected from the group consisting of lower and higher polyhydric alcohols having a boiling point of 150 ° C. or more and ester solvents. The paste for producing a superconducting film according to claim 1. 4. The method according to claim 1, wherein the ceramic-based superconductor has the formula:
_1-X M _x ) ₂ CuO _4-Y [where M is any one selected from the group consisting of Mg, Ca, Sr, Ba, K and Na]; Formula: Ln ₁ Ba ₂ Cu ₃ O _7-Y [Ln is Y, La, Nd, Sm, Eu, Gd, D
any one selected from the group consisting of y, Ho, Er, Tm, Yb, and Lu]; a formula: (Bi, Tl) _2-X (Sr, B
a) ₂ Ca _n-1 Cu _n O _{2n + 4} [where n is a natural number such as 1,2,3,4,5]
A compound represented by the formula: or other perovskite type
Similar to or similar to ABX ₃ , a superconductor compound having a crystal structure having a BX ₂ plane in which 4 to 6 X ions are blended with B site ions, wherein A site ions include Na,
One or more of K, Rb, Ag, Mg, Ca, Sr, Ba, Bi, Tl, Pb, Sb and rare earth metals are selected, and B
One or more transition metals capable of taking a plurality of valence states are selected as site ions, and one or two of O, N, F, P, S and Cl are selected as X ions. The superconducting paste according to claim 1, wherein the above is a selected compound.