JPH11172489A - Production of barium titanate coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily form a coating film uniform in coating thickness and a compsn. even a substrate of various materials with large area and complicated shape by anodically oxidizing titanium oxide coating film formed on a substrate in an aq. soln. of barium. SOLUTION: Titanium oxide coating film is formed on a substrate of metallic materials such as copper, nickel, platinum, gold, stainless steel or the like and the ones other than titanium metal such as ceramic, glass or the like. The production of this titanium oxide coating film is executed preferably by an electrochemical means such as electrolytic plating which is low is cost, and in which the reduction of the temp. is easy, and at this time, in the insulating substrate, the surface is preferably subjected to electricity conducting treatment. Next, this titanium oxide coating film is anodically oxidized in an aq. soln. of barium to produce barium titanate coating film, and, as posttreatment, heat treatment is executed according to necessary. As for the aq. soln. of barium, preferably, that of barium hydroxide is used, and it is used in such a manner that the concn. is regulated to about 0.005 to 1.0 mol/l, the temp. is regulated to about 10 to 100 deg.C, and the pH is regulated to >=13.0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a barium titanate film used for capacitors, thermistors, pyroelectric sensors, recording media and the like.

[0002]

2. Description of the Related Art Conventionally, barium titanate coatings are industrially useful substances, and their application to capacitors, thermistors, pyroelectric sensors, piezoelectric films, recording media and the like has been studied.

As a method for forming such a barium titanate film, attempts have been made to form a barium titanate film on a substrate by a dry film forming method such as a sputtering method, a vacuum evaporation method, and a CVD method.

[0004] In the hydrothermal electrochemical method, which is a wet film forming method, Japanese Journal of Applied Physics, 28 (1)
989), barium titanate is obtained by anodizing titanium metal in an alkali barium aqueous solution at about 100 ° C. to 200 ° C. in an autoclave, and in other electrochemical methods, Journalof A.
As described in American Ceramic, 76, 2619 (1993), it has been reported that a barium titanate coating can be obtained by anodizing titanium metal in an alkaline barium aqueous solution at about 55 ° C. in a beaker. I have.

[0005]

However, conventional dry film forming methods such as a sputtering method, a vacuum evaporation method and a CVD method require a large and expensive film forming apparatus, and the substrate area on which a film can be formed is limited. However, it has disadvantages such as difficulty in controlling composition and film thickness, and difficulty in film formation on a substrate having a complicated shape.

[0006] Also, in wet film forming methods such as hydrothermal electrochemical method and electrolytic method, since all of these methods form a film by supplying titanium ions from titanium metal,
It has been difficult to form a bismuth titanate coating on a substrate other than titanium metal.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies in view of the above technical problems, and as a result, after forming a titanium oxide film on a conductor other than titanium metal, the titanium oxide film was formed. Anodizing in a barium aqueous solution facilitates the formation of a barium titanate film with a uniform thickness and composition and a wide range of substrates can be selected even on large-area and complex-shaped substrates without requiring a large-scale apparatus. The inventors have found a method that can be obtained, and have completed the present invention.

That is, the present invention relates to a method for producing a barium titanate coating, which comprises forming a titanium oxide coating on a conductor other than titanium metal and then anodizing the coating in a barium aqueous solution. .

[0009] In the manufacturing method of the present invention, there is no particular limitation on the method of forming the titanium oxide film on the substrate. For example, it may be formed by a dry film formation method such as a sputtering method, a vacuum evaporation method, or a CVD method, or a wet film formation method such as a sol-gel method or an electrolytic plating method. Of these, it is desirable to use an electrochemical method such as an electrolytic plating method because advantages such as lowering the temperature of the process and lowering the cost of the equipment used can be obtained.

[0010] The barium source of the barium aqueous solution used in the present invention is not particularly limited as long as it is a water-soluble substance. For example, barium compounds such as barium bromide, barium chloride, barium iodide, barium nitrate, barium hydroxide, and barium acetate can be used. One of these barium compounds may be used, or a plurality thereof may be used as a mixture. Among these barium compounds, it is desirable to use barium hydroxide because it facilitates pH adjustment and prevents entry of halogen ions and the like into the barium titanate coating film to be produced.

The barium concentration in the barium aqueous solution can be set in a wide range. However, if the concentration is too low, only the dissolution of the titanium oxide film occurs and it is difficult to obtain a barium titanate film, and if the concentration is too high, the stability of the aqueous solution is deteriorated, and it is a reaction product with carbon dioxide in the aqueous barium solution. It tends to form barium carbonate precipitates.
For this reason, the barium aqueous solution temperature is usually 0.005 mol
/ L to about 1.0 mol / L is appropriate, and particularly preferably about 0.3 mol / L. Although the liquid temperature of the barium aqueous solution can be set in a wide range, it is usually suitable to be about 10 ° C to 100 ° C, preferably about 50 ° C to 90 ° C. Further, when the pH of the barium aqueous solution is lower than 13.0, it is difficult to obtain a barium titanate coating, so that the pH is suitably 13.0 or more. It is preferably about 5.

Further, various known substrates can be used as the substrate on which the titanium oxide film is formed.
For example, a metal material such as copper, nickel, platinum, gold, and stainless steel, a ceramic substrate, a glass substrate, and the like can be used. Further, a material obtained by subjecting the surface of an insulator substrate to a conductive treatment may be used.

From the viewpoints of further improving crystallinity and correcting film defects, the produced barium titanate film may be subjected to a heat treatment as a post-treatment.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an experiment conducted according to the present invention will be described. All reagents were of the reagent grade. Using sus304 as a substrate for producing a barium titanate film (that is, a working electrode), degreasing was performed according to a standard method. The electrolytic cell is a commonly used three-electrode type (counter electrode: Pt foil 20 × 30 × 0.1 mm, reference electrode: Ag / AgCl containing KCl, cell capacity 300 mL).
It was used.

[0015]

Experimental Example 1 First, a titanium oxide film having a thickness of 0.5 μm was formed on the previously prepared sus304 by a high frequency sputtering method. At this time, titanium dioxide (purity: 99.5%) was used as a target, argon gas (purity: 99.999%) was used as an atmosphere gas at the time of formation, the degree of vacuum in the chamber was 3.0 × 10 ⁻³ Torr, and the power input was 30
The condition was 0 W.

Next, a barium aqueous solution having the following composition was put into the electrolytic cell, and then set in a thermostat, and then anodized under the following conditions.

Barium hydroxide 0.3 mol / L (adjusted to pH 13.5 with 30% by weight aqueous sodium hydroxide solution) In the above aqueous solution, the liquid temperature was maintained at 85 ° C, and +3.0 V
When anodic oxidation was performed for 30 minutes, the colorless and transparent titanium oxide film before anodic oxidation was colored dim yellow. When this film was measured by the X-ray diffraction method, a peak of BaTiO was observed as shown in FIG. 1, and it was found that a crystalline barium titanate film was formed.

[0018]

Experimental Example 2 A 0.4 μm-thick titanium oxide film was formed on the previously prepared sus304 by electrolytic deposition. At this time, an aqueous solution having a pH of 6.0 containing 0.01 mol / L of titanium trichloride, citric acid, potassium nitrate, and hydrogen peroxide was used as an electrolyte for forming a titanium oxide film.

Next, a barium aqueous solution having the following composition was put into the electrolytic cell, and then set in a thermostat, and then anodized under the following conditions.

Barium chloride 0.4 mol / L (adjusted to pH 13.5 with 30% by weight aqueous sodium hydroxide solution) In the above aqueous solution, the liquid temperature was maintained at 90 ° C, and +3.0 V,
Anodization was performed for 30 minutes. When this film was identified by X-ray diffraction in the same manner as in Experimental Example 1, it was found that a crystalline barium titanate film was formed.

[0021]

[Experimental Example 3] A titanium oxide film was formed on sus304 by electrolytic deposition under the same conditions as in Experimental Example 2.

Next, a barium aqueous solution having the following composition was put into the electrolytic cell, and then set in a thermostat, and then anodized under the following conditions.

Barium nitrate 0.1 mol / L (adjusted to pH 13 with a 30% by weight aqueous sodium hydroxide solution) In the above aqueous solution, the liquid temperature was maintained at 65 ° C, and +4.0 V
Anodization was performed in 60 minutes. When this film was identified by X-ray diffraction in the same manner as in Experimental Example 1, it was found that a crystalline barium titanate film was formed.

[0024]

EXPERIMENTAL EXAMPLE 4 A titanium oxide film was formed on a sus 304 by electrolytic deposition under the same conditions as in Experimental Example 2.

Next, a barium aqueous solution having the following composition was placed in the electrolytic cell, and then set in a constant temperature bath, and then anodized under the following conditions.

Barium acetate 0.2 mol / L (adjusted to pH 14.0 with 30% by weight aqueous sodium hydroxide solution) In the above aqueous solution, the liquid temperature was maintained at 65 ° C, and +3.0 V
Anodization was performed for 30 minutes. When this film was identified by X-ray diffraction in the same manner as in Experimental Example 1, it was found that a crystalline barium titanate film was formed.

[0027]

Comparative Example A titanium oxide film was formed on a sus 304 by a high frequency sputtering method under the same conditions as in Experimental Example 1.

Next, a barium aqueous solution having the following composition was placed in the electrolytic cell, and then set in a thermostat, and then anodized under the following conditions.

Barium hydroxide 0.1 mol / L (adjusted to pH 12.5 with 30% by weight aqueous sodium hydroxide solution) In the above aqueous solution, the liquid temperature was maintained at 85 ° C, and +3.0 V
Anodization was performed for 30 minutes. During this anodization, sus
Peeling was observed in a part of the titanium oxide film formed on 304. When this film was identified by an X-ray diffraction method in the same manner as in Experimental Example 1, no peak due to crystalline barium titanate was found, and only a peak due to titanium metal foil was observed.

[0030]

As is apparent from the above description, after a titanium oxide film is formed on a conductor other than titanium metal, the titanium oxide film is anodized in a barium aqueous solution, so that a large scale is obtained. A barium titanate film having a uniform film thickness and composition can be easily obtained even on a substrate having a large area and a complicated shape without requiring an apparatus.

[Brief description of the drawings]

FIG. 1 is a diagram showing an X-ray diffraction chart in Experimental Example 1 of the present invention.

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[Procedure amendment]

[Submission date] December 26, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction contents]

Barium hydroxide 0.3 mol / L (adjusted to pH 13.5 with 30% by weight aqueous sodium hydroxide solution) In the above aqueous solution, the liquid temperature was maintained at 85 ° C, and +3.0 V
Anodization was performed for 30 minutes. When the film obtained by the anodic oxidation was measured by an X-ray diffraction method, a peak of BaTiO ₃ was observed as shown in FIG. 1, and it was found that a crystalline barium titanate film was formed.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI // C25D 11/26 302 C04B 35/46 D

Claims (3)

[Claims] 1. A barium titanate coating comprising: a step of forming a titanium oxide coating on a substrate; and a step of anodizing the titanium oxide coating obtained in the step in an aqueous barium solution. Manufacturing method. 2. The method for producing a barium titanate coating according to claim 1, wherein the titanium oxide coating is prepared by an electrochemical method. 3. The barium aqueous solution has a pH of 1
The method for producing a barium titanate coating according to claim 1, wherein the thickness is 3.0 or more.