JPH05148656A - Production of thin potassium niobate tantalate film - Google Patents

Abstract

PURPOSE:To easily produce the dense thin film of potassium niobate tantalate excellent in orientation property and having a desired composition. CONSTITUTION:A soln. contg. potassium alkoxide, tantalum alkoxide and niobium alkoxide in a specified ratio is refluxed to form a multicomponent alkoxide as the precursor the potassium niobate tantalate expressed by K(TaxNb1-x)O3 (where 0.25<=x<1.00), the reacting liq. is concentrated and applied on the surface of a substrate to form the thin film of the multicomponent alkoxide, and the thin film is heat-treated and then baked.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a potassium tantalate niobate thin film useful as a piezoelectric element material, a pyroelectric element material or an electro-optical material.

[0002]

2. Description of the Related Art In recent years, attention has been paid to the fact that potassium tantalate niobate exhibits piezoelectricity and pyroelectricity, and its thinning has been studied in order to apply it to surface acoustic wave devices, infrared sensors and the like. However, as a means for thinning the film, a known thin film forming technique such as a physical vapor deposition method or a chemical vapor deposition method is usually tried.

[0003]

However, in the physical vapor deposition method, the oxide or carbonate of each component is preliminarily blended in accordance with the composition of potassium tantalate niobate before the film formation step, and After calcination of the mixed powder, the obtained calcination powder must be molded and fired to produce a target, the manufacturing process is very complicated, and the apparatus for physical vapor deposition is expensive. In addition, there is a problem that the composition is liable to change, and it is difficult to obtain a dense thin film having excellent orientation.

Further, unlike the physical vapor deposition method, the chemical vapor deposition method does not require a preparatory step for preparing a target, but most of the starting materials need to be vaporized, and moreover, the deposition on the inner wall of the apparatus during vapor deposition is not necessary. There are problems that the film forming efficiency is low because of the large number and therefore the productivity is low.

Therefore, an object of the present invention is to make it possible to easily manufacture a dense potassium tantalate niobate thin film having a desired composition and excellent in orientation.

[0006]

As a means for solving the above problems, the present invention provides a solution of potassium alkoxide, tantalum alkoxide and niobium alkoxide in a predetermined ratio by refluxing the compound of the general formula: K (Ta _x Nb _1-x ) O ₃ , (where 0.25 ≦ x <1.00) represented by the formula: a complex alkoxide which is a precursor of potassium thallium niobate, and the reaction solution is concentrated. A thin film made of a composite alkoxide is formed by coating on the surface of a substrate, and the thin film is heat-treated and then baked. If necessary, a series of steps from the formation of the composite alkoxide thin film and the heat treatment or the formation of the composite alkoxide thin film to the firing may be repeated to form a thin film having a predetermined thickness.

The starting materials potassium alkoxide, tantalum alkoxide and niobium alkoxide are
Although any one can be used, the number of carbon atoms in the alkoxy group is 1.
It is preferably 5 or less, and more preferably 8 or less.

As a typical potassium alkoxide,
Methoxy potassium, ethoxy potassium, i-propoxy potassium, n-propoxy potassium. i-butoxy potassium,
Examples thereof include, but are not limited to, n-butoxy potassium, sec-butoxy potassium, t-butoxy potassium and the like.

Typical niobium alkoxides include pentamethoxy niobium, pentaethoxy niobium, penta-i-propoxy niobium, penta-n-propoxy niobium, penta-i-butoxy niobium, penta-n-butoxy niobium and the like. However, the present invention is not limited to these.

Further, typical tantalum alkoxides include pentamethoxy tantalum, pentaethoxy tantalum, penta-i-propoxy tantalum, penta-n-propoxy tantalum, penta-i-butoxy tantalum, penta-n-butoxy tantalum, penta. Examples thereof include, but are not limited to, -sec-butoxy tantalum, penta-t-butoxy tantalum, and the like.

The potassium alkoxide, niobium alkoxide and tantalum alkoxide may be used alone or in combination of two or more kinds. In addition, these alkoxides may be individually dissolved in a solvent, and then mixed and refluxed. Alternatively, a solution in which tantalum alkoxide and niobium alkoxide are previously dissolved is refluxed to form a complex alkoxide, and the reaction liquid The potassium alkoxide may be added as it is or after being dissolved in a solvent, and then added and refluxed.

Alcohols and other suitable organic solvents can be used as the solvent. In any case, since the alkoxide hydrolyzes when water is contained, a dehydrated one is used to avoid this. Is preferred.
As the substrate, sapphire, silica, silicon, magnesia, strontium titanate, or any other substance can be used as long as it does not react or decompose at the firing temperature, but when orientation is a problem, magnesia Is preferred.

The heat treatment is preferably carried out at a temperature of 100 ° C. or lower in a mixed flow of oxygen and water vapor. Further, the calcination is carried out at 650 to 800 ° C. for 30 minutes to 1 hour, and it is preferable that the temperature rising rate and the cooling rate at that time are higher, and usually, it is set to 2 to 5 ° C./minute.

[0014]

By using an alkoxide of a metal element constituting K (Ta _x Nb _1-x ) O ₃ as a starting material, a solution having a uniform composition containing no impurity metal element can be prepared and refluxed. Thus, a complex alkoxide which is a precursor of K (Ta _x Nb _1-x ) O ₃ containing each constituent element in a desired molar ratio can be produced. After the reaction solution is concentrated, dipping method or coating method is used. When applied on a substrate by any suitable means, a thin film of composite alkoxide of uniform thickness is formed. Heat treatment of this composite alkoxide thin film removes residual moisture and residual organic components. However, when this heat treatment is performed in a mixed atmosphere of oxygen and water vapor, residual organic components are effectively removed, and When baking can be performed at a low temperature and a composite alkoxide thin film is formed on the (100) surface of the substrate,
The firing produces a dense and oriented thin film having a perovskite structure.

[0015]

EXAMPLE As a starting material, potassium ethoxy (KOC ₂
H ₅ ), pentaethoxytantalum (Ta (OC ₂ H ₅ ) ₅ ) and pentaethoxyniobium (Nb (OC ₂ H ₅ ) ₅ ) are used, and the molar ratio of these is 1: 0.65: 0.35. First, ethoxy tantalum and ethoxy niobium are weighed to 50%.
The mixture was placed in a 0 ml eggplant-shaped flask, 50 ml of ethanol was further added, and the mixture was refluxed at 80 ° C. for 24 hours to prepare a complex alkoxide solution. Separately, to this complex alkoxide solution was added a solution prepared by dissolving ethoxypotassium, which was weighed at the above molar ratio, in 50 ml of ethanol and further heated at 80 ° C.
After refluxing for 24 hours to produce a complex alkoxide which is a precursor of potassium thallium niobate, the reaction solution was concentrated to 0.2 mol / liter, and the concentrated solution was used as a coating solution. What? ? ? The obtained product was confirmed to be a complex alkoxide from the NMR and IR spectral changes. ? ? ?

Then, the MgO crystal substrate was immersed in the coating solution in a dry nitrogen atmosphere, and then 1.
A gel film was formed on the surface of the substrate (MgO (100) surface) by pulling vertically at a constant speed of 85 mm / sec, and the gel film was held in the atmosphere for 3 minutes to be dried. This substrate was placed on a platinum boat, placed in an electric furnace, heated from room temperature to 300 ° C. at a rate of 5 ° C./min, and heat-treated at that temperature for 30 minutes. From the time when the temperature in the furnace reached 100 ° C., the temperature rise and heat treatment were performed while introducing a mixed gas of oxygen and water vapor into the furnace. After the heat treatment, the supply of water vapor is stopped, the temperature is raised while introducing only dry oxygen, the temperature is kept within the range of 550 to 850 ° C. for 1 hour for firing, and then the mixture is cooled at a rate of 5 ° C./min to 0. A smooth, crack-free thin film of 0.25 μm was obtained.

When X-ray diffraction analysis was performed on the obtained thin film, the results shown in FIG. 1 were obtained. FIG. 1 shows the results of a thin film obtained by firing a substrate having a gel film formed thereon at 675 ° C. From the figure, it can be seen that a potassium tantalate niobate thin film having a perovskite structure oriented in the crystal plane orientation of the substrate can be obtained. In addition, what was baked at a temperature of 650 ° C. or lower produced a pyrochlore phase.

[0018]

EFFECT OF THE INVENTION According to the method of the present invention, a potassium tantalate niobate thin film having a desired composition, which is dense and has an excellent orientation and a uniform thickness, can be easily produced at a low temperature.
Moreover, a thin film composed only of the perovskite phase can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing an X-ray diffraction pattern of a potassium tantalate niobate thin film produced by the method of the present invention.

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[Procedure amendment]

[Submission date] November 26, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction content]

[0015]

Example As a starting material, potassium ethoxy (KOC ₂
H ₅ ), pentaethoxy tantalum (Ta (OC ₂ H ₅ ).
₅ ) and pentaethoxyniobium (Nb (OC
₂ H ₅ ) ₅ ) and these are used in a molar ratio of 1: 0.65:
Weighed so as to be 0.35, first, ethoxytantalum and ethoxyniobium were put in a 500 ml eggplant-shaped flask, 50 ml of ethanol was further added, and the mixture was refluxed at 80 ° C. for 24 hours to prepare a composite alkoxide solution. Separately from this, a solution prepared by dissolving ethoxypotassium, which was weighed at the above molar ratio, in 50 ml of ethanol was added, and further refluxed at 80 ° C. for 24 hours,
After producing a complex alkoxide which is a precursor of potassium thallium niobate, the reaction solution was concentrated to 0.2 mol / liter, and the concentrated solution was used as a coating solution. The obtained product was confirmed to be a complex alkoxide from the NMR and IR spectral changes.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichi Kikuta 3-384 Shineicho, Toyoake-shi, Aichi

Claims (4)

[Claims] 1. A solution containing potassium alkoxide, tantalum alkoxide and niobium alkoxide in a predetermined ratio is refluxed to give a compound of the general formula: K (Ta _x Nb _1-x ) O ₃ , (provided that 0.2
5 ≦ x <1.00. ), A complex alkoxide that is a precursor of potassium thallium niobate, is concentrated, the reaction solution is concentrated, and then applied to the surface of the substrate to form a thin film of the complex alkoxide, and the thin film is heat-treated. A method for producing a potassium tantalate niobate thin film, which comprises firing. 2. The method according to claim 1, wherein the heat treatment is performed in a mixed stream of oxygen and steam. 3. The method according to claim 1, wherein the firing is performed at a temperature of 650 ° C. or higher. 4. A complex alkoxide is produced by refluxing a solution in which a tantalum alkoxide and a niobium alkoxide are dissolved, adding potassium alkoxide or a solution thereof, and then refluxing again to produce a complex alkoxide. The method described in.