JPH0414516B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a solution for producing a piezoelectric thin film and a method for producing a piezoelectric thin film.

``Prior art'' ``Problems to be solved by the invention'' Piezoelectric materials, especially sintered bodies mainly composed of lead and titanium oxides, which are attracting attention as electroceramics, have already been used as ignition elements, speakers, etc.
It is currently widely used in various electrical appliances as ultrasonic transducers and filters. These piezoelectric materials are
Furthermore, with the aim of high frequency applications or new functions, studies are underway to make the shape smaller or thinner.In particular, thin film piezoelectric materials are being used for surface wave filters and electrical spectroscopy elements that utilize optical anisotropy. It is a material that is expected to be applied to

However, when using this piezoelectric thin film material using conventional sintering technology, the molded body must be sliced and polished, which makes the processing process complicated and expensive, as well as increasing the size. It is difficult to form a film, and there is a limit to the film thickness, and the primary particles are large, so it cannot maintain strength, and it is difficult to form a film on another substrate.

In contrast, methods using vacuum technology such as vapor deposition, sputtering, and ion plating
It is possible to form a film of any thickness and densely on a substrate, and it has attracted attention as an important technology for forming electronics-related materials, and this method is also being actively investigated for the production of piezoelectric thin films. However, piezoelectric thin films made using this vacuum technology are quite difficult to stably produce with the desired stoichiometric composition, especially when the composition consists of two or more metals, and for this reason, they are completely different from the bulk material. It is well known that the physical properties are different. It is also known that it is difficult to form a film on a complex shape or large area, and that it is expensive due to equipment costs and poor productivity due to the batch method. A method for producing body thin films is expected.

"Means for Solving the Problems" In view of the above circumstances, the present invention provides a novel piezoelectric thin film manufacturing solution and its manufacturing method that can solve the difficulties of the above-mentioned thin film forming methods.

That is, the first aspect of the present invention is an organometallic compound solution containing one or more metals selected from lead and lanthanum and one or more metals selected from titanium and zirconium, wherein the functional group of the organometallic compound is A solution for manufacturing a piezoelectric thin film characterized by comprising an alkoxy group and a β-diketone group.The second aspect of the present invention is an organometallic compound solution containing lithium and one or more metals selected from tantalum, niobium, and vanadium. A third aspect of the present invention is a solution for producing a piezoelectric thin film, characterized in that the functional group of the organometallic compound consists of an alkoxy group and a β-diketone group.
An organometallic compound solution containing one or more metals and one or more metals selected from titanium and zirconium, the organometallic compound having a functional group consisting of an alkoxy group and a β-diketone group. A method for producing a piezoelectric thin film, which comprises immersing a metal, glass, or ceramic substrate into a humid atmosphere, pulling it out at a constant speed, drying it, and further heat-treating it at a temperature of 400°C or more and 1200°C or less. The fourth aspect of the present invention is lithium, tantalum, niobium,
An organometallic compound solution containing one or more metals selected from vanadium, in which the functional groups of the organometallic compound are an alkoxy group and a β-diketone group. The ceramic substrate is immersed, pulled out at a constant speed into a humid atmosphere, dried, and then heated for an additional 400
Each content is a method of manufacturing a piezoelectric thin film characterized by heat treatment at a temperature of 1200°C or higher.

It is important to use a metal alkoxide as the main component of the organometallic compound used in the present invention, which easily decomposes through hydrolysis or thermal decomposition, but if the composition consists only of a metal alkoxide, it is sensitive to moisture and decomposes. Since it is easily unstable and has poor long-term stability, it is necessary to use a composition in which some functional groups are replaced with β-diketone groups from alkoxy groups, or to use a metal β-diketone complex in combination.

In addition, if each metal alkoxide or metal β-diketone complex is simply mixed in a solvent, other individual metal oxides of the target composite metal oxide may be produced as impurities during thermal decomposition. In most cases, by previously subjecting the mixed solution to reflux treatment for a sufficient period of time, a single-phase composite oxide can be obtained by thermal decomposition. Furthermore, if the addition of β-diketone used for stabilization produces an insoluble precipitate, or if a β-diketone complex with low solubility is used, add an aldehyde in an amount equal to or less than the number of moles of β-diketone and perform reflux treatment. In particular, a stable solution can be obtained.

For these reasons, the transparent piezoelectric film forming solution of the present invention can be produced using the following three methods.

A metal alkoxide is mixed in a solvent to obtain a desired composition ratio, and β-diketone is added to stabilize the mixture. Preferably, after mixing the metal alkoxide in a solvent and subjecting it to sufficient heating and reflux, β-
Add diketone to stabilize.

The metal alkoxide and metal β-diketone complex are mixed in a solvent so as to have a desired composition ratio, and preferably heated under reflux.

When the solubility of the metal β-diketone complex is low in the precipitation method or the method described above, an aldehyde in an amount equal to or less than the number of moles of β-diketone is added and heated under reflux to obtain a uniform stable solution.

The organometallic compound used in the present invention is a metal alkoxide selected from lead, lanthanum, titanium, zirconium, lithium, tantalum, niobium, and vanadium, which are metals necessary for piezoelectric compounds, and a metal β-diketone complex. Alkoxides include reaction products of these metals with monohydric and polyhydric alcohols having 20 or less carbon atoms, preferably alcohols with 5 or less carbon atoms, and metal β-diketone complexes include reactants of these metals with acetylacetone, benzoylacetone, and dipivalo. A reactant of ylmethane, diisobutyrylmethane, 3-methylpentane-2dione, preferably an acetylacetone complex, is used.

The use of metal alkoxides and metal β-diketone complexes can be appropriately selected depending on the stability of the metal alkoxide and the difficulty of production, but depending on the adhesion to the substrate during application, the added organometallic It is desirable that 1/4 or more of the organic functional groups of the compound be alkoxy groups.

Furthermore, the β-diketones added to stabilize the solution are the aforementioned β-diketones, and acetylacetone is particularly preferred, and the amount added is adjusted so that the alkoxy groups account for 1/4 or more of the total organic functional groups. It is desirable to add.

Formaldehyde, paraformaldehyde, acetaldehyde, and benzaldehyde are preferable as the aldehyde used to improve solubility in the solvent when β-diketone complex and β-diketone are added. Particularly good results are obtained by using formaldehyde and paraformaldehyde. is obtained.

Examples of the solvent used in the present invention include monohydric or polyhydric alcohols, carboxylic acid esters, ketones, aromatic solvents such as benzene, and monohydric alcohols such as ethers.
and mixed solvents of two or more types, and lower alcohols, lower acetic esters, tetrahydrofuran, etc. are particularly versatile, but may be appropriately selected depending on the combination of metal alkoxide and metal β-diketone complex.

By immersing a substrate in the piezoelectric film forming solution of the present invention and drawing it out into the humid atmosphere at a constant speed, the alkoxy groups contained in the solution are hydrolyzed, resulting in a thin film that adheres tightly to the substrate. After drying this film at a temperature below the boiling point of the solvent, it is heated in an oxidizing atmosphere to a temperature of 400° C. or more and 1200° C. or less, thereby obtaining a transparent piezoelectric thin film of the desired composition on the substrate.

The substrate material for forming the thin film only needs to have heat resistance to withstand the temperature of the heat treatment, and examples include glass, ceramics, metals, and heat-resistant polymers such as polyimide.

Combinations of piezoelectric metals include lead titanate (PbTiO ₃ ), PZT (PbZr _x Ti _1-x O ₃ ), and combinations of metals selected from lead and lanthanum and titanium and zirconium. ) PLZT
A piezoelectric oxide such as [(Pb _x・La _1-x ) (Zr _y・Ti _1-y )O ₃ ] is obtained, and by the combination of lithium and a metal selected from tantalum, niobium, and vanadium, For example, lithium tantalate (LiTaO ₃ ), lithium niobate (LiNbO ₃ ), and lithium vanadate (LiVO ₃ ) can be obtained.

In addition, trace elements used to improve piezoelectric properties, such as zinc, manganese, antimony, bismuth, iron, gallium, indium, chromium, cobalt, nickel, aluminum, magnesium,
It goes without saying that tin, calcium, barium, strontium, cerium, yttrium, tungsten, etc. may be added as long as they are in the form of metal alkoxide or metal β-diketone complex compounds.

"Effects of the Invention" According to the present invention, 1. It becomes easy to form a film over a large area and a complicated shape.

2. A dense piezoelectric thin film with a smooth surface can be obtained.

3. A piezoelectric thin film with extremely excellent transparency, which is difficult to obtain with a sintered molded body, can be obtained.

4. Since the desired metal composition is placed on the substrate in advance and thermally decomposed, a thin film with the desired stoichiometry can be easily obtained, and the composition ratio can also be freely adjusted.

5. Compared to conventional sintering processes, the desired piezoelectric compound thin film can be obtained with low-temperature heat treatment.

6. Production can be performed in a continuous process, resulting in better productivity and lower film-forming costs than the batch method using vacuum technology.

This provides many advantages that cannot be obtained with conventional techniques such as.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but it goes without saying that the present invention is not limited only to the Examples.

Example 1 25.0 g of diisopropoxy lead, 16.2 g of zirconium tetrabutoxide, and 9.8 g of titanium tetraisopropoxide so that Pb:Zr:Ti was 1:0.55:045.
Ethyl alcohol that has been thoroughly dehydrated
After dissolving in 150 g of ethyl alcohol and refluxing for 4 hours at the boiling point of ethyl alcohol, acetylacetone
5.0 g was added to prepare a piezoelectric film coating solution. When this solution was left in a tightly closed glass container at room temperature for about 3 months, it remained stable without any change.

A piece of quartz glass was immersed in this coating solution, lifted into the atmosphere at a speed of 15 cm/min, dried at room temperature for 30 minutes, and then fired in a Matsufuru furnace at 600°C for 1 hour. As a result, a transparent thin film with a slightly gray color was formed. was obtained, and the film thickness was measured using a step meter and was approximately 1000 Å. Apply this method two more times to obtain a film thickness of approximately 3000Å.
However, the transparency of the film hardly changed, and as a result of elemental analysis using an X-ray microanalyzer, Pb:
It was confirmed that Zr:Ti was 1:0.59:0.41, and a thin film with almost the desired composition was formed. Also, X
As a result of line diffraction, the thin film fired at 600°C showed a PZT crystal pattern, and the thin film fired at 450°C was amorphous.

Example 2 Element ratio of Pb:La:Zr:Ti is 0.92:0.08:0.65:
Lead diacetylacetonate 29.9 to 0.35
g, lanthanum triacetylacetonate 2.8g,
When 20.0 g of zirconium tetrabutoxide and 8.0 g of titanium tetraisopropoxide were added to 150 g of absolute ethyl alcohol and stirred, they were not completely dissolved and an insoluble white precipitate was formed. Therefore, an additional 1.0g
When paraformaldehyde was added thereto and refluxed for 4 hours at the boiling point of ethyl alcohol, a clear yellowish solution was obtained, and this solution remained stable at room temperature for more than 3 months.

This solution was applied and heated on quartz glass under the same conditions as in Example 1 to obtain a transparent thin film with a thickness of about 3000 Å. The elemental composition of the thin film was measured using an energy dispersive scanning electron microscope and found to be Pb:La:Zr:Ti
= 1:0.1:0.7:0.4, which is almost the same as the composition in solution, and further structural analysis by X-ray diffraction revealed a single perovskite structure, indicating that a PLZT thin film was obtained. It was determined that it had been done.

Example 3 10.6 g of lithium acetylacetonate and 38.8 g of niobium pentaisopropoxide were dissolved in 100 g of anhydrous isopropyl alcohol and refluxed for 2 hours at the boiling point of isopropyl alcohol to obtain a colorless and transparent solution.

When this solution was applied on a quartz substrate in the same manner as in Example 1, an amorphous structure was obtained at a firing temperature of 500°C or lower, and a crystalline transparent lithium niobate thin film was obtained at a firing temperature of 650°C or higher. .

Claims (1)

[Scope of Claims] 1. An organometallic compound solution containing one or more metals selected from lead and lanthanum and one or more metals selected from titanium and zirconium, wherein the organometallic compound has a functional group of an alkoxy group. and a β-diketone group. 2. A piezoelectric material, which is an organometallic compound solution containing lithium and one or more metals selected from tantalum, niobium, and vanadium, characterized in that the functional group of the organometallic compound consists of an alkoxy group and a β-diketone group. Solution for producing body thin films. 3. An organometallic compound solution containing one or more metals selected from lead and lanthanum and one or more metals selected from titanium and zirconium, where the functional group of the organometallic compound is an alkoxy group or a β-diketone group. A metal, glass, or ceramic substrate is immersed in a piezoelectric thin film manufacturing solution, pulled out at a constant speed into a humid atmosphere, and then dried.
A method for producing a piezoelectric thin film, further comprising performing heat treatment at a temperature of 400°C or higher and 1200°C or lower. 4. An organometallic compound solution containing lithium and one or more metals selected from tantalum, niobium, and vanadium, the solution for producing a piezoelectric thin film in which the functional groups of the organometallic compound are an alkoxy group and a β-diketone group. A metal, glass or ceramic substrate is immersed in the inside, pulled out at a constant speed into a humid atmosphere, dried, and then heated to a temperature of 400°C or higher to 1200°C.
A method for producing a piezoelectric thin film, characterized by carrying out heat treatment at a temperature below.