JPH05139749A - Formation of lead zirconate film - Google Patents

Abstract

PURPOSE:To form a uniform lead zirconate (PbZrO3) film at a low temp. on a substrate having an arbitrary shape without requiring a post-treating process. CONSTITUTION:A substrate is immersed in an alkaline aq. soln. of >=pH 14 contg. >=0.1mol/l Pb ions or suspension and >=0.1mol/l Zr ions or suspension and hydrothermal treatment is carried out at >=200 deg.C to form a lead zirconate film on the surface of the substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for easily and reliably forming a lead zirconate (PbZrO ₃ ) film on a substrate.

[0002]

2. Description of the Related Art Lead zirconate (PbZrO ₃ ) is a typical antiferroelectric material, and titanic acid is widely used as a ferroelectric material, a piezoelectric material, and a pyroelectric material for various purposes. It is known as an end component of lead zirconate (Pb (Ti, Zr) O ₃ ).

Further, PbZrO ₃ is Pb (Ti, Z
r) It can be used as a starting material for an O ₃ solid solution film or as a component of a functionally graded material, and is also attracting attention as a material with potential application as an actuator that produces a large amount of displacement.

As a conventional method of forming a PbZrO ₃ film, for example, a physical vapor deposition method (PVD method) such as a sputtering method or an ion plating method, a thermal decomposition and an oxidation of an organic metal gas which is a thin film material, reduction,
A chemical vapor deposition method (CVD method) in which a thin film composition is deposited on a base material by polymerization or the like to form a thin film, or an organic metal is applied to the base material and baked to form an oxide film, a so-called sol. -Organic metal coating method such as gel method is used.

[0005]

However, in the physical vapor deposition method, it is generally necessary to raise the temperature of the base material such as the substrate to 500 ° C. or higher in order to obtain a crystalline film. However, there is a problem in that the material of the base material is significantly restricted due to exposure to high temperature, and thermal strains are accumulated in the step of cooling the base material, so that the formed lead zirconate film is easily cracked or peeled. Further, since the vapor deposition material is vaporized under a low oxygen partial pressure, the produced lead zirconate film often has oxygen defects, and there is a problem in that the characteristics are deteriorated or varied.

Further, when forming a thin film of a complex oxide such as lead zirconate (PbZrO ₃ ), the evaporation rate varies depending on the element, and therefore the composition of the film is controlled to obtain a target complex oxide. Is difficult to obtain. The slow growth of the film is also a serious drawback of this method.

On the other hand, in the chemical vapor deposition method, there is a problem that the evaporation temperature of the organic metal is relatively high and a large-scale equipment is required. Further, as in the case of the physical vapor deposition method described above, there is a problem. There is a problem that it is difficult to control the composition and it is not easy to form a film having a target composition. Further, there is a drawback that the organometallic compound as a raw material is extremely expensive.

Further, in the organometallic coating method, it is necessary to perform firing at a high temperature of 500 ° C. or higher in order to oxidize the organometallic coated on the substrate to form an oxide film. However, there is a problem that the material of the base material is remarkably restricted because it is exposed to a high temperature, and a large shrinkage occurs in the coating film during the drying and baking steps, so that the formed film is likely to be cracked or peeled.

Further, there is a problem that it becomes difficult to obtain a dense film because it becomes porous due to evaporation and combustion of the organic substance during the firing process.

This invention is based on the conventional lead zirconate (P
It is intended to solve the problems of the method of forming a bZrO ₃ ) film, and it is possible to form a lead zirconate film at a low temperature on a substrate having an arbitrary shape without requiring a post-treatment step. An object is to provide a method for forming a lead zirconate film.

[0011]

In order to achieve the above object, a method for forming a lead zirconate (PbZrO ₃ ) film according to the present invention comprises a lead (Pb) ion or suspension of 0.1 mol / l or more and By immersing the substrate in an alkaline aqueous solution containing 1 mol / l or more zirconium (Zr) ions or suspension and having a pH of 14 or more, and subjecting the substrate to hydrothermal treatment at a temperature of 200 ° C. or more,
A lead zirconate (PbZrO ₃ ) film is formed on the surface of the base material.

[0012]

EXAMPLES Hereinafter, the features of the present invention will be described in more detail by showing examples of the present invention together with comparative examples.

An aqueous solution of lead nitrate (Pb (NO ₃ ) ₂ ) and zirconium oxynitrate (ZrO (NO ₃ ) ₂ .H ₂ O) in an amount giving a predetermined Pb concentration and Zr concentration is added with NaOH.
The treatment solution is prepared by adjusting H ≧ 14. Note that Pb and Zr are not limited to being present as ions, but may be present as suspensions. The treatment solution is put into an autoclave, and a titanium (Ti) substrate (base material) whose surface is clean and whose surface is polished smoothly is immersed in the treatment solution and heated to raise the treatment solution and the titanium substrate to a predetermined temperature. After that, the temperature is maintained at this temperature for a certain period of time, the treatment solution in the autoclave is reacted with the titanium substrate to perform hydrothermal synthesis, and lead zirconate (PbZ
rO ₃ ) film is formed. After the reaction, the titanium substrate is taken out, sufficiently ultrasonically cleaned in distilled water, and dried at 120 ° C. for 60 minutes.

The thin films formed on the surfaces of the samples of Examples and Comparative Examples thus obtained were evaluated.

In Table 1, PbZrO ₃ was measured for thin films formed under various conditions with reaction conditions such as reaction temperature (hydrothermal synthesis temperature), reaction time, Pb ion concentration, Zr ion concentration and pH as parameters. The relationship between the amount of generated phases and the amount of generated phases (heterogeneous phases) other than the PbZrO ₃ phase including the unknown phase is shown.

[0016]

[Table 1]

However, in Table 1, a sample number marked with * indicates a film (comparative example) outside the scope of the present invention.

In Table 1, the values of the amounts of the PbZrO ₃ phase and the heterogeneous phase produced were determined by measuring the integrated intensity of the diffracted X-rays of the PbZrO ₃ phase and the heterogeneous phase by the X-ray diffraction method using CuKα rays (40 kV, 100 mA). , Is the value obtained by standardizing the value with the maximum value of all the measured values.

From Table 1, Pb ion concentration and Zr ion concentration
Degree, pH and reaction temperature are PbZrO 3 Related to production amount of film
You can see that That is, the Pb ion concentration and
When the Zr ion concentration is lower than 0.1 mol / l, PbZ
rO₃No membrane is formed and if the pH is less than 14
Also PbZrO₃No film is formed.

When the Pb ion concentration and the Zr ion concentration are 0.1 mol / l or higher and the pH is 14 or higher, the reaction temperature is 200 ° C. or lower (for example, 175, although not shown in Table 1). Even at (° C.), the formation of the PbZrO ₃ film is recognized to some extent, but the amount of the different phase is larger than the amount of the PbZrO ₃ phase.

On the other hand, when the hydrothermal reaction is carried out at a temperature of 200 ° C. or higher using a treatment solution having a Pb ion concentration and a Zr ion concentration of 0.1 mol / l or higher and a pH of 14 or higher, the reaction Almost a single layer of PbZr regardless of time
An O ₃ film can be obtained.

The X-ray diffraction pattern of the produced film is shown in FIG. 1 (however, the reaction condition is Pb ion concentration = 0.5 mo).
l / l, Zr ion concentration = 0.5 mol / l, pH = 14,
Reaction temperature = 300 ° C., processing time = 30 minutes). Figure 1
Therefore, the film obtained under the above reaction conditions is PbZr
Almost single layer PbZr with few phases (different phases) other than O ₃ phase
It can be seen that it is O ₃ .

In the above examples, the titanium substrate was used as the base material and the PbZrO ₃ film was formed on the surface of the titanium substrate by hydrothermal synthesis.
There is no particular restriction on the type of material that constitutes it, and it is a base made of various materials such as inorganic materials, metal materials, organic materials and their composite materials that have corrosion resistance to treatment solutions and heat resistance to hydrothermal reaction temperature. It is possible to use wood.

The shape of the base material is not particularly limited, and various base materials such as bulk and foil can be used, and the base material is not limited to a flat plate-shaped base material and has a complicated shape. The PbZrO ₃ film can be reliably formed on the surface of the.

Further, in the above embodiment, lead (Pb) and di
As a raw material for ruconium (Zr), lead nitrate (Pb (NO
₃)₂) And zirconium oxynitrate (ZrO (NO₃)₂
・ H The case of using 2O) was explained, but lead (P
Sources of b) and zirconium (Zr) are not limited to these
Lead acetate (Pb (CH₃COOH)_Four) And
Zirconium oxyacetate (ZrO (CH₃COOH)₂)
It is also possible to use other substances such as.

[0026]

As described above, according to the method for forming a lead zirconate (PbZrO ₃ ) film of the present invention, lead (Pb) ions or suspensions of 0.1 mol / l or more and zirconium (Zr) ions or suspensions of 0.1. 1 mol / l
By containing the above and immersing the substrate in an alkaline aqueous solution having a pH of 14 or more, and subjecting the substrate to hydrothermal treatment at a temperature of 200 ° C. or more, a lead zirconate (PbZrO ₃ ) film is formed on the surface of the substrate. Therefore, it is possible to form a uniform lead zirconate (PbZrO ₃ ) film on the base material at a low temperature and without requiring a post-treatment process.

Further, according to the present invention, a lead zirconate (PbZrO ₃ ) film can be easily formed on the surface of a substrate having various shapes made of various materials that can withstand a hydrothermal reaction temperature of 200 ° C. or higher. it can.

Further, when a metal is used as a base material, by using a metal base material having excellent workability as an electrode, various device shapes utilizing the characteristics of the lead zirconate (PbZrO ₃ ) film can be obtained. It is possible to arbitrarily control it according to its use and characteristics, and its use can be further expanded.

[Brief description of drawings]

FIG. 1 is a diagram showing an X-ray diffraction pattern of a film formed by the method for forming a lead zirconate (PbZrO ₃ ) film of the present invention.

Claims (1)

[Claims] 1. An alkaline aqueous solution containing 0.1 mol / l or more lead (Pb) ions or suspensions and 0.1 mol / l or more zirconium (Zr) ions or suspensions, and having a pH of 14 or more. A method for forming a lead zirconate film, which comprises forming a lead zirconate (PbZrO ₃ ) film on the surface of the base material by immersing the base material in water and performing hydrothermal treatment at a temperature of 200 ° C. or higher.