JPH0987017A - Composite dielectric crystal film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a low-cost composite dielectric crystal film applicable to various devices requiring superior characteristics in a high production yield. SOLUTION: This composite dielectric crystal film formed on a substrate by hydrothermal synthesis is represented by the formula (Pb1-x Lx )-(Zr1-y Tiy )1-x/4 O3 (where L is at least one kind of lanthanoid selected from a lanthanoid element group, 0<=x<=0.12 and 0<=y<=1) and has >=90% relative density.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a composite dielectric crystal film that can be used in piezoelectric actuators, piezoelectric sensors, pyroelectric sensors, dielectric elements and the like.

[0002]

2. Description of the Related Art As described above, dielectric crystal films have a wide range of applications as electronic materials. In particular, the dielectric P
Various studies have been conducted on the b (ZrTi) O ₃ material, including the effects of its substitution and additives.

[0003]

In recent years, as the performance and size of communication equipment, information processing equipment, audio-visual equipment, home electric appliances, etc. have been increasing, miniaturization of electronic parts constituting these equipment has been promoted. Weight reduction is being studied, and performance improvement is attempted by thinning. However, although thinning by the conventional ceramics polishing method can obtain a desired density and composition, there is a problem that the yield is poor and the cost is extremely increased in order to form a target thickness (3 to 50 μm). . Further, it was not suitable for forming into a free shape such as a curved surface.

The film can be thinned by using a vacuum process such as a sputtering method or a CVD method. However, in these methods, the film formation at a high temperature or the heat treatment after the film formation is limited to the kind of the substrate. There are problems that it is necessary and difficult to control the composition, and the mass productivity is poor when the film thickness is increased.

It is an object of the present invention to solve the above-mentioned problems and to provide a composite dielectric crystal film having excellent characteristics applicable to various devices.

[0006]

SUMMARY OF THE INVENTION The present invention provides a general formula (Pb _1-x L _x ) (Z) formed on a substrate by a hydrothermal synthesis method.
r _1-y Ti _y ) _{1-x / 4} O ₃ (wherein L represents at least one selected from the group of lanthanoid elements, and 0 ≦ x ≦
0.12 and 0 ≦ y ≦ 1. ), A relative dielectric density of the dielectric crystal film is 90% or more, and relates to a composite dielectric crystal film.

Examples of the substrate used in the present invention include a metal plate, a metal plate whose surface is subjected to oxidation treatment, and a metal-coated resin substrate or insulating substrate. As the metal plate, a titanium substrate, stainless steel, Fe-
Ni alloy or the like is used. Further, as the resin substrate, a heat resistant resin substrate such as a polyimide film or polyphenylene sulfide is preferable. Pt, Ti, or the like is used as the coating metal.

In the present invention, the substrate is 1-100 μm.
1 to 1 using a metal substrate such as titanium metal foil with a thickness of m
When a dielectric crystal film having a thickness of 00 μm, preferably 3 to 50 μm is formed on a substrate by a hydrothermal synthesis method, a relative density of 90% or more and a dielectric crystal film having excellent electric characteristics are obtained. be able to.

The method of forming the dielectric crystal film layer of the present invention on the substrate will be described in detail. A Ti substrate or a Ti-coated substrate is selected as a substrate, and a dielectric crystal film is formed on the substrate by a hydrothermal synthesis method. Further, P used when forming the dielectric crystal film by the hydrothermal synthesis method
As a raw material compound containing b, a lanthanoid element, Zr, and a Ti constituent element, chloride, oxychloride, nitrate, alkoxide, acetate, hydroxide, oxide and the like are preferable. The dielectric crystal film is formed as follows. Examples of the lanthanoid element represented by L include L
a, Ce, Pr, Nd, Pm, Sm, Eu, Gd, D
Examples thereof include y and Ho.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION First, an aqueous solution of Pb (NO ₃ ) ₂ 50
mmol / l to 500 mmol / l, ZrOCl ₂ aqueous solution 20 mmol / l
~ 500 mmol / l, TiCl ₄ aqueous solution 0.002 mmol / l ~
The substrate was put into a mixed solution of 50 mmol / l and a KOH aqueous solution of 1 mol / l to 8 mol / l, and hydrothermally surface-treated at a temperature of 120 to 200 ° C. for 6 to 24 hours to obtain Pb.
A crystal nucleus made of (Zr _{1- y} Ti _y ) O ₃ (0 ≦ y ≦ 1) is formed. A dielectric crystal film having a high relative density can be obtained by performing a growth reaction after performing a hydrothermal reaction in the presence of a Ti-containing raw material compound during the formation of crystal nuclei.

Next, in order to grow a crystal, Pb (N
O _{3) 2} aqueous solution 50mmol / l~500mmol / l, ZrOCl
₂ aqueous solution 10 mmol / l to 500 mmol / l, TiCl ₄ aqueous solution 5 mmol / l to 400 mmol / l and KOH aqueous solution 2 mol / l
8 mol / l, and optionally, L (CH ₃ COO) ₃ (where L represents the same lanthanoid-based element as described above) is added to the substrate, and the substrate on which the crystal nuclei are formed is charged to 100 to 140. Hydrothermal treatment is performed at 1 ° C. for 1 to 96 hours to perform rapid crystallization. As a result, a dielectric crystal film is formed on the substrate. The heating method in the hydrothermal treatment is based on an oil bath or an electric furnace. After that, general cleaning is performed. For example, ultrasonic cleaning is performed in pure water, then ultrasonic cleaning in an acetic acid aqueous solution, and then ultrasonic cleaning in pure water at 100 to 120 ° C.
And dry for about 12 hours.

The relative density of the dielectric crystal film layer formed on the substrate according to the present invention is 90% or more. Since the true density of the dielectric crystal film obtained by the present invention varies depending on the composition, it is represented by the relative density obtained by dividing the measured density by the true density of the composition. The measurement density was measured by the Archimedes method based on the substrate thickness accurately measured by SEM observation.

The electrode used when the dielectric crystal film obtained in the present invention is made into an element is not particularly limited, but an optimum electrode is selected in consideration of cost and mass productivity. For example, Ni by the sputtering method, Ni by the electroless plating method, baking type Ag, etc. are selectively used. In addition, Al by vapor deposition, Pt or Au by sputtering method, etc. are also used. When a resin is used for the substrate, the baking type Ag electrode is not preferable because it cannot be heated to a high temperature.

[0014]

EXAMPLES Hereinafter, specific examples of the present invention will be described in more detail.

Example 1 Pb (NO_Three)₂16 mmol aqueous solution, ZrOCl₂Aqueous solution
8 mmol, TiCl_Four0.08 mmol aqueous solution and KOH water
Solution 0.3 mol in a mixed solution (total solution volume 150 ml)
Install and fix the Ti substrate at 180 ° C for 12 hours with hydrothermal heat.
Treated with Pb (ZrTi) O_ThreeTo generate crystal nuclei of
Was. Next, Pb (NO_Three) ₂Aqueous solution 16
mmol, ZrOCl₂Aqueous solution 8.32mmol, TiCl_Fourwater
A mixture of 7.68 mmol solution and 2.24 mol KOH aqueous solution
Pour into the combined solution (total solution volume 640 ml) and
Pb (ZrTi) O after hydrothermal treatment at ℃ for 10 hours_Three
Was formed. Then, ultrasonic cleaning in pure water for 3 minutes
× 2 times, ultrasonic cleaning in 1 mol / l acetic acid aqueous solution for 3 minutes × 2
Ultrasonic cleaning in pure water for 3 minutes x 2 times
And dried at 100 ° C. for 12 hours. Like this
The relative density of the obtained crystalline film layer was measured by the Archimedes method.
When determined, the relative density was 92.6%. This result
The X-ray diffraction pattern of the crystal film layer is shown in FIG. Also, IC
The composition of the crystalline film layer confirmed by P, EPMA, etc. is P
b (Zr_0.52Ti_0.48) O_ThreeAnd the average crystal film thickness is
It was 5 μm. A gold electrode is deposited on this crystal film layer by vapor deposition.
When the electrical characteristics were measured, the dielectric constant was 12
00 and the dielectric loss was 0.03.

Examples 2 to 3 After forming crystal nuclei by the same method as in Example 1, crystal growth reaction was repeated with the same composition. In Example 2, 3
Times, in Example 3, the crystal growth reaction was performed 10 times, and Pb (Z
An rTi) O ₃ film was formed. After that, the same post-treatment and analysis as in Example 1 were performed. Table 1 shows the composition of these dielectric crystal films and the measurement results.

Examples 4 to 8 After crystal nuclei were formed by the same method as in Example 1, the Zr / Ti composition in the solution was changed as a raw material solution for crystal growth (Examples 4 to 6). , A La element was added (Examples 7 to 8), and the growth reaction was performed in the same manner as in Example 1, and post-treatment and analysis were performed in the same manner as in Example 1. Table 1 shows the composition of these dielectric crystal films and the measurement results.

[0018]

The dielectric crystal film of the present invention has a good yield and is manufactured at low cost, and the obtained dielectric crystal film has a high relative density of 90% or more, and is suitable for various devices requiring excellent characteristics. Can be used for

[0019]

[Table 1]

[Brief description of drawings]

FIG. 1 Pb after a crystal growth reaction obtained according to the present invention
Is a diagram showing an X-ray diffraction pattern of (ZrTi) O ₃ crystal film.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keigo Nagao 5 1978, Kozugushi, Ube, Yamaguchi Prefecture 5 Ube Kosan Co., Ltd. Ube Laboratory

Claims (1)

[Claims] 1. Formed on a substrate by a hydrothermal synthesis method,
General formula, (Pb _1-x L _x ) (Zr _1-y Ti _y ) _{1-x / 4} O
₃ (wherein L represents at least one selected from the group of lanthanoid elements, and 0 ≦ x ≦ 0.12 and 0 ≦ y ≦ 1), wherein the dielectric A composite dielectric crystal film, wherein the relative density of the crystal film is 90% or more.