JPH08133734A - Dielectric crystal film - Google Patents

Abstract

PURPOSE: To obtain a dielectric crystal film having a high Curie temp. and not deteriorating its characteristics even at the time of soldering CONSTITUTION: When a dielectric crystal film made of Pb(Zrx Ti1-x )O3 (where 0<=x<=1) is formed on a substrate by hydrothermal synthesis, K is incorporated into the film by <=20at.% of the amt. of Pb.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a piezoelectric actuator,
The present invention relates to a dielectric crystal film that can be used for a piezoelectric sensor, a pyroelectric sensor, a dielectric element and the like.

[0002]

2. Description of the Related Art As mentioned above, dielectric crystal films have a wide range of applications as electronic materials. In particular, various studies have been conducted on the Pb (ZrTi) O ₃ -based material, which is a ferroelectric substance, including the effects of its substitution and additives. However, the ceramic materials that have been practically used so far are
The Curie temperature is 200 to 400 [deg.] C. Therefore, there has been a problem of performance deterioration due to temperature rise associated with soldering. For example, it is used as a pyroelectric material (PbC
a) In the TiO ₃ -based perovskite material, the composition having a large pyroelectric coefficient of 3.5 × 10 ⁻⁸ [C / cm ² · K] and good performance has a low Curie temperature of about 250 ° C. On the other hand, performance improvement by thinning the film has been attempted, but in the conventional method, it is necessary to perform heat treatment for crystallization after film formation, or to keep it at a high temperature during film formation. I can't avoid it. For this reason, a substrate that does not interdiffuse with the ferroelectric crystal film material during the heat treatment process is selected, and in order to prevent cracks from occurring in the ferroelectric thin film material, the substrate is treated with the same heat as the ferroelectric thin film material. There is a problem that it is necessary to select a substrate having a coefficient of expansion.

[0003]

An object of the present invention is to solve the above problems, and to provide a Pb (ZrTi) O ₃ -based material which can be formed into a film by a low temperature process and has a high Curie temperature. With the goal.

[0004]

According to the present invention, a dielectric material of Pb (Zr _x Ti _1-x ) O ₃ (where 0 ≦ x ≦ 1) is formed on a substrate by hydrothermal synthesis. The present invention relates to a dielectric crystal film containing K in an amount of 20 atomic% or less with respect to Pb in the crystal film.

Examples of the substrate used in the present invention include a metal plate, a metal plate whose surface is oxidized, and a resin substrate or an insulating substrate coated with a metal. 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 to 100 μm.
Using a metal substrate such as titanium metal foil with a thickness of m, 50μ
When a ferroelectric crystal film having a thickness of m or less, preferably 10 μm or less is formed on a substrate by a hydrothermal synthesis method or the like, a ferroelectric crystal film having particularly high insulation resistance and small dielectric loss is obtained. You can

The method of forming the ferroelectric crystal film layer of the present invention on the substrate will be described in detail. A Ti substrate or a substrate coated with Ti is selected as a substrate, and a ferroelectric crystal film is formed on the substrate by hydrothermal synthesis. Also,
As the raw material compound containing Pb, Zr, and Ti constituent elements used when forming the ferroelectric crystal film by the hydrothermal method, chloride, oxychloride, nitrate, alkoxide, acetate, hydroxide, Oxides and the like are preferable. This ferroelectric crystal film is formed as follows.

First, a Pb (NO ₃ ) ₂ aqueous solution of 50 mmol / l
500 mmol / l, ZrOCl ₂ aqueous solution 20 mmol / l-500
mmol / l, TiCl ₄ aqueous solution 0.002 mmol / l to 50 mmol
/ l and KOH aqueous solution 1mol / l ~ 8mol / l into the mixed solution of the substrate, at a temperature of 140 ~ 190 ℃, 6
Approximately 24 hours hydrothermal surface treatment, Pb (Zr _X T
i _1−X ) O ₃ (0 ≦ x ≦ 1) form a crystal nucleus. A ferroelectric crystal film having a high orientation is obtained by allowing a Ti-containing starting compound to be present in the formation of crystal nuclei to carry out a hydrothermal reaction and then carrying out a growth reaction.

Next, in order to grow a crystal, Pb (N
O ₃ ) ₂ aqueous solution 50 mmol / l to 500 mmol / 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
The substrate on which the crystal nuclei are formed is placed in a mixed solution of 8 mol / l and subjected to hydrothermal treatment at 150 to 200 ° C. for 1 to 24 hours to perform rapid crystallization. As a result, a ferroelectric crystal film is formed on the substrate. The heating method in the hydrothermal treatment is 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.
It is dried at 00 to 120 ° C. for about 12 hours. The composition of the dielectric crystal film thus formed is 2 with respect to Pb.
It contains 0 atomic% or less of K.

Formation of crystal nuclei by hydrothermal reaction is performed under conditions of Reynolds number of 2000 or less, preferably 1000 or less, followed by crystallization to obtain a ferroelectric thin film having further excellent orientation. The conditions for crystal growth may be laminar flow or turbulent flow, but the film formation rate can be increased by appropriate stirring.

The electrode used when the ferroelectric crystal film obtained in the present invention is formed 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. In addition, when resin is used for the substrate, it cannot be heated to high temperature, so baking type Ag is used.
Electrodes are not preferred.

[0012]

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

Example 1 Pb (NO₃)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) O₃To generate crystal nuclei of
Was. Next, Pb (NO₃) 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 (Z containing K after hydrothermal treatment at 10 ° C for 10 hours
rTi) O₃Was formed. Then, the super sound in pure water
Wave cleaning 3 minutes × 2 times, ultrasonic cleaning in 1 mol / l acetic acid aqueous solution
Purification 3 minutes x 2 times, and further ultrasonic cleaning in pure water 3 minutes
The drying was performed for 12 hours at 100 ° C. for 2 times. This
Fig. 1 shows the X-ray diffraction pattern of the crystalline film obtained in the above manner.
In addition, in the film confirmed by ICP, EPMA, etc.
The K concentration of was 10 atomic% with respect to Pb. This
Thus prepared Pb (Zr_XTi_1-X) O₃(However
However, x is 0.52. ) The membrane is not polarized
Even though the polarization axes are uniform, after heat treatment at 500 ° C
Pyroelectric coefficient is 3.0 × 10^-8[C / cm²・ K] changes
And the Curie temperature is not less than 500 ° C.
It was

Example 2 Next, after forming crystal nuclei by the same method as in Example 1, 16 mmol of an aqueous Pb (NO ₃ ) ₂ solution for crystal growth,
A ZrOCl ₂ aqueous solution (8.32 mmol), a TiCl ₄ aqueous solution (7.68 mmol) and a KOH aqueous solution (2.56 mol) were put into a mixed solution (total amount of solution: 640 ml), and the mixture was heated at 190 ° C. for 2 hours.
A film of Pb (ZrTi) O ₃ was formed under hydrothermal conditions for an hour. Then, the same washing as in Example 1 was performed. The X-ray diffraction pattern of the crystalline film thus obtained is shown in FIG. 2, and the K concentration in the film confirmed by ICP, EPMA, etc. was 15 atomic% with respect to Pb. The Pb (Zr _x Ti _1-x ) O ₃ (where x is 0.52) film thus prepared has the same polarization axis even if polarization treatment is not performed, and the heat treatment at 500 ° C. It was confirmed that the Curie temperature was 500 ° C. or higher without changing the pyroelectric coefficient at 2.5 × 10 ⁻⁸ [C / cm ² · K] even after the treatment.

[0015]

Industrial Applicability As described above, Pb formed by hydrothermal synthesis and containing 20 atomic% or less of K relative to Pb.
The (ZrTi) O ₃ -based dielectric crystal film has a uniform polarization axis even if it is not subjected to polarization treatment, and its Curie temperature is 50.
Since the temperature is as high as 0 ° C. or higher, there is no characteristic deterioration during soldering.

[Brief description of drawings]

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

FIG. 2 Pb after the crystal growth reaction obtained by the present invention
Is a diagram showing an X-ray diffraction pattern of (ZrTi) O ₃ oriented crystalline film.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location H01L 41/187 (72) Inventor Takayuki Kimura 5 1978 at Kogushi, Ube City, Yamaguchi Prefecture Ube Industries, Ltd. Ube Institute

Claims (1)

[Claims] 1. Pb formed on a substrate by hydrothermal synthesis
(Zr_xTi_1-x) O ₃(However, if 0 ≦ x ≦ 1
It 2) with respect to Pb in the dielectric crystal film of
Dielectric bonding characterized by containing 0 atomic% or less of K
Crystal film.