JP3531688B2 - Dielectric crystal film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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 Dielectric crystal films have a wide range of applications as electronic materials as described above. In particular, Pb (ZrTi) O ₃ -based materials that are ferroelectrics have been studied in various ways, including their substitution and the effects of additives. However, ceramic materials that have been put to practical use so far are:
The Curie temperature is 200 to 400 ° C., and therefore, there has been a problem of performance deterioration due to temperature rise due to soldering. For example, it is used as a pyroelectric material (PbC
a) In a TiO ₃ -based perovskite material, a 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, although attempts have been made to improve performance by thinning, conventional methods require heat treatment for crystallization after film formation or high temperature during film formation. I can't avoid it. For this reason, in the heat treatment step, a substrate having no mutual diffusion with the ferroelectric crystal film material should be selected, and in order to prevent cracks in the ferroelectric thin film material, the substrate should be made to have the same heat as the ferroelectric thin film material. There is a problem that it is necessary to select a substrate having an expansion coefficient.

[0003]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a Pb (ZrTi) O ₃ -based material which can be formed by a low-temperature process and has a high Curie temperature. With the goal.

[0004]

The present invention SUMMARY OF], due hydrothermal synthesis formed on the substrate _{Pb (Zr x Ti 1-x} ) O 3 ( however, 0 <x <1.) Dielectric crystal consisting of In the film, K not less than 10 atomic% and not more than 20 atomic% with respect to Pb
And a dielectric crystal film having a Curie temperature of 500 ° C. or higher . Furthermore, the present invention provides
Starting compound containing element b: 50 mmol / l to 500
mmol / l, raw material compound containing Zr element 20 mm
ol / l to 500 mmol / l, raw material containing Ti element
0.002 mmol / l to 50 mmol / l,
And KOH 1mol / l to 8mol / l mixed aqueous solution
Inside, place a Ti substrate or a substrate coated with Ti
At a temperature of 140 to 190 ° C.
And Pb (Zr _x Ti _1-x ) O ₃ (where 0
<X <1. ) After forming a crystal nucleus
Starting compound containing element 50 mmol / l to 500 m
mol / l, raw material compound containing Zr element 10mmo
l / l-500mmol / l, raw material containing Ti element
Compound 5 mmol / l to 400 mmol / l, and K
In a mixed aqueous solution of OH 2 mol / l to 8 mol / l,
The substrate on which the crystal nuclei are formed is put in, and 150 to 200 ° C.
Pb (Zr _x T) characterized by hydrothermal treatment
i _1-x ) O ₃ (where 0 <x <1).
A method for manufacturing a dielectric crystal film.

[0005] Examples of the substrate used in the present invention include a metal plate, a metal plate having a surface oxidized, a resin substrate or an insulator substrate coated with 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, 1-100 μm is used as a substrate.
Using a metal substrate such as a titanium metal foil with a thickness of 50 m
When a ferroelectric crystal film having a thickness of not more than m, preferably not more than 10 μm is formed on a substrate by a hydrothermal synthesis method or the like, a ferroelectric crystal film having particularly high insulation resistance and low dielectric loss is obtained. Can be.

The method for forming the ferroelectric crystal film layer of the present invention on a 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,
Raw material compounds containing Pb, Zr, and Ti constituent elements used when forming a ferroelectric crystal film by a hydrothermal method include chloride, oxychloride, nitrate, alkoxide, acetate, hydroxide, Oxides and the like are preferred. The ferroelectric crystal film is formed as follows.

First, 50 mmol of Pb (NO ₃ ) ₂ aqueous solution
/ L to 500 mmol / l, ZrOCl ₂ aqueous solution 20m
mol / l to 500 mmol / l, 0.002 mmol / l to 50 mmol / l of TiCl ₄ aqueous solution and KO
In a mixed solution of 1 mol / l to 8 mol / l H aqueous solution,
The substrate is charged, and at a temperature of 140 to 190 ° C., 6 to 2
Surface treatment by hydrothermal treatment for 4 hours, and Pb (Zr _x Ti
_1-x ) A crystal nucleus composed of O ₃ ( 0 <x <1 ) is formed. A ferroelectric crystal film with high orientation can be obtained by performing a hydrothermal reaction in the presence of a Ti-containing raw material compound during crystal nucleus formation and then performing a growth reaction.

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
The substrate on which the crystal nuclei are formed is put into a mixed solution of 8 mol / l and subjected to a hydrothermal treatment at 150 to 200 ° C. for 1 to 24 hours to perform rapid crystallization. Thus, a ferroelectric crystal film is formed on the substrate. The heating method in the hydrothermal treatment is based on an oil bath or an electric furnace. Thereafter, general cleaning is performed. For example, ultrasonic cleaning is performed in pure water, then ultrasonic cleaning is performed in an acetic acid aqueous solution, and then ultrasonic cleaning is performed in pure water.
Dry at 00 to 120 ° C for about 12 hours. The composition of the dielectric crystal film thus formed has a composition of 2 with respect to Pb.
Contains 0 atomic% or less of K.

[0010] The formation of crystal nuclei by the hydrothermal reaction is performed under the condition that the Reynolds number is 2000 or less, preferably 1000 or less, and then crystallized, whereby a ferroelectric thin film having more excellent orientation can be obtained. The crystal growth may be performed under a laminar flow or under a turbulent flow, but the film formation rate can be increased by appropriately stirring.

The electrode used when the ferroelectric crystal film obtained by 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 sputtering, Ni by electroless plating, baking Ag, etc. are selectively used. In addition, Al by vapor deposition, Pt or Au by sputtering, etc. are also used. When a resin is used for the substrate, it cannot be heated to a high temperature.
Electrodes are not preferred.

[0012]

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

Embodiment 1 Pb (NO_Three)_TwoAqueous solution 16 mmol, ZrOCl_TwoAqueous solution
8 mmol, TiCl_Four0.08 mmol of aqueous solution and KOH water
In a mixed solution of 0.3 mol of solution (total volume of solution: 150 ml)
And fix the Ti substrate, and hydrothermal at 180 ° C for 12 hours
Pb (ZrTi) O_ThreeOf crystal nuclei
Was. Next, Pb (NO_Three) _TwoAqueous solution 16
mmol, ZrOCl_Two8.32 mmol aqueous solution, TiCl_Fourwater
Mixing 7.68 mmol of solution and 2.24 mol of aqueous KOH
Into a mixed solution (total amount of the solution: 640 ml),
Pb (Z
rTi) O_ThreeWas formed. After that, super sound in pure water
Ultrasonic washing in 1 mol / l acetic acid aqueous solution twice for 3 minutes x wave washing
Purification 3 times x 2 times, and further ultrasonic cleaning in pure water for 3 minutes
The drying was performed at 100 ° C. for 12 hours. This
FIG. 1 shows the X-ray diffraction pattern of the crystal film obtained as described above.
And in the film confirmed by ICP, EPMA, etc.
Was 10 atomic% with respect to Pb. This
Pb (Zr_XTi_1-X) O_Three(However
And x is 0.52. ) The membrane is not polarized
Even after the heat treatment at 500 ° C
Also has a pyroelectric coefficient of 3.0 × 10^-8[C / cm^Two・ K]
No, it was confirmed that the Curie temperature was 500 ° C or higher.
Was.

Example 2 Next, after crystal nuclei were formed in the same manner as in Example 1, 16 mmol of a Pb (NO ₃ ) ₂ aqueous solution was used for crystal growth.
The mixture was put into a mixed solution (total amount of the solution: 640 ml) of a ZrOCl ₂ aqueous solution (8.32 mmol), a TiCl ₄ aqueous solution (7.68 mmol) and a KOH aqueous solution (2.56 mol).
A Pb (ZrTi) O ₃ film was formed under hydrothermal conditions for a long time. Thereafter, the same cleaning as in Example 1 was performed. FIG. 2 shows the X-ray diffraction pattern of the crystal film thus obtained, and the K concentration in the film confirmed by ICP, EPMA or the like was 15 atomic% with respect to Pb. The Pb (Zr _x Ti _1-x ) O ₃ (x is 0.52) film produced in this way has a uniform polarization axis without any polarization treatment, and is subjected to a heat treatment at 500 ° C. , The pyroelectric coefficient was 2.5 × 10 ⁻⁸ [C / cm ² · K], and the Curie temperature was confirmed to be 500 ° C. or higher.

[0015]

As described above, Pb formed by hydrothermal synthesis and containing 20 atomic% or less of K with respect to Pb.
The (ZrTi) O ₃ -based dielectric crystal film has a uniform polarization axis without any polarization treatment, and has a Curie temperature of 50.
Since the temperature is as high as 0 ° C. or more, there is no characteristic deterioration at the time of soldering or the like.

[Brief description of the drawings]

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

FIG. 2 shows Pb after a crystal growth reaction obtained according to the present invention.
FIG. 3 is a view showing an X-ray diffraction pattern of a (ZrTi) O ₃ oriented crystal film.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-211523 (JP, A) JP-A-5-139749 (JP, A) JP-A-2-212316 (JP, A) JP-A 62-115 216917 (JP, A) JP-A-63-85015 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C01G 1/00-57/00 C30B 7/10 C30B 29/22 H01B 3/12 301 H01L 41/187

Claims (4)

(57) [Claims] 1. Pb formed on a substrate by hydrothermal synthesis
_{(Zr x Ti 1-x)} O 3 ( however, 0 <x <1.) In the dielectric crystal film consisting of, 1 for Pb
It contains 0 atomic% or more and 20 atomic% or less of K, and has a Curie temperature.
A dielectric crystal film having a temperature of 500 ° C. or higher . 2. A raw material compound containing Pb element of 50 mm
ol / l to 500 mmol / l, containing Zr element
Compound 20 mmol / l to 500 mmol / l, Ti
Starting compound containing element 0.002 mmol / l to 5
0 mmol / l, and KOH 1 mol / l to 8 mol
/ L of a mixed aqueous solution of Ti substrate or Ti
Into the substrate, and at a temperature of 140 to 190 ° C,
After performing surface treatment with hydrothermal heat, Pb (Zr _x Ti _1-x )
O ₃ (where 0 <x <1)
After forming Starting compound containing Pb element 50 mmol / l to 50
0 mmol / l, raw material compound containing Zr element 10 m
mol / l to 500 mmol / l, containing Ti element
Starting material compound 5 mmol / l to 400 mmol / l, and
And KOH 2mol / l to 8mol / l mixed aqueous solution
The substrate on which the crystal nuclei are formed is put into
Pb (Zr _x Ti
_1-x ) O ₃ (where 0 <x <1)
A method for manufacturing a dielectric crystal film. 3. The raw material compound containing the Pb element, Z
a raw material compound containing an r element, and a
Starting compounds are chloride, oxychloride,
Acid salts, alkoxides, acetates, hydroxides or oxides
3. The ferroelectric crystal film according to claim 2, wherein
Manufacturing method. 4. The method according to claim 1, wherein the raw material compound containing the Pb element is P
b (NO3) 2, a raw material containing the Zr element
The compound is ZrOCl ₂ and an element containing the Ti element.
The charge compound is TiCl _{4. The method according} to claim 2, wherein
A method for producing a ferroelectric crystal film according to the above.