JP3126212B2 - Piezoelectric / electrostrictive film type element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric / electrostrictive film type element, and more particularly to a unimorph type or bimorph used mainly for an ink jet print head, a microphone, a sounding body (such as a speaker), various vibrators and oscillators, and a sensor. Type,
The present invention relates to a piezoelectric / electrostrictive film type element that generates bending displacement. The element referred to herein means an element that converts electrical energy into mechanical energy, that is, an element that converts mechanical energy into mechanical displacement or stress or vibration, and also an element that performs reverse conversion. Further, since the element according to the present invention has dielectric properties in addition to piezoelectric / electrostrictive characteristics, it can be used as a film-shaped capacitor element.

[0002]

BACKGROUND ART In recent years, in fields such as optics and precision processing,
Displacement elements that adjust the optical path length and position on the order of sub-microns and detection elements that detect minute displacements as electrical changes have become desired. The development of piezoelectric / electrostrictive elements such as actuators and sensors, which are elements utilizing the reverse piezoelectric effect or the displacement based on the electrostrictive effect that occurs when an electric field is applied to an electrostrictive material, or the opposite phenomenon, has been promoted. I have.

In an ink jet print head or the like, such a piezoelectric / electrostrictive element structure has
Conventionally known unimorph type and bimorph type,
It is preferably adopted. There is a demand for improvements in printing quality and printing speed of printers using such elements, and in order to meet such demands, such piezoelectric / electrostrictive film type elements have been reduced in size and density and operated at lower voltages. The development for high-speed response is underway.

In these unimorph type and bimorph type piezoelectric / electrostrictive elements, it is important to reduce the thickness of a substrate serving as a diaphragm in order to obtain a large bending displacement, a generated force or a generated potential. However, when the thickness of such a substrate is reduced, there is a disadvantage that the strength is reduced. Moreover, the conventional unimorph-type and bimorph-type piezoelectric / electrostrictive elements each employ a structure in which a plate-like component member such as a piezoelectric / electrostrictive plate is attached using an adhesive or the like. For this reason, there has been a problem in the reliability of operation as an element.

[0005]

The present invention has been made in view of the above circumstances, and has as its object to provide a large displacement at a relatively low operating voltage and high reliability. An ink jet print head having a high response speed, a large generating force, and a higher integration.
Provided is a piezoelectric / electrostrictive film element having excellent strength, which is suitably used for a microphone, a sounding body (such as a speaker), various oscillators and oscillators, and furthermore, an acceleration sensor, a pressure sensor, a vibration sensor, an angular velocity sensor, and the like. In addition, in such a piezoelectric / electrostrictive film type element, the distortion and stress generated in the piezoelectric / electrostrictive operating portion can be effectively reduced while securing the adhesion strength between the piezoelectric / electrostrictive operating portion and the substrate. The purpose is to be able to communicate to the substrate.

[0006]

According to the present invention, there is provided a piezoelectric / electrostrictive device comprising a thin ceramic substrate and electrodes and a piezoelectric / electrostrictive layer provided on the ceramic substrate. A piezoelectric / electrostrictive element having a strain operating portion, wherein the piezoelectric / electrostrictive operating portion is formed by a film forming method, and the ceramic substrate is made of yttrium oxide, cerium oxide, magnesium oxide and calcium oxide. The crystal phase is partially stabilized by the inclusion of at least one compound selected from the group, and the crystal phase is mainly tetragonal, or mainly tetragonal, cubic, or monoclinic. The ceramic substrate is made of a material containing zirconium oxide as a main component and composed of a mixed crystal containing a crystal phase, and the surface roughness Ra of the ceramic substrate is 0.03 to 0.03. The piezoelectric / electrostrictive film type element characterized in that it is in the range of .9Myuemu, is to its gist.

[0007]

In the piezoelectric / electrostrictive film element according to the present invention, a thin ceramic substrate and a film-shaped piezoelectric / electrostrictive operating portion (two electrodes) formed on the substrate surface are provided. (Composed of a film-like piezoelectric / electrostrictive layer formed between the film and the electrode film), a large displacement can be obtained at a relatively low operating voltage, and a response speed can be obtained. In addition to being able to obtain a feature that is fast and has a large generating force or generated potential, it has a large number of piezoelectric / electrostrictive operating parts on the same substrate surface, which is good at a film forming process such as a thick film forming method. There is a feature that the element can be formed simultaneously and easily without using an adhesive, and further, there is a feature that the piezoelectric / electrostrictive operation section can be highly integrated.

Further, in the present invention, the ceramic substrate used as a substrate on which such a piezoelectric / electrostrictive operating portion is formed is selected from the group consisting of yttrium oxide, cerium oxide, calcium oxide and magnesium oxide. In addition, since the crystal phase is a material mainly composed of zirconium oxide whose crystal phase is partially stabilized by the inclusion of at least one compound, it has high mechanical strength, high toughness, and piezoelectricity even at a thin plate thickness. Characteristics such as a small stress at the time of heat treatment with the electrostrictive material and a low chemical reactivity with the piezoelectric / electrostrictive material can be obtained, so that an element having excellent characteristics can be provided. It was.

That is, as is well known, zirconium oxide, when in a pure state without any additives, undergoes porcelain destruction due to phase transformation between monoclinic and tetragonal at around 1000 ° C., resulting in a thin substrate. Is difficult to manufacture,
By adding the compound as described above, the crystal phase can be completely or partially stabilized so that such a crystal transformation does not occur. Here, "partially stabilizing" means to adjust a material so that partial crystal transformation can occur. In the present invention, the partially stabilized zirconium oxide whose crystal phase is mainly a tetragonal crystal or a mixed crystal mainly including at least two crystal phases of a tetragonal crystal, a cubic crystal, and a monoclinic crystal Shows high mechanical strength and toughness due to stress-induced crystal transformation, that is, a stress-induced phase transformation strengthening mechanism, etc., and the piezoelectric / electrostrictive layer, the electrode film, and the substrate are integrally formed without an adhesive, and the displacement or It can be very suitably used as a substrate material in a piezoelectric / electrostrictive film-type element which generates force or potential, and a film-type element can be advantageously formed by utilizing such material characteristics. Things.

Further, in the present invention, in order to obtain excellent piezoelectric / electrostrictive material characteristics, as will be described later, the electrode material and the piezoelectric / electrostrictive material do not contain so-called adhesive materials such as glass. Therefore, in order to enhance the adhesion between the piezoelectric / electrostrictive operating portion and the substrate, and to effectively transmit the strain and stress generated by the piezoelectric / electrostrictive layer to the substrate serving as the diaphragm, the reverse operation is effectively performed. To do so, the surface roughness of the substrate is an important factor. And for that purpose, in the present invention,
In the surface roughness represented by Ra, 0.03 to 0.9
A surface roughness in the range of μm, more preferably in the range of 0.1 to 0.7 μm, will be selected. When the surface roughness is increased, the adhesion strength is increased, but the flatness of the piezoelectric / electrostrictive operating portion is reduced, so that the electric field acting on the piezoelectric / electrostrictive layer is not uniform. Will be reduced. In addition, the strength of a substrate having a thickness of 50 μm or less, which is preferably employed in the present invention, is also affected by the surface roughness, so the range of the surface roughness is important.

In the present invention, a component comprising lead magnesium niobate, lead zirconate and lead titanate is used as a main component of the piezoelectric / electrostrictive material, and is combined with the partially stabilized zirconium oxide substrate. During the heat treatment of the piezoelectric / electrostrictive layer formed by the thick film method or the like, there is very little change in the composition of the film-like piezoelectric / electrostrictive layer due to the reaction with the substrate or the like or the occurrence of a crystalline phase such as pyrochlore. The composition and the crystal structure exhibit the characteristic that the piezoelectric / electrostrictive layer can be advantageously formed.

Further, in the piezoelectric / electrostrictive film type element according to the present invention, in order to be able to operate at a low voltage and to obtain a large bending displacement / generating force or generated potential, the thickness is preferably 100 μm or less, preferably 100 μm or less. Is less than 50 μm
An electrostriction operating portion, and a thickness of 50 μm or less, preferably 3 μm or less.
It is composed of a ceramic substrate of 0 μm or less, more preferably 10 μm or less. Further, in order to obtain high mechanical strength even at such a thin plate thickness, as the partially stabilized zirconium oxide, preferably, zirconium oxide stabilized with yttrium oxide is used as a substrate material, and such an oxide is used. The content of yttrium is 2 mol% to 7 mol%, preferably 2 mol% to 4 mol%, and the crystal phase of the partially stabilized zirconium oxide is mainly tetragonal or mainly tetragonal. It is composed of a mixed crystal containing at least two or more crystal phases among a crystal, a cubic, and a monoclinic. Further, from the viewpoint of the mechanical strength of the substrate, the average particle size of the substrate is preferably 0.05 μm to 3 μm, and more preferably 1 μm or less. The crystal particle diameter in such a range is also important for causing the above-mentioned crystal phase to exist stably.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be more specifically described with reference to the drawings showing a specific structure of a piezoelectric / electrostrictive film element according to the present invention. For easy understanding, the same reference numerals are given to components having the same structure or function throughout the drawings.

First, a piezoelectric / electrostrictive film type element (actuator) shown in FIG. 1 has a first electrode film 4 and a film-shaped piezoelectric / electrode on one surface of a thin flat ceramic substrate 2. The strained layer 6 and the second electrode film 8 are sequentially laminated by a normal film forming method to form a multilayer integrated structure. Note that the first and second electrode films 4 and 8 are respectively made of piezoelectric /
Extending from the end of the electrostrictive layer 6, the lead portions 4a,
8a are formed, and a voltage is applied to the respective electrode films 4, 8 through the leads 4a, 8a. The ceramic substrate 2 is made of a partially stabilized zirconium oxide material according to the present invention, and has a surface roughness Ra of 0.03.
It is finished so as to be in a range of 0.9 μm. Therefore, in the piezoelectric / electrostrictive film type element having such a structure, when an electric field is applied to the piezoelectric / electrostrictive layer 6,
Due to the transverse effect of the electric field induced strain, a bending displacement or a generated force in a direction perpendicular to the plate surface of the ceramic substrate 2 is developed.

In FIG. 2, the ceramic substrate 2
A comb-shaped electrode film 14a composed of a plurality of band-shaped electrodes 10 and a band-shaped electrode connection portion 12 connecting them and an electrode film 14b having the same shape are provided on one surface in an arrangement form as shown in FIG. Further, a piezoelectric / electrostrictive layer 6 is formed between the electrode films 14a and 14b so as to be in contact with the electrode films 14a and 14b, thereby forming an integral structure. In the piezoelectric / electrostrictive film type element having such a structure, when an electric field is applied to the piezoelectric / electrostrictive layer 6, the piezoelectric / electrostrictive layer 6 is bent in a direction perpendicular to the plate surface of the ceramic substrate 2 due to a longitudinal effect of electric field induced strain. The displacement or generated force is developed.

FIGS. 3 and 4 show examples in which the shape of the ceramic substrate 2 is changed in the elements shown in FIGS. 1 and 2, respectively. That is, FIG.
4 and FIG. 4, a ceramic substrate 16 is used in which an outer edge portion is made thick and an inner portion is made a thin thick portion 16a, and two thin portions 16a are provided on the surface of the thin thick portion 16a. Piezoelectric / electrostrictive operating portions composed of the electrode films 4, 8; 14a, 14b and the piezoelectric / electrostrictive layer 6 are provided integrally.

Further, the element shown in FIG. 5 has a bimorph type piezoelectric / electrostrictive element in which piezoelectric / electrostrictive operating portions (4, 6, 8) are provided on both surfaces of a thin thick portion 16a of a ceramic substrate 16, respectively. It is an example of a strain film type element.

In the device shown in FIG. 6, two band-like electrode films 18 and 18 are provided on one surface of the ceramic substrate 2.
Are provided so as to be spirally opposed to each other, and the piezoelectric / electrostrictive layer 6 is provided so as to embed these band-shaped electrode films 18, 18.
The piezoelectric / electrostrictive operating section is constituted by the piezoelectric / electrostrictive layers 6 and 8.

FIGS. 7 to 11 show different examples of the element according to the present invention in which a plurality of piezoelectric / electrostrictive operating parts are provided on a ceramic substrate, respectively.
The plurality of piezoelectric / electrostrictive actuating parts, in a laminated form,
Alternatively, in a side-by-side configuration, they are provided on a ceramic substrate.

For example, in FIG. 7, a plurality of strip-shaped electrode films 18 are arranged on one surface of the ceramic substrate 2 at regular intervals, and when the strip-shaped electrode films 18 are embedded, An example is shown in which a piezoelectric / electrostrictive operating section is formed by providing the piezoelectric / electrostrictive layer 6, and further on the piezoelectric / electrostrictive operating section (6, 18),
The electrode film 20, the film-like piezoelectric / electrostrictive layer 22, and the electrode film 20 are sequentially laminated and integrated. With the two electrode films 20 and 20 and the piezoelectric / electrostrictive layer 22,
Another piezoelectric / electrostrictive operating portion is formed.

In the examples shown in FIGS. 8 to 10, a plurality of piezoelectric / electrostrictive operating portions (4, 6, 8) are provided on the ceramic substrate 2 side by side. In the device shown in FIG. 9 and FIG. 9, a slit 24 is formed in the ceramic substrate 2 located between the plurality of piezoelectric / electrostrictive actuation portions (4, 6, 8), so that the respective piezoelectric / electrostrictive The parts are independent from each other. In the element shown in FIG. 10, the ceramic substrate 2 is provided with long rectangular holes 26 at a predetermined pitch to form a ladder-shaped ceramic substrate 2. A piezoelectric / electrostrictive operating portion composed of the first electrode film 4, the film-shaped piezoelectric / electrostrictive layer 6, and the second electrode film 8 is formed on the connection portion 2a sandwiched between the two. In FIG. 8, reference numeral 28 denotes an insulating film for electrically insulating the first electrode film 4 from the second electrode film 8 at the back of the piezoelectric / electrostrictive layer 6.

Further, in the example of the element shown in FIG. 11, a first electrode film 4, a film-like piezoelectric / electrostrictive layer 6, and a second electrode film 8 are formed on one large ceramic substrate 2. Are provided in a structure in which a plurality of the piezoelectric / electrostrictive operation sections are integrally arranged at a predetermined pitch.

FIGS. 12 and 13 show FIG.
2 shows an example in which the shape of the ceramic substrate 2 and the arrangement of the piezoelectric / electrostrictive operating portions (4, 6, 8) are changed. That is, FIG.
As is apparent from FIG. 3, on the back surface of the thick ceramic substrate 16, cavities 30 of a predetermined size are provided in a staggered manner at a predetermined pitch, so that a thin thick portion 16 a provided by the bottom of the cavity 30 is formed. The substrate configuration is a staggered arrangement. And this ceramic substrate 1
As shown in FIG. 13, the surface of the piezoelectric / electrostrictive operating portion (4, 6) is positioned on the thin thick portion 16a.
6, 8) are integrally formed and arranged in a staggered manner.

In each of the elements having such various structures, in order to function as an actuator, a current is applied between the two electrode films constituting the piezoelectric / electrostrictive operating portion in the same manner as in the prior art. When an electric field is applied to the piezoelectric / electrostrictive layer, electric field-induced strain of the piezoelectric / electrostrictive layer based on such an electric field is induced, and the direction perpendicular to the plate surface of the ceramic substrate is generated. Is generated.

Incidentally, in the piezoelectric / electrostrictive film type element according to the present invention, as for the ceramic substrate (2, 16) on which the piezoelectric / electrostrictive operating portion is formed, the material for providing the same is a crystal made of a predetermined compound. A material mainly composed of partially stabilized zirconium oxide whose phase is mainly tetragonal or a mixed crystal composed of at least two or more crystal phases of cubic, tetragonal and monoclinic will be used. . The film-type element according to the present invention is generally heat-treated at a high temperature together with a substrate, as described later, and has heat resistance at that time, reactivity with a piezoelectric / electrostrictive material via an electrode film,
Furthermore, it is based on the finding that the properties of the obtained film-type element, such as the generated force and displacement, are affected by the material properties of the substrate, such as the strength against stress during heat treatment. Zirconium oxide, which has been stabilized stably, has excellent characteristics such as element displacement and generated force, and is extremely effective as a substrate material.

In order to partially stabilize the zirconium oxide and to make its crystal phase mainly a tetragonal crystal or a mixed crystal mainly composed of at least two crystal phases of cubic, tetragonal and monoclinic. As a compound of
Yttrium oxide, cerium oxide, magnesium oxide,
By adding and including at least one compound of calcium oxide, zirconium oxide is partially stabilized, but the partial stabilization is not only the addition of one kind of compound, but also the compounding of those compounds. Partial stabilization of the desired zirconium oxide is also possible by adding in combination. The content of the partial stabilizer is 2 mol% to 7 mol% for yttrium oxide, 6 mol% to 15 mol% for cerium oxide, and 5 mol% to 12 mol for magnesium oxide and calcium oxide. It is preferable to use yttrium oxide as the partial stabilizing agent.
Mol% to 7 mol%, more preferably 2 mol% to 4 mol%
It is desirable that Zirconium oxide obtained by adding and containing yttrium oxide in such a range, the main crystal phase is tetragonal, or cubic, tetragonal,
A mixed crystal composed of at least two or more crystal phases among the monoclinic crystals is partially stabilized, and provides excellent substrate characteristics. The crystal phase discussed here is one in which the fired porcelain substrate is mirror-polished and identified by X-rays. In addition, the average crystal grain size of the substrate is also important in order for the crystal phase to exist stably and to obtain a large substrate strength. That is, the average particle diameter is preferably 0.05 μm to 3 μm, and more preferably 1 μm or less.

The compound used for stabilizing the zirconium oxide substrate is generally yttrium oxide,
Magnesium oxide and the like are known, but the crystal phase to be stabilized differs depending on the amount of such a compound added. However, the crystal phase is not determined only by the amount of such a compound added, but also depends on the crystal particle diameter of the raw material powder, and furthermore, the crystal particle diameter of zirconium oxide porcelain produced by firing, and Relatedly, the firing temperature and time are also factors. For example, when yttrium oxide is used as a stabilizer, in order to make the crystal phase mainly a tetragonal crystal, the amount of the stabilizer added is 2 to 4 mol%, and the particle diameter of the raw material powder is 0.1 μm.
m or less, the crystal grain diameter of the porcelain to be produced is 1 μm or less, and the firing temperature differs depending on the raw material. Therefore, although it cannot be said unconditionally, a temperature and time that do not cause grain growth are required. That is, only when these conditions are satisfied at the same time, it becomes possible to prepare a zirconium oxide substrate mainly composed of a crystal phase in which tetragonal crystals are stably present. On the other hand, in order to make the crystal phase mainly a mixed crystal composed of at least two crystal phases among cubic, tetragonal and monoclinic, the upper limit of the amount of the stabilizer to be added is up to about 7 mol%. ,
The condition that the crystal grain size of the produced porcelain is 3 μm or less is adopted. Outside of these conditions, for example, when the amount of the stabilizer added is less than 2 mol%, monoclinic crystals are predominant, and when the raw material powder and the crystal particle size of the porcelain also increase,
The tetragonal crystal becomes stable and difficult to produce.

Under these circumstances, in order to produce a partially stabilized zirconium oxide substrate according to the present invention, generally, a predetermined amount of the compound described above is used, and a raw material powder having a crystal average particle diameter of 0.1 μm or less is used. And the conditions for setting the firing temperature to 1300 ° C. to 1600 ° C. will be adopted.

As the form of the ceramic substrate, the single plate-shaped object (2) shown in FIGS. 1 and 2 and the bottom of the recess as shown in FIGS. Is a thin portion (16a), and a substrate (1) having a cavity structure in which a piezoelectric / electrostrictive operating portion is formed on the surface of the thin portion.
6), the latter substrate having a cavity structure can reduce the thickness of the substrate at the relevant portion, thereby reducing the strength of the element substrate, and further reducing the piezoelectric strength of the adjacent piezoelectric elements in a juxtaposed configuration. It is preferably used because the electrostriction actuating portions are less likely to interfere with each other due to the thick portion between the thin portion and the thick portion during displacement or vibration.
The substrate (1) having such a cavity structure
With regard to the dimensions of the cavity of 6), the length of such a cavity is preferably from 2 to 20 times its width, while the thinned portion (16a) of the cavity substrate (16)
Is preferably 50% to 90% with respect to the width of the cavity from the viewpoint of the displacement and generation force of the element.

Further, regarding the thickness of the thin ceramic substrate, in order to obtain a high-speed response and a large displacement of the element,
Generally, it is 50 μm or less, preferably 30 μm or less, and more preferably 10 μm or less.

Furthermore, such a ceramic substrate is finally formed into a sintered form, but it can be a sintered substrate before forming the piezoelectric / electrostrictive operating portion. Alternatively, a green sheet of a substrate material may be used to form a piezoelectric / electrostrictive operating portion by forming a film, which will be described later, followed by sintering. And the pattern dimensional accuracy can be obtained. The ceramic substrate (16) having a cavity structure is formed by laminating a thin green sheet to be a thin thick part on a green sheet having a hole by using a machining method such as a mold or ultrasonic processing, and thermocompression bonding. After that, it is preferable to produce by firing and integrating from the viewpoint of high reliability. Further, a sintering aid such as aluminum oxide, titanium oxide, or clay may be added to the partially stabilized zirconium oxide-based substrate material according to the present invention. Silicon (SiO ₂ , SiO)
It is desirable to adjust the composition and amount of the auxiliary agent so that 1% or more is not contained. If silicon oxide is excessively contained in the substrate, a reaction is likely to occur during heat treatment with the piezoelectric / electrostrictive material, and it becomes difficult to control the composition.

By the way, such a ceramic substrate is
Effectively receiving the operating characteristics of the piezoelectric / electrostrictive operating portion formed thereon, in other words, the strain and stress generated there,
In order to effectively perform the opposite operation, the surface roughness represented by Ra is adjusted to be in the range of 0.03 to 0.9 μm. Such adjustment of the surface roughness Ra is also effective in securing the strength of a thin substrate.

In order to form a piezoelectric / electrostrictive operating portion by providing a predetermined electrode film (4, 8) and a piezoelectric / electrostrictive layer 6 on such a ceramic substrate, various known film forming methods are used. Are appropriately adopted, for example, thick film forming techniques such as screen printing, spraying, dipping, and coating, ion beam, sputtering, vacuum deposition, ion plating, and CV.
D, a thin film forming technique such as plating is appropriately selected. In particular, in order to form the film-like piezoelectric / electrostrictive layer (6), a method of forming a thick film by screen printing, spraying, dipping, coating, or the like is suitably adopted. According to this method of forming a thick film, a film can be formed on a ceramic substrate using a paste or a slurry mainly composed of ceramic particles of a piezoelectric / electrostrictive material, and good element characteristics can be obtained. In addition, as the shape of such a film, in addition to pattern formation using a screen printing method, a photolithography method, or the like, a laser processing method, slicing, or a mechanical processing method such as ultrasonic processing is used to remove unnecessary portions. Remove it,
A pattern may be formed.

The structure of the element manufactured here and the shape of the film-shaped piezoelectric / electrostrictive operating portion are not limited at all, and any shape can be adopted according to the application. , A polygon such as a quadrangle, a circle such as a circle, an ellipse, a ring, a comb, a lattice, or a combination of these special shapes.

Each of the films (4, 6, 8) thus formed on the ceramic substrate by the above method.
May be heat-treated to form an integral structure with the substrate each time each film is formed, or heat-treated simultaneously after forming all the films so that each film is simultaneously integrated with the substrate. You may make it combine. Note that when an electrode film is formed by such a film formation technique, heat treatment may not always be required for integration.

Further, the heat treatment temperature for integrating the film thus formed and the substrate is generally 900
° C to 1400 ° C, preferably 10 ° C.
A temperature in the range from 00C to 1400C is advantageously chosen.
When the film-shaped piezoelectric / electrostrictive layer (6) is subjected to a heat treatment, the atmosphere of the piezoelectric / electrostrictive layer (6) may be heated together with the evaporation source of the piezoelectric / electrostrictive material so that the composition of the piezoelectric / electrostrictive layer is not unstable at a high temperature. It is preferable to perform heat treatment while performing control. In addition, a method of firing by placing an appropriate cover member on the piezoelectric / electrostrictive layer (6) so that its surface is not directly exposed to the firing atmosphere. Adoption is also recommended. In this case, a material similar to the substrate is used as the cover member.

The material of the electrode films (4, 8 and the like) constituting the piezoelectric / electrostrictive operating section manufactured by the above-mentioned method is a conductor which can withstand the heat treatment temperature and the high temperature oxidizing atmosphere at about the firing temperature. If it is not particularly limited, for example, it may be a simple metal, an alloy, or a mixture of an insulating ceramic and a metal or an alloy, or even a conductive ceramic. If you do, you can do nothing. However, more preferably, platinum, palladium, high melting point noble metals such as rhodium, or silver-palladium, silver-platinum, an electrode material containing an alloy such as platinum-palladium as a main component is preferably used, among which more preferably Is preferably a cermet material of platinum and a ceramic substrate material, and more preferably a cermet material of platinum, a substrate material and a piezoelectric material. Further, as a material to be added to the electrode, glass is liable to react during heat treatment with the piezoelectric / electrostrictive film, and tends to cause a decrease in actuator characteristics. In addition, as a substrate material to be added to the electrode, 5 to 30
It is preferable that the volume of the piezoelectric material is about 5 to 20% by volume.

An electrode formed using such a conductive material has an appropriate thickness depending on the application. In a type using the transverse effect of electric field induced strain,
Generally, it is formed in a thickness of 20 μm or less, preferably 5 μm or less. On the other hand, in the type using the longitudinal effect of electric field-induced strain, the electrode thickness is desirably 3 μm or more, preferably 10 μm or more, and more preferably 20 μm or more.

Further, the piezoelectric / electrostrictive actuator constituting the piezoelectric / electrostrictive operating section is
As the electrostrictive material, any material can be employed as long as it exhibits an electric field-induced strain such as a piezoelectric or electrostrictive effect. It may be a material, a semiconductor material, a dielectric ceramic material or a ferroelectric ceramic material, or any material that requires a polarization treatment. Unnecessary materials may be used.

However, the piezoelectric / electrostrictive material used in the present invention is preferably a lead zirconate titanate (PZ).
T-based material, Lead magnesium niobate (PMN-based) material, Nickel lead niobate (PNN-based) material, Lead manganese niobate-based material A material containing lead antimonate stannate as a main component, a material containing lead zinc niobate as a main component, a material containing lead titanate as a main component, and a composite material thereof are used. In addition, lanthanum, barium, niobium, zinc, cerium, cadmium,
Materials containing oxides such as chromium, cobalt, antimony, iron, yttrium, tantalum, tungsten, nickel, manganese, lithium, strontium, calcium, bismuth and other compounds as additives, such as PLZT-based materials The PZT system is mainly used
Add the prescribed additives as described above to the ingredients as appropriate
Even those were, what, etc. no problem. Note that the addition of a glass material should be avoided. Because the above piezoelectric /
This is because the electrostrictive material easily reacts with the glass, so that it is difficult to control the composition of the piezoelectric / electrostrictive film to a desired one, which causes variation and deterioration of the actuator characteristics.

Among these piezoelectric / electrostrictive materials, it is composed of lead magnesium niobate, lead zirconate and lead titanate.
The material whose main component is or lead nickel niobate, lead magnesium niobate, lead zirconate and lead titanate
Preferred is a material mainly composed of a component consisting of , more particularly, among them, lead magnesium niobate and lead zirconate.
A material mainly composed of a component consisting of lead titanate is less likely to segregate due to less reaction with the substrate material during the heat treatment, and a treatment for maintaining the composition can be suitably performed. It is advantageously used in combination with having a high piezoelectric constant, such as easy to obtain the composition and crystal structure to be used, when forming a piezoelectric / electrostrictive film by a thick film forming technique such as screen printing, spraying, dipping, coating, etc. Recommended as a material. In the case of a multi-component piezoelectric / electrostrictive material, the piezoelectric characteristics change depending on the composition of the components. However, in the three-component material of lead magnesium niobate-lead zirconate-lead titanate suitably employed in the present invention, The composition is preferably in the vicinity of the phase boundary of pseudocubic-tetragonal-rhombohedral. Particularly, lead magnesium niobate: 15 mol% to 50 mol%, lead zirconate: 10 mol% to 45 mol%, lead titanate: A composition of 30 mol% to 45 mol% is advantageously employed because it has a high piezoelectric constant and an electromechanical coupling coefficient.

The thickness of the piezoelectric / electrostrictive operating portion composed of the electrode film and the piezoelectric / electrostrictive film (layer) formed as described above is generally set to 100 μm or less. The thickness of the strain film is preferably 50 μm or less, more preferably 3 μm or more and 40 μm or less, in order to obtain a large displacement or the like at a low operating voltage.

Table 1 below shows various characteristics of an actuator manufactured using substrates made of various materials having different crystal phases. When manufacturing the actuator,
As the shape of the substrate, as shown in FIG.
a) and the thin and thick portion (16)
a) The thickness was 10 μm. Also, the piezoelectric / electrostrictive operating section contains lead magnesium niobate, lead zirconate and titanate.
A piezoelectric / electrostrictive material containing a lead component as a main component was used, screen-printed to a thickness of 30 μm, and heat-treated at 1000 ° C. or higher. The size of the thin thick part is 0.8 mm × 3 mm. The measurement of the breaking strength was performed by applying a load to the center of the thin-walled portion vertically with a probe having an area of 0.3 mmφ. The displacement of the actuator is a numerical value when DC 30 V is applied.

[0044]

[Table 1]

As is evident from the results in the table, partially stabilized zirconium oxide having a predetermined crystal phase does not react with the piezoelectric / electrostrictive material as compared with other substrate materials, and acts as an actuator. Is large, and shows high mechanical strength even with a thinner plate thickness.

The same experiment as described above was conducted by changing the surface roughness Ra of the substrate in various ways. The results are shown in Table 2 below. From the results in Table 2, the surface roughness of the substrate:
Those having Ra in the range of 0.03 to 0.9 μm show excellent characteristics.

[0047]

[Table 2]

Although the present invention has been described in detail with reference to some embodiments, the present invention is not construed as being limited to the above-described embodiments, and departs from the scope of the present invention. Unless otherwise stated, various changes, modifications,
It should be understood that improvements and the like can be made.

[Brief description of the drawings]

FIG. 1 is a partial perspective view showing one embodiment of a piezoelectric / electrostrictive film element according to the present invention.

FIG. 2 is a perspective partial explanatory view showing another embodiment of the piezoelectric / electrostrictive film type device according to the present invention.

FIG. 3 is a partial perspective view showing still another embodiment of the piezoelectric / electrostrictive film element according to the present invention.

FIG. 4 is a partial perspective view showing still another embodiment of the piezoelectric / electrostrictive film element according to the present invention.

FIG. 5 is a partial perspective view showing another embodiment of the piezoelectric / electrostrictive film element according to the present invention.

FIG. 6 is a partial perspective view showing another example of the piezoelectric / electrostrictive film type device according to the present invention.

FIG. 7 is a partial perspective view showing still another embodiment of the piezoelectric / electrostrictive film element according to the present invention.

FIG. 8 is a partial perspective view showing another embodiment of the piezoelectric / electrostrictive film type device according to the present invention.

FIG. 9 is a partial perspective view showing still another embodiment of the piezoelectric / electrostrictive film element according to the present invention.

FIG. 10 is a partial perspective view showing still another embodiment of the piezoelectric / electrostrictive film element according to the present invention.

FIG. 11 is a partial perspective view showing another still another embodiment of the piezoelectric / electrostrictive film type device according to the present invention.

FIG. 12 is a partial perspective view showing a back surface of a modified example of the piezoelectric / electrostrictive film type device shown in FIG. 11;

13 is a view showing the piezoelectric / electrostrictive film type device shown in FIG. 12; FIG.
FIG. 2 is a perspective partial explanatory view corresponding to FIG.

[Explanation of symbols]

 2, 16 Ceramic substrate 4 First electrode film 6, 22 Piezoelectric / electrostrictive layer 8 Second electrode film 10, 18 Strip electrode film 12 Electrode connection part 14a, 14b Comb electrode film 16a Thin thick part 20 Electrode film 24 Slit 26 rectangular hole

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-175569 (JP, A) JP-A-1-138988 (JP, A) JP-A-4-12678 (JP, A) 97437 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C04B 35/48 H01L 41/09

Claims (4)

(57) [Claims] 1. A piezoelectric / electrostrictive element comprising a thin ceramic substrate and a piezoelectric / electrostrictive operating portion provided on the ceramic substrate and including an electrode and a piezoelectric / electrostrictive layer. While the electrostriction actuating portion is formed by a film forming method, the ceramic substrate partially stabilizes the crystal phase by containing at least one compound selected from the group consisting of yttrium oxide, cerium oxide, magnesium oxide and calcium oxide. And the crystal phase is mainly a tetragonal crystal, or a material mainly composed of zirconium oxide composed of a mixed crystal including at least two or more crystal phases of a tetragonal crystal, a cubic crystal, and a monoclinic crystal. And the surface roughness Ra of such a ceramic substrate is:
A piezoelectric / electrostrictive film element, wherein the thickness is in the range of 0.03 to 0.9 μm. 2. The ceramic substrate is made of a material containing zirconium oxide as a main component partially stabilized with the yttrium oxide, and the content of the yttrium oxide is 2 mol% or more and 7 mol% or less. The piezoelectric / electrostrictive film type device according to claim 1, wherein: 3. The ceramic substrate is made of a material mainly composed of zirconium oxide partially stabilized with cerium oxide, and the content of cerium oxide is at least 6 mol% and at most 15 mol%. The piezoelectric / electrostrictive film type device according to claim 1, wherein: 4. The ceramic substrate is made of a material mainly composed of zirconium oxide partially stabilized with the magnesium oxide or calcium oxide, and the content of the magnesium oxide or calcium oxide is 5 mol% or more and 12 mol or less. % Or less.
3. The piezoelectric / electrostrictive film type element according to item 1.