JP2003309298A - Piezoelectric/electrostrictive element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric/electrostrictive element exhibiting excellent strength, impact resistance, handling performance, dimensional accuracy, positional accuracy, the stability of element characteristics, and a manufacturing yield in which even a thin element having a large area can be prevented from being deformed or damaged. <P>SOLUTION: The piezoelectric/electrostrictive element comprises piezoelectric/ electrostrictive thin films 2A, 2B, 2C and 2D each having a rectangular plane where the width dimension a (mm) and the depth dimension b (mm) of the external shape satisfy a relation a+b<100, and inner electrode layers 3A, 3B and 3C provided to sandwich the piezoelectric/electrostrictive thin films 2A, 2B, 2C and 2D. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric / electrostrictive element, and more particularly to a piezoelectric / electrostrictive element that is thin and is not easily damaged, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, in various fields such as optics, magnetic recording, precision processing, and printing, for example, the optical path length and position are controlled in the submicron order, and a thin and small area is used for precisely controlling vibration. There is a demand for such displacement elements. As a displacement element that meets this demand, there is one that utilizes displacement due to an inverse piezoelectric effect or an electrostrictive effect that occurs when a voltage is applied to a piezoelectric / electrostrictive material such as a ferroelectric substance.

Conventionally, as this type of thin displacement element having a small area, there is a laminated piezoelectric / electrostrictive element. This piezoelectric / electrostrictive element is formed by alternately stacking a plurality of piezoelectric / electrostrictive layers and electrode layers. In order to manufacture such a piezoelectric / electrostrictive element,
First, the raw materials are weighed, crushed and mixed with a binder,
After defoaming, the sheet is formed into a rectangular green sheet (fired to form a piezoelectric / electrostrictive ceramic layer).
Is a predetermined shape. A conductive paste is printed over a predetermined area on one surface of the green sheet to form an electrode layer. Next, a green sheet on which this electrode layer is appropriately printed is laminated and pressure-bonded, and if necessary, cut to form a piezoelectric /
The electrostrictive element precursor is fired to produce a laminated body. As a result, the green sheet is fired to form the piezoelectric ceramic layer as described above, and the piezoelectric / electrostrictive element is manufactured by appropriately forming the external electrodes on the piezoelectric ceramic layer.

In order to manufacture a unimorph type actuator using the laminated piezoelectric / electrostrictive element having such a structure,
After the piezoelectric / electrostrictive element is bonded and fixed on the vibration plate, the outer shape may be processed into a predetermined size.

[0005]

However, in the unimorph type actuator using the above-mentioned laminated piezoelectric / electrostrictive element, since the laminated piezoelectric / electrostrictive element has a small area, it is necessary to process it after assembling. In addition, the yield was low and the raw material yield was low. Usually, lead compounds are often used for piezoelectric / electrostrictive materials, and
There is a problem that a large amount of waste containing a large amount of lead is generated, and the cost of processing the waste increases.

Further, in the manufacture of a unimorph type actuator using a laminated piezoelectric / electrostrictive element, the fired laminated piezoelectric / electrostrictive ceramic is handled and conveyed / assembled.

However, the conventional piezoelectric / electrostrictive ceramic is
Fracture toughness was low and handling was difficult. For this reason, it is difficult to manufacture a piezoelectric / electrostrictive element using a master of a thin, large-area piezoelectric / electrostrictive element. The piezoelectric / electrostrictive element produced by firing a precursor of a thin-walled, small-area piezoelectric / electrostrictive element as in the prior art has a problem that the central portion and the peripheral portion have different characteristics. The reason why the characteristics are different as described above is that, as the piezoelectric / electrostrictive material, there are many lead compounds whose composition easily changes during firing, so that the composition may change between the central portion and the peripheral portion of the piezoelectric / electrostrictive element precursor. Probably the cause. For this reason, in the above-mentioned thin piezoelectric / electrostrictive element having a small area, the final characteristics are likely to vary.

The present invention has been made to solve the above problems. Therefore, the present invention provides a piezoelectric / electrical device that can prevent deformation and damage even with a thin wall and a large area and is excellent in strength, impact resistance, handleability, dimensional accuracy, position accuracy, element characteristic stability, and raw material yield. It is an object of the present invention to provide a strain element and a manufacturing method thereof.

[0009]

In order to solve the above-mentioned problems, the first feature of the present invention is that the plane has a rectangular shape, and the width dimension a (mm) and the depth dimension b (mm) of the outer shape are the same. , A +
It is a gist to provide a piezoelectric / electrostrictive thin film satisfying the relationship of b <100 and at least a pair of electrodes provided so as to sandwich the piezoelectric / electrostrictive thin film. Particularly, in the present invention, the width dimension a (mm) and the depth dimension b (m) of the outer shape are
m) is preferably a + b <70, more preferably a + b <40.

With such a structure, it is possible to obtain a thin piezoelectric / electrostrictive element with a low defect rate.

In the invention according to the first feature, the piezoelectric /
The thickness t of the electrostrictive thin film is 0.3 mm or less, preferably 0.2 mm or less, more preferably 0.15 mm or less. By setting such a thickness dimension, the displacement characteristic of the piezoelectric / electrostrictive element can be reliably obtained.

Further, in the invention according to the first feature, the number of laminated piezoelectric / electrostrictive thin films is 15 or less, preferably 10 or less,
It is more preferably 5 or less. With such a structure, it is possible to suppress dielectric breakdown during use of the piezoelectric / electrostrictive element.

In the invention according to the first feature, it is preferable that at least one layer of the electrode is a cermet, particularly a cermet made of a piezoelectric / electrostrictive ceramic and a metal such as Pt, Ag, Pd or Ni. By forming the electrode with the cermet in this way, it is possible to reduce the difference in thermal expansion between the electrode and the piezoelectric / electrostrictive thin film, and the internal difference caused by the temperature difference between the firing temperature and the actual use temperature (near room temperature) It has the effect of suppressing peeling due to stress, and can improve the reliability of the piezoelectric / electrostrictive element, and can suppress the decrease in electric field induced strain of the piezoelectric / electrostrictive element due to internal stress. In addition, since the relative volume of a metal such as Pt, Ag, Pd, or Ni, which does not generate distortion even when a voltage is applied, to the piezoelectric / electrostrictive element is reduced, the displacement of the piezoelectric / electrostrictive element can be increased. it can.

A second feature of the present invention is that in a piezoelectric / electrostrictive device provided with a diaphragm having a diaphragm fixing portion, the piezoelectric / electrostrictive device is fixed to the diaphragm and at least one piezoelectric / piezoelectric layer is used.
It is a thin piezoelectric / electrostrictive element having an electrostrictive layer and at least two electrode layers, and the summary is that the average particle size of the surface of the piezoelectric / electrostrictive layer is 30 μm or less.

In the second aspect of the invention, the fracture toughness is improved by setting the average grain size on the surface of the piezoelectric / electrostrictive layer to 30 μm or less, and the impact is transmitted to the piezoelectric / electrostrictive device during handling. It has the effect of suppressing damage from occurring in the event of damage.

In the invention according to the second feature, the piezoelectric /
The average particle size on the surface of the electrostrictive layer is preferably 20 μm or less, more preferably 10 μm or less. By setting the material particle size on the surface of the piezoelectric / electrostrictive layer to 20 μm or less, it is possible to suppress the occurrence of breakage when the piezoelectric / electrostrictive element is driven or when a thermal shock is applied. Especially, the material grain size on the surface of the piezoelectric / electrostrictive layer is set to 1
By setting the thickness to 0 μm or less, in addition to the above-mentioned action, there is an action of suppressing the occurrence of dielectric breakdown even under high humidity.

In the invention according to the second feature, the piezoelectric /
The ratio of the thickness of the electrostrictive element to the thickness of the diaphragm is 0.5 to 1
0, the ratio of the length of the piezoelectric / electrostrictive element to the length of the vibration plate fixing portion is 1.25 or more, and the width is preferably 0.8 mm or more. The ratio of the thickness to the thickness of the diaphragm is preferably 0.8-5, more preferably 1-3.
Is. With such a configuration, it becomes easy to follow the waviness of the diaphragm when assembled with the diaphragm, the thickness of the adhesive becomes constant regardless of the part, and the variation in displacement characteristics of the piezoelectric / electrostrictive device is reduced. There is.

Further, in the invention according to the second feature, the ratio of the length of the piezoelectric / electrostrictive element to the length of the diaphragm fixing portion is:
It is preferably 2 or more, and more preferably 3 or more.

In the invention according to the second feature, the piezoelectric /
The width dimension of the electrostrictive element is preferably 1.5 mm or more. In this way, by setting the width dimension to be 1.5 mm or more, it is possible to obtain many portions in which the composition variation during firing of the piezoelectric / electrostrictive element is small, so that the manufacturing efficiency can be improved.

Further, in the invention according to the second feature, it is desirable that the number of piezoelectric / electrostrictive layers is 15 or less, preferably 1 to 10 layers, more preferably 2 to 8 layers. With such a stacking number, there is an effect of suppressing dielectric breakdown. That is, when the number of laminated piezoelectric / electrostrictive layers is more than 15, the electrode length in the piezoelectric / electrostrictive element becomes long and the distance between the electrodes becomes short, so that dielectric breakdown occurs when a voltage is applied. It will be easier. Also, the number of laminated piezoelectric / electrostrictive layers is 1
By setting it to 0 or less, sufficient displacement can be secured.

In the second aspect of the invention, it is preferable that at least one of the electrode layers is a cermet. With such a structure, peeling or reduction in displacement due to the difference in thermal expansion between the electrode material and the piezoelectric / electrostrictive material is suppressed, and the reliability of the piezoelectric / electrostrictive element is improved. Further, by using the cermet, the volume of the metal portion of the piezoelectric / electrostrictive element that is not distorted even when an electric field is applied can be reduced, and thus the displacement of the piezoelectric / electrostrictive element can be increased.

A third feature of the present invention is a method for manufacturing a piezoelectric / electrostrictive element, which comprises forming an adhesion preventing layer which disappears by heat treatment on a ceramic substrate, and then screen printing on the adhesion preventing layer. Is used to form a piezoelectric / electrostrictive element precursor,
After that, the main point is to bake the piezoelectric / electrostrictive element precursor.

In the invention of the third feature, the ceramic substrate may be a fired piezoelectric / electrostrictive material layer or an unfired piezoelectric / electrostrictive material layer. Further, this ceramic substrate may have a two-layer structure of a fired ceramic material layer which is not a piezoelectric / electrostrictive material and a fired piezoelectric / electrostrictive material layer. Further, the ceramic substrate may have a two-layer structure including an unfired ceramic material layer which is not a piezoelectric / electrostrictive material and an unfired piezoelectric / electrostrictive material layer. Furthermore, a two-layer structure of a fired ceramic material layer which is not a piezoelectric / electrostrictive material and an unfired piezoelectric / electrostrictive material layer is preferable. The piezoelectric / electrostrictive material layer of the ceramic substrate may be formed by a green sheet forming method or a screen printing method. Then, it is preferable to dispose a plurality of piezoelectric / electrostrictive element precursors on the ceramic substrate.

In the invention according to the third feature, it is preferable that the adhesion preventing layer is made of a substance that sublimes. If the anti-adhesion layer is a substance that becomes a liquid phase before vaporizing and evaporating, the piezoelectric /
When the electrostrictive element precursor is partially melted, a defective shape occurs in the piezoelectric / electrostrictive element after firing, or the melted portion of the piezoelectric / electrostrictive element precursor adheres to the ceramic substrate, which results in firing. While the later piezoelectric / electrostrictive element is fixed to the ceramic substrate, by using a sublimable substance,
The above problem does not occur because the anti-adhesion layer can be eliminated during melting without melting.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, details of a piezoelectric / electrostrictive element and a method of manufacturing the same according to the present invention will be described based on an embodiment shown in the drawings. However, the drawings are schematic,
The thickness and size of each material layer should be determined with reference to the following description. Moreover, it is needless to say that the drawings may include portions having different dimensional relationships and ratios.

Here, the piezoelectric / electrostrictive element in the present invention is a concept including an element which mutually converts electrical energy and mechanical energy by an inverse piezoelectric effect and an electrostrictive effect or a piezoelectric effect. Therefore, it is used not only as an active element such as various actuators and vibrators, but especially as a displacement element utilizing displacement due to an inverse piezoelectric effect or an electrostrictive effect, and also as a sensor utilizing electromotive force due to a piezoelectric effect.

[Embodiment] (Piezoelectric / electrostrictive element) FIG. 1 is a perspective view showing a state in which the piezoelectric / electrostrictive element 1 according to the first embodiment is placed upside down. As shown in FIG. 1, the piezoelectric /
The electrostrictive element 1 includes, for example, four piezoelectric / electrostrictive layers 2A, 2B,
2C, 2D and these piezoelectric / electrostrictive layers 2A, 2B, 2
For example, three internal electrode layers 3A, 3B, 3C interposed between the adjacent layers C, 2D and a pair of external electrode layers 4A in which these internal electrode layers 3A, 3B, 3C are alternately connected. And 4B. The piezoelectric / electrostrictive element 1 has a substantially trapezoidal laminated structure in which the pair of upper and lower bottom surfaces are both rectangular.

In the piezoelectric / electrostrictive element 1 according to this embodiment, the piezoelectric / electrostrictive layers 2A, 2B, 2C and 2D are made of any material as long as they exhibit electric field induced strain such as piezoelectric or electrostrictive effect. It may be a material, or may be a dielectric ceramic material or a ferroelectric ceramic material without any problem. Further, it may be a material that needs polarization treatment, or it may be an unnecessary material. , Preferably a material containing lead zirconate titanate (PZT type) as a main component, a material containing lead magnesium niobate (PMN type) as a main component,
A material whose main component is lead nickel niobate (PNN),
Material containing lead zinc niobate as a main component, material containing lead manganese niobate as a main component, material containing lead antimony stannate as a main component, material containing lead titanate as a main component, and barium titanate as a main component. The material to be used, and a composite material of these materials are used. In addition, the material which has PZT system as a main component,
A material containing oxides of lanthanum, barium, niobium, zinc, nickel, manganese, etc., or other compounds thereof as additives, for example, a PLZT-based material, is appropriately added with predetermined additives. It doesn't matter. In addition, the internal electrode layers 3A, 3B, 3C and the external electrode layer 4
A and 4B are formed of cermet. This cermet is a high-melting point metal such as platinum, palladium, rhodium, a metal containing an alloy such as silver-palladium, silver-platinum, platinum-palladium as a main component, lead oxide, titanium oxide, zirconium oxide, magnesium oxide, Niobium oxide, nickel oxide, zinc oxide, manganese oxide, antimony oxide, tin oxide, lanthanum oxide, barium oxide and their compounds, materials containing lead zirconate as a main component, and lead magnesium niobate as a main component Material, a material containing lead nickel niobate as a main component, a material containing lead antimony stannate as a main component, a material containing lead titanate as a main component, or a material containing barium titanate as a main component, or a mixture thereof, is composited. It becomes.

In this piezoelectric / electrostrictive element 1, the piezoelectric / electrostrictive layers 2A, 2B, which are laminated from the bottom surface f1 toward the bottom surface f2,
2C and 2D are set so that the width gradually becomes narrower. As a result, slopes f3 and f4 are formed on both sides in the depth direction of the entire piezoelectric / electrostrictive element 1.

Further, in this piezoelectric / electrostrictive element 1,
The sum a + b of the width dimension a and the depth dimension b shown in FIG. 1 is 10
It is set to be smaller than 0 mm. Furthermore, the thickness t of the piezoelectric / electrostrictive element 1 is set to 0.3 mm or less.

With this setting, the piezoelectric / electrostrictive element 1 according to the present embodiment can obtain desired displacement characteristics with an upper limit of 1σ. Therefore, a + b <1
If the thickness t of the piezoelectric / electrostrictive element 1 is set to 0.3 mm or less under the condition of 00 mm, desired displacement characteristics can be obtained on average when the piezoelectric / electrostrictive element is used. Furthermore, a + b <1
When the thickness t of the piezoelectric / electrostrictive element 1 is set to 0.15 mm or less under the condition of 00 mm, when the piezoelectric / electrostrictive element is used, desired displacement characteristics can be obtained on average at the lower limit of 1σ.

In the piezoelectric / electrostrictive element 1 having such a setting, the number of laminated piezoelectric / electrostrictive layers is equal to that of the piezoelectric / electrostrictive layers 2.
There are four layers A, 2B, 2C, and 2D. In the present embodiment, when a + b <100 mm and the thickness dimension t of the piezoelectric / electrostrictive element 1 is set to 0.3 mm or less, the piezoelectric / electrostrictive element 1
By setting the number of laminated electrostrictive layers to 15 or less, dielectric breakdown of the piezoelectric / electrostrictive layers can be prevented.

In the piezoelectric / electrostrictive element 1 according to the present embodiment, the internal electrode layers 3A, 3B, 3C and the external electrode layers 4A, 4B have the same composition as the ceramics forming the piezoelectric / electrostrictive layer, or Since the cermet, which is a mixture of ceramic and metal having a similar composition, is formed, the ceramic of the cermet and the ceramic of the piezoelectric / electrostrictive layer are sintered to strengthen the bond between the electrode layer and the piezoelectric / electrostrictive layer. In addition, the internal stress caused by the difference in the coefficient of thermal expansion is reduced, and the electrode layers and the piezoelectric / electrostrictive layers 2A, 2B, 2C, and 2D can be prevented from peeling off.

Table 1 below shows the width dimension a (m) of the outer shape of the piezoelectric / electrostrictive element 1 according to this embodiment, as shown in FIG.
m) and the depth dimension b (mm) of the outer shape are gradually changed, showing the defect rate (defect occurrence rate) of the piezoelectric / electrostrictive element 1. In addition, FIG. 2 is a piezoelectric / electrostrictive element 1 based on Table 1 below.
Area where the defective rate is 100%, an area where the defective rate is 0%, and an area where the defective rate is 0 to 100% (the two-dot chain line indicates the defective rate of 50%
% Is shown).

[0035]

[Table 1] From Table 1 and FIG. 2 above, the sum of the width dimension a and the depth dimension b of the outer shape of the piezoelectric / electrostrictive element 1 is shorter than 100 mm (a
It can be seen that when + b <100 mm), the defective rate of the piezoelectric / electrostrictive element 1 is less than 100%. Also, a + b <70
It can be seen that the defective rate of the piezoelectric / electrostrictive element 1 can be lowered when mm, and further, a + b <40 mm.

Further, in the piezoelectric / electrostrictive element 1 according to the present embodiment, the thickness dimension t is set to 0.3 mm or less, but the thickness dimension t is preferably 0.2 mm or less, and more preferably, It is preferably 0.15 mm or less.

Further, under the above-mentioned dimensional conditions, the number of laminated piezoelectric / electrostrictive layers is 4, but as described above, it is 15 or less, preferably 10 or less, and more preferably 5 or less.

[Method for Manufacturing Piezoelectric / Electrostrictive Element] Next, a method for manufacturing the piezoelectric / electrostrictive element 1 according to the present embodiment will be described with reference to FIGS.

(1) First, as shown in FIG. 3, a ceramic substrate 10 of a predetermined size made of an oxide such as zirconia, alumina or magnesia is prepared. The ceramic substrate 10 has a function as a screen printing base and a function as a firing substrate.

(2) Next, on this ceramic substrate,
The piezoelectric / electrostrictive material powder dispersion paste having the same composition as the piezoelectric / electrostrictive layer of the piezoelectric / electrostrictive element 1 is printed on a plurality of rows of regions having a dimension longer than that of the piezoelectric / electrostrictive element 1, and dried, A composition buffer layer is formed.

(3) On the composition buffer layer, carbon powder or theobromine powder dispersion paste which is a subliming substance is printed in the same shape as the piezoelectric / electrostrictive paste and dried to prevent adhesion as shown in FIG. Form the layer 11.

(4) Next, as shown in FIG. 3, a material of platinum-piezoelectric / electrostrictive is formed on the plurality of parallel element forming regions A on the adhesion preventing layer 11 by screen printing. An electrode paste made of the material cermet is used for a part of the external electrode layer 4A (a wide electrode part along the lower surface of the piezoelectric / electrostrictive layer 2A) and a part of the external electrode layer 4B (piezoelectric / electrostrictive layer 2A).
Electrode portion having a small area along the lower surface of the above). After that, by the screen printing method, the piezoelectric / electrostrictive layer 2
Form A. In the piezoelectric / electrostrictive layer 2A shown in FIG. 4, the sum of the width dimension (a) and the depth dimension (b) is 10 as described above.
It is set to be less than 0 mm. And FIG.
As shown in, on the piezoelectric / electrostrictive layer 2A, the internal electrode layer 3A, the piezoelectric / electrostrictive layer 2B,
Internal electrode layer 3B, piezoelectric / electrostrictive layer 2C, internal electrode layer 3C,
The piezoelectric / electrostrictive layer 2D and the external electrode layer 4A are printed and dried repeatedly to produce a laminated body. The screen of the external electrode layer 4A is set so as to cover the inclined side wall of the trapezoidal laminate. Similarly, the internal electrodes 3A, 3B, and 3C are also set so as to cover the side walls of the stacked body.
In FIG. 5, reference numeral 12 indicates a screen (printing plate). The internal electrode layers 3A, 3B, 3C and the external electrode layer 4B are formed of the same Pt-piezoelectric / electrostrictive material cermet as the external electrode layer 4A.

(4) Finally, the temperature is raised at such a rate that the organic components of the respective material layers and the anti-adhesion film 11 are not left, for example, firing is performed at a maximum temperature of 1100 to 1300 ° C. As a result,
As shown in FIG. 6, the adhesion preventing film 11 disappears, and the piezoelectric / electrostrictive element 1 can be easily separated from the ceramic substrate 10 (+ buffer layer).

According to the manufacturing method of the present embodiment described above, the average grain size of the piezoelectric / electrostrictive layer after firing is 30 μm or less, and the fracture toughness is higher than that of the average grain size larger than 30 μm. Has improved. It is considered that this is because if the particle size is large, intragranular fracture is likely to occur.
In the piezoelectric / electrostrictive element 1 manufactured by the manufacturing method according to the present embodiment, since fracture toughness is high, damage due to handling is unlikely to occur and the frequency of occurrence of defects is low.

(Drop Test of Piezoelectric / Electrostrictive Element) In addition, the piezoelectric / electrostrictive element 1 manufactured by the above-described manufacturing method having different average particle diameters of the piezoelectric / electrostrictive material was prepared.
The piezoelectric / electrostrictive elements having different surface grain diameters of the piezoelectric / electrostrictive layers were dropped 10 times on a plate made of SUS304 having a height of 10 cm to a wall thickness of 20 mm, and the capacity decreased by 2% or more was regarded as a defect. FIG. 7 is a graph showing the results of such a drop test, and is a graph showing the average particle size of the piezoelectric / electrostrictive material and the frequency of occurrence of defects (%) in the piezoelectric / electrostrictive element. As can be seen from FIG. 7, the average grain size on the surface of the piezoelectric / electrostrictive layer after firing is 3
When it is larger than 0 μm, the frequency of occurrence of defects is dramatically increased. In other words, the surface grain size of the piezoelectric / electrostrictive layer is 30.
If the thickness is smaller than μm, the frequency of occurrence of defects decreases, and a piezoelectric / electrostrictive element with a low defect rate can be manufactured.

(Displacement Characteristics of Piezoelectric / Electrostrictive Element) Further, similarly to the drop test, piezoelectric / electrostrictive elements having different particle diameters of the piezoelectric / electrostrictive material were prepared, and the respective piezoelectric / electrostrictive elements were changed. 3k
After polarization at V / mm, si at 1 kHz at 0-3 kV / mm
The displacement of the piezoelectric / electrostrictive element was measured after driving for 100 hours with n waves. Then, the one in which the displacement of the piezoelectric / electrostrictive element was reduced by 5% or more was determined to be defective. The result is shown in FIG.

As shown in FIG. 8, the average particle size is 20 μm.
It can be seen that when m or less, the frequency of occurrence of defects is significantly reduced, and a piezoelectric / electrostrictive element having good displacement characteristics can be stably manufactured.

(Durability of Piezoelectric / Electrostrictive Element at High Temperature and High Humidity) Further, similarly to each of the above-mentioned tests, a piezoelectric / electrostrictive element in which the particle size of the piezoelectric / electrostrictive material was changed was prepared and the temperature was 85 ° C. , Humidity 8
In a 5% environment, the displacement of each piezoelectric / electrostrictive element was measured after driving with a sin wave of 1 kHz for 100 hours. Then, the one in which the displacement of the piezoelectric / electrostrictive element changed by 5% or more was determined to be defective. The result is shown in FIG.

As shown in FIG. 9, the average particle size is 10 μm.
It can be seen that when m or less, the frequency of occurrence of defects is significantly reduced, and high temperature and high humidity durability is improved.

(Relationship between Thickness of Piezoelectric / Electrostrictive Element / Thickness of Vibration Plate and Displacement) Next, the piezoelectric / electrostrictive element 1 according to the present embodiment will be described with reference to FIG. The relationship between the thickness t1 of the piezoelectric / electrostrictive element 1 and the vibration plate t2 when fixed to the base portion of the vibration plate 14 fixed to 13 with an adhesive was investigated. First, piezoelectric / electrostrictive elements having various thicknesses were bonded to a vibration plate having a thickness of 100 μm, and the displacement was measured (the maximum displacement is expressed as 100%). FIG. 11 is a graph showing the result. As shown in FIG. 11, the ratio between the thickness of the piezoelectric / electrostrictive element and the thickness of the vibration plate is 0.5 to 10 (preferably 0.5.
Good displacement characteristics can be obtained in the range of 8 to 10, and more preferably 1 to 3. In this displacement measurement,
The thickness of the diaphragm was set to 100 μm, but 50 μm, 1
Similar results were obtained even when the thickness was 50 μm.

(Relationship Between Length of Piezoelectric / Electrostrictive Element / Length of Vibration Plate Fixing Part and Displacement) When the piezoelectric / electrostrictive element 1 is fixed to the diaphragm 14 as shown in FIG. The relationship between the length L2 of the strain element / the length L1 of the diaphragm fixing portion and the displacement was examined. FIG. 12 is a graph showing the result.

As shown in FIG. 12, good displacement characteristics are obtained when the length L2 of the piezoelectric / electrostrictive element / the length L1 of the diaphragm fixing portion is 1.25 or more (preferably 2 or more, more preferably 3 or more). It turns out that it has.

For example, also in the piezoelectric / electrostrictive device 20 having the structure shown in FIG. 18, the length L2 of the piezoelectric / electrostrictive element / the length L1 of the diaphragm fixing portion is 1.25 or more (preferably 2 or more, and more preferably 3 or more), with good displacement characteristics. The piezoelectric / electrostrictive device 20
As shown in FIG. 18, the movable plate portions 31 and 31 that face each other with a predetermined distance are provided between the movable plate portions 31 and 31 on one end side of the movable plate portions 31 and 31. The base 30 is integrally formed with the fixed portion 32 formed so as to be interposed, and the pair of movable plate portions 31, 31 is provided.
Piezoelectric / electrostrictive elements 40 are adhered and fixed to the opposing outer surfaces on the one end side of each.

In this piezoelectric / electrostrictive device 20, the pair of movable plate portions 3 is driven by driving the piezoelectric / electrostrictive elements 40, 40.
The piezoelectric / electrostrictive element 40 detects the displacement of the first and the third members 31 or the displacement of the movable plate members 31 and 31. For example, in the piezoelectric / electrostrictive device 20 shown in FIG. 18, the actuator portion 3 is composed of the movable plate portion 31 and the piezoelectric / electrostrictive element 40.
3, 33 are configured. In addition, the pair of movable plate portions 3
Movable portions 34 and 34 are formed at the other end portions of the reference numerals 1 and 31 so as to project inward from each other. These movable parts 34 are displaced along with the displacement operation of the movable plate part 31. As a result, as shown in FIG. 18, it is possible to drive a component 50 that requires fine position control, such as an optical device, a precision device, or a head of a hard disk drive.

The trapezoidal piezoelectric / electrostrictive element 40 shown in FIG. 18 may be attached to the fixing portion 32 with the top and bottom reversed. Also in the piezoelectric / electrostrictive device having such a structure, the length L2 of the piezoelectric / electrostrictive element / the length L1 of the vibration plate fixing portion is 1.25.
With the above values (preferably 2 or more, more preferably 3 or more), good displacement characteristics are provided.

Further, as shown in FIG. 19, the piezoelectric / electrostrictive elements 40 may be adhered and fixed to the opposite side surfaces of the pair of movable plates 31, 31 at the other end side. In the piezoelectric / electrostrictive device having such a configuration,
Piezoelectric / electrostrictive element length L2 / movable portions 34, 34 length L
When 3 is 1.25 or more (preferably 2 or more, more preferably 3 or more), good displacement characteristics are provided.

(Relationship between Width of Piezoelectric / Electrostrictive Element and Displacement) The piezoelectric / electrostrictive element having the above-mentioned structure was sliced in the width direction to measure the displacement. As a result, the result shown in FIG. 13 was obtained. Since the displacement characteristics are low (or cause variations) at both ends of about 0.7 mm, it is desirable that the width is at least 1.5 mm or more and that the location where the displacement characteristics are stable is used. In addition, as a result of a composition analysis by an electron probe microanalyzer (EPMA), it was found that the composition of the portions with low displacements at both ends varied. From these results, if a master of a thin-walled, large-area piezoelectric / electrostrictive element is produced and the precursor of the piezoelectric / electrostrictive element is cut out from the area excluding the peripheral portion from this master, many piezoelectric / electrostrictive elements can be obtained. A device precursor can be taken.

(Relationship Between Number of Piezoelectric / Electrostrictive Layers, Displacement Characteristics, and Failure Rate) The displacement and failure rate were measured while the number of layers of the piezoelectric / electrostrictive element was gradually changed. The result is shown in the graph of FIG. It has been found that the number of piezoelectric / electrostrictive layers is preferably 15 or less, preferably 10 or less, and more preferably 5 or less under the above-described dimensional conditions of the present embodiment.

Although the first embodiment has been described above, the green sheet laminating method may be used in the manufacture of the piezoelectric / electrostrictive element 1 in the present embodiment.

[Other Embodiments] (Piezoelectric / Electrostrictive Element) The embodiments of the present invention have been described above. However, the description and drawings forming part of the disclosure of the above embodiments limit the present invention. It should not be understood as a thing. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

For example, in the above-described embodiment, the piezoelectric / electrostrictive element 1 having a trapezoidal cross section has been described by applying the present invention. However, a rectangular parallelepiped piezoelectric / electrostrictive element as shown in FIGS. The present invention can also be applied to 20. This piezoelectric / electrostrictive element 20 has a piezoelectric / electrostrictive element 20 as shown in FIG.
A laminated body 23 in which the electrostrictive layers 21 and the electrode layers 22 are alternately laminated, and the electrode layers 22 are alternately connected in common on two side surfaces of the laminated body 23 facing each other, and It is provided with a pair of external electrode layers 24 and 25 which are formed to extend on the upper and lower surfaces and are electrically separated from each other. In this piezoelectric / electrostrictive element 20, six piezoelectric / electrostrictive layers 21 are laminated in the thickness direction, and seven layers of electrodes including the external electrode layers 24 and 25 are alternately laminated. This piezoelectric / electrostrictive element 20
Also in the above, by setting the dimensions similar to those of the above-described embodiment, the defect occurrence rate is reduced and the fracture toughness is improved,
It is possible to improve the displacement characteristics.

(Method for Manufacturing Piezoelectric / Electrostrictive Element) In order to manufacture such a piezoelectric / electrostrictive element 20, first, as shown in FIG. 16, firing with the same composition as the piezoelectric / electrostrictive layer 21 is performed. An adhesion preventing film 31 similar to that of the above-described first embodiment is formed on the formed ceramic substrate 30. Thereafter, a green sheet of piezoelectric / electrostrictive material having an electrode layer formed on the surface thereof is sequentially laminated to form a laminated body, and the laminated body (piezoelectric / electrostrictive element precursor) is fired together with the ceramic substrate 30. I'll do it. Also in the present embodiment, the adhesion prevention film 31 disappears by firing, and the piezoelectric / electrostrictive element 20 can be separated from the ceramic substrate 30.

In the present embodiment, since the ceramic substrate 30 that functions as a base during firing is formed of the piezoelectric / electrostrictive material, the components on the substrate side diffuse into the piezoelectric / electrostrictive layer 21 to cause the piezoelectric / electrostrictive layer 21. It is possible to prevent the characteristics of the electrostrictive element 20 from being affected.

In the present embodiment, the green sheet laminating method is used when forming the laminated body, but it may be formed by the screen printing method as in the above-mentioned embodiments.

Further, in the present embodiment, the ceramic substrate 30 used as a base during firing is formed by firing a piezoelectric / electrostrictive material, but is made of an unfired piezoelectric / electrostrictive material. It may be used as a substrate. Furthermore, FIG.
As shown in FIG. 3, the ceramic substrate 30 may have a two-layer structure including a fired ceramic material layer 32 which is not a piezoelectric / electrostrictive material and a fired or unfired piezoelectric / electrostrictive material layer 33. . In the piezoelectric / electrostrictive element 20 according to such another embodiment as well, the same dimension setting and piezoelectric / electrostrictive element 1 as those of the piezoelectric / electrostrictive element 1 according to the above-described embodiment are performed.
The setting of the number of electrostrictive layers can be applied, and the same result can be obtained.

[0066]

As is apparent from the above description, according to the present invention, it is possible to reliably obtain a thin piezoelectric / electrostrictive element with a low defect rate.

Further, according to the present invention, it is possible to realize a piezoelectric / electrostrictive element having a desired displacement characteristic.

Furthermore, it is possible to provide a piezoelectric / electrostrictive element in which dielectric breakdown is unlikely to occur during use.

Further, according to the present invention, peeling between the electrode and the piezoelectric / electrostrictive thin film can be suppressed and the reliability of the piezoelectric / electrostrictive element can be improved.

Further, according to the present invention, a piezoelectric / electrostrictive element having good fracture toughness (handling property) can be realized, and there is an effect of suppressing deformation or damage due to handling. In addition, there is an effect of suppressing the occurrence of breakage when the piezoelectric / electrostrictive element is driven or when a thermal shock is applied. And
According to the present invention, it is possible to manufacture a piezoelectric / electrostrictive element in which dielectric breakdown is unlikely to occur even under high humidity.

Further, according to the present invention, there is an effect of reducing variation in displacement characteristics of the piezoelectric / electrostrictive device.

Furthermore, according to the present invention, a large number of piezoelectric / electrostrictive elements having good displacement characteristics can be obtained, and manufacturing efficiency can be improved.

Further, according to the present invention, a piezoelectric / electrostrictive element having a good displacement characteristic can be realized.

Further, according to the present invention, by using the cermet as the electrode layer, it is possible to prevent the electrode material and the piezoelectric / electrostrictive material from being separated from each other, and improve the reliability of the piezoelectric / electrostrictive element. It is possible to reduce internal stress and suppress a decrease in displacement. In addition, since the cermet has a small volume of the metal member that does not displace when a voltage is applied, the relative displacement between the piezoelectric / electrostrictive layer and the electrode becomes large. Therefore, the displacement of the piezoelectric / electrostrictive element can be increased.

Further, according to the present invention, since the adhesion preventing layer is made of a substance that sublimes, the adhesion preventing layer can be eliminated during firing and the piezoelectric / electrostrictive element can be easily removed from the ceramic substrate. Further, it is possible to prevent impurities from diffusing from the ceramic substrate to the piezoelectric / electrostrictive element side, and it is possible to manufacture a piezoelectric / electrostrictive element having proper characteristics.

[Brief description of drawings]

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

FIG. 2 is a graph showing a relationship between a width dimension, a depth dimension, and a defect occurrence rate of a piezoelectric / electrostrictive element.

FIG. 3 is a plan view showing a state in which an adhesion prevention film is attached to a ceramic substrate in the method for manufacturing a piezoelectric / electrostrictive element according to the embodiment.

FIG. 4 is a plan view showing a piezoelectric / electrostrictive layer of the piezoelectric / electrostrictive element according to the present embodiment.

5A to 5C are cross-sectional explanatory views showing the steps of the method for manufacturing the piezoelectric / electrostrictive element according to the present embodiment.

FIG. 6 is a cross-sectional explanatory view showing a step of the method for manufacturing the piezoelectric / electrostrictive element according to the present embodiment.

FIG. 7 is a graph showing the relationship between the average grain size of the piezoelectric / electrostrictive material of the piezoelectric / electrostrictive element according to the present embodiment and the defect occurrence frequency by the drop test.

FIG. 8 is a graph showing the occurrence frequency of defects in a voltage application test of a piezoelectric / electrostrictive element in which the average particle diameter of the piezoelectric / electrostrictive material of the piezoelectric / electrostrictive element according to the present embodiment is changed.

FIG. 9 shows a piezoelectric / electrostrictive element in which the particle size of the piezoelectric / electrostrictive material is changed, at 1 kHz in an environment of a temperature of 85 ° C. and a humidity of 85%.
5 is a graph showing the results of measuring the displacement of each piezoelectric / electrostrictive element after driving with the sin wave for 100 hours.

FIG. 10 is an explanatory diagram showing a state where a piezoelectric / electrostrictive element is bonded to a vibration plate fixed to a vibration plate fixing portion.

FIG. 11 is a graph showing the relationship between the ratio of the thickness dimension of the piezoelectric / electrostrictive element to the thickness dimension of the diaphragm and the displacement according to the present embodiment.

FIG. 12 is a graph showing the relationship between the ratio of the length of the piezoelectric / electrostrictive element to the length of the diaphragm fixing portion and the displacement according to the present embodiment.

FIG. 13 is a graph showing the relationship between the position in the width direction and the displacement of the piezoelectric / electrostrictive element according to the present embodiment.

FIG. 14 is a diagram showing a piezoelectric / electrostrictive element of the present embodiment;
It is a graph which shows the relationship between the number of electrostrictive layers and displacement.

FIG. 15 is a perspective view of a piezoelectric / electrostrictive element according to another embodiment.

FIG. 16 is a cross-sectional view showing the manufacturing process of the piezoelectric / electrostrictive element according to another embodiment.

FIG. 17 is a cross-sectional view showing the manufacturing process of the piezoelectric / electrostrictive element according to another embodiment.

FIG. 18 is a plan view of a piezoelectric / electrostrictive device according to another embodiment.

FIG. 19 is a plan view of a piezoelectric / electrostrictive device according to another embodiment.

[Explanation of symbols]

1, 20 Piezoelectric / electrostrictive element 2A, 2B, 2C, 2D, 21 Piezoelectric / electrostrictive layer 3A, 3B, 3C, 22 Internal electrode layers 10, 30 Ceramic substrate 11,31 Anti-adhesion film 13 Vibration plate fixing part 14 diaphragm

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01L 41/18 101D (72) Inventor Masaki Iwamoto 2-56 Sudacho, Sudacho, Mizuho-ku, Aichi Prefecture Nagoya, Japan Within the corporation

Claims (32)

[Claims] 1. The plane has a rectangular shape, and the width dimension a of the outer shape.
(Mm) and the depth dimension b (mm) are a + b <100
2. A piezoelectric / electrostrictive element, comprising: a piezoelectric / electrostrictive thin film satisfying the above relationship; and at least a pair of electrodes provided so as to sandwich the piezoelectric / electrostrictive thin film. 2. The piezoelectric / electrostrictive element according to claim 1, wherein a + b <70. 3. The piezoelectric / electrostrictive element according to claim 1, wherein a + b <40. 4. The piezoelectric / electrostrictive device according to claim 1, wherein the piezoelectric / electrostrictive thin film has a thickness t of 0.3 mm or less. Piezoelectric / electrostrictive element. 5. The piezoelectric / electrostrictive element according to claim 4, wherein a thickness t of the piezoelectric / electrostrictive thin film is 0.2 mm or less. 6. The piezoelectric / electrostrictive element according to claim 4, wherein the piezoelectric / electrostrictive thin film has a thickness t of 0.15 mm or less. 7. The piezoelectric / electrostrictive element according to claim 1, wherein the number of stacked piezoelectric / electrostrictive thin films is 15 or less. Distortion element. 8. The piezoelectric / electrostrictive element according to claim 7, wherein the number of stacked piezoelectric / electrostrictive thin films is 10 or less. 9. The piezoelectric / electrostrictive element according to claim 7, wherein the number of stacked piezoelectric / electrostrictive thin films is 5 or less. 10. The piezoelectric / electrostrictive element according to any one of claims 1 to 9, wherein at least one layer of the electrode is a cermet. 11. A piezoelectric / electrostrictive device in a piezoelectric / electrostrictive device including a diaphragm having a diaphragm fixing portion, the piezoelectric / electrostrictive layer being at least one layer, and at least two electrode layers. A thin-walled piezoelectric / electrostrictive element having: a piezoelectric / electrostrictive element having an average particle size of 30 μm or less on the surface of the piezoelectric / electrostrictive layer. 12. The piezoelectric / electrostrictive element according to claim 11, wherein the average particle diameter of the surface of the piezoelectric / electrostrictive layer is 20 μm or less. 13. The piezoelectric / electrostrictive element according to claim 11, wherein the average particle diameter of the surface of the piezoelectric / electrostrictive layer is 10 μm or less. 14. The piezoelectric / electrostrictive element according to claim 11, wherein a ratio of the thickness of the diaphragm to the thickness of the diaphragm is 0.5 to 10, and the diaphragm is fixed. A piezoelectric / electrostrictive element having an outer shape with a ratio of length to part length of 1.25 or more and a width of 0.8 mm or more. 15. The piezoelectric / electrostrictive element according to claim 11, wherein the thickness ratio of the diaphragm to the thickness of the diaphragm is 0.8 to 5. Piezoelectric / electrostrictive element. 16. The piezoelectric / electrostrictive element according to claim 11, wherein a ratio of the thickness of the diaphragm to the thickness of the diaphragm is 1 to 3. Piezoelectric / electrostrictive element. 17. The piezoelectric / electrostrictive element according to claim 11, wherein a ratio of the length to the length of the diaphragm fixing portion is 2 or more. Piezoelectric / electrostrictive element. 18. The piezoelectric / electrostrictive element according to claim 11, wherein a ratio of a length to a length of the diaphragm fixing portion is 3 or more. Piezoelectric / electrostrictive element. 19. The piezoelectric / electrostrictive element according to any one of claims 11 to 16, wherein the width dimension is 1.5 mm or more. 20. The piezoelectric / electrostrictive element according to claim 11, wherein the piezoelectric / electrostrictive layer is 15 layers or less. . 21. The piezoelectric / electrostrictive element according to any one of claims 11 to 19, wherein the piezoelectric / electrostrictive layer is 1 to 10 layers. element. 22. The piezoelectric / electrostrictive element according to claim 11, wherein the piezoelectric / electrostrictive layer is 2 to 8 layers. element. 23. The piezoelectric / electrostrictive element according to any one of claims 11 to 22, wherein at least one layer of the electrode layers is a cermet. 24. After forming an adhesion preventing layer which disappears by heat treatment on a ceramic substrate, a piezoelectric / electrostrictive element precursor is formed on the adhesion preventing layer by a screen printing method, and then the piezoelectric / electrostrictive element precursor is formed. A method for manufacturing a piezoelectric / electrostrictive element, which comprises firing an electrostrictive element precursor. 25. The method for manufacturing a piezoelectric / electrostrictive element according to claim 24, wherein the ceramic substrate is formed of a fired piezoelectric / electrostrictive material layer. . 26. The method of manufacturing a piezoelectric / electrostrictive element according to claim 24, wherein the ceramic substrate is made of an unfired piezoelectric / electrostrictive material layer. . 27. The method for manufacturing a piezoelectric / electrostrictive element according to claim 24, wherein the ceramic substrate is not a piezoelectric / electrostrictive material, and a fired ceramic material layer and a fired piezoelectric / electrostrictive material. A method for manufacturing a piezoelectric / electrostrictive element, which comprises a two-layer structure with layers. 28. The method for manufacturing a piezoelectric / electrostrictive element according to claim 24, wherein the ceramic substrate is not a piezoelectric / electrostrictive material, and is an unfired ceramic material layer and an unfired piezoelectric / electrostrictive material. A method for manufacturing a piezoelectric / electrostrictive element, which comprises a two-layer structure with layers. 29. The method for manufacturing a piezoelectric / electrostrictive element according to claim 25, wherein the piezoelectric / electrostrictive material layer is formed by a green sheet forming method. And a method for manufacturing a piezoelectric / electrostrictive element. 30. The method for manufacturing a piezoelectric / electrostrictive element according to claim 25, wherein the piezoelectric / electrostrictive material layer is formed by a screen printing method. A method for manufacturing a piezoelectric / electrostrictive element. 31. The method for manufacturing a piezoelectric / electrostrictive element according to claim 29 or 30, wherein a plurality of the piezoelectric / electrostrictive element precursors are arranged on the ceramic substrate. A method for manufacturing a piezoelectric / electrostrictive element. 32. The piezoelectric / electrostrictive element according to claim 24, wherein the adhesion preventing layer is made of a substance that sublimes. Method.