JP2013207073A - Piezoelectric/electrostrictive actuator and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve insulation properties, under high-humidity atmosphere, of a piezoelectric/electrostrictive actuator having a piezoelectric/electrostrictive layer by enhancing moisture resistance without blocking variation of the piezoelectric/electrostrictive actuator.SOLUTION: A second piezoelectric/electrostrictive layer is disposed as a moistureproof film in an outside (ambient atmosphere side) of the first piezoelectric/electrostrictive layer. A ratio of a size of a crystal grain included in the second piezoelectric/electrostrictive layer to a size of a crystal grain included in the first piezoelectric/electrostrictive layer is within a predetermined range, and a ratio of the size of the crystal grain included in the second piezoelectric/electrostrictive layer to the thickness of the second piezoelectric/electrostrictive layer is within a predetermined range.

Description

The present invention relates to a piezoelectric / electrostrictive actuator. More specifically, the present invention relates to a piezoelectric / electrostrictive actuator having high reliability in a high humidity atmosphere while suppressing inhibition of piezoelectric displacement. The present invention further relates to a method of manufacturing such a piezoelectric / electrostrictive actuator.

  Piezoelectric / electrostrictive actuators have the advantage that displacement can be precisely controlled on the order of submicrons. In particular, a piezoelectric / electrostrictive actuator using a sintered body of a piezoelectric / electrostrictive porcelain composition as a piezoelectric / electrostrictive body can precisely control displacement, and has high electromechanical conversion efficiency. It has the advantages of large force, fast response speed, high durability, and low power consumption. Taking advantage of these advantages, it has been adopted in ink jet heads and micro pumps. However, in these applications, there are concerns over deterioration and dielectric breakdown of piezoelectric films (hereinafter sometimes referred to as “piezoelectric bodies” or “piezoelectric / electrostrictive layers”) at high temperatures and high humidity. In order to suppress such deterioration and dielectric breakdown of the piezoelectric film due to water, various means have been taken.

Therefore, in this technical field, for example, by covering the piezoelectric / electrostrictive actuator with a dense moisture-proof film made of an inorganic material such as Al ₂ O ₃ or SiO ₂ , moisture can be prevented from entering the piezoelectric film from the outside. Has been proposed (see, for example, Patent Document 1). However, the moisture-proof film made of the inorganic material as described above is hard and has a high possibility of hindering the displacement of the piezoelectric element. Therefore, in this technical field, measures such as patterning have been proposed in order not to cover the active part that generates displacement as a piezoelectric element with a moisture-proof film. In this case, the region corresponding to the active portion on the outer surface of the piezoelectric element is exposed without being covered with the moisture-proof film.

  In the piezoelectric / electrostrictive actuator provided with the moisture-proof film having the opening at the position corresponding to the active portion of the piezoelectric element as described above, for example, the upper electrode made of a metal having a low water vapor transmission rate (for example, Ti, Ru, etc.) Or forming a piezoelectric film by a thin film method such as a gas phase method such as a sputtering method or a liquid phase method such as a sol-gel method (for example, (See Patent Document 2). Incidentally, the piezoelectric film formed by the thin film method as described above has a fine columnar structure. For example, a general molding method such as a gel cast method or a doctor blade method (hereinafter referred to as a “thick film method”). Compared with the piezoelectric film formed by the above), it has a denser structure.

  As a result, the piezoelectric film formed by the thin film method is compared with the piezoelectric film formed by the thick film method, for example, micro cracks (fine cracks) in the layer when the piezoelectric element is polarized or driven. It is hard to produce. Therefore, in the piezoelectric film formed by the thin film method, for example, a certain level of moisture resistance is achieved by covering only the side surface portions that are damaged due to processing such as etching in the manufacturing process of the piezoelectric element. be able to. That is, it can be said that the piezoelectric film formed by the thin film method is suitable for applying a moisture-proof film having an opening at a position corresponding to the active portion of the piezoelectric element as described above.

  However, in order to provide an opening at a location corresponding to the active portion of the moisture-proof film piezoelectric element, processing such as patterning is required as described above, which complicates the manufacturing process of the piezoelectric / electrostrictive actuator. There is a risk of increasing the manufacturing cost. Also, the piezoelectric film formed by the thin film method is very thin, and in order to form a piezoelectric film having a thickness necessary for generating a desired displacement and stress by the thin film method, the piezoelectric film reaches a desired thickness. It is necessary to repeat the thin film method until the manufacturing cost increases.

  On the other hand, according to the thick film method as described above, a piezoelectric film having a desired thickness can be easily formed. However, as described above, the piezoelectric film formed by the thick film method does not have a dense structure as the piezoelectric film formed by the thin film method. Specifically, in the piezoelectric film formed by the thick film method, the crystal grains existing in the film are larger than the piezoelectric film formed by the thin film method, and the grain boundary that is the interface between the crystal grains is large. Spacing is wider. Therefore, in the piezoelectric film formed by the thick film method, for example, during polarization treatment or driving as a piezoelectric / electrostrictive element, a larger stress is applied compared to the piezoelectric film formed by the thin film method. It is easy to concentrate on (particularly, the grain boundary that becomes a triple point). In particular, in the vicinity of the boundary between the active part (active part) and the inactive part (non-active part), microcracks (fine cracks) are likely to occur in the layer.

  As described above, microcracks (fine cracks) generated near the boundary between the active part (working part) and the inactive part (non-working part) and at the grain boundary (particularly, the grain boundary serving as a triple point) are piezoelectric / electrical. There is a possibility that it may lead to problems such as degradation of the strained layer, dielectric breakdown, and short circuit of the electrode. Therefore, for piezoelectric films formed by the thick film method, it is difficult to ensure sufficient insulation in a high humidity atmosphere by covering only the side surfaces as in the piezoelectric film formed by the thin film method. It is. The details of the active part (acting part), the inactive part (non-acting part), and the grain boundary (particularly, the grain boundary that becomes a triple point) will be described later.

  As described above, in the technical field, the moisture resistance of the piezoelectric / electrostrictive actuator including the piezoelectric / electrostrictive layer is improved without hindering the displacement of the piezoelectric / electrostrictive actuator, and the insulation in a high humidity atmosphere is improved. There is an ongoing need for technology that can be improved.

JP 2007-276384 A JP 2009-081347 A

  As described above, in this technical field, the moisture resistance of the piezoelectric / electrostrictive actuator including the piezoelectric / electrostrictive layer is increased without impeding the displacement of the piezoelectric / electrostrictive actuator, and the insulation in a high humidity atmosphere is improved. There is an ongoing need for technology that can be improved. The present invention has been made to meet such a demand. That is, the present invention improves the insulation in a high-humidity atmosphere by enhancing the moisture resistance of the piezoelectric / electrostrictive actuator including the piezoelectric / electrostrictive layer without inhibiting the displacement of the piezoelectric / electrostrictive actuator. One purpose.

The above purpose is
Comprising at least one laminate comprising a first piezoelectric / electrostrictive layer comprising piezoelectric / electrostrictive ceramics and a pair of electrodes respectively disposed on both sides of the first piezoelectric / electrostrictive layer; An operation portion corresponding to a portion where the first piezoelectric / electrostrictive layer is sandwiched between the pair of electrodes, and the first piezoelectric / electrostrictive layer is not sandwiched between the pair of electrodes. A piezoelectric / electrostrictive actuator comprising a piezoelectric / electrostrictive element having a non-actuating part corresponding to a part,
In the laminate closest to the ambient atmosphere,
A second piezoelectric / electrostrictive layer comprising piezoelectric / electrostrictive ceramics between the electrode on the ambient atmosphere side and the first piezoelectric / electrostrictive layer;
A second diameter, which is an average value of the diameters of crystal grains of the piezoelectric / electrostrictive ceramics constituting the second piezoelectric / electrostrictive layer in a plane parallel to the main surface of the second piezoelectric / electrostrictive layer, is the first diameter. It is not more than 0.12 times the first diameter which is the average value of the diameters of the crystal grains of the piezoelectric / electrostrictive ceramics constituting the first piezoelectric / electrostrictive layer in a plane parallel to the main surface of the piezoelectric / electrostrictive layer. And the second diameter is not more than 1.5 times the second layer thickness which is the thickness in the normal direction of the main surface of the second piezoelectric / electrostrictive layer.
This is achieved by a piezoelectric / electrostrictive actuator.

  According to the present invention, the moisture resistance of a piezoelectric / electrostrictive actuator including a piezoelectric / electrostrictive layer can be improved without impeding displacement as a piezoelectric / electrostrictive actuator to improve insulation in a high humidity atmosphere. it can.

SEM of the cross section of the 1st piezoelectric / electrostrictive layer which comprises the piezoelectric / electrostrictive actuator which concerns on one embodiment of this invention, and the 2nd piezoelectric / electrostrictive layer arrange | positioned on the 1st piezoelectric / electrostrictive layer It is a photograph. It is a graph showing the relationship (IV characteristic) between the intensity | strength of the electric field applied between the upper electrode of a piezoelectric / electrostrictive actuator, and a lower electrode, and the electric current which flows between electrodes. High humidity in various combinations of ratio (D2 / D1) of second diameter (D2) to first diameter (D1) and ratio (D2 / T2) of second diameter (D2) to second layer thickness (T2) It is a graph showing the evaluation result of insulation.

  As described above, one object of the present invention is to increase the moisture resistance of a piezoelectric / electrostrictive actuator including a piezoelectric / electrostrictive layer without impeding the displacement of the piezoelectric / electrostrictive actuator and to insulate in a high humidity atmosphere. Is to improve sex. As a result of diligent research to achieve the above object, the present inventor has arranged the second piezoelectric / electrostrictive layer as a moisture-proof film outside the first piezoelectric / electrostrictive layer (on the ambient atmosphere side). The ratio of the size of the crystal grains constituting the electrostrictive layer to the size of the crystal grains constituting the first piezoelectric / electrostrictive layer and the thickness of the second piezoelectric / electrostrictive layer falls within a specific range. As a result, it was found that the insulation in a high-humidity atmosphere can be improved by increasing the moisture resistance of the piezoelectric / electrostrictive actuator including the piezoelectric / electrostrictive layer without hindering the displacement of the piezoelectric / electrostrictive actuator. The present invention has been conceived.

That is, the first embodiment of the present invention is:
Comprising at least one laminate comprising a first piezoelectric / electrostrictive layer comprising piezoelectric / electrostrictive ceramics and a pair of electrodes respectively disposed on both sides of the first piezoelectric / electrostrictive layer; An operation portion corresponding to a portion where the first piezoelectric / electrostrictive layer is sandwiched between the pair of electrodes, and the first piezoelectric / electrostrictive layer is not sandwiched between the pair of electrodes. A piezoelectric / electrostrictive actuator comprising a piezoelectric / electrostrictive element having a non-actuating part corresponding to a part,
In the laminate closest to the ambient atmosphere,
A second piezoelectric / electrostrictive layer comprising piezoelectric / electrostrictive ceramics between the electrode on the ambient atmosphere side and the first piezoelectric / electrostrictive layer;
A second diameter, which is an average value of the diameters of crystal grains of the piezoelectric / electrostrictive ceramics constituting the second piezoelectric / electrostrictive layer in a plane parallel to the main surface of the second piezoelectric / electrostrictive layer, is the first diameter. It is not more than 0.12 times the first diameter which is the average value of the diameters of the crystal grains of the piezoelectric / electrostrictive ceramics constituting the first piezoelectric / electrostrictive layer in a plane parallel to the main surface of the piezoelectric / electrostrictive layer. And the second diameter is not more than 1.5 times the second layer thickness which is the thickness in the normal direction of the main surface of the second piezoelectric / electrostrictive layer.
It is a piezoelectric / electrostrictive actuator.

  As described above, the piezoelectric / electrostrictive actuator according to this embodiment is disposed on both surfaces of the first piezoelectric / electrostrictive layer including the piezoelectric / electrostrictive ceramic and the first piezoelectric / electrostrictive layer. A piezoelectric / electrostrictive element including at least one laminate including a pair of electrodes is provided. The first piezoelectric / electrostrictive layer is composed of a lead zirconate titanate (PZT) -based piezoelectric / electrostrictive porcelain composition and a lead-free piezoelectric / electrostrictive layer that has been vigorously developed from the viewpoint of recent environmental protection. It can be appropriately selected from various piezoelectric / electrostrictive porcelain compositions used for the production of piezoelectric / electrostrictive sintered bodies including electrostrictive porcelain compositions. Specific examples include, for example, lead zirconate, lead titanate, lead magnesium niobate, lead nickel niobate, lead zinc niobate, lead manganate niobate, lead antimony stannate, lead manganese tungstate, lead cobalt niobate, Piezoelectric / electrostrictive ceramics containing barium titanate, bismuth nickel niobate, sodium bismuth titanate, potassium sodium niobate, strontium bismuth tantalate, etc., alone or as a mixture of two or more components, preferably three or more components. It is done.

  Moreover, the said electrode can be suitably selected from the various materials used as an electrode in the said technical field, such as gold (Au), silver (Ag), platinum (Pt), for example. Further, the thickness of the piezoelectric / electrostrictive layer and the electrode can be appropriately set according to the application to which the piezoelectric / electrostrictive actuator according to the present invention is applied. The first piezoelectric / electrostrictive layer and the electrode may be laminated by any method known in the technical field (for example, vapor phase epitaxy or firing after screen printing of each layer). .

  By the way, the piezoelectric / electrostrictive element may include two or more of the laminated bodies. Thus, a piezoelectric / electrostrictive element including two or more of the above laminates can also be manufactured by a technique well known in the art. In any case, it will be apparent to those skilled in the art that the piezoelectric / electrostrictive element can be manufactured in various configurations using various methods known in the art. No more detailed explanation is given here.

  In addition, as described above, in the piezoelectric / electrostrictive layer, for example, in the case of polarization processing or driving as a piezoelectric / electrostrictive element, a minute defect such as a microcrack at a grain boundary (particularly, a grain boundary triple point). Is likely to occur. Note that the grain boundary refers to a boundary between a plurality of crystal grains constituting the piezoelectric / electrostrictive layer (piezoelectric body). Furthermore, the grain boundary triple point refers to a point where the boundaries of three adjacent crystal grains intersect. In the piezoelectric / electrostrictive layer (piezoelectric body), when an electric field is applied, the domain in the crystal grains expands and contracts and rotates, so that a displacement is expressed. At that time, stress concentrates particularly at grain boundaries where the orientation of domains and crystal lattices is not well established. The triple point of a grain boundary is a part where stress is particularly concentrated in the grain boundary. Therefore, microcracks tend to occur at grain boundaries (particularly, grain boundary triple points) of the piezoelectric / electrostrictive layer (piezoelectric body) included in the operating portion.

  In particular, as described above, the piezoelectric film formed by the thick film method does not have a dense structure as the piezoelectric film formed by the thin film method. The crystal grains present in the crystal are large, and the interval between the grain boundaries, which are the interfaces between the crystal grains, is wider. That is, in a piezoelectric film formed by the thick film method, for example, when driving as a polarization process or a piezoelectric / electrostrictive element, a larger stress is applied to the grain boundary compared to the piezoelectric film formed by the thin film method. It is easy to concentrate on (particularly, the grain boundary that becomes a triple point).

  Further, depending on the number of the laminates (including one piezoelectric / electrostrictive layer and a pair of electrodes respectively disposed on both sides of the piezoelectric / electrostrictive layer) included in the piezoelectric / electrostrictive element. The piezoelectric / electrostrictive element included in the piezoelectric / electrostrictive actuator according to this embodiment includes an operation unit corresponding to a portion where the first piezoelectric / electrostrictive layer is sandwiched between the pair of electrodes, There is a non-actuating portion corresponding to a portion where the first piezoelectric / electrostrictive layer is not sandwiched between the pair of electrodes.

  In the piezoelectric / electrostrictive element, the operating portion refers to a portion corresponding to a portion where the first piezoelectric / electrostrictive layer is sandwiched between the pair of electrodes, and the operating portion is the piezoelectric after firing. / In an electrostrictive element, when an electric field is applied between the electrodes, it is a part that causes deformation (displacement) according to the applied electric field. On the other hand, the non-operating portion refers to a portion corresponding to a portion where the first piezoelectric / electrostrictive layer is not sandwiched between the pair of electrodes, and the non-operating portion is the piezoelectric / electrostrictive element after firing. In this case, even when an electric field is applied between the electrodes, a deformation (displacement) corresponding to the applied electric field does not occur (little or no).

  Therefore, as described above, for example, during polarization processing or when driving as a piezoelectric / electrostrictive element, stress acts on the vicinity of the boundary between the operating part and the non-operating part, and microcracks tend to occur. is there. Furthermore, microcracks are particularly likely to occur at the grain boundaries of the piezoelectric / electrostrictive layer (piezoelectric body) included in the vicinity of the boundary between the operating portion and the non-operating portion. This microcrack is a main cause of problems such as deterioration of the piezoelectric / electrostrictive layer, dielectric breakdown, and short-circuiting of the electrodes, and a factor of lowering the insulation of the piezoelectric / electrostrictive element in a high humidity atmosphere.

Therefore, in the piezoelectric / electrostrictive actuator according to the prior art, as described above, the piezoelectric / electrostrictive actuator is covered from the outside by covering the piezoelectric / electrostrictive actuator with a dense moisture-proof film made of an inorganic material such as Al ₂ O ₃ or SiO _2. It has been proposed to prevent moisture from entering the piezoelectric film. In addition, the region corresponding to the active portion of the piezoelectric element of the moisture-proof film is intended to reduce the inhibition of the displacement of the piezoelectric element caused by covering the piezoelectric / electrostrictive actuator with the hard moisture-proof film made of the inorganic material as described above. It has also been proposed to provide an opening in the plate. However, in order to prevent moisture from entering through the opening of the moisture-proof film, for example, an upper electrode made of a special metal (for example, Ti, Ru, etc.) having a low water vapor transmission rate is used. It is necessary to form a piezoelectric film by a thin film method such as a liquid phase method such as a phase method or a sol-gel method.

  The piezoelectric film formed by the thin film method as described above is more in comparison with the piezoelectric film formed by the thick film method which is a general molding method such as a gel cast method or a doctor blade method. Since it has a fine columnar structure, for example, it is difficult to generate microcracks (fine cracks) in the layer during polarization processing or driving of the piezoelectric element. As a result, in a piezoelectric film formed by a thin film method, for example, if only the side surface that is damaged due to processing such as etching in the manufacturing process of the piezoelectric element is covered, a certain level of moisture resistance is achieved. be able to. However, in order to provide an opening at a location corresponding to the active portion of the piezoelectric element of the moisture-proof film, processing such as patterning is required as described above. In addition, the piezoelectric film formed by the thin film method is very thin, and in order to form a piezoelectric film having a thickness necessary for generating the desired displacement and stress by the thin film method, the piezoelectric film has a desired thickness. It is necessary to repeat the thin film method until it reaches. Under such circumstances, in this technical field, as described above, the moisture resistance of the piezoelectric / electrostrictive actuator including the piezoelectric / electrostrictive layer is increased without hindering the displacement of the piezoelectric / electrostrictive actuator, and thus, in a high humidity atmosphere. There was a continuing need for technology that could improve the insulation in the.

  Therefore, in the piezoelectric / electrostrictive actuator according to the present embodiment, the first piezoelectric / electrostrictive layer included in the piezoelectric / electrostrictive element included in the piezoelectric / electrostrictive actuator and a pair of layers disposed on both surfaces thereof. Among the at least one laminate including electrodes, the laminate closest to the ambient atmosphere includes piezoelectric / electrostrictive ceramics between the electrode on the ambient atmosphere side and the first piezoelectric / electrostrictive layer. The second piezoelectric / electrostrictive layer is further provided. Here, the ambient atmosphere is, for example, the first piezoelectric / electrostrictive constituting the piezoelectric / electrostrictive element, such as outside air in contact with the piezoelectric / electrostrictive element included in the piezoelectric / electrostrictive actuator according to the present embodiment. It refers to the external environment that can be a source of moisture that enters the layer. Therefore, for example, when one main surface of the piezoelectric / electrostrictive element is disposed on the substrate and the other main surface is exposed to the outside air, it is closest to the other main surface of the piezoelectric / electrostrictive element. The laminated body corresponds to the above-mentioned “laminated body closest to the ambient atmosphere”. The “laminated body closest to the surrounding atmosphere” is disposed on both surfaces of the first piezoelectric / electrostrictive layer and the first piezoelectric / electrostrictive layer, respectively, including the piezoelectric / electrostrictive ceramic as described above. A pair of formed electrodes.

  In the piezoelectric / electrostrictive actuator according to the present embodiment, the first piezoelectric / electrostrictive layer constituting the “laminated body closest to the ambient atmosphere” and the ambient atmosphere (for example, the external environment, the outside air) of the pair of electrodes. A second piezoelectric / electrostrictive layer containing piezoelectric / electrostrictive ceramics is further provided between the electrode and the near electrode. As will be described in detail later, the second piezoelectric / electrostrictive layer includes the first piezoelectric / electrostrictive layer (and, if there is a lower first piezoelectric / electrostrictive layer, further first piezoelectric / electrostrictive layers). It functions as a moisture barrier film that prevents moisture from entering the electrostrictive layer) from the surrounding atmosphere. As described above, the moisture-proof layer is composed of the second piezoelectric / electrostrictive layer containing piezoelectric / electrostrictive ceramics, and is disposed between the electrode on the ambient atmosphere side and the first piezoelectric / electrostrictive layer. The

  Therefore, when the second piezoelectric / electrostrictive layer includes a piezoelectric / electrostrictive ceramic exhibiting a piezo (piezoelectric / electrostrictive) effect, the moisture-proof layer has a first property when an electric field is applied between the electrodes. Along with the piezoelectric / electrostrictive layer, deformation (displacement) corresponding to the applied electric field can be generated. In this case, since the moisture-proof film composed of the second piezoelectric / electrostrictive layer includes the piezoelectric / electrostrictive ceramics exhibiting a piezoelectric effect, the first moisture-proof film related to the prior art as described above has been concerned. There is a low possibility that the displacement based on the piezoelectric effect of the piezoelectric / electrostrictive actuator by the piezoelectric / electrostrictive layer (which may be simply referred to as “piezoelectric displacement” in this specification) is hindered. From this point of view, the moisture-proof layer composed of the second piezoelectric / electrostrictive layer containing the piezoelectric / electrostrictive ceramics, as described above, in the laminate closest to the ambient atmosphere, the electrode on the ambient atmosphere side and the first piezoelectric / electrostrictive layer. It is desirable to be disposed between the electrostrictive layer.

  The second piezoelectric / electrostrictive layer is provided for the purpose of functioning as a moisture-proof layer as described above. Therefore, it is desirable that the second piezoelectric / electrostrictive layer has a denser structure than the first piezoelectric / electrostrictive layer. That is, the second piezoelectric / electrostrictive layer is composed of small crystal grains regardless of the crystallinity of the piezoelectric / electrostrictive ceramics constituting the second piezoelectric / electrostrictive layer or the crystal structure, for example. It is desirable to have a dense structure.

  Specifically, in the piezoelectric / electrostrictive actuator according to this embodiment, the piezoelectric / electrostrictive ceramics constituting the second piezoelectric / electrostrictive layer in a plane parallel to the main surface of the second piezoelectric / electrostrictive layer. The second diameter, which is the average value of the diameters of the crystal grains, of the piezoelectric / electrostrictive ceramics constituting the first piezoelectric / electrostrictive layer in a plane parallel to the main surface of the first piezoelectric / electrostrictive layer The second diameter is equal to or less than 0.12 times the first diameter which is an average value of the diameters of the second piezoelectric layer and the second diameter is a thickness in the normal direction of the main surface of the second piezoelectric / electrostrictive layer. 1.5 times or less.

  As described above, the first piezoelectric / electrostrictive layer and the second piezoelectric / electrostrictive layer are both piezoelectric / electrostrictive layers including piezoelectric / electrostrictive ceramics. Therefore, these piezoelectric / electrostrictive layers are composed of a plurality of crystal grains of piezoelectric / electrostrictive ceramics. In the piezoelectric / electrostrictive actuator according to this embodiment, as described above, the piezoelectric / electrostrictive ceramics constituting the second piezoelectric / electrostrictive layer in a plane parallel to the main surface of the second piezoelectric / electrostrictive layer. The second diameter, which is the average value of the diameters of the crystal grains, of the piezoelectric / electrostrictive ceramics constituting the first piezoelectric / electrostrictive layer in a plane parallel to the main surface of the first piezoelectric / electrostrictive layer Or less than 0.12 times the first diameter, which is the average value of the diameters.

  Here, the first diameter is an average value of the diameters of crystal grains of piezoelectric / electrostrictive ceramics constituting the first piezoelectric / electrostrictive layer in a plane parallel to the main surface of the first piezoelectric / electrostrictive layer. The first diameter can be obtained, for example, as an average value of the equivalent circular diameters of crystal grains observed on the main surface of the first piezoelectric / electrostrictive layer by a scanning electron microscope (SEM). The second diameter is also defined in the same manner as the first diameter, and can be obtained in the same manner as the first diameter. As described above, in the piezoelectric / electrostrictive actuator according to this embodiment, the second diameter is 0.12 times or less, more preferably 0.07 times or less than the first diameter. If the second diameter exceeds 0.12 times the first diameter, the insulation in a high-humidity atmosphere (hereinafter sometimes referred to as “IV characteristics”) is lowered, which is not desirable.

  As described above, in the piezoelectric / electrostrictive actuator according to this embodiment, the size of crystal grains observed on the main surface of each piezoelectric / electrostrictive layer is larger in the second piezoelectric / electrostrictive layer. It is configured to be sufficiently smaller than one piezoelectric / electrostrictive layer. Thereby, in the piezoelectric / electrostrictive actuator according to the present embodiment, the second piezoelectric / electrostrictive layer can have a denser structure as compared with the first piezoelectric / electrostrictive layer. It can function as a moisture-proof film that prevents moisture from entering the first piezoelectric / electrostrictive layer from the ambient atmosphere.

  As described above, the first diameter and the second diameter are on the main surface of each piezoelectric / electrostrictive layer of the ceramic crystal grains constituting the first piezoelectric / electrostrictive layer and the second piezoelectric / electrostrictive layer, respectively. It is an average value of diameters of crystal grains (for example, equivalent circular diameter) in parallel (perpendicular to the thickness direction) plane. Therefore, in some cases (for example, when the shape of the crystal grains is a flat plate shape), the second diameter is the thickness of the second piezoelectric / electrostrictive layer (that is, the main surface of the second piezoelectric / electrostrictive layer). It may be larger than the dimension in the normal direction). However, when the second diameter is excessive with respect to the thickness of the second piezoelectric / electrostrictive layer, the interval between the grain boundaries, which are the interfaces between crystal grains, becomes excessively wide, for example, polarization treatment or piezoelectric / electrostrictive element When driving, the stress concentrates on each grain boundary and becomes excessive, and microcracks (fine cracks) are generated, which may reduce the function of the second piezoelectric / electrostrictive layer as a moisture-proof film. .

  Therefore, in the piezoelectric / electrostrictive actuator according to this embodiment, as described above, the second diameter is a thickness of the second layer that is the thickness in the normal direction of the main surface of the second piezoelectric / electrostrictive layer. 1.5 times or less. When the second diameter exceeds 1.5 times the second layer thickness, the second diameter becomes excessive with respect to the second layer thickness as described above, and the interval between the grain boundaries which are the interfaces between the crystal grains is excessively wide. As a result, for example, in the case of polarization processing or driving as a piezoelectric / electrostrictive element, stress concentrates on individual grain boundaries and becomes excessive, resulting in microcracks (fine cracks), and the second piezoelectric / This is not desirable because it may lead to problems such as deterioration of the function of the electrostrictive layer as a moisture-proof film.

  As described above, in the piezoelectric / electrostrictive actuator according to this embodiment, the second piezoelectric / electrostrictive layer is disposed as a moisture-proof film on the outer side (ambient atmosphere side) of the first piezoelectric / electrostrictive layer. The ratio of the size (second diameter) of crystal grains constituting the piezoelectric / electrostrictive layer to the size (first diameter) of crystal grains constituting the first piezoelectric / electrostrictive layer, and the second piezoelectric / electrostrictive layer By configuring the ratio of the size of the crystal grains (second diameter) to the thickness of the second piezoelectric / electrostrictive layer (thickness of the second layer) to fall within a specific range, Without hindering the displacement of the strain actuator, the moisture resistance of the piezoelectric / electrostrictive actuator including the piezoelectric / electrostrictive layer can be improved, and the insulation in a high humidity atmosphere can be improved.

  As described above, in the piezoelectric / electrostrictive actuator according to this embodiment, the second diameter is 0.12 times or less, more preferably 0.07 times or less of the first diameter. When the second diameter is 0.07 times or less of the first diameter, extremely good IV characteristics can be exhibited (insulation in a high humidity atmosphere is extremely high).

Accordingly, the second embodiment of the present invention provides:
A piezoelectric / electrostrictive actuator according to the first embodiment of the present invention,
The second diameter is 0.07 times or less of the first diameter;
It is a piezoelectric / electrostrictive actuator.

  As described above, in the piezoelectric / electrostrictive actuator according to this embodiment, the second diameter is 0.07 times or less the first diameter. That is, in the piezoelectric / electrostrictive actuator according to the present embodiment, the crystal grains of the piezoelectric / electrostrictive ceramic constituting the second piezoelectric / electrostrictive layer are the piezoelectric / electrostrictive ceramic constituting the first piezoelectric / electrostrictive layer. Compared with the crystal grains of (1), it is much finer (the particle size is small). As a result, the second piezoelectric / electrostrictive layer can have a more dense structure than the first piezoelectric / electrostrictive layer. Thereby, in the piezoelectric / electrostrictive actuator according to the present embodiment, the function of the second piezoelectric / electrostrictive layer as a moisture-proof film is further enhanced, and extremely good IV characteristics can be exhibited (in a high humidity atmosphere). Insulation is extremely high.

  By the way, even if it is the 2nd piezoelectric / electrostrictive layer containing a piezoelectric / electrostrictive ceramic, if the layer thickness is excessive, it may become a factor which inhibits the piezoelectric displacement of a 1st piezoelectric / electrostrictive layer. For example, as described above, the size of crystal grains of piezoelectric / electrostrictive ceramics constituting each piezoelectric / electrostrictive layer is greatly different between the first piezoelectric / electrostrictive layer and the second piezoelectric / electrostrictive layer. Thus, for example, when driving as a polarization process or a piezoelectric / electrostrictive element, the degree and mode of expansion and contraction and rotation of the domains in the crystal grains accompanying application of an electric field depends on the first piezoelectric / electrostrictive layer and the second piezoelectric element. / It may be different from the electrostrictive layer. In such a case, as a result, the piezoelectric displacement of the first piezoelectric / electrostrictive layer is inhibited. Therefore, it is desirable to limit the thickness of the second piezoelectric / electrostrictive layer to a range that does not hinder the piezoelectric displacement of the first piezoelectric / electrostrictive layer.

Therefore, the third embodiment of the present invention
A piezoelectric / electrostrictive actuator according to any one of the first or second embodiments of the present invention,
The second layer thickness is not more than 0.11 times the first layer thickness which is the thickness in the normal direction of the main surface of the first piezoelectric / electrostrictive layer.
It is a piezoelectric / electrostrictive actuator.

  As described above, in the piezoelectric / electrostrictive actuator according to this embodiment, the second layer thickness is 0 of the first layer thickness which is the thickness in the normal direction of the main surface of the first piezoelectric / electrostrictive layer. .11 times or less. That is, in the piezoelectric / electrostrictive actuator according to this embodiment, the second piezoelectric / electrostrictive layer has a thickness (normal line of the main surface of the piezoelectric / electrostrictive layer) as compared with the first piezoelectric / electrostrictive layer. The dimension in the direction) is significantly thinner. Thereby, in the piezoelectric / electrostrictive actuator according to the present embodiment, it is possible to avoid the second piezoelectric / electrostrictive layer from hindering the piezoelectric displacement of the first piezoelectric / electrostrictive layer.

  Here, the configuration of the piezoelectric / electrostrictive actuator according to this embodiment will be further described with reference to the accompanying drawings. As described above, FIG. 1 shows a first piezoelectric / electrostrictive layer and a second piezoelectric / electrostrictive layer which are disposed on a first piezoelectric / electrostrictive layer constituting a piezoelectric / electrostrictive actuator according to one embodiment of the present invention. It is a SEM photograph of the section of a piezoelectric / electrostrictive layer. In the piezoelectric / electrostrictive element provided in the actual piezoelectric / electrostrictive actuator according to this embodiment, a pair of the piezoelectric / electrostrictive layer and the piezoelectric / electrostrictive layer is sandwiched between the pair. Electrodes are provided. However, in the SEM photograph shown in FIG. 1, the fracture surface of the laminate without the electrodes is used for the sake of easy understanding of the structure of the laminate of the first piezoelectric / electrostrictive layer and the second piezoelectric / electrostrictive layer. Was observed.

  As shown in FIG. 1, the second layer thickness T2, which is the thickness in the normal direction of the main surface of the second piezoelectric / electrostrictive layer disposed on the upper side in the drawing, is arranged on the lower side in the drawing. It is much thinner than the first layer thickness T1, which is the thickness in the normal direction of the principal surface of the first piezoelectric / electrostrictive layer provided. Therefore, as described above, the second piezoelectric / electrostrictive layer is different from the first piezoelectric / electrostrictive layer due to, for example, a difference in the degree of expansion / contraction and rotation of domains in crystal grains accompanying application of an electric field. Even in the case where the piezoelectric displacement can be a factor, the second layer thickness T2 is sufficiently smaller than the first layer thickness T1, so that the second piezoelectric / electrostrictive layer causes the piezoelectric displacement of the first piezoelectric / electrostrictive layer. Inhibiting is avoided.

  Further, although it is difficult to understand in the SEM photograph shown in FIG. 1, the size of the crystal grains of the piezoelectric / electrostrictive ceramics constituting the second piezoelectric / electrostrictive layer disposed on the upper side in the drawing is appropriate for the drawing. The size of the crystal grains of the piezoelectric / electrostrictive ceramics constituting the first piezoelectric / electrostrictive layer disposed on the lower side is sufficiently small. That is, also in the piezoelectric / electrostrictive actuator according to the embodiment shown in FIG. 1, as described above, in the laminated body closest to the ambient atmosphere, the electrode on the ambient atmosphere side and the first piezoelectric / electrostrictive layer are A second piezoelectric / electrostrictive layer comprising a piezoelectric / electrostrictive ceramic is further provided therebetween, and the second piezoelectric / electrostrictive layer is configured in a plane parallel to the main surface of the second piezoelectric / electrostrictive layer. The second diameter, which is the average value of the diameters of the crystal grains of the piezoelectric / electrostrictive ceramics, constitutes the first piezoelectric / electrostrictive layer in the plane parallel to the main surface of the first piezoelectric / electrostrictive layer. It is not more than 0.12 times the first diameter which is the average value of the diameters of the crystal grains of the strain ceramics, and the second diameter is the thickness in the normal direction of the main surface of the second piezoelectric / electrostrictive layer. It is 1.5 times or less of the second layer thickness. Thereby, also in the piezoelectric / electrostrictive actuator according to the embodiment shown in FIG. 1, the second piezoelectric / electrostrictive layer can have a denser structure than the first piezoelectric / electrostrictive layer, As a result, it can function as a moisture-proof film that prevents moisture from entering the first piezoelectric / electrostrictive layer from the ambient atmosphere.

  Incidentally, the second diameter, which is an average value of the diameters of the crystal grains of the piezoelectric / electrostrictive ceramics constituting the second piezoelectric / electrostrictive layer in a plane parallel to the main surface of the second piezoelectric / electrostrictive layer, is the above-mentioned various Any size may be used as long as the above condition is satisfied. However, from the viewpoint of making the structure of the second piezoelectric / electrostrictive layer sufficiently dense, the second diameter is more preferably 0.20 μm or less.

Therefore, the fourth embodiment of the present invention is
A piezoelectric / electrostrictive actuator according to any one of the first to third embodiments of the present invention,
The second diameter is 0.20 μm or less;
It is a piezoelectric / electrostrictive actuator.

  As described above, in the piezoelectric / electrostrictive actuator according to this embodiment, the second diameter is 0.20 μm or less. Thereby, in the piezoelectric / electrostrictive actuator according to the present embodiment, the structure of the second piezoelectric / electrostrictive layer can be made sufficiently dense. As a result, the second piezoelectric / electrostrictive layer has the following structure: It can function reliably as a moisture-proof film that prevents moisture from entering the first piezoelectric / electrostrictive layer from the ambient atmosphere.

  As is well known to those skilled in the art, a piezoelectric / electrostrictive actuator uses a deformation (piezo effect) of a piezoelectric body caused by an applied voltage (electric field) to apply a voltage (electric field) to a force (stress). It includes a piezoelectric / electrostrictive element that is an element for converting into a piezoelectric material. Generally, at least one main surface of the piezoelectric / electrostrictive element is disposed on a substrate that is deformed or moved in accordance with the displacement of the piezoelectric / electrostrictive element caused by the piezoelectric effect.

Accordingly, the fifth embodiment of the present invention provides:
A piezoelectric / electrostrictive actuator according to any one of the first to fourth embodiments of the present invention,
The piezoelectric / electrostrictive element is disposed on a substrate;
It is a piezoelectric / electrostrictive actuator.

  As described above, in the piezoelectric / electrostrictive actuator according to this embodiment, the piezoelectric / electrostrictive element is disposed on the substrate. The substrate is deformed or moved in accordance with the displacement of the piezoelectric / electrostrictive element caused by the piezoelectric effect. Thereby, in the piezoelectric / electrostrictive actuator according to the present embodiment, the displacement of the piezoelectric / electrostrictive element generated according to the voltage (electric field) due to the piezoelectric effect can be effectively used.

By the way, as the substrate, a substrate generally used as a substrate for a piezoelectric / electrostrictive actuator can be used. Such a substrate can be manufactured using materials such as zirconium oxide (ZrO ₂ ), silicon dioxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), for example. The substrate may contain a small amount of additives such as yttrium oxide (Y ₂ O ₃ ) and titanium oxide (TiO ₂ ). Furthermore, as a substrate manufacturing method, a technique well-known in the technical field (for example, green sheet molding or the like) can be used. The thickness and shape of the substrate can be appropriately designed according to the application to which the piezoelectric / electrostrictive actuator according to this embodiment is applied.

  For example, the substrate may have a thin portion having a thickness thinner than other portions. In this case, by disposing the piezoelectric / electrostrictive element so as to cover (at least a part of) the thin-walled portion, the displacement of the piezoelectric / electrostrictive element generated according to the voltage (electric field) due to the piezoelectric effect is It can be used more effectively.

Accordingly, the sixth embodiment of the present invention provides:
A piezoelectric / electrostrictive actuator according to the fifth embodiment of the present invention,
The substrate has a thin portion, and the piezoelectric / electrostrictive element is disposed so as to cover at least a part of the thin portion,
It is a piezoelectric / electrostrictive actuator.

  As described above, in the piezoelectric / electrostrictive actuator according to this embodiment, the substrate has a thin portion, and the piezoelectric / electrostrictive element is disposed so as to cover at least a part of the thin portion. Yes. Thereby, in the piezoelectric / electrostrictive actuator according to the present embodiment, the displacement of the piezoelectric / electrostrictive element caused by the voltage (electric field) due to the piezo effect can be used more effectively.

  The thin portion of the substrate can also be formed by a method generally used for substrates for piezoelectric / electrostrictive actuators. For example, the thin portion may be formed by cutting the substrate by a technique such as etching, and the thin portion is formed on a relatively thin member (for example, having a thickness of several μm) where the thin portion is to be formed. You may form by laminating | stacking another member (thick part) comparatively thick processed so that it may have an opening part in the location corresponding to a part.

  That is, regardless of the method for forming the thin portion (cutting method or lamination method), there is a surface (for example, the top surface) on the side opposite to the side where the piezoelectric / electrostrictive element of the thin portion is fixed. ) Is in contact with the thin-walled portion, and there is a space where the surface (for example, a side surface) intersecting the thin-walled portion is in contact with the inner wall of the opening of the thick-walled portion. The piezoelectric / electrostrictive actuator according to this embodiment is also applied to the thickness of the substrate, the thickness and area of the thin portion of the substrate, and the volume of the opening of the thick portion (thickness of the thick portion). It can design suitably according to a use.

  For example, when the piezoelectric / electrostrictive actuator according to this embodiment is used as a liquid ejecting head such as an ink jet head used in an ink jet printer, a mechanism for ejecting a liquid such as ink (for example, an ejecting nozzle) Can be provided so as to be connected to the opening surface of the space (a surface not in contact with the thin wall portion or the inner wall of the thick wall portion). A configuration generally used in the technical field of the liquid ejecting head can also be adopted as the configuration of the ejecting mechanism.

  By the way, in the piezoelectric / electrostrictive actuator according to this embodiment, as described above, the substrate has a thin portion, and the piezoelectric / electrostrictive element is disposed so as to cover at least a part of the thin portion. Has been. In other words, the piezoelectric / electrostrictive element is disposed in a region corresponding to the thin portion on the opposite side of the space (opening portion of the thick portion) of the substrate. In the region, the piezoelectric / electrostrictive element and the substrate may be firmly fixed to each other, or the piezoelectric / electrostrictive element is disposed so as to cover at least a part of the thin portion. However, the piezoelectric / electrostrictive element and the substrate may not be fixed. Which arrangement method is adopted can be appropriately determined according to the application to which the piezoelectric / electrostrictive actuator according to this embodiment is to be applied.

Accordingly, the seventh embodiment of the present invention provides:
A piezoelectric / electrostrictive actuator according to the sixth embodiment of the present invention,
The piezoelectric / electrostrictive element is fixed to a region corresponding to the thin portion on the substrate,
It is a piezoelectric / electrostrictive actuator.

  As described above, in the piezoelectric / electrostrictive actuator according to this embodiment, the piezoelectric / electrostrictive element is fixed to a region corresponding to the thin portion on the substrate. In other words, in the piezoelectric / electrostrictive actuator according to the present embodiment, the piezoelectric / electrostrictive element corresponds to the thin portion on the opposite side of the space (opening portion of the thick portion) of the substrate. Secured to the area. Thereby, in the piezoelectric / electrostrictive actuator according to this embodiment, the piezoelectric / electrostrictive element can be reliably arranged so as to cover at least a part of the thin portion of the substrate. In addition, in the piezoelectric / electrostrictive actuator according to the present embodiment, since the piezoelectric / electrostrictive element is fixed to a region corresponding to the thin portion on the substrate, for example, a voltage ( The displacement of the piezoelectric / electrostrictive element generated according to the electric field can be more faithfully transmitted to the thin portion.

  By the way, as described above, the piezoelectric / electrostrictive element included in the piezoelectric / electrostrictive actuator according to the present invention is a pair of piezoelectric / electrostrictive layers disposed on both sides of the piezoelectric / electrostrictive layer and the piezoelectric / electrostrictive layer. At least one laminate including an electrode is included. The outermost layer of the piezoelectric / electrostrictive element having such a structure may have an electrode constituting the laminate positioned in the outermost layer exposed, or may be positioned in the outermost layer for processing or design reasons, for example. Any insulating material may cover the electrodes constituting the laminated body. In the former case, the substrate and the piezoelectric / electrostrictive element are fixed via the electrodes.

Accordingly, the eighth embodiment of the present invention provides:
A piezoelectric / electrostrictive actuator according to any one of the fifth to seventh embodiments of the present invention,
The substrate and the piezoelectric / electrostrictive element are fixed via the electrodes,
It is a piezoelectric / electrostrictive actuator.

  As described above, in the piezoelectric / electrostrictive actuator according to this embodiment, the substrate and the piezoelectric / electrostrictive element are fixed via the electrode. In other words, in the piezoelectric / electrostrictive actuator according to this embodiment, among the electrodes constituting the piezoelectric / electrostrictive element, the electrode closest to the substrate does not pass through, for example, the piezoelectric / electrostrictive layer. , Directly fixed to the substrate. With this configuration, in the piezoelectric / electrostrictive actuator according to this embodiment, for example, the dimension in the thickness direction of the substrate can be further reduced (thinned). Further, in this configuration, the electrode closest to the substrate is fixed to the substrate via the piezoelectric / electrostrictive layer (that is, the piezoelectric / electrostrictive is between the electrode closest to the substrate and the substrate). Since there are fewer parts that do not contribute to the piezoelectric displacement compared to the configuration (with layers interposed), it is useful in applications that seek to achieve greater piezoelectric displacement in smaller piezoelectric / electrostrictive actuators.

Incidentally, as described above, the present invention also relates to various piezoelectric / electrostrictive actuator manufacturing methods according to the present invention including the various embodiments described above.
That is, the ninth embodiment of the present invention
Comprising at least one laminate comprising a first piezoelectric / electrostrictive layer comprising piezoelectric / electrostrictive ceramics and a pair of electrodes respectively disposed on both sides of the first piezoelectric / electrostrictive layer; An operation portion corresponding to a portion where the first piezoelectric / electrostrictive layer is sandwiched between the pair of electrodes, and the first piezoelectric / electrostrictive layer is not sandwiched between the pair of electrodes. A piezoelectric / electrostrictive actuator comprising a piezoelectric / electrostrictive element having a non-actuating part corresponding to a part,
In the laminate closest to the ambient atmosphere,
A second piezoelectric / electrostrictive layer comprising piezoelectric / electrostrictive ceramics between the electrode on the ambient atmosphere side and the first piezoelectric / electrostrictive layer;
A second diameter, which is an average value of the diameters of crystal grains of the piezoelectric / electrostrictive ceramics constituting the second piezoelectric / electrostrictive layer in a plane parallel to the main surface of the second piezoelectric / electrostrictive layer, is the first diameter. It is not more than 0.12 times the first diameter which is the average value of the diameters of the crystal grains of the piezoelectric / electrostrictive ceramics constituting the first piezoelectric / electrostrictive layer in a plane parallel to the main surface of the piezoelectric / electrostrictive layer. And the second diameter is not more than 1.5 times the second layer thickness which is the thickness in the normal direction of the main surface of the second piezoelectric / electrostrictive layer.
Piezoelectric / electrostrictive actuator,
A manufacturing method of
The first piezoelectric / electrostrictive layer is formed by a solid phase reaction method involving heat treatment at a first temperature, which is a relatively high temperature,
The second piezoelectric / electrostrictive layer is formed by a thin film method involving heat treatment at a second temperature, which is a relatively low temperature.
This is a method for manufacturing a piezoelectric / electrostrictive actuator.

  As described above, the piezoelectric / electrostrictive actuator manufacturing method according to the present embodiment is arranged on both surfaces of the first piezoelectric / electrostrictive layer including the piezoelectric / electrostrictive ceramic and the first piezoelectric / electrostrictive layer. An actuating portion corresponding to a portion in which the first piezoelectric / electrostrictive layer is sandwiched between the pair of electrodes, comprising at least one laminate including a pair of electrodes provided; A piezoelectric / electrostrictive actuator comprising a piezoelectric / electrostrictive element having a non-actuating portion corresponding to a portion where the first piezoelectric / electrostrictive layer is not sandwiched between the pair of electrodes. In the nearest laminate, a second piezoelectric / electrostrictive layer containing piezoelectric / electrostrictive ceramics is further provided between the electrode on the ambient atmosphere side and the first piezoelectric / electrostrictive layer, The second piezoelectric / electrostrictive layer is formed on a plane parallel to the main surface of the piezoelectric / electrostrictive layer. The second diameter, which is the average value of the diameters of the crystal grains of the piezoelectric / electrostrictive ceramic, is the piezoelectric / electrostrictive layer constituting the first piezoelectric / electrostrictive layer in a plane parallel to the main surface of the first piezoelectric / electrostrictive layer. The second diameter is equal to or less than 0.12 times the first diameter, which is an average value of the diameters of the electrostrictive ceramic crystal grains, and the thickness in the normal direction of the main surface of the second piezoelectric / electrostrictive layer. A piezoelectric / electrostrictive actuator that is less than 1.5 times the thickness of a certain second layer is to be manufactured. The configuration and the like of the piezoelectric / electrostrictive actuator have already been described in the description of the various embodiments described above, and thus description thereof will not be repeated here.

  As described above, in the method for manufacturing a piezoelectric / electrostrictive actuator according to this embodiment, the first piezoelectric / electrostrictive layer is formed by a solid-phase reaction method involving heat treatment at a first temperature that is a relatively high temperature. The second piezoelectric / electrostrictive layer formed is formed by a thin film method involving heat treatment at a second temperature which is a relatively low temperature. Here, as is well known to those skilled in the art, the solid phase reaction method, for example, weighs oxides, carbonates, nitrates, etc. (powder), which are the raw materials of the target ceramic, to a predetermined composition. In this method, after mixing, heat treatment is performed to obtain a piezoelectric / electrostrictive ceramic having a desired composition. The piezoelectric / electrostrictive ceramics thus obtained can be formed by, for example, a thick film method, which is a general forming method such as a gel cast method or a doctor blade method, after pulverization.

  As described above, the first piezoelectric / electrostrictive layer constituting the piezoelectric / electrostrictive element included in the piezoelectric / electrostrictive actuator manufactured by the manufacturing method according to this embodiment is made of lead zirconate titanate (PZT). For the production of piezoelectric / electrostrictive ceramics, including piezoelectric / electrostrictive ceramic compositions and lead-free piezoelectric / electrostrictive ceramic compositions that have been vigorously developed from the viewpoint of recent environmental protection It can be suitably selected from various piezoelectric / electrostrictive porcelain compositions used. Specific examples include, for example, lead zirconate, lead titanate, lead magnesium niobate, lead nickel niobate, lead zinc niobate, lead manganate niobate, lead antimony stannate, lead manganese tungstate, lead cobalt niobate, Piezoelectric / electrostrictive ceramics containing barium titanate, bismuth nickel niobate, sodium bismuth titanate, potassium sodium niobate, strontium bismuth tantalate, etc., alone or as a mixture of two or more components, preferably three or more components. It is done. Moreover, although low-temperature baking is desired from the viewpoint of cost reduction or the like, a sintering aid may be added for this purpose.

  Further, as described above, the electrode can be appropriately selected from various materials used as an electrode in the technical field, such as gold (Au), silver (Ag), platinum (Pt), and the like. . Further, the thickness of the piezoelectric / electrostrictive layer and the electrode can be appropriately set according to the application to which the piezoelectric / electrostrictive actuator according to the present invention is applied. The first piezoelectric / electrostrictive layer and the electrode may be laminated by any method known in the technical field (for example, vapor phase epitaxy or firing after screen printing of each layer). .

  On the other hand, the second piezoelectric / electrostrictive layer is formed by a thin film method involving a heat treatment at a second temperature which is a relatively low temperature. Here, the thin film method is a film forming method such as a vapor phase method such as a sputtering method or a liquid phase method such as a sol-gel method, as is well known to those skilled in the art. A piezoelectric film formed by such a thin film method is compared with a piezoelectric film formed by a thick film method, which is a general piezoelectric / electrostrictive ceramic film forming method such as a gel cast method or a doctor blade method. In addition, since it has a finer columnar structure, for example, when a piezoelectric element is polarized or driven, microcracks (fine cracks) hardly occur in the layer, and the function as a moisture-proof film can be exhibited. . The composition of the piezoelectric / electrostrictive ceramics included in the second piezoelectric / electrostrictive layer is the first piezoelectric / electrostrictive as long as the conditions regarding the first diameter, the second diameter, and the second layer thickness are satisfied. The composition may be the same as or different from the composition of the piezoelectric / electrostrictive ceramics that the layer comprises.

  By the way, in the method for manufacturing a piezoelectric / electrostrictive actuator according to the present embodiment, as described above, the first piezoelectric / electrostrictive layer has a solid-phase reaction involving heat treatment at a first temperature which is a relatively high temperature. The second piezoelectric / electrostrictive layer is formed by a thin film method involving heat treatment at a second temperature, which is a relatively low temperature. As a result, the piezoelectric / electrostrictive actuator manufactured by the method for manufacturing a piezoelectric / electrostrictive actuator according to the present embodiment satisfies the above-described conditions regarding the first diameter, the second diameter, the second layer thickness, and the like. it can. The specific values of the first temperature and the second temperature are, for example, the composition of the piezoelectric / electrostrictive ceramics included in the first piezoelectric / electrostrictive layer, and the piezoelectric / electrostrictive layer included in the second piezoelectric / electrostrictive layer. It can be set as appropriate according to the composition of the electrostrictive ceramic. In addition, as a method for heat treatment of the first piezoelectric / electrostrictive layer and / or the second piezoelectric / electrostrictive layer, for example, rapid thermal annealing (RTA) can be employed. Specific examples of the first temperature and the second temperature include a temperature range of 800 ° C. or higher and lower than 1300 ° C. and 500 ° C. or higher and lower than 700 ° C., respectively.

Accordingly, the tenth embodiment of the present invention provides:
A method for manufacturing a piezoelectric / electrostrictive actuator according to the ninth embodiment of the present invention, comprising:
The first temperature is 800 ° C. or higher and lower than 1300 ° C .;
The second temperature is 500 ° C. or higher and lower than 700 ° C.,
This is a method for manufacturing a piezoelectric / electrostrictive actuator.

  As described above, in the method for manufacturing a piezoelectric / electrostrictive actuator according to this embodiment, the first temperature is 800 ° C. or higher and lower than 1300 ° C., and the second temperature is 500 ° C. or higher and lower than 700 ° C. Thereby, the piezoelectric / electrostrictive actuator according to the present invention that satisfies the conditions regarding the first diameter, the second diameter, the second layer thickness, and the like described above can be more reliably manufactured. Incidentally, when the first temperature is less than 800 ° C., for example, the denseness is poor and the insulation is deteriorated, or when the second piezoelectric / electrostrictive layer is baked, it is easy to be integrated with the first piezoelectric / electrostrictive layer. For example, it is difficult to suppress the evaporation of the lead component of the piezoelectric / electrostrictive layer. On the other hand, if the second temperature is less than 500 ° C., for example, it becomes difficult to crystallize the second piezoelectric / electrostrictive layer, so that the denseness becomes poor and the insulation becomes worse, or the amount of piezoelectric displacement decreases. If it is 700 ° C. or higher, for example, it is not desirable because it is difficult to integrate with the second piezoelectric / electrostrictive layer during firing or to suppress the evaporation of the lead component.

  Incidentally, as described above, a thin film method is employed as a method for forming the second piezoelectric / electrostrictive layer in the method for manufacturing a piezoelectric / electrostrictive actuator according to the present invention. As described above, the thin film method is a film forming method such as a gas phase method such as a sputtering method or a liquid phase method such as a sol-gel method, and the method for manufacturing a piezoelectric / electrostrictive actuator according to the present invention. As a method for forming the second piezoelectric / electrostrictive layer, any thin film method may be employed.

Accordingly, the eleventh embodiment of the present invention is
A method for manufacturing a piezoelectric / electrostrictive actuator according to any one of the ninth or tenth embodiments of the present invention,
The thin film method includes any one method selected from a sol-gel method and a sputtering method,
This is a method for manufacturing a piezoelectric / electrostrictive actuator.

  As described above, in the method for manufacturing a piezoelectric / electrostrictive actuator according to this embodiment, the thin film method includes any one method selected from a sol-gel method and a sputtering method. In other words, in the method for manufacturing a piezoelectric / electrostrictive actuator according to this embodiment, as a method for forming the second piezoelectric / electrostrictive layer, any one method selected from a sol-gel method and a sputtering method is used. Can be adopted. Thereby, in the piezoelectric / electrostrictive actuator manufactured by the manufacturing method according to this embodiment, the second piezoelectric / electrostrictive layer has a denser structure than the first piezoelectric / electrostrictive layer. As a result, it can function as a moisture-proof film that prevents moisture from entering the first piezoelectric / electrostrictive layer from the ambient atmosphere.

  The present invention will be described in more detail with reference to the following examples, but the technical scope of the present invention is not limited to these examples.

Production of Piezoelectric / Electrostrictive Actuator Evaluation of the influence of the first diameter, the second diameter, the first layer thickness, and the second layer thickness on the insulation properties of the piezoelectric / electrostrictive actuator having the above-described configuration in a high humidity atmosphere. For the purpose of manufacturing piezoelectric / electrostrictive actuators having various first diameters, second diameters, first layer thicknesses, and second layer thickness combinations, high humidity atmospheres of the individual piezoelectric / electrostrictive actuators The lower insulation was evaluated. However, the configuration and manufacturing method described below are merely examples, and the configuration and manufacturing method of the piezoelectric / electrostrictive actuator according to the present invention are not limited to these.

(1) Production of Piezoelectric / Electrostrictive Actuator In this example, a substrate mainly made of zirconium oxide (ZrO ₂ ) is used as the substrate material, the thickness of the thin portion is 2 μm, the width is 80 μm, and the length is 1 mm. It was. Next, a platinum (Pt) electrode (lower electrode) having a thickness of 0.5 μm is applied by a resist method so as to cover a region corresponding to the thin portion of the main surface of the substrate (the side opposite to the cavity formed by the thin portion). Formed by.

As a main material of the first piezoelectric / electrostrictive layer, a piezoelectric / electrostrictive ceramic of 0.2 Bi (Ni _2/3 Nb _1/3 ) O ₃ + 0.80 PZT was synthesized by a solid phase reaction method. Lead oxide (PbO), a dispersant, and a binder were added to the piezoelectric / electrostrictive ceramic thus obtained, and wet pulverized to obtain a slurry having an average particle size of 0.15 μm. The slurry was screen-printed on the lower electrode, degreased, and then fired at 1000 ° C. for 2 hours to form a first piezoelectric / electrostrictive layer. The first layer thickness was variously changed by changing the coating amount during screen printing. The values of the first layer thickness (T1) and the first diameter (D1) for each piezoelectric / electrostrictive actuator are listed in Table 1.

  On the other hand, the second piezoelectric / electrostrictive layer is formed by applying a sol-gel solution having a composition ratio of Pb / Zr / Ti = 1.1 / 0.52 / 0.48 by spin coating to the first piezoelectric / electrostrictive layer. It was formed by coating on and heat-treating with RTA. Incidentally, the second diameter (D2) was variously changed by changing the temperature during RTA in the range of 500 ° C. to 700 ° C. The values of the second layer thickness (T2) and the second diameter (D2) for each piezoelectric / electrostrictive actuator are also listed in Table 1. On the second piezoelectric / electrostrictive layer thus obtained, an upper electrode having a thickness of 0.1 μm was formed by a resist method using gold (Au) resinate.

(2) Polarization treatment of piezoelectric / electrostrictive actuator The piezoelectric / electrostrictive actuator obtained as described above was subjected to polarization treatment. A voltage was applied to the electrode of the piezoelectric / electrostrictive actuator (sintered body) on which the electrode was formed as described above. At this time, it is desirable to perform a high temperature polarization treatment in which the piezoelectric / electrostrictive actuator is heated to 50 to 150 ° C. When performing the high temperature polarization process, an electric field of 2 to 20 kV / mm is applied to the piezoelectric / electrostrictive actuator. In this example, an electric field of 15 kV / mm was applied to the piezoelectric / electrostrictive actuator at 70 ° C., but the conditions for the polarization treatment also depend on the configuration of the piezoelectric / electrostrictive element and the like. It can be appropriately selected from various techniques well known in the field. Furthermore, when performing an aging process, you may heat the said piezoelectric / electrostrictive actuator to 100-300 degreeC in air | atmosphere in the state by which the electrode was open | released.

A) Evaluation of Insulating Property in High Humidity Atmosphere Evaluation methods and evaluation results of various piezoelectric / electrostrictive actuators manufactured as described above in a high humidity atmosphere will be described below. While changing the strength of the electric field applied between the upper and lower electrodes of the various piezoelectric / electrostrictive actuators manufactured as described above in a high humidity atmosphere of 27 ° C. × 85% RH, between these electrodes The current (IV characteristic) flowing in the was measured. An example of the measurement result will be further described with reference to the accompanying drawings. FIG. 2 is a graph showing the relationship (IV characteristic) between the intensity of the electric field applied between the upper electrode and the lower electrode of the piezoelectric / electrostrictive actuator and the current flowing between the electrodes as described above.

  In the graph of FIG. 2, the piezoelectric / electrostrictive actuator according to an exemplary embodiment of the present invention is represented by a solid line, and the piezoelectric / electrostrictive actuator according to the prior art is represented by a dotted line. As shown in the graph of FIG. 2, in both the piezoelectric / electrostrictive actuator according to the present invention and the piezoelectric / electrostrictive actuator according to the prior art, when the strength of the electric field applied between the upper electrode and the lower electrode increases, It is recognized that the value of the current flowing between these electrodes tends to increase. However, when compared at the same electric field strength, the current value flowing in the piezoelectric / electrostrictive actuator according to the present invention is significantly smaller than the current value flowing in the piezoelectric / electrostrictive actuator according to the prior art. That is, it was confirmed that the piezoelectric / electrostrictive actuator according to the present invention exhibits superior insulation in a high humidity atmosphere as compared with the piezoelectric / electrostrictive actuator according to the prior art. As an evaluation result thus obtained, the current value [μA] at an electric field strength of 20 V / μm was calculated from the first diameter (D1), the second diameter (D2), and the first layer thickness of each piezoelectric / electrostrictive actuator. It is listed in the following Table 1 together with the values of (T1) and the second layer thickness (T2).

  As described above, in Table 1, for each of the various combinations of the first diameter (D1), the second diameter (D2), the first layer thickness (T1), and the second layer thickness (T2), 20V / The current value (μA) at an electric field strength of μm is listed in the upper row, and the evaluation results of the insulation properties in a high humidity atmosphere based on the individual current values are listed in the lower row. In addition, as an evaluation standard for insulation in a high humidity atmosphere, when the current value (μA) at an electric field strength of 20 V / μm is 0.10 μA or less, it is good (◯), exceeds 0.10 μA and 1. When it was 5 μA or less, it was acceptable (Δ), and when it exceeded 1.5 μA, it was judged as defective (×). As is clear from the results shown in Table 1, the first diameter (D1), the second diameter (D2), the first layer thickness (T1), and the second layer thickness (T2) satisfy a specific relationship. Only in a certain range, the result was evaluated as good (◯) or acceptable (Δ) in the insulation under a high humidity atmosphere. Thus, regarding the influence of the first diameter (D1), the second diameter (D2), the first layer thickness (T1), and the second layer thickness (T2) on the insulation properties of the piezoelectric / electrostrictive actuator in a high humidity atmosphere, Consider the following in detail.

[A-1] Ratio of the second diameter (D2) to the first diameter (D1) (D2 / D1)
First, the influence of the ratio (D2 / D1) of the second diameter (D2) to the first diameter (D1) on the insulation in a high humidity atmosphere will be considered. Therefore, in various combinations of the first diameter (D1), the second diameter (D2), the first layer thickness (T1), and the second layer thickness (T2) listed in Table 1, the insulating properties in a high humidity atmosphere Table 2 below lists the ratio (D2 / D1) of the second diameter (D2) to the first diameter (D1).

  In Table 2, for each of the various combinations of first diameter (D1), second diameter (D2), first layer thickness (T1), and second layer thickness (T2), for the first diameter (D1). The ratio (D2 / D1) of the second diameter (D2) is listed in the upper row, and the evaluation results of the insulating properties in a high humidity atmosphere are listed in the lower row. As is apparent from the results shown in Table 2, the electric field strength of 20 V / μm is obtained only when the ratio (D2 / D1) of the second diameter (D2) to the first diameter (D1) is 0.12 or less. As a result of evaluation based on the current value, insulation in a high-humidity atmosphere of (Δ) or higher was achieved. Furthermore, in order to make the evaluation result of the insulating property in a high humidity atmosphere good (◯), the ratio (D2 / D1) of the second diameter (D2) to the first diameter (D1) is set to 0.07 or less. It was confirmed that there was a need.

  However, when the second layer thickness (T2) is 0.04 μm and the second diameter (D2) is 0.08 μm, and the second layer thickness (T2) is 0.04 μm and the second diameter (D2). Is 0.12 μm, the ratio (D2 / D1) of the second diameter (D2) to the first diameter (D1) (in each case 1.2 μm) is 0.12 or less (specifically, Despite being 0.07 and 0.11), the high-humidity insulation is poor (x). This is because, in these cases, the ratio (D2 / T2) of the second diameter (D2) to the second layer thickness (T2) is within an appropriate range (specifically, as described above, 1.5 or less). Since it deviates, it is thought that the insulation in a high humidity atmosphere deteriorated.

[A-2] Ratio of second diameter (D2) to second layer thickness (T2) (D2 / T2)
Next, the influence of the ratio (D2 / T2) of the second diameter (D2) to the second layer thickness (T2) on the insulation in a high humidity atmosphere will be considered. Therefore, in various combinations of the first diameter (D1), the second diameter (D2), the first layer thickness (T1), and the second layer thickness (T2) listed in Table 1, the insulating properties in a high humidity atmosphere Table 3 below lists the ratio (D2 / T2) of the second diameter (D2) to the second layer thickness (T2).

  In Table 3, the second layer thickness (T2) for each of the various combinations of the first diameter (D1), the second diameter (D2), the first layer thickness (T1), and the second layer thickness (T2). The ratio (D2 / T2) of the second diameter (D2) to the upper is listed in the upper row, and the evaluation results of the insulation in a high humidity atmosphere are listed in the lower row. As is clear from the results shown in Table 3, an electric field of 20 V / μm is obtained only when the ratio (D2 / T2) of the second diameter (D2) to the second layer thickness (T2) is 1.5 or less. As an evaluation result based on the current value in terms of strength, it was confirmed that insulation in a high humidity atmosphere of acceptable (Δ) or higher was achieved.

  However, when the second diameter (D2) is 0.20 μm and the second layer thickness (T2) is 0.18 μm to 1.50 μm, the second diameter (D2) with respect to the second layer thickness (T2). Ratio (D2 / T2) is 1.5 or less (specifically, 1.25, 1.00, 0.67, 0.50, 0.25, 0.17, and 0.13, respectively). Nevertheless, the high-humidity insulation is poor (x). In these cases, the ratio (D2 / D1) of the second diameter (D2) to the first diameter (D1) deviates from an appropriate range (specifically, as described above, 0.12 or less). Therefore, it is considered that the insulation in a high humidity atmosphere deteriorated.

  From the above considerations in A-1 and A-2, in order to improve the insulation (high-humidity insulation) in a high-humidity atmosphere, the second diameter (D2) with respect to the first diameter (D1) It was suggested that both the ratio (D2 / D1) and the ratio of the second diameter (D2) to the second layer thickness (T2) (D2 / T2) need to be in an appropriate range. Therefore, in the following A-3, various data in the above-described A-1 and A-2 are arranged, the ratio (D2 / D1) of the second diameter (D2) to the first diameter (D1) and the second layer. The high-humidity insulating properties in various combinations with the ratio (D2 / T2) of the second diameter (D2) to the thickness (T2) are evaluated again.

[A-3] High-humidity insulation in various combinations of D2 / D1 and D2 / T2 As described above, here, various data in the above-described A-1 and A-2 are arranged, and the first diameter High humidity insulation in various combinations of ratio (D2 / D1) of second diameter (D2) to (D1) and ratio (D2 / T2) of second diameter (D2) to second layer thickness (T2) Consider again. Therefore, FIG. 3 shows a graph summarizing the evaluation results of the high-humidity insulation in various combinations of D2 / D1 and D2 / T2 based on the data listed in Tables 1 and 2. In the graph shown in FIG. 3, the symbols displayed in the individual plots represent the evaluation results of insulating properties (good (◯), acceptable (Δ), and f-defective (×)) in a high humidity atmosphere, respectively. .

  As is clear from the graph shown in FIG. 3, in order to improve the insulation (high-humidity insulation) in a high-humidity atmosphere, the second diameter (D2) with respect to the first diameter (D1) It was confirmed that both the ratio (D2 / D1) and the ratio (D2 / T2) of the second diameter (D2) to the second layer thickness (T2) need to be in an appropriate range. Specifically, in order to improve the high-humidity insulation, the ratio (D2 / D1) of the second diameter (D2) to the first diameter (D1) is 0.12 or less, more preferably 0.8. And the ratio (D2 / T2) of the second diameter (D2) to the second layer thickness (T2) needs to be 1.5 or less.

B) Evaluation of insulation in a high humidity atmosphere As described above, even if the second piezoelectric / electrostrictive layer containing piezoelectric / electrostrictive ceramics is too thick, the first piezoelectric / electrostrictive layer is This may be a factor that hinders the piezoelectric displacement of the strained layer. Therefore, in this example, the magnitude of the piezoelectric displacement was measured for each of the various piezoelectric / electrostrictive actuators manufactured as described above. The piezoelectric displacement was determined by measuring the amount of displacement in the thickness direction when an electric field of 4 kV / mm was applied between the electrodes of each piezoelectric / electrostrictive actuator with a laser Doppler. The piezoelectric displacement [nm] thus obtained is converted into the first diameter (D1), the second diameter (D2), the first layer thickness (T1), and the second layer thickness (T2) in each piezoelectric / electrostrictive actuator. ) And the following values are listed in Table 4.

  As described above, in Table 4, each of the various combinations of the first diameter (D1), the second diameter (D2), the first layer thickness (T1), and the second layer thickness (T2) is described above. The piezoelectric displacements [nm] measured in this way are listed. In addition, as an evaluation standard of piezoelectric displacement, when the measured value was 345 nm or more, it was set as good ((circle)), and when it was less than 345 nm, it was set as bad (x). As is clear from the results shown in Table 4, only when the ratio (T2 / T1) of the second layer thickness (T2) to the first layer thickness (T1) is 0.11 or less, sufficient piezoelectric displacement is achieved. Was maintained. That is, when the second piezoelectric / electrostrictive layer is thickened so that the ratio (T2 / T1) of the second layer thickness (T2) to the first layer thickness (T1) exceeds 0.11, the first piezoelectric / electrostrictive layer is increased. It was confirmed that the piezoelectric displacement by the layer was inhibited.

  Although several embodiments having specific configurations have been described above for the purpose of illustrating the present invention, the scope of the present invention is not limited to these exemplary embodiments, and patents Needless to say, modifications can be made as appropriate within the scope of the claims and the description of the specification.

Claims (11)

Comprising at least one laminate comprising a first piezoelectric / electrostrictive layer comprising piezoelectric / electrostrictive ceramics and a pair of electrodes respectively disposed on both sides of the first piezoelectric / electrostrictive layer; An operation portion corresponding to a portion where the first piezoelectric / electrostrictive layer is sandwiched between the pair of electrodes, and the first piezoelectric / electrostrictive layer is not sandwiched between the pair of electrodes. A piezoelectric / electrostrictive actuator comprising a piezoelectric / electrostrictive element having a non-actuating part corresponding to a part,
In the laminate closest to the ambient atmosphere,
A second piezoelectric / electrostrictive layer comprising piezoelectric / electrostrictive ceramics between the electrode on the ambient atmosphere side and the first piezoelectric / electrostrictive layer;
A second diameter, which is an average value of the diameters of crystal grains of the piezoelectric / electrostrictive ceramics constituting the second piezoelectric / electrostrictive layer in a plane parallel to the main surface of the second piezoelectric / electrostrictive layer, is the first diameter. It is not more than 0.12 times the first diameter which is the average value of the diameters of the crystal grains of the piezoelectric / electrostrictive ceramics constituting the first piezoelectric / electrostrictive layer in a plane parallel to the main surface of the piezoelectric / electrostrictive layer. And the second diameter is not more than 1.5 times the second layer thickness which is the thickness in the normal direction of the main surface of the second piezoelectric / electrostrictive layer.
Piezoelectric / electrostrictive actuator. The piezoelectric / electrostrictive actuator according to claim 1,
The second diameter is 0.07 times or less of the first diameter;
Piezoelectric / electrostrictive actuator. The piezoelectric / electrostrictive actuator according to any one of claims 1 and 2,
The second layer thickness is not more than 0.11 times the first layer thickness which is the thickness in the normal direction of the main surface of the first piezoelectric / electrostrictive layer.
Piezoelectric / electrostrictive actuator. The piezoelectric / electrostrictive actuator according to any one of claims 1 to 3,
The second diameter is 0.20 μm or less;
Piezoelectric / electrostrictive actuator. The piezoelectric / electrostrictive actuator according to any one of claims 1 to 4,
The piezoelectric / electrostrictive element is disposed on a substrate;
Piezoelectric / electrostrictive actuator. The piezoelectric / electrostrictive actuator according to claim 5,
The substrate has a thin portion, and the piezoelectric / electrostrictive element is disposed so as to cover at least a part of the thin portion,
Piezoelectric / electrostrictive actuator. The piezoelectric / electrostrictive actuator according to claim 6,
The piezoelectric / electrostrictive element is fixed to a region corresponding to the thin portion on the substrate,
Piezoelectric / electrostrictive actuator. The piezoelectric / electrostrictive actuator according to any one of claims 5 to 7,
The substrate and the piezoelectric / electrostrictive element are fixed via the electrodes,
Piezoelectric / electrostrictive actuator. Comprising at least one laminate comprising a first piezoelectric / electrostrictive layer comprising piezoelectric / electrostrictive ceramics and a pair of electrodes respectively disposed on both sides of the first piezoelectric / electrostrictive layer; An operation portion corresponding to a portion where the first piezoelectric / electrostrictive layer is sandwiched between the pair of electrodes, and the first piezoelectric / electrostrictive layer is not sandwiched between the pair of electrodes. A piezoelectric / electrostrictive actuator comprising a piezoelectric / electrostrictive element having a non-actuating part corresponding to a part,
In the laminate closest to the ambient atmosphere,
A second piezoelectric / electrostrictive layer comprising piezoelectric / electrostrictive ceramics between the electrode on the ambient atmosphere side and the first piezoelectric / electrostrictive layer;
A second diameter, which is an average value of the diameters of crystal grains of the piezoelectric / electrostrictive ceramics constituting the second piezoelectric / electrostrictive layer in a plane parallel to the main surface of the second piezoelectric / electrostrictive layer, is the first diameter. It is not more than 0.12 times the first diameter which is the average value of the diameters of the crystal grains of the piezoelectric / electrostrictive ceramics constituting the first piezoelectric / electrostrictive layer in a plane parallel to the main surface of the piezoelectric / electrostrictive layer. And the second diameter is not more than 1.5 times the second layer thickness which is the thickness in the normal direction of the main surface of the second piezoelectric / electrostrictive layer.
Piezoelectric / electrostrictive actuator,
A manufacturing method of
The first piezoelectric / electrostrictive layer is formed by a solid phase reaction method involving heat treatment at a first temperature, which is a relatively high temperature,
The second piezoelectric / electrostrictive layer is formed by a thin film method involving heat treatment at a second temperature, which is a relatively low temperature.
A method for manufacturing a piezoelectric / electrostrictive actuator. A method for manufacturing a piezoelectric / electrostrictive actuator according to claim 9,
The first temperature is 800 ° C. or higher and lower than 1300 ° C .;
The second temperature is 500 ° C. or higher and lower than 700 ° C.,
A method for manufacturing a piezoelectric / electrostrictive actuator. A method for manufacturing a piezoelectric / electrostrictive actuator according to any one of claims 9 and 10,
The thin film method includes any one method selected from a sol-gel method and a sputtering method,
A method for manufacturing a piezoelectric / electrostrictive actuator.