JP2021012908A - Method for manufacturing piezoelectric laminate, piezoelectric element and piezoelectric laminate - Google Patents

Abstract

To prolong the life of a piezoelectric film made of an alkaline niobium oxide.SOLUTION: A piezoelectric laminate includes a substrate, an electrode film, and a polycrystalline film that is made of an alkaline niobium oxide having a perovskite structure represented by a composition formula (K1-xNax)NbO3(0<x<1), and the piezoelectric film includes Cu, and the amount of Cu present at the grain boundaries of the crystals constituting the piezoelectric film is larger than that of Cu existing in the matrix phase of the crystal.SELECTED DRAWING: Figure 1

Description

The present invention relates to a piezoelectric laminate, a piezoelectric element, and a method for manufacturing a piezoelectric laminate.

Piezoelectric bodies are widely used in functional electronic components such as sensors and actuators. As the material of the piezoelectric body, lead-based materials, in particular, ferroelectric PZT system represented by a composition formula _{Pb (Zr 1-x Ti x} ) O 3 has been widely used. Since the PZT-based piezoelectric material contains lead, it is not preferable from the viewpoint of pollution prevention. Therefore, sodium potassium niobate (KNN) has been proposed as a material for lead-free piezoelectric materials (see, for example, Patent Documents 1 and 2). In recent years, there has been a strong demand for further improving the performance of piezoelectric materials made of lead-free materials such as KNN.

JP-A-2007-184513 Japanese Unexamined Patent Publication No. 2008-159807

An object of the present invention is to further extend the life of a piezoelectric film made of an alkali niobium oxide.

According to one aspect of the invention
With the board
With the electrode film
A polycrystalline film comprising a piezoelectric film composed of an alkaline niobium oxide having a perovskite structure represented by the composition formula (K _1-x Na _x ) NbO ₃ (0 <x <1).
The piezoelectric film contains Cu and contains Cu.
Provided are a piezoelectric laminate in which Cu present in the grain boundaries of crystals constituting the piezoelectric film is larger than Cu present in the matrix phase of the crystal, and related techniques thereof.

According to the present invention, it is possible to further extend the life of the piezoelectric film made of an alkali niobium oxide.

It is a figure which shows an example of the cross-sectional structure of the piezoelectric laminated body which concerns on one Embodiment of this invention. It is a figure which shows the modification of the cross-sectional structure of the piezoelectric laminated body which concerns on one Embodiment of this invention. It is a figure which shows an example of the schematic structure of the piezoelectric device which concerns on one Embodiment of this invention. It is a figure which shows an example of the cross-sectional structure of the intermediate body (the laminate before heat treatment) at the time of producing the piezoelectric laminate which concerns on one Embodiment of this invention. It is a figure which shows the modification of the schematic structure of the piezoelectric device which concerns on one Embodiment of this invention.

<One Embodiment of the present invention>
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

(1) Configuration of piezoelectric laminate As shown in FIG. 1, the laminate (laminated substrate) 10 having the piezoelectric film according to the present embodiment (hereinafter, also referred to as piezoelectric laminate 10) is on the substrate 1 and the substrate 1. The lower electrode film 2 formed on the lower electrode film 2, the piezoelectric film (piezoelectric thin film) 3 formed on the lower electrode film 2, and the upper electrode film 4 formed on the piezoelectric film 3 are provided.

The substrate 1 is a single crystal silicon (Si) substrate 1a on which a surface oxide film (SiO ₂ film) 1b such as a thermal oxide film or a CVD (Chemical Vapor Deposition) oxide film is formed, that is, a Si substrate having a surface oxide film. Can be preferably used. Further, as the substrate 1, as shown in FIG. 2, a Si substrate 1a having an insulating film 1d formed of an insulating material other than SiO _{2 on} its surface can also be used. Further, as the substrate 1, a Si substrate 1a in which a Si (100) surface or a Si (111) surface or the like is exposed on the surface, that is, a Si substrate having no surface oxide film 1b or insulating film 1d can also be used. The substrate 1 is formed of a metal material such as an SOI (Silicon On Insulator) substrate, a quartz glass (SiO ₂ ) substrate, a gallium arsenide (GaAs) substrate, a sapphire (Al ₂ O ₃ ) substrate, and stainless steel (SUS). It is also possible to use a metal substrate. The thickness of the single crystal Si substrate 1a can be, for example, 300 to 1000 μm, and the thickness of the surface oxide film 1b can be, for example, 1 to 4000 nm.

The lower electrode film 2 can be formed by using, for example, platinum (Pt). The lower electrode film 2 is a single crystal film or a polycrystalline film (hereinafter, these are also referred to as Pt films). The crystals constituting the Pt film are preferably preferentially oriented in the (111) plane orientation with respect to the surface of the substrate 1. That is, it is preferable that the surface of the Pt film (the surface serving as the base of the piezoelectric film 3) is mainly composed of the Pt (111) surface. The Pt film can be formed by using a method such as a sputtering method or a thin film deposition method. In addition to Pt, the lower electrode film 2 includes various metals such as gold (Au), ruthenium (Ru), and iridium (Ir), alloys containing these as main components, strontium ruthenate (SrRuO ₃ , abbreviation: SRO), or It is also possible to form a film using a metal oxide such as lanthanum nickelate (LaNiO ₃ , abbreviated as LNO). In order to improve the adhesion between the substrate 1 and the lower electrode film 2, for example, titanium (Ti), tantalum (Ta), titanium oxide (TiO ₂ ), nickel (Ni), ruthenium oxide, etc. The adhesion layer 6 containing (RuO ₂ ), iridium oxide (IrO ₂ ), or the like as a main component may be provided. The adhesion layer 6 can be formed into a film by using a method such as a sputtering method or a thin film deposition method. The thickness of the lower electrode film 2 can be, for example, 100 to 400 nm, and the thickness of the adhesion layer 6 can be, for example, 1 to 200 nm.

The piezoelectric film 3 contains, for example, potassium (K), sodium (Na), and niobium (Nb), and is an alkaline niobium oxide represented by the composition formula (K _1-x Na _x ) NbO ₃ , that is, potassium niobate. A film can be formed using sodium (KNN). The coefficient x [= Na / (K + Na)] in the above composition formula has a magnitude within the range of 0 <x <1. The piezoelectric film 3 is a KNN polycrystalline film (hereinafter, also referred to as KNN film 3). The crystal structure of KNN is a perovskite structure. The KNN film 3 can be formed by using a method such as a sputtering method, a PLD (Pulsed Laser Deposition) method, or a sol-gel method. The thickness of the KNN film 3 is, for example, 0.5 to 5 μm.

The crystals constituting the KNN film 3 have priority in the (001) plane orientation with respect to the surface of the substrate 1 (Si substrate 1a when the substrate 1 is, for example, a Si substrate 1a having a surface oxide film 1b or an insulating film 1d). It is preferably oriented. That is, it is preferable that the surface of the KNN film 3 (the surface serving as the base of the upper electrode film 4) is mainly composed of the KNN (001) plane orientation. By directly forming the KNN film 3 on the Pt film preferentially oriented in the (111) plane direction with respect to the surface of the substrate 1, the crystals constituting the KNN film 3 are formed with respect to the surface of the substrate 1 (001). ) It becomes easy to preferentially orient the plane orientation. For example, 80% or more of the crystals constituting the KNN film 3 are oriented in the (001) plane orientation with respect to the surface of the substrate 1, and 80% or more of the surface of the KNN film 3 is KNN (001). ) It becomes easy to make a surface.

It is preferable that more than half of the crystals constituting the KNN film 3 have a columnar structure. It is preferable that the boundary between the crystals constituting the KNN film 3, that is, the grain boundary existing in the KNN film 3 penetrates in the thickness direction of the KNN film 3. For example, in the KNN film 3, the number of crystal grain boundaries penetrating in the thickness direction is larger than the grain boundaries not penetrating in the thickness direction of the KNN film 3 (for example, the grain boundaries parallel to the plane direction of the substrate 1). Is preferable.

The average particle size of the crystals (crystal group) constituting the KNN film 3 (hereinafter, also referred to as “average crystal grain size of the KNN film 3”) is preferably 100 nm or more, for example. The average crystal grain size of the KNN film 3 referred to here is the average crystal grain size of the KNN film 3 in the cross section of the substrate 1 in the plane direction. The average crystal grain size of the KNN film 3 can be obtained by image analysis of the field of view of an image taken with a scanning electron microscope (for example, SEM image) or an image taken with a transmission electron microscope (for example, TEM image). As the image analysis software, for example, "ImageJ" manufactured by Wayne Rasband can be used.

By increasing the average crystal grain size of the KNN film 3, it is possible to reduce the grain boundary density of the KNN film 3. The grain boundary density here is a value obtained by dividing the total length of crystal grain boundaries in the cross section of the KNN film 3 in the plane direction of the substrate 1 by the cross-sectional area (= total grain boundary length of crystal grains /). Cross-sectional area).

From the viewpoint of lowering the grain boundary density of the KNN film 3, the larger the average crystal grain size of the KNN film 3, the more preferable. However, if the average crystal grain size of the KNN film 3 is larger than the thickness of the KNN film 3, the in-plane uniformity of the piezoelectric characteristics may decrease. Therefore, from the viewpoint of suppressing the decrease in in-plane uniformity of the piezoelectric characteristics, the average crystal grain size of the KNN film 3 is preferably smaller than the thickness of the KNN film 3.

The KNN film 3 contains copper (Cu). In addition, in the KNN film 3, Cu is present at the crystal grain boundaries, and Cu existing at the crystal grain boundaries (for example, the number of Cu particles existing at the crystal grain boundaries) is the parent phase of the crystals constituting the KNN film 3. It is larger than the Cu present in (for example, the number of Cu particles present in the matrix). Therefore, when an electric field is applied to the piezoelectric element 20 (piezoelectric device 30) described later, it is possible to suppress the movement of oxygen deficiency existing at the crystal grain boundaries of the KNN film 3.

Oxygen deficiency (oxygen vacancy) is present at a predetermined ratio inside the crystals (crystal grains) constituting the KNN film 3 and at the crystal grain boundaries. Among these oxygen deficiencies, especially when the oxygen deficiency existing at the crystal grain boundary of the KNN film 3 applies an electric field to the piezoelectric element 20 (piezoelectric device 30) described later, which is produced by processing the piezoelectric laminate 10. May move to. When the oxygen deficiency moves and reaches the electrode film (lower electrode film 2 or upper electrode film 4), the oxygen deficiency reacts with the metal in the electrode film to cause a short circuit. Therefore, the inventors of the present application have diligently studied the suppression of the movement of oxygen deficiency existing at the grain boundaries of the KNN film 3. As a result, when Cu is present at the grain boundaries of the KNN film 3, this Cu is paired with the oxygen deficiency existing at the grain boundaries of the KNN film 3, that is, the Cu existing at the grain boundaries is oxygen deficient. It was found that the movement of oxygen deficiency existing at the grain boundary can be suppressed by trapping. Further, although such an effect of suppressing oxygen deficiency movement is obtained by Cu existing at the crystal grain boundary, it constitutes Cu (for example, KNN film 3) existing in the parent phase (inside the crystal) of the crystal constituting the KNN film 3. It was also found that it is difficult to obtain it depending on the Cu) incorporated in the lattice of the crystal. These findings are the first findings found as a result of diligent studies by the inventors of the present application.

The KNN film 3 preferably contains Cu at a concentration in the range of, for example, 0.2 at% or more and 2.0 at% or less. The Cu concentration referred to here is the total concentration of Cu existing at the grain boundaries and Cu existing in the matrix phase.

When the Cu concentration of the KNN film 3 is 0.2 at% or more, even if the Cu content in the KNN film 3 is very small, a certain amount or more of Cu can be present at the grain boundaries and the grain boundaries can be present. It is possible to increase the amount of Cu present in the parent phase to that of Cu present in the parent phase. As a result, the above-mentioned effect of suppressing oxygen deficiency movement can be obtained. When the Cu concentration of the KNN film 3 is 2.0 at% or less, the relative permittivity of the KNN film 3 can be set to a size suitable for applications such as sensors and actuators.

The KNN film 3 does not impair the effect of adding elements other than K, Na, Nb and Cu such as manganese (Mn), lithium (Li), Ta and antimony (Sb) within the above range. It may be contained within the range, for example, 5 at% or less (when a plurality of the above-mentioned elements are added, the total concentration is 5 at% or less).

The upper electrode film 4 can be formed by using various metals such as Pt, Au, aluminum (Al), and Cu, or alloys thereof. The upper electrode film 4 can be formed by using a method such as a sputtering method, a vapor deposition method, a plating method, or a metal paste method. The upper electrode film 4 does not have a great influence on the crystal structure of the KNN film 3 like the lower electrode film 2. Therefore, the material, crystal structure, and film forming method of the upper electrode film 4 are not particularly limited. In order to enhance the adhesion between the KNN film 3 and the upper electrode film 4, for example, an adhesion layer containing Ti, Ta, TiO ₂ , Ni, RuO ₂ , IrO _2, etc. as main components is provided. It may have been. The thickness of the upper electrode film 4 can be, for example, 100 to 5000 nm, and when the adhesion layer is provided, the thickness of the adhesion layer can be, for example, 1 to 200 nm.

(2) Configuration of Piezoelectric Device FIG. 3 shows a schematic configuration diagram of the device 30 having the KNN film 3 (hereinafter, also referred to as the piezoelectric device 30) in the present embodiment. The piezoelectric device 30 is connected to an element 20 (element 20 having a KNN film 3; hereinafter, also referred to as a piezoelectric element 20) obtained by molding the above-mentioned piezoelectric laminate 10 into a predetermined shape, and the piezoelectric element 20. It includes at least a voltage application unit 11a or a voltage detection unit 11b. The voltage application unit 11a is a means for applying a voltage between the lower electrode film 2 and the upper electrode film 4 (between the electrodes), and the voltage detection unit 11b is the lower electrode film 2 and the upper electrode film 4 It is a means for detecting the voltage generated between the electrodes (between the electrodes). As the voltage application unit 11a and the voltage detection unit 11b, various known means can be used.

By connecting the voltage application unit 11a between the lower electrode film 2 and the upper electrode film 4 of the piezoelectric element 20, the piezoelectric device 30 can function as an actuator. The KNN film 3 can be deformed by applying a voltage between the lower electrode film 2 and the upper electrode film 4 by the voltage applying portion 11a. By this deformation operation, various members connected to the piezoelectric device 30 can be operated. In this case, examples of the use of the piezoelectric device 30 include a head for an inkjet printer, a MEMS mirror for a scanner, an oscillator for an ultrasonic generator, and the like.

By connecting the voltage detection unit 11b between the lower electrode film 2 and the upper electrode film 4 of the piezoelectric element 20, the piezoelectric device 30 can function as a sensor. When the KNN film 3 is deformed due to some change in physical quantity, a voltage is generated between the lower electrode film 2 and the upper electrode film 4 due to the deformation. By detecting this voltage by the voltage detection unit 11b, the magnitude of the physical quantity applied to the KNN film 3 can be measured. In this case, applications of the piezoelectric device 30 include, for example, an angular velocity sensor, an ultrasonic sensor, a pressure sensor, an acceleration sensor, and the like.

(3) Method for Manufacturing Piezoelectric Laminate, Piezoelectric Element, and Piezoelectric Device The method for manufacturing the above-mentioned piezoelectric laminate 10, the piezoelectric element 20, and the piezoelectric device 30 will be described with reference to FIG.

As shown in FIG. 4, first, a substrate 1 is prepared, and an adhesion layer 6 (Ti layer) and a lower electrode film 2 (Pt film) are formed in this order on one of the main surfaces of the substrate 1 by, for example, a sputtering method. Membrane. A substrate 1 on which the adhesion layer 6 and the lower electrode film 2 are formed in advance may be prepared on any of the main surfaces.

The following conditions are exemplified as the conditions for providing the adhesion layer 6.
Temperature (Substrate temperature): 100 ° C or higher and 500 ° C or lower, preferably 200 ° C or higher and 400 ° C or lower Discharge power: 1000 W or higher and 1500 W or lower, preferably 1100 W or higher and 1300 W or lower Atmosphere: Argon (Ar) Gas atmosphere Atmospheric pressure: 0.1 Pa or higher 0.5 Pa or less, preferably 0.2 Pa or more and 0.4 Pa or less Formation time: 30 seconds or more and 3 minutes or less, preferably 45 seconds or more and 2 minutes or less

The following conditions are exemplified as the conditions for forming the lower electrode film 2.
Temperature (Substrate temperature): 100 ° C or higher and 500 ° C or lower, preferably 200 ° C or higher and 400 ° C or lower Discharge power: 1000 W or higher and 1500 W or lower, preferably 1100 W or higher and 1300 W or lower Below, preferably 0.2 Pa or more and 0.4 Pa or less, film forming time: 3 minutes or more and 10 minutes or less, preferably 4 minutes or more and 8 minutes or less, more preferably 5 minutes or more and 6 minutes or less.

Subsequently, a layer containing Cu is provided on the lower electrode film 2, that is, at a position where it comes into contact with the lower surface of the KNN film 3. Examples of the layer containing Cu include a KNN film containing Cu. Hereinafter, the layer containing Cu provided on the lower electrode film 2 is also referred to as a first Cu layer 7. The first Cu layer 7 is a single crystal layer or a polycrystalline layer. The first Cu layer 7 can be provided by using a method such as a sputtering method or a vapor deposition method. The thickness of the first Cu layer 7 can be, for example, 1 to 200 nm. The Cu concentration in the first Cu layer will be described later.

When a KNN film containing Cu as the first Cu layer 7 is formed by, for example, a sputtering method, the composition ratio of the first Cu layer 7 can be adjusted, for example, by controlling the composition of the target material used during the sputtering film formation. The target material can be produced by mixing K ₂ CO ₃ powder, Na ₂ CO ₃ powder, Nb ₂ O ₅ powder, Cu powder (or Cu O powder, Cu ₂ O powder) and the like and firing them. The composition of the target material can be controlled by adjusting the mixing ratio of K ₂ CO ₃ powder, Na ₂ CO ₃ powder, Nb ₂ O ₅ powder, and Cu powder (or Cu O powder, Cu ₂ O powder).

The following conditions are exemplified as conditions for providing a KNN film containing Cu as the first Cu layer 7 by, for example, a sputtering method. The film forming time is appropriately set according to the thickness of the first Cu layer.
Discharge power: 2000 W or more and 2400 W or less, preferably 2100 W or more and 2300 W or less Atmosphere: Ar gas + oxygen (O ₂ ) Gas atmosphere Atmospheric pressure: 0.2 Pa or more and 0.5 Pa or less, preferably 0.2 Pa or more and 0.4 Pa or less O ₂ Partial pressure of Ar gas to gas (Ar / O ₂ partial pressure ratio): 30/1 to 20/1, preferably 27/1 to 22/1
Film formation rate: 0.5 μm / hr or more and 2 μm / hr or less, preferably 0.75 μm / hr or more and 1.5 μm / hr or less

A Cu-free KNN film (Cu-free KNN film) 3A is formed on the first Cu layer 7. When the Cu-free KNN film 3A is formed by, for example, a sputtering method, the composition ratio of the Cu-free KNN film 3A can be adjusted by controlling the composition of the target material used during the sputtering film formation, for example. The target material can be produced by mixing K ₂ CO ₃ powder, Na ₂ CO ₃ powder, Nb ₂ O ₅ powder and the like and firing them. The composition of the target material can be controlled by adjusting the mixing ratio of K ₂ CO ₃ powder, Na ₂ CO ₃ powder, and Nb ₂ O ₅ powder. The conditions for forming the KNN film 3 can be the same as the conditions for providing the first Cu layer 7 described above.

A layer containing Cu or a layer made of Cu is provided on the Cu-free KNN film 3A, that is, at a position in contact with the upper surface of the Cu-free KNN film 3A. Hereinafter, the layer containing Cu or the layer made of Cu provided on the Cu-free KNN film 3A is also referred to as a second Cu layer 8. Unlike the first Cu layer 7, the second Cu layer 8 does not significantly affect the crystal structure of the Cu-free KNN film 3A. Therefore, the material, crystal structure, and film forming method of the second Cu layer 8 are not particularly limited. The second Cu layer 8 can be provided by using a method such as a sputtering method, a vapor deposition method, or a metal paste method. The thickness of the second Cu layer 8 can be, for example, 1 to 200 nm. The Cu concentration in the second Cu layer 8 when the second Cu layer 8 is a layer containing Cu will be described later.

The conditions for providing the layer containing Cu as the second Cu layer 8 by, for example, the sputtering method can be the same as the conditions for providing the first Cu layer 7 described above.

In addition, the following conditions are exemplified as conditions for forming a layer made of Cu as the second Cu layer.
Temperature (board temperature): Room temperature or more and 300 ° C. or less, preferably room temperature or more and 100 ° C. or less Discharge power: 100 W or more and 500 W or less, preferably 150 W or more and 300 W or less, more preferably 200 W or more and 250 W or less Atmosphere: Ar Gas atmosphere Atmosphere pressure: 0 .05 Pa or more and 0.5 Pa or less, preferably 0.05 Pa or more and 0.2 Pa or less Formation time: 30 seconds or more and 3 minutes or less, preferably 45 seconds or more and 2 minutes or less

The Cu concentration in the first Cu layer 7 and the Cu concentration in the second Cu layer 8 when the second Cu layer 8 is a layer containing Cu are the first Cu layer 7 and the second Cu layer 8 when the heat treatment described later is performed. The Cu concentration in the KNN film 3 after the heat treatment is adjusted to a concentration that can be within the range of 0.2 at% or more and 2.0 at% or less by Cu diffusion from the above.

Then, the upper electrode film 4 is formed on the second Cu layer 8 by, for example, a sputtering method. The conditions for forming the upper electrode film 4 can be the same as the conditions for forming the lower electrode film 2 described above. As a result, as shown in FIG. 4, a laminate 12 having the substrate 1, the lower electrode film 2, the first Cu layer 7, the KNN film 3, the second Cu layer 8, and the upper electrode film 4 is obtained.

Then, the laminated body 12 is heat-treated under predetermined conditions. As a result, Cu in the first Cu layer 7 and the second Cu layer 8 diffuses into the Cu-free KNN film 3A. As a result, the Cu-free KNN film 3A is a film containing Cu at a predetermined concentration, and is a KNN film in which Cu is present at the grain boundaries and more Cu is present at the grain boundaries than Cu is present in the parent phase. It becomes 3.

The following conditions are exemplified as the heat treatment conditions.
Annealing temperature (temperature of laminated body): 600 ° C. or higher, preferably 600 ° C. or higher and 800 ° C. or lower, more preferably 650 ° C. or higher and 750 ° C. or lower Annealing time: 0.5 hours or more and 12 hours or less, preferably 1 hour or more and 6 hours Below, more preferably 2 hours or more and 3 hours or less Annealing atmosphere: Atmospheric or nitrogen atmosphere

By performing the heat treatment, Cu in the first Cu layer 7 and the second Cu layer 8 diffuses into the Cu-free KNN film 3A, so that the first Cu layer 7 and the second Cu layer 8 are almost eliminated. As a result, the piezoelectric laminate 10 (see FIG. 1) having the substrate 1, the lower electrode film 2, the KNN film 3, and the upper electrode film 4 contains Cu and Cu existing at the grain boundaries is used as the parent phase. A piezoelectric laminate 10 having more KNN films 3 than existing Cu can be obtained. It is preferable that the first Cu layer 7 and the second Cu layer 8 disappear by performing the heat treatment, but the first Cu layer 7 and the second Cu layer 8 may remain.

Then, by molding the piezoelectric laminate 10 into a predetermined shape by etching or the like, the piezoelectric element 20 as shown in FIG. 3 is obtained, and the voltage application unit 11a or the voltage detection unit 11b is connected to the piezoelectric element 20. Then, the piezoelectric device 30 is obtained.

(4) Effects obtained by the present embodiment According to the present embodiment, one or more of the following effects can be obtained.

(A) Cu (for example, Cu particles) is present at the grain boundaries of the KNN film 3, and Cu existing at the grain boundaries of the KNN film 3 is present in the matrix of the crystals constituting the KNN film 3. Since it is more than Cu, it suppresses the movement of oxygen deficiency existing at the grain boundaries of the KNN film 3 when an electric field is applied to the piezoelectric element 20 (piezoelectric device 30) produced by processing the piezoelectric laminate 10. It becomes possible to do. This makes it possible to reduce the oxygen deficiency reaching the electrode film (lower electrode film 2 or upper electrode film 4) and to lengthen the time until the oxygen deficiency reaches the electrode film. As a result, the life of the KNN film 3 can be extended. For example, a high-accelerated life test (abbreviated as Highly Accelerated Life Test) in which a positive or negative electric field of 300 kV / cm is applied to the upper electrode film 4 while the piezoelectric laminate 10 is heated to a temperature of 200 ° C. : When HALT) is performed, the time from the start of electric field application under at least one electric field (positive or negative electric field) application condition to the dielectric breakdown of the KNN film 3 can be set to 7600 seconds or more. In this embodiment, it is considered that the KNN film 3 has undergone dielectric breakdown when the leakage current density flowing through the KNN film 3 exceeds 30 mA / cm ² .

The inventors of the present application have described each of Samples 1 to 5 of the KNN film 3 having a Cu content of 0.5 at% (wt%) and having more Cu present at the grain boundaries than Cu present at the parent phase. , HALT was performed under the above conditions. Samples 1 to 5 are prepared under the same conditions within the condition range described in the above-described embodiment. The HALT measurement results were sample 1: 7663 seconds, sample 2: 20057 seconds, sample 3: 32966 seconds, sample 4: 27566 seconds, and sample 5: 31937 seconds. The above-mentioned HALT value is the average of the values measured at 7 points within 0.5 mmφ per sample. The average HALT measurement result of Samples 1 to 5 is 240877.8 seconds.

Further, the inventors of the present application have described above for each of the samples 6 to 11 of the KNN film 3 having a Cu content of 1.0 at% and having more Cu present at the grain boundaries than Cu present at the parent phase. HALT was performed under the conditions. Samples 6 to 11 are prepared under the same conditions within the condition range described in the above-described embodiment. The HALT measurement results were sample 6: 30806 seconds, sample 7: 45309 seconds, sample 8: 23811 seconds, sample 9: 33069 seconds, sample 10: 30420 seconds, and sample 11: 35229 seconds. The above-mentioned HALT value is the average of the values measured at 7 points within 0.5 mmφ per sample. The average HALT measurement result of Samples 6 to 11 is 3310.7.33 seconds.

Further, the inventors of the present application have described above for each of the samples 12 to 17 of the KNN film 3 having a Cu content of 1.0 at% and having more Cu present at the grain boundaries than Cu present at the parent phase. HALT was performed under the conditions. Samples 12 to 17 are prepared under the same conditions within the condition range described in the above-described embodiment. The HALT measurement results were sample 12:24223 seconds, sample 13:33583 seconds, sample 14:49063 seconds, sample 15:38160 seconds, sample 16:54823 seconds, and sample 17:26331 seconds. The above-mentioned HALT value is the average of the values measured at 7 points within 0.5 mmφ per sample. The average HALT measurement result of Samples 12 to 17 is 3769.6.17 seconds.

On the other hand, the inventor of the present application has confirmed that the result of performing HALT under the above conditions for the KNN film in which Cu does not exist at the grain boundaries is less than 7600 seconds.

(B) By making the average crystal grain size of the KNN film 3 larger than the average crystal grain size of the conventional KNN film, for example, 100 nm or more, the grain boundary density of the KNN film 3 can be lowered. As a result, for example, the ratio of oxygen deficiency existing at the grain boundary of the KNN film 3 to the oxygen deficiency existing inside the crystal constituting the KNN film 3 and at the grain boundary (total oxygen deficiency in the KNN film 3) (= It is possible to reduce the oxygen deficiency / total oxygen deficiency existing at the grain boundaries). As a result, oxygen deficiency in the KNN film 3 that moves when an electric field is applied to the piezoelectric device 30 can be reliably reduced, and the life of the KNN film 3 can be further extended.

(C) The KNN film 3 has more Cu present at the grain boundaries of the KNN film 3 than the Cu present in the parent phase, and the average crystal grain size of the KNN film 3 is large (for example, 100 nm or more). It is possible to further extend the life of the. Since the amount of Cu existing at the grain boundaries of the KNN film 3 is larger than that of Cu existing in the parent phase, even if the average crystal grain size of the KNN film 3 is not large (for example, even if it is less than 100 nm). ), At least the above-mentioned effect (a), that is, the above-mentioned oxygen deficiency movement suppressing effect can be obtained.

(D) When the KNN film 3 contains Cu at a concentration of, for example, 0.2 at% or more and 2.0 at% or less, the relative permittivity of the KNN film 3 is obtained while obtaining the effect of suppressing oxygen deficiency movement due to Cu existing at the grain boundaries. It is possible to make the rate suitable for applications such as sensors and actuators.

(5) Modification Example This embodiment is not limited to the above-described embodiment, and can be modified as follows. Moreover, these modified examples can be arbitrarily combined.

(Modification example 1)
At least one of the first Cu layer 7 and the second Cu layer 8 may be provided. In this case, the Cu concentration in the first Cu layer 7 or the second Cu layer 8 is adjusted so that the Cu concentration of the KNN film 3 after the heat treatment is 0.2 at% or more and 2.0 at% or less. Also in this modification, it is possible to obtain the KNN film 3 in which the amount of Cu existing at the grain boundaries is larger than that of Cu existing in the matrix phase, and the same effect as that of the above-described embodiment can be obtained. However, from the viewpoint of uniformly diffusing Cu over the thickness direction of the KNN film 3, it is preferable to provide both the first Cu layer 7 and the second Cu layer 8.

(Modification 2)
When the adhesion layer is provided between the KNN film 3 and the upper electrode film 4, it is preferable to provide the second Cu layer 8 before providing the adhesion layer. The second Cu layer 8 is preferably provided between the KNN film 3 (Cu-free KNN film 3A) and the adhesion layer, that is, in contact with the upper surface of the KNN film 3. This is because if the second Cu layer 8 is provided between the adhesion layer and the upper electrode film 4, the adhesion layer may inhibit the diffusion of Cu from the second Cu layer 8 to the KNN film 3. The conditions for providing the adhesion layer between the KNN film 3 and the upper electrode film 4 can be the same as the conditions for providing the adhesion layer 6 described above. In this modification as well, the same effect as that of the above-described embodiment can be obtained.

(Modification 3)
When forming a film of the KNN layer 3 may be made of Cu powder (or CuO powder, Cu ₂ O powder) target material obtained by mixing. Cu powder (or CuO powder, Cu ₂ O powder) in the target material during the mixing ratio of the first 1Cu layer 7, taking into account the Cu diffused from the 2Cu layer 8 to KNN layer 3 (Cu-free KNN film 3A) The Cu concentration in the KNN film 3 after the heat treatment is set to 0.2 at% or more and 2.0 at% or less. The conditions for forming the KNN film 3 can be the same as those in the above-described embodiment. In this modification as well, the same effect as that of the above-described embodiment can be obtained.

(Modification example 4)
The piezoelectric laminate 10 does not have to include the lower electrode film 2. That is, the piezoelectric laminate 10 is formed on the substrate 1 and the substrate 1, and the Cu present at the crystal grain boundary is larger than the Cu present in the parent phase on the KNN film (piezoelectric film) 3 and the KNN film 3. The upper electrode film 4 (electrode film 4) formed in the film may be provided.

In the piezoelectric laminate 10 according to this modification, a Cu-free KNN film 3A is formed on the substrate 1, and a layer containing Cu or a layer made of Cu, that is, a second Cu layer 8 is formed on the Cu-free KNN film 3A. It can be obtained by forming an electrode film 4 on the second Cu layer 8 to prepare a laminated body 12 and heat-treating the laminated body 12. The conditions for forming (providing) each film (layer) can be the same as the conditions for each film (layer) shown in the above-described embodiment. A layer containing Cu (that is, a first Cu layer 7) may be provided between the substrate 1 and the KNN film 3 (Cu-free KNN film 3A) in addition to or in place of the second Cu layer 8. Good.

FIG. 5 shows a schematic configuration diagram of a piezoelectric device 30 manufactured by using the piezoelectric laminate 10 according to this modification. The piezoelectric device 30 is configured to include at least a piezoelectric element 20 obtained by molding the piezoelectric laminate 10 into a predetermined shape, and a voltage applying unit 11a and a voltage detecting unit 11b connected to the piezoelectric element 20. .. In this modification, the piezoelectric element 20 has a pattern electrode formed by molding the electrode film 4 into a predetermined pattern. For example, the piezoelectric element 20 has a pair of positive and negative pattern electrodes 4p ₁ on the input side and a pair of positive and negative pattern electrodes 4p ₂ on the output side. Examples of the pattern electrodes 4p ₁ and 4p ₂ include comb-shaped electrodes (Inter Digital Transducer, abbreviation: IDT).

By connecting the voltage application unit 11a between the pattern electrodes 4p ₁ and the voltage detection unit 11b between the pattern electrodes 4p ₂ , the piezoelectric device 30 is connected to a filter such as a surface acoustic wave (SAW) filter. It can function as a device. By applying a voltage between the pattern electrode 4p ₁ by the voltage application section 11a, it is possible to excite the SAW in the surface of the KNN layer 3. Adjustment of SAW frequencies excite can be carried out by adjusting, for example, the pitch of the pattern electrodes 4p _1. For example, the shorter the pitch of the IDT as the pattern electrode 4p ₁ , the higher the SAW frequency, and the longer the pitch, the lower the SAW frequency. Of the SAWs that are excited by the voltage application unit 11a and propagate through the KNN film 3 to reach the pattern electrode 4p ₂ , the SAW has a predetermined frequency (frequency component) determined according to the pitch of the IDT as the pattern electrode 4p _2. As a result, a voltage is generated between the pattern electrodes 4p ₂ . By detecting this voltage by the voltage detection unit 11b, it is possible to extract the SAW having a predetermined frequency from the excited SAWs. The term "predetermined frequency" here may include not only a predetermined frequency but also a predetermined frequency band in which the center frequency is a predetermined frequency.

Also in this modification, since the amount of Cu present at the grain boundaries of the KNN film 3 is larger than that of Cu present at the parent phase, the same effect as that of the above-described embodiment can be obtained.

(Modification 5)
An orientation control layer that controls the orientation of the crystals constituting the KNN film 3 may be provided between the lower electrode film 2 and the KNN film 3. When the first Cu layer 7 is provided, it is preferable to provide an orientation control layer between the lower electrode film 2 and the first Cu layer 7. Further, when the lower electrode film 2 is not provided as described in the modified example 4, between the substrate 1 and the KNN film 3 (when the first Cu layer 7 is provided, between the substrate 1 and the first Cu layer 7). It is preferable to provide an orientation control layer. The orientation control layer may be formed by using a metal oxide such as SRO, LNO, strontium titanate (SrTiO ₃ , abbreviation: STO), which is different from the material constituting the lower electrode film 2. it can. It is preferable that the crystals constituting the orientation control layer are preferentially oriented toward the (100) plane with respect to the surface of the substrate 1.

(Modification 6)
In the above-described embodiment and modification, a case where the first Cu layer 7 and the second Cu layer 8 are provided and heat treatment is performed to diffuse Cu into the KNN film 3 has been described as an example. However, the present invention is not limited to the above-described embodiments and modifications. For example, instead of providing the first Cu layer 7 and the second Cu layer 8, or in addition to providing at least one of the first Cu layer 7 and the second Cu layer 8, the lower electrode film 2 and the upper electrode film 4 ( Cu may be contained in at least one of the electrode films 4). At this time, Cu is contained in the side close to the upper surface of the lower electrode film 2 (the surface in contact with the KNN film 3), preferably the uppermost surface of the lower electrode film 2, and the lower surface of the upper electrode film 4 (the surface in contact with the KNN film 3). ), It is preferable that Cu is contained in the lowermost surface of the upper electrode film 4. The Cu concentration contained in the lower electrode film 2 and the upper electrode film 4 is such that the Cu concentration of the KNN film 3 after the heat treatment can be, for example, 0.2 at% or more and 2.0 at% or less. When Cu is contained in the upper electrode film 4 in this modification, it is preferable not to provide an adhesion layer between the KNN film 3 and the upper electrode film 4. This is because, as described above, the adhesion layer may inhibit the diffusion of Cu into the KNN film 3. Other configurations are the same as those of the above-described embodiments and modifications.

Also in this modified example, Cu in the lower electrode film 2 and the upper electrode film 4 (electrode film 4) can be diffused into the KNN film 3 by performing the same heat treatment as in the above-described embodiment. As a result, the piezoelectric laminate 10 having the KNN film 3 in which Cu is present at the crystal grain boundaries can be obtained, and the same effects as those of the above-described embodiments and modifications can be obtained.

(Modification 7)
In the above-described embodiment and modification, by providing at least one layer of the first Cu layer 7 or the second Cu layer 8 and performing heat treatment, Cu existing at the grain boundaries is more than Cu existing in the matrix phase. The case where a large number of KNN films 3 are produced has been described as an example. However, the present invention is not limited to the above-described embodiments and modifications. For example, the above-mentioned piezoelectric laminate 10 can be produced by the production method described below without providing any of the above-mentioned first Cu layer 7 and second Cu layer 8.

First, a KNN film 3 to which Cu is added (doped) is formed on the lower electrode film 2 of the substrate 1. The method and conditions for forming the Cu-doped KNN film 3 can be the same as the methods and conditions described in the above-described embodiment and modification 3. Then, the upper electrode film 4 is formed on the KNN film 3. The conditions for forming (providing) the adhesion layer 6, the lower electrode film 2, and the upper electrode film 4 can be the same as those in the above-described embodiment. As a result, the laminated body 12 is obtained. Then, the laminated body 12 is heat-treated under predetermined conditions. The heat treatment conditions can be the same as those in the above-described embodiment. After the heat treatment, the laminate 12 is cooled over 20 minutes or more until the temperature of the laminate 12 reaches 400 ° C. Then, the laminate 12 is cooled until the temperature of the laminate 12 reaches about room temperature (25 ° C.). By cooling the laminate 12 in this way, a piezoelectric laminate 10 having a KNN film 3 having more Cu present at the grain boundaries than Cu present at the matrix can be obtained. The piezoelectric laminate 10 produced by the method according to this modification also has the same effect as that of the above-described embodiment.

<Other embodiments>
The embodiments of the present invention have been specifically described above. However, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist thereof.

For example, the KNN film 3 in which the amount of Cu present at the grain boundaries is larger than that of Cu present in the parent phase may be produced by using a method such as the Cu decoration method. Specifically, first, as the substrate 1, for example, a single crystal Si substrate 1a on which the surface oxide film 1b is formed is used to prepare a laminate having at least a lower electrode film 2, a KNN film 3, and an upper electrode film 4. To do. Alternatively, the single crystal Si substrate 1a is used to prepare a laminate having at least the KNN film 3 and the electrode film 4. Then, the laminate and the platinum plate are immersed in an aqueous solution of copper (II) sulfate (CuSO ₄ ), the surface oxide film 1b of the Si substrate 1a is used as a cathode, and the platinum plate is used as an anode to apply an electric field to each electrode. Apply. As a result, Cu is precipitated at the crystal grain boundaries of the KNN film 3, and a piezoelectric laminate 10 having a KNN film 3 having more Cu present at the crystal grain boundaries than Cu existing at the matrix can be obtained. Even in this case, the same effect as that of the above-described embodiment and modification can be obtained.

Further, for example, the KNN film 3 has a relative permittivity of the KNN film 3 while obtaining the above-mentioned oxygen deficiency movement suppressing effect by adding another metal element having the same effect as Cu in addition to or changing to Cu. May be contained in a concentration capable of making an appropriate size. Even in this case, the same effect as that of the above-described embodiment and modification can be obtained.

Further, for example, when the above-mentioned piezoelectric laminate 10 is molded into the piezoelectric element 20, the piezoelectric device 30 manufactured by using the piezoelectric laminate 10 (piezoelectric element 20) can be applied to a desired application such as a sensor or an actuator. As long as the substrate 1 may be removed from the piezoelectric laminate 10.

<Preferable Aspect of the Present Invention>
Hereinafter, preferred embodiments of the present invention will be added.

(Appendix 1)
According to one aspect of the invention
With the board
With the electrode film
A polycrystalline film comprising a piezoelectric film composed of an alkaline niobium oxide having a perovskite structure represented by the composition formula (K _1-x Na _x ) NbO ₃ (0 <x <1).
The piezoelectric film contains copper (Cu) and contains
Provided is a piezoelectric laminate in which Cu present at the grain boundaries of the crystals constituting the piezoelectric film is larger than Cu present in the matrix phase of the crystals.

(Appendix 2)
According to another aspect of the invention
With the board
With the electrode film
A polycrystalline film comprising a piezoelectric film composed of an alkaline niobium oxide having a perovskite structure represented by the composition formula (K _1-x Na _x ) NbO ₃ (0 <x <1).
Provided is a piezoelectric laminate in which copper (Cu) is decorated at the grain boundaries of the crystals constituting the piezoelectric film.

(Appendix 3)
The piezoelectric laminate of Appendix 1 or 2, preferably.
When a positive or negative electric field of 300 kV / cm is applied to the electrode film provided on the piezoelectric film at a temperature of 200 ° C., the current flows to the piezoelectric film from the start of electric field application under at least one electric field application condition. It takes 7600 seconds or more for the leakage current density to exceed 30 mA / cm ² .

(Appendix 4)
It is a piezoelectric laminate according to any one of Appendix 1 to 3, preferably.
The piezoelectric film is composed of crystal grains having an average particle size of 100 nm or more.

(Appendix 5)
It is a laminated body according to any one of Appendix 1 to 4, and is preferable.
The piezoelectric film contains Cu at a concentration of 0.2 at% or more and 2.0 at% or less.

(Appendix 6)
According to yet another aspect of the invention.
With the board
A piezoelectric film formed on the substrate, which is a polycrystalline film and is composed of an alkaline niobium oxide having a perovskite structure represented by the composition formula (K _1-x Na _x ) NbO ₃ (0 <x <1). ,
An electrode film formed on the piezoelectric film and
The piezoelectric film contains Cu and contains Cu.
Provided is a piezoelectric element or piezoelectric device in which the amount of Cu present at the grain boundaries of the crystals constituting the piezoelectric film is larger than that of Cu present in the matrix phase of the crystals.

(Appendix 7)
According to yet another aspect of the invention.
With the board
The lower electrode film formed on the substrate and
A piezoelectric film formed on the lower electrode film, which is a polycrystalline film and is composed of an alkaline niobium oxide having a perovskite structure represented by the composition formula (K _1-x Na _x ) NbO ₃ (0 <x <1). Membrane and
An upper electrode film formed on the piezoelectric film is provided.
The piezoelectric film contains Cu and contains Cu.
Provided is a piezoelectric element or piezoelectric device in which the amount of Cu present at the grain boundaries of the crystals constituting the piezoelectric film is larger than that of Cu present in the matrix phase of the crystals.

(Appendix 8)
According to yet another aspect of the invention.
A step of forming a piezoelectric film which is a polycrystalline film and is made of an alkali niobium oxide having a perovskite structure represented by the composition formula (K _1-x Na _x ) NbO ₃ (0 <x <1) on the substrate. When,
A step of providing a layer containing Cu or a layer made of Cu on the piezoelectric film, and
The step of forming an electrode film on the layer containing Cu or the layer made of Cu, and
A step of heat-treating a laminate including the substrate, the piezoelectric film, a layer containing the Cu, or a layer made of the Cu, and the electrode film.
By carrying out the step of performing the heat treatment, Cu in the layer containing Cu or the layer composed of Cu is diffused into the piezoelectric film, and the piezoelectric film is made into a crystal containing Cu and constituting the piezoelectric film. Provided is a method for producing a piezoelectric laminate in which the amount of Cu present in the grain boundary of the crystal is larger than that of Cu present in the matrix of the crystal.

(Appendix 9)
According to yet another aspect of the invention.
The process of forming the lower electrode film on the substrate and
On the lower electrode film, a piezoelectric film which is a polycrystalline film and is made of an alkali niobium oxide having a perovskite structure represented by the composition formula (K _1-x Na _x ) NbO ₃ (0 <x <1) is produced. The process of filming and
The process of forming an upper electrode film on the piezoelectric film and
It has a step of performing a heat treatment on a laminate including the substrate, the lower electrode film, the piezoelectric film, and the upper electrode film.
Before the step of forming the piezoelectric film, a step of providing a layer containing Cu so as to be in contact with the lower surface of the piezoelectric film, or after performing a step of forming the piezoelectric film, the piezoelectric film of the piezoelectric film is formed. At least one of the steps of providing a layer containing Cu or a layer made of Cu so as to be in contact with the upper surface is performed.
By carrying out the step of performing the heat treatment, Cu in the layer containing Cu or the layer composed of Cu is diffused into the piezoelectric film, and the piezoelectric film is made into a crystal containing Cu and constituting the piezoelectric film. Provided is a method for producing a piezoelectric laminate in which the amount of Cu present in the grain boundary of the crystal is larger than that of Cu present in the matrix of the crystal.

(Appendix 10)
According to yet another aspect of the invention.
A step of forming a piezoelectric film which is a polycrystalline film and is made of an alkali niobium oxide having a perovskite structure represented by the composition formula (K _1-x Na _x ) NbO ₃ (0 <x <1) on the substrate. When,
A step of forming an electrode film containing Cu on the piezoelectric film and
It has a step of performing a heat treatment on a laminate having the substrate, the piezoelectric film, and the electrode film.
By carrying out the step of performing the heat treatment, Cu in the electrode film is diffused into the piezoelectric film, and the piezoelectric film contains Cu and Cu present in the grain boundary of the crystal constituting the piezoelectric film. Provided is a method for producing a piezoelectric laminate having a film having more film than Cu present in the matrix of the crystal.

(Appendix 11)
According to yet another aspect of the invention.
The process of forming the lower electrode film on the substrate and
On the lower electrode film, a piezoelectric film which is a polycrystalline film and is made of an alkali niobium oxide having a perovskite structure represented by the composition formula (K _1-x Na _x ) NbO ₃ (0 <x <1) is produced. The process of filming and
The process of forming an upper electrode film on the piezoelectric film and
It has a step of performing a heat treatment on a laminate including the substrate, the lower electrode film, the piezoelectric film, and the upper electrode film.
Cu is contained in the lower electrode film in the step of forming the lower electrode film, or Cu is contained in the upper electrode film in the step of forming the upper electrode film.
By carrying out the step of performing the heat treatment, Cu in the lower electrode film or the upper electrode film is diffused into the piezoelectric film, and the piezoelectric film contains Cu and crystal grains constituting the piezoelectric film. Provided is a method for producing a piezoelectric laminate in which the amount of Cu present in the field is larger than that of Cu present in the matrix of the crystal.

(Appendix 12)
The method of Appendix 11, preferably
In the step of forming the lower electrode film, Cu is contained on the side close to the upper surface of the lower electrode film, and in the step of forming the upper electrode film, Cu is contained on the side close to the lower surface of the upper electrode film. To include.

1 Substrate 3 Piezoelectric film 10 Piezoelectric laminate

Claims (6)

With the board
With the electrode film
A polycrystalline film comprising a piezoelectric film composed of an alkaline niobium oxide having a perovskite structure represented by the composition formula (K _1-x Na _x ) NbO ₃ (0 <x <1).
The piezoelectric film contains Cu and contains Cu.
A piezoelectric laminate in which the amount of Cu present at the grain boundaries of the crystals constituting the piezoelectric film is larger than that of Cu present in the matrix phase of the crystals. When a positive or negative electric field of 300 kV / cm is applied to the electrode film provided on the piezoelectric film at a temperature of 200 ° C., the piezoelectric film is subjected to an electric field application start under at least one electric field application condition. The piezoelectric laminate according to claim 1, wherein it takes 7600 seconds or more for the flowing leakage current density to exceed 30 mA / cm ² . The piezoelectric laminate according to claim 1 or 2, wherein the piezoelectric film is composed of crystal grains having an average particle size of 100 nm or more. The piezoelectric laminate according to any one of claims 1 to 3, wherein the piezoelectric film contains Cu at a concentration of 0.2 at% or more and 2.0 at% or less. With the board
A piezoelectric film formed on the substrate, which is a polycrystalline film and is composed of an alkaline niobium oxide having a perovskite structure represented by the composition formula (K _1-x Na _x ) NbO ₃ (0 <x <1). ,
An electrode film formed on the piezoelectric film and
The piezoelectric film contains Cu and contains Cu.
A piezoelectric element in which the amount of Cu present at the grain boundaries of the crystals constituting the piezoelectric film is larger than that of Cu present in the matrix phase of the crystals. A step of forming a piezoelectric film which is a polycrystalline film and is made of an alkali niobium oxide having a perovskite structure represented by the composition formula (K _1-x Na _x ) NbO ₃ (0 <x <1) on the substrate. When,
A step of providing a layer containing Cu or a layer made of Cu on the piezoelectric film, and
The step of forming an electrode film on the layer containing Cu or the layer made of Cu, and
A step of heat-treating a laminate including the substrate, the piezoelectric film, a layer containing the Cu, or a layer made of the Cu, and the electrode film.
By carrying out the step of performing the heat treatment, Cu in the layer containing Cu or the layer composed of Cu is diffused into the piezoelectric film, and the piezoelectric film is made into a crystal containing Cu and constituting the piezoelectric film. A method for producing a piezoelectric laminate in which the amount of Cu present in the grain boundary of the crystal is larger than that of Cu present in the matrix of the crystal.

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