Piezoelectric substrates, piezoelectric elements, and piezoelectric element application devices

Abstract

To provide a piezoelectric substrate, a piezoelectric element, and a piezoelectric element application device that can reduce the generation of leakage current.SOLUTION: A piezoelectric substrate according to the present invention includes: a base body; an electrode deposited on the base body; and a piezoelectric layer deposited on the electrode and containing potassium, sodium, and niobium. A value of IR2 / IR1 obtained by dividing an integrated intensity IR2 at a peak 2 by an integrated intensity IR1 at a peak 1 when a surface of the piezoelectric layer is measured by Fourier transform infrared spectroscopy is less than 0.086. Here, the peak 1 has the strongest area intensity among peaks detected at wavelengths of 475-700 cm-1, and the peak 2 has the sum of area intensities of peaks detected at wavelengths of 1200-1645 cm-1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a piezoelectric substrate, a piezoelectric element, and a piezoelectric element application device. [Background technology]

[0002] A piezoelectric element generally comprises a substrate, a piezoelectric layer having electromechanical conversion properties, and two electrodes that sandwich the piezoelectric layer. In recent years, there has been a great deal of activity in developing devices that use such piezoelectric elements as a driving source (piezoelectric element application devices). Examples of piezoelectric element application devices include liquid jet heads, such as those used in inkjet recording heads; MEMS elements, such as piezoelectric MEMS elements; ultrasonic measuring devices, such as ultrasonic sensors; and piezoelectric actuator devices.

[0003] Lead zirconate titanate (PZT) is known as a material for the piezoelectric layer of piezoelectric elements (piezoelectric material). However, in recent years, from the perspective of reducing environmental impact, the development of lead-free piezoelectric materials with reduced lead content has been progressing. Furthermore, in recent years, there has been a strong demand for further miniaturization and improved performance of various electronic devices and electronic components, and consequently, there is a growing need for miniaturization and improved performance of piezoelectric elements.

[0004] As one example of a lead-free piezoelectric material, potassium sodium niobate (KNN; (K,Na)NbO3) has been proposed, as shown in Patent Document 1. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2013-225605 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Generally, when KNN-based materials are used as piezoelectric materials, a problem is known to be that leakage current is easily generated. In this regard, Patent Document 1 discloses that the generation of leakage current can be suppressed by including at least one of iron and manganese.

[0007] However, our own research has revealed that residual organic components within the piezoelectric layer increase the leakage current density. In other words, simply improving the crystal orientation by adding additives to the KNN-based piezoelectric layer may not be sufficient to reduce the leakage current density.

[0008] For these reasons, there is a need for piezoelectric layers in piezoelectric substrates and piezoelectric elements equipped with KNN-type piezoelectric layers that can sufficiently reduce leakage current.

[0009] Furthermore, this problem is not limited to piezoelectric elements used in piezoelectric actuators mounted on liquid ejection heads, such as those found in inkjet recording heads, but also exists in piezoelectric elements used in other piezoelectric element application devices. [Means for solving the problem]

[0010] To solve the above problems, according to a first aspect of the present invention, a piezoelectric substrate is provided comprising a substrate, an electrode formed on the substrate, and a piezoelectric layer formed on the electrode containing potassium, sodium, and niobium, wherein the value IR2 / IR1 obtained by dividing the integrated intensity IR2 of peak 2 by the integrated intensity IR1 of peak 1 when the surface of the piezoelectric layer is measured by Fourier transform infrared spectroscopy is less than 0.086. Here, peak 1 has a wavelength of 475 to 700 cm. -1 The area intensity of the strongest peak among the peaks detected is the area intensity of the peak 2, where the wavelength is 1200-1645 cm. -1 This is the sum of the area intensities of the peaks detected.

[0011] Further, according to a second aspect of the present invention, there is provided a piezoelectric element comprising a substrate, a first electrode formed on the substrate, a piezoelectric layer formed on the first electrode and containing potassium, sodium, and niobium, and a second electrode formed on the piezoelectric layer, wherein a value IR2 / IR1 obtained by dividing an integrated intensity IR2 of peak 2 by an integrated intensity IR1 of peak 1 when a surface of the piezoelectric layer is measured by Fourier transform infrared spectroscopy is less than 0.086.

[0012] Further, according to a third aspect of the present invention, there is provided a piezoelectric element application device including the piezoelectric element according to the above aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] [Figure 1] It is a cross-sectional view schematically showing the piezoelectric substrate of the present embodiment. [Figure 2] It is a cross-sectional view schematically showing the piezoelectric element of the present embodiment. [Figure 3] It is a perspective view showing a schematic configuration of the recording apparatus of the present embodiment. [Figure 4] It is an exploded perspective view of the recording head of the recording apparatus of FIG. 1. [Figure 5] It is a plan view of the recording head of the recording apparatus of FIG. 1. [Figure 6] It is a cross-sectional view of the recording head of the recording apparatus of FIG. 1. [Figure 7] It is a graph showing measurement results of Fourier transform infrared spectroscopy of the present example. DESCRIPTION OF EMBODIMENTS

[0014] Embodiments of the present invention will be described below with reference to the drawings. The following description illustrates one aspect of the present invention and can be modified as appropriate without departing from the spirit of the invention. In each drawing, components with the same reference numerals indicate the same member, and their descriptions are omitted as appropriate. The numbers following the letters that constitute the reference numerals are used to distinguish elements that are referenced by reference numerals containing the same letters and have similar configurations. When there is no need to distinguish between elements indicated by reference numerals containing the same letters, these elements are each referenced by reference numerals containing only letters.

[0015] In each drawing, X, Y, and Z represent three mutually orthogonal spatial axes. In this specification, the directions along these axes are referred to as the first direction X (X direction), the second direction Y (Y direction), and the third direction Z (Z direction), respectively, with the direction indicated by the arrow in each figure being the positive (+) direction and the opposite direction being the negative (-) direction. The X and Y directions represent the in-plane directions of plates, layers, and films, while the Z direction represents the thickness direction or lamination direction of plates, layers, and films.

[0016] Furthermore, the components shown in each drawing, namely the shape and size of each part, the thickness of plates, layers and films, their relative positional relationships, and repeating units, may be exaggerated in order to explain the present invention. Moreover, the term "above" in this specification does not limit the positional relationship of the components to "directly above". For example, the expressions "first electrode on the substrate" and "piezoelectric layer on the first electrode" described later do not exclude cases where other components are included between the substrate and the first electrode, or between the first electrode and the piezoelectric layer.

[0017] (Piezoelectric substrate) First, the configuration of the piezoelectric substrate 400 in this embodiment will be described with reference to the drawings. Figure 1 is a schematic cross-sectional view showing the piezoelectric substrate 400.

[0018] As shown in the figure, the piezoelectric substrate 400 includes a base body 2, an electrode 60A, and a piezoelectric layer 70. The piezoelectric substrate 400 is provided above the base body 2. In the illustrated example, the piezoelectric substrate 400 is provided on the base body 2. Note that the thicknesses of each element shown in the figure are examples only and can be changed without altering the essence of the present invention.

[0019] The substrate 2 is, for example, a flat plate made of a semiconductor, an insulator, or the like. The substrate 2 may be a single layer or a structure in which multiple layers are stacked. The internal structure of the substrate 2 is not limited as long as the top surface is planar, and it may have a structure in which spaces are formed inside.

[0020] The substrate 2 has a diaphragm 50 that can be deformed by the operation of, for example, the piezoelectric layer 70. In the illustrated example, the diaphragm 50 has a silicon oxide layer 51 and an oxide layer 52 provided on the silicon oxide layer 51. In the illustrated example, the substrate 2 has a silicon substrate 10, and the diaphragm 50 is provided on the silicon substrate 10.

[0021] The silicon oxide layer 51 is a layer containing silicon and oxygen, for example, a silica (SiO2) layer. The silicon oxide layer 51 may function as an elastic film. The diaphragm 50 does not need to have the silicon oxide layer 51.

[0022] The oxide layer 52 is, for example, a zirconium oxide layer. When the oxide layer 52 is a zirconium oxide layer, the oxide layer 52 is a layer containing zirconium and oxygen, for example, a ZrO2 layer.

[0023] The electrode 60A is formed on the substrate 2 (diaphragm 50 in Figure 1). The shape of the electrode 60A is, for example, layered or thin film. The thickness (length in the Z-axis direction) of the electrode 60A is, for example, 10 nm to 200 nm.

[0024] Examples of materials for the electrode 60A include various metals such as nickel, iridium, and platinum, their conductive oxides (e.g., iridium oxide), a composite oxide of strontium and ruthenium (SrRuOx:SRO), and a composite oxide of lanthanum and nickel (LaNiOx:LNO). The electrode layer 60A may be a single layer structure of the materials exemplified above, or it may be a structure in which multiple materials are laminated.

[0025] The material for electrode 60A is preferably a precious metal such as platinum (Pt) or iridium (Ir), or an oxide thereof. Any conductive material is acceptable for the material of electrode 60A.

[0026] An adhesion layer (not shown) may be provided between the electrode 60A and the oxide layer 52. The adhesion layer may be, for example, titanium oxide (TiO X It consists of titanium (Ti), SiN, etc., and has the function of improving the adhesion between the piezoelectric layer 70 and the diaphragm 50. In addition, titanium oxide (TiO) is used as the adhesion layer. X When a silicon (PNC) layer, titanium (Ti) layer, or silicon nitride (SiN) layer is used, the adhesion layer also functions as a stopper to prevent potassium and sodium, which are constituent elements of the piezoelectric layer 70, from passing through the first electrode 60 and reaching the silicon substrate 10 when forming the piezoelectric layer 70. The adhesion layer can be omitted.

[0027] It is preferable to provide an orientation control layer (seed layer) 61 between the electrode 60A and the piezoelectric layer 70. The orientation control layer 61 functions as an orientation control layer that controls the orientation of the piezoelectric crystals constituting the piezoelectric layer 70. That is, by providing the orientation control layer 61 on the electrode 60A, the piezoelectric crystals constituting the piezoelectric layer 70 can be preferentially oriented to a predetermined plane orientation (for example, the (100) plane). By improving the crystal orientation of the piezoelectric layer, it is possible to efficiently utilize domain rotation and improve displacement characteristics. Examples of materials for the orientation control layer 61 include various metals such as titanium, nickel, iridium, and platinum, their oxides, and compounds containing bismuth, iron, titanium, and lead.

[0028] The piezoelectric layer 70 is formed on the electrode 60A, covering the electrode 60A. The piezoelectric layer 70 contains a composite oxide with a perovskite structure represented by the general formula ABO3 as its main component. In this embodiment, the piezoelectric layer 70 contains a piezoelectric material consisting of a KNN-based composite oxide represented by the following formula (1).

[0029] (K X Na 1-X )NbO3··· (1) (0.1 ≤ X ≤ 0.9)

[0030] The composite oxide represented by formula (1) above is a so-called KNN-type composite oxide. KNN-type composite oxides are lead-free piezoelectric materials with reduced lead (Pb) content, and therefore have excellent biocompatibility and low environmental impact. Moreover, KNN-type composite oxides have superior piezoelectric properties among lead-free piezoelectric materials, making them advantageous for improving various properties.

[0031] Here, the relationship between residual organic components contained in the piezoelectric layer 70 (hereinafter referred to as residual organic components) and leakage current will be explained below, along with new findings obtained by the inventors. In general, piezoelectric substrates (or piezoelectric elements described later) using a KNN system as represented by the above formula (1) as the piezoelectric material are known to be prone to leakage current. The inventors of this invention have diligently investigated the factors causing this leakage current and have found that residual organic components in the piezoelectric layer increase the leakage current density; in other words, there is a correlation between residual organic components and leakage current density. Furthermore, it has been found that simply improving the crystal orientation by adding additives to the piezoelectric layer, which is one of the conventional methods for reducing leakage current, may not be sufficient to reduce the leakage current density.

[0032] Therefore, in this embodiment, we focus on the residual organic components contained in the piezoelectric layer 70 and define the correlation of each peak when measured by Fourier transform infrared (FT-IR) spectroscopy. Specifically, the value IR2 / IR1 obtained by dividing the integrated intensity IR2 of peak 2 by the integrated intensity IR1 of peak 1 when the surface of the piezoelectric layer 70 is measured by FT-IR spectroscopy is less than 0.086. Here, peak 1 is defined as having a wavelength of 475 to 700 cm. -1 The area intensity of the strongest peak detected is peak 2, where the wavelength is 1200-1645 cm. -1 This is the sum of the area intensities of the peaks detected. More specifically, in the piezoelectric layer 70 of this embodiment, peak 1 corresponds to the peak related to niobium oxide (NbO), and by correlating the peaks related to residual organic components with respect to peak 1, it becomes possible to quantitatively evaluate the residual organic components contained in the piezoelectric layer 70. When IR2 / IR1 is less than 0.086, the amount of organic components remaining in the piezoelectric layer 70 can be reduced, leakage current can be sufficiently suppressed, and the amount of displacement can be increased because domain rotation can be applied. Preferably, IR2 / IR1 is 0.078 or less.

[0033] Since a smaller IR2 / IR1 ratio is preferable, there is no particular limit on the lower limit. However, the preferred manufacturing method for the piezoelectric substrate and the piezoelectric element described later in this embodiment is the liquid phase method, and in the case of the liquid phase method using a precursor solution, organic components tend to remain in the piezoelectric layer 70 more easily than in the gas phase method, so for example, IR2 / IR1 may be 0.05 or higher.

[0034] The piezoelectric layer 70 preferably contains lithium. Lithium has the effect of improving leakage characteristics. Therefore, in order to reduce leakage current more efficiently, it is effective to include lithium as a material constituting the piezoelectric layer 70. When lithium is included in the piezoelectric layer 70, the lithium content is preferably 20 moles or less. If the lithium content exceeds 20 moles, there is a risk that a different phase will be generated within the piezoelectric layer 70, and the crystal orientation and arrangement of the piezoelectric material may deteriorate. More preferably, the lithium content is 10 moles or less.

[0035] Furthermore, it is preferable that the piezoelectric layer 70 contains a first transition metal. Similar to lithium, the first transition metal has the effect of improving leakage characteristics. Therefore, to more efficiently reduce leakage current, it is effective to include a first transition metal as a material constituting the piezoelectric layer 70. Among the first transition metals, manganese and copper have a higher effect in improving leakage characteristics. Therefore, when the piezoelectric layer 70 contains a first transition metal, it is more preferable to include either manganese or copper. Both manganese and copper may be included in the piezoelectric layer 70.

[0036] Furthermore, if the content of the first transition metal in the piezoelectric layer 70 exceeds 5 moles, there is a risk of a different phase forming within the piezoelectric layer 70, which may reduce the crystal orientation and arrangement of the piezoelectric material. For this reason, when the piezoelectric layer 70 contains the first transition metal, it is preferable that the total content of the first transition metal be 5 moles or less.

[0037] Either lithium or the first transition metal mentioned above may be included in the piezoelectric layer 70, or both may be included. To further improve the leakage characteristics, it is preferable to include lithium and copper in the piezoelectric layer 70.

[0038] The average grain size of the KNN-based composite oxide constituting the piezoelectric layer 70 is preferably 1000 nm or less. If the average grain size of the KNN-based composite oxide is coarse, residual stress accumulated within the piezoelectric layer 70 will concentrate in the regions where coarse grains exist, potentially causing cracks to form within the piezoelectric layer 70. Therefore, the average grain size of the KNN-based composite oxide is preferably 1000 nm or less, and more preferably 300 nm or less. While a smaller average grain size is preferable from the viewpoint of suppressing crack formation, there is no particular lower limit; however, it is, for example, 20 nm or more.

[0039] The piezoelectric substrate 400 has been described above, but the piezoelectric material constituting the piezoelectric layer 70 can be any KNN-based composite oxide and is not limited to the composition represented by formula (1) above. For example, other metal elements (additives) may be included in the A site or B site of potassium sodium niobate. Examples of such additives include manganese (Mn), lithium (Li), barium (Ba), calcium (Ca), strontium (Sr), zirconium (Zr), titanium (Ti), bismuth (Bi), tantalum (Ta), antimony (Sb), iron (Fe), cobalt (Co), silver (Ag), magnesium (Mg), zinc (Zn), and copper (Cu). One or more of these additives may be included. By using additives, it is easier to improve various properties and diversify the composition and function. Even in the case of a composite oxide containing these other elements, it is preferable that it is configured to have an ABO3 type perovskite structure.

[0040] Furthermore, in this specification, "a perovskite-type composite oxide containing K, Na, and Nb" refers to "a composite oxide with an ABO3-type perovskite structure containing K, Na, and Nb," and is not limited to composite oxides with an ABO3-type perovskite structure containing K, Na, and Nb. That is, in this specification, "a perovskite-type composite oxide containing K, Na, and Nb" includes piezoelectric materials represented as a mixed crystal containing a composite oxide with an ABO3-type perovskite structure containing K, Na, and Nb (for example, the KNN-based composite oxide exemplified above) and other composite oxides having an ABO3-type perovskite structure.

[0041] Other composite oxides are not limited to the scope of this embodiment, but preferably lead-free piezoelectric materials that do not contain lead (Pb). These materials result in a piezoelectric substrate 400 that is highly biocompatible and has a low environmental impact.

[0042] According to the piezoelectric substrate 400 of this embodiment described above, residual organic components in the piezoelectric layer 70 can be reduced, and leakage current can be reduced.

[0043] (Piezoelectric element) Next, the configuration of the piezoelectric element 300 of this embodiment will be described with reference to the drawings. Figure 2 is a schematic cross-sectional view of the piezoelectric element 300, and is an enlarged cross-sectional view of line BB' in Figure 6. Note that components with the same reference numerals in Figures 1 and 2 are the same components, and their descriptions may be omitted as appropriate.

[0044] As shown in the figure, the piezoelectric element 300 includes a substrate 2, a first electrode 60, a piezoelectric layer 70, and a second electrode 80. The piezoelectric element 300 is provided above the substrate 2. In the illustrated example, the piezoelectric element 300 is provided on the substrate 2. Note that the thicknesses of each element shown in the figure are examples only and can be changed without altering the essence of the present invention.

[0045] The configuration, materials, etc., of the base body 2 and the diaphragm 50 may be the same as those of the piezoelectric substrate 400 (see Figure 1) according to this embodiment. Therefore, a detailed explanation is omitted.

[0046] The first electrode 60 is formed on the substrate 2 (diaphragm 50 in Figure 2). The shape of the first electrode 60 is, for example, layered or thin film. The thickness (length in the Z-axis direction) of the first electrode 60 is, for example, 10 nm to 200 nm. The planar shape (shape viewed from the Z-axis direction) of the first electrode 60 is not particularly limited as long as it is a shape that allows the piezoelectric layer 70 to be placed between the two when the second electrode 80 is placed opposite it.

[0047] Examples of materials for the first electrode 60 include various metals such as nickel, iridium, and platinum, their conductive oxides (e.g., iridium oxide), a composite oxide of strontium and ruthenium (SrRuOx:SRO), and a composite oxide of lanthanum and nickel (LaNiOx:LNO). The first electrode layer 60 may be a single layer of the materials exemplified above, or it may be a structure in which multiple materials are laminated.

[0048] The first electrode 60, together with the second electrode 80, can form one of the electrodes (for example, a lower electrode formed below the piezoelectric layer 70) for applying a voltage to the piezoelectric layer 70.

[0049] The second electrode 80 is formed on the piezoelectric layer 70. The second electrode 80 is disposed to face the first electrode 60 with the piezoelectric layer 70 interposed therebetween. The shape of the second electrode 80 is, for example, a layered or thin-film shape. The thickness of the second electrode 80 is, for example, 10 nm or more and 200 nm or less. The planar shape of the second electrode 80 is not particularly limited as long as it allows the piezoelectric layer 70 to be disposed between the second electrode 80 and the first electrode 60 when the second electrode 80 is disposed facing the first electrode 60.

[0050] As the material of the second electrode 80, for example, those listed above as the materials of the first electrode 60 can be applied. However, in order for the ratio of the Young's modulus of the piezoelectric layer 70 to the Young's modulus of the second electrode 80 to satisfy the above range, it is preferable to use platinum (Pt) or iridium (Ir) as the material of the second electrode 80.

[0051] One of the functions of the second electrode 80 is that, paired with the first electrode 60, it serves as the other electrode for applying a voltage to the piezoelectric layer 70 (for example, an upper electrode formed above the piezoelectric layer 70).

[0052] Preferable materials for the first electrode 60 and the second electrode 80 are noble metals such as platinum (Pt) and iridium (Ir), and oxides thereof. The material of the first electrode 60 and the material of the second electrode 80 only need to be conductive materials. The material of the first electrode 60 and the material of the second electrode 80 may be the same or different.

[0053] An adhesion layer (not shown) may be provided between the first electrode 60 and the oxide layer 52. The adhesion layer is formed of, for example, titanium oxide (TiO X ), titanium (Ti), SiN, or the like, and has a function of improving the adhesion between the piezoelectric layer 70 and the vibration plate 50. Further, as the adhesion layer, titanium oxide (TiO XWhen a silicon (PNC) layer, titanium (Ti) layer, or silicon nitride (SiN) layer is used, the adhesion layer also functions as a stopper to prevent potassium and sodium, which are constituent elements of the piezoelectric layer 70, from passing through the first electrode 60 and reaching the silicon substrate 10 when forming the piezoelectric layer 70. The adhesion layer can be omitted.

[0054] It is preferable to provide an orientation control layer (seed layer) 61 between the first electrode 60 and the piezoelectric layer 70. The orientation control layer 61 functions as an orientation control layer that controls the orientation of the piezoelectric crystals constituting the piezoelectric layer 70. That is, by providing the orientation control layer 61 on the first electrode 60, the piezoelectric crystals constituting the piezoelectric layer 70 can be preferentially oriented to a predetermined plane orientation (for example, the (100) plane). By improving the crystal orientation of the piezoelectric layer, it is possible to efficiently utilize domain rotation and improve displacement characteristics. Examples of materials for the orientation control layer 61 include various metals such as titanium, nickel, iridium, and platinum, their oxides, and compounds containing bismuth, iron, titanium, and lead.

[0055] The piezoelectric layer 70 is formed on the first electrode 60 so as to cover the first electrode 60. The piezoelectric layer 70 contains a composite oxide with a perovskite structure represented by the general formula ABO3 as its main component. In this embodiment, the piezoelectric layer 70 contains a piezoelectric material consisting of a KNN-based composite oxide represented by the above formula (1).

[0056] The composition, materials, IR2 / IR1, lithium, and first transition metal specifications of the piezoelectric layer 70 can be the same as those of the piezoelectric substrate 400 according to this embodiment.

[0057] According to the piezoelectric element 300 of this embodiment described above, residual organic components in the piezoelectric layer 70 can be reduced, and leakage current can be reduced.

[0058] (Manufacturing method for piezoelectric elements) Next, an example of a method for manufacturing the piezoelectric element 300 will be described. In the following explanation, the case in which the piezoelectric layer 70 is manufactured by a chemical solution method (also called a wet method or liquid phase method) will be used as an example.

[0059] First, a silicon substrate 10 is prepared, and a silicon oxide layer 51 made of silicon dioxide (SiO2) is formed on its surface by thermal oxidation of the silicon substrate 10.

[0060] Next, an oxide layer 52 made of zirconium oxide (ZrO2) is deposited on the silicon oxide layer 51 by atomic layer deposition (ALD). The deposition temperature is, for example, 450 to 850°C. The oxide layer 52 can also be formed by methods other than ALD, such as sputtering or vapor deposition. For example, a zirconium film is first formed on the silicon oxide layer 51 by sputtering or vapor deposition, and then the oxide layer 52 made of zirconium oxide (ZrO2) is obtained by thermal oxidation. In this way, a diaphragm 50 made of the silicon oxide layer 51 and the oxide layer 52 is formed on the silicon substrate 10.

[0061] Next, an adhesion layer made of metallic titanium (Ti) is formed on the oxide layer 52. The adhesion layer can be formed by sputtering or the like. Then, a first electrode 60 made of platinum (Pt) is formed on the adhesion layer. The first electrode 60 can be appropriately selected depending on the electrode material, and can be formed by vapor phase deposition such as sputtering, vacuum deposition (PVD), or laser ablation, or liquid phase deposition such as spin coating.

[0062] Next, an orientation control layer (seed layer) 61 is formed on the first electrode 60. The orientation control layer 61 can be formed, for example, by a chemical solution method (wet method) in which a solution containing a metal complex (precursor solution) is applied, followed by drying and degreasing, and then firing at a high temperature to obtain a metal oxide. Examples of materials for the orientation control layer 61 include various metals such as bismuth, iron, titanium, lead, nickel, iridium, and platinum, and their oxides.

[0063] Next, a resist of a predetermined shape is formed on the first electrode 60 as a mask, and the adhesion layer, the first electrode 60, and the orientation control layer 61 are patterned simultaneously. The patterning of the adhesion layer, the first electrode 60, and the orientation control layer 61 can be performed, for example, by dry etching such as reactive ion etching (RIE) or ion milling, or by wet etching using an etching solution. The shape of the patterned adhesion layer, the first electrode 60, and the orientation control layer 61 is not particularly limited.

[0064] Next, multiple piezoelectric films are formed on the first electrode 60. The piezoelectric layer 70 is composed of these multiple piezoelectric films. The piezoelectric layer 70 can be formed, for example, by a chemical solution method (wet method) in which a solution containing a metal complex (precursor solution) is applied and dried, and then fired at a high temperature to obtain a metal oxide. In addition, it can also be formed by laser ablation, sputtering, pulsed laser deposition (PLD), chemical vapor deposition (CVD), aerosol deposition, etc.

[0065] For example, a piezoelectric layer 70 formed by a wet method (liquid phase method) has multiple piezoelectric layers formed by a series of steps including a step of applying a precursor solution to form a precursor film (coating step), a step of drying the precursor film (drying step), a step of heating and degreasing the dried precursor film (degreasing step), and a step of firing the degreasing precursor film (firing step). That is, the piezoelectric layer 70 is formed by repeating the series of steps from the coating step to the firing step multiple times. In addition, in the series of steps described above, the firing step may be performed after repeating the steps from the coating step to the degreasing step multiple times.

[0066] The specific procedure for forming the piezoelectric layer 70 using a wet method (liquid phase method) is as follows, for example. First, a precursor solution containing a predetermined metal complex is prepared. The precursor solution is obtained by dissolving or dispersing a metal complex, which can form a composite oxide containing K, Na, and Nb by calcination, in an organic solvent. At this time, a metal complex containing additives such as Mn, Li, and Cu may be further mixed in. By mixing a metal complex containing Mn, Li, or Cu into the precursor solution, the insulating properties of the resulting piezoelectric layer 70 can be further enhanced.

[0067] Examples of metal complexes containing potassium (K) include potassium 2-ethylhexanoate and potassium acetate. Examples of metal complexes containing sodium (Na) include sodium 2-ethylhexanoate and sodium acetate. Examples of metal complexes containing niobium (Nb) include niobium 2-ethylhexanoate and pentaethoxyniobium. When manganese (Mn) is added as an additive, examples of metal complexes containing Mn include manganese 2-ethylhexanoate. When lithium (Li) is added as an additive, examples of metal complexes containing Li include lithium 2-ethylhexanoate. When copper (Cu) is added as an additive, examples of metal complexes containing Cu include copper 2-ethylhexanoate. In this case, two or more metal complexes may be used in combination. For example, potassium 2-ethylhexanoate and potassium acetate may be used in combination as metal complexes containing potassium (K). Examples of solvents include 2-n-butoxyethanol, n-octane, or mixed solvents thereof. The precursor solution may contain additives that stabilize the dispersion of the metal complexes containing K, Na, and Nb. Examples of such additives include 2-ethylhexanoic acid.

[0068] Then, the above-mentioned precursor solution is applied to the silicon substrate 10 on which the silicon oxide layer 51, the oxide layer 52, and the first electrode 60 are formed, to form a precursor film (coating step). Next, this precursor film is heated to a predetermined temperature, for example, around 130°C to 250°C, and dried for a certain period of time (drying step).

[0069] Next, the dried precursor film is heated to a predetermined temperature, for example, 250°C to 450°C, and held at this temperature for a certain period of time to degrease it and remove organic components from the precursor film (degreasing step).

[0070] Next, the degreased precursor film is heated to 500°C to 800°C and held at this temperature for 1 to 10 minutes to perform firing (firing process). If the holding temperature is too high, the crystal orientation may be reduced. On the other hand, if the holding temperature is too low, the firing may be insufficient. Therefore, in this embodiment, the holding temperature is preferably 500 to 800°C. In addition, the average heating rate in the firing process is preferably 60°C / second or less. If the average heating rate is too fast, the time until crystallization will be shortened, and organic components will be more likely to remain in the precursor film. Therefore, the average heating rate is preferably 60°C / second or less.

[0071] Examples of heating devices used in the drying, degreasing, and firing processes include RTA (Rapid Thermal Annealing) devices that heat by irradiation with infrared lamps, and hot plates. The above process is repeated multiple times to form a piezoelectric layer 70 consisting of multiple piezoelectric films. In addition, in the series of processes from the coating process to the firing process, the firing process may be performed after repeating the coating process to the degreasing process multiple times.

[0072] Furthermore, before and after forming the second electrode 80 on the piezoelectric layer 70, a reheating treatment (post-annealing) may be performed in a temperature range of 600°C to 800°C as needed. By performing post-annealing in this manner, a good interface can be formed between the piezoelectric layer 70 and the first electrode, and between the piezoelectric layer 70 and the second electrode 80. In addition, the crystallinity of the piezoelectric layer 70 can be improved, and the insulating properties of the piezoelectric layer 70 can be further enhanced.

[0073] After the firing process, the piezoelectric layer 70, which consists of multiple piezoelectric films, is patterned into a desired shape. Patterning can be performed by dry etching such as reactive ion etching or ion milling, or by wet etching using an etching solution.

[0074] Subsequently, a second electrode 80 is formed on the piezoelectric layer 70. The second electrode 80 can be formed in the same manner as the first electrode 60.

[0075] Through the above process, a piezoelectric element 300 comprising a first electrode 60, a piezoelectric layer 70, and a second electrode 80 is manufactured.

[0076] (Piezoelectric element application devices) Next, an inkjet recording device, which is an example of a piezoelectric element application device according to this embodiment and is a liquid jetting device equipped with a recording head, will be described with reference to the drawings. Figure 3 is a perspective view showing the schematic configuration of the inkjet recording device. As shown in Figure 3, in the inkjet recording device (recording device) I, an inkjet recording head unit (head unit) II is detachably mounted on cartridges 2A and 2B. Cartridges 2A and 2B constitute the ink supply means. The head unit II has a plurality of inkjet recording heads (recording heads) 1 (see Figure 4, etc.) and is mounted on a carriage 3. The carriage 3 is mounted on a carriage shaft 5 attached to the main body 4 of the device, so as to be movable in the axial direction. These head unit II and carriage 3 are configured to eject, for example, a black ink composition and a color ink composition, respectively.

[0077] The driving force of the drive motor 6 is transmitted to the carriage 3 via a plurality of gears (not shown) and a timing belt 7, causing the carriage 3, on which the head unit II is mounted, to move along the carriage axis 5. Meanwhile, the main body of the device 4 is provided with transport rollers 8 as a transport means, and the recording sheet S, which is a recording medium (media) such as paper, is transported by the transport rollers 8. Note that the transport means for transporting the recording sheet S is not limited to transport rollers, but may also be a belt or drum.

[0078] A piezoelectric element 300 (see Figure 2) is used as a piezoelectric actuator device in the recording head (head chip) 1. By using the piezoelectric element 300, it is possible to avoid a decrease in various characteristics of the recording device I (piezoelectric characteristics, durability, ink ejection characteristics, etc.). In this embodiment, the piezoelectric element application device can particularly improve piezoelectric characteristics (especially leakage characteristics) by applying the piezoelectric element 300.

[0079] Next, a recording head (head chip) 1, which is an example of a head chip mounted on a liquid injection device, will be described with reference to the drawings. Figure 4 is an exploded perspective view showing the schematic configuration of an inkjet recording head. Figure 5 is a plan view showing the schematic configuration of an inkjet recording head. Figure 6 is a cross-sectional view taken along line AA' in Figure 4. Note that Figures 4 to 6 each show only a part of the configuration of the recording head 1 and have been omitted as appropriate.

[0080] As shown in the figure, the recording head (head chip) 1 comprises a nozzle plate 20 having a nozzle opening 21 for ejecting droplets, a pressure generating chamber 12 communicating with the nozzle opening 21, a partition wall 11 provided on the nozzle plate 20 and forming the pressure generating chamber 12, a flow channel forming substrate (silicon substrate) 10 forming a part of the wall surface of the pressure generating chamber 12, a piezoelectric element 300 provided on the silicon substrate 10, and a lead electrode (voltage application part) 90 for applying a voltage to the piezoelectric element 300.

[0081] Multiple partition walls 11 are formed on the silicon substrate 10. Multiple pressure generating chambers 12 are partitioned by the partition walls 11. That is, the pressure generating chambers 12 are arranged in parallel on the substrate 10 along the X direction (the direction in which nozzle openings 21 for ejecting ink of the same color are arranged side by side). This configuration forms the movable part of the piezoelectric element 300. For example, a silicon single crystal substrate can be used as the silicon substrate 10.

[0082] On one end (+Y direction side) of the pressure generating chamber 12 of the silicon substrate 10, an ink supply passage 13 and a connecting passage 14 are formed. The ink supply passage 13 is configured to reduce the area of ​​the opening on one end of the pressure generating chamber 12. The connecting passage 14 has approximately the same width as the pressure generating chamber 12 in the +X direction. A connecting section 15 is formed on the outside (+Y direction side) of the connecting passage 14. The connecting section 15 constitutes part of the manifold 100. The manifold 100 is a common ink chamber for each pressure generating chamber 12. In this way, a liquid flow path consisting of the pressure generating chamber 12, the ink supply passage 13, the connecting passage 14, and the connecting section 15 is formed in the silicon substrate 10.

[0083] A nozzle plate 20, for example, made of SUS (stainless steel), is bonded to one side (the side in the -Z direction) of the silicon substrate 10. Nozzle openings 21 are arranged in parallel on the nozzle plate 20 along the +X direction. The nozzle openings 21 communicate with each pressure generating chamber 12. The nozzle plate 20 can be bonded to the silicon substrate 10 by adhesive, heat-sealing film, or the like.

[0084] A diaphragm 50 is formed on the other side (the side in the +Z direction) of the silicon substrate 10. The diaphragm 50 is composed of, for example, a silicon oxide layer 51 formed on the silicon substrate 10 and an oxide layer 52 formed on the silicon oxide layer 51. The silicon oxide layer 51 is made of, for example, silicon dioxide (SiO2), and the oxide layer 52 is made of, for example, zirconium oxide (ZrO2). The silicon oxide layer 51 does not have to be a separate component from the silicon substrate 10. A part of the silicon substrate 10 may be thinned and used as the silicon oxide layer 51. The insulating film 52 functions as a stopper to prevent potassium and sodium, which are constituent elements of the piezoelectric layer 70, from passing through the first electrode 60 and reaching the substrate 10 when forming the piezoelectric layer 70, which will be described later.

[0085] A first electrode 60 is provided for each pressure generating chamber 12. In other words, the first electrode 60 is configured as an independent individual electrode for each pressure generating chamber 12. The first electrode 60 is formed to be smaller than the width of the pressure generating chamber 12 in the ±X direction. Also, the first electrode 60 is formed to be wider than the width of the pressure generating chamber 12 in the ±Y direction. That is, in the ±Y direction, both ends of the first electrode 60 are formed to extend beyond the region on the diaphragm 50 that faces the pressure generating chamber 12. A lead electrode (voltage application part) 90 for applying voltage to the piezoelectric element 300 is connected to one end of the first electrode 60 (opposite the communication passage 14).

[0086] The piezoelectric layer 70 is provided between the first electrode 60 and the second electrode 80. The piezoelectric layer 70 is a thin film piezoelectric material. The piezoelectric layer 70 is formed with a width wider than the width of the first electrode 60 in the ±X direction. Also, the piezoelectric layer 70 is formed with a width wider than the ±Y length of the pressure generation chamber 12 in the ±Y direction. The end of the piezoelectric layer 70 on the ink supply path 13 side (+Y direction side) extends outward beyond the +Y direction end of the first electrode 60. In other words, the +Y direction end of the first electrode 60 is covered by the piezoelectric layer 70. On the other hand, the end of the piezoelectric layer 70 on the lead electrode 90 side (-Y direction side) is inward (+Y direction side) beyond the -Y direction end of the first electrode 60. In other words, the -Y direction end of the first electrode 60 is not covered by the piezoelectric layer 70.

[0087] The second electrode 80 is continuously provided on the piezoelectric layer 70 and the diaphragm 50 in the +X direction. In other words, the second electrode 80 is configured as a common electrode common to multiple piezoelectric layers 70. In this embodiment, the first electrode 60 is configured as an individual electrode independently provided corresponding to the pressure generating chamber 12, and the second electrode 80 is configured as a common electrode continuously provided in the direction in which the pressure generating chambers 12 are arranged side by side. However, the first electrode 60 may be configured as a common electrode and the second electrode 80 as an individual electrode.

[0088] In the piezoelectric element 300 of this embodiment, the diaphragm 50 and the first electrode 60 are displaced by the displacement of the piezoelectric layer 70, which has electromechanical conversion characteristics. That is, the diaphragm 50 and the first electrode 60 substantially function as a diaphragm. However, in reality, the second electrode 80 is also displaced by the displacement of the piezoelectric layer 70, so the region in which the diaphragm 50, the first electrode 60, the piezoelectric layer 70, and the second electrode 80 are sequentially stacked functions as the movable part (also called the vibrating part) of the piezoelectric element 300.

[0089] A protective substrate 30 is bonded to the substrate 10 (diaphragm 50) on which the piezoelectric element 300 is formed, using an adhesive 35. The protective substrate 30 has a manifold portion 32. The manifold portion 32 constitutes at least a part of the manifold 100. In this embodiment, the manifold portion 32 penetrates the protective substrate 30 in the thickness direction (Z direction) and is further formed over the width direction (+X direction) of the pressure generating chamber 12. The manifold portion 32 is in communication with the communication portion 15 of the substrate 10. With these configurations, a manifold 100 is formed which serves as a common ink chamber for each pressure generating chamber 12.

[0090] A piezoelectric element holding portion 31 is formed in the region containing the piezoelectric element 300 on the protective substrate 30. The piezoelectric element holding portion 31 has a space that does not hinder the movement of the piezoelectric element 300. This space may or may not be sealed. The protective substrate 30 is provided with a through hole 33 that penetrates the protective substrate 30 in the thickness direction (Z direction). The end of the lead electrode 90 is exposed inside the through hole 33.

[0091] Examples of materials for the protective substrate 30 include Si, SOI, glass, ceramic materials, metals, and resins, but it is more preferable that it be made of a material with a thermal expansion coefficient approximately the same as that of the substrate 10.

[0092] A drive circuit 120, which functions as a signal processing unit, is fixed to the protective substrate 30. The drive circuit 120 can be, for example, a circuit board or a semiconductor integrated circuit (IC). The drive circuit 120 and the lead electrodes 90 are electrically connected via connecting wiring 121, which consists of conductive wires such as bonding wires inserted through through holes 33. The drive circuit 120 can be electrically connected to a printer controller 200 (see Figure 2). Such a drive circuit 120 functions as a control means for a piezoelectric actuator device (piezoelectric element 300).

[0093] Furthermore, a compliance substrate 40, consisting of a sealing film 41 and a fixing plate 42, is bonded to the protective substrate 30. The sealing film 41 is made of a material with low rigidity, and the fixing plate 42 can be made of a hard material such as metal. The region of the fixing plate 42 facing the manifold 100 is an opening 43 that is completely removed in the thickness direction (Z direction). One side of the manifold 100 (the side in the +Z direction) is sealed only with the flexible sealing film 41.

[0094] Such a recording head 1 ejects ink droplets in the following manner. First, ink is drawn in through an ink inlet connected to an external ink supply means (not shown), filling the manifold 100 and the nozzle opening 21 with ink. Then, according to the recording signal from the drive circuit 120, a voltage is applied between the first electrode 60 and the second electrode 80 corresponding to the pressure generating chamber 12, causing the piezoelectric element 300 to bend and deform. As a result, the pressure in each pressure generating chamber 12 increases, and ink droplets are ejected from the nozzle opening 21.

[0095] In the above embodiment, an inkjet recording head was described as an example of a liquid ejection head, but the present invention is applicable to liquid ejection heads in general, and can also be applied to liquid ejection heads that eject liquids other than ink. Other examples of liquid ejection heads include various recording heads used in image recording devices such as printers, colorant ejection heads used in the manufacture of color filters for liquid crystal displays, electrode material ejection heads used in electrode formation for organic EL displays and FEDs (field emission displays), and bio-organic material ejection heads used in biochip manufacturing.

[0096] Furthermore, the present invention is not limited to piezoelectric elements mounted on liquid injection heads, but can also be applied to piezoelectric elements mounted on other piezoelectric element application devices. Examples of piezoelectric element application devices include ultrasonic devices, motors, pressure sensors, pyroelectric elements, and ferroelectric elements. In addition, complete systems utilizing these piezoelectric element application devices, such as liquid injection devices using the above-mentioned liquid injection head, ultrasonic sensors using the above-mentioned ultrasonic devices, robots using the above-mentioned motors as a driving source, IR sensors using the above-mentioned pyroelectric elements, and ferroelectric memories using ferroelectric elements, are also included in the category of piezoelectric element application devices.

[0097] In particular, the piezoelectric element of the present invention is suitable as a piezoelectric element mounted in a sensor. Examples of sensors include gyro sensors, ultrasonic sensors, pressure sensors, and speed / acceleration sensors. When the piezoelectric element of the present invention is applied to a sensor, for example, a sensor can be created by providing a voltage detection unit that detects the voltage output from the piezoelectric element 300 between the first electrode 60 and the second electrode 80. In such a sensor, when the piezoelectric element 300 is deformed due to some external change (change in physical quantity), a voltage is generated in conjunction with the deformation. Various physical quantities can be detected by detecting this voltage with the voltage detection unit. [Examples]

[0098] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to these examples.

[0099] (Example 1) First, the surface of a silicon substrate (6-inch; (110) orientation) was thermally oxidized to form a silicon oxide layer (1460 nm) made of silicon dioxide on the substrate. Furthermore, a ZrO2 film was deposited on the silicon oxide layer using the ALD method to form an oxide layer (400 nm) made of zirconium oxide. The deposition temperature was 850°C. In this way, a diaphragm consisting of the silicon oxide layer and the oxide layer was formed on the silicon substrate.

[0100] Next, an adhesion layer (20 nm) made of titanium (Ti) was formed on the diaphragm by sputtering, and then a first electrode containing platinum (Pt) and iridium was formed on the adhesion layer by sputtering. The first electrode is constructed by sequentially stacking a layer containing platinum (Pt) (80 nm) and a layer containing iridium (Ir) (5 nm) on the adhesion layer.

[0101] Next, an orientation control layer (seed layer) was formed on the first electrode using the following procedure. First, a solution of bismuth, iron, titanium, and lead propionic acid was prepared using Bi:Pb:Fe:Ti in a ratio of Bi:Pb:Fe:Ti = 110:10:50:50. This solution was applied to the first electrode by spin coating. Subsequently, the applied solution was dried and degreased using a hot plate, and then heat-treated using RTA (Rapid Thermal Annealing) to form an orientation-controlled layer. The deposition conditions for the orientation-controlled layer are shown in Table 1.

[0102] [Table 1]

[0103] Next, a piezoelectric layer was formed on the diaphragm using the following procedure. First, using a precursor solution consisting of potassium 2-ethylhexanoate, sodium 2-ethylhexanoate, lithium 2-ethylhexanoate, niobium 2-ethylhexanoate, manganese 2-ethylhexanoate, and copper 2-ethylhexanoate, K 0.5136 Na 0.4934 Li 0.053 Nb 0.99 Mn 0.005 Cu 0.005 O x The mixture was prepared in this manner and applied to the orientation control layer by spin coating to form a precursor film (coating step). The precursor film was then dried (drying step), followed by degreasing (degreasing step). Next, the degreased precursor film was subjected to heat treatment using RTA (Rapid Thermal Annealing) to form a piezoelectric film (firing step). The upper limits for each of the coating, drying, degreasing, and firing steps are shown in Table 1.

[0104] This process, from coating to firing, was repeated five times to produce a piezoelectric layer consisting of five piezoelectric films with a total thickness of 400 nm.

[0105] A second electrode (50 nm) made of platinum (Pt), similar to the first electrode, was formed on the obtained piezoelectric layer by sputtering, thereby obtaining a piezoelectric element.

[0106] (Example 2) The composition of the piezoelectric layer is K 0.5136 Na 0.4934 Li 0.053 Nb 0.99 Cu 0.01 O x Except for the above, the procedure was the same as in Example 1.

[0107] (Comparative Example 1) The composition of the piezoelectric layer is K 0.5136 Na 0.4934 Li 0.053 Nb 0.99 Mn 0.005 O x Except for the above, the procedure was the same as in Example 1.

[0108] (Comparative Example 2) The composition of the piezoelectric layer is K 0.5 Na 0.5 Nb 0.995 Mn 0.005 O x , and the procedure was the same as in Example 1 except that the manufacturing conditions were as shown in Table 2.

[0109]

Table 2

[0110] For each of the above examples and comparative examples, FT-IR spectroscopic analysis was performed on the obtained piezoelectric layers.

[0111] <FT-IR Spectroscopic Analysis> Measurement was performed by the ATR method using an FT / IR-4700 (detector: TGS) manufactured by JASCO Corporation. A diamond was used as the ATR crystal, and the ATR crystal was pressed into close contact with the sample. The measurement range was 4000 to 400 cm -1 , the resolution was 4 cm -1 , and the number of integrations was 32. FIG. 7 shows the FT-IR spectroscopic analysis results of Examples 1 to 2 and Comparative Examples 1 to 2. In FIG. 7, the analysis results of Examples 1 to 2 and Comparative Examples 1 to 2 are arranged along the vertical axis direction for easy comparison.

[0112] <Leakage Current Measurement> The leakage current of the obtained piezoelectric element was measured using a microammeter (model 4140B, manufactured by Hewlett-Packard Company). The measurement conditions were as follows: the delay time was set to 10 seconds, measurement was performed with the first electrode side as the drive side, and the leakage current at an electric field strength of 500 kV / cm was measured.

[0113] (Test Results) Table 3 shows the leakage current measurement results at an electric field strength of 500 kV / cm for Examples 1, 2 and Comparative Example 1. For the comparative example, when the surface of the piezoelectric layer was observed with a scanning electron microscope (SEM) after forming the piezoelectric layer, generation of cracks was confirmed, so measurement of the leakage current density was not performed.

[0114] The measurement results are shown in Tables 3 and 4. In Table 3, "BE" refers to the first electrode and "TE" refers to the second electrode. Also, in Table 3, "E-0x" in "Leakage Current" means "×10 -x This indicates that "2.71E-07" is "2.71×10 -7 This means that it is ".

[0115] [Table 3]

[0116] [Table 4]

[0117] (Test results) As shown in Table 3 and Figure 7, it can be seen that in Examples 1 and 2, residual organic components in the piezoelectric layer can be reduced, and the amount of leakage current can be significantly suppressed. [Explanation of Symbols]

[0118] I... Inkjet recording device (liquid ejection device), II... Inkjet recording head unit (head unit), 1... Inkjet recording head (liquid ejection head), 2... Substrate, 10... Silicon substrate, 12... Pressure generating chamber, 13... Ink supply path, 14... Communication passage, 15... Communication section, 20... Nozzle plate, 21... Nozzle opening, 30... Protective substrate, 31... Piezoelectric element holding section, 32... Manifold section, 40... Compliance substrate, 50... Diaphragm, 51... Silicon oxide layer, 52... Oxide layer, 60... First electrode, 61... Orientation control layer, 70... Piezoelectric layer, 80... Second electrode, 90... Lead electrode, 100... Manifold, 300... Piezoelectric element, 400 Piezoelectric substrate.

Claims

1. Substrate and, An electrode formed on the substrate, A piezoelectric layer is formed on the electrode, comprising a thin film containing potassium, sodium, and niobium, A piezoelectric substrate equipped with, The piezoelectric layer further contains lithium, The integrated intensity of peak 2 when the surface of the piezoelectric layer is measured by Fourier transform infrared spectroscopy. The value obtained by dividing IR2 by the integrated intensity IR1 of peak 1, IR2 / IR1, is less than 0.

086. A piezoelectric substrate characterized by the following. Here, peak 1 is the most prominent of the peaks detected at wavelengths of 475 to 700 cm⁻¹. The area intensity of the strong peak is such that peak 2 is detected at wavelengths of 1200 to 1645 cm⁻¹. This is the sum of the area intensities of the peaks that are produced.

2. The piezoelectric substrate according to claim 1, characterized in that the IR2 / IR1 ratio is 0.05 or greater.

3. The pressure according to claim 1, characterized in that the lithium content is 10 mol% or less. Circuit board.

4. A substrate and, An electrode formed on the substrate, A piezoelectric layer is formed on the electrode, comprising a thin film containing potassium, sodium, and niobium, A piezoelectric substrate equipped with, The piezoelectric layer further comprises at least one of manganese and copper. The integrated intensity of peak 2 when the surface of the piezoelectric layer is measured by Fourier transform infrared spectroscopy. The value obtained by dividing IR2 by the integrated intensity IR1 of peak 1, IR2 / IR1, is less than 0.

086. A piezoelectric substrate characterized by the following. Here, peak 1 is the most prominent of the peaks detected at wavelengths of 475 to 700 cm⁻¹. The area intensity of the strong peak is such that peak 2 is detected at wavelengths of 1200 to 1645 cm⁻¹. This is the sum of the area intensities of the peaks that are produced.

5. The present invention is characterized in that an orientation control layer is provided between the piezoelectric layer and the electrode. A piezoelectric substrate.

6. Substrate and, A first electrode formed on the substrate, A piezoelectric layer is formed on the first electrode and is a thin film containing potassium, sodium, and niobium, A second electrode formed on the piezoelectric layer, A piezoelectric element comprising, The piezoelectric layer further contains lithium, The integrated intensity of peak 2 when the surface of the piezoelectric layer is measured by Fourier transform infrared spectroscopy. The value obtained by dividing IR2 by the integrated intensity IR1 of peak 1, IR2 / IR1, is less than 0.

086. A piezoelectric element characterized by the following. Here, peak 1 is the most prominent of the peaks detected at wavelengths of 475 to 700 cm⁻¹. The area intensity of the strong peak is such that peak 2 is detected at wavelengths of 1200 to 1645 cm⁻¹. This is the sum of the area intensities of the peaks that are produced.

7. A substrate and, An electrode formed on the substrate, A piezoelectric layer is formed on the electrode, comprising a thin film containing potassium, sodium, and niobium, A piezoelectric element comprising, The piezoelectric layer further comprises at least one of manganese and copper. The integrated intensity of peak 2 when the surface of the piezoelectric layer is measured by Fourier transform infrared spectroscopy. The value obtained by dividing IR2 by the integrated intensity IR1 of peak 1, IR2 / IR1, is less than 0.

086. A piezoelectric element characterized by the following. Here, peak 1 is the most prominent of the peaks detected at wavelengths of 475 to 700 cm⁻¹. The area intensity of the strong peak is such that peak 2 is detected at wavelengths of 1200 to 1645 cm⁻¹. This is the sum of the area intensities of the peaks that are produced.

8. A piezoelectric element application device characterized by comprising the piezoelectric element described in claim 6 or 7.

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