JP2022041246A - Manufacturing method of piezoelectric element and piezoelectric element - Google Patents

Abstract

To provide a manufacturing method of a piezoelectric element capable of producing a piezoelectric element having excellent piezoelectricity and ferroelectricity at lower temperature by a CSD method.SOLUTION: A manufacturing method of a piezoelectric element including a substrate, a first electrode layer, a piezoelectric layer, and a second electrode layer in this order includes an LNO layer forming step. The first electrode layer includes an LNO layer made of lanthanum nickelate (LaNiO3) ceramics. The piezoelectric layer includes lead zirconate titanate-based ceramics and is formed on the surface of the LNO layer. In the LNO layer forming step, a first film including a lanthanum atom, a nickel atom, and an organic solvent having 1 or more and 4 or less carbon atoms is heated to a temperature of 450°C or more and 600°C or less at a heating rate of 10°C/sec or more. Then, this temperature is maintained to form an LNO layer.SELECTED DRAWING: Figure 4

Description

Application for application of Article 30, Paragraph 2 of the Patent Act Reiwa 1st year published on pages 24 to 25 of the 35th Japan Ceramics Association Kanto Branch Research Presentation Abstracts, published by the Japan Ceramics Association September 3-4 Published at the 35th Japan Ceramics Association Kanto Branch Research Presentation November 20, 1st Reiwa Published by the Japan Ceramics Association 36th Japan-Korea International Ceramics Seminar Program Collection, Poster Session P-26 Published at Reiwa November 20-23, 1st Published at the 36th Japan-Korea International Ceramics Seminar Reiwa January 9, 2nd Executive Committee Chairman Masanori Fuji Issued 58th Japan Ceramics Basic Science Discussion Meeting Lecture Abstracts, published on page 155 Reiwa January 9-10, 2nd published at the 58th Japan Ceramics Basic Science Conference

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

In recent years, MEMS (Micro Electro Mechanical Systems) devices using a lead titanium zirconate (Pb (Ti, Zr) O ₃ ) thin film (hereinafter referred to as “PZT thin film”) having piezoelectric properties have attracted attention.

It is known that the PZT thin film has different physical constants depending on its orientation direction. In particular, the PZT thin film having the MPB (Morphotropic phase boundary) composition of the tetragonal system, the rhombohedral system and its boundary exhibits high piezoelectricity and ferroelectricity by controlling the c-axis orientation ((001) orientation). .. That is, the c-axis orientation controlled PZT thin film exhibits a high piezoelectric constant d ₃₃ and a high residual polarization value Pr.

As a method for forming a PZT thin film, a CSD (Chemical Solution Depositoon) method and a sputtering method are known. Among them, the CSD method makes it easy to control the composition of the PZT thin film, and unlike the sputtering method, a uniform PZT thin film can be easily formed on a large substrate. Further, the CSD method is low cost because it does not require expensive equipment such as a vacuum device. Therefore, research is being actively conducted to form a PZT thin film whose c-axis orientation is controlled by the CSD method.

Patent Document 1 discloses a method for manufacturing a piezoelectric element by the CSD method. The manufacturing method disclosed in Patent Document 1 includes a lower electrode layer forming step, a piezoelectric layer forming step, and an upper electrode layer forming step. The lower electrode layer forming step, the piezoelectric layer forming step, and the upper electrode layer forming step are executed in this order.

In the lower electrode layer forming step, a lower electrode made of lanthanum nickelate (LaNiO ₃ ) ceramics is formed on the surface of the silicon substrate. Specifically, the surface of the silicon substrate is coated with the LNO precursor solution, and rapidly heated at a heating rate of 200 ° C./min and 700 ° C. for 5 minutes using a rapid heating furnace (RTA: Rapid Thermal Annealing). Crystallize lanthanum nickelate ceramics.

The LNO precursor solution consists of lanthanum nitrate, nickel acetate, 2-methoxyethanol, and 2-aminoethanol.

In the piezoelectric layer forming step, a piezoelectric layer made of lead zirconate titanate ceramics is formed on the surface of the lower electrode layer. Specifically, the PZT precursor solution is applied to the surface of the lower electrode layer and rapidly heated using RTA at a heating rate of 200 ° C./min and 650 ° C. for 5 minutes to crystallize lead zirconate titanate ceramics. To make it.

The PZT precursor precursor solution is obtained by mixing a Ti—Zr solution with a Pb solution. The Ti-Zr solution consists of titanium isopropoxide, zircon normal propoxide, and absolute ethanol. The Pb solution consists of lead acetate (II) and absolute ethanol.

In the upper electrode layer forming step, an upper electrode layer made of gold is formed by an ion beam vapor deposition method or the like.

Japanese Unexamined Patent Publication No. 2008-251916

However, in the manufacturing method disclosed in Patent Document 1, the substrate is exposed to a high temperature of 650 ° C. or higher. Therefore, a substrate having thermal stability such as a silicon substrate, a magnesium oxide single crystal substrate, a strontium titanate single crystal substrate, and a refractory glass substrate is required as the substrate. As a result, the degree of freedom in designing the piezoelectric device may be limited.

The present disclosure has been made in view of the above.
An object to be solved by one embodiment of the present disclosure is to provide a method for manufacturing a piezoelectric element capable of producing a piezoelectric element having excellent piezoelectricity and ferroelectricity at a lower temperature by the CSD method. ..
An object to be solved by another embodiment of the present disclosure is to provide a piezoelectric element having excellent piezoelectricity and ferroelectricity.

The means for solving the above problems include the following embodiments.

<1> A method for manufacturing a piezoelectric element including a substrate, a first electrode layer, a piezoelectric layer, and a second electrode layer in this order.
The first electrode layer has an LNO layer made of lanthanum nickelate ceramics.
The piezoelectric layer has lead zirconate titanate-based ceramics and is formed on the surface of the LNO layer.
The first film containing a lanthanum atom, a nickel atom, and an organic solvent having 1 or more and 4 or less carbon atoms is heated to a temperature of 450 ° C. or higher and 600 ° C. or lower at a heating rate of 10 ° C./sec or higher to maintain the temperature. A method for manufacturing a piezoelectric element, which comprises a step of forming an LNO layer for forming the LNO layer.

<2> The method for producing a piezoelectric device according to <1>, wherein the organic solvent having 1 or more and 4 or less carbon atoms contains alcohol.

<3> The method for manufacturing a piezoelectric element according to <1> or <2>, wherein the temperature rising rate is 30 ° C./sec or more.

<4> The method for producing a piezoelectric element according to any one of <1> to <3>, wherein the first film contains at least one of 2-methoxyethanol and 2-aminoethanol.

<5> The piezoelectric layer includes a base layer formed on the surface of the LNO layer and a PZT layer made of the lead zirconate titanate ceramics formed on the surface of the base layer.
A step of forming a base layer on the surface of the LNO layer by heating a second film containing a lead atom, a titanium atom, and a first organic solvent at 450 ° C. or higher and 600 ° C. or lower.
A PZT layer forming step of heating a third film containing a lead atom, a titanium atom, a zirconium atom, and a second organic solvent at 450 ° C. or higher and 600 ° C. or lower to form the PZT layer on the surface of the base layer. The method for manufacturing a piezoelectric element according to any one of <1> to <4>, which comprises.

<6> The second film further contains a zirconium atom and contains a zirconium atom.
The method for manufacturing a piezoelectric element according to <5>, wherein the ratio of the zirconium atom to the titanium atom of the second film is more than 0% and less than 25% in terms of molar ratio.

<7> In the PZT layer forming step,
A first solution is prepared by adding a titanium alkoxide compound, a zirconium alkoxide compound, a third organic solvent, and at least one of a monocarboxylic acid having 1 to 8 carbon atoms and a dicarboxylic acid having 2 to 8 carbon atoms. death,
After adding water to the first solution, a second solution containing a lead atom and a fourth organic solvent was further added to prepare a third solution.
The method for manufacturing a piezoelectric element according to <5> or <6>, wherein the third solution is applied to the surface of the base layer to form the third film.

<8> The piezoelectric layer includes a PZT layer made of lead zirconate titanate ceramics formed on the surface of the LNO layer.
A first solution is prepared by adding a titanium alkoxide compound, a zirconium alkoxide compound, a first organic solvent, and at least one of a monocarboxylic acid having 1 or more and 8 or less carbon atoms and a dicarboxylic acid having 2 or more and 8 or less carbon atoms. death,
After adding water to the first solution, a second solution containing a lead atom and a second organic solvent is further added to prepare a third solution.
The third solution is applied to the surface of the LNO layer to form a third film containing a lead atom, a titanium atom, a zirconium atom, and a third organic solvent.
The item according to any one of <1> to <4>, which comprises a PZT layer forming step of heating the third film at 450 ° C. or higher and 600 ° C. or lower to form the PZT layer on the surface of the LNO layer. Method for manufacturing piezoelectric elements.

（式（１）中、［Ａ_Ｘ］は、前記ＰＺＴ層の厚み方向の断面を走査透過型電子顕微鏡（ＳＴＥＭ－ＥＤＸ）で前記厚み方向に沿って分析をした、前記ＬＮＯ層の表面から前記厚み方向の前記第２電極層側に第１距離離れた第１位置の濃度比（Ｔｉ濃度／Ｐｂ濃度）を示し、［Ａ_{Ｘ＋１００}］は、前記分析をした、前記第１位置から前記厚み方向の前記第２電極層側に１００ｎｍ離れた第２位置の濃度比（Ｔｉ濃度／Ｐｂ濃度）を示し、
式（２）中、［Ｂ_Ｘ］は、前記分析をした、前記第１位置の濃度比（Ｚｒ濃度／Ｐｂ濃度）を示し、［Ｂ_{Ｘ＋１００}］は、前記分析をした、前記第２位置の濃度比（Ｚｒ濃度／Ｐｂ濃度）を示す。） <9> The substrate, the first electrode layer, the piezoelectric layer, and the second electrode layer are provided in this order.
The first electrode layer has an LNO layer made of lanthanum nickelate ceramics.
The piezoelectric layer has a PZT layer made of lead zirconate titanate ceramics.
The volatility A represented by the following equation (1) is 10% or less.
A piezoelectric element having a volatility B represented by the following equation (2) of 10% or less.

In the formula (1), [ _AX ] is obtained by analyzing the cross section of the PZT layer in the thickness direction with a scanning transmission electron microscope (STEM-EDX) along the thickness direction from the surface of the LNO layer. The concentration ratio (Ti concentration / Pb concentration) of the first position separated by the first distance is shown on the second electrode layer side in the thickness direction, and [ _{AX + 100} ] indicates the thickness direction from the first position in which the analysis was performed. The concentration ratio (Ti concentration / Pb concentration) of the second position separated by 100 nm is shown on the second electrode layer side of the above.
In the formula (2), [ _BX ] indicates the concentration ratio (Zr concentration / Pb concentration) of the first position of the analysis, and [ _{BX + 100} ] indicates the concentration ratio of the second position of the analysis. The concentration ratio (Zr concentration / Pb concentration) is shown. )

According to one embodiment of the present disclosure, a method for manufacturing a piezoelectric element capable of producing a piezoelectric element having excellent piezoelectricity and ferroelectricity at a lower temperature is provided by the CSD method.
According to another embodiment of the present disclosure, a piezoelectric device having excellent piezoelectricity and ferroelectricity is provided.

It is sectional drawing of one aspect of the piezoelectric element which concerns on embodiment of this disclosure. It is a figure for demonstrating the partial hydrolysis reaction of titanium alkoxide, zirconium alkoxide, and acetic acid which is a partial stabilizer. It is sectional drawing of another aspect of the piezoelectric element which concerns on embodiment of this disclosure. 6 is an X-ray diffraction pattern diagram of the LNO layer obtained in Example 1, Example 2, Comparative Example 1, and Comparative Example 5. It is a figure which shows the measurement result of the characteristic (PE hysteresis loop) of the piezoelectric element obtained in Example 1 and Example 2. FIG. It is a figure which shows the measurement result of the characteristic (PE hysteresis loop) of the piezoelectric element obtained in Example 3 and Example 4. FIG. The cross section of the PZT layer in the thickness direction of Reference Example 1 was scanned and line-analyzed along the thickness direction of the PZT layer with a scanning transmission electron microscope (STEM-EDX). It is a graph which shows the fluctuation of each of the ratio (Ti concentration / Pb concentration) and the concentration ratio (Zr concentration / Pb concentration). The cross section of the PZT layer in the thickness direction of Reference Example 2 was line-analyzed along the thickness direction of the PZT layer with STEM-EDX. ) And the fluctuation of the concentration ratio (Zr concentration / Pb concentration).

The contents of the present disclosure will be described in detail below.
The description of the constituents described below may be based on the representative embodiments of the present disclosure, but the present disclosure is not limited to such embodiments.

A method for manufacturing a piezoelectric element including the substrate, the first electrode layer, the piezoelectric layer, and the second electrode layer in this order of the present disclosure, wherein the first electrode layer has an LNO layer made of lanthanum nickelate ceramics. However, the piezoelectric layer has lead zirconate titanate-based ceramics and is formed on the surface of the LNO layer, and is a first film containing a lanthanum atom, a nickel atom, and an organic solvent having 1 or more and 4 or less carbon atoms. The temperature is increased to 450 ° C. or higher and 600 ° C. or lower at a heating rate of 10 ° C./sec or higher, and this temperature is maintained to form an LNO layer forming step.

This makes it possible to manufacture a piezoelectric element having excellent piezoelectricity and ferroelectricity at a lower temperature by the CSD method. This is presumed to be due to the following reasons.
Conventionally, it has been reported that by firing an LNO precursor at a crystallization temperature of a high temperature (for example, 700 ° C.), an LNO highly oriented in the (100) direction can be obtained. Therefore, in the preparation of the conventional LNO precursor solution, in order to calcin the LNO precursor at the high temperature of the first crystallization temperature, the LNO precursor is thermally stabilized by using a solvent having a large side chain. Specifically, 2-methoxyethanol and 2-aminoethanol were used as solvents having a large side chain. These solvents undergo an alcohol exchange reaction with, for example, lanthanum nitrate and nickel acetate in the process of preparing the LNO precursor solution to produce a thermally stable LNO precursor. In order to promote the thermal decomposition of the side chain of this thermally stable LNO precursor, the LNO precursor was calcined at a first crystallization temperature of 700 ° C. or higher. By doing so, an LNO highly oriented in the (100) direction was obtained.
On the other hand, in the present disclosure, the LNO precursor is exposed to a high temperature for a short period of time by heating the LNO precursor at a rapid temperature rise (10 ° C./sec or more). Further, in the first embodiment, an organic solvent having a side chain smaller than that of the conventional solvent and having 1 or more and 4 or less carbon atoms is used. Therefore, the thermal decomposition of the side chain of the LNO precursor can be promoted at the first crystallization temperature lower than the conventional one. That is, in the present disclosure, the LNO precursor is heated at a crystallization temperature lower than the conventional one by using an organic solvent having 1 or more carbon atoms and 4 or less carbon atoms and heating the LNO precursor at a heating rate of 10 ° C./sec or more. Even if the solution is fired, an LNO-based ceramic film highly oriented in the (100) direction can be obtained. As a result, high orientation and low temperature crystallization of the LNO-based ceramic film are realized.

（式（１）中、［Ａ_Ｘ］は、前記ＰＺＴ層の厚み方向の断面を走査透過型電子顕微鏡（ＳＴＥＭ－ＥＤＸ）で前記厚み方向に沿って分析をした、前記ＬＮＯ層の表面から前記厚み方向の前記第２電極層側に第１距離離れた第１位置の濃度比（Ｔｉ濃度／Ｐｂ濃度）を示し、［Ａ_{Ｘ＋１００}］は、前記分析をした、前記第１位置から前記厚み方向の前記第２電極層側に１００ｎｍ離れた第２位置の濃度比（Ｔｉ濃度／Ｐｂ濃度）を示し、
式（２）中、［Ｂ_Ｘ］は、前記分析をした、前記第１位置の濃度比（Ｚｒ濃度／Ｐｂ濃度）を示し、［Ｂ_{Ｘ＋１００}］は、前記分析をした、前記第２位置の濃度比（Ｚｒ濃度／Ｐｂ濃度）を示す。） The piezoelectric element of the present disclosure includes a substrate, a first electrode layer, a piezoelectric layer, and a second electrode layer in this order, and the first electrode layer has an LNO layer made of lanthanum nickelate ceramics and is piezoelectric. The body layer has a PZT layer made of lead zirconate titanate ceramics, the fluctuation rate A represented by the following formula (1) is 10% or less, and the fluctuation rate B represented by the following formula (2). Is 10% or less.

In the formula (1), [ _AX ] is obtained by analyzing the cross section of the PZT layer in the thickness direction with a scanning transmission electron microscope (STEM-EDX) along the thickness direction from the surface of the LNO layer. The concentration ratio (Ti concentration / Pb concentration) of the first position separated by the first distance is shown on the second electrode layer side in the thickness direction, and [ _{AX + 100} ] indicates the thickness direction from the first position in which the analysis was performed. The concentration ratio (Ti concentration / Pb concentration) of the second position separated by 100 nm is shown on the second electrode layer side of the above.
In the formula (2), [ _BX ] indicates the concentration ratio (Zr concentration / Pb concentration) of the first position of the analysis, and [ _{BX + 100} ] indicates the concentration ratio of the second position of the analysis. The concentration ratio (Zr concentration / Pb concentration) is shown. )

As a result, the piezoelectric element of the present disclosure is excellent in piezoelectricity and ferroelectricity.

Hereinafter, embodiments of the metal member, the metal resin composite, and the method for manufacturing the metal member according to the present disclosure will be described with reference to the drawings. Further, in the figure, the same or corresponding parts are designated by the same reference numerals and the description is not repeated.

(1) First Embodiment A method for manufacturing the piezoelectric element 1 and the piezoelectric element 1 according to the first embodiment of the present disclosure will be described.

(1.1) Piezoelectric element First, the first piezoelectric element 1 will be described with reference to FIG. 1. FIG. 1 is a cross-sectional view of the piezoelectric element 1 according to the first embodiment of the present disclosure.

As shown in FIG. 1, the piezoelectric element 1 includes a substrate 11, a first electrode layer 12, a piezoelectric layer 13, and a second electrode layer 14. The substrate 11, the first electrode layer 12, the piezoelectric layer 13, and the second electrode layer 14 are laminated in this order.

(1.1.1) Substrate Examples of the substrate 11 include a glass substrate, a semiconductor single crystal substrate, a metal substrate, a ceramics substrate, a heat-resistant plastic substrate, and the like. Examples of the material of the glass substrate include aminosilicate glass, quartz glass, borosilicate glass and the like. Examples of the material of the semiconductor single crystal substrate include silicon, magnesium oxide, strontium titanate doped with Sr or La, and the like. Examples of the material of the metal substrate include stainless steel, titanium, aluminum, magnesium and the like. Examples of the material of the ceramic substrate include alumina, zirconia and the like. The size of the substrate 11 and the like are appropriately adjusted according to the application of the piezoelectric element 1 and the like.

(1.1.2) First Electrode Layer In the first embodiment, the first electrode layer 12 is made of an LNO layer 12a made of lanthanum nickelate ceramics.

Lanthanum nickelate ceramics contain lanthanum nickelate (LaNiO ₃ ) (hereinafter referred to as "LNO") as a main component. The main component means a component having a ratio of 60% by mass or more to all the components constituting the lanthanum nickelate ceramics.

LNO has a space group of R-3c (“-3” is a symbol with a bar on top of 3), and has a perovskite-type structure distorted into a rhombohedron (rhombohedral crystal system: a0 = 5.461Å (a0). = Ap), α = 60 °, pseudo-cubic system: a0 = 3.84 Å). LNO is an oxide having a resistivity of 1 × 10 ^-3 (Ω · cm, 300K) and having metallic electrical conductivity. In LNO, the metal-insulator transition does not occur even if the temperature changes.

The lanthanum nickelate-based ceramics include not only LNO but also ceramics in which a part of nickel in LNO is replaced with another metal (hereinafter, referred to as “substituent metal”). Substituent metals include at least one metal selected from the group consisting of iron, aluminum, manganese, and cobalt. Examples of the ceramics in which a part of nickel of LNO is replaced with a substituted metal include LaNiO ₃ -LaFeO ₃ substituted with iron, LaNiO ₃ -LaAlO ₃ substituted with aluminum, LaNiO ₃ -LaMnO ₃ substituted with manganese, and cobalt. Examples thereof include substituted LaNiO ₃ -LaCoO ₃ . A part of nickel in LNO may be substituted with two or more kinds of substituted metals.

The film thickness of the first electrode layer 12 is appropriately adjusted according to the intended use of the piezoelectric element 1, and is preferably 0.1 μm or more and 0.4 μm or less.

(1.1.3) Piezoelectric layer In the first embodiment, the piezoelectric layer 13 is made of a PZT layer 13a made of lead zirconate titanate-based ceramics.

Lead zirconate titanate-based ceramics contain lead zirconate titanate (hereinafter referred to as "PZT") as a main component. The main component means a component having a ratio of 80% by mass or more to all the components constituting the lead zirconate titanate ceramics.

PZT is represented by the general formula Pb (Zr _x Ti _1-x ) O ₃ (0.4 <x <1)). The ratio of zirconium atom to titanium atom (Zr / Ti) of PZT is preferably 67% (40/60) or more and 233% (70/30) or less, more preferably 67% (40/60) or more in terms of molar ratio. It is 150% (60/40) or less. The ratio of zirconium to titanium (Zr / Ti) in PZT is particularly preferably the boundary between the tetragonal system and the rhombic crystal system (molphotolopic phase) from the viewpoint of improving the piezoelectricity and ferroelectricity of the piezoelectric element 1. The composition is 108% (52/48) near the boundary).

It is preferable that the composition distribution of the PZT layer 13a in the thickness direction is uniform. As a result, the piezoelectric element 1 is superior in piezoelectricity and ferroelectricity to a configuration in which the composition distribution in the thickness direction is not uniform.
Specifically, it is preferable that the volatility A represented by the following formula (1) is 10% or less, and the volatility B represented by the following formula (2) is 10% or less. If each of the volatility A and the volatility B is 10% or less, it can be considered that the composition distribution of the PZT layer 13a in the thickness direction is uniform.

In formula (1), [ _AX ] is the concentration at the first position obtained by analyzing the cross section of the PZT layer 13a in the thickness direction with a scanning transmission electron microscope (STEM-EDX) along the thickness direction of the PZT layer 13a. The ratio (Ti concentration / Pb concentration) is shown. The first position indicates a position one distance away from the surface S12 of the LNO layer 12a on the side of the second electrode layer 14 in the thickness direction of the PZT layer 13a.
In the formula (1), in [ _{AX + 100} ], the cross section of the PZT layer 13a in the thickness direction was analyzed by STEM-EDX along the thickness direction of the PZT layer 13a, and the concentration ratio (Ti concentration / Pb concentration) at the second position was analyzed. ) Is shown. The second position indicates a position 100 nm away from the first position on the side of the second electrode layer 14 in the thickness direction of the PZT layer 13a.
In the formula (2), [ _BX ] is a concentration ratio (Zr concentration / Pb concentration) at the first position obtained by analyzing a cross section of the PZT layer 13a in the thickness direction by STEM-EDX along the thickness direction of the PZT layer 13a. ) Is shown.
In the formula (2), in [ _{BX + 100} ], the cross section of the PZT layer 13a in the thickness direction was analyzed by STEM-EDX along the thickness direction of the PZT layer 13a, and the concentration ratio (Zr concentration / Pb concentration) at the second position was analyzed. ) Is shown.

The first distance is not particularly limited, and is preferably 300 nm or more and 600 nm or less. When the first distance is 300 nm or more and 600 nm or less, the volatility A and the volatility B indicate the variation in the composition of the PZT layer 13a in the vicinity of the substrate 11. In particular, when the volatility A and the volatility B in the vicinity of the substrate 11 are 10% or less, it can be considered that the composition distribution of the PZT layer 13a in the thickness direction is uniform.
The volatility A is preferably 10% or less, more preferably 8% or less, and the lower the volatility A, the more preferable it is from the viewpoint of exhibiting superior piezoelectricity and ferroelectricity to the piezoelectric element 1. The volatility b is preferably 10% or less, more preferably 8% or less, and the lower the volatility b, the more preferable it is from the viewpoint of exhibiting superior piezoelectricity and ferroelectricity to the piezoelectric element 1.

The PZT layer 13a having a uniform composition distribution in the thickness direction can be obtained, for example, by using a PZT precursor solution using the partial hydrolysis method described later in the manufacturing process thereof.

Lead zirconate titanate ceramics are not only PZT but also lead magnesium niobate (PMN), which is a ceramic containing PZT as a main component and a small amount of at least one metal selected from the group consisting of Sr, Nb, and Al. ) And lead zirconate tit (PZN) may contain ceramics containing at least one of them.

The film thickness of the piezoelectric layer 13 is appropriately adjusted according to the intended use of the piezoelectric element 1, and is preferably 0.5 μm or more and 5.0 μm or less.

The tetragonal PZT is a material having a lattice constant of a = b = 4.036 Å and c = 4.146 Å in terms of bulk ceramics. Therefore, the LNO having a pseudo-cubic structure having a lattice constant of a = 3.84 Å has good lattice matching with the (001) plane and the (100) plane of PZT.

The lattice matching indicates the lattice consistency between the unit cell of PZT and the unit cell of LNO. In general, when a certain crystal plane is exposed on the surface, a force that tries to match the crystal lattice with the crystal lattice of the film formed on the surface acts to form an epitaxial crystal nucleus at the interface. It is known to be easy to form.

It is preferable that the difference in lattice constant between the (001) plane and the (100) plane, which are the main orientation planes of the PZT layer 13a, and the main orientation plane S12 of the LNO layer 12a is within ± 10% in absolute value. If the difference in lattice constant is within this range, the orientation of either the (001) plane or the (100) plane of the PZT layer 13a can be increased. Then, an epitaxial crystal nucleus can be formed at the interface S12 between the LNO layer 12a and the PZT layer 13a. In the orientation control by lattice matching, it is difficult to realize a film selectively oriented to either the (001) plane or the (100) plane.

By producing LNO by the production method described later, it is possible to realize a film preferentially oriented to the (100) plane of a pseudo-cubic system on the surface of various substrates. Therefore, the LNO layer 12a not only functions as the first electrode layer 12, but also functions as the orientation control layer of the PZT layer 13a. From this, the (001) plane of PZT (lattice constant: a = 4.036, c = 4.146 Å) having good lattice matching with the surface of LNO oriented to the (100) plane (lattice constant: 3.84 Å) or (100) Surfaces are selectively generated.

(1.1.4) Second Electrode Layer The material of the second electrode layer 14 may be any conductive material, and examples thereof include a metal and a conductive metal oxide. Examples of the metal include gold, silver, platinum, iridium, ruthenium and the like. Examples of the conductive metal oxide include tin-doped indium oxide (ITO), zinc oxide, gallium-doped zinc oxide (GZO), aluminum-doped zinc oxide (AZO), tin oxide, antimony-doped tin oxide (ATO), and fluorine-doped tin oxide (TO). FTO), niobium-doped titanium oxide (TNO) and the like. The film thickness of the second electrode layer 14 may be appropriately adjusted according to the intended use of the piezoelectric element 1, and is preferably 0.1 μm or more and 0.4 μm or less.

(1.1.5) Applications of Piezoelectric Element The piezoelectric element 1 is suitably used for sensors, actuators, optical devices, micropumps, ceramic capacitors, ferroelectric memories and the like used in various electronic devices. Examples of the sensor include an angular velocity sensor and an infrared sensor. Examples of the actuator include a piezoelectric actuator, an ultrasonic motor, and the like. Examples of the optical device include an optical waveguide and an optical switch.
In particular, in the first embodiment, as will be described later, the temperature of the thermal history of the substrate 11 can be 550 ° C. or lower in the manufacturing process. Therefore, as the base material 11, an aminosilicate glass plate, which has not been used in the conventional piezoelectric element, can be used. As a result, the piezoelectric element 1 is suitably used for a transparent electronic member such as a touch panel of a smartphone.

(1.2) Method for Manufacturing a Piezoelectric Device Next, a method for manufacturing the piezoelectric device 1 according to the first embodiment will be described with reference to FIG. 2.

The method for manufacturing the piezoelectric element 1 according to the first embodiment includes a first electrode layer forming step, a piezoelectric layer forming step, and a second electrode layer forming step. The first electrode layer forming step, the piezoelectric layer forming step, and the second electrode layer forming step are executed in this order. As a result, the piezoelectric element 1 according to the first embodiment is obtained.

(1.2.1) First Electrode Layer Forming Step In the first embodiment, the first electrode layer forming step includes a first solution preparation step, a first coating step, a first drying step, and a first calcining step. It has a step and a first firing step. The first solution preparation step, the first coating step, the first drying step, the first calcining step, and the first firing step are executed in this order. As a result, the first electrode layer 12 made of the LNO layer 12a is formed on the surface of the substrate 11. Hereinafter, the first electrode layer forming step may be referred to as an “LNO layer forming step”.

(1.2.1.1) First solution preparation step In the first solution preparation step, an LNO precursor solution as a raw material for the LNO layer 12a is prepared. The LNO precursor solution is prepared by adding at least a lanthanum compound, a nickel compound, and an organic solvent having 1 or more and 4 or less carbon atoms.

Examples of the lanthanum compound include lanthanum nitrate, lanthanum chloride, lanthanum carboxylate, and lanthanum alkoxide. Examples of the lanthanum carboxylate include lanthanum acetate, lanthanum octylate, and lanthanum 2-ethylhexanoate. Examples of the lanthanum alkoxide include lanthanum isopropoxide, lanthanum butoxide, lanthanum ethoxydo, lanthanum methoxyethoxydo and the like. Among them, lanthanum nitrate is preferable as the lanthanum compound.

Examples of the nickel compound include nickel nitrate, nickel chloride, nickel carboxylate, nickel alkoxide and the like. Examples of the nickel carboxylate include nickel acetate, nickel octylate, nickel 2-ethylhexanoate and the like. Examples of the nickel alkoxide include nickel isopropoxide, nickel butoxide, nickel ethoxyde, nickel methoxyethoxydo and the like. Among them, nickel acetate is preferable as the nickel compound.

The organic solvent having 1 or more and 4 or less carbon atoms is preferably an organic solvent having high solubility in each of the lanthanum compound and the nickel compound and thermally decomposing at a low temperature (for example, 300 ° C.). Specifically, examples of the organic solvent having 1 or more and 4 or less carbon atoms include alcohols having 1 or more and 4 or less carbon atoms, ethers having 1 or more and 4 or less carbon atoms, and the like. Examples of the alcohol having 1 or more and 4 or less carbon atoms include methanol, ethanol, butanol, propanol and the like. Examples of the ether having 1 or more and 4 or less carbon atoms include dimethyl ether and diethyl ether. These organic solvents having 1 or more and 4 or less carbon atoms may be used alone or in combination of two or more. Among them, alcohol is preferable, and ethanol is more preferable as the organic solvent having 1 or more and 4 or less carbon atoms. The amount of the organic solvent added having 1 to 4 carbon atoms is preferably 400 parts by mass or more and 2000 parts by mass or less, more preferably 500 parts by mass or more and 2000 parts by mass or less, based on 100 parts by mass of the total of the lanthanum compound and the nickel compound. Is.

The LNO precursor solution may contain another organic solvent different from the organic solvent having 1 or more and 4 or less carbon atoms. Examples of other organic solvents include 2-methoxyethanol and 2-aminoethanol. These other organic solvents may be used alone or in combination of two or more. Among them, the LNO precursor solution preferably contains at least one of 2-methoxyethanol and 2-aminoethanol. When the LNO precursor solution contains at least one of 2-methoxyethanol and 2-aminoethanol, the piezoelectric element 1 having more excellent piezoelectricity and ferroelectricity can be obtained. The mixing ratio of the other organic solvent is preferably 5 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the organic solvent having 1 or more and 4 or less carbon atoms.

(1.2.1.2) First coating step In the first coating step, the LNO precursor solution is coated on the surface of the base material 11. As a result, an LNO coating film is formed on the surface of the base material 11. The LNO coating film contains a lanthanum atom, a nickel atom, and an organic solvent having 1 or more and 4 or less carbon atoms. The LNO coating film is an example of the first film.
The method for applying the LNO coating film is not particularly limited, and examples thereof include a spin coating method, a dip coating method, and a spray coating method. In the spin coating method, by controlling the number of rotations per unit time, a thin film having a uniform film thickness of the LNO coating film can be uniformly applied to the surface of the substrate 11. For example, the film thickness can be reduced by increasing the rotation speed of the substrate 11. Further, in the dip coating method, the film thickness can be reduced by increasing the pulling speed of the substrate 11.

The film thickness of the LNO coating film is preferably 0.1 μm or more and 0.3 μm or less.

(1.2.1.3) First drying step In the first drying step, the LNO coating film is dried. Thereby, the physically adsorbed water in the obtained LNO layer 12a can be removed. The drying temperature is preferably more than 100 ° C and less than 200 ° C.

(1.2.1.4) First calcining step In the first calcining step, the LNO coating film is calcined. Thereby, it is possible to suppress the organic component from remaining in the obtained LNO layer 12a. The calcination temperature is preferably 200 ° C. or higher and lower than 400 ° C.

(1.2.1.5) First firing step In the first firing step, an LNO coated film is heated at a heating rate of 10 ° C./sec or more using a rapid heating furnace (RTA) (RTA) to 450. The temperature is raised to a temperature of ° C. or higher and 600 ° C. or lower (hereinafter, referred to as “first crystallization temperature”), the first crystallization temperature is maintained, and LNO is crystallized. As a result, the LNO layer 12a highly oriented in the (100) plane direction is obtained. This is presumed to be due to the following reasons.
That is, it has been reported that by firing the LNO precursor at a high temperature (for example, 700 ° C.) of the first crystallization temperature, LNO highly oriented in the (100) direction can be obtained. Therefore, in the preparation of the conventional LNO precursor solution, in order to calcin the LNO precursor at the high temperature of the first crystallization temperature, the LNO precursor is thermally stabilized by using a solvent having a large side chain. Specifically, 2-methoxyethanol and 2-aminoethanol were used as solvents having a large side chain. These solvents undergo an alcohol exchange reaction with, for example, lanthanum nitrate and nickel acetate in the process of preparing the LNO precursor solution to produce a thermally stable LNO precursor. In order to promote the thermal decomposition of the side chain of this thermally stable LNO precursor, the LNO precursor was calcined at a first crystallization temperature of 700 ° C. or higher. By doing so, an LNO highly oriented in the (100) direction was obtained.
On the other hand, in the first embodiment, the LNO precursor is exposed to a high temperature for a short time by heating the LNO precursor at a rapid temperature rise (10 ° C./sec or more). Further, in the first embodiment, an organic solvent having a side chain smaller than that of the conventional solvent and having 1 or more and 4 or less carbon atoms is used. Therefore, the thermal decomposition of the side chain of the LNO precursor can be promoted at the first crystallization temperature lower than the conventional one. That is, in the first embodiment, the first crystallization temperature is lower than the conventional one by using an organic solvent having 1 or more and 4 or less carbon atoms and heating the LNO precursor at a heating rate of 10 ° C./sec or more. Even if the LNO precursor solution is fired in (100), an LNO-based ceramic film highly oriented in the (100) direction can be obtained. As a result, high orientation and low temperature crystallization of the LNO-based ceramic film are realized.

Further, the LNO layer 12a tends to be oriented in the (100) plane direction regardless of the substrate 11. Therefore, the degree of freedom in selecting the substrate 11 is high.

The rate of temperature rise is 10 ° C./sec or higher, preferably 30 ° C./sec or higher. When the temperature rising rate is 30 ° C./sec or more, the piezoelectric element 1 having more excellent piezoelectricity and ferroelectricity can be obtained. This is because when the heating rate is 30 ° C./sec or higher, the LNO precursor is exposed to a high temperature at which residual organic matter is thermally decomposed in a short time, and the LNO is more likely to be highly oriented in the (100) direction. As a result, it is presumed that the C-axis orientation of the PZT layer 13a is easily controlled.

The first crystallization temperature is 450 ° C. or higher and 600 ° C. or lower, preferably 500 ° C. or higher and 600 ° C. or lower, and more preferably 500 ° C. or higher and 550 ° C. or lower. If the first crystallization temperature is less than 450 ° C., the piezoelectricity and ferroelectricity of the obtained piezoelectric element 1 are not sufficient. Further, in order to sufficiently promote the crystallization of the LNO-based ceramics, the holding time of the first crystallization temperature is preferably 10 minutes or more.

The desired film thickness of the LNO layer 12a can be obtained, for example, by repeating this cycle a plurality of times, with the first coating step, the first drying step, the first calcining step, and the first firing step as one cycle. In the first embodiment, an LNO layer 12a having a film thickness of 0.04 μm or more can be formed per cycle.

(1.2.2) Piezoelectric layer forming step In the first embodiment, the piezoelectric layer forming step includes a second solution preparation step, a second coating step, a second drying step, and a second calcining step. , The second firing step is included. The second solution preparation step, the second coating step, the second drying step, the second calcining step, and the second firing step are executed in this order. As a result, the PZT layer 13a is formed on the surface S12 of the LNO layer 12a. Hereinafter, the piezoelectric layer forming step may be referred to as a “PZT layer forming step”.

(1.2.2.1) Second solution preparation step In the second solution preparation step, the Pb solution and the Ti—Zr solution are mixed and reacted to prepare a PZT precursor solution as a raw material for the PZT layer 13a. .. The Pb solution is an example of the second solution according to claim 8. The Ti—Zr solution is an example of the first solution according to claim 8. The PZT precursor solution is an example of the third solution according to claim 8.

When mixing the Pb solution and the first Ti—Zr solution, the amount of the Pb component added is based on the stoichiometric composition (Pb (Zr _x Ti _1-x ) O ₃ (0.4 <x <1)). It is preferably 15 mol% to 20 mol% excess. This makes it possible to make up for the shortage of lead components due to volatilization in the second firing step.

(A) Pb solution The Pb solution can be obtained, for example, by adding a lead compound to a first organic solvent and refluxing ammonia gas while bubbling. When the lead compound contains hydrate, the lead compound is dried, and then the dried lead compound is added to the first organic solvent. The Pb solution contains lead and a first organic solvent. The first organic solvent is an example of the second organic solvent in claim 8.
Examples of the lead compound include lead (II) acetate, lead diisoproxide, lead dibutoxide and the like. These lead compounds may be used alone or in combination of two or more.
Examples of the first organic solvent include ethanol, xylene, butanol and the like. These first organic solvents may be used alone or in combination of two or more.

(B) First Ti-Zr Solution In the first embodiment, the first Ti-Zr solution is prepared by a partial hydrolysis method. Specifically, the first titanium alkoxide compound, the first zirconium alkoxide compound, the second organic solvent, and at least one of a monocarboxylic acid having 1 or more and 8 or less carbon atoms and a dicarboxylic acid having 2 or more and 8 or less carbon atoms (partially stabilized). The agent) is added at least to prepare a first mixed solution, and water is added to the first mixed solution to perform partial hydrolysis and polycondensation. The first mixed solution is an example of the first solution. The second organic solvent is an example of the first organic solvent in claim 8.

When mixing the first titanium alkoxide compound and the first zirconium alkoxide compound, the ratio of the zirconium atom to the titanium atom (Zr / Ti) is preferably 67% (40/60) or more and 233% (70/30) in terms of molar ratio. ) Or less, more preferably 67% (40/60) or more and 150% (60/40). The ratio of zirconium to titanium (Zr / Ti) is particularly preferably 108% (52/48), which is a composition near the boundary between the tetragonal system and the rhombohedral system of PZT (the morphotropic phase boundary).

Examples of the first titanium alkoxide compound include titanium isopropoxide and titanium tetrapropoxide. These first titanium alkoxide compounds may be used alone or in combination of two or more.

Examples of the first zirconium alkoxide compound include zirconium normal propoxide and zirconium tetrabutoxide. These first zirconium alkoxide compounds may be used alone or in combination of two or more.

Examples of the second organic solvent include ethanol, xylene, butanol and the like. These second organic solvents may be used alone or in combination of two or more. The second organic solvent may be the same as or different from the first organic solvent.

At least one of a monocarboxylic acid having 1 to 8 carbon atoms and a dicarboxylic acid having 2 to 8 carbon atoms functions as a partial stabilizer for the PZT precursor, as will be described later.
Examples of the monocarboxylic acid having 1 or more and 8 or less carbon atoms include acetic acid, propionic acid, butanoic acid, pentanoic acid, 2-methylbutanoic acid, 3-methylbutanoic acid, hexanoic acid, 2-methylpentanoic acid and 3-methylpentanoic acid. , 4-Methylpentanoic acid, 2-ethylbutanoic acid, 3-ethylbutanoic acid, heptanic acid, 2-methylhexanoic acid, 3-methylhexanoic acid, 4-methylhexanoic acid, 5-methylhexanoic acid, 2,2-dimethylpentane Acid, 2-ethylpentanoic acid, 3-ethylpentanoic acid, 2-ethylhexanoic acid, 2-methylheptanoic acid, 3-methylheptanoic acid, 4-methylheptanoic acid, 5-methylheptanoic acid, 6-methylheptanoic acid, Examples thereof include 2,2-dimethylhexanoic acid and 3,5-dimethylhexanoic acid. These monocarboxylic acids having 1 or more and 8 or less carbon atoms may be used alone or in combination of two or more.
Examples of the dicarboxylic acid having 2 or more and 8 or less carbon atoms include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, and suberic acid. These dicarboxylic acids having 2 or more and 8 or less carbon atoms may be used alone or in combination of two or more.
The amount of at least one of the monocarboxylic acid having 1 or more and 8 or less carbon atoms and the dicarboxylic acid having 2 or more and 8 or less carbon atoms is, for example, 1.5 mol with respect to the total amount of 1 mol of Zr ion and Ti ion.

Examples of water include distilled water, ion-exchanged water and the like. The amount of water added is, for example, 1 mol with respect to 1 mol of the total amount of Zr ions and Ti ions.

In the first embodiment, a PZT precursor solution prepared by mixing and reacting a Pb solution and a first Ti—Zr solution prepared by a partial hydrolysis method is used.
As a result, the piezoelectricity and ferroelectricity of the obtained piezoelectric element 1 are superior to those using the Ti—Zr solution which has not been prepared by the partial hydrolysis method. It is presumed that this is mainly due to the uniform composition distribution of the obtained piezoelectric element 1 in the thickness direction.
Specifically, a molecular design for forming a metal-oxygen bond in a PZT precursor solution was realized by reaction control in an organic solvent (partial hydrolysis method of PZT precursor using a chemical modification control method). ..
FIG. 2 is a diagram for explaining a partial hydrolysis reaction between titanium alkoxide, zirconium alkoxide, and acetic acid as a partial stabilizer. As shown in FIG. 2, the reaction control of the B site of the perovskite structure by the chemical modification control method forms a side chain group that is preferentially hydrolyzed by steric hindrance X due to chelation of acetic acid, and has a high degree of polymerization and homogeneity. High Ti-Zr solution is synthesized. By mixing and reacting the Ti—Zr solution having a high degree of polymerization and high homogeneity with the Pb solution, a PZT precursor having a small composition change can be obtained. Therefore, it is presumed that the composition distribution of the obtained piezoelectric element 1 in the thickness direction becomes uniform.
Further, conventionally, in the CSD method, it has been necessary to crystallization the PZT-based ceramics by firing the PZT precursor at a temperature of 600 ° C. or higher (hereinafter referred to as “second crystallization temperature”). On the other hand, in the first embodiment, the PZT precursor solution containing the first Ti—Zr solution prepared by the partial hydrolysis method and the LNO layer 12a in which the LNO is highly oriented in the (100) plane direction are used. It is considered that the PZT-based ceramic film can be crystallized even if the PZT precursor is fired at a second crystallization temperature lower than the conventional one.

(1.2.2.2) Second coating step In the second coating step, the PZT precursor solution is applied to the surface S12 of the LNO layer 12a. As a result, a PZT coating film is obtained. The PZT coating film contains a lead atom, a titanium atom, a zirconium atom, a first organic solvent, and a second organic solvent. The PZT coating film is an example of the third film according to claim 8. The first organic solvent and the second organic solvent are examples of the third organic solvent in claim 8.
The method for applying the PZT precursor solution is not particularly limited, and examples thereof include a spin coating method, a dip coating method, and a spray coating method.

(1.2.2.3) Second drying step In the second drying step, the PZT coating film is dried. Thereby, the water content in the PZT coating film and the residual solvent can be removed. The drying temperature is preferably more than 100 ° C and less than 200 ° C. When the drying temperature is within the above range, it is possible to suppress the residual water content in the obtained PZT film.

(1.2.2.4) Second calcining step In the second calcining step, the PZT coating film is calcined. This makes it possible to prevent the organic component from remaining in the obtained PZT coating film. The calcination temperature is preferably 200 ° C. or higher and lower than 400 ° C.

(1.2.2.5) Second firing step In the second firing step, the PZT coating film is rapidly heated using a rapid heating (RTA) furnace to maintain the second crystallization temperature, and the PZT is maintained. Crystallize the ceramics.

The rate of temperature rise is preferably 3.3 ° C./sec or higher, and preferably 10 ° C./sec or higher. When the rate of temperature rise is 3.3 ° C./sec or more, the piezoelectricity and ferroelectricity of the obtained piezoelectric element 1 are more excellent.

The second crystallization temperature is preferably 450 ° C. or higher and 600 ° C. or lower. Further, in order to sufficiently promote the crystallization of the PZT-based ceramics, the holding time of the second crystallization temperature is preferably 1 minute or more.

The desired film thickness of the PZT layer 13a can be obtained, for example, by repeating this cycle a plurality of times, with the second coating step, the second drying step, the second calcining step, and the second firing step as one cycle. In the first embodiment, the PZT layer 13a having a film thickness of 0.15 μm or more can be formed per cycle.

(12.3) Second Electrode Layer Forming Step In the second electrode layer forming step, the second electrode layer 14 is formed on the surface of the piezoelectric layer 13.
The method for forming the second electrode layer 14 is not particularly limited, and examples thereof include an ion beam vapor deposition method, a resistance heating vapor deposition method, and a sputtering method.

(2) Second Embodiment Next, with reference to FIG. 3, a method for manufacturing the piezoelectric element 1 and the piezoelectric element 1 according to the second embodiment of the present disclosure will be described. FIG. 3 is a cross-sectional view of the piezoelectric element 1 according to the second embodiment of the present disclosure.

(2.1) Piezoelectric Element The piezoelectric element 1 according to the second embodiment has a first electrode layer 12 having a conductor layer 12b and a piezoelectric layer 13 having a base layer 13b. It is different from the piezoelectric element 2 according to the embodiment.

As shown in FIG. 3, the piezoelectric element 1 according to the second embodiment includes a substrate 11, a first electrode layer 12, a piezoelectric layer 13, and a second electrode layer 14.

(2.1.1) First Electrode Layer In the second embodiment, the first electrode layer 12 has an LNO layer 12a and a conductor layer 12b. In the first electrode layer 12, the LNO layer 12a is located closest to the piezoelectric layer 13. Therefore, the piezoelectric layer 13 is laminated on the surface S12 of the LNO layer 12a.

Examples of the material of the conductor layer 12b include the same materials as those exemplified as the material of the second electrode layer 14. The film thickness of the conductor layer 12b may be appropriately adjusted according to the intended use of the piezoelectric element 1, and is preferably 0.1 μm or more and 0.4 μm or less.

(2.1.2) Piezoelectric layer In the second embodiment, the piezoelectric layer 13 has a PZT layer 13a and a base layer 13b. In the piezoelectric layer 13, the base layer 13b is located closest to the first electrode layer 12. Therefore, the base layer 13b is laminated on the surface S12 of the LNO layer 12a.

The base layer 13b is made of lead titanate-based ceramics.
Lead titanate-based ceramics are mainly composed of ceramics represented by the general formula Pb (Zr _x Ti _1-x ) O ₃ (0 ≦ x <0.4) (hereinafter referred to as “PT”). The main component means a component having a ratio of 80% by mass or more to all the components constituting the lead titanate-based ceramics.
The ratio (Zr / Ti) of the zirconium atom to the titanium atom of the lead titanate ceramic is preferably 0% (0/100) or more and 43% (30/70) or less, more preferably 0% (0%) in terms of molar ratio. 0/100) More than 25% (20/80).

Lead titanate-based ceramics include not only PT but also ceramics containing PT as a main component and a small amount of at least one metal selected from the group consisting of Sr, Nb, and Al added, lead magnesium niobium (PMN), and the like. It may contain ceramics containing at least one of lead titanate (PZN).

(2.2) Method for Manufacturing Piezoelectric Element In the method for manufacturing the piezoelectric element 1 according to the second embodiment, the first electrode layer forming step includes a conductor layer forming step, and the piezoelectric forming step is a base layer. It differs from the method for manufacturing the piezoelectric element 1 according to the first embodiment in that it includes a forming step.

The method for manufacturing the piezoelectric element 1 according to the second embodiment includes a first electrode layer forming step, a piezoelectric layer forming step, and a second electrode layer forming step. The first electrode layer forming step, the piezoelectric layer forming step, and the second electrode layer forming step are executed in this order.

(2.2.1) First Electrode Layer Forming Step In the second embodiment, the first electrode layer forming step includes a conductor layer forming step, a first solution preparation step, a first coating step, and a first drying. It has a step, a first calcining step, and a first firing step. The conductor layer forming step, the first solution preparation step, the first coating step, the first drying step, the first calcining step, and the first firing step are executed in this order. As a result, the first electrode layer 12 in which the conductor layer 12b and the LNO layer 12a are laminated in this order is formed on the surface of the substrate 11.

(2.2.1.1) Conductor layer forming step In the conductor layer forming step, the conductor layer 12b is formed on the surface of the substrate 11.
The method for forming the conductor layer 12b is not particularly limited, and examples thereof include an ion beam vapor deposition method, a resistance heating vapor deposition method, and a sputtering method.

In each of the first coating step, the first drying step, the first calcining step, and the first firing step according to the second embodiment, the LNO precursor solution is applied to the surface of the conductor layer 12b in the first coating step. Other than coating, it is carried out in the same manner as in the first embodiment.

(2.2.2) Piezoelectric layer forming step In the second embodiment, the piezoelectric layer forming step includes a third solution preparation step, a third drying step, a third calcination step, and a third main firing step. A second solution preparation step, a second drying step, a second calcination step, and a second main firing step are included. The third solution preparation step, the third drying step, the third calcining step, the third firing step, the second solution preparing step, the second drying step, the second calcining step, and the second firing step are in this order. Is executed by. As a result, the base layer 13b and the PZT layer 13a are laminated in this order on the surface S12 of the LNO layer 12a.

(2.2.2.1) Third solution preparation step In the third solution preparation step, the Pb solution and the second Ti—Zr solution are mixed to prepare a PT precursor solution as a raw material for the base layer 13b.

When mixing the Pb solution and the second Ti—Zr solution, the amount of the Pb component added is 15 mol with respect to the stoichiometric composition (Pb (Zr _x Ti _1-x ) O ₃ (0 ≦ x <0.4)). % To 20 mol% is preferable. This makes it possible to make up for the shortage of the Pb component due to volatilization in the third firing step.

The Pb solution is obtained in the same manner as in the second solution preparation step of the first embodiment.

In the second embodiment, the second Ti—Zr solution is prepared by a partial hydrolysis method. Specifically, at least one of a second titanium alkoxide compound, a third organic solvent, a monocarboxylic acid having 1 or more and 8 or less carbon atoms and a dicarboxylic acid having 2 or more and 8 or less carbon atoms (partial stabilizer) is added. The second mixed solution is prepared, and water is added to the second mixed solution for hydrolysis. A second zirconium alkoxide compound may be added when preparing the second mixed solution.

..
When the second titanium alkoxide compound and the second zirconium alkoxide compound are mixed in the second Ti—Zr solution, the ratio of the zirconium atom to the titanium atom (Zr / Ti) is preferably 0% (0/100) in terms of molar ratio. It is 43% (30/70) or less, more preferably more than 0% (0/100) and less than 25% (20/80).

Examples of the second titanium alkoxide compound include compounds similar to the compounds exemplified as the first titanium alkoxide compound of the first embodiment. These second titanium alkoxide compounds may be used alone or in combination of two or more. The second titanium alkoxide compound may be the same as or different from the first titanium alkoxide compound.
Examples of the second zirconium alkoxide compound include compounds similar to the compounds exemplified as the second zirconium alkoxide compound of the first embodiment. These second zirconium alkoxide compounds may be used alone or in combination of two or more. The second zirconium alkoxide compound may be the same as or different from the first zirconium alkoxide compound.
Examples of the third organic solvent include ethanol, xylene, butanol and the like. These third organic solvents may be used alone or in combination of two or more. The third organic solvent may be the same as or different from the second organic solvent.
Examples of the monocarboxylic acid having 1 or more and 8 or less carbon atoms in the PT precursor solution include the same compounds as those exemplified as the monocarboxylic acid having 1 or more and 8 or less carbon atoms in the first embodiment. These monocarboxylic acids having 1 or more and 8 or less carbon atoms may be used alone or in combination of two or more. The monocarboxylic acid having 1 or more and 8 or less carbon atoms in the PT precursor solution may be the same as or different from the monocarboxylic acid having 1 or more and 8 or less carbon atoms in the PZT precursor solution.
Examples of the dicarboxylic acid having 2 or more and 8 or less carbon atoms in the PT precursor solution include the same compounds as those exemplified as the dicarboxylic acid having 2 or more and 8 or less carbon atoms in the first embodiment. These dicarboxylic acids having 2 or more and 8 or less carbon atoms may be used alone or in combination of two or more. The dicarboxylic acid having 2 or more and 8 or less carbon atoms in the PT precursor solution may be the same as or different from the dicarboxylic acid having 2 or more and 8 or less carbon atoms in the PZT precursor solution.
The amount of at least one of the monocarboxylic acid having 1 or more and 8 or less carbon atoms and the dicarboxylic acid having 2 or more and 8 or less carbon atoms is, for example, 1 with respect to 1 mol of the total amount of Zr ions and Ti ions in the second mixed solution. It is .5 mol.

(2.2.2.2) Third coating step In the third coating step, the PT precursor solution is applied to the surface S12 of the LNO layer 12a. As a result, a PT coating film is obtained. The PT coating film contains a lead atom, a titanium atom, a first organic solvent, and a third organic solvent, and further contains a zirconium atom, if necessary. The PT coating film is an example of the second film according to claim 5.
The method for applying the LNO precursor solution is not particularly limited, and examples thereof include a spin coating method, a dip coating method, and a spray coating method.

Here, as the Zr content of the PT precursor coating film increases, it is necessary to raise the third crystallization temperature for crystallizing lead titanate-based ceramics. Further, when the content of Zr in the obtained piezoelectric layer 13 is large, the piezoelectric element 1 having more excellent piezoelectricity and ferroelectricity can be obtained. Therefore, the ratio of the zirconium atom to the titanium atom (Zr / Ti) of the PT coating film is preferably more than 0% (0/100) and less than 25% (20/80) in terms of molar ratio. As a result, the piezoelectric element 1 having excellent piezoelectricity and ferroelectricity can be obtained while keeping the third crystallization temperature low.
The ratio of zirconium atom to titanium atom (Zr / Ti) is within the above range. For the PT coating film, the ratio of zirconium atom to titanium atom in the second Ti—Zr solution (Zr / Ti) is 0% (0%) in molar ratio. / 100) Obtained by adjusting to more than 25% (20/80).

(2.2.2.2) Third drying step In the third drying step, the PT coating film is dried. Thereby, the water content and the residual solvent in the PT coating film can be removed. The drying temperature is preferably more than 100 ° C and less than 200 ° C. When the drying temperature is within the above range, it is possible to prevent moisture from remaining in the obtained PT coating film.

(2.2.2.4) Third calcination step In the third calcination step, the PT coating film is tentatively baked. This makes it possible to prevent the organic component from remaining in the obtained PT coating film. The calcination temperature is preferably 200 ° C. or higher and lower than 400 ° C.

(2.2.2.5) Third firing step In the third firing step, the PT coating film is rapidly heated using a rapid heating (RTA) furnace to maintain the third crystallization temperature, and the PT is maintained. Crystallize ceramics. As a result, the base layer 13b is formed on the surface S12 of the LNO layer 12a.

The rate of temperature rise is preferably 3.3 ° C./sec or higher, and preferably 10 ° C./sec or higher. When the rate of temperature rise is 3.3 ° C./sec or more, the piezoelectricity and ferroelectricity of the obtained piezoelectric element 1 are more excellent.

The third crystallization temperature is preferably 450 ° C. or higher and 600 ° C. or lower. Further, in order to sufficiently promote the crystallization of the PT-based ceramics, the holding time of the third crystallization temperature is preferably 5 minutes or more.

In the second embodiment, in the second solution preparation step, the second coating step, the second drying step, the second calcining step, and the second firing step, each of the second coating step is carried out by lowering the PZT precursor solution. It is carried out in the same manner as in the first embodiment except that it is applied to the surface of the formation layer 13b.
As described above, in the second embodiment, the PZT layer 13a is formed on the surface of the base layer 13b. Therefore, even if the PZT body solution is fired at a second crystallization temperature lower than the conventional one, the PZT-based ceramics can be crystallized.

In the second embodiment, the desired film thickness of the piezoelectric layer 13 is, for example, a second coating step, a second drying step, a second calcining step, and a second firing step as one cycle, and a plurality of these cycles. Obtained by repeating the process.

(2.2.3) Second Electrode Layer Forming Step In the second embodiment, the second electrode layer forming step is executed in the same manner as in the first embodiment.

Hereinafter, embodiments according to the present invention will be described in detail with reference to Examples. The present invention is not limited to the description of these examples.

[Preparation of base material]
As the base material 11, a glass substrate and a silicon substrate were prepared.

[Preparation of LNO precursor solution]
As the LNO precursor solution, an LNO (A) precursor solution and an LNO (B) precursor solution were prepared as follows. The organic solvent of the LNO (A) precursor solution and the LNO (B) precursor solution are different.

[Preparation of LNO (A) precursor solution]
Lanthanum Nitrate Hexhydrate (La (NO ₃ ) _{3.6H 2} O) Weigh 20 parts by mass in a beaker and dry at 150 ° C. for 1 hour or more to remove the hydrate. Got Next, after cooling the first dried product to room temperature, 90 parts by mass of ethanol and 10 parts by mass of 2-methoxyethanol were added to the first dried product, and the mixture was stirred at room temperature for 3 hours to dissolve lanthanum nitrate to dissolve the solution. I got A.
Nickel acetate tetrahydrate ((CH ₃ COO) ₂ Ni · 4H ₂ O) 20 parts by mass is weighed in a first separable flask, dried at 150 ° C. for 1 hour to remove hydrate, and then 200. A second dried product was obtained by drying at ° C. for 1 hour for a total of 2 hours. Next, 90 parts by mass of ethanol, 5 parts by mass of 2-methoxyethanol and 5 parts by mass of 2-aminoethanol were added to the second dried product, and the mixture was stirred at 110 ° C. for 30 minutes to obtain a solution B.
After cooling the solution B to room temperature, the solution A was put into a first separable flask containing the solution B and stirred at room temperature for 3 hours to obtain an LNO (A) precursor solution.

[Preparation of LNO (B) precursor solution]
20 parts by mass of lanthanum nitrate hexahydrate was weighed in a beaker and dried at 150 ° C. for 1 hour or more to obtain a third dried product. Then, after cooling the third dried product to room temperature, 100 parts by mass of ethanol was added to the third dried product, and the mixture was stirred at room temperature for 3 hours to dissolve lanthanum nitrate to obtain a solution C.
20 parts by mass of nickel acetate tetrahydrate was weighed in a second separable flask and dried at 150 ° C. for 1 hour to remove the hydrate, and then dried at 200 ° C. for 1 hour for a total of 2 hours. 4 Dried product was obtained. Then, 100 parts by mass of ethanol was added to the fourth dried product, and the mixture was stirred at 110 ° C. for 30 minutes to obtain a solution D.
After cooling the solution D to room temperature, the solution C was put into a second separable flask containing the solution D and stirred at room temperature for 3 hours to obtain an LNO (B) precursor solution.

[Preparation of PZT precursor solution]
As the PZT precursor solution, the first PZT (53/47) precursor solution, the first PZT (30/70) precursor solution, the PT precursor solution, the second PZT (53/47) precursor solution, and the second The first PZT (30/70) precursor solution was prepared as follows.
The first PZT (53/47) precursor solution, the first PZT (30/70) precursor solution, and the PT precursor solution differ in the content of zirconium in the solution.
The content of zirconium in the second PZT (53/47) precursor solution and the second PZT (30/70) precursor solution are different.
Each of the first PZT (53/47) precursor solution, the first PZT (30/70) precursor solution, and the PT precursor solution contains a partial stabilizer (acetic acid) as a raw material thereof, whereas the second PZT (acetic acid) is contained. Each of the 53/47) precursor solution and the second PZT (30/70) precursor solution does not contain a partial stabilizer in its raw material.

[Preparation of 1st PZT (53/47) precursor solution]
Lead acetate (II) trihydrate ((CH ₃ COO) ₂ Pb · 3H ₂ O) was weighed in a third separable flask and dried at 150 ° C. for 3 hours to remove the hydrate. 5 dried product was obtained. Then, absolute ethanol was added to the fifth dried product, and the mixture was heated and stirred at 50 ° C. for 2 hours while flowing ammonia gas to prepare a Pb solution.
The Zr-Ti precursor solution was prepared by the partial hydrolysis method. Specifically, zirconium-n-propoxide (Zr (OC ₃ H ₇ ) ₄ ) and titanium tetraisopropoxide (((CH ₃ ) ₂ CHO) ₄ Ti) are weighed in a fourth separable flask and anhydrous. Ethanol was added to dissolve the mixture, and the mixture was refluxed at 78 ° C. for 2 hours, acetic acid as a partial stabilizer was added, and the mixture was refluxed at 78 ° C. for 1 hour to obtain a solution E. The mixing ratio of zirconium-n-propoxide and titanium tetraisopropoxide was (53/47) in terms of the molar ratio of (Zr / Ti).
Then, the solution E was transferred into a cooler, stirred at 5 ° C. for 30 minutes, distilled water was added, and a partial hydrolysis reaction was carried out for 1 hour to prepare a Zr—Ti precursor solution. The amount of acetic acid added was 1.5 mol with respect to 1 mol of the total amount of Zr ions and Ti ions in the solution E. The amount of distilled water added was 1 mol with respect to 1 mol of the total amount of Zr ions and Ti ions in the solution E.
Then, the Pb solution and the Zr—Ti precursor solution were mixed and reacted, and stirred at 5 ° C. for 16 hours in a cooler to obtain a first PZT (53/47) precursor solution. The mixing ratio of the Pb solution and the Zr-Ti precursor solution was such that the Pb component was 20 mol% excessive with respect to the stoichiometric composition (Pb (Zr _{0.53 ,} Ti _0.47 ) O3).

[Preparation of 1st PZT (30/70) precursor solution]
The mixing ratio of zirconium-n-propoxide and titanium tetraisopropoxide was (30/70) in a molar ratio of (Zr / Ti), and the (1st PZT (53/47) precursor solution) was used. The first PZT (30/70) precursor solution was obtained in the same manner as in (Preparation).

[Preparation of PT precursor solution]
A PT precursor solution was obtained in the same manner as in (Preparation of 1st PZT (53/47) precursor solution) except that zirconium-n-propoxide was not used.

[Preparation of 2nd PZT (53/47) precursor solution]
The second PZT (53/47) precursor solution was prepared in the same manner as in (Preparation of the first PZT (53/47) precursor solution) except that acetic acid as a partial stabilizer was not added to the Zr-Ti precursor solution. Obtained.

[Preparation of 2nd PZT (30/70) precursor solution]
The mixing ratio of zirconium-n-propoxide and titanium tetraisopropoxide was set to 43% (30/70) in terms of the molar ratio of (Zr / Ti), and a partial stabilizer was added to the Zr-Ti precursor solution. A second PZT (30/70) precursor solution was obtained in the same manner as in (Preparation of the first PZT (53/47) precursor solution) except that acetic acid was not added.

(Example 1)
[First electrode layer forming step]
[LNO layer forming step]
The LNO (A) precursor solution was applied to the surface of the glass substrate by the spin coating method to obtain an LNO (A) coating film. The conditions for spin coating were a rotation speed of 2500 rpm and 30 seconds.
Then, in an oxygen atmosphere, the LNO (A) coating film was dried at 150 ° C. for 10 minutes, then heated from 150 ° C. to 350 ° C. and calcined at 350 ° C. for 10 minutes.
Then, using RTA, the temperature was raised from 350 ° C. to 550 ° C. at a heating rate of 40 ° C./sec, and main firing was performed at 550 ° C. for 15 minutes to obtain an LNO thin film on the surface of the glass substrate.
Similar to the method for forming the obtained LNO thin film, the work of applying the LNO (A) precursor solution by the spin coating method, drying, calcining, and main firing as one cycle is performed on the obtained LNO thin film 3 times. Repeated times.
As a result, a four-layer LNO thin film was obtained as the LNO layer 12a on the surface of the substrate 11.

[Piezoelectric layer forming process]
[Underground layer forming process]
A PZT (30/70) precursor solution was applied to the surface S12 of the LNO layer 12a by a spin coating method to obtain a PZT (30/70) coating film. The conditions for spin coating were a rotation speed of 2500 rpm and 30 seconds.
Then, in an oxygen atmosphere, the PZT (30/70) coating film was dried at 150 ° C. for 10 minutes, heated from 150 ° C. to 420 ° C., and calcined at 420 ° C. for 10 minutes.
Then, using RTA, the temperature was raised from 420 ° C. to 550 ° C. at a heating rate of 3.3 ° C./sec, and main firing was performed at 550 ° C. for 15 minutes on the surface S12 of the LNO layer 12a as the base layer 13b. A PZT (30/70) film was obtained.

[PZT layer forming step]
The first PZT (53/47) precursor solution was applied to the surface of the obtained PZT (30/70) thin film by a spin coating method to obtain a first PZT (53/47) coating film. The conditions for spin coating were a rotation speed of 2500 rpm and 30 seconds.
Then, in an oxygen atmosphere, the first PZT (53/47) coating film was dried at 150 ° C. for 10 minutes, then heated from 150 ° C. to 420 ° C. and calcined at 420 ° C. for 10 minutes.
Then, using RTA, the temperature was raised from 420 ° C. to 550 ° C. at a heating rate of 3.3 ° C./sec, and main firing was performed at 550 ° C. for 15 minutes on the surface of the 1PZT (30/70) thin film. (53/47) A thin film was obtained.
Similar to the method for forming the obtained first PZT (53/47) film, the work of applying, drying, calcining and main firing of the first PZT (53/47) precursor solution by the spin coating method is performed in one cycle. , Repeated 3 times on the obtained PZT (53/47) thin film.
As a result, a piezoelectric one layer of PZT (30/70) thin film as the base layer 13b and four layers of PZT (53/47) thin film as the PZT layer 13a are laminated in this order on the surface S12 of the LNO layer 12. Body layer 13 was obtained.

[Second electrode layer forming step]
An upper electrode layer made of Au was obtained on the surface of the PZT layer 13 by an ion beam vapor deposition method.

As described above, a piezoelectric element was obtained.

(Example 2)
A piezoelectric element was obtained in the same manner as in Example 1 except that the following (1) was different.
(1): In the LNO layer forming step, the temperature rise rate of RTA was set to 20 ° C./sec.

(Example 3)
A piezoelectric element was obtained in the same manner as in Example 1 except that the following (2) was different.
(2): In the LNO layer forming step, the LNO (B) precursor solution was used instead of the LNO (A) precursor solution.

(Example 4)
A piezoelectric element was obtained in the same manner as in Example 1 except that the following (1) and (2) were different.
(1): In the LNO layer forming step, the temperature rise rate of RTA was set to 20 ° C./sec. (2): In the LNO layer forming step, the LNO (B) precursor solution was used instead of the LNO (A) precursor solution. Was used

(Example 5)
A piezoelectric element was obtained in the same manner as in Example 1 except that the following (3) was different.
(3): In the PZT layer forming step, a PT precursor solution was used instead of the first PZT (30/70) precursor solution.

(Example 6)
A piezoelectric element was obtained in the same manner as in Example 1 except that the following (1) and (3) were different.
(1): In the LNO layer forming step, the temperature rise rate of RTA was set to 20 ° C./sec. (3): In the PZT layer forming step, the PT precursor was used instead of the first PZT (30/70) precursor solution. Using the solution

(Example 7)
A piezoelectric element was obtained in the same manner as in Example 1 except that the following (2) and (3) were different.
(2): The LNO (B) precursor solution was used instead of the LNO (A) precursor solution in the LNO layer forming step. (3): The first PZT (30/70) precursor in the PZT layer forming step. Using PT precursor solution instead of solution

(Example 8)
A piezoelectric element was obtained in the same manner as in Example 1 except that the following (1) to (3) were different.
(1): In the LNO layer forming step, the temperature rise rate of RTA was set to 20 ° C./sec. (2): In the LNO layer forming step, the LNO (B) precursor solution was used instead of the LNO (A) precursor solution. (3): In the PZT layer forming step, a PT precursor solution was used instead of the first PZT (30/70) precursor solution.

(Example 9)
A piezoelectric element was obtained in the same manner as in Example 1 except that the following (1) and (4) were different.
(1): In the LNO layer forming step, the temperature rise rate of RTA was set to 20 ° C./sec. (4): In the PZT layer forming step, instead of the first PZT (30/70) precursor solution, the first PZT ( 53/47) Precursor solution was used

(Example 10)
A piezoelectric element was obtained in the same manner as in Example 1 except that the following (5) was different.
(5): In the PZT layer forming step, the second PZT (53/47) precursor solution is used instead of the first PZT (53/47) precursor solution, and the first PZT (30/70) precursor solution is used instead of the first PZT (30/70) precursor solution. Using 2PZT (30/70) precursor solution

(Comparative Example 1)
A piezoelectric element was obtained in the same manner as in Example 1 except that the following (6) was different.
(6): In the LNO layer forming step, the temperature rise rate of RTA was set to 3.3 ° C./sec.

(Comparative Example 2)
A piezoelectric element was obtained in the same manner as in Example 1 except that the following (2) and (6) were different.
(2): In the LNO layer forming step, the LNO (B) precursor solution was used instead of the LNO (A) precursor solution. (6): In the LNO layer forming step, the temperature rise rate of RTA was 3.3. ℃ / sec

(Comparative Example 3)
A piezoelectric element was obtained in the same manner as in Example 1 except that the following (7) was different.
(7): In the LNO layer forming step, the main firing was performed at 400 ° C instead of 550 ° C.

(Comparative Example 4)
A piezoelectric element was obtained in the same manner as in Example 1 except that the following (1), (2), and (7) were different.
(1): In the LNO layer forming step, the temperature rise rate of RTA was set to 20 ° C./sec. (2): In the LNO layer forming step, the LNO (B) precursor solution was used instead of the LNO (A) precursor solution. (7): In the LNO layer forming step, the main firing was performed at 400 ° C instead of 550 ° C.

(Comparative Example 5)
A piezoelectric element was obtained in the same manner as in Example 1 except that the following (4) and (8) to (10) were different.
(4): In the PZT layer forming step, the first PZT (53/47) precursor solution was used instead of the first PZT (30/70) precursor solution. (8): As the substrate 11, instead of the glass substrate. (9): In the LNO layer forming step, the heating rate was changed from 40 ° C./sec to 30 ° C./sec, and the main firing conditions were changed from 15 minutes at 550 ° C to 5 minutes at 750 ° C. What was changed (10): In the PZT layer forming step, the drying condition was changed from 150 ° C. to 115 ° C., the calcination condition was changed from 420 ° C. to 350 ° C., and the main firing condition was changed to 550 ° C. for 15 minutes at 650 ° C. 5 What I replaced with minutes

(Measurement of piezoelectric elements, etc.)
The piezoelectric constant d ₃₃ and the residual polarization (Pr: Remanent Polarization) of the piezoelectric elements of Examples 1 to 10 and Comparative Examples 1 to 5 were measured by the following measuring methods and the like. Table 1 shows the measurement results of the obtained residual polarization Pr and the piezoelectric constant d ₃₃ .
In Table 3, in the measurement results of the residual polarization Pr and the piezoelectric constant d ₃₃ , “0” indicates that the piezoelectric constant d ₃₃ and the residual polarization Pr could not be measured due to poor crystallinity.

(Measurement of piezoelectric constant d ₃₃ )
The minute displacement when a voltage was applied to the first electrode layer and the second electrode layer was measured by a scanning probe microscope (SPM), and the piezoelectric constant d ₃₃ was obtained.
A piezoelectric element having a piezoelectric constant d ₃₃ of 40 (pm / V) or more was evaluated as a piezoelectric element having excellent piezoelectricity.

(Measurement of residual polarization Pr)
A Sawyer tower circuit was used for the measurement of the residual polarization Pr. That is, a triangular wave voltage was applied to the piezoelectric element, the polarization generated by the voltage further generated a surface charge, the amount of the surface charge was measured, and the residual polarization Pr was obtained by dividing by the electrode area.
A piezoelectric element having a residual polarization Pr of 15 (μC / cm ² ) or more was evaluated as a piezoelectric element having excellent ferroelectricity.

In Examples 1 to 10, the LNO coating film containing lanthanum nitrate, nickel acetate, and ethanol was heated to a first crystallization temperature of 450 ° C. or higher and 600 ° C. or lower at a heating rate of 10 ° C./sec or higher. The first crystallization temperature was maintained to form the LNO layer. Therefore, the piezoelectric elements of Examples 1 to 10 have a piezoelectric constant d ₃₃ of 40 (pm / V) or more and a residual polarization Pr of 15 (μC / cm ² ) or more. As a result, it was found that in Examples 1 to 10, a piezoelectric element having excellent piezoelectricity and ferroelectricity can be produced at a lower temperature by the CSD method.

Further, as is clear from the comparison between Example 1 and Example 3 and the comparison between Example 2 and Example 4, ethanol, 2-methoxyethanol and 2-aminoethanol are used in the solvent of the LNO precursor solution. In Examples 1 and 2 containing only ethanol, the piezoelectric constant d ₃₃ of the piezoelectric element was higher than in Examples 3 and 4 containing only ethanol. As a result, when the solvent of the LNO precursor solution further contains 2-methoxyethanol and 2-aminoethanol in addition to the organic solvent having 1 or more and 4 or less carbon atoms, a piezoelectric element having better piezoelectricity can be produced. all right.

Further, as is clear from the comparison between Example 1 and Example 5, the comparison between Example 2 and Example 6, the comparison between Example 3 and Example 7, and the comparison between Example 4 and Example 8. In addition, Examples 1 to 4 in which the ratio of the zirconium atom to the titanium atom in the PT coating film is 43% (30/70) in molar ratio are higher than those in Examples 5 to 8 in which the ratio is 0%. , The piezoelectric constant d ₃₃ and the residual polarization Pr of the piezoelectric element were higher. As a result, it was found that when the PT coating film contains zirconium, a piezoelectric element having more excellent piezoelectricity and ferroelectricity can be produced.

Further, as is clear from the comparison between Example 2 and Example 7, Example 2 in which the piezoelectric layer 13 has the base layer 13b is higher than that in Example 7 in which the piezoelectric layer 13 does not have the base layer 13b. The piezoelectric constant d ₃₃ and the residual polarization Pr of the piezoelectric element of the piezoelectric element were higher. As a result, it was found that the piezoelectric layer 13 having the base layer 13b makes it possible to manufacture a piezoelectric element having more excellent piezoelectricity and ferroelectricity.

Further, as is clear from the comparison between Example 1 and Example 10, Example 1 using the Zr-Ti precursor solution prepared by the partial hydrolysis method is Zr- not prepared by the partial hydrolysis method. The piezoelectric constant d ₃₃ and the residual polarization Pr of the piezoelectric element of the piezoelectric element were higher than those of Example 10 using the Ti precursor solution. As a result, it was found that a piezoelectric device having more excellent piezoelectricity and ferroelectricity can be produced by using the Zr-Ti precursor solution prepared by the partial hydrolysis method.

On the other hand, in Comparative Example 1 and Comparative Example 2, the temperature of the LNO coating film containing lanthanum nitrate, nickel acetate and ethanol was raised to 550 ° C at a heating rate of less than 10 ° C / sec. Therefore, in the piezoelectric elements of Comparative Example 1 and Comparative Example 2, the piezoelectric constant d ₃₃ was less than 40 (pm / V) and the residual polarization Pr was less than 15 (μC / cm ² ). As a result, in Comparative Example 1 and Comparative Example 2, it was found that the piezoelectric element having excellent piezoelectricity and ferroelectricity could not be manufactured at a lower temperature by the CSD method.

In Comparative Example 3 and Comparative Example 4, the LNO coating film containing lanthanum nitrate, nickel acetate, and ethanol was kept at a first crystallization temperature of less than 450 ° C. to form an LNO layer. Therefore, in the piezoelectric elements of Comparative Example 1 and Comparative Example 2, the piezoelectric constant d ₃₃ was less than 40 (pm / V) and the residual polarization Pr was less than 15 (μC / cm ² ). As a result, in Comparative Example 3 and Comparative Example 4, it was found that the piezoelectric element having excellent piezoelectricity and ferroelectricity could not be manufactured at a lower temperature by the CSD method.

In Comparative Example 5, the first crystallization temperature of the LNO coating film was 750 ° C. Therefore, the piezoelectric element of Comparative Example 5 is a very excellent piezoelectric element having a piezoelectric constant d ₃₃ of 40 (pm / V) or more and a residual polarization Pr of 15 (μC / cm ² ) or more. However (Pr = 38 μC / cm ² , d ₃₃ = 500 pm / V), the substrate 11 was exposed to a high temperature of 750 ° C. As a result, in Comparative Example 5, it was found that a piezoelectric element having excellent piezoelectricity and ferroelectricity could be produced by the CSD method, but the substrate 11 was exposed to a high temperature of 650 ° C. or higher.

Further, as is clear from the comparison between Comparative Example 1 and Example 1 and the comparison between Comparative Example 2 and Example 2, if the LNO layer 12a is not preferentially oriented on the surface of the substrate 11 in the (100) plane, partial water addition is performed. It was found that even when the PZT precursor solution containing the Zr-Ti precursor solution prepared by the decomposition method was used, the obtained piezoelectric element did not exhibit excellent piezoelectricity and ferroelectricity.

FIG. 4 is an X-ray diffraction pattern diagram of the LNO layer 12a obtained in Example 1, Example 2, Comparative Example 1, and Comparative Example 5. As shown in FIG. 4, in Example 1 having a heating rate of 40 ° C./sec, Comparative Example 5 having a heating rate of 30 ° C./sec, and Example 2 having a heating rate of 20 ° C./sec, the LNO layer. Was found to be preferentially oriented to the (100) plane. On the other hand, in Comparative Example 1 at a heating rate of 3.3 ° C./sec, it was found that the LNO layer was not preferentially oriented toward the (100) plane. From these results, it was found that the LNO layer can be preferentially oriented toward the (100) plane by setting the temperature rise rate to 10 ° C./sec or more in the LNO layer forming step.

FIG. 5 is a diagram showing measurement results of the characteristics (PE hysteresis loop) of the piezoelectric element obtained in Examples 1 and 2. FIG. 6 is a diagram showing measurement results of the characteristic PE hysteresis loop of the piezoelectric element obtained in Examples 3 and 4.
As shown in FIG. 5, the LNO layer 12a using the LNO (A) precursor solution capable of maintaining a stable molecular structure up to a high temperature is used as the orientation control layer and the first electrode layer 12 of the PZT layer 13a to rapidly raise the temperature. In Example 1 (40 ° C./sec), a very large residual polarization value (ferroelectricity) and relatively good piezoelectricity (d ₃₃ = 170 pm / V) were obtained.
As shown in FIG. 6, in Examples 3 and 4, the temperature of the LNO layer 12a using the body solution of LNO (B) was rapidly increased by using the LNO layer 12a as the orientation control layer and the first electrode layer 12 of the PZT layer 13a. It was also found that relatively good ferroelectricity and piezoelectricity can be obtained. However, it was found that by using the LNO (A) precursor solution, it is possible to fabricate a piezoelectric device having higher performance than using the LNO (B) precursor solution.

FIG. 7 shows the distance from the surface S12 of the LNO layer 12a in the thickness direction of the PZT layer 13a obtained by line-analyzing the cross section of the PZT layer 13a in the thickness direction of Reference Example 1 along the thickness direction of the PZT layer 13a with STEM-EDX. It is a graph which shows the fluctuation of each of the concentration ratio (Ti concentration / Pb concentration) and the concentration ratio (Zr concentration / Pb concentration) with respect to. Specifically, FIG. 7 shows the concentration ratio (Ti concentration / Pb concentration) and the concentration in the 100 nm section from a position 0.41 μm away from the surface S12 of the LNO layer 12 on the second electrode layer 14 side in the thickness direction of the PZT layer 13a. The fluctuation range of each ratio (Zr concentration / Pb concentration) is shown. Further, the piezoelectric device of Reference Example 1 was produced by using a PZT precursor solution containing a first Ti—Zr solution prepared by a partial hydrolysis method according to Comparative Example 5. Similar to Comparative Example 5, the piezoelectric element of Reference Example 1 has a piezoelectric constant d ₃₃ of 40 (pm / V) or more and a residual polarization Pr of 15 (μC / cm ² ) or more, and is extremely excellent. It is a piezoelectric element. 0.41 μm is an example of the first distance. The position 0.41 μm away from the surface S12 of the LNO layer 12 on the side of the second electrode layer 14 in the thickness direction of the PZT layer 13a is an example of the first position. A position 0.51 μm away from the surface S12 of the LNO layer 12 on the side of the second electrode layer 14 in the thickness direction of the PZT layer 13a is an example of the second position.

FIG. 8 shows the distance from the surface S12 of the LNO layer 12 in the thickness direction of the PZT layer 13a obtained by line-analyzing the cross section of the PZT layer 13a in the thickness direction of Reference Example 2 along the thickness direction of the PZT layer 13a with STEM-EDX. It is a graph which shows the fluctuation of each of the concentration ratio (Ti concentration / Pb concentration) and the concentration ratio (Zr concentration / Pb concentration) with respect to. Specifically, FIG. 8 shows the concentration ratio (Ti concentration / Pb concentration) and the concentration in the 100 nm section from a position 0.34 μm away from the surface S12 of the LNO layer 12 on the second electrode layer 14 side in the thickness direction of the PZT layer 13a. The fluctuation range of each ratio (Zr concentration / Pb concentration) is shown. Further, the piezoelectric element of Reference Example 2 was produced in the same manner as in Reference Example 1 except that a PZT precursor solution not prepared by the partial hydrolysis method was used. Unlike the reference example 1, the piezoelectric element of the reference example 2 had a piezoelectric constant d ₃₃ of less than 40 (pm / V) and a residual polarization Pr of less than 15 (μC / cm ² ).

In Reference Example 1 using the PZT precursor solution prepared by the partial hydrolysis method, very excellent ferroelectricity and piezoelectricity were shown.
Further, as shown in FIG. 7, the concentration ratio (Ti concentration / Pb concentration) of the first position separated by 0.41 μm from the surface S12 of the LNO layer 12 to the second electrode layer 14 side in the thickness direction of the PZT layer 13a is determined. It was 0.270. A second position 0.51 μm away from the surface S12 of the LNO layer 12 on the second electrode layer 14 side in the thickness direction of the PZT layer 13a (100 nm away from the first position on the second electrode layer 14 side in the thickness direction of the PZT layer 13a). The concentration ratio (Ti concentration / Pb concentration) of the position) was 0.275. That is, the concentration ratio (Ti concentration / Pb concentration) changes only 0.005 (variation rate A is about 1%) in the fluctuation range between 100 nm from the first position to the second position. In other words, as shown by the composition gradient CA, it was found that the concentration ratio (Ti concentration / Pb concentration) was uniform over 100 nm.
Further, in Reference Example 1, the concentration ratio (Zr concentration / Pb concentration) at the first position was 0.190. The concentration ratio (Zr concentration / Pb concentration) at the second position was 0.175. That is, the concentration ratio (Zr concentration / Pb concentration) changes only 0.015 (variation rate B is about 8%) in the fluctuation range between 100 nm from the first position to the second position. In other words, as shown by the composition gradient CB, it was found that the concentration ratio (Zr concentration / Pb concentration) was uniform over 100 nm.
From the above, it was found that the composition distribution of the PZT layer 13a of Reference Example 1 using the PZT precursor solution prepared by the partial hydrolysis method was uniform in the thickness direction.

On the other hand, in Reference Example 2 using the PZT precursor solution not prepared by the partial hydrolysis method, as shown in FIG. 8, the second electrode layer in the thickness direction from the surface S12 of the LNO layer 12 to the PZT layer 13a. The concentration ratio (Ti concentration / Pb concentration) at the first position, which was 0.34 μm away from the 14 side, was about 0.300. A second position 0.44 μm away from the surface S12 of the LNO layer 12 on the second electrode layer 14 side in the thickness direction of the PZT layer 13a (100 nm away from the first position on the second electrode layer 14 side in the thickness direction of the PZT layer 13a). The concentration ratio (Ti concentration / Pb concentration) of the position) was 0.225. That is, the concentration ratio (Ti concentration / Pb concentration) varies greatly between 100 nm from the first position to the second position, with a fluctuation range of about 0.075 (variation rate A is about 25%). In other words, as shown by the composition gradient CA, it was found that the uniformity of the concentration ratio (Ti concentration / Pb concentration) was low over 100 nm.
Further, in Reference Example 2, the concentration ratio (Zr concentration / Pb concentration) at the first position was about 0.150. The concentration ratio (Zr concentration / Pb concentration) at the second position was about 0.200. That is, the concentration ratio (Zr concentration / Pb concentration) varies greatly between 100 nm from the first position to the second position, with a fluctuation range of about 0.050 (variation rate B is about 25%). In other words, as shown by the composition gradient CB, it was found that the uniformity of the concentration ratio (Zr concentration / Pb concentration) was low over 100 nm.
From the above, it was found that in Reference Example 1 using the PZT precursor solution prepared by the partial hydrolysis method, the uniformity of the composition distribution in the thickness direction is very high, so that the ferroelectricity and the piezoelectricity are high. ..

1 Piezoelectric element 11 Substrate 12 First electrode layer 13 Piezoelectric layer 13a PZT layer 13b Underlayer layer 14 Second electrode layer

Claims (9)

A method for manufacturing a piezoelectric element including a substrate, a first electrode layer, a piezoelectric layer, and a second electrode layer in this order.
The first electrode layer has an LNO layer made of lanthanum nickelate ceramics.
The piezoelectric layer has lead zirconate titanate-based ceramics and is formed on the surface of the LNO layer.
The first film containing a lanthanum atom, a nickel atom, and an organic solvent having 1 or more and 4 or less carbon atoms is heated to a temperature of 450 ° C. or higher and 600 ° C. or lower at a heating rate of 10 ° C./sec or higher to maintain the temperature. A method for manufacturing a piezoelectric element, which comprises a step of forming an LNO layer for forming the LNO layer.
The method for manufacturing a piezoelectric device according to claim 1, wherein the organic solvent having 1 or more and 4 or less carbon atoms contains alcohol.
The method for manufacturing a piezoelectric element according to claim 1 or 2, wherein the temperature rising rate is 30 ° C./sec or more.
The method for producing a piezoelectric element according to any one of claims 1 to 3, wherein the first film contains at least one of 2-methoxyethanol and 2-aminoethanol.
The piezoelectric layer includes a base layer formed on the surface of the LNO layer and a PZT layer made of the lead zirconate titanate ceramics formed on the surface of the base layer.
A step of forming a base layer on the surface of the LNO layer by heating a second film containing a lead atom, a titanium atom, and a first organic solvent at 450 ° C. or higher and 600 ° C. or lower.
A PZT layer forming step of heating a third film containing a lead atom, a titanium atom, a zirconium atom, and a second organic solvent at 450 ° C. or higher and 600 ° C. or lower to form the PZT layer on the surface of the base layer. The method for manufacturing a piezoelectric element according to any one of claims 1 to 4, which comprises.
The second film further contains a zirconium atom and
The method for manufacturing a piezoelectric element according to claim 5, wherein the ratio of the zirconium atom to the titanium atom of the second film is more than 0% and less than 25% in terms of molar ratio.
In the PZT layer forming step,
A first solution is prepared by adding a titanium alkoxide compound, a zirconium alkoxide compound, a third organic solvent, and at least one of a monocarboxylic acid having 1 to 8 carbon atoms and a dicarboxylic acid having 2 to 8 carbon atoms. death,
After adding water to the first solution, a second solution containing a lead atom and a fourth organic solvent was further added to prepare a third solution.
The method for manufacturing a piezoelectric element according to claim 5 or 6, wherein the third solution is applied to the surface of the base layer to form the third film.
The piezoelectric layer includes a PZT layer made of the lead zirconate titanate ceramics formed on the surface of the LNO layer.
A first solution is prepared by adding a titanium alkoxide compound, a zirconium alkoxide compound, a first organic solvent, and at least one of a monocarboxylic acid having 1 or more and 8 or less carbon atoms and a dicarboxylic acid having 2 or more and 8 or less carbon atoms. death,
After adding water to the first solution, a second solution containing a lead atom and a second organic solvent is further added to prepare a third solution.
The third solution is applied to the surface of the LNO layer to form a third film containing a lead atom, a titanium atom, a zirconium atom, and a third organic solvent.
The invention according to any one of claims 1 to 4, further comprising a PZT layer forming step of heating the third film at 450 ° C. or higher and 600 ° C. or lower to form the PZT layer on the surface of the LNO layer. Manufacturing method of piezoelectric element.
The substrate, the first electrode layer, the piezoelectric layer, and the second electrode layer are provided in this order.
The first electrode layer has an LNO layer made of lanthanum nickelate ceramics.
The piezoelectric layer has a PZT layer made of lead zirconate titanate ceramics.
The volatility A represented by the following equation (1) is 10% or less.
A piezoelectric element having a volatility B represented by the following equation (2) of 10% or less.

In the formula (1), [ _AX ] is obtained by analyzing the cross section of the PZT layer in the thickness direction with a scanning transmission electron microscope (STEM-EDX) along the thickness direction from the surface of the LNO layer. The concentration ratio (Ti concentration / Pb concentration) of the first position separated by the first distance is shown on the second electrode layer side in the thickness direction, and [ _{AX + 100} ] indicates the thickness direction from the first position in which the analysis was performed. The concentration ratio (Ti concentration / Pb concentration) of the second position separated by 100 nm is shown on the second electrode layer side of the above.
In the formula (2), [ _BX ] indicates the concentration ratio (Zr concentration / Pb concentration) of the first position of the analysis, and [ _{BX + 100} ] indicates the concentration ratio of the second position of the analysis. The concentration ratio (Zr concentration / Pb concentration) is shown. )

Images