JP2007204341A - Piezoelectric material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel piezoelectric material friendly to environment and excellent in piezoelectric characteristics. <P>SOLUTION: The piezoelectric material is expressed by general formula (1): ((K,Na)<SB>1/2</SB>Bi<SB>1/2</SB>)(Ni<SB>1/3</SB>Nb<SB>2/3</SB>)O<SB>3</SB>. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a piezoelectric material.

Inkjet printers are known as printers that enable high image quality and high-speed printing. The ink jet printer includes an ink jet recording head having a cavity whose internal volume changes. As a head actuator in such an ink jet recording head, a piezoelectric element using a piezoelectric film represented by Pb (Zr, Ti) O ₃ (PZT) has been conventionally used (for example, JP-A-2001-223404). No. publication). However, since PZT and the like contain lead (Pb), there is a very environmental problem.
JP 2001-223404 A

  An object of the present invention is to provide a novel piezoelectric material that is environmentally friendly and excellent in piezoelectric characteristics.

The piezoelectric material according to the present invention is
It is represented by the following general formula (1).

((K, Na) _1/2 Bi _1/2 ) (Ni _1/3 Nb _2/3 ) O ₃ (1)
This piezoelectric material is extremely useful because it does not contain lead (Pb) which causes environmental problems. Furthermore, this piezoelectric material can obtain a good piezoelectric characteristic, for example, a sufficient lattice strain amount, while being lead-free.

In the piezoelectric material according to the present invention,
The composition ratio of potassium (K) in the general formula (1) can be larger than the composition ratio of sodium (Na).

In the piezoelectric material according to the present invention,
It can be represented by the following general formula (2) in which a part of niobium (Nb) in the general formula (1) is replaced by tantalum (Ta).

((K, Na) _1/2 Bi _1/2 ) (Ni _1/3 (Nb, Ta) _2/3 ) O ₃ (2)
In the piezoelectric material according to the present invention,
The composition ratio of niobium (Nb) in the general formula (2) can be larger than the composition ratio of tantalum (Ta).

In the piezoelectric material according to the present invention,
It can have a rhombohedral structure.

In the piezoelectric material according to the present invention,
It can have a monoclinic structure.

In the piezoelectric material according to the present invention,
It can be pseudo-cubic and (100) -oriented.

  In the present invention, for example, “oriented to (100)” means that all crystals are oriented to (100), and most crystals are oriented to (100). And the case where the remaining non-oriented crystal is oriented to (110) or the like. That is, “orientation at (100)” can also be referred to as “priority orientation at (100)”. This is the same in the present invention when, for example, “oriented to (110)”.

In the piezoelectric material according to the present invention,
It can be pseudo-cubic and (110) -oriented.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

1. 1. First embodiment 1.1. First, the piezoelectric material according to the first embodiment will be described. The piezoelectric material according to the present embodiment is represented by the following general formula (1).

((K, Na) _1/2 Bi _1/2 ) (Ni _1/3 Nb _2/3 ) O ₃ (1)
The piezoelectric material according to this embodiment has a perovskite structure. The piezoelectric material preferably has a rhombohedral structure or a monoclinic structure. In addition, the piezoelectric material is preferably pseudo cubic and (100) or (110) oriented. A piezoelectric material having a rhombohedral structure or a monoclinic structure and oriented in a pseudo cubic (100) or (110) can have good piezoelectric properties. In addition, the valence of each element in the piezoelectric material is desirably K for +1, Na for +1, Bi for +3, Ni for +2, Nb for +5, and O for -2. Thereby, the piezoelectric material can be charge neutral.

  Moreover, it is desirable that the composition ratio of potassium (K) in the general formula (1) is larger than the composition ratio of sodium (Na). For example, the composition ratio of potassium: the composition ratio of sodium = K: Na = 0.8: 0.2. The piezoelectric material in this case can be represented by the following formula (1 ′).

((K _0.8 Na _0.2 ) _1/2 Bi _1/2 ) (Ni _1/3 Nb _2/3 ) O ₃ (1 ′)
The piezoelectric material according to the present embodiment can be represented by the following general formula (2) in which a part of niobium (Nb) in the general formula (1) is replaced with tantalum (Ta).

((K, Na) _1/2 Bi _1/2 ) (Ni _1/3 (Nb, Ta) _2/3 ) O ₃ (2)
As for the valence of each element in the piezoelectric material, Ta is +5, and the other elements are preferably the same as those desired for the piezoelectric material of the general formula (1). Thereby, the piezoelectric material can be charge neutral.

  In addition, the composition ratio of niobium (Nb) in the general formula (2) is preferably larger than the composition ratio of tantalum (Ta). For example, the composition ratio of niobium: the composition ratio of tantalum = Nb: Ta = 0.9: 0.1. The piezoelectric material in this case can be represented by the following formula (2 ′).

((K _, Na) _1/2 Bi _1/2 ) (Ni _1/3 (Nb _0.9 Ta _0.1 ) _2/3 ) O ₃ (2 ′)
1.2. The piezoelectric material according to the present embodiment is extremely useful because it does not contain lead (Pb) that causes environmental problems. Furthermore, the piezoelectric material according to the present embodiment can obtain good piezoelectric characteristics, for example, a sufficient lattice strain amount, while being lead-free. This has been confirmed in an experimental example according to a second embodiment to be described later.

2. Second Embodiment 2.1. Next, the piezoelectric element 100 according to the second embodiment will be described. FIG. 1 is a cross-sectional view schematically showing an example of a piezoelectric element 100 including a piezoelectric film 6 made of a piezoelectric material according to the present invention.

  The piezoelectric element 100 is formed on the first conductive layer (hereinafter also referred to as “lower electrode”) 4, the lower electrode 4, the piezoelectric film 6 made of the piezoelectric material, and the first film formed on the piezoelectric film 6. 2 conductive layers (hereinafter also referred to as “upper electrodes”) 7. The piezoelectric element 100 can include a base 2 and an elastic film 3 formed on the base 2. The lower electrode 4 can be formed on the elastic film 3. Note that the piezoelectric element 100 may not have at least one of the base 2 and the elastic film 3.

  As the substrate 2, for example, a (110) -oriented single crystal silicon substrate can be used, and is not particularly limited. The substrate 2 may be a single substrate or a laminate in which other layers are laminated on the substrate. The elastic film 3 can be applied as the elastic film 55 in the ink jet recording head 50 (see FIG. 3). As the elastic film 3, for example, a film in which silicon oxide and zirconium oxide are laminated in this order can be used, and the elastic film 3 is not particularly limited. The film thickness of the elastic film 3 is, for example, about 1 μm.

The lower electrode 4 is one electrode for applying a voltage to the piezoelectric film 6. The lower electrode 4 can be formed in the same planar shape as the piezoelectric film 6 and the upper electrode 7, for example. The film thickness of the lower electrode 4 is, for example, 100 nm to 300 nm. The lower electrode 4 is not particularly limited, for example, be used as the platinum (Pt) conductive oxide having a perovskite structure on a metal film such as a (e.g. LaNiO _3, etc. SrRuO ₃₎ film formed by laminating a it can. For example, the film made of the conductive oxide is desirably pseudo cubic and oriented in (100) or (110) like the piezoelectric film 6 made of the piezoelectric material. Since the conductive oxide film is oriented in this way, the piezoelectric film 6 formed on the conductive oxide film can easily take over the orientation of the conductive oxide film.

  The piezoelectric film 6 is formed from the piezoelectric material according to the first embodiment. That is, the piezoelectric film 6 is composed of the piezoelectric material. The film thickness of the piezoelectric film 6 is not particularly limited, but is, for example, 200 nm to 1.5 μm.

The upper electrode 7 is the other electrode for applying a voltage to the piezoelectric film 6. As the upper electrode 7, for example, a single layer of platinum (Pt), iridium (Ir), iridium oxide (IrOx), a conductive oxide having a perovskite structure (for example, LaNiO ₃ , SrRuO _3, etc.) A laminate can be used and is not particularly limited. The film thickness of the upper electrode 7 is, for example, 100 nm to 200 nm.

  2.2. Next, a method for manufacturing the piezoelectric element 100 according to this embodiment will be described with reference to FIG.

  (A) First, the elastic film 3 is formed on the substrate 2. The elastic film 3 can be formed by, for example, a thermal oxidation method, a chemical vapor deposition (CVD) method, a sputtering method, a vapor deposition method, or the like.

  (B) Next, the lower electrode 4 is formed on the elastic film 3. The lower electrode 4 can be formed, for example, by sputtering, spin coating, CVD, laser ablation, or the like.

  (C) Next, the piezoelectric film 6 made of the piezoelectric material according to the first embodiment is formed on the lower electrode 4. The piezoelectric film 6 can be formed using, for example, a sol-gel method, a MOD (Metal Organic Decomposition) method, or the like. The method for forming the piezoelectric film 6 when using the sol-gel method or the MOD method is specifically as follows.

  First, a precursor solution for forming the piezoelectric film 6 is applied onto the lower electrode 4 by using, for example, a spin coating method (precursor solution applying step). For the precursor solution, for example, an organometallic compound containing each of the constituent metals of the piezoelectric material to be the piezoelectric film 6 is mixed so that each constituent metal has a desired molar ratio, and the mixture is mixed with an organic solvent such as alcohol. It can be prepared by dissolving or dispersing using As an organometallic compound containing a constituent metal of the piezoelectric material, for example, a metal alkoxide, an organic acid salt, a β-diketone complex, or the like can be used. Examples of the organometallic compound containing the constituent metal of the piezoelectric material (for example, K, Na, Bi, Ni, Nb, Ta in the case of the piezoelectric material of the general formula (2)) include the following.

  Examples of the organometallic compound containing potassium (K) include potassium ethoxide. Examples of the organometallic compound containing sodium (Na) include sodium ethoxide. Examples of the organometallic compound containing bismuth (Bi) include bismuth isopropoxide. Examples of the organometallic compound containing nickel (Ni) include nickel acetylacetonate. Examples of the organometallic compound containing niobium (Nb) include niobium ethoxide. Examples of the organometallic compound containing tantalum (Ta) include tantalum ethoxide. The organometallic compound containing the constituent metal of the piezoelectric material is not limited to these.

  Various additives such as a stabilizer can be added to the precursor solution as necessary. In the case where hydrolysis / polycondensation is caused in the precursor solution, an acid or a base can be added as a catalyst together with an appropriate amount of water to the precursor solution. Examples of the additive to the precursor solution include diethanolamine and acetic acid.

  For example, the spin rotation speed in spin coating is initially set to about 500 rpm, and then the rotation speed can be increased to about 2000 rpm so that coating unevenness does not occur.

  Next, heat treatment is performed at a temperature, for example, about 10 ° C. higher than the boiling point of the solvent used in the precursor solution using a hot plate or the like in an air atmosphere (dry heat treatment step).

  Next, in order to decompose and remove the ligand of the organometallic compound used in the precursor solution, heat treatment is performed, for example, at about 300 ° C. to 400 ° C. using a hot plate or the like in the atmosphere (degreasing heat treatment step).

  In addition, a series of processes of the precursor solution coating process, the drying heat treatment process, and the degreasing heat treatment process described above can be repeated as appropriate according to the desired film thickness.

  Next, the piezoelectric film 6 is obtained by performing a crystallization annealing, that is, a baking process for crystallization. The crystallization annealing can be performed at about 600 ° C. to 750 ° C. in an oxygen atmosphere by, for example, RTA (Rapid Thermal Annealing).

  The piezoelectric film 6 can be formed not only by a liquid phase method such as a sol-gel method or a MOD method, but also by a vapor phase method such as a laser ablation method or a sputtering method.

  (D) Next, the upper electrode 7 is formed on the piezoelectric film 6. The upper electrode 7 can be formed by, for example, sputtering, spin coating, chemical vapor deposition (CVD), laser ablation, or the like.

  (E) Next, post-annealing can be performed as necessary. Thereby, a good interface between the piezoelectric film 6 and the upper and lower electrodes can be formed, and the crystallinity of the piezoelectric film 6 can be improved. Post annealing can be performed in an oxygen atmosphere by, for example, RTA.

  Through the above steps, the piezoelectric element 100 according to this embodiment can be manufactured.

  2.3. In the piezoelectric element 100 according to the present embodiment, the piezoelectric film 6 is composed of the piezoelectric material according to the first embodiment. As described above, this piezoelectric material can have good piezoelectric characteristics while being lead-free. Therefore, according to this embodiment, it is possible to provide the piezoelectric element 100 that is environmentally friendly and excellent in piezoelectric characteristics.

  2.4. Next, experimental examples will be described.

  A sample of the piezoelectric element 100 according to this embodiment was obtained by the following method.

First, an elastic film 3 was obtained by laminating a SiO ₂ film with a thickness of 500 nm and a ZrO ₂ film with a thickness of 500 nm on a (110) oriented silicon substrate (base 2). The SiO ₂ film was formed by thermal oxidation, and the ZrO ₂ film was formed by sputtering. Next, as a lower electrode 4, a Pt film having a thickness of 200 nm and a LaNiO ₃ film having a thickness of 100 nm were sequentially stacked on the ZrO ₂ film by sputtering. The power for sputtering the Pt film and the LaNiO ₃ film was 200 W. The orientation of the obtained LaNiO ₃ film was confirmed to be pseudo cubic and (100) oriented.

Next, a piezoelectric film 6 made of the piezoelectric material according to the first embodiment was formed on the LaNiO ₃ film. The piezoelectric film 6 was obtained as follows.

  First, a precursor solution of a piezoelectric material represented by the following formula (a) was prepared as follows.

((K _0.8 Na _0.2 ) _1/2 Bi _1/2 ) (Ni _1/3 (Nb _0.9 Ta _0.1 ) _2/3 ) O ₃ (a)
First, reagents for organometallic compounds (potassium ethoxide, sodium ethoxide, bismuth isopropoxide, nickel acetylacetonate, niobium ethoxide, tantalum ethoxide) containing constituent metals of the piezoelectric material were prepared. Next, they were mixed so as to have a molar ratio corresponding to the composition of the piezoelectric material, and dissolved (dispersed) in butyl cellosolve. Furthermore, diethanolamine was added as a stabilizer for this solution. In this way, a precursor solution was prepared.

  Next, this precursor solution was applied onto the lower electrode 4 by a spin coat method (precursor solution application step). Next, it was heat-treated (dried) at a temperature about 10 ° C. higher than the boiling point of the solvent (about 170 ° C. in the case of butyl cellosolve) to remove the solvent and gel (dry heat treatment step). Next, by heating to about 400 ° C., organic components other than the solvent remaining in the film were decomposed / removed (degreasing heat treatment step) to form an amorphous film having a thickness of 100 nm. The above process was repeated 5 times. Next, crystallization was performed by heating at 600 ° C. for 1 minute in an oxygen atmosphere by RTA, thereby forming a piezoelectric film 6 having a thickness of 500 nm. It was confirmed that the crystal structure of the obtained piezoelectric film 6 was a rhombohedral structure or a monoclinic structure. The piezoelectric film 6 was confirmed to be pseudo cubic and (100) oriented. X-ray scattering and Raman scattering were used to identify the crystal structure and orientation of the piezoelectric film 6.

  Next, a Pt film having a thickness of 200 nm was formed as the upper electrode 7 on the piezoelectric film 6 by sputtering.

  A sample of the piezoelectric element 100 was obtained as described above. With respect to the piezoelectric film 6 of this sample, the strain amount of the lattice of the piezoelectric material when an electric field of 100 kV / cm was applied from the upper and lower electrodes was 0.06%, and good piezoelectric characteristics were confirmed. Note that the strain amount of the lattice was determined from θ-2θ measurement by electric field X-rays.

3. Third Embodiment 3.1. Next, the piezoelectric element 200 according to the third embodiment will be described. FIG. 2 is a cross-sectional view schematically showing an example of the piezoelectric element 200 including the piezoelectric film 6 made of the piezoelectric material according to the present invention. In addition, about the same member as the piezoelectric element 100 which concerns on 2nd Embodiment, the same code | symbol is attached | subjected and the detailed description is abbreviate | omitted.

  The piezoelectric element 200 is formed on the piezoelectric film 6 made of the piezoelectric material, a first conductive layer (hereinafter also referred to as “first electrode”) 40 formed on the piezoelectric film 6, and the piezoelectric film 6. And a second conductive layer (hereinafter also referred to as “second electrode”) 70. The piezoelectric element 200 can include a base 2 and a buffer layer 30 formed on the base 2. The piezoelectric film 6 can be formed on the buffer layer 30. Note that the piezoelectric element 200 may not include at least one of the base 2 and the buffer layer 30.

The buffer layer 30 can have a function of controlling the crystal orientation of the piezoelectric film 6. If the base 2 has this function, the buffer layer 30 may not be provided. As with the piezoelectric film 6 made of a piezoelectric material, the buffer layer 30 is preferably pseudo-cubic and oriented (100) or (110). Since the buffer layer 30 is thus oriented, the piezoelectric film 6 formed on the buffer layer 30 can easily take over the orientation of the buffer layer 30. As the buffer layer 30, for example, a conductive oxide having a perovskite structure (for example, LaNiO ₃ , SrRuO _3, or the like) can be used.

The first electrode 40 and the second electrode 70 are electrodes for applying a voltage to the piezoelectric film 6. As the first electrode 40 and the second electrode 70, for example, platinum (Pt), iridium (Ir), iridium oxide (IrOx), a conductive oxide having a perovskite structure (for example, LaNiO ₃ , SrRuO _3, etc.) A layer or a laminate thereof can be used, and is not particularly limited. The film thickness of the upper electrode 7 is, for example, 100 nm to 200 nm.

  3.2. Next, a method for manufacturing the piezoelectric element 200 according to this embodiment will be described with reference to FIG.

  (A) First, the buffer layer 30 is formed on the substrate 2. The buffer layer 30 can be formed by, for example, sputtering, spin coating, CVD, laser ablation, or the like.

  (B) Next, the piezoelectric film 6 is formed on the buffer layer 30. Since this process is the same as one manufacturing process of the piezoelectric element according to the second embodiment described above, detailed description thereof is omitted.

  (C) Next, the first electrode 40 and the second electrode 70 are formed on the piezoelectric film 6. The first electrode 40 and the second electrode 70 can be formed by, for example, a sputtering method, a spin coating method, a CVD method, a laser ablation method, or the like. The first electrode 40 and the second electrode 70 can be patterned by a known method.

  (D) Next, post-annealing can be performed as necessary. Since this process is the same as one manufacturing process of the piezoelectric element according to the second embodiment described above, detailed description thereof is omitted.

  Through the above steps, the piezoelectric element 200 according to this embodiment can be manufactured.

  3.3. According to the present embodiment, as in the second embodiment, it is possible to provide the piezoelectric element 200 that is environmentally friendly and excellent in piezoelectric characteristics.

4). Fourth Embodiment 4.1. Next, an example in which the piezoelectric element according to the present invention is applied to an ink jet recording head as a piezoelectric actuator will be described. The ink jet recording head can be applied to, for example, an ink jet printer. FIG. 3 is a side sectional view showing a schematic configuration of the ink jet recording head 50 according to the present embodiment, and FIG. 4 is an exploded perspective view of the ink jet recording head 50, which is upside down from a normally used state. It is shown in.

  As shown in FIGS. 3 and 4, the ink jet recording head 50 includes a head main body 57 and a piezoelectric portion 54 formed on the head main body 57. The piezoelectric unit 54 is configured by sequentially stacking the lower electrode 4, the piezoelectric film 6, and the upper electrode 7 in the piezoelectric element 100 illustrated in FIG. 1. 3 and 4, illustration of each layer of the piezoelectric portion 54 is omitted. In the ink jet recording head 50, the piezoelectric portion 54 functions as a piezoelectric actuator.

  The head body 57 includes a nozzle plate 51, an ink chamber base 52, and an elastic film 55. The ink chamber base 52 and the elastic film 55 are composed of the base 2 and the elastic film 3 in the piezoelectric element 100 shown in FIG. These are housed in a casing 56 to constitute an ink jet recording head 50.

  Each piezoelectric portion 54 is electrically connected to a piezoelectric element drive circuit (not shown) and is configured to operate (vibrate, deform) based on a signal from the piezoelectric element drive circuit. That is, each piezoelectric part 54 functions as a vibration source (head actuator). The elastic film 55 vibrates due to the vibration (deflection) of the piezoelectric portion 54 and functions to instantaneously increase the internal pressure of the cavity 521.

  4.2. The ink jet recording head 50 according to the present embodiment includes a piezoelectric element 100 that is environmentally friendly and has excellent piezoelectric characteristics. Therefore, according to the present embodiment, it is possible to provide an ink jet recording head 50 that is environmentally friendly, has high ink ejection capability, and has high density of nozzles.

  4.3. In the above description, an ink jet recording head that discharges ink has been described as an example. However, the present embodiment is intended for liquid ejecting heads and liquid ejecting apparatuses that use piezoelectric elements. Examples of the liquid ejecting head include a recording head used in an image recording apparatus such as a printer, a color material ejecting head used for manufacturing a color filter such as a liquid crystal display, an organic EL display, and an electrode formation such as an FED (surface emitting display). Examples thereof include an electrode material ejecting head used in manufacturing, a bioorganic matter ejecting head used in biochip manufacturing, and the like.

  5. Although the embodiments of the present invention have been described in detail as described above, those skilled in the art will readily understand that many modifications are possible without substantially departing from the novel matters and effects of the present invention. Accordingly, all such modifications are included in the scope of the present invention.

  For example, the piezoelectric element according to the present invention is not only applied to the above-described devices, but also various devices (for example, BAW (bulk acoustic wave) such as FBAR (film bulk acoustic resonator) type and SMR (solid mounted resonator) type. ) Filter, SAW (surface acoustic wave) filter, gyro sensor, ultrasonic motor, etc.). The piezoelectric element according to the present invention is excellent in piezoelectric characteristics and can be suitably applied to various applications.

Sectional drawing which shows the piezoelectric element which concerns on 2nd Embodiment. Sectional drawing which shows the piezoelectric element which concerns on 3rd Embodiment. 1 is a schematic configuration diagram of an ink jet recording head. FIG. 2 is an exploded perspective view of an ink jet recording head.

Explanation of symbols

2 substrate, 3 elastic film, 4 lower electrode, 6 piezoelectric film, 7 upper electrode, 30 buffer layer, 40 first electrode, 50 ink jet recording head, 51 nozzle plate, 52 ink chamber substrate, 54 piezoelectric section, 55 elasticity Membrane, 56 housing, 57 head body, 70 second electrode, 100 piezoelectric element, 200 piezoelectric element, 521 cavity

Claims (8)

A piezoelectric material represented by the following general formula (1).
((K, Na) _1/2 Bi _1/2 ) (Ni _1/3 Nb _2/3 ) O ₃ (1) In claim 1,
The piezoelectric material in which the composition ratio of potassium (K) in the general formula (1) is larger than the composition ratio of sodium (Na). In claim 1 or 2,
A piezoelectric material represented by the following general formula (2) in which a part of niobium (Nb) in the general formula (1) is replaced with tantalum (Ta).
((K, Na) _1/2 Bi _1/2 ) (Ni _1/3 (Nb, Ta) _2/3 ) O ₃ (2) In claim 3,
A piezoelectric material in which the composition ratio of niobium (Nb) in the general formula (2) is larger than the composition ratio of tantalum (Ta). In any one of Claims 1 thru | or 4,
A piezoelectric material having a rhombohedral structure. In any one of Claims 1 thru | or 4,
A piezoelectric material having a monoclinic structure. In any one of Claims 1 thru | or 6.
A piezoelectric material which is pseudo cubic and (100) oriented. In any one of Claims 1 thru | or 6.
Piezoelectric material which is pseudo-cubic and oriented in (110).

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