JP7034639B2 - Piezoelectric materials, piezo elements, and electronic devices - Google Patents

Description

The present invention relates to a piezoelectric material, and more particularly to a piezoelectric element using a piezoelectric material that does not contain lead. The present invention also relates to an electronic device using the piezoelectric element.

ABO type ₃ perovskite-type metal oxides such as lead-containing lead zirconate titanate (hereinafter referred to as "PZT") are typical piezoelectric materials. Piezoelectric elements having electrodes on the surface of the piezoelectric material are used in various piezoelectric devices and electronic devices such as actuators, oscillators, sensors and filters.

However, since PZT contains lead as an A-site element, the lead component in the discarded piezoelectric material may dissolve into the soil and harm the ecosystem, and the impact on the environment is regarded as a problem. Therefore, various lead-free piezoelectric materials (hereinafter referred to as "lead-free piezoelectric materials") have been studied.

A typical lead-free piezoelectric material that is currently being widely studied is a piezoelectric material containing potassium niobate. However, when synthesizing a piezoelectric material containing potassium, the hygroscopicity of the raw material (for example, potassium carbonate) powder is high, it is difficult to accurately weigh the raw material powder at a target molar ratio, and there is a difficulty in industrial production. In addition, the piezoelectric material containing potassium niobate (KNbO ₃ ) has deliquescent properties, and the piezoelectricity of the piezoelectric ceramics containing potassium niobate may deteriorate over time. Further, in the piezoelectric material containing potassium niobate, the successive phase transition temperature between the tetragonal crystal and the orthorhombic crystal may be in the operating temperature range of the piezoelectric device (for example, from 0 ° C. to 80 ° C.). Since the piezoelectricity fluctuates remarkably in the vicinity of the successive phase transition temperature, there is a problem that the performance of the piezoelectric device fluctuates remarkably depending on the operating temperature.

An example of a lead-free piezoelectric material is a solid solution of sodium niobate (NaNbO ₃ ) and barium titanate (BaTIO ₃ ) (hereinafter referred to as “NN-BT”). Since the NN-BT ceramics do not substantially contain potassium, which causes resistance to sintering and low moisture resistance, the piezoelectric characteristics hardly change with time. Further, even when NN-BT ceramics are used for a piezoelectric device, the performance may vary significantly depending on the operating temperature because there is no phase transition of the crystal structure in the operating temperature range of the device (for example, from 0 ° C to 80 ° C). It has the advantage of being almost nonexistent.

In the piezoelectric body, the piezoelectric constant for the displacement in the polarization direction when a charge is applied in the polarization direction is d ₃₃ , and the piezoelectric constant for the in-plane displacement of the piezoelectric body orthogonal to the displacement direction of the piezoelectric constant d ₃₃ is piezoelectric. The constant is expressed as d ₃₁ .

In Patent Document 1, a lead-free piezoelectric material (bismuth sodium titanate-based) having | d ₃₃ / d ₃₁ | of 3 or more is used for a specific piezoelectric element, so that it is unnecessary due to d ₃₁ as compared with PZT. There is a disclosure that various vibrations can be suppressed.

However, there is a problem that d ₃₃ of the bismuth sodium titanate-based piezoelectric material shown in Patent Document 1 stays at 80-160 pC / N and does not reach 200 pC / N of PZT.

On the other hand, Non-Patent Document 1 discloses a lead-free sodium niobate-barium titanate-calcium zirconate (NaNbO _{3-BaTIO 3 -} CaZrO ₃ ) composition system, in which d ₃₃ is used in a specific component ratio. It has been shown to exceed 200 pC / N.

Japanese Unexamined Patent Publication No. 2011-199206

Ruzhong Zuo et al., Applied Physics Letter, 2016, Vol. 109, pp. 022902

However, the dielectric loss tangent at room temperature in the composition of 0.875 (NaNbO ₃ ) -0.1 (BaTIO ₃ ) -0.025 (CaZrO ₃ ) showing a good piezoelectric constant in Non-Patent Document 1 exceeds 0.02. There is. If the dielectric loss tangent of the piezoelectric material is larger than 0.02, the power consumption when used as a piezoelectric element will be significantly increased, and the efficiency will be significantly reduced.

The present invention has been made to solve such a problem, and is NNBT-based non-lead piezoelectric, which does not contain lead and potassium, has a high value of | d ₃₃ / d ₃₁ |, and has a small dielectric loss tangent value. It provides the material. The present invention also provides a piezoelectric element using the piezoelectric material and an electronic device.

The piezoelectric material of the present invention that solves the above problems is
A piezoelectric material containing Na, Ba, Nb, Ti, Zr, Mn, and Ca and made of a perovskite-type oxide.
T indicating the molar ratio of the Ti to the Nb is 0.08 ≦ t ≦ 0.15.
Z indicating the molar ratio of the Zr to the Nb is 0.01 ≦ z ≦ 0.04,
Β indicating the molar ratio of Ba to Nb is 0.08 ≦ β ≦ 0.17.
Α indicating the molar ratio of the Na to the Nb is 0.95 ≦ α ≦ 1.03.
M indicating the molar ratio of Mn to Nb is 0.0005 ≦ m ≦ 0.0025, and the molar ratio of Ca to Zr is 0.97 or more and 1.03 or less .
| D ₃₃ / d ₃₁ | The value is 3.5 or more, and the dielectric loss tangent is less than 0.02 when an alternating voltage of 1 kHz is applied at room temperature .

The piezoelectric element according to the present invention is a piezoelectric element having a piezoelectric material portion and an electrode.
The piezoelectric material constituting the piezoelectric material portion is the above-mentioned piezoelectric material.

The electronic device according to the present invention is characterized by including the above-mentioned piezoelectric element.

According to the present invention, by adding an appropriate amount of the Mn component, it is possible to provide a novel piezoelectric material in which dielectric loss tangent is suppressed and the ratio of | d ₃₃ / d ₃₁ | is increased. Further, the present invention can provide a piezoelectric element using the piezoelectric material and an electronic device.

Further, since the piezoelectric ceramics of the present invention do not use lead and potassium, they have a small load on the environment and are excellent in terms of moisture resistance and storage stability.

It is a schematic diagram which shows one Embodiment of the structure of the piezoelectric element of this invention. It is sectional drawing which shows one Embodiment of the structure of the laminated type piezoelectric element of this invention. It is a schematic diagram which shows one Embodiment of the electronic device of this invention. It is a schematic diagram which shows one Embodiment of the electronic device of this invention. It is a schematic diagram which shows one Embodiment of the electronic device of this invention. It is a figure which shows the relationship between | d ₃₃ / d ₃₁ | value and Mn amount of dielectric loss tangent in the piezoelectric element of Examples 11 to 13 and Comparative Example 1 of this invention. It is a figure which shows the relationship with the Zr amount of | d ₃₃ / d ₃₁ | value in the piezoelectric element of Examples 21-23, 31-33 and Comparative Examples 21, 31 of this invention. It is a polarization-electric field hysteresis curve in the piezoelectric element of Examples 21-23 and Comparative Example 2 of this invention.

Hereinafter, embodiments for carrying out the present invention will be described.

The present invention provides a lead-free piezoelectric material having a basic structure of NN-BT and having a good mechanical quality coefficient and piezoelectricity. The piezoelectric material of the present invention can be used for various purposes such as capacitors, memories, and sensors by utilizing its characteristics as a dielectric.

The piezoelectric material of the present invention has the following features.
(Characteristic 1) Contains Na, Ba, Nb, Ti, Zr, and Mn.
(Characteristic 2) Consists of perovskite-type oxide.
(Characteristic 3) t indicating the molar ratio of Ti to Nb is 0.08 ≦ t ≦ 0.15.
(Characteristic 4) z indicating the molar ratio of Zr to Nb is 0.01 ≦ z ≦ 0.04.
(Characteristic 5) β indicating the molar ratio of Ba to Nb is 0.08 ≦ β ≦ 0.17.
(Characteristic 6) α indicating the molar ratio of Na to Nb is 0.95 ≦ α ≦ 1.03.
(Characteristic 7) m indicating the molar ratio of Mn to Nb is 0.0005 ≦ m ≦ 0.0025.
(Characteristic 8) More preferably, the piezoelectric material contains Ca of 0.97 or more and 1.03 or less in terms of molar ratio with respect to Zr.

Each of these features will be described in detail below.

(Feature 1)
The piezoelectric material of the present invention contains Na, Ba, Nb, Ti, Zr and Mn. More preferably, the piezoelectric material also contains Ca.

By simultaneously containing Na, Ba, Nb, Ti, and O as the main components of the piezoelectric material, the piezoelectric constant of the piezoelectric material becomes large, and each of them in the operating temperature range of the device (for example, from 0 ° C to 80 ° C). Fluctuations in characteristics can be reduced. In addition, since the piezoelectric material contains Ca, the piezoelectric constant d ₃₃ becomes even larger.

By containing a small amount of Zr and a small amount of Mn in addition to the main components of Na, Ba, Nb, Ti, and O, the piezoelectric material has a large | d ₃₃ / d ₃₁ | value of 3 or more. .. With such a configuration, the dielectric loss tangent becomes less than 0.02 (2%) when, for example, an alternating voltage of 1 kHz is applied at room temperature. When Ca is further contained, a piezoelectric material having a larger value of | d ₃₃ / d ₃₁ | with a value of 3.5 or more can be obtained.

Further, when the piezoelectric constant | d ₃₃ / d ₃₁ | is 4.0 or more, it is more preferable from the viewpoint of suppressing unnecessary vibration caused by d ₃₁ .

(Feature 2)
The piezoelectric material consists of a perovskite-type oxide. The same applies when the piezoelectric material contains Ca. Since the piezoelectric material is made of a perovskite-type oxide, the piezoelectric material of the present invention exhibits a large piezoelectric constant.

It is desirable that this crystal structure is a so-called main phase in which the perovskite-type structure occupies the majority of the whole, and more preferably it is a single phase consisting of only the perovskite-type structure. For example, if a large number of tungsten bronze type structures are mixed, the piezoelectric constant may be significantly lowered.

In the present invention, the perovskite-type metal oxide is a perovskite-type structure (perovskite) that is ideally a cubic structure as described in the 5th edition of the Iwanami Physics and Chemistry Dictionary (issued on February 20, 1998 by Iwanami Shoten). Refers to a metal oxide having a structure). Metal oxides with a perovskite-type structure are generally represented by the chemical formula of ABO ₃ . In perovskite-type metal oxides, the elements A and B occupy specific positions in the unit cell called A site and B site, respectively, in the form of ions. For example, in the case of a cubic unit cell, element A is located at the apex of the cube and element B is located at the center of the body. The O element occupies the face-centered position of the cube as an anion of oxygen. The A-site element of the cube is 12-coordinated, and the B-site element is 6-coordinated. When the elements A, B, and O are slightly coordinate-shifted from the symmetrical positions of the unit cell, the unit cell of the perovskite-type structure is distorted and becomes a crystal system such as tetragonal crystal, rhombohedral crystal, and orthorhombic crystal.

For example, in the case of a tetragonal crystal, the only four-fold rotation axis direction is defined as the c-axis, and the two crystal axes perpendicular to each other are defined as the a-axis and the b-axis. The length of each axial unit cell is represented by c, a, b (= a).

In the main components of the material of the present invention, Na and Ba are located at the A site and Nb, Ti and Zr are located at the B site, but the Na / Nb ratio is intentionally smaller than 1 and the Ba / Ti ratio is 1. It may be larger. Even if the amount ratio of A-site element, B-site element, and oxygen element in the entire metal oxide is not necessarily 1: 1: 3, the perovskite-type structure occupies 90% or more of the main phase of the present invention. Included in the range. More preferably, it is a single phase in which the oxide of the perovskite type structure occupies substantially all.

The fact that the oxide has a perovskite-type structure can be determined, for example, from the measurement results of X-ray diffraction and electron diffraction with respect to the piezoelectric material.

(Features 3, 5, 6)
By occupying the main elements other than oxygen of the piezoelectric material with Na, Ba, Nb, Ti, Zr, and Mn, the improvement of the value | d ₃₃ / d ₃₁ |, which is the aim of the present invention, can be obtained, and further, the dielectric loss tangent can be obtained. Sufficient inhibitory effect can be obtained. However, for the purpose of adjusting other physical properties of the piezoelectric material, other metal elements may be added as long as the effects of the present invention are not impaired.

Here, the main component constituting the piezoelectric material of the present invention is sodium niobate, which is an antiferroelectric material, to which barium titanate, which is a ferroelectric substance, is added. When t or β, which indicates the amount of barium titanate with respect to sodium niobate, becomes larger than 0.15 or 0.17, the Curie temperature drops significantly, for example, to 80 ° C. or lower. On the other hand, when t or β is less than 0.08, the piezoelectric constant and the mechanical strength decrease. Therefore, when 0.08 ≦ t ≦ 0.15 and 0.08 ≦ β ≦ 0.15, a high Curie temperature and good piezoelectricity can be obtained. Further, when 0.09 ≦ t ≦ 0.12 and 0.09 ≦ β ≦ 0.12, a Curie temperature of about 190 ° C. or higher and a piezoelectric constant of 50 pm / V or higher | d ₃₁ | are obtained. It is less likely that the piezoelectric performance will deteriorate due to heat in the device manufacturing process, which is more preferable.

The piezoelectric constant d ₃₁ is generally expressed as a negative value, but the absolute value is expressed below.

(Features 4, 7, 8)
In the piezoelectric material of the present invention, z, which indicates the molar ratio of Zr to Nb, contains Zr in the range of 0.01 ≦ z ≦ 0.04, that is, Zr contains 4 mol% or less of the elements occupying the B site. By occupying it, the dielectric constant at room temperature increases and the piezoelectric performance improves. As the amount of Zr increases, the c / a ratio of the perovskite structure decreases, and the anisotropy of the crystal structure changes.

Further, when the spontaneous polarization of the piezoelectric material of the present invention is pinned, Zr can reduce the pinning of the spontaneous polarization. When the pinning is reduced, the residual polarization value decreases or the coercive electric field decreases in the polarization-electric field hysteresis curve near saturation. When Zr exceeds 4 mol% of B site, the resistivity decreases.

When m indicating the molar ratio of Mn to Nb is in the range of 0.0005 ≦ m ≦ 0.0025 and the piezoelectric material contains Mn, resistivity, piezoelectric constant, electromechanical coupling coefficient, mechanical quality coefficient, Young's modulus The rate and density can be increased. In particular, by including Mn in the above range in the piezoelectric material of the present invention, an effect of suppressing dielectric loss tangent at room temperature and an effect of improving the value of | d ₃₃ / d ₃₁ | can be obtained as compared with the case where Mn is not contained.

The Mn is contained in the piezoelectric material and is present at the A site or B site of the perovskite type structure or at the grain boundary of the crystal grain of the perovskite type structure composed of Na, Ba, Nb, Ti, Zr and O.

When Mn is located at the A site, it has the effect of compensating for defects in the crystal structure.

Further, when Mn is located at the B site, a defective dipole is formed and an internal electric field is generated.

The effect of the present invention can be obtained regardless of where Mn is located. Mn may be contained in both the A site and the B site.

At least a part of Mn may be present at the grain boundaries. It is preferable that Mn existing at the grain boundary exists as an oxide. Since a part of Mn is unevenly present at the grain boundaries, effects such as suppression of pores, an increase in the mechanical quality coefficient, and an increase in Young's modulus can be expected. In addition, the presence of a part of Mn at the grain boundaries reduces the grain boundary friction, and it is expected that the material will become harder.

The distribution of Mn in the sample and the occupied sites in the crystal can also be evaluated by an electron microscope, energy-dispersed X-ray spectroscopy, X-ray diffraction, Raman scattering, and a transmission electron microscope.

When Mn is present only in the A site, the Mn ion is smaller than the Na ion or Ba ion, so that the volume of the unit cell is reduced.

When Zr is present only at the B site, the Zr ion is larger than the Nb ion or Ti ion, so that the volume of the unit cell increases.

When Ca is present only in the A site, the Ca ion is smaller than the Ba ion, so that the volume of the unit cell is reduced.

When the above states are realized at the same time, the above effects are superimposed and appear.

However, since the addition of excess Ca may significantly lower the Curie temperature and the successive phase transition temperature, it is preferable to contain Ca having a molar ratio of 0.97 or more and 1.03 or less with respect to Zr.

The volume of the unit cell can be calculated from the angle of each diffraction peak in the X-ray diffraction measurement.

As the amount of Zr increases, the c / a ratio of the perovskite structure decreases, and the anisotropy of the crystal structure changes. It is conceivable that the value of | d ₃₃ / d ₃₁ | becomes smaller as c / a becomes smaller, but in the material of the present invention, the value of | d ₃₃ / d ₃₁ | can be increased by adding Zr. It is considered that this is due to the ease of displacement of atoms in the twisting direction with respect to the c-axis.

By adding Ca in addition to Zr and Mn at the same time, the above effects appear in combination, and more | d ₃₃ / d ₃₁ | values can be expected to increase.

(Curie temperature)
The Curie temperature is a temperature at which the piezoelectricity of the piezoelectric material disappears above that temperature. In the present specification, the temperature at which the capacitance becomes maximum in the vicinity of the phase transition temperature of the ferroelectric phase and the normal dielectric phase is defined as the Curie temperature. For example, it can be obtained by measuring the capacitance at 1 kHz with an impedance analyzer (4194A manufactured by Keysight Technologies (formerly Agilent Technologies)) while changing the temperature of the piezoelectric material to which the electrode is attached.

When evaluating the Curie temperature with a single piezoelectric material having no electrode, an X-ray diffraction image of a sample obtained by crushing and powdering the piezoelectric material is measured, for example, in the range of room temperature to 300 ° C. and ferroelectricity. The temperature at which the phase transition from the sexual structure to the ferroelectric structure occurs can be regarded as the Curie temperature.

The Curie temperature of the piezoelectric material of the present invention is preferably 235 ° C. or higher and 400 ° C. or lower. When the Curie temperature of the piezoelectric material is 235 ° C. or higher, the piezoelectric constant of the piezoelectric material does not decrease even if a heating step such as a thermocompression bonding process of a resin is performed when processing the element after the piezoelectric material is polarized. Therefore, it is preferable. On the other hand, when the Curie temperature of the piezoelectric material is 400 ° C. or lower, the polarization treatment to the piezoelectric material becomes easy.

(Piezoelectric constant)
The piezoelectric constant is a quantity indicating the degree of displacement (extension, contraction, displacement) of the piezoelectric material when a voltage is applied to the piezoelectric material. For example, the piezoelectric constant d ₃₁ is proportional to the contraction (extension) displacement in the direction orthogonal to the polarization direction when a voltage is applied in the polarization direction of the piezoelectric material (usually the direction in which the voltage is applied during the polarization process). It is a coefficient, that is, the amount of displacement per unit voltage. Conversely, it can also be defined as the amount of charge induced when stress is applied to the material.

The piezoelectric constant of the piezoelectric material can be obtained by calculation from the measurement results of the resonance frequency and the antiresonance frequency obtained by using a commercially available impedance analyzer, based on the Japan Electronics and Information Technology Industries Association standard (JEITA EM-4501). Unless otherwise stated, the present specification is intended to measure piezoelectric constants at room temperature, for example, at 25 ° C. This measurement method is called a resonance-antiresonance method.

The piezoelectric constant can be calculated not only by the resonance-antiresonance method but also by measuring the displacement amount when a voltage is applied or measuring the induced charge amount when a stress is applied. From the viewpoint of good vibration characteristics, the piezoelectric constant d33 is preferably 200 pm / V or more.

(Ti, Nb ratio)
The molar ratio t of Ti to Nb contained in the piezoelectric material is preferably 0.08 ≦ t ≦ 0.15. When it is 0.08 or more, the crystallization of the piezoelectric material is promoted, and the mechanical strength and density required for mounting the piezoelectric material in an electronic device can be obtained. On the other hand, when t is 0.15 or less, the characteristics of sodium niobate, which is the main component, are emphasized, and a Curie temperature of 190 ° C. or higher and a piezoelectric constant of 50 pm / V or higher | d ₃₁ | can be obtained. A more preferable range of t is 0.09 ≦ t ≦ 0.12.

(Pb component, K component)
It is preferable that the total amount of the Pb component and the K component contained in the piezoelectric material is less than 1000 ppm.

More preferably, the Pb component contained in the piezoelectric material is less than 500 ppm, and the K component is less than 500 ppm. Even more preferably, the total of the Pb component and the K component is less than 500 ppm.

By suppressing the amount of the Pb component contained in the piezoelectric material of the present invention, the influence of the Pb component released into the environment when the piezoelectric material is left in water or soil can be reduced.

Suppressing the amount of the K component contained in the piezoelectric material of the present invention enhances the moisture resistance of the piezoelectric material and the efficiency at the time of high-speed vibration.

(Dissipation factor)
The dielectric loss tangent of the piezoelectric material of the present invention at room temperature is preferably 0.02 or less (2% or less). When the dielectric loss tangent at room temperature is 0.02 or less, the power consumption of the piezoelectric element or electronic device using the piezoelectric material of the present invention can be suppressed. More preferably, the dielectric loss tangent at room temperature is 0.013 or less (1.3% or less), and even more preferably 0.01 or less (1% or less).

The dielectric loss tangent of the piezoelectric material at room temperature can be measured, for example, at a frequency of 1 kHz by using a commercially available impedance analyzer after attaching an electrode to the piezoelectric material.

(Manufacturing method of piezoelectric material)
The piezoelectric material of the present invention is characterized in its constituent components, composition ratio, and crystal structure, and there are no particular restrictions on the production method, and the piezoelectric material of the present invention can be obtained by a general means for synthesizing an inorganic oxide. ..

Hereinafter, an example of a desirable manufacturing method will be described.

In order to obtain piezoelectric ceramics, which is one aspect of the form of the piezoelectric material of the present invention, a molded product before firing is produced. Here, the ceramics represent a so-called polycrystal, which is a metal oxide as a basic component and is an aggregate (also referred to as a bulk body) of crystal particles baked and hardened by heat treatment. Ceramics are also included in those processed after sintering. The molded product is a solid product obtained by molding raw material powder.

The raw material powder is preferably of high purity.

Examples of the powder of the metal compound that can be used as the raw material powder include Na compound, Ba compound, Ti compound, Nb compound, Mn compound, Zr compound and a composite compound thereof.

Examples of Na compounds that can be used include sodium carbonate, sodium niobate, and the like.

Examples of the Ba compound that can be used include barium oxide, barium carbonate, barium oxalate, barium acetate, barium nitrate, barium titanate, and Ba-Nb composite calcination powder.

Examples of Ca compounds that can be used include calcium oxide, calcium carbonate, calcium oxalate, calcium acetate, calcium titanate, calcium zirconate, calcium zirconate titanate and the like.

Examples of Ti compounds that can be used include titanium oxide and barium titanate.

Examples of the Nb compound that can be used include niobium oxide and sodium niobate.

Examples of Mn compounds that can be used include manganese oxide (IV), manganese oxide (II), manganese oxide (II), manganese carbonate (II), manganese acetate (II), manganese nitrate (II), and manganese oxalate (II). And so on.

Examples of the Zr compound that can be used include zirconium oxide, barium zirconate, barium titanate, and calcium zirconate.

As a desirable combination of raw material powders for forming the piezoelectric material of the present invention, sodium niobate (NaNbO _{3) calcination powder, barium titanate (BaTIO 3 )} calcination powder, barium carbonate and niobide oxide are mixed. Examples thereof include pre-baked Ba-Nb composite pre-baked powder, manganese oxide powder (for example, Mn 3O ₄ , MnO ₂ ), and zirconate compound (for example, calcium zirconate (CaZrO ₃ ), barium zirconate _{(BaZrO 3 )} ). With this combination of raw material powders, crystallization proceeds at a relatively low temperature, for example, 1300 ° C. or lower, and the effect of the present invention of a high Curie temperature can be easily obtained. The raw material mixed powder is preferably used for molding after being calcined at a maximum temperature of 800 ° C. or higher and 1000 ° C. or lower.

Examples of the method for forming the raw material mixed powder include uniaxial pressure processing, cold hydrostatic pressure processing, warm hydrostatic pressure processing, casting molding and extrusion molding. When producing a molded product, it is preferable to use granulated powder. Sintering a molded product using granulated powder has an advantage that the size distribution of the crystal grains of the sintered body tends to be uniform.

The method for granulating the raw material powder of the piezoelectric material is not particularly limited, but the spray-drying method is the most preferable granulation method from the viewpoint that the particle size of the granulated powder can be made more uniform.

Examples of binders that can be used for granulation include PVA (polyvinyl alcohol), PVB (polyvinyl butyral), and acrylic resins. The amount of the binder to be added is preferably 1 part by weight to 10 parts by weight, more preferably 2 parts by weight to 7 parts by weight from the viewpoint of increasing the density of the molded product with respect to the raw material powder of the piezoelectric material.

The method for sintering the molded product is not particularly limited.

Examples of the sintering method include sintering with an electric furnace, sintering with a gas furnace, energization heating method, microwave sintering method, millimeter wave sintering method, HIP (hot isotropic press) and the like. Sintering with an electric furnace and a gas may be a continuous furnace or a batch furnace.

The sintering temperature in the sintering method is not particularly limited, but it is preferably a temperature at which each compound reacts and sufficiently crystal grows. The preferred sintering temperature is 1100 ° C. or higher and 1400 ° C. or lower, and more preferably 1150 ° C. or higher and 1300 ° C. or lower. Piezoelectric materials sintered in the above temperature range show good insulation and piezoelectric constants. In order to reproducibly stabilize the characteristics of the piezoelectric material obtained by the sintering treatment, the sintering temperature should be kept constant within the above range for 1 hour or more and 48 hours or less, more preferably 2 hours or more and 24 hours or less. It is good to do. Further, although a sintering method such as a two-step sintering method may be used, a method without a sudden temperature change is preferable in consideration of productivity.

The piezoelectric material obtained by the sintering process is polished into a desired shape according to the application. After the polishing process, it is preferable to heat-treat at a temperature equal to or higher than the Curie temperature. When mechanically polished, residual stress is generated inside the piezoelectric material, but by heat treatment at the Curie temperature or higher, the residual stress is relaxed and the piezoelectric characteristics of the piezoelectric material are further improved. The specific time of the heat treatment is not particularly limited, but for example, a heat treatment in which the temperature of 300 ° C. or higher and 500 ° C. or lower is maintained for 1 hour or longer and 24 hours or lower is preferable.

When the average particle size of the crystals constituting the piezoelectric material of the present invention is 0.2 μm or more and 50 μm or less, it is preferable from the viewpoint of achieving both piezoelectricity and processing strength. By setting the average particle size within the above range, it is possible to obtain mechanical strength during cutting and polishing while ensuring sufficient piezoelectricity. A more preferable range of the average particle size is 0.3 μm or more and 20 μm or less. In the present specification, the average particle size means an average circle equivalent diameter. The circle-equivalent diameter represents the "projected area circle-equivalent diameter" generally referred to in the microscope observation method, and represents the diameter of a perfect circle having the same area as the projected area of the crystal grains.

Although the present invention relates to a piezoelectric material, it may be in any form other than ceramics, such as powder, single crystal, membrane, and slurry.

When the piezoelectric material of the present invention is used as a film formed on a substrate, the thickness of the piezoelectric material is preferably 200 nm or more and 10 μm or less, more preferably 300 nm or more and 3 μm or less. This is because a sufficient electromechanical conversion function as a piezoelectric element can be obtained by setting the film thickness of the piezoelectric material to 200 nm or more and 10 μm or less.

The method of laminating the film is not particularly limited. For example, chemical solution deposition method (CSD method), sol-gel method, metalorganic chemical vapor deposition method (MOCVD method), sputtering method, pulse laser deposition method (PLD method), hydrothermal synthesis method, aerosol deposition method (AD). Law) and so on. Of these, the most preferable laminating method is a chemical solution deposition method or a sputtering method. The chemical solution deposition method or the sputtering method can easily increase the film formation area. The substrate used for the piezoelectric material of the present invention is preferably a single crystal substrate cut and polished on the (001) plane, the (110) plane or the (111) plane. By using a single crystal substrate cut and polished on a specific crystal plane, the piezoelectric material film provided on the surface of the substrate can also be strongly oriented in the same direction.

(Piezoelectric element)
Next, the piezoelectric element of the present invention will be described.

FIG. 1 is a schematic view showing an embodiment of the configuration of the piezoelectric element of the present invention. The piezoelectric element according to the present invention is a piezoelectric element having at least a first electrode 1, a piezoelectric material portion 2 and a second electrode 3, and the piezoelectric material constituting the piezoelectric material portion 2 is the piezoelectric material of the present invention. It is characterized by being.

The piezoelectric material according to the present invention can be evaluated for its piezoelectric characteristics by forming a piezoelectric element having at least a first electrode and a second electrode. The first electrode and the second electrode are made of a conductive layer having a thickness of about 5 nm to 10 μm. The material is not particularly limited, and may be any material usually used for a piezoelectric element. For example, metals such as Ti, Pt, Ta, Ir, Sr, In, Sn, Au, Al, Fe, Cr, Ni, Pd, Ag, Cu and compounds thereof can be mentioned.

The first electrode and the second electrode may be made of one of them, or may be made by stacking two or more of them. Further, the first electrode and the second electrode may be made of different materials.

The method for producing the first electrode and the second electrode is not limited, and the first electrode and the second electrode may be formed by baking a metal paste, sputtering, a vapor deposition method, or the like. Further, both the first electrode and the second electrode may be used by patterning them into a desired shape.

(polarization)
It is more preferable that the piezoelectric element has the polarization axes aligned in a certain direction. When the polarization axes are aligned in a certain direction, the piezoelectric constant of the piezoelectric element becomes large.

The polarization method of the piezoelectric element is not particularly limited. The polarization treatment may be performed in the atmosphere or in silicone oil. The temperature at the time of polarization is preferably 60 ° C. to 150 ° C., but the optimum conditions differ slightly depending on the composition of the piezoelectric material constituting the device. The electric field applied for the polarization treatment is preferably 800 V / mm to 3.0 kV / mm.

(PE Hysteresis measurement)
Since the piezoelectric material layer of the piezoelectric element of the present invention has a ferroelectric characteristic, it has a polarization-electric field hysteresis characteristic. The polarization-electric field hysteresis characteristic means that the AC electric field applied to the ferroelectric substance has a historical effect in the relationship between the amount of polarization generated by the ferroelectric substance. Due to this historical effect, the piezoelectric material layer has positive or negative polarization even when the external electric field is 0, and this polarization value is called residual polarization ± Pr. Similarly, the electric field in which the amount of polarization becomes 0 is also divided into two, and the magnitude of these electric fields is called the coercive electric field ± Ec.

The polarization-electric field hysteresis characteristic is generally obtained by converting it from the amount of charge measured while applying a triangular wave voltage to the pair of electrodes facing each other of the piezoelectric element, and is a commercially available device (for example, FCE of Toyo Corporation). Can be measured by.

(Laminate type piezoelectric element)
Next, a laminated type piezoelectric element, which is an embodiment of the piezoelectric element, will be described.

In the laminated piezoelectric element according to the present invention, in the piezoelectric element, at least one internal electrode is provided in the piezoelectric material portion, and the piezoelectric material layer made of the piezoelectric material and the layered at least one internal electrode are alternately arranged. It is characterized by having a laminated laminated structure.

FIG. 2 is a schematic cross-sectional view showing an embodiment of the configuration of the laminated piezoelectric element of the present invention. The laminated piezoelectric element according to the present invention is composed of a piezoelectric material layer 54, 504 and an electrode layer including internal electrodes 55, 505, and is a laminated piezoelectric element in which these are alternately laminated, and the piezoelectric material. The layers 54 and 504 are characterized by being made of the above-mentioned piezoelectric material. The electrode layer may include external electrodes such as the first electrodes 51 and 501 and the second electrodes 53 and 503 in addition to the internal electrodes 55 and 505.

In FIG. 2A, two layers of piezoelectric material layers 54 and one layer of internal electrodes 55 are alternately laminated, and the laminated structure thereof is sandwiched between the first electrode 51 and the second electrode 53. The configuration of the piezoelectric element is shown. As shown in FIG. 2B, the number of piezoelectric material layers and internal electrodes may be increased, and the number of layers is not limited. In the laminated piezoelectric element of FIG. 2B, 9 layers of piezoelectric material layers 504 and 8 layers of internal electrodes 505 (505a or 505b) are alternately laminated. The laminated structure has a structure in which a piezoelectric material layer is sandwiched between a first electrode 501 and a second electrode 503, and has an external electrode 506a and an external electrode 506b for short-circuiting the alternately formed internal electrodes.

The sizes and shapes of the internal electrodes 55, 505 and the external electrodes 506a, 506b, the first electrodes 51, 501 and the second electrodes 53, 503 do not necessarily have to be the same as those of the piezoelectric material layers 54, 504, and may be plural. It may be divided.

The internal electrodes 55 and 505, the external electrodes 506a and 506b, the first electrodes 51 and 501 and the second electrodes 53 and 503 are made of a conductive layer having a thickness of about 5 nm to 10 μm. The material is not particularly limited, and may be any material usually used for a piezoelectric element. For example, metals such as Ti, Pt, Ta, Ir, Sr, In, Sn, Au, Al, Fe, Cr, Ni, Pd, Ag, Cu and compounds thereof can be mentioned. The internal electrodes 55 and 505 and the external electrodes 506a and 506b may be composed of one of them, a mixture or alloy of two or more of them, or a stack of two or more of them. It may be a thing. Further, the plurality of electrodes may be made of different materials.

In the laminated piezoelectric element using the piezoelectric material of the present invention, the internal electrodes 55 and 505 include Ag and Pd, and the weight ratio M1 / M2 between the Ag content weight M1 and the Pd content weight M2 is 1. It is preferable that 5 ≦ M1 / M2 ≦ 9.0. If the weight ratio M1 / M2 is less than 1.5, the heat resistance of the internal electrode is high, but it is not desirable because the electrode cost increases due to the increase in the Pd component. On the other hand, if the weight ratio M1 / M2 is larger than 9.0, the heat resistant temperature of the internal electrodes is insufficient, and the internal electrodes are formed in an island shape and become non-uniform in the plane, which is not desirable. From the viewpoint of heat resistance and cost, 2.0 ≦ M1 / M2 ≦ 5.0 is more preferable.

From the viewpoint that the electrode material is inexpensive, the internal electrodes 55 and 505 preferably contain at least one of Ni and Cu. When at least one of Ni and Cu is used for the internal electrodes 55 and 505, it is preferable that the laminated piezoelectric element of the present invention is fired in a reducing atmosphere.

As shown in FIG. 2B, a plurality of electrodes including the internal electrode 505 may be short-circuited with each other for the purpose of aligning the phases of the drive voltages. For example, the internal electrode 505a and the first electrode 501 may be short-circuited by the external electrode 506a. The internal electrode 505b and the second electrode 503 may be short-circuited by the external electrode 506b. The internal electrodes 505a and the internal electrodes 505b may be arranged alternately. Further, the form of short circuit between electrodes is not limited. An electrode or wiring for short-circuiting may be provided on the side surface of the laminated piezoelectric element, or a through hole penetrating the piezoelectric material layer 504 may be provided, and a conductive material may be provided inside the through hole to short-circuit the electrodes.

(Manufacturing method of laminated piezoelectric element)
The method for manufacturing the laminated piezoelectric element according to the present invention is not particularly limited, but the manufacturing method thereof will be exemplified below. First, a step (A) of dispersing a metal compound powder containing at least Mn, Na, Nb, Ba, and Ti to obtain a slurry, and a step (B) of placing the slurry on a substrate to obtain a molded product. To execute. After that, a step (C) of forming an electrode on the molded body and a step (D) of sintering the molded body on which the electrode is formed to obtain a laminated piezoelectric element are executed.

The metal oxide that can be used in the step (A) is as exemplified as the raw material powder. Particularly desirable combinations of raw material powders include sodium niobate (NaNbO _{3) calcination powder, barium titanate (BaTIO 3 )} aging powder, and Ba-Nb composite aging powder obtained by mixing barium carbonate and niobium oxide. , Manganese oxide powder (eg, Mn 3O ₄ , MnO ₂ ), zirconate compounds (eg, calcium zirconate (CaZrO ₃ ), barium zirconate _{(BaZrO 3 )} ). With this combination of raw material powders, crystallization proceeds at a relatively low temperature, for example, 1300 ° C. or lower, and the effect of the present invention of a high Curie temperature can be easily obtained. It is more preferable that the metal oxide powder is subjected to a calcining treatment at a maximum temperature of 800 ° C. or higher and 1000 ° C. or lower and then made into a slurry.

An example is a method for producing a slurry in the step (A). A solvent having a weight of 1.6 to 1.7 times that of the metal compound powder is added and mixed. As the solvent, for example, toluene, ethanol, a mixed solvent of toluene and ethanol, n-butyl acetate, or water can be used. After mixing in a ball mill for 24 hours, a trace amount of binder and plasticizer is added.

Examples of the binder include PVA (polyvinyl alcohol), PVB (polyvinyl butyral), and acrylic resins. Examples of the plasticizer include dioctyl sebacate, dioctyl phthalate, and dibutyl phthalate. If dibutyl phthalate is used as the plasticizer, weigh it equally with the binder. Then, run the ball mill again overnight. The amount of solvent and binder is adjusted so that the viscosity of the slurry is 300 to 500 mPa · s.

The molded product in the step (B) is a sheet-shaped mixture of the metal compound powder, the binder and the plasticizer. As a method for obtaining a molded product in the step (B), for example, there is sheet molding. For example, the doctor blade method can be used for sheet molding. The doctor blade method is a method of forming a sheet-shaped molded product by applying the slurry onto the substrate and drying it using a doctor blade.

As the base material, for example, a pet film can be used. It is desirable to coat the surface on which the slurry of the pet film is to be placed, for example, with fluorine because it is easy to peel off the molded product. The drying may be natural drying or hot air drying. The thickness of the molded product is not particularly limited and can be adjusted according to the thickness of the laminated piezoelectric element. The thickness of the molded product can be increased, for example, by increasing the viscosity of the slurry.

The manufacturing method of the electrode, that is, the internal electrode 505 and the external electrodes 506a and 506b in the step (C) is not limited, and may be formed by baking a metal paste, or may be formed by a sputtering method, a vapor deposition method, a printing method, or the like. good. For the purpose of reducing the drive voltage, the layer thickness and pitch interval of the piezoelectric material layer 504 may be reduced. At that time, a process of simultaneously firing the laminate after forming the laminate including the precursor of the piezoelectric material layer 504 and the internal electrodes 505a and 505b is selected. In that case, a material for an internal electrode that does not cause shape change or conductive deterioration due to the temperature required for sintering the piezoelectric material layer 504 is required. Metals or alloys thereof having a lower melting point and lower cost than Pt such as Ag, Pd, Au, Cu, and Ni can be used for the internal electrodes 505a and 505b and the external electrodes 506a and 506b. However, the external electrodes 506a and 506b may be provided after firing the laminate, and in that case, Al or a carbon-based electrode material can be used in addition to Ag, Pd, Cu and Ni.

A screen printing method is desirable as a method for forming the electrodes. The screen printing method is a method in which a screen plate is placed on a molded body placed on a base material and then a metal paste is applied using a spatula. A screen mesh is formed in at least a part of the screen plate. Therefore, the metal paste of the portion where the screen mesh is formed is applied onto the molded body. It is desirable that the screen mesh in the screen plate has a pattern formed. By transferring the pattern to the molded body using a metal paste, the electrodes can be patterned on the molded body.

After forming the electrode in the step (C) and peeling it from the base material, one or a plurality of the molded bodies are stacked and pressure-bonded. Examples of the crimping method include uniaxial pressure processing, cold hydrostatic pressure processing, and warm hydrostatic pressure processing. Warm hydrostatic pressure processing is desirable because it can apply pressure evenly and isotropically. It is desirable to heat the binder to the vicinity of the glass transition temperature during crimping because the crimping can be performed better. A plurality of the molded products can be stacked and crimped until they have a desired thickness. For example, after stacking 5 to 100 layers of the molded product, the molded product can be laminated by thermocompression bonding at a pressure of 10 to 60 MPa at 50 to 80 ° C. in the stacking direction for 10 seconds to 10 minutes. .. Further, by attaching an alignment mark to the electrodes, it is possible to align a plurality of molded bodies and stack them with high accuracy. Further, by providing a through hole for positioning in the molded body, it is possible to stack them with high accuracy.

The sintering temperature of the molded product in the step (D) is not particularly limited, but it is preferably a temperature at which each compound reacts and sufficiently crystal grows. The preferred sintering temperature is 1100 ° C. or higher and 1400 ° C. or lower, and more preferably 1150 ° C. or higher and 1300 ° C. or lower, from the viewpoint of setting the particle size of the ceramics in the range of 0.2 μm to 50 μm. The laminated type piezoelectric element sintered in the above temperature range exhibits good piezoelectric performance.

However, when a material containing Ni as a main component is used for the electrode in the step (C), it is preferable to perform the step (D) in a furnace capable of firing in an atmosphere. After the binder is burnt off at a temperature of 200 ° C. to 600 ° C. in the air atmosphere, the binder is changed to a reducing atmosphere and sintered at a temperature of 1200 ° C. to 1550 ° C. Here, the reducing atmosphere mainly refers to an atmosphere composed of a mixed gas of hydrogen (H ₂ ) and nitrogen (N ₂ ). The volume ratio of hydrogen and nitrogen is preferably in the range of H ₂ : N ₂ = 1: 99 to H ₂ : N ₂ = 10: 90. Further, the mixed gas may contain oxygen. Its oxygen concentration is ^10-12 Pa or more and ^10-4 Pa or less. More preferably, it is ^10-8 Pa or more and ^10-5 Pa or less. Oxygen concentration can be measured with a zirconia oxygen meter. By using the Ni electrode, the laminated piezoelectric element of the present invention can be manufactured at low cost. After firing in a reducing atmosphere, it is preferable to lower the temperature to 600 ° C. and replace the atmosphere with an atmospheric atmosphere (oxidizing atmosphere) to perform an oxidation treatment. After being taken out from the firing furnace, a conductive paste is applied to the side surface of the prime field where the end portion of the internal electrode is exposed and dried to form an external electrode.

(Electronics)
The electronic device according to the present invention is characterized by comprising the piezoelectric element of the present invention.

(Example of electronic device 1: liquid discharge head, liquid discharge device)
3 (a) and 3 (b) are schematic views schematically showing the configuration of a liquid discharge head provided with the piezoelectric element of the present invention and a liquid discharge device using the liquid discharge head as an example of the electronic device of the present invention. Is. The liquid discharge head has at least a liquid chamber provided with a vibrating portion in which the piezoelectric element or the laminated piezoelectric element is arranged, and a discharge port communicating with the liquid chamber. The liquid discharge device includes a mounting portion of the transferred body and the liquid discharge head. However, the shape and arrangement of each member are not limited to the examples of FIGS. 3A and 3B.

As shown in FIG. 3A, the liquid discharge head, which is the electronic device of the present invention, has the piezoelectric element 101 of the present invention. The piezoelectric element 101 has at least a first electrode 1011 and a piezoelectric material 1012, and a second electrode 1013. The piezoelectric material 1012 and the second electrode 1013 may be patterned for the purpose of increasing the discharge force of the liquid discharge head.

The liquid discharge head has a discharge port 105, an individual liquid chamber 103, a communication hole 106 connecting the individual liquid chamber 103 and the discharge port 105, a liquid chamber partition wall 104, a common liquid chamber 107, a diaphragm 102, and a piezoelectric element 101. Generally, the piezoelectric material 1012 has a shape that follows the shape of the individual liquid chamber 103.

When an electric signal is input to the liquid discharge head, which is an example of the electronic device of the present invention, and the liquid is driven, the diaphragm 102 vibrates up and down due to the deformation of the piezoelectric element 101, and pressure is applied to the liquid stored in the individual liquid chamber 103. .. As a result, the liquid is discharged from the discharge port 105. The liquid discharge head can be used for incorporation into a printer that prints on various media or for manufacturing an electronic device.

Next, a liquid discharge device using the liquid discharge head will be described.

This liquid discharge device can also be said to be an example of the electronic device of the present invention. FIG. 3B illustrates a liquid ejection device as an inkjet recording device.

In the liquid discharge device of FIG. 3B, each mechanism is incorporated in the exterior portion 896. The automatic feeding unit 897 has a function of automatically feeding the recording paper as the transfer target into the main body of the apparatus. The recording paper sent from the automatic feeding unit 897 is guided to a predetermined recording position (without a drawing number) by the transport unit 899, and after the recording operation, is again guided from the recording position to the discharge unit 898 by the transport unit 899. The transport section 899 is a mounting section for the transferred body. The liquid discharge device also has a recording unit 891 for recording on the recording paper conveyed to the recording position, and a recovery unit 890 for performing recovery processing on the recording unit 891. The recording unit 891 is provided with a carriage 892 that houses the liquid discharge head and reciprocates on the rail.

In such a liquid ejection device, the carriage 892 transfers the liquid ejection head according to an instruction from an external computer, and ink is ejected from the ejection port 105 of the liquid ejection head in response to a voltage application to the piezoelectric element of the present invention. By doing so, printing is performed.

Although the above example has been exemplified as a printer, the liquid discharge device of the present invention is used as a printing device such as an inkjet recording device such as a facsimile, a multifunction device, and a copying machine, an industrial liquid discharge device, and a drawing device for an object. can do. In addition, the user can select a desired transfer target according to the application.

(Example 2: Electronic device: Vibration wave motor, optical device)
4 (a) to 4 (e) are schematic views schematically showing the configuration of a vibration wave motor provided with the piezoelectric element of the present invention and an optical device using the vibration wave motor as an example of the electronic device of the present invention. Is. The vibration wave motor has at least a vibrating body in which the piezoelectric element or the laminated piezoelectric element is arranged, and a moving body in contact with the vibrating body. The optical device includes the vibration wave motor in the drive unit. However, the shape and arrangement of each member are not limited to the examples of FIGS. 4A to 4E.

FIG. 4A shows a vibration wave motor in which the piezoelectric element of the present invention is a single plate. The vibrating wave motor is integrally provided with the vibrating body 201, the moving body 202 (also referred to as a rotor), and the moving body 202, which are in contact with the sliding surface of the vibrating body 201 by the pressure applied by a pressure spring (not shown). It has an output shaft 203. The vibrating body 201 is composed of a metal elastic body ring 2011, a piezoelectric element 2012 of the present invention, and an organic adhesive 2013 (epoxy-based, cyanoacrylate-based, etc.) for adhering the piezoelectric element 2012 to the elastic body ring 2011.

When a two-phase alternating voltage having a phase different by an odd number of π / 2 is applied to the piezoelectric element, a bending progressive wave is generated in the vibrating body 201, and each point on the sliding surface of the vibrating body 201 makes an elliptical motion. The rotor 202 receives a frictional force from the vibrating body 201 and rotates in the direction opposite to the bending traveling wave. The driven body (not shown) is joined to the output shaft 203 and is driven by the rotational force of the rotor 202.

Next, a vibration wave motor including a piezoelectric element having a laminated structure (laminated piezoelectric element) is illustrated in FIG. 4 (b). The vibrating body 204 is composed of a laminated piezoelectric element 2042 sandwiched between tubular metal elastic bodies 2041. The laminated piezoelectric element 2042 is the laminated element, and has a first electrode and a second electrode on the outer surface of the laminate, and an internal electrode on the inner surface of the laminate. The metal elastic body 2041 sandwiches and fixes the laminated piezoelectric element 2042 with bolts to form the vibrating body 204.

By applying alternating voltages having different phases to the laminated piezoelectric element 2042, the vibrating body 204 excites two vibrations orthogonal to each other. These two vibrations are combined to form a circular vibration for driving the tip of the vibrating body 204. A constricted peripheral groove is formed in the upper part of the vibrating body 204 to increase the displacement of the vibration for driving.

The moving body 205 (also referred to as a rotor) pressurizes and contacts the vibrating body 204 by a pressurizing spring 206 to obtain a frictional force for driving. The moving body 205 is rotatably supported by bearings.

Next, an optical device using the vibration wave motor will be described.

This optical device can also be said to be an example of the electronic device of the present invention. FIGS. 4 (c), (d), and (e) illustrate an optical device as an interchangeable lens barrel of a single-lens reflex camera.

A fixed cylinder 712, a straight guide cylinder 713, and a front lens barrel 714 are fixed to the detachable mount 711 with and from the camera. These are the fixing members of the interchangeable lens barrel.

The straight guide cylinder 713 is formed with a straight guide groove 713a in the optical axis direction for the focus lens 702. Cam rollers 717a and 717b projecting outward in the radial direction are fixed to the rear lens barrel 716 holding the focus lens 702 by a shaft screw 718, and the cam rollers 717a are fitted in the straight guide groove 713a.

A cam ring 715 is rotatably fitted to the inner circumference of the straight guide cylinder 713. The straight guide cylinder 713 and the cam ring 715 are restricted from moving in the optical axis direction by the roller 719 fixed to the cam ring 715 being fitted into the peripheral groove 713b of the straight guide cylinder 713. A cam groove 715a for the focus lens 702 is formed in the cam ring 715, and the above-mentioned cam roller 717b is simultaneously fitted in the cam groove 715a.

On the outer peripheral side of the fixed cylinder 712, a rotation transmission ring 720 held so as to be rotatable in a fixed position with respect to the fixed cylinder 712 by a ball race 727 is arranged. In the rotation transmission ring 720, the roller 722 is freely rotatably held by the shaft 720f extending radially from the rotation transmission ring 720, and the large diameter portion 722a of the roller 722 is in contact with the mount side end surface 724b of the manual focus ring 724. is doing. Further, the small diameter portion 722b of the roller 722 is in contact with the joining member 729. Six rollers 722 are arranged at equal intervals on the outer circumference of the rotation transmission ring 720, and each roller is configured by the above relationship.

A low friction sheet (washer member) 733 is arranged on the inner diameter of the manual focus ring 724, and this low friction sheet is sandwiched between the mount side end surface 712a of the fixed cylinder 712 and the front end surface 724a of the manual focus ring 724. There is. Further, the outer diameter surface of the low friction sheet 733 is ring-shaped and is diameter-fitted with the inner diameter 724c of the manual focus ring 724, and the inner diameter 724c of the manual focus ring 724 is diameter-fitted with the outer diameter portion 712b of the fixed cylinder 712. It fits. The low friction sheet 733 serves to reduce friction in the rotating ring mechanism in which the manual focus ring 724 rotates relative to the fixed cylinder 712 about the optical axis.

The large diameter portion 722a of the roller 722 and the mount-side end surface 724b of the manual focus ring are in contact with each other in a state where a pressing force is applied by the force of the wave washer 726 pressing the vibration wave motor 725 toward the front of the lens. .. Similarly, due to the force of the wave washer 726 pressing the vibration wave motor 725 toward the front of the lens, the small diameter portion 722b of the roller 722 and the joining member 729 are also in contact with each other in a state where an appropriate pressing force is applied. The wave washer 726 is restricted from moving in the mounting direction by a washer 732 that is bayonet-coupled to the fixed cylinder 712. The spring force (urging force) generated by the wave washer 726 is transmitted to the vibration wave motor 725 and further to the roller 722, and the manual focus ring 724 also serves as a pressing force on the mount side end surface 712a of the fixed cylinder 712. That is, the manual focus ring 724 is incorporated in a state of being pressed against the mount side end surface 712a of the fixed cylinder 712 via the low friction sheet 733.

Therefore, when the ultrasonic motor 725 is rotationally driven with respect to the fixed cylinder 712 by a control unit (not shown), the joining member 729 is in frictional contact with the small diameter portion 722b of the roller 722, so that the roller 722 is centered on the shaft 720f. Rotate around. When the roller 722 rotates around the axis 720f, the rotation transmission ring 720 rotates about the optical axis as a result.

Two focus keys 728 are attached to the rotation transmission ring 720 at positions facing each other, and the focus key 728 is fitted with a notch 715b provided at the tip of the cam ring 715. Therefore, when the rotation transmission ring 720 rotates around the optical axis, the rotational force is transmitted to the cam ring 715 via the focus key 728. When the cam ring is rotated around the optical axis, the rear lens barrel 716 whose rotation is restricted by the cam roller 717a and the straight guide groove 713a moves back and forth along the cam groove 715a of the cam ring 715 by the cam roller 717b. As a result, the focus lens 702 is driven and the focus operation is performed.

In the above example, as an optical device using the vibration wave motor, an interchangeable lens barrel of a single-lens reflex camera has been described. However, regardless of the type of camera such as a compact camera or an electronic still camera, a vibration wave motor is used in the drive unit. The vibration wave motor can be applied to an optical instrument having the vibration wave motor.

(Example 3: Electronic device: Vibration device, image pickup device)
5 (a) to 5 (d) are schematic views schematically showing the configuration of a vibration device provided with the piezoelectric element of the present invention and an image pickup device using the vibration device as an example of the electronic device of the present invention. .. The vibrating device shown in FIG. 5 is a dust removing device having at least a vibrating body in which the piezoelectric element of the present invention is arranged on the diaphragm and having a function of removing dust adhering to the surface of the diaphragm. The image pickup device is an image pickup device having at least the dust removal device and the image pickup element unit, and the diaphragm of the dust removal device is provided on the light receiving surface side of the image pickup element unit.

However, the shape and arrangement of each member are not limited to the examples of FIGS. 5A to 5D.

5 (a) and 5 (b) are schematic views showing an embodiment of an electronic device as a dust removing device. The dust removing device 310 is composed of a plate-shaped piezoelectric element 330 and a diaphragm 320. The piezoelectric element 330 may be the laminated piezoelectric element of the present invention. The material of the diaphragm 320 is not limited, but when the dust removing device 310 is used for an optical device, a translucent material or a light-reflecting material can be used as the diaphragm 320, and the translucent portion and light reflection of the diaphragm can be used. The part is subject to dust removal.

The piezoelectric element 330 is composed of a piezoelectric material 331, a first electrode 332, and a second electrode 333, and the first electrode 332 and the second electrode 333 are arranged so as to face the plate surface of the piezoelectric material 331. .. In the case of a laminated piezoelectric element, the piezoelectric material 331 has an alternating structure of a piezoelectric material layer and an internal electrode, and the internal electrodes are alternately short-circuited with the first electrode 332 or the second electrode 333 to form a layer of the piezoelectric material. It is possible to give a drive waveform with a different phase for each. In FIG. 5A, the first electrode 332 wraps around to the side of the second electrode 333.

When an alternating voltage is applied to the piezoelectric element 330 from the outside, stress is generated between the piezoelectric element 330 and the diaphragm 320, causing out-of-plane vibration in the diaphragm. The dust removing device 310 is a device that removes foreign matter such as dust adhering to the surface of the diaphragm 320 due to the out-of-plane vibration of the diaphragm 320. Out-of-plane vibration is elastic vibration that displaces the diaphragm in the optical axis direction, that is, in the thickness direction of the diaphragm.

Next, an image pickup device using the dust removing device will be described. This image pickup device is also an example of the electronic device of the present invention. FIGS. 5 (c) and 5 (d) illustrate an image pickup device as a digital single-lens reflex camera.

FIG. 5C is a front perspective view of the camera body 601 as viewed from the subject side, showing a state in which the photographing lens unit is removed. FIG. 5D is an exploded perspective view showing a schematic configuration inside the camera for explaining the peripheral structure of the dust removing device and the image pickup unit 400.

A mirror box 605 for guiding a shooting light flux passing through a shooting lens is provided in the camera body 601 shown in FIG. 5 (c), and a main mirror (quick return mirror) 606 is arranged in the mirror box 605. ing. The main mirror 606 is held at an angle of 45 ° with respect to the shooting optical axis in order to guide the shooting light flux in the direction of the pentadha mirror (not shown), and in order to guide it in the direction of the image sensor (not shown). It can be held in a position retracted from the shooting light beam.

In FIG. 5D, a mirror box 605 and a shutter unit 200 are arranged on the subject side of the main body chassis 300, which is the skeleton of the camera body, in order from the subject side. Further, an image pickup unit 400 is arranged on the photographer side of the main body chassis 300. The image pickup unit 400 is composed of a diaphragm of a dust removing device and an image pickup element unit. Further, the diaphragms of the dust removing device are sequentially provided on the same axis as the light receiving surface of the image pickup element unit. The image pickup unit 400 is installed on the mounting surface of the mount portion 602 (FIG. 5 (c)) as a reference to which the photographing lens unit is attached, and the image pickup surface of the image pickup element unit is separated from the image pickup lens unit by a predetermined distance. It is adjusted to be parallel.

Here, a digital single-lens reflex camera has been described as an example of an image pickup apparatus, but a camera with an interchangeable shooting lens unit such as a mirrorless digital single-lens camera that does not have a mirror box 605 may be used. In addition, among electronic and electrical equipment equipped with various image pickup devices or image pickup devices such as video cameras with interchangeable shooting lens units and copiers, facsimiles, scanners, etc., devices that require removal of dust adhering to the surface of optical components in particular. Can also be applied to.

Up to this point, as examples of the electronic device of the present invention, a liquid discharge head, a liquid discharge device, a vibration wave motor, an optical device, a vibration device, and an image pickup device have been described, but the types of the electronic device are not limited thereto. Electronic devices that detect electrical signals and extract energy due to the positive piezoelectric effect by extracting power from the piezoelectric element, and electronic devices that utilize displacement due to the inverse piezoelectric effect by inputting power to the piezoelectric element. In general, the piezoelectric element of the present invention can be applied. For example, a piezoelectric acoustic component, a voice reproduction device having the piezoelectric acoustic component, a voice recording device, a mobile phone, an information terminal, and the like are also included in the electronic device of the present invention.

The piezoelectric material of the present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples.

Tables 1 and 2 show the compositions and firing temperatures of the sintered bodies of Examples 11 to 13, 21 to 23, 31 to 33 and Comparative Examples 11, 21, 31 of the present invention. In the table, t, z, β, α, m, and γ are the abundance of Ti, the abundance of Zr, the abundance of Ba, the abundance of Na, and the abundance of Mn, respectively, when the abundance of Nb is 1. , Represents the abundance of Ca.

The composition of the sintered body was evaluated by ICP (inductively coupled plasma emission spectroscopy), and there was a measurement distribution of 5 to 10% including the repetition error of sample synthesis and the measurement error of the apparatus. For example, regarding the composition parameters of the sample groups in Examples 11 to 33, the t-value is distributed in the range of 0.10 to 0.155, and the z-value is distributed in the range of 0.010 to 0.037. The β value is distributed in the range of 0.10 to 0.17, the α value is distributed in the range of 0.95 to 1.03, and the m value is 0.0006 to 0.0025. It was distributed in the range. The compositions shown in Tables 1 and 2 are average values of these.

Examples 11 to 13 and Comparative Example 1 have the general formula (1) Na (α) Ba (β) Nb (1) Ti (t) -Zr (z) -Mn (m) -Ca (γ) in Table 1. The raw materials were weighed so as to be t, z, β, α, m and γ.

Examples 21 to 23 and 31 to 33 and Comparative Examples 21 and 31 are shown in Table 2 in the general formula (2) Na (α) Ba (β) Nb (1) Ti (t) -Zr (z) -Mn (m). The raw materials were weighed so as to have t, z, β, α and m. However, Examples 21 to 23 and 31 to 33 and Comparative Examples 21 and 31 were prepared in such a form that the abundance of Nb was set to 1 and 0.011 Zn was added to the elements shown in Table 2.

The raw material powders of the examples were mixed by running a ball mill for 12 hours.

The raw materials of Examples 11 to 13 and Comparative Example 11 are sodium niobate (NaNbO ₃ ) having a purity of 99% or more, barium titanate (BaTIO ₃ ) having a purity of 99% or more, and calcium zirconate (CaZrO) having a purity of 99% or more. ₃ ) A powder of manganese oxide (Mn ₃ O ₄ ) having a purity of 99.9% was used.

The raw materials of Examples 21 to 23, 31 to 33 and Comparative Examples 21 and 31 are sodium niobate (NaNbO ₃ ) having a purity of 99% or more, barium titanate (BaTIO ₃ ) having a purity of 99% or more, and a purity of 99% or more. Barium zirconate (BaZrO ₃ ), manganese oxide (MnO ₂ ) having a purity of 99.9%, and zinc oxide (ZnO) having a purity of 99% or more were used.

The mixed powder was calcined in the air at 900 ° C to 1100 ° C for 2-5 hours. The calcined powder was pulverized, and 3% by weight of PVB binder was added to the weight of the calcined powder to granulate. The granulated powder was filled in a mold and compressed at a pressure of 200 MPa to prepare a molded product having a diameter of 17 mm and a thickness of about 1 mm. The obtained molded product was fired in air at 1100 ° C. to 1280 ° C. for 2 to 6 hours to obtain a sintered body. However, even if this calcination step is omitted, a piezoelectric material exhibiting the effect of the present invention can be obtained.

When the density of the sintered body was measured by the Archimedes method and the relative density was calculated, the relative density of each sintered body was 94% or more.

The relative density is the ratio of the measured density to the theoretical density calculated from the lattice constant of the piezoelectric material and the atomic weight of the constituent elements of the piezoelectric material. The lattice constant can be measured, for example, by X-ray diffraction analysis. The density can be measured, for example, by a known Archimedes method.

The sintered body was polished to a thickness of about 0.5 mm. X-ray diffraction was performed using the polished sintered body or the powder obtained by crushing the polished sintered body, and the constituent phase and the lattice constant were evaluated. By X-ray diffraction, it was confirmed that the sample was almost a perovskite structure single phase.

The particle size in the sintered body was evaluated by observing with an optical microscope or an electron microscope.

When the particle size of the sintered body was observed with an electron microscope, the average particle size was in the range of 2 to 70 μm.

A titanium film having a diameter of 30 nm was formed as an adhesion layer between the electrode and the ceramics. The ceramics with electrodes were cut to produce a strip-shaped piezoelectric element of 10 mm × 2.5 mm × 0.5 mmt.

A semiconductor parameter analyzer was used to evaluate the resistivity. A DC voltage of several tens of volts to 100 volts was applied to the sample, and the resistance was measured 30 seconds after the start of voltage application. The resistivity was calculated from the measured resistance and sample dimensions.

The electric field-polarization hysteresis measurement was performed to determine the presence or absence of ferroelectricity in a practical electric field of the target element at room temperature. A material that exhibits ferroelectricity in a certain temperature range has piezoelectricity in the same temperature range and can also be used as a memory material. Specifically, the amount of polarization when an AC electric field (triangular wave) was applied to the piezoelectric element of the present invention was measured. The frequency of the AC electric field was 10 to 100 Hz. The maximum electric field strength was about ± 50 kV / cm.

Polarization treatment was performed prior to the evaluation of the piezoelectric characteristics. Specifically, a voltage of 1.5 to 5 kV / mm was applied to the sample for 30 minutes in an oil bath maintained at 110 to 150 ° C., and the sample was cooled to room temperature while the voltage was still applied.

The piezoelectric constant (d ₃₁ ), mechanical quality coefficient (Qm), and dielectric loss tangent (tan δ) of the strip-shaped piezoelectric element were measured by the resonance antiresonance method. The piezoelectric constant (d ₃₃ ) was evaluated using the same sample by a d ₃₃ meter based on the Berlin coat method. An impedance analyzer was used to measure the relative permittivity. The relative permittivity in the present specification is a value at a measurement frequency of 1 kHz, and the magnitude of the applied AC electric field is 500 mV. The measurement was performed after the polarization treatment. When evaluating the temperature dependence of the relative permittivity, the change in the relative permittivity when the measurement of the relative permittivity is started from room temperature, the sample is once cooled from room temperature to -100 ° C, and then raised to 350 ° C. Was recorded, and the Curie temperature and the successive phase transition temperature were calculated from the maximum part of the relative permittivity.

Table 2, Table 3, and Table 4 show the characteristics of typical samples.

(Piezoelectric materials and piezoelectric elements of Examples 11 to 13 and Comparative Example 11)
Examples 11 to 13 are samples in which z representing the amount of Zr with respect to Nb is 0.029 and m representing the amount of Mn is 0.0007 to 0.0011. As shown in Table 3 and FIG. 6 (a), | d ₃₃ / d ₃₁ | increased with the addition of Mn. Further, as shown in Table 5, an increase in Curie temperature was obtained. Further, as shown in Table 4 and FIG. 6 (b), better results of an increase in resistivity and a decrease in dielectric loss tangent were obtained in Examples 11 to 13 as compared with Comparative Example 11 in which Mn was not added. On the other hand, when Mn is added in an amount of more than 0.005 mol%, a perovskite-type metal oxide is not formed, the resistivity is remarkably lowered, and the piezoelectric characteristics cannot be measured.

(Piezoelectric materials and piezoelectric elements of Examples 21 to 23 and Comparative Example 21)
Examples 21 to 23 are samples in which m representing the amount of Mn with respect to Nb in the perovskite-type metal oxide represented by the general formula (2) is 0.0023 and z representing the amount of Zr is 0.011 to 0.034. Was fired at 1150 ° C. The resistivity of the samples of Examples 21 to 23 was high as shown in Table 4, and the dielectric loss tangent (tan δ) was as low as 0.02 or less as shown in Table 3. FIG. 7 is a diagram showing the relationship between the | d ₃₃ / d ₃₁ | values of the Zr amount in the piezoelectric elements of Examples 21 to 23, 31 to 33 and Comparative Examples 21 and 31 of the present invention. An increase in the relative permittivity was observed with the addition of Zr. Further, in Examples 21 to 23, | d ₃₃ / d ₃₁ | became larger with the addition of Zr than in Comparative Example 21 to which Zr was not added. Further, as shown in Table 3, the mechanical quality coefficient (Qm) increased with the addition of Zr. On the other hand, the Curie temperature (Tc) decreases according to the amount of Zr added. When z representing the amount of Zr exceeds 0.04, the Curie temperature is remarkably lowered and the resistivity is also remarkably lowered, which is not preferable as a material used for the piezoelectric element.

(Piezoelectric materials and piezoelectric elements of Examples 31 to 33 and Comparative Example 31)
In Examples 31 to 33, in the piezoelectric material made of the perovskite-type metal oxide represented by the general formula (2), m representing the amount of Mn with respect to Nb in the piezoelectric material is 0.0023, and z representing the amount of Zr is 0. Samples of 011 to 0.034 are calcined at 1100 ° C. The resistivity of the samples of Examples 31 to 33 was a high value as shown in Table 4, and the dielectric loss tangent (tan δ) was also a low value of 0.02 or less. An increase in the relative permittivity was observed with the addition of Zr. Further, in Examples 31 to 33, | d ₃₃ / d ₃₁ | became larger with the addition of Zr than in Comparative Example 31 in which Zr was not added. In addition, the mechanical quality coefficient (Qm) increased with the addition of Zr. On the other hand, the Curie temperature (Tc) decreases according to the amount of Zr added. When z representing the amount of Zr exceeds 0.04, the Curie temperature is remarkably lowered and the resistivity is also remarkably lowered, which is not preferable as a piezoelectric element material.

The samples of Examples 31 to 33 were polished and X-ray diffraction measurements were performed, and it was observed that as the amount of Zr increased, the a-axis length became longer and the c / a ratio of the perovskite structure tended to decrease.

It is more preferable that the relative permittivity at room temperature is 1300 or less from the viewpoint of low power consumption.

(Hysteresis curve of piezoelectric material of Examples 21 to 23 and Comparative Example 21)
The electric field-polarization hysteresis measurement results of the piezoelectric materials of Examples 21 to 23 and Comparative Example 21 are shown in FIG. With the addition of Zr, the hysteresis curve decreased as the amount of Zr increased. That is, there is a decrease in the residual polarization value (polarization value Pr when the applied electric field is zero) and a decrease in the coercive electric field (applied electric field Ec when the sign of polarization is reversed), which is thought to be caused by the reduction in pinning of spontaneous polarization. Was done.

(Example 41)
The laminated piezoelectric element of the present invention was produced in the following manner.

A PVB binder was added to the 900 ° C. calcined powder before spray-dry granulation in Example 12 and mixed, and then a sheet was formed by a doctor blade method to obtain a green sheet having a thickness of 50 μm.

A conductive paste for internal electrodes was printed on the green sheet. As the conductive paste, an Ag70% −Pd30% alloy (Ag / Pd = 2.33) paste was used. Nine green sheets coated with the conductive paste were laminated, and the laminated body was fired at 1200 ° C. for 5 hours to obtain a sintered body. After cutting the sintered body to a size of 10 mm × 2.5 mm, the side surface thereof is polished to form a pair of external electrodes (first electrode and second electrode) in which the internal electrodes are alternately short-circuited by Au sputtering. Then, a laminated piezoelectric element as shown in FIG. 2 (b) was manufactured.

When the cross section of the obtained laminated piezoelectric element was observed, an internal electrode made of Ag—Pd and a piezoelectric material layer were alternately formed.

The laminated piezoelectric element was subjected to a polarization treatment. Specifically, the sample was heated to 150 ° C. in an oil bath, a voltage of 2 kV / mm was applied between the first electrode and the second electrode for 30 minutes, and the sample was cooled to room temperature while the voltage was still applied.

When the piezoelectric characteristics of the obtained laminated piezoelectric element were evaluated, it had sufficient insulating properties, and it was possible to obtain a piezoelectric constant, a Curie temperature, and a dielectric loss tangent equivalent to those of the piezoelectric material of Example 12.

(Example 42)
Using the piezoelectric elements of Examples 12 and 41, the liquid discharge head shown in FIG. 3A was manufactured. It was confirmed that the ink was ejected following the input electric signal.

Using this liquid discharge head, the liquid discharge device shown in FIG. 3 (b) was manufactured. Ink ejection following the input electrical signal was confirmed on the recording medium.

(Example 43)
Using the piezoelectric elements of Examples 12 and 41, the ultrasonic motor shown in FIG. 4 (a) or FIG. 4 (b) was manufactured. It was confirmed that the motor rotated in response to the application of AC voltage.

Using this ultrasonic motor, the optical instruments shown in FIGS. 4 (c), (d), and (e) were manufactured. It was confirmed that the autofocus operation was performed in response to the application of AC voltage.

(Example 44)
Using the piezoelectric elements of Examples 12 and 41, the dust removing device shown in FIGS. 5 (a) and 5 (b) was manufactured. When plastic beads were sprayed and an AC voltage was applied, a good dust removal rate was confirmed.

Using this dust removing device, the image pickup device shown in FIGS. 5 (c), (d), and (e) was manufactured. When this image pickup device was energized, dust on the surface of the image pickup unit was satisfactorily removed, and an image without dust defects was obtained.

The piezoelectric material of the present invention exhibits good piezoelectricity even at a high environmental temperature. Moreover, since it does not contain lead, it has a low impact on the environment. Therefore, the piezoelectric material of the present invention can be used without problems in equipment that uses a large amount of piezoelectric material, such as a liquid discharge head, a vibration wave motor, and a dust removing device.

1 First electrode 2 Piezoelectric material part 3 Second electrode 101 Piezoelectric element

Claims (9)

A piezoelectric material containing Na, Ba, Nb, Ti, Zr, Mn, and Ca and made of a perovskite-type oxide.
T indicating the molar ratio of the Ti to the Nb is 0.08 ≦ t ≦ 0.15.
Z indicating the molar ratio of the Zr to the Nb is 0.01 ≦ z ≦ 0.04,
Β indicating the molar ratio of Ba to Nb is 0.08 ≦ β ≦ 0.17.
Α indicating the molar ratio of the Na to the Nb is 0.95 ≦ α ≦ 1.03.
M indicating the molar ratio of Mn to Nb is 0.0005 ≦ m ≦ 0.0025, and the molar ratio of Ca to Zr is 0.97 or more and 1.03 or less .
| D ₃₃ / d ₃₁ | Piezoelectric material having a value of 3.5 or more and a dielectric loss tangent of less than 0.02 when an alternating voltage of 1 kHz is applied at room temperature . The piezoelectric material according to claim 1, wherein β is 0.08 ≦ β ≦ 0.15. The piezoelectric material according to claim 1 or 2, wherein the Pb component and the K component contained in the piezoelectric material are less than 1000 ppm in total. The piezoelectric material according to any one of claims 1 to 3, wherein the relative permittivity at room temperature is 1300 or less. The piezoelectric material according to any one of claims 1 to 4, wherein the piezoelectric constant d ₃₃ is 200 pm / V or more. The piezoelectric material according to any one of claims 1 to 5, wherein the value of | d ₃₃ / d ₃₁ | is 4.0 or more. A piezoelectric element having a piezoelectric material part and electrodes.
The piezoelectric element according to any one of claims 1 to 6, wherein the piezoelectric material constituting the piezoelectric material portion is the piezoelectric material. The piezoelectric element according to claim 7, wherein the piezoelectric material portion and the electrodes are alternately laminated. The electronic device provided with the piezoelectric element according to claim 7.

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