Piezoelectric element, method for manufacturing piezoelectric element, ultrasonic motor, optical apparatus, vibration device, dust removal device, imaging device, ultrasonic probe, ultrasonic diagnostic device, ultrasonic diagnostic system, and electronic apparatus

Abstract

The purpose of the present invention is to provide a piezoelectric element with which it is possible to achieve both a high electromechanical coupling coefficient and a high coercive electric field and to cope with a broader range of perovskite-type oxide single crystals. A piezoelectric element according to the present invention has a single crystal of a perovskite-type metal oxide and electrodes facing each other, the piezoelectric element being characterized in that when the environmental temperature is 25°C, the crystal system of the single crystal is a tetragonal system, and the crystal orientation of the surfaces of the single crystal in contact with the electrode surfaces of the electrodes facing each other is (110) or (111).

Description

Piezoelectric element, method of manufacturing piezoelectric element, ultrasonic motor, optical device, vibration device, dust removal device, imaging device, ultrasonic probe, ultrasonic diagnostic device, ultrasonic diagnostic system, and electronic device

[0001] The present invention relates to a piezoelectric element and a method for manufacturing the piezoelectric element, and also to an ultrasonic motor, an optical device, a vibration device, a dust removal device, an imaging device, an ultrasonic probe, an ultrasonic diagnostic device, an ultrasonic diagnostic system, and an electronic device that use the piezoelectric element.

[0002] In the case of perovskite-type oxide piezoelectrics, single crystal materials are used to obtain high piezoelectric performance. In lead-based perovskite-type oxides, the electromechanical coupling coefficient k ３３ The dielectric constant is large, at over 90%. However, the coercive field, which indicates the withstand voltage, is smaller than that of polycrystalline materials, and there is a limit to the voltage that can be applied. Patent Document 1 describes a PMN-PT single crystal, and although the material design emphasizes high dielectric constant and high piezoelectric performance, the crystal system is pseudocubic and the coercive field Ec does not become large.

[0003] As a result of extensive research, the inventors have found that by fabricating elements with (110) and (111) orientations that allow single crystals of tetragonal perovskite oxide to be polarized in a direction different from the axis of easy polarization, it is possible to achieve both a high electromechanical coupling coefficient and a high coercive field.

[0004] Patent No. 5156065

[0005] It has been difficult to achieve both a high electromechanical coupling coefficient and a high coercive field with perovskite oxide single crystal materials. The present invention has been made to solve this problem, and aims to provide a piezoelectric element that can be used with a wider range of perovskite oxide single crystals. Another aim of the present invention is to provide a method for manufacturing the above piezoelectric element. Another aim of the present invention is to provide a single crystal piezoelectric element having a high mechanical quality factor and coercive field, and to provide ultrasonic motors, optical instruments, vibration devices, dust removal devices, imaging devices, ultrasonic probes, ultrasonic diagnostic devices, ultrasonic diagnostic systems, and electronic devices that use the piezoelectric element.

[0006] In order to solve the above problems, the present invention provides a piezoelectric element having a single crystal of a perovskite metal oxide and opposing electrodes, wherein when the ambient temperature is 25°C, the crystal system of the single crystal is a tetragonal system, and the crystal orientation of the surface of the single crystal that contacts the electrode surfaces of the opposing electrodes is (110) or (111). The present invention also provides a method for manufacturing a piezoelectric element, comprising: a first preparation step of preparing a matrix and a seed single crystal; a second preparation step of preparing an integrated body in which a surface of the matrix is ​​in contact with a (110) plane or a (111) plane of the seed single crystal; a first heating step of raising the temperature of the integrated body from room temperature to a liquid phase start temperature of the matrix; a second heating step of raising the temperature of the integrated body from the liquid phase start temperature to a liquid phase finish temperature of the matrix; a heating step of heating the integrated body at the liquid phase finish temperature; a step of obtaining a single crystal from the integrated body after heating; a step of arranging opposing electrodes on the single crystal to fabricate a piezoelectric element; and a step of performing a polarization treatment on the piezoelectric element, wherein the heating rate in the second heating step is smaller than the heating rate in the first heating step. The present invention also provides an ultrasonic motor having at least a vibrating body on which the piezoelectric element is disposed and a moving body in contact with the vibrating body. The present invention also relates to an optical device having the ultrasonic motor in a drive section. The present invention also relates to a vibration device having a vibrating body with the piezoelectric element arranged on a vibration plate. The present invention also relates to a dust removal device having the vibration device in a vibration section. The present invention also relates to an imaging device having at least the dust removal device and an imaging element unit, in which the vibration plate of the dust removal device is provided on the light receiving surface side of the imaging element unit. The present invention also relates to an ultrasonic probe having the piezoelectric element and transmitting and receiving by the piezoelectric element. The present invention also relates to an ultrasonic diagnostic device having at least the ultrasonic probe and an image output section. The present invention also relates to an ultrasonic diagnostic system having the ultrasonic probe, a transmitting section that transmits signals output from the ultrasonic probe, and a receiving section that receives signals transmitted from the transmitting section.The present invention also provides an electronic device equipped with a piezoelectric acoustic component having the piezoelectric element.

[0007] According to the present invention, it is possible to obtain a piezoelectric element that simultaneously achieves a high electromechanical coupling coefficient and a high coercive field, which has been difficult to achieve with conventional single crystal materials of perovskite oxides.

[0008] FIG. 1 is a schematic diagram showing one embodiment of the configuration of a piezoelectric element of the present invention. FIG. 2 is a schematic diagram showing one embodiment of the configuration of a piezoelectric element of the present invention. FIG. 3A is a schematic diagram for explaining an example of pole figure measurement of X-ray diffraction of a (100) single crystal constituting a piezoelectric element of the present invention. FIG. 3B is a schematic diagram for explaining another example of pole figure measurement of X-ray diffraction of a (100) single crystal constituting a piezoelectric element of the present invention. FIG. 4A is a schematic diagram for explaining an example of pole figure measurement of X-ray diffraction of a (110) single crystal constituting a piezoelectric element of the present invention. FIG. 4B is a schematic diagram for explaining another example of pole figure measurement of X-ray diffraction of a (110) single crystal constituting a piezoelectric element of the present invention. FIG. 5A is a schematic diagram for explaining an example of pole figure measurement of X-ray diffraction of a (111) single crystal constituting a piezoelectric element of the present invention. FIG. 5B is a schematic diagram for explaining another example of pole figure measurement of X-ray diffraction of a (111) single crystal constituting a piezoelectric element of the present invention. FIG. 6 is a schematic diagram for explaining an example of the dielectric constant temperature characteristics of a piezoelectric element of the present invention. FIG. 7 is a schematic diagram illustrating an example of a PE hysteresis curve of a piezoelectric element of the present invention. FIG. 8A is a schematic diagram illustrating an example of a configuration for producing a single crystal of the present invention. FIG. 8B is a schematic diagram illustrating another example of a configuration for producing a single crystal of the present invention. FIG. 9 is a schematic diagram illustrating another example of a configuration for producing a single crystal of the present invention. FIG. 10 is a schematic diagram illustrating another example of a configuration for producing a single crystal of the present invention. FIG. 11 is a schematic diagram illustrating an embodiment of the configuration of an ultrasonic motor of the present invention. FIG. 12A is a schematic diagram illustrating an embodiment of an optical device of the present invention. FIG. 12B is an enlarged view of the upper right portion of FIG. 12A. FIG. 13 is a schematic diagram illustrating an embodiment of an optical device of the present invention. FIG. 14A is an example of a schematic diagram illustrating an embodiment in which the vibration device of the present invention is used as a dust removal device. FIG. 14B is another example of a schematic diagram illustrating an embodiment in which the vibration device of the present invention is used as a dust removal device. FIGS. 15(a) to 15(c) are schematic diagrams illustrating the configuration of a piezoelectric element in a dust removal device of the present invention. Figures 16(a) and 16(b) are schematic diagrams showing the vibration principle of the dust removing device of the present invention. Figure 17 is a schematic diagram showing an embodiment of the imaging device of the present invention. Figure 18 is a schematic diagram showing an embodiment of the imaging device of the present invention.Fig. 19 is a schematic diagram showing an embodiment of an ultrasonic probe of the present invention. Fig. 20 is a schematic diagram showing an embodiment of an ultrasonic diagnostic apparatus of the present invention. Fig. 21 is a schematic diagram showing an embodiment of an ultrasonic diagnostic system of the present invention. Fig. 22 is a schematic diagram showing an embodiment of an ultrasonic diagnostic system of the present invention. Fig. 23 is a schematic diagram showing an embodiment of an electronic device of the present invention.

[0009] First Embodiment The first embodiment relates to a piezoelectric element. The piezoelectric element of the present invention is a piezoelectric element having a single crystal of a perovskite metal oxide and opposing electrodes, characterized in that, when the ambient temperature is 25°C, the crystal system of the single crystal is tetragonal, and the crystal orientation of the surface of the single crystal that contacts the electrode surfaces of the opposing electrodes is (110) or (111). Hereinafter, embodiments for carrying out the present invention will be described.

[0010] According to the present invention, a single crystal piezoelectric element is provided that simultaneously achieves a high electromechanical coupling coefficient and a high coercive field, which have been difficult to achieve with conventional single crystal perovskite oxide materials. Furthermore, the single crystal element of the present invention can be used in a variety of applications, such as electronic devices, light-emitting elements, optical elements, energy conversion elements, and sensors.

[0011] <Explanation for understanding the invention> (Single crystal) A single crystal, which is a piezoelectric material constituting a piezoelectric element, is made up of a single crystal grain, and the crystal axis, which is the direction of the atomic arrangement, is the same throughout the crystal grain. However, the single crystal of the present invention may contain lattice defects such as dislocations, vacancies, or gaps within the single crystal. It may also contain a domain structure that occurs due to differences in the crystal system caused by phase transition or differences in the direction of spontaneous polarization.

[0012] (Perovskite type) The perovskite type refers to a perovskite structure (also called a perovskite structure) which is ideally a cubic crystal structure, as described in the Iwanami Dictionary of Physics and Chemistry, 5th Edition (Iwanami Shoten, published February 20, 1998). Perovskite type oxides are generally classified into ABO ３The molar ratio of the elements at the A site and B site to the O element is expressed as 1:3, but even if the ratio of the element amounts is slightly different (for example, 1.00:2.94 to 1.00:3.06), the oxide can still be called a perovskite oxide as long as it has a perovskite-type main phase.

[0013] Furthermore, if the coordinates of the elements A, B, and O are slightly shifted from their respective symmetric positions in the unit lattice, the perovskite unit lattice will be distorted, resulting in a crystal system such as a tetragonal, rhombohedral, or rectangular crystal. The single crystal of the present invention is preferably made of a perovskite oxide, but the crystal system of the single crystal can be any crystal system depending on the single or multiple elements that make up A and B. Whether an oxide is perovskite and what its crystal system is can be determined by structural analysis using, for example, X-ray diffraction or electron beam diffraction. In this case, the sample may be powdered before measurement, if necessary.

[0014] <Piezoelectric Element> (Perovskite-Type Oxide Piezoelectric Single Crystal 1) The perovskite-type single crystal, which is the piezoelectric material constituting the piezoelectric element of the present invention, may contain Pb, Mg, Nb, and Ti.

[0015] (Tetragonal System) When the ambient temperature of the piezoelectric element of the present invention is 25° C., the crystal system of the single crystal is tetragonal. The perovskite single crystal may contain a perovskite metal oxide represented by the following general formula (2) as a main component: (1-y)Pb(Mg １／３ Nb ２／３ ) O ３ - yPbTiO ３ (2) When y in the formula is in the range of 0.34≦y≦0.50, single crystals having a tetragonal crystal system can be stably produced at an ambient temperature of 25°C.

[0016] (Perovskite-Type Oxide Piezoelectric Single Crystal 2) The perovskite-type single crystal, which is the piezoelectric material constituting the piezoelectric element of the present invention, may contain Pb, Zn, Nb, and Ti.

[0017] (Tetragonal System) When the ambient temperature of the piezoelectric element of the present invention is 25° C., the crystal system of the single crystal is tetragonal. The perovskite single crystal may contain a perovskite metal oxide represented by the following general formula (3) as a main component: (1-z)Pb(Zn １／３ Nb ２／３ ) O ３ -zPbTiO ３ (3) When z in the formula is in the range of 0.12≦z≦0.20, single crystals having a tetragonal crystal system can be stably produced at an ambient temperature of 25°C.

[0018] (Evaluation of Crystal System and Crystal Orientation) In the piezoelectric element of the present invention, the single crystal is tetragonal at an ambient temperature of 25°C. Furthermore, in the piezoelectric element of the present invention, it is preferable that the crystal system of the perovskite metal oxide is tetragonal when the ambient temperature is 0°C or higher and 60°C or lower. In a tetragonal single crystal, the ratio c / a of the a-axis length to the c-axis length is larger than in other crystal systems, and therefore the spontaneous polarization is larger and the polarization after polarization treatment is also larger. This larger polarization can increase the threshold for changing direction in response to an external electric field. In other words, it can increase the coercive electric field.

[0019] (Perovskite-Type Oxide Piezoelectric Single Crystal 3) In the piezoelectric element of the present invention, the perovskite-type single crystal preferably contains Ba, Ti, and Zr. In the piezoelectric element of the present invention, when the amount of substance (molar ratio) of Zr to the total amount of substance of Ti and Zr is x, it is preferable that 0.01≦x≦0.03. In the piezoelectric element of the present invention, when the amount of substance (molar ratio) of Ba to the total amount of substance of Ti and Zr is α, it is preferable that 0.976≦α≦1.020. In the piezoelectric element of the present invention, the single crystal preferably contains at least Mn and Bi, and the Mn content is 0.0020 to 0.0500 molar parts per 1 molar part of the perovskite metal oxide containing Ba, Ti, and Zr, and the Bi content is 0.0005 to 0.0060 molar parts per 1 molar part of the perovskite metal oxide containing Ba, Ti, and Zr. In the piezoelectric element of the present invention, the crystal system of the single crystal is tetragonal when the ambient temperature is 25°C.

[0020] The perovskite single crystal, which is the piezoelectric body constituting the piezoelectric element of the present invention, comprises a single crystal having a main component containing a perovskite metal oxide represented by the following general formula (1), a first subcomponent consisting of Mn, and a second subcomponent consisting of trivalent Bi, and an opposing electrode, and it is preferable that the content of the Mn is 0.0020 molar parts or more and 0.0500 molar parts or less per 1 molar part of the perovskite metal oxide containing Ba, Ti, and Zr, and the content of the Bi is 0.0005 molar parts or more and 0.0060 molar parts or less per 1 molar part of the perovskite metal oxide containing Ba, Ti, and Zr. α (Ti １－ｘ Zr ｘ ) O ３ (1) When x in the formula is in the range of 0.01≦x≦0.03 and α in the formula is in the range of 0.976≦α≦1.020, single crystals having a tetragonal crystal system can be stably produced at an ambient temperature of 25°C.

[0021] The perovskite oxide containing Ba, Ti, and Zr and the single crystal containing Mn and Bi have piezoelectric properties, and among lead-free piezoelectric materials, they have a high electromechanical coupling coefficient and a high coercive field.

[0022] When using a piezoelectric single crystal in an ultrasonic motor, it is required to have a high electromechanical coupling coefficient and a large coercive electric field. If the electromechanical coupling coefficient is low, the vibration amplitude cannot be obtained and the driving force required for an ultrasonic motor cannot be obtained. In order to increase the driving voltage to obtain the vibration amplitude, a large coercive electric field is required, but if this is low, the vibration amplitude cannot be obtained. Furthermore, when used as an ultrasonic probe, it is required to have a high electromechanical coupling coefficient and a large coercive electric field. A low electromechanical coupling coefficient does not allow wideband transmission and reception characteristics.

[0023] The oxide represented by the general formula (1) means that the element located at the A site is Ba, and the elements located at the B site are Ti and Zr. However, some Ba may be located at the B site. Similarly, some Ti and Zr may be located at the A site. In the general formula (1), the molar ratio of the B site element to the O element is 1:3, but the ratio of the amounts of the elements may be slightly different (for example, 1.00:2.94 to 1.00:3.06).

[0024] In the single crystal of the present invention, in the general formula (1), α, which indicates the ratio of the molar amount of Ba in the A site to the molar amounts of Ti and Zr in the B site, is preferably in the range of 0.976≦α≦1.020.

[0025] The perovskite single crystal that is the piezoelectric material constituting the piezoelectric element of the present invention preferably contains the perovskite oxide represented by the general formula (1) as the main component in an amount of 90 mol % or more, more preferably 95 mol % or more.

[0026] If α is less than 0.976, many voids may occur, resulting in a decrease in strength. On the other hand, if α is greater than 1.020, the grain size of matrix 1 may become too large in the first heating step, making it difficult for the single crystal to expand during heating, and making it difficult to produce the single crystal. The preferred range of α, which reduces voids and makes it easier for the single crystal to expand, is 0.980≦α≦1.000.

[0027] In the general formula (1), x, which indicates the molar ratio of Zr in the B site, is preferably in the range of 0.01≦x≦0.03. If x is greater than 0.03, the crystal system at room temperature (25° C.) is orthorhombic rather than tetragonal, resulting in a small coercive field and insufficient voltage resistance, while if x is less than 0.01, the piezoelectric constant at room temperature is small.

[0028] The means for measuring the composition of the single crystal of the present invention is not particularly limited. Examples of the means include X-ray fluorescence analysis, ICP emission spectroscopy, atomic absorption spectroscopy, etc. Any of the means can calculate the weight ratio and composition ratio of each element contained in the single crystal.

[0029] When the single crystal of the present invention contains 0.0020 to 0.0500 molar parts of Mn per 1 molar part of the metal oxide, the coercive field at room temperature (25°C) is increased. Mn is not limited to metallic Mn, and it may be contained in the single crystal as a Mn component, regardless of the form of inclusion. For example, Mn may be present in the B site as a solid solution or at the interface with voids in the single crystal. Alternatively, the Mn component may be present in the single crystal in the form of metal, ion, oxide, metal salt, complex, or the like. The valence of Mn can generally be 4+, 2+, or 3+. When conduction electrons exist in the crystal (for example, when oxygen vacancies exist in the crystal or when a donor element occupies the A site), the valence of Mn decreases from 4+ to 3+ or 2+, trapping conduction electrons and improving insulation resistance.

[0030] On the other hand, when the valence of Mn is lower than 4+, such as 2+, Mn acts as an acceptor. When Mn exists as an acceptor in a perovskite single crystal, holes are generated in the crystal or oxygen vacancies are formed in the single crystal.

[0031] If the valence of Mn in the sample is 2+ or 3+, the introduction of oxygen vacancies alone will not be enough to compensate for the holes, resulting in a decrease in insulation resistance. Therefore, it is preferable that the majority of Mn is 4+. However, a very small amount of Mn may have a valence lower than 4+ and occupy the B site of the perovskite structure as an acceptor, forming oxygen vacancies. Mn with a valence of 2+ or 3+ and oxygen vacancies form defect dipoles, generating an internal electric field. Polarization treatment can align the direction of the internal electric field along with the spontaneous polarization, contributing to an increase in the effective coercive field.

[0032] Furthermore, in the single crystal of the present invention, the Bi content is 0.0005 to 0.0060 molar parts per 1 molar part of the metal oxide, so that trivalent Bi can occupy the A site, which makes it easier for Mn in the B site to take a valence lower than 4+ in order to achieve charge balance, and allows it to behave as an acceptor.

[0033] The valence of Mn contained in the single crystal of the present invention can be evaluated by measuring the temperature dependence of magnetic susceptibility. Magnetic susceptibility can be measured using a superconducting quantum interference device (SQUID), a vibrating sample magnetometer (VSM), or a magnetic balance. The magnetic susceptibility χ obtained by measurement generally follows the Curie-Weiss law expressed by Equation 4: χ = C / (T-θ) (C: Curie constant, θ: paramagnetic Curie temperature) (4)

[0034] Generally, when a small amount of Mn is added to a non-magnetic material, the spin S=5 / 2 is obtained when the valence is 2+, S=2 when the valence is 3+, and S=3 / 2 when the valence is 4+. Therefore, the Curie constant C converted per unit Mn amount corresponds to the spin S value at each Mn valence. Therefore, the average valence of Mn in a sample can be evaluated by deriving the Curie constant C from the temperature dependence of the magnetic susceptibility χ.

[0035] If the Mn content is less than 0.0020 parts by mole, the coercive field will be as small as less than 1.2 kV / cm at room temperature (25°C). If the coercive field is small, there is a limit to the voltage that can be applied to drive the piezoelectric element, and large vibrations cannot be obtained. In the present invention, the coercive field Ec is preferably 4.0 kV / cm or more, more preferably 6.0 kV / cm or more. The even more preferred coercive field Ec is 8.0 kV / cm or more. The particularly preferred coercive field Ec is 10 kV / cm or more.

[0036] On the other hand, if the Mn content is greater than 0.0500 parts by mole, the insulating properties of the piezoelectric element may actually decrease. For example, the dielectric loss tangent at a frequency of 1 kHz of the single crystal may exceed 0.01, and the resistivity may fall below 1 GΩ cm. The dielectric loss tangent can be measured using an impedance analyzer.

[0037] When the dielectric loss tangent is 0.01 or less, stable operation can be obtained even when a high voltage is applied to the single crystal when used as a piezoelectric element. If the resistivity of the single crystal is 1 GΩcm, it can be polarized and driven as a piezoelectric element. A more preferable resistivity is 50 GΩcm or more.

[0038] (Configuration of Piezoelectric Element) The piezoelectric element of the present invention has a single crystal of a perovskite metal oxide and opposing electrodes. FIG. 1 is a schematic diagram showing one embodiment of the configuration of the piezoelectric element of the present invention. The piezoelectric element of the present invention is a piezoelectric element having at least a first electrode 11, a single crystal 3, and a second electrode 33, and its piezoelectric constant can be evaluated. The first electrode 11 and the second electrode 33 are made of conductive layers with a thickness of approximately 5 nm to 10 μm. The material is not particularly limited, and may be any material commonly used in piezoelectric elements. Examples include metals such as Ti, Pt, Ta, Ir, Sr, In, Sn, Au, Al, Fe, Cr, Ni, Pd, Ag, and Cu, alloys, and compounds thereof.

[0039] (Relationship between Crystal Orientation, Easy Polarization Axis, and Piezoelectricity) When the ambient temperature is 25° C., the piezoelectric element has a single crystal whose crystal system is tetragonal, and the crystal orientation of the surface of the single crystal that contacts the electrode surfaces of the opposing electrodes (the electrode surfaces of the first electrode 11 and the second electrode 33) is (110) or (111). In the piezoelectric element of the present invention, it is preferable that the crystal orientation of the surface of the single crystal that contacts the opposing electrode surfaces is (110), and when the electrode surfaces of the opposing electrodes are taken as the main surfaces of the piezoelectric element, the crystal orientation of the side surface of the piezoelectric element that is located on the longitudinal side of the electrode surfaces is (001).

[0040] By applying a voltage to a piezoelectric element made of tetragonal single crystal with a crystal orientation (110) in the direction of the opposing electrodes and performing the polarization process, the polarization axes become two directions:

[100] and

[010] . By applying a voltage to a piezoelectric element made of tetragonal single crystal with a crystal orientation (111) in the direction of the opposing electrodes and performing the polarization process, the polarization axes become three directions:

[100] ,

[010] , and

[001] .

[0041] By applying a voltage to a piezoelectric element made of a tetragonal single crystal with a crystal orientation (100) in the direction of the opposing electrodes and performing the polarization process, the polarization axis becomes only in the

[001] direction. In the present invention, since the polarization axes are in multiple directions, it is possible for multiple domains to exist at high density, and it is possible to obtain great piezoelectric properties.

[0042] Second Embodiment The second embodiment relates to a method for manufacturing a piezoelectric element. The method for manufacturing a piezoelectric element of the present invention includes: a first preparation step of preparing a matrix and a seed single crystal; a second preparation step of preparing an integrated body in which the surface of the matrix is ​​in contact with the (110) or (111) face of the seed single crystal; a first heating step of raising the temperature of the integrated body from room temperature to the liquid phase start temperature of the matrix; a second heating step of raising the temperature of the integrated body from the liquid phase start temperature to the liquid phase finish temperature of the matrix; a heating step of heating the integrated body at the liquid phase finish temperature; a step of obtaining a single crystal from the integrated body after heating; a step of arranging opposing electrodes on the single crystal to fabricate a piezoelectric element; and a step of performing a polarization treatment on the piezoelectric element. The heating rate in the second heating step is smaller than the heating rate in the first heating step. Each step is described below.

[0043] (Raw Materials for Piezoelectric Material) When producing the single crystal of the present invention, a general method can be used in which a molded body is made from solid powder of an oxide, carbonate, nitrate, oxalate, acetate, or the like containing the constituent elements, and the molded body is sintered under atmospheric pressure. The raw materials are composed of compounds such as Ba compounds, Ti compounds, Zr compounds, and Mn compounds.

[0044] Usable Ba compounds include barium oxide, barium carbonate, barium oxalate, barium acetate, barium nitrate, barium titanate, barium zirconate, etc. It is preferable to use commercially available high-purity Ba compounds (e.g., with a purity of 99.99% or more).

[0045] Usable Ti compounds include titanium oxide, barium titanate, and barium titanate zirconate. When these Ti compounds contain alkaline earth metals such as barium, it is preferable to use commercially available high-purity compounds (e.g., purity of 99.99% or higher). They may contain Nb to the extent that it is contained as an inevitable component in commercially available Ti raw materials, and Hf to the extent that it is contained as an inevitable component in commercially available Zr raw materials.

[0046] Usable Zr compounds include zirconium oxide, barium zirconate, and barium titanate zirconate. When these Zr compounds contain alkaline earth metals such as barium, it is preferable to use commercially available high-purity compounds (e.g., 99.99% or higher purity). Usable Mn compounds include manganese carbonate, manganese oxide, manganese dioxide, manganese acetate, and trimanganese tetroxide.

[0047] Furthermore, the raw material for adjusting α, which indicates the molar ratio of Ba present at the A site and Ti to Zr at the B site of the piezoelectric material according to the present invention, is not particularly limited. The same effect can be obtained with any of Ba compounds, Ti compounds, and Zr compounds.

[0048] (Relative Density) The single crystal piezoelectric body used in the piezoelectric element of the present invention preferably has a relative density of 93% or more and 100% or less. If the relative density is less than 93%, the mechanical strength may decrease. The relative density of the piezoelectric material of the present invention is more preferably in the range of 95% or more and 100% or less, and even more preferably in the range of 97% or more and 100% or less. If the relative density is 95% or more, the material is less likely to break during processing, and if it is 97% or more, chipping during cutting and polishing is reduced.

[0049] In the piezoelectric element of the present invention, the single crystal preferably contains less than 1000 ppm of Pb. This reduces the environmental impact of the piezoelectric element. The amount of Pb contained in the single crystal can be determined by measuring it using ICP atomic emission spectroscopy.

[0050] (Method for producing single crystals by solid phase growth method) A specific method for producing single crystals used in piezoelectric elements of the present invention will be described below. Figures 8A and 8B are schematic diagrams showing one embodiment of an integrated product of a seed single crystal and a matrix of the present invention. In Figure 8A, a seed single crystal 2 is provided on top of a matrix 1, and an integrated product is formed in which the surface of the matrix 1 and the surface of the seed single crystal 2 are in contact with each other. A method for producing a perovskite oxide single crystal of the present invention is, for example, a method for producing a perovskite single crystal by heating a matrix 1 as shown in Figure 8B.

[0051] <First Preparation Step> The method for manufacturing a piezoelectric element of the present invention includes a first preparation step of preparing a matrix and a seed single crystal. The seed single crystal 2 used in the method for manufacturing a perovskite single crystal of the present invention may be a bulk or a thin film, but is preferably a bulk with a thickness of 10 μm or more in terms of high strength, because stress may be generated in the seed single crystal 2 due to a mismatch in lattice constant or a difference in thermal expansion between the matrix 1 and the seed single crystal 2 in the region in contact with the matrix 1, which may cause breakage. In addition, it is preferable that the matrix 1 and the seed single crystal 2 have approximately the same composition.

[0052] The seed single crystal 2 may be prepared by selecting from commercially available oxide single crystals, semiconductor single crystals, fluoride / alkali halide single crystals, metal single crystals, alloy single crystals, etc., but a perovskite-type single crystal is preferable because it is less likely to generate stress due to a mismatch in lattice constant with the matrix 1 or a difference in thermal expansion.

[0053] The perovskite single crystal used as the seed single crystal 2 is BaTiO ３ , BaZrO ３ , SrTiO ３ , CaTiO ３ , Pb(Mg １／３ Nb ２／３ ) O ３ , KTaO ３ , KNbO ３ , SrRuO ３ , LiNbO ３ , LaNiO ３ , AgNbO ３ , CdTiO ３and solid solutions thereof. The seed single crystal 2 used in the production method of the present invention may be a single crystal obtained by the production method of the present invention.

[0054] (Explanation of Matrix) The matrix 1 of the present invention is a molded body or a sintered body, and the shape of the matrix 1 is not particularly limited. However, a shape with a flat surface, such as a rectangular parallelepiped or a disk, is preferred because it can be easily placed in contact with the seed single crystal 2.

[0055] The process for preparing the matrix will be described below. (Raw material powder for preparing the matrix) The raw material used for the matrix 1 of the present invention is a solid powder of oxide, carbonate, nitrate, oxalate, or the like containing the constituent elements of the single crystal of the present invention, or a mixed powder of these. In this case, if the main component of the single crystal is not a lead-based material, it is more preferable that the lead (Pb) content in the raw material is less than 1000 ppm, as this reduces the burden on the environment.

[0056] Preferred elements constituting the raw materials include, for example, Li, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Zn, Ge, Sr, Y, Zr, Nb, Mo, Sn, Sb, Ba, Hf, Ta, Bi, La, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Yb.

[0057] The raw materials may be heat-treated for the purpose of homogenization, or may be crushed after the heat treatment. The heat treatment for homogenizing the raw materials is preferably carried out in the range of 800°C to 1300°C, since crushing after the heat treatment is easy.

[0058] (Growth Promoters Promoting Single Crystallization of Matrix) In addition to the solid powder containing the constituent elements for forming a single crystal or the mixed powder thereof, a compound that promotes single crystallization by solid phase growth may be added to the matrix 1 of the present invention. Examples of the promoting compound include lithium carbonate, silicon oxide, and aluminum oxide. Preferably, lithium carbonate is added in an amount of 3 to 7 molar parts per mole of the perovskite metal oxide, which is the main component of the matrix 1.

[0059] (Granulation of raw materials for preparing a matrix) The raw materials for matrix 1 used in the method for producing a single crystal of the present invention may be granulated, and the granulation method is not particularly limited. Examples of binders that can be used during granulation include PVA (polyvinyl alcohol), PVB (polyvinyl butyral), and acrylic resins. The amount of binder added to the mixed powder is preferably 1 to 10 parts by weight, and more preferably 2 to 5 parts by weight from the viewpoint of increasing the density of the molded body. From the viewpoint of making the particle size of the granulated powder more uniform, the most preferred granulation method is spray drying.

[0060] (Molded body of raw material for preparing matrix) The molded body of matrix 1 used in the method for producing a single crystal of the present invention is a molded body obtained by compacting the above-mentioned raw materials into a desired shape, and the method for producing the molded body is not particularly limited. The molded body is a solid body produced from raw material powder, granulated powder (binder), or slurry.

[0061] Methods for producing a molded body include uniaxial pressing, cold isostatic pressing, warm isostatic pressing, slip casting, and extrusion. Alternatively, the raw material in a slurry state may be formed into a sheet using a doctor blade method, dried, and the sheets may be stacked and molded into the desired shape. It is preferable to perform a degassing step before drying the sheet, as this increases the density, thereby increasing the density of the matrix 1 using the sheet and also increasing the density of the single crystal produced using the matrix 1.

[0062] In the method for producing a single crystal of the present invention, the matrix 1 is preferably a molded body. In this case, too, as shown in Fig. 8A , a seed single crystal 2 is placed on the matrix 1, and the matrix 1 and the seed single crystal 2 are arranged in contact with each other. When heat treatment is performed in this state, the matrix 1 shrinks and the seed single crystal 2 slightly bites into the matrix 1, so that the matrix 1 and the seed single crystal 2 are in closer contact with each other. In other words, the contact area between the matrix 1 and the seed single crystal 2 increases.

[0063] Although there is a method of placing the seed single crystal 2 in the molded body during molding, there is a risk of significant deformation or breakage or cracks occurring during heat treatment due to the difference in the amount of shrinkage between the molded body and the seed single crystal 2. Therefore, when the matrix 1 is a molded body, it is preferable to place the seed single crystals 2 in contact with each surface of the matrix 1.

[0064] When placing the seed single crystal 2, it is necessary to align in advance the crystal orientation of the surface of the seed single crystal 2 that contacts the matrix 1 with the crystal orientation of the desired single crystal. For this purpose, the seed single crystal 2 is oriented using an X-ray diffraction pole figure or the Laue method, and polished in the desired orientation to obtain a surface that is the surface of the seed single crystal that contacts the matrix.

[0065] The matrix 1 and the seed single crystal 2 are preferably arranged one above the other so as to be in contact with each other. Furthermore, it is preferable to place a weight on the matrix 1 and the seed single crystal 2, since this facilitates contact between the matrix 1 and the seed single crystal 2. Even if a force acts in a direction that separates the matrix 1 and the seed single crystal 2 due to deformation during heat treatment or the like, the weight acts in a direction that suppresses this force, making it easier for them to come into contact with each other.

[0066] The area of ​​the face of the seed single crystal 2 on the side where it contacts the matrix 1 is preferably equal to or less than the area of ​​the face of the matrix 1 on the side where it contacts the seed single crystal 2. The portion of the seed single crystal 2 that is larger than the matrix 1 is wasted because it does not contribute to the single crystallization of the matrix 1. However, since the heat treatment time required to expand the single crystal region to the entire matrix becomes long, the area of ​​the face of the seed single crystal 2 on the side where it contacts the matrix 1 is preferably 50% to 100% of the area of ​​the face of the matrix 1 on the side where it contacts the seed single crystal 2.

[0067] (Sintering) When matrix 1 is used as a sintered body, the molded body may be sintered by any means, and examples of the sintering method include sintering in an electric furnace, sintering in a gas furnace, hot pressing, resistance heating, microwave sintering, millimeter wave sintering, HIP (hot isostatic pressing), and flash sintering. Hot pressing, resistance heating, and HIP, which generate high pressure at high temperatures, are preferred because they can reduce the size or number of voids in the matrix. A smaller volume of voids in the matrix is ​​preferred because it increases the density of the single crystal obtained from that matrix 1.

[0068] The relative density of the matrix 1 is preferably 93% or more and 100% or less. When the relative density of the matrix 1 is 93% or more and 100% or less, the density of the single crystal obtained from the matrix 1 also becomes high.

[0069] The relative density is the ratio of the theoretical density calculated from the lattice constant of the piezoelectric material and the atomic weight of the constituent elements of the piezoelectric material to the measured density. The lattice constant can be measured, for example, by X-ray diffraction analysis. The density can be measured, for example, by the Archimedes method.

[0070] When the ratio of the measured density (ρ meas.) to the theoretical density (ρ calc.) determined from the composition and lattice constant of the sintered body, that is, the relative density (ρ calc. / ρ meas.), is 93% or more, the relative density can be said to be sufficiently high.

[0071] (Crystal orientation alignment) The single crystal obtained by sintering as described above is subjected to a process of measuring the crystal orientation using pole figures of X-ray diffraction or the Laue method, and then the front and back surfaces are polished to achieve the desired orientation. Polishing methods include mechanical polishing, chemical polishing, and CMP polishing, and these may be combined for polishing.

[0072] Mechanical polishing refers to polishing using a machine, and when mechanical polishing is performed, a polishing machine, lapping machine, polishing machine, or buffing machine may be selected and used. A process using a precision grinding machine with a fine grinding stone can also be used as the polishing process.

[0073] Chemical polishing is a polishing method in which a sample is immersed in a polishing solution and the surface of the sample is corroded by a chemical reaction using the power of acid or alkali. For example, a rotary polishing method is used in which a polishing pad is attached to a disc-shaped surface plate, and a liquid abrasive containing chemical components and fine particles is dripped onto the pad and polished while rotating.

[0074] CMP polishing is a technique that combines mechanical polishing and chemical polishing, and it is a method that flattens the surface by not only using the mechanical action of abrasive grains to scrape the surface of the sample, but also by using chemical reactions between the abrasive grains and the sample, and between the polishing liquid and grinding liquid, and by using these physical polishing and chemical reactions. Mirror surfaces can be created by chemical polishing and CMP polishing.

[0075] When preparing matrix 1 as a sintered body, it is preferable to sinter it at a temperature that prevents the crystal grains from becoming too large during sintering. As a means for preventing the crystal grains from becoming too large, a method of sintering in a reducing atmosphere such as nitrogen or argon during heating may be used. When matrix 1 is used as a sintered body, the crystal grain size of matrix 1 is preferably 50 μm or less, more preferably 10 μm or less.

[0076] Here, "particle size" refers to what is generally called "projected area circle equivalent diameter" in microscopic observation, and refers to the diameter of a perfect circle having the same area as the projected area of ​​a crystal grain. In the present invention, there are no particular limitations on the method for measuring particle size. For example, the particle size can be determined by image processing of a photographic image obtained by photographing the surface of a sample using a polarizing microscope or a scanning electron microscope. Since the optimal magnification differs depending on the particle size of interest, an optical microscope and an electron microscope may be used interchangeably. The circle equivalent diameter may also be determined from an image of a polished surface or cross section of the sample rather than from the surface.

[0077] <Second Preparation Step> The method for producing a piezoelectric element of the present invention includes a second preparation step of preparing an integral body in which the surface of the matrix and the (110) or (111) plane of the seed single crystal are arranged in contact with each other.

[0078] (Heating Method) There are no particular limitations on the method for heating the integral body of the matrix 1 and the seed single crystal 2, but sintering in an electric furnace is preferred in that it allows heating a large number of bodies at once and reduces production costs.

[0079] (Sagger, setter, beads, weight) Figures 8A, 8B, 9, and 10 are examples of schematic diagrams showing the configuration for producing a single crystal of the present invention. In Figure 8B, a weight 4 is placed on an integral body of a matrix 1 and a seed single crystal 2, and the integral body is placed on a setter 6 via beads 5. Figure 9 shows these placed in a sagger 7, and Figure 10 shows the sagger 7 of Figure 9 with a lid 8 attached, which is placed in an electric furnace and heated.

[0080] When the matrix 1 is heated, it is preferable to heat-treat the matrix 1 and the seed single crystal 2 in a sagger 7, and a box-type sagger with a lid is preferable because it is less susceptible to the effects of furnace contamination.

[0081] The matrix 1 and the seed single crystal 2 may be placed on a setter 6 that is less reactive with the matrix 1 or the seed single crystal 2 and then heat-treated. The material of the setter 6 may be, for example, alumina, zirconia, alumina with a zirconia surface coating, stabilized zirconia, silicon carbide, silicon nitride, or the like. Beads 5 such as stabilized zirconia, powder obtained by sintering and pulverizing the matrix 1 at high temperature, or a platinum sheet may be placed on the setter 6, and the matrix 1 and the seed single crystal 2 may then be placed on top of them. If it is difficult to determine whether a material is less reactive, it is sufficient to actually test each material and select the one that leaves the least traces when heated.

[0082] Although there is a method of placing the seed single crystal 2 in the molded body during molding, there is a risk of significant deformation or breakage or cracks occurring during heat treatment due to the difference in the amount of shrinkage between the molded body and the seed single crystal 2. Therefore, when the matrix 1 is a molded body, it is preferable to place the seed single crystals 2 in contact with each surface of the matrix 1.

[0083] When placing a seed single crystal, it is necessary to align the crystal orientation of the surface of the seed single crystal that comes into contact with the matrix with the crystal orientation of the desired single crystal in advance. To this end, the seed single crystal is oriented using an X-ray diffraction pole figure or the Laue method, and then polished in the desired orientation to obtain a surface that is the surface of the seed single crystal that comes into contact with the matrix.

[0084] The matrix 1 and the seed single crystal 2 are preferably arranged one above the other so as to be in contact with each other. Furthermore, it is preferable to place a weight on the matrix 1 and the seed single crystal 2, since this facilitates contact between the matrix 1 and the seed single crystal 2. Even if a force acts in a direction that separates the matrix 1 and the seed single crystal 2 due to deformation during heat treatment or the like, the weight acts in a direction that suppresses this force, making it easier for them to come into contact with each other.

[0085] The area of ​​the face of the seed single crystal 2 on the side where it contacts the matrix 1 is preferably equal to or less than the area of ​​the face of the matrix 1 on the side where it contacts the seed single crystal 2. The portion of the seed single crystal 2 that is larger than the matrix 1 is wasted because it does not contribute to the single crystallization of the matrix 1. However, since the heat treatment time required to expand the single crystal region to the entire matrix becomes long, the area of ​​the face of the seed single crystal 2 on the side where it contacts the matrix 1 is preferably 50% to 100% of the area of ​​the face of the matrix 1 on the side where it contacts the seed single crystal 2.

[0086] <First Heating Step> The method for manufacturing a piezoelectric element of the present invention includes a first heating step in which the integrated body is heated from room temperature to the liquidus start temperature of the matrix. In the first heating step in which the temperature is raised to the liquidus start temperature, crystal grains grow substantially uniformly within the matrix. As described above, if the crystal grains of matrix 1 become too large, it becomes difficult for matrix 1 to be incorporated into the single crystal. Therefore, it is preferable to set the first heating step to a short time so that the crystal grains do not become too large.

[0087] The method for producing a piezoelectric element of the present invention includes a second heating step of heating the integrated body from the liquid phase start temperature to the liquid phase end temperature of the matrix. In addition, in the method for producing a piezoelectric element of the present invention, the heating rate in the second heating step is smaller than the heating rate in the first heating step.

[0088] In the second heating step, the interface between the seed single crystal 2 and the matrix 1 becomes liquid, and the single crystal interface spreads toward the matrix 1. However, if the temperature varies depending on the location due to differences in the orientation of the crystal grains of the matrix 1 in contact with the seed single crystal 2, the interfaces of the crystal grains with different orientations in the matrix 1 also spread at the same time, and it may not be possible to obtain a single crystal that is a single crystal grain.

[0089] Therefore, by reducing the temperature increase rate from the liquid phase start temperature to the liquid phase finish temperature in the second temperature increase step compared to the rate from room temperature to the liquid phase start temperature in the first temperature increase step, it is possible to spread a single crystal consisting of a single crystal grain from the seed single crystal 2. By maintaining the temperature at the liquid phase finish temperature after the temperature increase, it is possible to further increase the size of the single crystal spread from the seed single crystal 2.

[0090] <Heating Step> The method for manufacturing a piezoelectric element of the present invention includes a heating step of heating the integrated body at a liquid phase finish temperature. If the atmosphere during heating contains oxygen, the liquid phase spreads more easily, allowing for the production of large single crystals more quickly. Therefore, it is preferable that the atmosphere during heating contains oxygen.

[0091] <Step of Obtaining Single Crystal> Next, a description will be given of the step of obtaining a perovskite single crystal from the heated matrix 1 after the second heating step. The method for manufacturing a piezoelectric element of the present invention includes the step of obtaining a single crystal from the heated integral body.

[0092] After the second heating step, the regions in the matrix that are single crystals can be determined by checking with a microscope whether there are grain boundaries. If there are no grain boundaries, the matrix is ​​a single crystal consisting of a single crystal grain. This can also be confirmed by structural analysis using X-ray diffraction or electron beam diffraction.

[0093] Only the single crystal region can be obtained by removing the polycrystalline portion other than the single crystal region and the seed single crystal 2 portion using a wire saw, a dicing saw, water jet cutting, electrical discharge machining, laser machining, polishing, etc. A single crystal can also be obtained from the matrix 1 by a similar method when the matrix is ​​held at the liquid phase finish temperature for a certain period of time after the second heating step.

[0094] <Step of Fabricating Piezoelectric Element> The method for fabricating a piezoelectric element of the present invention includes a step of arranging opposing electrodes on a single crystal to fabricate a piezoelectric element. FIG. 1 is a schematic diagram showing one embodiment of the configuration of a piezoelectric element of the present invention. The piezoelectric element of the present invention is a piezoelectric element having at least a first electrode 11, a single crystal 3, and a second electrode 33, and its piezoelectric constant can be evaluated. The first electrode 11 and the second electrode 33 are made of conductive layers with thicknesses of approximately 5 nm to 10 μm. Materials for the electrodes are not particularly limited, and may be any material commonly used in piezoelectric elements. Examples include metals such as Ti, Pt, Ta, Ir, Sr, In, Sn, Au, Al, Fe, Cr, Ni, Pd, Ag, and Cu, alloys, and compounds thereof.

[0095] The first electrode 11 and the second electrode 33 may be made of one of these materials or may be made by laminating two or more of these materials. Also, the first electrode 11 and the second electrode 33 may be made of different materials.

[0096] The manufacturing method of the first electrode 11 and the second electrode 33 is not limited, and they may be formed by baking a metal paste, or by sputtering, vapor deposition, etc. Furthermore, both the first electrode 11 and the second electrode 33 may be patterned into a desired shape before use.

[0097] <Polarization step> The method for manufacturing a piezoelectric element of the present invention includes a step of poling a piezoelectric element. It is more preferable that the piezoelectric element has a polarization axis aligned in a certain direction. The polarization axis aligned in a certain direction increases the piezoelectric constant of the piezoelectric element.

[0098] The polarization method of the piezoelectric element is not particularly limited. The polarization treatment may be performed in the air or in silicone oil. The temperature during polarization is preferably a temperature at which the single crystal undergoes a phase transition. For example, a temperature of 60°C to 150°C is preferable, but the optimal conditions vary somewhat depending on the composition of the single crystal constituting the element. The electric field applied for polarization treatment is preferably 8 kV / cm to 20 kV / cm, and it is preferable to terminate the application of the electric field after lowering the environmental temperature to a temperature at which the single crystal has the same crystal structure as at room temperature, in order to obtain a good piezoelectric constant.

[0099] <Evaluation Method> Some evaluation methods in the present invention are described below. (Evaluation of Crystal Orientation) Crystal orientation can be evaluated by X-ray diffraction. For example, pole figure measurement can be used to evaluate whether the desired crystal orientation is aligned with the measurement surface or by how many degrees it is tilted. The tilt between the desired orientation and the measurement surface orientation is preferably within 2 degrees. If it is within 2 degrees, the influence on the electromechanical coupling coefficient and the coercive field is small. If it is greater than 2 degrees, the electromechanical coupling coefficient and the coercive field decrease rapidly. It is more preferable that the tilt between the desired orientation and the measurement surface orientation is within 1 degree. If it is within 1 degree, a more highly reproducible electromechanical coupling coefficient and coercive field can be obtained.

[0100] (Measurement of Phase Transition Temperature) The phase transition temperature Tot of the piezoelectric element between the tetragonal system and the orthorhombic system is ３１ When the measurement temperature was raised from a low temperature to the Curie temperature Tc or higher using an element, the temperature at which the dielectric constant took a maximum value, which appeared at a temperature lower than the Curie temperature Tc, was determined.

[0101] (Measurement of Electromechanical Coupling Coefficient) To measure the electromechanical coupling coefficient of the piezoelectric element, first, measurements of the resonance frequency and antiresonance frequency are obtained using a commercially available impedance analyzer (4294A manufactured by Agilent Technologies). The measurement results can then be used to calculate the electromechanical coupling coefficient based on the Japan Electronics and Information Technology Industries Association standard (JEITA EM-4501). Hereinafter, this method will be referred to as the resonance-antiresonance method.

[0102] The electromechanical coupling coefficient of the piezoelectric element of the present invention is k ３１The electromechanical coupling coefficient of the piezoelectric element is preferably k ３１ When the ratio is 30% or more, the driving efficiency is high for devices using bending modes such as ultrasonic motors, and therefore a piezoelectric element with low power consumption is realized.

[0103] The electromechanical coupling coefficient of the piezoelectric element of the present invention is k ３３ The electromechanical coupling coefficient of the piezoelectric element is preferably k ３３ When the dielectric constant is 67% or more, the driving efficiency is high for a device using a longitudinal vibration mode such as an ultrasonic probe, and therefore a piezoelectric element with low power consumption is realized.

[0104] The electromechanical coupling coefficient of the piezoelectric element of the present invention is k' ３３ The electromechanical coupling coefficient k' of the piezoelectric element is preferably 62% or more. ３３ When k is 62% or more, ３３ Similarly, since the driving efficiency is high for devices that use longitudinal vibration modes such as ultrasonic probes, it is possible to realize piezoelectric elements with low power consumption.

[0105] (PE Hysteresis and Coercive Field Evaluation) A ferroelectric / piezoelectric evaluation system (LCII manufactured by Radiant Technologies, Inc.) can be used to evaluate the coercive field. In the hysteresis measurement mode, the electric field when the polarization amount was 0 was read from the PE hysteresis curve obtained from the polarization amount with respect to the electric field, and this value was taken as the coercive field.

[0106] (Piezoelectric Element Performance Index) The electromechanical coupling coefficient k' is used as a performance index showing that the piezoelectric element of the present invention achieves both low power consumption due to high driving efficiency and large amplitude performance. ３３ and the product of the coercive field Ec (k' ３３ As a piezoelectric element that exhibits low power consumption and large amplitude performance, k' ３３ It is preferable that k' × Ec exceeds 200. More preferably, k' ３３ ×Ec is 360.

[0107] <<Application Examples>> Application examples of the present invention include ultrasonic motors, optical devices, vibration devices, dust removal devices, imaging devices, ultrasonic probes, ultrasonic diagnostic devices, ultrasonic diagnostic systems, and electronic devices. These are described below.

[0108] (Ultrasonic motor) The ultrasonic motor of the present invention has at least a vibrating body on which the above-mentioned piezoelectric element is arranged, and a moving body in contact with the vibrating body. Fig. 11 is a schematic diagram showing one embodiment of the configuration of the ultrasonic motor of the present invention. Fig. 11 shows an ultrasonic motor in which the piezoelectric element of the present invention is made of a single plate.

[0109] The ultrasonic motor has a vibrator 201, a rotor 202 that is in contact with the sliding surface of the vibrator 201 by the pressure of a pressure spring (not shown), and an output shaft 203 that is provided integrally with the rotor 202. The vibrator 201 is composed of a metal elastic ring 2011, a piezoelectric element 2012 of the present invention, and an organic adhesive 2013 (epoxy-based, cyanoacrylate-based, etc.) that bonds the piezoelectric element 2012 to the elastic ring 2011. The piezoelectric element 2012 of the present invention is composed of a single crystal sandwiched between a first electrode 11 and a second electrode 33 (not shown).

[0110] When a two-phase alternating voltage with a phase difference of an odd multiple of π / 2 is applied to the piezoelectric element of the present invention, a flexural traveling wave is generated in the vibrator 201, and each point on the sliding surface of the vibrator 201 moves elliptically. When the rotor 202 is pressed against the sliding surface of the vibrator 201, the rotor 202 receives a frictional force from the vibrator 201 and rotates in the opposite direction to the flexural traveling wave. A driven body (not shown) is joined to the output shaft 203 and is driven by the rotational force of the rotor 202.

[0111] When a voltage is applied to a single crystal, it expands and contracts due to the piezoelectric transverse effect. The efficiency of this conversion from electrical energy to mechanical energy depends on the magnitude of the electromechanical coupling coefficient. When an elastic material such as metal is bonded to a piezoelectric element with an adhesive, the elastic material is bent by the expansion and contraction of the single crystal via the adhesive. The type of ultrasonic motor described here utilizes this principle.

[0112] (Optical Apparatus) Next, the optical apparatus of the present invention will be described. The optical apparatus of the present invention includes the ultrasonic motor in its drive section. Figures 12A and 12B are cross-sectional views of the main parts of an interchangeable lens barrel for a single-lens reflex camera, which is an example of a preferred embodiment of the optical apparatus of the present invention. Also, Figure 13 is an exploded perspective view of an interchangeable lens barrel for a single-lens reflex camera, which is an example of a preferred embodiment of the optical apparatus of the present invention. A fixed barrel 712, a linear guide barrel 713, and a front-group barrel 714 that can house a front-group lens 701 are fixed to a detachable mount 711 for the camera. These are fixed members of the interchangeable lens barrel.

[0113] The linear guide barrel 713 is formed with a linear guide groove 713a in the optical axis direction for the focus lens 702. Cam rollers 717a and 717b protruding radially outward are fixed to a rear group barrel 716 that holds the focus lens 702 with axial screws 718, and the cam roller 717a fits into the linear guide groove 713a.

[0114] A cam ring 715 is rotatably fitted onto the inner periphery of the linear guide barrel 713. Relative movement between the linear guide barrel 713 and the cam ring 715 in the optical axis direction is restricted by a roller 719 fixed to the cam ring 715 fitting into a circumferential groove 713b of the linear guide barrel 713. A cam groove 715a for the focus lens 702 is formed in this cam ring 715, and the above-mentioned cam roller 717b is fitted into the cam groove 715a at the same time.

[0115] A rotation transmission ring 720 is arranged on the outer periphery of the fixed barrel 712, and is held in a fixed position and rotatable relative to the fixed barrel 712 by a ball race 727. In the rotation transmission ring 720, rollers 722 are rotatably held on shafts 720f extending radially from the rotation transmission ring 720, and large diameter portions 722a of the rollers 722 contact the mount side end surface 724b of the manual focus ring 724. In addition, small diameter portions 722b of the rollers 722 contact the joining member 729. Six rollers 722 are arranged at equal intervals on the outer periphery of the rotation transmission ring 720, and each roller is configured as described above.

[0116] A low-friction sheet (washer member) 733 is disposed on the inner diameter portion of the manual focus ring 724, and this low-friction sheet 733 is sandwiched between the mount-side end face 712a of the fixed barrel 712 and the front end face 724a of the manual focus ring 724. The outer diameter surface of the low-friction sheet 733 is ring-shaped and fits radially into the inner diameter 724c of the manual focus ring 724, which in turn fits radially into the outer diameter portion 712b of the fixed barrel 712. 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 barrel 712 around the optical axis.

[0117] The large-diameter portion 722a of the roller 722 and the mount-side end surface 724b of the manual focus ring 724 are in contact with each other under pressure due to the force of the wave washer 726 pressing the ultrasonic motor 725 toward the front of the lens. Similarly, the small-diameter portion 722b of the roller 722 and the joining member 729 are also in contact with each other under moderate pressure due to the force of the wave washer 726 pressing the ultrasonic motor 725 toward the front of the lens.

[0118] Movement of the wave washer 726 toward the mount is restricted by washer 732, which is bayonet-connected to the fixed barrel 712, and the spring force (biasing force) generated by the wave washer 726 is transmitted to the ultrasonic motor 725 and further to the rollers 722, and also acts as a force pressing the manual focus ring 724 against the mount-side end face 712a of the fixed barrel 712. In other words, the manual focus ring 724 is assembled in a state where it is pressed against the mount-side end face 712a of the fixed barrel 712 via the low-friction sheet 733.

[0119] Therefore, when the ultrasonic motor 725 is driven to rotate relative to the fixed barrel 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, causing the roller 722 to rotate around the center of the shaft 720f. When the roller 722 rotates around the shaft 720f, the rotation transmission ring 720 rotates around the optical axis (autofocus operation).

[0120] Furthermore, when a rotational force about the optical axis is applied to the manual focus ring 724 from a manual operation input unit (not shown), the mount-side end surface 724b of the manual focus ring 724 is in pressure contact with the large-diameter portion 722a of the roller 722, causing the roller 722 to rotate about the shaft 720f due to friction. When the large-diameter portion 722a of the roller 722 rotates about the shaft 720f, the rotation transmission ring 720 rotates about the optical axis. At this time, the ultrasonic motor 725 does not rotate due to the frictional holding force between the rotor 725c and the stator 725b (manual focus operation).

[0121] Two focus keys 728 are attached to the rotation transmission ring 720 at positions facing each other, and the focus keys 728 fit into notches 715b provided at the tip of the cam ring 715. Therefore, when autofocusing or manual focusing is performed and the rotation transmission ring 720 is rotated around the optical axis, the rotational force is transmitted to the cam ring 715 via the focus keys 728.

[0122] When the cam ring 715 is rotated around the optical axis, the rear group barrel 716, whose rotation is restricted by the cam rollers 717a and the linear guide grooves 713a, is moved forward and backward by the cam rollers 717b along the cam grooves 715a of the cam ring 715. This drives the focus lens 702, and a focusing operation is performed.

[0123] Here, the optical device of the present invention has been described as an interchangeable lens barrel for a single-lens reflex camera, but the present invention can also be applied to optical devices that have an ultrasonic motor in the drive section, regardless of the type of camera, such as compact cameras, electronic still cameras, and camera-equipped personal digital assistants.

[0124] (Vibration Device and Dust Removal Device) Vibration devices used for transporting and removing particles, powder, and droplets are widely used in electronic devices and the like. Below, a dust removal device using the piezoelectric element of the present invention will be described as an example of the vibration device of the present invention. The vibration device of the present invention has a vibrating body in which the piezoelectric element or the laminated piezoelectric element is arranged on a vibration plate. The dust removal device of the present invention has the vibration device in its vibration section.

[0125] 14A and 14B are schematic diagrams showing one embodiment of a dust removal device of the present invention. Dust removal device 310 is composed of a plate-shaped piezoelectric element 330 and a vibration plate 320. The material of vibration plate 320 is not limited, but when dust removal device 310 is used in an optical device, a light-transmitting material or a light-reflective material can be used for vibration plate 320.

[0126] Figures 15(a) to (c) are schematic diagrams showing the configuration of the piezoelectric element 330 in Figure 14A. Figures 15(a) and (c) show the configuration of the front and back surfaces of the piezoelectric element 330, and Figure 15(b) shows the configuration of the side surface. As shown in Figure 14A, the piezoelectric element 330 is composed of a single crystal 331, a first electrode 332, and a second electrode 333, and the first electrode 332 and the second electrode 333 are arranged to face the plate surface of the single crystal 331.

[0127] In (c) of Figure 15, the surface on which the first electrode 332 protruding in front of the piezoelectric element 330 is installed is referred to as the first electrode surface 336, and in (a) of Figure 15, the surface on which the second electrode 333 protruding in front of the piezoelectric element 330 is installed is referred to as the second electrode surface 337.

[0128] Here, the electrode surface in the present invention refers to the surface of the piezoelectric element on which the electrode is provided, and for example, the first electrode 332 may extend around to the second electrode surface 337 as shown in FIG. 15(b).

[0129] As shown in Figures 14A and 14B, the piezoelectric element 330 and the diaphragm 320 are fixed to the plate surface of the diaphragm 320 by the first electrode surface 336 of the piezoelectric element 330. When the piezoelectric element 330 is driven, stress is generated between the piezoelectric element 330 and the diaphragm 320, causing out-of-plane vibration in the diaphragm. The dust removal device 310 of the present invention is a device that removes foreign matter such as dust adhering to the surface of the diaphragm 320 by the out-of-plane vibration of the diaphragm 320. The out-of-plane vibration refers to elastic vibration that displaces the diaphragm in the optical axis direction, i.e., in the thickness direction of the diaphragm.

[0130] Figures 16(a) and (b) are schematic diagrams showing the vibration principle of the dust removal device 310 of the present invention. Figure 16(a) shows a state in which an alternating voltage of the same phase is applied to a pair of left and right piezoelectric elements 330, causing out-of-plane vibration in the vibration plate 320. The polarization direction of the single crystals constituting the pair of left and right piezoelectric elements 330 is the same as the thickness direction of the piezoelectric elements 330, and the dust removal device 310 is driven in a seventh vibration mode.

[0131] 16(b) shows a state in which anti-phase alternating voltages, 180° out of phase, are applied to a pair of left and right piezoelectric elements 330, generating out-of-plane vibrations in diaphragm 320. Dust removal device 310 is driven in a sixth vibration mode. Dust removal device 310 of the present invention is a device that can effectively remove dust adhering to the surface of the diaphragm by selectively using at least two vibration modes.

[0132] (Imaging Device) Next, an imaging device of the present invention will be described. The imaging device of the present invention includes at least the dust removal device and an imaging element unit, and the diaphragm of the dust removal device is provided on the light receiving surface side of the imaging element unit. Figures 17 and 18 are diagrams showing a digital single-lens reflex camera as an example of a preferred embodiment of the imaging device of the present invention.

[0133] Fig. 17 is a front perspective view of the camera body 601 as viewed from the subject side, showing the state in which the photographing lens unit is removed. Fig. 18 is an exploded perspective view showing the schematic internal configuration of the camera, for explaining the peripheral structure of the dust removal device and the imaging unit 400 of the present invention.

[0134] A mirror box 605 is provided within the camera body 601 to which the photographing light beam that has passed through the photographing lens is directed, and a main mirror (quick return mirror) 606 is disposed within the mirror box 605. The main mirror 606 can be held at an angle of 45° with respect to the photographing optical axis to direct the photographing light beam toward a pentagonal roof mirror (not shown), or held in a position away from the photographing light beam to direct it toward an image sensor (not shown).

[0135] On the subject side of main body chassis 300, which forms the framework of the camera body, are arranged, in order from the subject side, a mirror box 605 and a shutter unit 200. Furthermore, on the photographer side of main body chassis 300, an imaging unit 400 is arranged. Imaging unit 400 is installed such that the imaging surface of the imaging element is spaced a predetermined distance from, and adjusted to be parallel to, the attachment surface of mount portion 602, which serves as the reference for attaching the photographing lens unit.

[0136] Although a digital single-lens reflex camera has been described as the imaging device of the present invention, it may also be a camera with an interchangeable taking lens unit, such as a mirrorless digital single-lens camera that does not have a mirror box 605. The present invention may also be applied to various imaging devices or electronic and electrical devices equipped with imaging devices, such as video cameras with interchangeable taking lens units, copiers, facsimiles, and scanners, which require the removal of dust adhering to the surfaces of optical components in particular.

[0137] (Ultrasonic Probe) Next, the ultrasonic probe of the present invention will be described. The ultrasonic probe of the present invention has the above-described piezoelectric element and transmits and receives waves using the piezoelectric element. Fig. 19 is a schematic cross-sectional view showing one embodiment of the ultrasonic probe of the present invention. The ultrasonic probe 1100 of Fig. 19 is composed of piezoelectric elements 1101, a backing material 1102, an acoustic matching layer 1103, and an acoustic lens 1104. As shown in Fig. 19, a plurality of piezoelectric elements 1101 are arranged and bonded on the backing material 1102, and an acoustic matching layer 1103 for matching acoustic impedance is provided on the opposite surface, which serves as the transmitting and receiving surface.

[0138] Acoustic matching layer 1103 may be a single layer or multiple layers, preferably two or more layers. Materials that can be used for acoustic matching layer 1103 include, for example, carbon, aluminum, aluminum alloys (e.g., Al-Mg alloys), magnesium alloys, Macol glass, glass, fused silica, copper graphite, polyethylene, polypropylene, polycarbonate, ABC resin, polyphenylene ether, ABS resin, AAS resin, AES resin, nylon, polyamideimide, polyethylene terephthalate, polycarbonate, epoxy resin, and urethane resin.

[0139] The backing material 1102 can be made of thermoplastic resins such as natural rubber, ferrite rubber, epoxy resin, vinyl chloride, polyvinyl butyral, ABS resin, polyurethane, polyvinyl alcohol, polyethylene, polypropylene, polyacetal, polyethylene terephthalate, fluororesin, polyethylene glycol, and polyethylene terephthalate, or these mixed with metal powder, or super-hard materials such as tungsten carbide.

[0140] The piezoelectric element 1101 may be one piece or divided into multiple pieces. Fig. 19 shows an example in which the piezoelectric element is divided into pieces. A flexible cable (not shown) is connected to the electrodes of each piezoelectric element, allowing signals to be transmitted and received by the piezoelectric element to be input and output.

[0141] Acoustic lens 1104 is bonded to acoustic matching layer 1103. Acoustic lens 1104 is a component for converging ultrasonic waves transmitted from piezoelectric element 1101 toward the subject, and is arc-shaped in the example of Fig. 15. Note that the acoustic lens 1104 is generally made of a material such as rubber containing silicone resin (rubber) as its main component.

[0142] When using this ultrasonic probe 1100, an alternating voltage is applied to the piezoelectric element 1101 through the flexible cable, causing the piezoelectric element to vibrate due to the piezoelectric effect, thereby transmitting ultrasonic waves from the piezoelectric element 1101. At this time, if the acoustic impedance of the subject that the ultrasonic waves are applied to is small, or if the ultrasonic waves are applied to the subject through water or air, the presence of the acoustic matching layer 1103 can suppress reflected waves caused by large changes in acoustic impedance, allowing the ultrasonic waves to be efficiently applied to the subject.

[0143] During reception, ultrasonic waves reflected from inside the subject vibrate the piezoelectric element 1101, and this vibration is converted into an electrical signal by the piezoelectric effect to obtain a received signal. During transmission and reception, conversion between electrical energy and mechanical energy occurs, and the conversion efficiency at this time depends on the magnitude of the electromechanical coupling coefficient.

[0144] (Ultrasonic Diagnostic Apparatus) Next, the ultrasonic diagnostic apparatus of the present invention will be described. The ultrasonic diagnostic apparatus of the present invention has at least the ultrasonic probe and an image output unit (image display unit). Fig. 20 is a schematic diagram showing one embodiment of the ultrasonic diagnostic apparatus of the present invention. The ultrasonic diagnostic apparatus 1110 of Fig. 20 is composed of an ultrasonic probe 1100, a cable 1111, a drive control unit 1113, and an image display unit 1112. The flexible cable of the ultrasonic probe 1100 and the drive control unit 1113 are connected by the cable 1111, and an alternating voltage is applied from the drive control unit 1113 to the piezoelectric element 1101 of the ultrasonic probe 1100 via the cable 1111.

[0145] When ultrasonic waves are irradiated into the subject from the ultrasonic probe 1100, the ultrasonic waves reflected from inside the subject are converted into electrical signals again by the ultrasonic probe and input to the image processing unit 1114 via the cable 1111. The image processing unit 1114 generates image data by performing calculations based on the delay time and change in signal strength relative to the alternating voltage output from the drive control unit 1113. The generated image data is output to the image display unit 1112.

[0146] (Ultrasound Diagnostic System) Next, an ultrasound diagnostic system of the present invention will be described. The ultrasound diagnostic system of the present invention includes the ultrasound probe, a transmitter that transmits a signal output from the ultrasound probe, and a receiver that receives a signal transmitted from the transmitter.

[0147] 21 and 22 are schematic diagrams showing one embodiment of the ultrasound diagnostic system of the present invention. In the ultrasound diagnostic system 1120 of Fig. 21, a signal obtained by an ultrasound probe 1100 is transmitted from a transmitter 1121, and the signal is received by a receiver 1122. From the received signal, image data is created by an image processor 1114, and output by an image display 1112. The transmitter 1121 and the receiver 1122 may be far apart. Transmission and reception may be achieved using wireless communication such as Wi-Fi (registered trademark) or Bluetooth (registered trademark), or via a network line by connecting a network cable.

[0148] 22, image data is created from the output signal by an image processing unit 1114, and the data is transmitted as a signal from a transmitting unit 1121, and the signal is received by a receiving unit 1122. The received signal is output by an image display unit 1112.

[0149] (Electronic Device) Next, an electronic device of the present invention will be described. The electronic device of the present invention is provided with a piezoelectric acoustic component including the above-mentioned piezoelectric element or the above-mentioned multilayer piezoelectric element. Piezoelectric acoustic components include speakers, buzzers, microphones, and surface acoustic wave (SAW) elements.

[0150] 23 is an overall perspective view, seen from the front, of a digital camera body 931, which is an example of a preferred embodiment of an electronic device of the present invention. On the front of the body 931, an optical device 901, a microphone 914, a strobe light emitting unit 909, and an fill light unit 916 are arranged. The microphone 914 is shown by a dashed line because it is built into the body. A hole is provided in front of the microphone 914 to pick up external sounds.

[0151] A power button 933, a speaker 912, a zoom lever 932, and a release button 908 for performing a focusing operation are arranged on the top surface of the main body 931. The speaker 912 is incorporated inside the main body 931 and is indicated by a dashed line. A hole is provided in front of the speaker 912 to transmit sound to the outside.

[0152] The piezoelectric acoustic component of the present invention is used for at least one of the microphone 914, the speaker 912, and the surface acoustic wave element.

[0153] Here, a digital camera has been described as an example of the electronic device of the present invention, but the electronic device of the present invention can also be applied to electronic devices having various piezoelectric acoustic components, such as audio playback devices, audio recording devices, mobile phones, and information terminals.

[0154] As described above, the piezoelectric element of the present invention is suitable for use in ultrasonic motors, optical devices, vibration devices, dust removal devices, imaging devices, ultrasonic probes, ultrasonic diagnostic devices and electronic devices.

[0155] By using the piezoelectric element of the present invention, it is possible to provide an ultrasonic motor having driving efficiency equal to or higher than that of a piezoelectric element containing lead.

[0156] By using the ultrasonic motor of the present invention, it is possible to provide optical equipment having an operating speed and operating efficiency equal to or greater than that of a piezoelectric element containing lead.

[0157] By using the piezoelectric element of the present invention, it is possible to provide a vibrating device having vibration capabilities equal to or greater than those of a piezoelectric element containing lead.

[0158] By using the vibration device of the present invention, it is possible to provide a dust removal device having dust removal efficiency equal to or higher than that of a device using a piezoelectric element containing lead.

[0159] By using the dust removing device of the present invention, it is possible to provide an imaging device having a dust removing function equal to or better than that of a device using a piezoelectric element containing lead.

[0160] By using the piezoelectric element of the present invention, it is possible to provide an ultrasonic probe having transmission and reception performance equal to or better than that of a piezoelectric element containing lead.

[0161] By using the ultrasonic probe of the present invention, it is possible to provide an ultrasonic diagnostic device and an ultrasonic diagnostic system that have driving efficiency equal to or higher than that when a piezoelectric element containing lead is used.

[0162] By using a piezoelectric acoustic component including the piezoelectric element of the present invention, it is possible to provide an electronic device that has sound generation properties equal to or better than those achieved when a piezoelectric element containing lead is used.

[0163] In addition to the above-mentioned devices, the single crystal and piezoelectric element of the present invention can be used in devices such as motors, liquid discharge heads, liquid discharge apparatuses, piezoelectric actuators, piezoelectric sensors, and ferroelectric memories.

[0164] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Piezoelectric elements of the present invention and devices and apparatuses using the piezoelectric elements were produced by the methods described below.

[0165] Example 1 Barium titanate (BaTiO) with an average particle size of 100 nm was used as a matrix raw material powder. ３ , Ba / Ti=0.999), barium zirconate (BaZrO ３ , Ba / Zr=1.002) trimanganese tetroxide (Mn ３ O ４ Titanium oxide was used to adjust the ratio α of the sum of the moles of Ti and Zr to the sum of the moles of Ti and Zr.

[0166] These raw material powders were mixed with titanium and barium in a composition formula of Ba ０．９９０ (Ti ０．９８ , Zr ０．０２ ) O ３ The amount of Mn and Bi was weighed out so that the content of metal Mn was 0.01 moles and 0.001 moles, respectively, per mole of this oxide. ３ O ４ ), Bi ２ O ３ was added.

[0167] Furthermore, Mn ３ O ４ and Bi ２ O３ The oxides to which the above-mentioned additives had been added were dry mixed for 24 hours using a ball mill. To granulate the resulting mixed powder, 3 parts by weight of a PVA binder was attached to the surface of the mixed powder using a spray dryer to form granulated powder.

[0168] Next, the obtained granulated powder was filled into a mold having a mirror-finished surface facing the sample, and a molding pressure of 200 MPa was applied using a press molding machine to produce a rectangular parallelepiped molded body. This molded body may be further pressed using a cold isostatic pressing machine.

[0169] The resulting molded body was then placed in an electric furnace and held at a maximum temperature of 1300° C. for 5 hours, and sintered in an air atmosphere for a total of 24 hours to obtain a rectangular parallelepiped matrix measuring 12 mm×18 mm×1.3 mm.

[0170] Next, the average equivalent circular diameter and relative density of the crystal grains constituting the obtained matrix were evaluated. As a result, the average equivalent circular diameter was 2 μm and the relative density was 98%. A polarizing microscope was mainly used to observe the crystal grains. A scanning electron microscope (SEM) was used to identify the particle size of small crystal grains. The average equivalent circular diameter was calculated from the observation results. Furthermore, the relative density was evaluated using the theoretical density calculated from the lattice constant and weighed composition obtained by X-ray diffraction, and the density measured by the Archimedes method.

[0171] Next, both sides of the obtained rectangular parallelepiped matrix were polished using a polishing machine while changing the grit size of the abrasive grains to a thickness of 1.0 mm, and finally chemical polishing was performed as a finishing step to obtain a mirror surface.

[0172] Next, a zirconia-coated alumina sagger was prepared as the sagger 7, a zirconia setter as the setter 6, a zirconia setter as the weight 4, and zirconia beads as the beads 5. These were arranged as shown in FIG. 9, and placed in an electric furnace with the lid on, and heated.

[0173] The seed single crystal used here was a BaTiO crystal measuring 10 mm x 15 mm x 1 mm. ３The substrate used was a (110) mirror-polished substrate (manufactured by Physics Optoelectronics, Inc.) with both surfaces mirror-polished and facing in the (110) direction. In the present invention, the upper and lower surfaces refer to the surface in contact with the main surface of the matrix and the surface opposite to it.

[0174] The temperature profile during heating was as follows: the temperature was increased from room temperature to the liquid phase starting temperature of 1320°C over 8.8 hours at a rate of 150°C / h, and then increased from 1320°C to 1400°C over 100 hours at a rate of 0.80°C / h. The sample was then held at 1400°C for 1000 hours, and finally cooled to room temperature.

[0175] Next, the seed single crystal portion was removed by polishing, the top and bottom surfaces were polished, and the single crystal portion in the thickness direction was confirmed, after which the single crystal portion was cut out with a dicing saw to obtain a single crystal.

[0176] Next, the crystal structure of the obtained single crystal was analyzed by X-ray diffraction. As shown in Figures 4A and 4B, the (110) and (200) pole figures indicated a (110) orientation. Furthermore, the relative density of the obtained single crystal was measured and found to be 98%.

[0177] Next, the composition of the obtained single crystal was evaluated by ICP emission spectroscopy, and the results showed that the weighed compositions of Ba, Ti, Zr, Mn, and Bi were consistent with the compositions after heating.

[0178] Next, 400 nm thick gold electrodes were formed on the front and back of the single crystal by DC sputtering, and a 30 nm thick titanium film was formed between the electrodes and the single crystal as an adhesive layer.

[0179] The electrode-attached single crystal was cut into strips of 10 mm x 0.2 mm x 0.3 mm (k'33 evaluation element, Figure 2) and 10 mm x 2.5 mm x 0.3 mm (k31 evaluation element, Figure 1) so that the long side faces were the (100) plane, producing rectangular piezoelectric elements of the present invention. The resulting piezoelectric elements were polarized by setting the surface of a hot plate to 60°C to 100°C and applying an electric field of 1 kV / mm on the hot plate for 30 minutes.

[0180] The phase transition temperature Tot between the tetragonal system and the orthorhombic system of the polarization-treated piezoelectric element is shown in FIG. ３１ When the measurement temperature is increased from a low temperature to above the Curie temperature Tc using an element, the temperature at which the dielectric constant takes a maximum value appears at a temperature lower than the Curie temperature Tc. For Example 1, Tot was 10°C, and it was found that the crystal was tetragonal when the ambient temperature was 10°C to 60°C and tetragonal when the ambient temperature was 25°C.

[0181] In Table 2, those that were tetragonal over the entire range of environmental temperatures from 10°C to 60°C were marked with "○" in the "Tetragonal @ 10°C to 60°C" column, and those that were not were marked with "×" in the "Tetragonal @ 10°C to 60°C" column.

[0182] k ３３ Before electrodes were attached, the evaluation element was a 0.8 mm × 0.8 mm × 5.0 mm rectangular pillar, which was cut by dicing so that the crystal orientation of the top and bottom surfaces of the pillar was (110). Platinum paste was applied to the (110) surface of the 0.8 mm × 0.8 mm pillar, and heat treatment was performed at 1200 °C for 2 hours to form electrodes on the top and bottom surfaces.

[0183] Next, as the static characteristics of the piezoelectric element having the single crystal of the present invention, the electromechanical coupling coefficient k of the polarization-treated piezoelectric element is ３１ , k ３３ , k' ３３ was evaluated by a resonance-antiresonance method at room temperature (25°C) using an impedance analyzer (4294A manufactured by Agilent Technologies). ３３ and k' ３３ The results are shown in Table 2. ３１ is 32.1%, k ３３ is 73.4%, k' ３３ It was found that the electromechanical coupling coefficient was 68.8%, which is a large value for a lead-free piezoelectric material.

[0184] Next, the coercive field of the piezoelectric element was evaluated. Using a ferroelectric / piezoelectric evaluation system (LCII manufactured by Radiant Technologies, Inc.), the electric field at zero polarization was read from the PE hysteresis curve obtained from the polarization versus electric field in the hysteresis measurement mode shown in Figure 7, and this value was taken as the coercive field. The coercive field Ec at this time was 6.58 kV / cm.

[0185] The obtained k' ３３ From the value of the coercive electric field Ec, the piezoelectric element performance index (k' ３３ × Ec) is a very high value of 453, and k' ３３ It was shown that both the high electric field and the high coercive field Ec were achieved.

[0186] (Example 2) Barium titanate (BaTiO) with an average particle size of 100 nm was used as the raw material powder for the matrix. ３ , Ba / Ti=0.999), barium zirconate (BaZrO ３ , Ba / Zr=1.002) trimanganese tetroxide (Mn ３ O ４ Titanium oxide was used to adjust the ratio α of the sum of the moles of Ti and Zr to the sum of the moles of Ti and Zr.

[0187] These raw material powders were mixed with titanium and barium in a composition formula of Ba ０．９９０ (Ti ０．９８ , Zr ０．０２ ) O ３ The amount of Mn and Bi was weighed out so that the content of metal Mn was 0.01 moles and 0.001 moles, respectively, per mole of this oxide. ３ O ４ ), Bi ２ O ３ was added.

[0188] Furthermore, Mn ３ O ４ and Bi ２ O ３The oxides to which the above-mentioned additives had been added were dry mixed for 24 hours using a ball mill. To granulate the resulting mixed powder, 3 parts by weight of a PVA binder was attached to the surface of the mixed powder using a spray dryer to form granulated powder.

[0189] Next, the obtained granulated powder was filled into a mold having a mirror-finished surface facing the sample, and a molding pressure of 200 MPa was applied using a press molding machine to produce a rectangular parallelepiped molded body.

[0190] The resulting molded body was then placed in an electric furnace and held at a maximum temperature of 1300° C. for 5 hours, and sintered in an air atmosphere for a total of 24 hours to obtain a rectangular parallelepiped matrix measuring 12 mm×18 mm×1.3 mm.

[0191] Next, the average equivalent circular diameter and relative density of the crystal grains constituting the obtained matrix were evaluated. As a result, the average equivalent circular diameter was 2 μm and the relative density was 98%. A polarizing microscope was mainly used to observe the crystal grains. A scanning electron microscope (SEM) was used to identify the particle size of small crystal grains. The average equivalent circular diameter was calculated from the observation results. Furthermore, the relative density was evaluated using the theoretical density calculated from the lattice constant and weighed composition obtained by X-ray diffraction, and the density measured by the Archimedes method.

[0192] Next, both sides of the obtained rectangular parallelepiped matrix were polished using a polishing machine while changing the grit size of the abrasive grains to a thickness of 1.0 mm, and finally chemical polishing was performed as a finishing step to obtain a mirror surface.

[0193] Next, a zirconia-coated alumina sagger 7, a zirconia setter 6, a zirconia setter 8 as the weight 4, and zirconia beads 5 were prepared, arranged as shown in Figure 9, and placed in an electric furnace with the lid on and heated.

[0194] The seed single crystal used here was a BaTiO crystal measuring 10 mm x 15 mm x 1 mm. ３The substrate used was a (111) mirror-polished substrate (manufactured by Physics Opto-electronics). The heating profile was as follows: the temperature was raised from room temperature to the liquid phase start temperature of 1320°C over 8.8 hours at a rate of 150°C / h, and then from 1320°C to 1400°C over 100 hours at a rate of 0.80°C / h. The substrate was then held at 1400°C for 1000 hours and finally cooled to room temperature.

[0195] Next, the seed single crystal portion was removed by polishing, the top and bottom surfaces were polished, and the single crystal portion in the thickness direction was confirmed, after which the single crystal portion was cut out with a dicing saw to obtain a single crystal.

[0196] Next, the crystal structure of the obtained single crystal was analyzed by X-ray diffraction. As shown in Figures 5A and 5B, the (111) and (200) pole figures indicated a (111) orientation. Furthermore, the relative density of the obtained single crystal was measured and found to be 98%.

[0197] Next, the composition of the obtained single crystal was evaluated by ICP emission spectroscopy, and the results showed that the weighed compositions of Ba, Ti, Zr, Mn, and Bi were consistent with the compositions after heating.

[0198] Next, 400 nm thick gold electrodes were formed on the front and back of the single crystal by DC sputtering, and a 30 nm thick titanium film was formed between the electrodes and the single crystal as an adhesive layer.

[0199] This single crystal with electrodes was placed in a 10 mm x 0.2 mm x 0.3 mm (k' ３３ Evaluation element, Figure 2) and 10 mm x 2.5 mm x 0.3 mm (k ３１ The piezoelectric element was cut to the size of an evaluation element (see FIG. 1) to prepare a rectangular piezoelectric element of the present invention. The surface of the obtained piezoelectric element was set to 60° C. to 100° C., and an electric field of 1 kV / mm was applied to the hot plate for 30 minutes to perform a polarization treatment.

[0200] The phase transition temperature Tot between the tetragonal system and the orthorhombic system of the polarized piezoelectric element is defined as k ３１The element was used, and the temperature was raised from a low temperature to above the Curie temperature Tc, at which the dielectric constant reached its maximum value. T was 9°C, and it was found that the crystal was tetragonal when the ambient temperature was between 10°C and 60°C, and tetragonal when the ambient temperature was 25°C.

[0201] k ３３ Before electrodes were attached, the evaluation element was a 0.8 mm × 0.8 mm × 5.0 mm rectangular pillar, which was cut by dicing so that the crystal orientation of the top and bottom surfaces of the pillar was (111). Platinum paste was applied to the (111) surface of the 0.8 mm × 0.8 mm pillar, and heat treatment was performed at 1200 °C for 2 hours to form top and bottom electrodes.

[0202] Next, as the static characteristics of the piezoelectric element having the single crystal of the present invention, the electromechanical coupling coefficient k of the polarization-treated piezoelectric element is ３１ , k ３３ , k' ３３ The results are shown in Table 2. ３１ is 31.2%, k ３３ is 72.8%, k' ３３ It was found that the electromechanical coupling coefficient was 67.4%, which is a large value for a lead-free piezoelectric material.

[0203] Next, the coercive field of the piezoelectric element was evaluated. Using a ferroelectric / piezoelectric evaluation system (LCII manufactured by Radiant Technologies, Inc.), the electric field at zero polarization was read from the PE hysteresis curve obtained from the polarization versus electric field in the hysteresis measurement mode, and this value was taken as the coercive field. The coercive field Ec at this time was 7.50 kV / cm.

[0204] The obtained k' ３３ From the value of the coercive electric field Ec, the piezoelectric element performance index (k' ３３ × Ec) is a very high value of 506, and k' ３３ It was shown that both the high electric field and the high coercive field Ec were achieved.

[0205] (Examples 4, 6 to 8, 11, 12, and 20) Single crystals and piezoelectric elements of the present invention were obtained in the same manner as in Example 2, except that the values ​​were changed as shown in Table 1. The electromechanical coupling coefficient k ３１ , k ３３ , k' ３３ The results are shown in Table 2.

[0206] (Examples 3, 5, 9, 10, 13 to 19, 21 to 23) Single crystals and piezoelectric elements of the present invention were obtained in the same process as in Example 1, except that the values ​​were changed as shown in Table 1. The electromechanical coupling coefficient k ３１ , k ３３ , k' ３３ The results are shown in Table 2.

[0207] (Examples 24 to 27) Barium titanate (BaTiO) with an average particle size of 100 nm was used as the matrix raw material powder. ３ , Ba / Ti=0.999), barium zirconate (BaZrO ３ , Ba / Zr=1.002) trimanganese tetroxide (Mn ３ O ４ Titanium oxide was used to adjust the ratio α of the sum of the moles of Ti and Zr to the sum of the moles of Ti and Zr. These raw material powders were prepared by the composition formula Ba, which is mainly composed of titanium and barium. ０．９９０ (Ti ０．９８ , Zr ０．０２ ) O ３ The ratio was measured.

[0208] As shown in Table 1, for 1 mole of this oxide, trimanganese tetroxide (Mn) was added so that the metallic Mn content was 0.015 in moles in Examples 24 and 25, and 0.020 in moles in Examples 26 and 27, and the metallic Bi content was 0.002 in moles in Examples 24 and 26, and 0.003 in moles in Examples 25 and 27. ３ O ４ ), Bi ２ O ３ was added.

[0209] Furthermore, the main component composition Ba ０．９９０ (Ti ０．９８ , Zr ０．０２ ) O ３ For every mole of perovskite-type metal oxide containing metal Mn and metal Bi, 3 to 7 moles of lithium carbonate Li is used as a single crystallization promoter. ２ CO ３ Mn was added. ３ O ４ , Bi ２ O ３ and Li ２ CO ３ The oxides to which the above-mentioned additives had been added were dry mixed for 24 hours using a ball mill. To granulate the resulting mixed powder, 3 parts by weight of a PVA binder was attached to the surface of the mixed powder using a spray dryer to form granulated powder.

[0210] The subsequent steps were the same as in Example 1 to obtain a single crystal and a piezoelectric element of the present invention. ３１ , k ３３ , k' ３３ The results are shown in Table 2.

[0211] Comparative Example 1: Barium titanate (BaTiO) with an average particle size of 100 nm was used as the matrix raw material powder. ３ , Ba / Ti=0.999), barium zirconate (BaZrO ３ , Ba / Zr=1.002) trimanganese tetroxide (Mn ３ O ４ Titanium oxide was used to adjust the ratio α of the sum of the moles of Ti and Zr to the sum of the moles of Ti and Zr.

[0212] These raw material powders were mixed with titanium and barium in a composition formula of Ba ０．９９０ (Ti ０．９８ , Zr ０．０２ ) O ３The amount of Mn and Bi was weighed out so that the content of metal Mn was 0.01 moles and 0.001 moles, respectively, per mole of this oxide. ３ O ４ ), Bi ２ O ３ was added.

[0213] Furthermore, Mn ３ O ４ and Bi ２ O ３ The oxides to which the above-mentioned additives had been added were dry mixed for 24 hours using a ball mill. To granulate the resulting mixed powder, 3 parts by weight of a PVA binder was attached to the surface of the mixed powder using a spray dryer to form granulated powder.

[0214] Next, the obtained granulated powder was filled into a mold having a mirror-finished surface facing the sample, and a molding pressure of 200 MPa was applied using a press molding machine to produce a rectangular parallelepiped molded body.

[0215] The resulting molded body was then placed in an electric furnace and held at a maximum temperature of 1300° C. for 5 hours, and sintered in an air atmosphere for a total of 24 hours to obtain a rectangular parallelepiped matrix measuring 12 mm×18 mm×1.3 mm.

[0216] Next, the average equivalent circular diameter and relative density of the crystal grains constituting the obtained matrix were evaluated. As a result, the average equivalent circular diameter was 4 μm and the relative density was 98%. A polarizing microscope was mainly used to observe the crystal grains. A scanning electron microscope (SEM) was used to identify the particle size of small crystal grains. The average equivalent circular diameter was calculated from the observation results. Furthermore, the relative density was evaluated using the theoretical density calculated from the lattice constant and weighed composition obtained by X-ray diffraction, and the density measured by the Archimedes method.

[0217] Next, both sides of the obtained rectangular parallelepiped matrix were polished using a polishing machine while changing the grit size of the abrasive grains to a thickness of 1.0 mm, and finally chemical polishing was performed as a finishing step to obtain a mirror surface.

[0218] Next, a zirconia-coated alumina sagger was prepared as the sagger 7, a zirconia setter as the setter 6, a zirconia setter as the weight 4, and zirconia beads as the beads 5. These were arranged as shown in FIG. 9, and placed in an electric furnace with the lid on, and heated.

[0219] The seed single crystal used here was a BaTiO crystal measuring 10 mm x 15 mm x 1 mm. ３ The substrate used was a (100) substrate (manufactured by Physics Opto-electronics) with both surfaces mirror-polished.

[0220] The temperature profile during heating was as follows: the temperature was increased from room temperature to the liquid phase starting temperature of 1320°C over 8.8 hours at a rate of 150°C / h, and then increased from 1320°C to 1400°C over 100 hours at a rate of 0.80°C / h. The sample was then held at 1400°C for 1000 hours, and finally cooled to room temperature.

[0221] Next, the seed single crystal portion was removed by polishing, the top and bottom surfaces were polished, and the single crystal portion in the thickness direction was confirmed, after which the single crystal portion was cut out with a dicing saw to obtain a single crystal.

[0222] Next, the crystal structure of the obtained single crystal was analyzed by X-ray diffraction. As shown in Figures 3A and 3B, the (200) and (110) pole figures indicated a (100) orientation. Furthermore, the relative density of the obtained single crystal was measured and found to be 98%.

[0223] Next, the composition of the obtained single crystal was evaluated by ICP emission spectroscopy, and the results showed that the weighed compositions of Ba, Ti, Zr, Mn, and Bi were consistent with the compositions after heating.

[0224] Next, 400 nm thick gold electrodes were formed on the front and back of the single crystal by DC sputtering, and a 30 nm thick titanium film was formed between the electrodes and the single crystal as an adhesive layer.

[0225] The single crystal with electrodes was placed in a 10 mm x 0.2 mm x 0.3 mm (k') dimension so that the (100) planes were the top and bottom faces and the (110) planes were the side faces. ３３ Evaluation element, Figure 2) and 10 mm x 2.5 mm x 0.3 mm (k３１ The piezoelectric element was cut to the size of an evaluation element (see FIG. 1) to prepare a rectangular piezoelectric element of Comparative Example 1. The surface of a hot plate was set to a temperature of 60° C. to 100° C., and an electric field of 1 kV / mm was applied to the obtained piezoelectric element on the hot plate for 30 minutes to perform a polarization treatment.

[0226] The phase transition temperature Tot between the tetragonal system and the orthorhombic system of the polarized piezoelectric element is defined as k ３１ The element was used, and the temperature was raised from a low temperature to above the Curie temperature Tc, at which the dielectric constant reached its maximum value. T was 10°C, and it was found that the crystal was tetragonal when the ambient temperature was between 10°C and 60°C, and tetragonal when the ambient temperature was 25°C.

[0227] k ３３ Before electrodes were attached, the evaluation element was a rectangular pillar of 0.8 mm x 0.8 mm x 5.0 mm, which was cut out by dicing so that the crystal orientation of the upper and lower faces of the rectangular pillar was (100).

[0228] Next, as the static characteristics of the piezoelectric element, the electromechanical coupling coefficient k of the polarization-treated piezoelectric element is ３１ , k ３３ , k' ３３ The results are shown in Table 2. ３１ is 19.1%, k ３３ is 44.6%, k' ３３ It was found that the electromechanical coupling coefficient was relatively small, at 41.3%.

[0229] Next, the coercive field of the piezoelectric element was evaluated. Using a ferroelectric / piezoelectric evaluation system (LCII manufactured by Radiant Technologies, Inc.), the electric field at zero polarization was read from the PE hysteresis curve obtained from the polarization versus electric field in the hysteresis measurement mode, and this value was taken as the coercive field. The coercive field at this time was 4.19 kV / cm.

[0230] The obtained k' ３３ and the piezoelectric element performance index (k' ３３× Ec) was 173, which was less than 200, so k' ３３ It was shown that the coercive field Ec and the tensile strength Ec cannot be simultaneously achieved.

[0231] Comparative Example 2 A single crystal and a piezoelectric element were obtained in the same process as in Comparative Example 1, except that the values ​​were changed as shown in Table 1. The electromechanical coupling coefficient k ３１ , k ３３ , k' ３３ The results are shown in Table 2.

[0232] The phase transition temperature Tot between the tetragonal and orthorhombic crystal systems of the piezoelectric element subjected to polarization treatment in Comparative Example 2 was 10°C, and it was found that the element was in the tetragonal crystal system when the ambient temperature was in the range of 10°C to 60°C and in the tetragonal crystal system when the ambient temperature was 25°C.

[0233] (Comparative Examples 3 to 5) Single crystals and piezoelectric elements were obtained in the same manner as in Example 1, except that the values ​​were changed as shown in Table 1. The electromechanical coupling coefficient k ３１ , k ３３ , k' ３３ The results are shown in Table 2.

[0234] The phase transition temperatures Tot between the tetragonal system and the orthorhombic system of the polarization-treated piezoelectric elements of Comparative Examples 3, 4, and 5 were 26° C., 29° C., and 34° C., respectively. It was found that the piezoelectric elements were orthorhombic at room temperature (25° C.), but not tetragonal at ambient temperatures in the range of 10° C. to 60° C. (In Table 2, the column for tetragonal system @ 10° C. to 60° C. is marked with "X").

[0235] (Comparative Examples 6 and 7) In Comparative Examples 6 and 7, no region where the single crystal portion spread from the seed single crystal was observed in the matrix after heating, and a single crystal could not be obtained.

[0236]

[0237]

[0238] Example 28 An ultrasonic motor shown in Fig. 11 was fabricated using the piezoelectric element of Example 1. In the fabricated ultrasonic motor, rotation of the motor in response to application of an alternating voltage was confirmed.

[0239] Example 29 The optical device shown in Fig. 13 was fabricated using the ultrasonic motor of Example 28. In the fabricated optical device, autofocus operation in response to application of an AC voltage was confirmed.

[0240] 14A and 14B was fabricated using the piezoelectric element of Example 1. When plastic beads were scattered in the fabricated dust removal device and an alternating voltage was applied, a good dust removal rate was confirmed.

[0241] (Example 31) The imaging device shown in Fig. 18 was fabricated using the dust removal device of Example 30. When the fabricated imaging device was operated, dust on the surface of the imaging unit was successfully removed, and an image without dust defects was obtained.

[0242] (Example 32) The ultrasonic probe shown in Fig. 19 was fabricated using the piezoelectric element of Example 1. In the fabricated ultrasonic probe, ultrasonic waves were transmitted by applying an alternating voltage, and a received signal due to reflection from inside the subject was confirmed.

[0243] (Example 33) The ultrasonic diagnostic device shown in Fig. 20 was fabricated using the ultrasonic probe of Example 32. When the fabricated ultrasonic diagnostic device was operated, a clear image of the inside of the subject was output.

[0244] (Example 34) An ultrasound diagnostic system shown in Fig. 21 was fabricated using the ultrasound probe of Example 33. When the fabricated ultrasound diagnostic system was operated and an image was displayed on the image display unit, a clear image of the inside of the subject was output.

[0245] Example 35 An electronic device shown in Fig. 23 was fabricated using the piezoelectric element of Example 1. In the fabricated electronic device, speaker operation in response to application of an alternating voltage was confirmed.

[0246] The piezoelectric element of the present invention has a large electromechanical coupling coefficient and coercive electric field, which indicate piezoelectric performance. Therefore, the single crystal of the present invention can be used without problems in many devices, such as ultrasonic motors, dust removal devices, and ultrasonic probes. Because the above-mentioned technology can be used even in configurations in which the single crystal contains less than 1,000 ppm of Pb, the technology described herein can contribute to the realization of a sustainable society, such as a carbon-free / recycling-based society.

[0247] The present invention is not limited to the above-described embodiments, and various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the following claims are appended to apprise the public of the scope of the present invention.

[0248] This application claims priority based on Japanese Patent Application No. 2024-015528 filed on February 5, 2024, and Japanese Patent Application No. 2024-215920 filed on December 10, 2024, the entire contents of which are incorporated herein by reference.

[0249] REFERENCE SIGNS LIST 1 matrix 2 seed single crystal 3 single crystal 4 weight 5 beads 6 setter 7 sagger 8 lid 11 first electrode 33 second electrode 201 vibrator 202 rotor 203 output shaft 2011 elastic ring 2012 piezoelectric element 2013 organic adhesive 310 dust removal device 320 diaphragm 330 piezoelectric element 331 single crystal 332 first electrode 333 second electrode 336 first electrode surface 337 second electrode surface 601 camera body 602 mount section 605 mirror box 606 main mirror 200 shutter unit 300 body chassis 400 imaging unit 701 front lens group 702 rear lens group (focus lens) 711 detachable mount 712 Fixed barrel 713 Linear guide barrel 714 Front group barrel 715 Cam ring 716 Rear group barrel 717 Cam roller 718 Shaft screw 719 Roller 720 Rotation transmission ring 722 Roller 724 Manual focus ring 725 Ultrasonic motor 726 Wave washer 727 Ball race 728 Focus key 729 Joint member 732 Washer 733 Low-friction sheet 901 Optical device 908 Release button 909 Strobe light emitting unit 912 Speaker 914 Microphone 916 Filler light unit 931 Main body 932 Zoom lever 933 Power button 1100 Ultrasonic probe 1101 Piezoelectric element 1102 Backing layer 1103 Acoustic matching layer 1104 Acoustic lens 1110 Ultrasonic diagnostic device 1111 Cable 1112 Image display unit 1113 Drive control unit 1114 Image processing unit 1120 Ultrasound diagnostic system 1121 Transmitting unit 1122 Receiving unit

Claims

1. A piezoelectric element having a single crystal of perovskite metal oxide and opposing electrodes, characterized in that when the ambient temperature is 25°C, the crystal system of the single crystal is tetragonal, and the crystal orientation of the surface of the single crystal that contacts the electrode surfaces of the opposing electrodes is (110) or (111).

2. The piezoelectric element according to claim 1, wherein said single crystal contains less than 1000 ppm of Pb.

3. The piezoelectric element according to claim 1 or 2, wherein the single crystal is mainly composed of a perovskite metal oxide containing Ba, Ti, and Zr, and wherein, when x is the amount (molar ratio) of Zr to the total amount of the Ti and the Zr, 0.01≦x≦0.03, and when α is the amount (molar ratio) of Ba to the total amount of the Ti and the Zr, 0.976≦α≦1.020, and the single crystal contains at least Mn and Bi, and the Mn content is 0.0020 to 0.0500 molar parts per 1 molar part of the perovskite metal oxide containing Ba, Ti, and Zr, and the Bi content is 0.0005 to 0.0060 molar parts per 1 molar part of the perovskite metal oxide containing Ba, Ti, and Zr.

4. The piezoelectric element according to any one of claims 1 to 3, wherein the single crystal has a main component containing a perovskite metal oxide represented by the following general formula (1), a first subcomponent consisting of Mn, and a second subcomponent consisting of trivalent Bi, wherein the content of the Mn is 0.0020 to 0.0500 molar parts per 1 molar part of the perovskite metal oxide represented by the general formula (1), and the content of the Bi is 0.0005 to 0.0060 molar parts per 1 molar part of the perovskite metal oxide represented by the general formula (1). Ba α (Ti １－ｘ Zr ｘ ) O ３ (1) (In the formula, 0.01≦x≦0.03, 0.976≦α≦1.020) 5. A piezoelectric element according to any one of claims 1 to 4, which has a coercive electric field Ec of 10 kV / cm or more.

6. The piezoelectric element according to any one of claims 1 to 5, wherein the single crystal contains, as a main component, a perovskite-type metal oxide represented by the following general formula (2): (1-y)Pb(Mg １／３ Nb ２／３ ) O ３ - yPbTiO ３ (2) (In the formula, 0.34≦y≦0.50) 7. The piezoelectric element according to any one of claims 1 to 6, wherein the single crystal contains, as a main component, a perovskite-type metal oxide represented by the following general formula (3): (1-z)Pb(Zn １／３ Nb ２／３ ) O ３ -zPbTiO ３ (3) (In the formula, 0.12≦z≦0.20) 8. A piezoelectric element according to any one of claims 1 to 7, wherein the crystal system of the perovskite metal oxide is tetragonal when the ambient temperature is 0°C or higher and 60°C or lower.

9. A piezoelectric element according to any one of claims 1 to 8, wherein the crystal orientation of the surface of the single crystal in contact with the opposing electrode surface is (110), and when the electrode surface of the opposing electrode is taken as the main surface of the piezoelectric element, the crystal orientation of the side surface of the piezoelectric element on the longitudinal side of the electrode surface is (001).

10. A method for manufacturing a piezoelectric element, comprising: a first preparation step of preparing a matrix and a seed single crystal; a second preparation step of preparing an integrated body in which the surface of the matrix and the (110) plane or the (111) plane of the seed single crystal are in contact; a first heating step of raising the temperature of the integrated body from room temperature to the liquid phase start temperature of the matrix; a second heating step of raising the temperature of the integrated body from the liquid phase start temperature to the liquid phase end temperature of the matrix; a heating step of heating the integrated body at the liquid phase end temperature; a step of obtaining a single crystal from the integrated body after heating; a step of arranging opposing electrodes on the single crystal to prepare a piezoelectric element; and a step of performing a polarization treatment on the piezoelectric element, wherein the heating rate in the second heating step is smaller than the heating rate in the first heating step.

11. An ultrasonic motor having a vibrating body on which the piezoelectric element according to any one of claims 1 to 9 is arranged, and a moving body in contact with the vibrating body.

12. An optical device having an ultrasonic motor according to claim 11 in a driving section.

13. A vibrating device having a vibrating body in which the piezoelectric element according to any one of claims 1 to 9 is arranged on a diaphragm.

14. A dust removal device having the vibration device according to claim 13 in its vibration section.

15. An imaging device comprising the dust removal device according to claim 14 and an imaging element unit, wherein the diaphragm of said dust removal device is provided on the light receiving surface side of said imaging element unit.

16. An ultrasonic probe having a piezoelectric element according to any one of claims 1 to 9, which transmits and receives signals using said piezoelectric element.

17. An ultrasonic diagnostic device comprising the ultrasonic probe according to claim 16 and an image output unit.

18. An ultrasound diagnostic system comprising the ultrasound probe according to claim 16, a transmitter for transmitting signals output from said ultrasound probe, and a receiver for receiving signals transmitted from said transmitter.

19. An electronic device equipped with a piezoelectric acoustic component having a piezoelectric element according to any one of claims 1 to 9.

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