Piezoelectric ceramic, ceramic electronic component, and method for manufacturing piezoelectric ceramic

Abstract

A piezoelectric ceramic characterized by containing a perovskite compound containing at least Pb, Zr, Ti, Mn, and Nb, in an X-ray crystal structure analysis chart of the perovskite compound, an X-ray diffraction peak of a (101) plane is detected in a range of 2θ = 30.5° to 31.5° which is a main peak of a PZT tetragonal phase, and an X-ray diffraction peak of a (110) plane is detected in a range of 2θ = 30.8° to 31.8°, and the number of X-ray diffraction peaks appearing based on the (101) plane and the (110) plane is one.

Description

[0001] This application is a divisional application of patent application 201980035361.0 (International filing date: July 3, 2019, invention title: piezoelectric ceramic, ceramic electronic component and method for manufacturing piezoelectric ceramic). Technical Field

[0002] This invention relates to a piezoelectric ceramic, a ceramic electronic component, and a method for manufacturing a piezoelectric ceramic. Background Technology

[0003] In recent years, there has been a surge in demand for miniaturization of portable devices and thinner, lighter televisions, which in turn requires further miniaturization and shrinkage of electronic components. Piezoelectric resonant driven high-power devices, due to their ability to achieve large displacements at low voltages, are advantageous for miniaturization and shrinkage.

[0004] Lead zirconate titanate (hereinafter referred to as "PZT"), which has good piezoelectric properties, is widely used as a ceramic material in such piezoelectric ceramic electronic components.

[0005] However, in the aforementioned high-power piezoelectric resonant driven devices, a low Vmax (limiting vibration velocity) during resonant driving leads to thermal runaway, causing a sharp temperature rise and significantly reducing the lifespan of the piezoelectric ceramic. Furthermore, in piezoelectric transformers, the heat generated during driving affects surrounding circuitry, potentially degrading device characteristics. Therefore, to suppress thermal runaway during driving, it is necessary to increase Vmax during resonant driving.

[0006] Patent Document 1 discloses a piezoelectric ceramic composition with PZT as the main component. Furthermore, Patent Document 2 also discloses a piezoelectric ceramic composition, describing the preparation of the composition by calcining the molded article at a temperature above 1300°C.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2006-199524

[0010] Patent Document 2: Japanese Patent Application Publication No. 2017-165618 Summary of the Invention

[0011] In PZT-based piezoelectrics like those in Patent Document 1, a high piezoelectric constant can be expected by replacing a portion of Pb with Sr, which has low electronegativity. However, during resonant driving, the presence of easily mobile Sr ions can lead to increased heat generation, accompanied by a decrease in Vmax and Qm. From the viewpoint of extending the lifetime of piezoelectric ceramics, this is not preferable.

[0012] Furthermore, Patent Document 1

[0031] states that "the reason for the improved Kr properties is the effect of ceramic grain growth," which suggests that the piezoelectric ceramic composition obtained in Patent Document 1 is highly crystalline.

[0013] In Patent Document 2, by substituting La at the A site of PZT, an improvement in Qm can be expected compared to the Sr substitution case. However, this material requires calcination at a high temperature of up to 1300°C to achieve sintering resistance. Under high-temperature calcination, rapid sintering diffusion occurs, increasing the atomic concentration and promoting the formation of crystal nuclei, thereby leading to crystallization. If crystallization occurs, the 90° region inversion increases, resulting in increased heat generation and a decrease in Vmax, which are accompanied by a decrease in Qm during resonant vibration, making it impossible to expect a long lifespan for the piezoelectric ceramic.

[0014] The present invention was made in view of the above-mentioned actual situation, and its purpose is to provide a piezoelectric ceramic that can improve Qm and suppress heat generation during resonant large amplitude driving, improve Vmax, thereby achieving a long lifespan, as well as ceramic electronic components using the piezoelectric ceramic and a method for manufacturing the piezoelectric ceramic.

[0015] The piezoelectric ceramic of the present invention is characterized in that it contains a perovskite-type compound comprising at least Pb, Zr, Ti, Mn and Nb. In the X-ray crystallographic analysis diagram of the perovskite-type compound, the X-ray diffraction peaks detected on the (101) plane of the main peak of the PZT tetragonal phase, i.e., the range of 2θ = 30.5° to 31.5°, and the X-ray diffraction peaks detected on the (110) plane, i.e., the range of 2θ = 30.8° to 31.8°, are unbranched, and the number of X-ray diffraction peaks appearing on the (101) plane and the (110) plane is one.

[0016] The ceramic electronic component of the present invention is characterized by having a piezoelectric body comprising the piezoelectric ceramic of the present invention and an external electrode.

[0017] The first embodiment of the piezoelectric ceramic manufacturing method of the present invention is a method for manufacturing piezoelectric ceramics comprising the following steps: preparing a ceramic material raw material comprising at least a Pb compound, a Zr compound, a Ti compound, a Mn compound, and a Nb compound; preparing a ceramic pre-fired powder by pre-firing the above-mentioned ceramic material raw material; forming the above-mentioned ceramic pre-fired powder to form a ceramic molded body; and calcining the above-mentioned ceramic molded body to obtain a sintered body, wherein the oxygen partial pressure is 9.87 × 10⁻⁶. －2 MPa ~ 1.01 × 10 －1 The above calcination process is carried out under a high oxygen atmosphere of MPa.

[0018] The second aspect of the method for manufacturing piezoelectric ceramics of the present invention is characterized by comprising the following steps: preparing a ceramic material raw material comprising at least a Pb compound, a Zr compound, a Ti compound, a Mn compound, and a Nb compound; preparing a ceramic pre-fired powder by pre-firing the above-mentioned ceramic material raw material; pulverizing the above-mentioned ceramic pre-fired powder; forming the pulverized above-mentioned ceramic pre-fired powder into a ceramic molded body; and calcining the above-mentioned ceramic molded body to obtain a sintered body.

[0019] According to the present invention, a piezoelectric ceramic can be provided that suppresses heat generation and increases Vmax by increasing Qm during resonant large amplitude driving, thereby achieving a long lifespan. Attached Figure Description

[0020] Figure 1 This is a cross-sectional view, an example of a first way of schematically representing a ceramic electronic component.

[0021] Figure 2 This is a cross-sectional view illustrating a second way of representing a ceramic electronic component.

[0022] Figure 3 This is a cross-sectional view schematically representing a third-party example of a ceramic electronic component.

[0023] Figure 4 This is an electron microscope image of the piezoelectric ceramic prepared from sample number 3.

[0024] Figure 5 This is a graph comparing the X-ray diffraction peaks of the piezoelectric ceramic single plates prepared from samples 1 to 4.

[0025] Figure 6 This is a graph comparing the X-ray diffraction peaks of the piezoelectric ceramic plates prepared from samples 2, 5, and 6.

[0026] Figure 7 This is a coordinate graph showing the relationship between the vibration velocity and Qm of the piezoelectric ceramics prepared by sample numbers 1 to 4 under resonant drive.

[0027] Figure 8 This is a coordinate graph showing the relationship between the vibration velocity and Qm of the piezoelectric ceramics prepared by sample numbers 2, 5, and 6 under resonance drive.

[0028] Figure 9 This is a coordinate graph showing the relationship between the vibration velocity and heat generation when the piezoelectric ceramics prepared by sample numbers 1 to 4 are driven by resonance.

[0029] Figure 10This is a coordinate graph showing the relationship between the vibration velocity and heat generation when the piezoelectric ceramics prepared by sample numbers 2, 5, and 6 are driven by resonance. Detailed Implementation

[0030] The piezoelectric ceramic, ceramic electronic component, and manufacturing method of the piezoelectric ceramic of the present invention will be described below.

[0031] However, the present invention is not limited to the following configurations, and can be appropriately modified and applied without changing the spirit of the invention. It should be noted that combinations of two or more of the preferred configurations of the present invention described below also fall under the scope of the present invention.

[0032] <Piezoelectric ceramics>

[0033] The piezoelectric ceramic of the present invention is characterized in that it contains at least a perovskite-type compound comprising Pb, Zr, Ti, Mn and Nb. In the X-ray crystallographic analysis diagram of the perovskite-type compound, the X-ray diffraction peaks detected on the (101) plane of the main peak of the PZT tetragonal phase, i.e., in the range of 2θ = 30.5° to 31.5°, and the X-ray diffraction peaks detected on the (110) plane in the range of 2θ = 30.8° to 31.8°, are unbranched, and the number of X-ray diffraction peaks appearing based on the (101) plane and the (110) plane is one.

[0034] The crystals of perovskite-type compounds containing Pb, Zr, Ti, Mn, and Nb were analyzed by X-ray diffraction (XRD) of the crystal structure. XRD peaks based on the (101) plane were detected in the range of 2θ = 30.5°–31.5°. Additionally, XRD peaks based on the (110) plane were detected in the range of 2θ = 30.8°–31.8°.

[0035] When the perovskite-type compound has high crystallinity, X-ray diffraction peaks based on the (101) plane and X-ray diffraction peaks based on the (110) plane can be clearly distinguished and detected.

[0036] On the other hand, when the crystallinity of perovskite-type compounds is low, the X-ray diffraction peaks based on the (101) plane and the X-ray diffraction peaks based on the (110) plane are unbranched, and the number of X-ray diffraction peaks based on the (101) plane and the (110) plane is one.

[0037] That is, the perovskite-type compound constituting the piezoelectric ceramic of the present invention is a compound with low crystallinity.

[0038] In the piezoelectric ceramic of the present invention, in the X-ray crystal structure analysis diagram of the perovskite-type compound, preferably one X-ray diffraction peak based on the (101) plane and the (110) plane appears at a position of 2θ = 30.8° to 31.2°.

[0039] This position is slightly offset from the peak position of the (101) plane based on the PZT tetragonal phase, where there is no boundary between the peaks based on the (101) and (110) planes, and it appears as an X-ray diffraction peak.

[0040] X-ray crystal structure analysis can be performed using commonly used X-ray crystal structure analysis equipment.

[0041] For example, the following apparatus and measurement conditions can be used for the measurement.

[0042] X-ray tube: CuKα

[0043] Tube voltage: 45kV

[0044] Tube current: 200mA

[0045] Scanning angle: 10-70°

[0046] Sampling width: 0.02°

[0047] Optical system: Luminous optical system

[0048] The perovskite-type compound constituting the piezoelectric ceramic of the present invention has low crystallinity, which suppresses the decrease of Qm in the high vibration velocity region when the piezoelectric properties are measured as ceramic electronic components. Furthermore, the limiting vibration velocity (Vmax) becomes higher.

[0049] In the past, in order to improve the piezoelectric properties of ceramic electronic components using piezoelectric ceramics, the grains of the compound constituting the piezoelectric ceramic were usually grown to increase crystallinity. However, improving the piezoelectric properties by intentionally using compounds with low crystallinity is a method that was not conceived in previous technologies.

[0050] The piezoelectric ceramic of the present invention contains a perovskite-type compound comprising Pb, Zr, Ti, Mn and Nb, and is a composition in which at least Mn and Nb are added to PZT ceramic.

[0051] The Mn content in the perovskite compound is preferably 0.019 mol% to 0.041 mol%. Furthermore, the Nb content in the perovskite compound is preferably 0.048 mol% to 0.057 mol%.

[0052] In addition, trace amounts of Hf, Fe, Cl, Si, Al, etc., may be contained as unavoidable impurities, provided that the properties of the piezoelectric ceramic of the present invention are not impaired.

[0053] The piezoelectric ceramic of the present invention preferably has a mechanical quality factor Qm of 800 or more at a vibration velocity of 0.55 m / s.

[0054] Furthermore, the piezoelectric ceramic of the present invention preferably has a limiting vibration velocity (Vmax) of 0.8 m / s or more as a material.

[0055] The properties of the piezoelectric ceramic of the present invention can be determined as follows.

[0056] (1) The piezoelectric ceramic was cut into a shape of 13mm in length, 3mm in width, and 0.9mm in thickness using a cutting machine for the evaluation of piezoelectric properties.

[0057] (2) The cut sample was subjected to polarization treatment for 30 minutes at a temperature of 150℃ and an electric field strength of 3kV / mm using an oil bath or similar method.

[0058] (3) Specific permittivity (ε) of the micro electric field 33 T / ε0) and electromechanical coupling coefficient (k 31 The blockage detector (Agilent Technologies: 4294A) can be used to measure the blockage using the resonance-anti-resonance method based on the Japan Electronic Materials Industries Association standard specification (EMAS-6100).

[0059] (4) Resonance-driven mechanical quality factor (Qm), limiting vibration velocity (Vmax), and elastic compliance (S) 11 E The value of ) is determined by the rated current measurement method. The vibration velocity at which the temperature rises to 20°C at the vibration node of the oscillator under resonant driving state at room temperature is taken as the limiting vibration velocity.

[0060] <Manufacturing Methods of Piezoelectric Ceramics>

[0061] Next, the manufacturing method of the piezoelectric ceramic of the present invention will be described.

[0062] The method for manufacturing the piezoelectric ceramic of the present invention includes two methods. The first method is characterized by using an oxygen partial pressure of 9.87 × 10⁻⁶. －2 MPa ~ 1.01 × 10 －1 The calcination process is carried out under a high oxygen atmosphere of MPa.

[0063] In addition, the second method is characterized by a pulverizing process that pulverizes the pre-fired ceramic powder.

[0064] The piezoelectric ceramic of the present invention can be obtained by any method.

[0065] (The first method for manufacturing piezoelectric ceramics)

[0066] The first embodiment of the manufacturing method of the piezoelectric ceramic of the present invention includes the following steps: preparing a ceramic material raw material comprising at least a Pb compound, a Zr compound, a Ti compound, a Mn compound, and a Nb compound; preparing a ceramic pre-fired powder by pre-firing the above-mentioned ceramic material raw material; forming the above-mentioned ceramic pre-fired powder to form a ceramic molded body; and calcining the above-mentioned ceramic molded body to obtain a sintered body, wherein the oxygen partial pressure is 9.87 × 10⁻⁶. －2 MPa ~ 1.01 × 10 －1 The above calcination process is carried out under a high oxygen atmosphere of MPa.

[0067] [Ceramic pre-fired powder preparation process]

[0068] Prepare ceramic material raw materials containing at least Pb compounds, Zr compounds, Ti compounds, Mn compounds and Nb compounds.

[0069] There are no particular restrictions on the form of these compounds; they can be compounds in the form of oxides, carbonates, chlorides, hydroxides, organometallic compounds, etc.

[0070] The above-mentioned ceramic material raw materials are weighed in a manner that, after sintering, results in a specified composition ratio.

[0071] Next, these weighed materials are put into a ball mill or similar material containing some pulverizing media such as stabilized zirconium. Pure water and organic solvents are used as solvents for wet mixing. After dehydration, the materials are pre-fired in a large atmosphere at a temperature of 930℃~1080℃ to prepare ceramic pre-fired powder.

[0072] [Molding Process]

[0073] Next, the ceramic raw material powder is crushed, and organic binders such as polyvinyl alcohol resin are added. The mixture is then wet-dispersed without media or wet-milled using a ball mill containing grinding media to prepare a slurry. This slurry is then spray-dried to prepare granulated powder for molding. The granulated powder is then molded to prepare a ceramic molded body.

[0074] [Calcination and Degreasing Treatment]

[0075] The ceramic molded body is placed in a firing pan and placed in a furnace for calcination and degreasing. The calcination and degreasing process is carried out in an atmospheric atmosphere using a muffle furnace or similar device. The calcination conditions involve raising the furnace temperature to a specified temperature (e.g., 400°C to 500°C) at a specified heating rate (e.g., 0.5°C / min to 4°C / min), performing degreasing for a specified time (e.g., 1 hour to 3 hours), and then cooling at a specified cooling rate (e.g., 1°C / min to 6°C / min) to complete the calcination and degreasing process.

[0076] Calcination and degreasing is an optional process.

[0077] [Calcination process]

[0078] Next, the main calcination (calcination process) is carried out. The calcination process is conducted at an oxygen partial pressure of 9.87 × 10⁻⁶. －2 MPa ~ 1.01 × 10 － 1 The experiment was conducted under a high-oxygen atmosphere of MPa.

[0079] As calcination conditions, the furnace temperature is raised to a specified temperature (e.g., 250°C to 350°C) at a specified heating rate (e.g., 0.5°C / min to 4°C / min) and held for a specified time (e.g., 1 hour to 3 hours). After replacing the calcination atmosphere with O2 to create the aforementioned high-oxygen atmosphere, the furnace temperature is raised to a specified calcination temperature (e.g., 1100°C to 1250°C) at a specified heating rate (e.g., 0.5°C to 4°C / min) and held for a specified time (e.g., 6 hours to 10 hours). Then, the temperature is lowered at a specified cooling rate (e.g., 1°C / min to 6°C / min) to complete the calcination process and obtain piezoelectric ceramics.

[0080] Furthermore, the calcination temperature in the calcination process is more preferably 1060°C to 1200°C. From the viewpoint of densifying the piezoelectric ceramic, it is preferable to set the calcination temperature to 1060°C or higher, thereby obtaining a piezoelectric ceramic with low porosity.

[0081] Under high oxygen partial pressure using O2 gas (oxygen partial pressure is 9.87 × 10⁻⁶), －2 MPa ~ 1.01 × 10 －1 Calcination under an atmosphere of MPa yields a perovskite-type compound with low crystallinity, in which the X-ray diffraction peaks of the (101) and (110) planes of the tetragonal PZT phase are unbranched and the number of X-ray diffraction peaks based on the (101) and (110) planes is one.

[0082] It is speculated that this is because the solid dissolution of Mn components into the B sites of PZT-based perovskite compounds is suppressed, which in turn reduces oxygen vacancies and inhibits sintering, resulting in low crystallinity.

[0083] (Second method for manufacturing piezoelectric ceramics)

[0084] The second aspect of the method for manufacturing piezoelectric ceramics of the present invention is characterized by comprising the following steps: preparing a ceramic material raw material comprising at least a Pb compound, a Zr compound, a Ti compound, a Mn compound, and a Nb compound; preparing a ceramic pre-fired powder by pre-firing the above-mentioned ceramic material raw material; pulverizing the above-mentioned ceramic pre-fired powder; forming the pulverized above-mentioned ceramic pre-fired powder to form a ceramic molded body; and calcining the above-mentioned ceramic molded body to obtain a sintered body.

[0085] In this method, the process up to the [ceramic pre-fired powder preparation process] can be the same as the first method described above. Therefore, the subsequent processes (processes after the pulverization process) will be described.

[0086] [Grinding Process]

[0087] In the pulverization process, the pre-fired ceramic powder is pulverized, and then a dispersant and defoamer are added. The powder is then wet-pulverized in a container with some stabilized zirconia balls for a specified time (e.g., 10 to 40 hours) to prepare a slurry.

[0088] By performing a pulverization process, the crystallinity of the pre-fired powder can be reduced, thereby obtaining piezoelectric ceramics of perovskite-type compounds with low crystallinity.

[0089] In the crushing process, a specific surface area of ​​2.9–5.3 m² based on the BET method is preferred. 2 The material is pulverized using a / g method.

[0090] [Molding Process]

[0091] In the molding process, the slurry is filled into a resin mold and dried for a specified time (e.g., 20 to 28 hours) to obtain a ceramic molded body (cast molded body).

[0092] [Calcination and Degreasing Treatment]

[0093] The cast body is placed in a calcining pan and placed inside a furnace for calcination and degreasing. The calcination and degreasing process is carried out in an atmospheric atmosphere using a muffle furnace or similar device. The calcination conditions are as follows: the furnace temperature is raised to a specified temperature (e.g., 70°C to 80°C) at a specified heating rate (e.g., 0.5°C / min to 4°C / min), then raised to a specified temperature (e.g., 350°C to 450°C) at a specified heating rate (e.g., 0.2°C / min to 0.5°C / min), held for a specified time (e.g., 1 hour to 3 hours), and then further raised to a specified temperature (e.g., 550°C to 650°C) at a specified heating rate (e.g., 2°C / min to 4°C / min), held for a specified time (e.g., 0.5 hours to 1.5 hours), and finally cooled at a specified cooling rate (e.g., 1°C / min to 5°C / min) to complete the calcination and degreasing process.

[0094] Calcination and degreasing is an optional process.

[0095] [Calcination process]

[0096] Next, the main calcination (calcination process) is carried out.

[0097] As calcination conditions, the furnace temperature is raised to a specified temperature (e.g., 250°C to 350°C) at a specified heating rate (e.g., 0.5°C / min to 4°C / min), held for a specified time (e.g., 1 hour to 3 hours), and then the calcination atmosphere is replaced with N2. The furnace temperature is then raised to a specified temperature (e.g., 1030°C to 1200°C) at a specified heating rate (e.g., 0.5°C / min to 4°C / min), held for a specified time (e.g., 6 hours to 10 hours), and then cooled at a specified cooling rate (e.g., 1°C / min to 6°C / min) to complete the main calcination process.

[0098] The preferred furnace atmosphere for the calcination process is one using N2 gas with an oxygen partial pressure of 5.74 × 10⁻⁶. －7 MPa ~ 3.28 × 10 －6 The experiment was conducted in a low-oxygen atmosphere at MPa.

[0099] Furthermore, it is preferable to use a mixture of H2 / N2 gas and water droplets (hereinafter also referred to as WD) with an oxygen partial pressure of 1.04 × 10⁻⁶. －9 MPa ~ 1.20 × 10 －8 The experiment was conducted in a low-oxygen atmosphere at MPa.

[0100] It should be noted that when the calcination process is carried out in such an atmosphere, it is preferable to densify the piezoelectric ceramic at a low temperature by calcination at a temperature above 1050°C.

[0101] By densifying it at low temperatures, the growth of crystal nuclei can be suppressed, thereby obtaining perovskite-type compounds with low crystallinity.

[0102] In addition, the calcination process can be carried out at an oxygen partial pressure of 9.87 × 10⁻⁶. －2 MPa ~ 1.01 × 10 －1 The experiment was conducted under a high-oxygen atmosphere of MPa.

[0103] In this case, the process becomes the first and second steps of the manufacturing method of the piezoelectric ceramic of the present invention, in which a perovskite-type compound with low crystallinity can be obtained.

[0104] <Ceramic Electronic Components>

[0105] The ceramic electronic component of the present invention is characterized by having a piezoelectric body comprising the piezoelectric ceramic of the present invention and an external electrode.

[0106] Alternatively, a piezoelectric ceramic electronic component is preferred, wherein the piezoelectric element has an input section and an output section, and the voltage signal supplied to the input section is transformed and output from the output section.

[0107] The following are examples of ceramic electronic components.

[0108] Figure 1 This is a cross-sectional view, an example of a first way of schematically representing a ceramic electronic component.

[0109] As a first example, let's represent a piezoelectric actuator.

[0110] This piezoelectric actuator has a sintered laminated body 6 comprising piezoelectric elements 4a-4h formed from the piezoelectric ceramic of the present invention and internal electrodes 5a-5g. External electrodes 7a and 7b are formed on the outer surface of the sintered laminated body 6. Piezoelectric elements 4b, 4d, 4f, and 4h are polarized in the direction of arrow A, and piezoelectric elements 4c, 4e, and 4g are polarized in the direction of arrow B. That is, the piezoelectric elements 4b-4h are configured such that the hierarchical directions between each layer are opposite.

[0111] The sintered body 6 has piezoelectric bodies 4a to 4h and internal electrodes 5a to 5g stacked alternately. The internal electrodes 5a, 5c, 5e, and 5g are electrically connected to one external electrode 7a, and the internal electrodes 5b, 5d, and 5f are electrically connected to the other external electrode 7b.

[0112] There are no particular limitations on the internal and external electrode materials; Ag and Ag-Pd are preferred.

[0113] In this piezoelectric actuator, when a voltage is applied to the external electrodes 7a and 7b, the actuator displaces in the direction of arrow X using the reverse piezoelectric effect, releasing mechanical energy, and can control various electronic devices with high precision.

[0114] In the first embodiment, the piezoelectric bodies 4a to 4h are formed from the piezoelectric ceramic of the present invention. Therefore, the mechanical quality factor Qm is high and the limiting vibration velocity Vmax is high. Thus, self-heating is suppressed, the piezoelectric actuator can be extended in life, and stable piezoelectric characteristics can be ensured.

[0115] The piezoelectric actuator can be manufactured as follows.

[0116] A conductive paste is prepared to serve as both the internal and external electrodes.

[0117] In addition, ceramic green sheets are prepared using the slurry used in the molding process of the piezoelectric ceramic manufacturing method of the present invention described above.

[0118] A predetermined conductive pattern is formed by coating a conductive paste onto the surface of the ceramic green sheet using methods such as screen printing.

[0119] Next, ceramic green sheets with conductive patterns are stacked in a specified direction, and then ceramic green sheets without conductive patterns are placed on the top layer and hot-pressed to prepare a laminated body.

[0120] This concludes the forming process of the piezoelectric ceramic manufacturing method of the present invention.

[0121] Next, the laminated body is subjected to the calcination and degreasing treatment (arbitrary step) and calcination step of the piezoelectric ceramic manufacturing method of the present invention to obtain a laminated sintered body 6 with piezoelectric bodies 4a to 4h and internal electrodes 5a to 5g alternately arranged. In this stage, the piezoelectric ceramic of the present invention is manufactured in the laminated sintered body.

[0122] Subsequently, external electrodes 7a and 7b are formed on the outer surface of the laminated sintered body 6 using vacuum evaporation or other methods.

[0123] Subsequently, under heating, an electric field is applied to the external electrodes 7a and 7b for a specified time, and polarization is performed in the directions of arrow A and arrow B, thereby fabricating a piezoelectric actuator.

[0124] Figure 2 This is a cross-sectional view illustrating a second way of representing a ceramic electronic component.

[0125] As a second approach, an example of a piezoelectric transformer is shown.

[0126] The piezoelectric transformer is configured such that the piezoelectric element 8 formed from the piezoelectric ceramic of the present invention has an input section 9 and an output section 10, and the voltage signal supplied to the input section 9 is transformed and output from the output section 10.

[0127] Specifically, the input section 9 has a stacked structure in which piezoelectric bodies 11a-11j and internal electrodes 12a-12i are alternately stacked. External electrodes, i.e., input electrodes 13a and 13b, are formed on the upper surface of piezoelectric body 11a and the lower surface of piezoelectric body 11j. The internal electrodes 12a-12h are electrically connected to the input electrodes 13a and 13b. Furthermore, piezoelectric bodies 11a, 11c, 11e, 11g, and 11i are polarized in the direction of arrow D, while piezoelectric bodies 11b, 11d, 11f, 11h, and 11j are polarized in the direction of arrow C. That is, the piezoelectric bodies 11a-11j are configured such that the polarization direction between each layer is opposite.

[0128] In addition, the output section 10 is a single-layer structure without internal electrodes, and the external electrode, i.e. the output electrode 14, is formed on one end face and is polarized in the direction of arrow E.

[0129] When an AC voltage at the resonant frequency is applied to the input electrodes 13a and 13b, the piezoelectric transformer formed in this way converts the voltage into mechanical energy through the reverse piezoelectric effect, thus exciting mechanical vibration. Then, this mechanical vibration is converted into electrical energy using the piezoelectric effect, and a voltage signal boosted according to the capacity ratio of the input section 9 and the output section 10 is output from the output electrode 14.

[0130] In the second embodiment, the piezoelectric elements 8, 11a to 11j are formed from the piezoelectric ceramic of the present invention. Therefore, the mechanical quality factor Qm is high and the limiting vibration velocity Vmax is high, thereby suppressing self-heating, extending the life of the piezoelectric transformer, and ensuring stable piezoelectric characteristics.

[0131] In the second approach, there are no particular limitations on the internal electrode material and the external electrode material; Ag and Ag-Pd can be preferred.

[0132] Furthermore, this piezoelectric transformer is the same as the piezoelectric actuator described above and can be manufactured as follows.

[0133] A conductive paste is prepared to serve as both the internal and external electrodes.

[0134] Furthermore, ceramic green sheets are prepared using the slurry used in the molding process of the piezoelectric ceramic manufacturing method of the present invention described above.

[0135] A conductive paste is applied to the surface of the ceramic green sheet using a screen printing method or similar technique, forming a predetermined conductive pattern at the location corresponding to the input section 9.

[0136] Next, after stacking a specified number of ceramic green sheets with conductive patterns, hot pressing is performed to prepare a laminated body.

[0137] This concludes the forming process of the piezoelectric ceramic manufacturing method of the present invention.

[0138] Next, the laminated body is subjected to the calcination and degreasing treatment (an arbitrary step) and calcination step of the piezoelectric ceramic manufacturing method of the present invention, to obtain a laminated structure in which the input part 9 is a piezoelectric element 11a-11j and internal electrodes 12a-12i are alternately arranged, and the output part 10 is a sintered body with a single-layer structure. In this stage, the piezoelectric ceramic of the present invention is manufactured in the sintered body.

[0139] Subsequently, using vacuum evaporation or the like, input electrodes 13a and 13b, which serve as external electrodes, are formed on the upper and lower surfaces of the input section 9, and then an output electrode 14, which serves as an external electrode, is formed on the end face of the output section 10.

[0140] Subsequently, an electric field is applied between the input electrodes 13a and 13b and the output electrode 14 for a predetermined time under heating, causing the output section 10 to be polarized in the direction of arrow E.

[0141] Furthermore, after heating to a specified temperature, an electric field is applied between the input electrode 13a and the input electrode 13b for a specified time in such a way that the polarization direction of the input section 9 is opposite between each layer, thereby performing polarization treatment and fabricating a piezoelectric transformer.

[0142] Figure 3 This is a cross-sectional view schematically representing a third-party example of a ceramic electronic component.

[0143] As a third approach, another example of a piezoelectric transformer is shown.

[0144] In the third embodiment, similar to the second embodiment, the piezoelectric body 15 formed from the piezoelectric ceramic of the present invention has an input portion 16 and an output portion 17, and the voltage signal supplied to the input portion 16 is transformed and output from the output portion 17.

[0145] Furthermore, both the input section 16 and the output section 17 of this piezoelectric transformer have a stacked structure with internal electrodes, and the distance between the internal electrodes is different in the input section 16 and the output section 17. That is, the input section 16 has a stacked structure in which piezoelectric bodies 18a-18e and internal electrodes 19a-19d are alternately stacked, and input electrodes 20a and 20b are formed on the side of the input section 16. Specifically, the internal electrodes 19a and 19c are electrically connected to one of the input electrodes 20a, and the internal electrodes 19b and 19d are electrically connected to the other input electrode 20b. Moreover, the piezoelectric bodies 18b-18d are polarized in opposite directions between each layer, either in the direction of arrow F or arrow G.

[0146] On the other hand, the output section 17 has a stacked structure in which piezoelectric elements 21a-21i and internal electrodes 22a-22i are alternately stacked, and output electrodes 23a and 23b are formed on the side of the output section 17. Specifically, the internal electrodes 22a, 22c, 22e, 22g, and 22i are electrically connected to one of the output electrodes 23a, and the internal electrodes 22b, 22d, 22f, and 22h are electrically connected to the other output electrode 23b. Furthermore, the piezoelectric elements 21b-21i are polarized in opposite directions between each layer, either in the direction of arrow H or arrow I.

[0147] Furthermore, in the third method, the distance between the internal electrodes of the output section 17 is made different between the output section 17 and the input section 16 by making the distance between the internal electrodes of the output section 17 22a to 22i shorter than the distance between the internal electrodes of the input section 16 19a to 19d.

[0148] For a piezoelectric transformer formed in this way, when an AC voltage of the resonant frequency is applied to the input electrodes 20a and 20b, it is converted into mechanical energy using the reverse piezoelectric effect, thus exciting mechanical vibration. Then, this mechanical vibration is converted into electrical energy using the piezoelectric effect, and a voltage signal with a voltage drop according to the capacity ratio is output from the output electrodes 23a and 23b.

[0149] Furthermore, in the third embodiment, the piezoelectric elements 18a-18e and 21a-21i are formed from the piezoelectric ceramic of the present invention. As a result, similar to the second embodiment, the mechanical quality factor Qm is high and the limiting vibration velocity Vmax is high. Therefore, self-heating is suppressed, the piezoelectric transformer can have a long lifespan, and the stable piezoelectric characteristics can be ensured.

[0150] In the third approach, there are no particular limitations on the internal electrode material and the external electrode material; Ag and Ag-Pd can be preferred.

[0151] In addition, the piezoelectric transformer can be manufactured in the same manner as the piezoelectric actuator and piezoelectric transformer described above.

[0152] A conductive paste is prepared to serve as both the internal and external electrodes.

[0153] In addition, using the slurry in the molding process of the piezoelectric ceramic manufacturing method of the present invention, two types of ceramic green sheets (input ceramic green sheet and output ceramic green sheet) with different thicknesses are prepared.

[0154] Conductive paste is applied to the surface of these ceramic green sheets using screen printing or other methods to form a specified conductive pattern. Then, a specified number of ceramic green sheets with conductive patterns are stacked, and ceramic green sheets without conductive patterns are placed at both ends and hot-pressed to prepare a laminated body.

[0155] This concludes the forming process of the piezoelectric ceramic manufacturing method of the present invention.

[0156] Next, the laminated body is subjected to the calcination and degreasing treatment (an arbitrary step) and calcination step in the manufacturing method of the piezoelectric ceramic of the present invention, resulting in a sintered body with the following characteristics: the input section 16 is a laminated structure in which piezoelectric bodies 18a-18e and internal electrodes 19a-19d are alternately arranged, and the output section 17 is a laminated structure in which piezoelectric bodies 21a-21i and internal electrodes 22a-22i are alternately arranged, with different inter-electrode distances between the internal electrodes. In this stage, the piezoelectric ceramic of the present invention is manufactured in the sintered body.

[0157] Subsequently, using vacuum evaporation or similar methods, input electrodes 20a and 20b, serving as external electrodes, and output electrodes 23a and 23b, serving as external electrodes, are formed on both sides of the input section 16 and the output section 17. Then, under heating, an electric field is applied for a predetermined time with opposite polarization directions between each layer to perform polarization treatment, thereby fabricating a piezoelectric transformer.

[0158] It should be noted that the ceramic electronic component of the present invention is not limited to the embodiments described above. For example, as another example of a ceramic electronic component, it can also be formed as a piezoelectric resonator, a piezoelectric filter, etc.

[0159] Example

[0160] The following provides more specific embodiments of the piezoelectric ceramics of the present invention. It should be noted that the present invention is not limited to these embodiments.

[0161] (Sample numbers 1-4)

[0162] [Sample Preparation]

[0163] As raw materials for ceramic materials, PbO, ZrO2, TiO2, Nb2O5, and MnCO3 are prepared. The raw materials are weighed such that their main components after calcination are PbO (67.80–68.63 wt%), ZrO2 (17.20–17.36 wt%), TiO2 (11.49–12.10 wt%), MnO (0.59–0.64 wt%), and Nb2O5 (1.97–2.06 wt%).

[0164] Next, the weighed material was fed into a ball mill along with some stabilized zirconia balls and wet-mixed and pulverized for 190 minutes.

[0165] Subsequently, after dehydration and drying, the material is pre-fired at 1030℃ to prepare pre-fired ceramic powder.

[0166] Next, the pre-fired ceramic powder is pulverized and then organic binders such as polyvinyl alcohol resin are added. The mixture is then wet-dispersed and mixed without media to prepare a slurry.

[0167] Then, granulation powder for compression molding is prepared by spray drying. Ceramic molded bodies are prepared by compression molding of the granulation powder.

[0168] The ceramic molded body was placed in a firing pan and then placed in a furnace for calcination and degreasing. The calcination and degreasing process was carried out in an atmospheric atmosphere using a muffle furnace. The calcination conditions involved heating to a furnace temperature of 450°C at a rate of 0.5°C / min, holding for 2 hours, and then cooling down at a rate of 1°C / min to 6°C / min to complete the calcination and degreasing process.

[0169] Next, the main calcination (calcination process) is carried out. As for the calcination conditions, the furnace temperature is raised to 300°C at a heating rate of 3°C / min and held for 1 hour. The temperature is then raised to 1100°C to 1150°C at a heating rate of 3°C / min when the calcination atmosphere is O2, and to 1050°C when the atmosphere is replaced with N2 or H2 / N2 mixed gas and WD. After holding for 8 hours, the calcination process is completed by cooling down at a cooling rate of 1°C / min to 6°C / min.

[0170] The oxygen concentration during the calcination process is shown below.

[0171] Sample No. 1: 1.04 × 10 －9 MPa ~ 1.20 × 10 －8 MPa

[0172] Sample No. 2: 5.74 × 10 －7 MPa ~ 3.28 × 10 －6 MPa

[0173] Sample No. 3: 9.87 × 10 －2 MPa ~ 1.01 × 10 －1 MPa

[0174] Sample No. 4: 9.87 × 10 －2 MPa ~ 1.01 × 10 －1 MPa

[0175] Using a cutting machine, the samples were cut into shapes measuring 13mm in length, 3mm in width, and 0.9mm in thickness for piezoelectric property evaluation. The cut samples were polarized for 30 minutes using an oil bath and other methods at a temperature of 150℃ and an electric field strength of 3kV / mm.

[0176] (Sample numbers 5 and 6)

[0177] As raw materials for ceramic materials, PbO, ZrO2, TiO2, Nb2O5, and MnCO3 are prepared. Furthermore, the main components of the calcined ceramic material are weighed in such a manner that PbO (67.80–68.63 wt%), ZrO2 (17.20–17.36 wt%), TiO2 (11.49–12.10 wt%), MnO (0.59–0.64 wt%), and Nb2O5 (1.97–2.06 wt%).

[0178] Next, the weighed material was fed into a ball mill along with some stabilized zirconia balls and wet-mixed and pulverized for 190 minutes.

[0179] Subsequently, after dehydration and drying, the powder is pre-fired at 1030℃ to prepare pre-fired ceramic powder.

[0180] Next, the pre-fired ceramic powder is pulverized, and dispersant and defoamer are added. The powder is then wet-pulverized in a container containing some stabilized zirconia balls to prepare a slurry.

[0181] The pulverization time was 12 hours for sample number 5 and 36 hours for sample number 6.

[0182] Furthermore, the slurry is filled into a resin mold and dried for 24 hours to obtain a cast body.

[0183] The cast body was placed in a calcining pan and then placed in a furnace for calcination and degreasing. The calcination and degreasing process was carried out in an atmospheric atmosphere using a muffle furnace. The calcination conditions were as follows: the temperature was increased to 80°C at a rate of 3°C / min; then increased to 400°C at a rate of 0.25°C / min and held for 2 hours; then further increased to 600°C at a rate of 3°C / min and held for 1 hour; finally, the temperature was decreased at a rate of 1°C / min to 5°C / min to complete the calcination and degreasing process.

[0184] Next, the main calcination (calcination process) is carried out. As calcination conditions, the furnace temperature is raised to 300°C at a heating rate of 3°C / min and held for 1 hour. After the calcination atmosphere is replaced with N2, the furnace temperature is raised to 1050°C at a heating rate of 3°C / min and held for 8 hours. Then, the temperature is lowered at a cooling rate of 1°C / min to 6°C / min to complete the main calcination treatment.

[0185] The oxygen concentration for the calcination process is as follows.

[0186] Sample No. 5: 5.74 × 10 －7 MPa ~ 3.28 × 10 －6 MPa

[0187] Sample No. 6: 5.74 × 10 －7MPa ~ 3.28 × 10 －6 MPa

[0188] The samples were cut into shapes measuring 13mm in length, 3mm in width, and 0.9mm in thickness using a cutting machine for piezoelectric property evaluation. The cut samples were polarized for 30 minutes using an oil bath at 150°C and an electric field strength of 3kV / mm.

[0189] [Sample Evaluation]

[0190] The grain diameter of the sintered piezoelectric ceramic was determined by observing the surface of the sintered sample using SEM, measuring the volume distribution of approximately 80 particles, and setting it as the D50 value for the Heywood diameter.

[0191] The crystallinity of the sintered piezoelectric ceramics was evaluated using an X-ray diffraction apparatus with the following conditions: CuKα tube, tube voltage 45kV, tube current 200mA, scanning angle 10-70°, and sampling width 0.02°. The evaluation was performed using the lumped method.

[0192] The specific permittivity (ε33T / ε0) and electromechanical coupling coefficient k of the micro-electric field in piezoelectric properties 31 The measurement was performed using a blockage detector (Agilent Technologies: 4294A) and the resonance-anti-resonance method.

[0193] As a piezoelectric property driven by large resonant amplitude, the elastic compliance S 11 E and the ultimate vibration velocity Vmax were determined using the rated current measurement method.

[0194] After the sintered piezoelectric ceramic was pressed into shape, the phenomenon was analyzed by fluorescence X-ray to identify the composition, confirming that it contained at least Pb, Zr, Ti, Mn and Nb.

[0195] The manufacturing conditions and evaluation results for each sample number are summarized in Table 1.

[0196]

[0197] When O2 with high oxygen partial pressure is calcined (oxygen partial pressure: 9.87 × 10⁻⁶), －2 MPa or above, 1.01×10 －1 Below MPa, the inhibition of Mn acceptor solid solution at the B site of PZT reduces the generation of oxygen vacancies that promote grain growth, resulting in smaller grain diameters (samples 3 and 4). Samples 3 and 4 show high voltage characteristics and high Vmax.

[0198] Figure 4 This is an electron microscope image of the piezoelectric ceramic prepared from sample number 3.

[0199] Under an O2 atmosphere, by setting the calcination temperature to above 1100℃, thus achieving... Figure 4 The diagram shows that a dense structure can be obtained.

[0200] In addition, a higher Vmax (sample number 4) was observed by setting the calcination temperature to 1150°C.

[0201] On the other hand, in samples 5 and 6, where the particle size of the pre-calcined powder was reduced by wet pulverization, under a low oxygen partial pressure N2 atmosphere (5.74 × 10⁻⁶) with a sintering-promoting effect based on increased oxygen cavitation, the particle size was reduced. －7 MPa ~ 3.28 × 10 －6 By adjusting the calcination temperature to 1050℃, which is lower than that of O2 calcination, densification can be achieved without causing grain growth.

[0202] This demonstrates the high voltage characteristics and high Vmax.

[0203] Figure 5 This is a graph comparing the X-ray diffraction peaks of the piezoelectric ceramic plates prepared from samples 1 to 4. The vertical axis is offset to facilitate the comparison of samples 1 to 4.

[0204] It can be seen that in samples No. 3 and 4 calcined under oxygen atmosphere, the X-ray diffraction peaks of the main peak of the PZT tetragonal phase on the (101) and (110) planes are unbranched, and the diffraction pattern is a single peak.

[0205] On the other hand, it can be seen that in the samples No. 1 and 2 calcined under low oxygen partial pressure (H2 / N2+WD) atmosphere or low oxygen partial pressure (N2) atmosphere, the X-ray diffraction peaks are clearly divided into (101) plane and (110) plane.

[0206] Therefore, it can be concluded that samples 3 and 4, compared with samples 1 and 2, can suppress the crystallization of perovskite-type compounds.

[0207] Figure 6 This is a graph comparing the X-ray diffraction peaks of piezoelectric ceramic plates prepared from samples 2, 5, and 6. The vertical axis is offset to facilitate comparison of samples 2, 5, and 6.

[0208] It can be seen that in samples 5 and 6, which were calcined after being pulverized from pre-fired ceramic powder, the main peaks of the PZT tetragonal phase, namely the X-ray diffraction peaks of the (101) and (110) planes, were unbranched, and the diffraction pattern was a single peak. On the other hand, in sample 2, which was calcined without pulverizing the pre-fired ceramic powder, X-ray diffraction peaks that were clearly divided into the (101) and (110) planes can be seen.

[0209] Therefore, it can be concluded that in samples 5 and 6, the crystallization of the perovskite-type compound was suppressed compared with that in sample 2.

[0210] Figure 7 This is a coordinate graph showing the relationship between the vibration velocity and Qm of the piezoelectric ceramics prepared by sample numbers 1 to 4 under resonant drive.

[0211] Figure 8 This is a coordinate graph showing the relationship between the vibration velocity and Qm of the piezoelectric ceramics prepared by sample numbers 2, 5, and 6 under resonance drive.

[0212] These coordinate graphs show that the piezoelectric ceramics (samples 3-6) composed of low-crystallinity compounds with unbranched X-ray diffraction peaks of the PZT tetragonal phase, namely the (101) and (110) planes, exhibit high Qm values ​​at high vibration velocities (above 0.5 m / s).

[0213] Figure 9 This is a coordinate graph showing the relationship between the vibration velocity and heat generation when the piezoelectric ceramics prepared by sample numbers 1 to 4 are driven by resonance.

[0214] Figure 10 This is a coordinate graph showing the relationship between the vibration velocity and heat generation when the piezoelectric ceramics prepared by sample numbers 2, 5, and 6 are driven by resonance.

[0215] Figure 9 , 10 The vibration velocity [m / s] at the moment when the temperature reaches 20℃ is the ultimate vibration velocity Vmax.

[0216] These coordinate graphs show that the piezoelectric ceramics (samples 3-6) composed of compounds with unbranched X-ray diffraction peaks of the PZT tetragonal phase, namely the (101) and (110) planes, with a single diffraction pattern, and low crystallinity, have high limiting vibrational velocities Vmax.

[0217] As shown in Table 1, the elastic compliance S of sample No. 4, which was densified under a high oxygen partial pressure O2 calcination atmosphere, and samples No. 5 and 6, which were prepared by pulverizing the pre-calcined powder, is... 11 E Compared to sample numbers 1 and 2, S 11 E Small indicates that the piezoelectric ceramic has hardened.

[0218] In other words, reversal is difficult in the 90° region, and the reduction of Qm at high vibration velocities (above 0.5 m / s) is suppressed. Figure 7 , Figure 8 Therefore, the limiting vibration velocity becomes higher. Figure 9 , Figure 10 ).

[0219] Symbol Explanation

[0220] 04a~4h: Piezoelectric element

[0221] 5a~5g: Internal electrodes

[0222] 6: Layered sintered body

[0223] 7a, 7b: External electrodes

[0224] 8, 11a~11j: Piezoelectric elements

[0225] 9: Input Section

[0226] 10: Output Department

[0227] 12a~12i: Internal electrodes

[0228] 13a, 13b: Input electrodes

[0229] 14: Output electrode

[0230] 15: Piezoelectric element

[0231] 16: Input Section

[0232] 17: Output Section

[0233] 18a~18e, 21a~21i: Piezoelectric elements

[0234] 19a~19d, 22a~22i: Internal electrodes

[0235] 20a, 20b: Input electrodes

[0236] 23a, 23b: Output electrodes

Claims

1. A piezoelectric ceramic, characterized in that, It is a piezoelectric ceramic composed of perovskite compounds, wherein the perovskite compounds consist of Pb, Zr, Ti, Mn and Nb, with Mn content ranging from 0.019 mol% to 0.041 mol% and Nb content ranging from 0.048 mol% to 0.057 mol%. For the piezoelectric ceramic, the vibration velocity at the vibration node of the oscillator under resonant driving at room temperature when the temperature rises to 20°C is taken as the limiting vibration velocity Vmax. In the manufacturing of the piezoelectric ceramic, the specific surface area, based on the BET method, is 2.9–5.3 m² during the pulverization process. 2 The material is pulverized in a manner that produces a powder, and the calcination process uses N2 gas with an oxygen partial pressure of 5.74 × 10⁻⁶ g. －7 MPa ~ 3.28 × 10 －6 The process is carried out in a low-oxygen atmosphere of MPa, thereby making the limiting vibration velocity Vmax of the piezoelectric ceramic above 0.84 m / s.

2. A ceramic electronic component, characterized in that, It includes the piezoelectric element and external electrode of the piezoelectric ceramic as described in claim 1.

3. The ceramic electronic component according to claim 2 is a piezoelectric ceramic electronic component, wherein the piezoelectric element has an input section and an output section, and the voltage signal supplied to the input section is transformed and output from the output section.

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