KR20230120694A - Piezoelectric ceramics sintered body, method for preparing the same, multilayered piezoelectric composite containing the same and piezoelectic speaker - Google Patents

Abstract

The present invention relates to a sintered piezoelectric ceramics, a manufacturing method thereof, a multilayer piezoelectric body including the same, and a piezoelectric speaker including the same. A sintering additive is added:
[Formula 1]
xPb((Zn _0.8 Ni _0.2 ) _1/3 Nb _2/3 )O ₃ -(1-x)Pb(Zr _0.5 Ti _0.5 )O ₃ (PZNN-PZT)
(0.10<x<0.30).

Description

Piezoelectric ceramics sintered body, manufacturing method thereof, laminated piezoelectric body including the same, and piezoelectric speaker including the same

The present invention relates to a sintered piezoelectric ceramics, a manufacturing method thereof, a laminated piezoelectric body including the same, and a piezoelectric speaker including the same.

Recently, the need for miniaturization, thinning, and high efficiency of internal electronic parts is increasing in order to integrate many functions at high density in a limited size of mobile IT products. Nowadays, complex electronic components are often replaced with piezoelectric materials, and research to develop acoustic components, which are essential components, is being actively conducted.

Currently commercialized dynamic speakers use magnetic diaphragms and coils, so there is a limit to miniaturization, and there is a problem of high power consumption due to current driving. Piezoelectric speakers, which are actuator elements using vibration, are emerging as they have the advantages of being thin, light, and consuming less power.

In order to apply piezoelectric materials as acoustic actuators, it is fundamentally important to develop materials with high piezoelectric constants and conversion efficiencies, and to realize low driving voltages, it is essential to manufacture multilayer piezoelectric materials. Since the ceramic layer and internal electrodes are fired simultaneously when manufacturing a multilayer piezoelectric body, Ag/Pd electrodes with a high Pd content, which is expensive when sintered at high temperatures, must be used, and characteristic degradation caused by compositional changes in the material itself due to volatilization of PbO at high temperatures There is a problem or a problem in which structural deformation such as bending or cracking occurs. Accordingly, there is a demand for development of a material capable of being sintered at a low temperature in order to prevent deterioration of device characteristics.

In addition, when manufacturing a piezoelectric speaker including this, in the case of a speaker using a metal plate, alloy, or piezoelectric film for the diaphragm constituting the existing piezoelectric speaker, the sound quality is poor and the area of the diaphragm must be very large, making it difficult to miniaturize and not suitable for replacing the existing dynamic speaker. not. Therefore, it is essential to develop a piezoelectric speaker with an improved structure in order to manufacture a miniaturized piezoelectric speaker as well as minimize sound distortion.

The foregoing background art is technical information that the inventor possessed for derivation of the present invention or acquired during the derivation process of the present invention, and cannot necessarily be said to be known art disclosed to the general public prior to filing the present invention.

The present invention is to solve the above problems, and an object of the present invention is to provide a piezoelectric ceramics sintered body capable of being sintered at a low temperature, a manufacturing method thereof, a laminated piezoelectric body including the same, and a piezoelectric speaker including the same.

However, the problem to be solved by the present invention is not limited to those mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

A piezoelectric ceramics sintered body according to an embodiment of the present invention is obtained by adding a low-temperature sintering additive to the PZNN-PZT ceramics composition represented by Formula 1 below:

[Formula 1]

xPb((Zn _0.8 Ni _0.2 ) _1/3 Nb _2/3 )O ₃ -(1-x)Pb(Zr _0.5 Ti _0.5 )O ₃ (PZNN-PZT)

(0.10<x<0.30).

In one embodiment, the x may be 0.20 to 0.25.

In one embodiment, the low-temperature sintering additive may include at least one selected from the group consisting of lithium carbonate (Li ₂ CO ₃ ), boron carbonate (B ₂ CO ₃ ), and cadmium carbonate (CdCO ₃ ). there is.

In one embodiment, the low-temperature sintering additive may be in the range of 0.01% by weight to 0.5% by weight based on the total weight of the piezoelectric ceramics sintered body.

In a method for manufacturing a sintered piezoelectric ceramics body according to another embodiment of the present invention, raw material powders including PbO, ZrO ₂ , TiO ₂ , ZnO, NiO, and Nb ₂ O ₅ are put into a solvent and wet-mixed so as to have a compositional formula of Formula 1 below Preparing a mixture by law; drying and then calcining the mixture to form a first powder; forming a second powder by adding a low-temperature sintering additive to the first powder, wet mixing, and then drying; and molding and sintering the second powder to form a piezoelectric body:

[Formula 1]

xPb((Zn _0.8 Ni _0.2 ) _1/3 Nb _2/3 )O ₃ -(1-x)Pb(Zr _0.5 Ti _0.5 )O ₃ (PZNN-PZT)

(0.10<x<0.30).

In one embodiment, the x may be 0.20 to 0.25.

In one embodiment, preparing the mixture may include wet mixing the raw material powder with at least one solvent selected from the group consisting of methanol, ethanol, isopropanol, and distilled water for 10 to 40 hours.

According to one embodiment, in the first powder forming step, a PZNN-PZT-based piezoelectric ceramics composition is prepared by first calcining all materials except Pb in the mixture, then mixing the calcined composition powder and Pb and performing secondary calcining. it may be

According to one embodiment, the first calcination temperature may be performed in a temperature range of 1000 °C to 1100 °C, and the second calcination temperature may be performed in a temperature range of 700 °C to 760 °C.

In one embodiment, the low-temperature sintering additive may include at least one selected from the group consisting of lithium carbonate (Li ₂ CO ₃ ), boron carbonate (B ₂ CO ₃ ), and cadmium carbonate (CdCO ₃ ). there is.

In one embodiment, the low-temperature sintering additive may be added in a range of 0.01 wt% to 0.5 wt% based on the total weight of the piezoelectric ceramics sintered body.

In one embodiment, the sintering may be performed at a temperature of 850 °C to 900 °C for 1 hour to 10 hours.

A multilayer piezoelectric body according to another embodiment of the present invention includes a piezoelectric ceramics sintered body layer manufactured by the piezoelectric ceramics sintered body or the method of manufacturing the piezoelectric ceramics sintered body according to one embodiment of the present invention; and an electrode layer formed on at least one of upper and lower surfaces of the piezoelectric ceramics sintered body layer. it could be

In one embodiment, the piezoelectric ceramics sintered body layer may be laminated in two to ten layers.

In one embodiment, the thickness of one layer of the piezoelectric ceramics sintered body may be 20 μm to 40 μm.

A piezoelectric speaker according to another embodiment of the present invention includes a laminated piezoelectric body according to an embodiment of the present invention; a diaphragm layer formed under the multilayer piezoelectric body; and a frame surrounding upper and lower side surfaces of the diaphragm.

A method of manufacturing a piezoelectric speaker according to another embodiment of the present invention includes bonding two types of films having different vibration characteristics with an epoxy material; Soldering a portion of the laminated piezoelectric electrode of an embodiment of the present invention; attaching the soldered multilayer piezoelectric body and the laminated film of the two types; and wrapping and attaching the periphery of the two types of laminated films with a frame.

The sintered piezoelectric ceramics according to an embodiment of the present invention can be sintered at a low temperature, so that structural deformation does not occur when manufactured as a multilayer piezoelectric body, and sintering can be performed at a low temperature without a problem of characteristic degradation due to a composition change of the material due to volatilization of PbO, It can exhibit a high energy conversion constant, a high piezoelectric strain constant (d33), a low permittivity and a high electromechanical coupling coefficient.

By adding the low-temperature sintering additive according to an embodiment of the present invention, it is possible to sinter at a low temperature of 900 ° C or less, so that structural deformation does not occur when manufactured as a layered piezoelectric body, and there is no problem of characteristic degradation due to compositional change of the material due to volatilization of PbO. It is possible to implement an acoustic actuator device having constant and conversion efficiency.

In addition, the piezoelectric speaker including the laminated piezoelectric body manufactured using the PZNN-PZT-based composition to which lithium carbonate (Li ₂ CO ₃ ) is added according to an embodiment is a diaphragm that amplifies vibration generated from an acoustic actuator element, and is mutually It has an acoustic diaphragm structure in which a PEEK film with different vibration characteristics and a smaller size silicone rubber film are laminated, so that the acoustic characteristics are improved.

Therefore, a PZNN-PZT-based piezoelectric ceramic composition capable of being sintered at a low temperature according to the present invention and a functionally excellent piezoelectric speaker having an improved structure using the same can be manufactured and applied to electronic devices as a miniaturized acoustic actuator component to replace the existing dynamic speaker. It is expected that there will be

1 is a flow chart showing a manufacturing process of a piezoelectric ceramics sintered body according to an embodiment of the present invention.
2 is a graph showing XRD analysis results of PZNN-PZT sintered bodies according to PZNN content prepared according to an embodiment of the present invention.
3 is a SEM image of a PZNN-PZT sintered body according to a doping content of lithium carbonate (Li2CO3) prepared according to an embodiment of the present invention.
4 shows the results of measuring the electrical properties of the PZNN-PZT sintered body according to the doping content of lithium carbonate (Li2CO3) prepared according to an embodiment of the present invention.
5 is a SEM image of a fracture surface of a multilayer piezoelectric body manufactured according to an embodiment of the present invention.
6 shows a plan view of a piezoelectric speaker according to an embodiment of the present invention.
7 is a cross-sectional view of a piezoelectric speaker according to an acoustic diaphragm structure having different sizes manufactured according to an embodiment of the present invention.
FIG. 8 shows simulation analysis results of frequency response characteristics of the piezoelectric speaker of FIG. 7 .

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. However, since various changes can be made to the embodiments, the scope of the patent application is not limited or limited by these embodiments. It should be understood that all changes, equivalents or substitutes to the embodiments are included within the scope of rights.

Terms used in the examples are used only for descriptive purposes and should not be construed as limiting. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as "include" or "have" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art to which the embodiment belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in the present application, they should not be interpreted in an ideal or excessively formal meaning. don't

In addition, in the description with reference to the accompanying drawings, the same reference numerals are given to the same components regardless of reference numerals, and overlapping descriptions thereof will be omitted. In describing the embodiment, if it is determined that a detailed description of a related known technology may unnecessarily obscure the gist of the embodiment, the detailed description will be omitted.

In addition, in describing the components of the embodiment, terms such as first, second, A, B, (a), and (b) may be used. These terms are only used to distinguish the component from other components, and the nature, order, or order of the corresponding component is not limited by the term.

Components included in one embodiment and components having common functions will be described using the same names in other embodiments. Unless stated to the contrary, descriptions described in one embodiment may be applied to other embodiments, and detailed descriptions will be omitted to the extent of overlap.

Hereinafter, the piezoelectric ceramics sintered body of the present invention, its manufacturing method, the laminated piezoelectric body including the same, and the piezoelectric speaker including the same will be described in detail with reference to examples and drawings. However, the present invention is not limited to these examples and drawings.

A piezoelectric ceramics sintered body according to an embodiment of the present invention is obtained by adding a low-temperature sintering additive to the PZNN-PZT ceramics composition represented by Formula 1 below:

[Formula 1]

xPb((Zn _0.8 Ni _0.2 ) _1/3 Nb _2/3 )O ₃ -(1-x)Pb(Zr _0.5 Ti _0.5 )O ₃ (hereinafter referred to as “PZNN-PZT”)

(0.10<x<0.30).

The piezoelectric ceramics sintered body of the present invention is composed of a (Pb, Zn, Ni, Nb)-(Pb,Zr,Ti) phase, and a low-temperature sintering additive is added to a compound represented by PZNN-PZT to xPb ((Zn _0.8 Ni _0.2 ) _{1 /3} Nb _2/3 )O ₃ -(1-x)Pb(Zr _0.5 Ti _0.5 )O ₃ + Y wt% It has a composition formula of low temperature sintering additive (0.10<x<0.30, 0.01<Y<0.5).

In one embodiment, x is from 0.10 to 0.30; 0.15 to 0.30; 0.20 to 0.30; 0.10 to 0.25; 0.15 to 0.25; 0.20 to 0.25; 0.10 to 0.20; 0.15 to 0.20; Or it may be 0.20 to 0.25.

Preferably, the x may be 0.20 to 0.25.

In one embodiment, the low-temperature sintering additive has a low melting point and induces the formation of a liquid phase during sintering to densify the surface of ceramic particles, thereby providing excellent piezoelectric properties even at a low temperature.

In one embodiment, the low-temperature sintering additive may include at least one selected from the group consisting of lithium carbonate (Li ₂ CO ₃ ), boron carbonate (B ₂ CO ₃ ), and cadmium carbonate (CdCO ₃ ). there is.

Preferably, the low-temperature sintering additive may be lithium carbonate (Li ₂ CO ₃ ).

Accordingly, the piezoelectric ceramics sintered body of the present invention is preferably xPb((Zn _0.8 Ni _0.2 ) _1/3 Nb _2/3 )O ₃ -(1-x)Pb(Zr _0.5 Ti _0.5 )O ₃ + Y It may have a composition formula of wt% Li ₂ CO ₃ (0.10<x<0.30, 0.01<Y<0.5).

In one embodiment, the low-temperature sintering additive may be in the range of 0.01% by weight to 0.5% by weight based on the total weight of the piezoelectric ceramics sintered body. Preferably, it may be in the range of 0.1% by weight to 0.3% by weight. If the low-temperature sintering additive is less than 0.01% by weight relative to the total weight of the piezoelectric ceramics sintered body, the effect of densifying the surface of ceramic particles cannot be exhibited when sintered at a low temperature. Grain boundary segregation within the crystal may hinder grain growth and degrade the piezoelectric properties of the material.

The sintered piezoelectric ceramics according to an embodiment of the present invention can be sintered at a low temperature, so that structural deformation does not occur when manufactured as a multilayer piezoelectric body, and sintering can be performed at a low temperature without a problem of characteristic degradation due to a composition change of the material due to volatilization of PbO, It can exhibit a high energy conversion constant, a high piezoelectric strain constant (d33), a low permittivity and a high electromechanical coupling coefficient.

A method for manufacturing a sintered piezoelectric ceramics body according to another embodiment of the present invention is a wet mixing method in which raw material powders including PbO, ZrO ₂ , TiO ₂ , ZnO, NiO, and Nb ₂ O are put into a solvent so as to have a composition formula of Formula 1 below preparing a mixture; drying and then calcining the mixture to form a first powder; forming a second powder by adding a low-temperature sintering additive to the first powder, wet mixing, and then drying; and molding and sintering the second powder to form a piezoelectric body:

[Formula 1]

xPb((Zn _0.8 Ni _0.2 ) _1/3 Nb _2/3 )O ₃ -(1-x)Pb(Zr _0.5 Ti _0.5 )O ₃ (PZNN-PZT)

(0.10<x<0.30).

1 is a flow chart showing a manufacturing process of a piezoelectric ceramics sintered body according to an embodiment of the present invention.

Referring to FIG. 1 , a method for manufacturing a piezoelectric ceramics sintered body according to an embodiment of the present invention includes preparing a mixture (110), forming a first powder (120), forming a second powder (130), and forming a piezoelectric body. (140).

In one embodiment, in the mixture preparation step 110, a raw material powder containing PbO, ZrO ₂ , TiO ₂ , ZnO, NiO, and Nb ₂ O ₅ is put into a solvent so as to have a compositional formula of Formula 1 below, and a wet mixing method Steps to prepare the mixture as:

[Formula 1]

xPb((Zn _0.8 Ni _0.2 ) _1/3 Nb _2/3 )O ₃ -(1-x)Pb(Zr _0.5 Ti _0.5 )O ₃ (PZNN-PZT)

(0.10<x<0.30).

The PZT-PZNN powder is made of raw material powder containing PbO, ZrO ₂ , TiO ₂ , ZnO, NiO and Nb ₂ O ₅ .

Specifically, the PZT-PZNN mixture contains 0.1 to 1 mol of ZrO ₂ , 0.1 to 1 mol of TiO ₂ , 0.01 to 0.5 mol of NiO, and 0.01 to 0.5 mol of ZnO based on 1 mol of PbO. (mol) and Nb ₂ O ₅ 0.1 to 1 mol (mol).

When the raw material powder is mixed in an amount outside the above range, a compound other than the PZT-PZNN compound may be produced.

In one embodiment, x is from 0.10 to 0.30; 0.15 to 0.30; 0.20 to 0.30; 0.10 to 0.25; 0.15 to 0.25; 0.20 to 0.25; 0.10 to 0.20; 0.15 to 0.20; Or it may be 0.20 to 0.25.

Preferably, the x may be 0.20 to 0.25.

In one embodiment, preparing the mixture may include wet mixing the raw material powder with at least one solvent selected from the group consisting of methanol, ethanol, isopropanol, and distilled water for 10 to 40 hours.

The present invention uses a general solid-state reaction method. The solid-state reaction method is to obtain a piezoelectric ceramics powder of a desired composition by causing a reaction of powders at a high temperature, and wet mixing is a wet process in a ball mill process to mix powders. .

Specifically, raw material powders including PbO, ZrO ₂ , TiO ₂ , ZnO, NiO, and Nb ₂ O ₅ are mixed, put into a jar, and wet-mixed with zirconia balls and a solvent for 4 to 36 hours. The content of the mixed raw material powder is 0.1 to 1 mol of ZrO2, 0.1 to 1 mol of TiO2, 0.01 to 0.5 mol of NiO, and 0.01 to 0.5 mol of ZnO based on 1 mol of PbO. ) and 0.1 to 1 mole (mol) of Nb2O5.

As described above, the composition of the PZT-PZNN compound is optimally designed by controlling the mole fraction of the raw material powders, so that it has a high piezoelectric strain constant and a low permittivity.

In one embodiment, the purity of the raw material powder does not affect properties such as piezoelectric strain constant, permittivity, and sintering temperature, but a preferred purity is 98% or more.

In one embodiment, the solvent is not particularly limited as long as wet mixing is possible with the raw material powder, but preferably, at least one solvent selected from the group consisting of methanol, ethanol, isopropanol, and distilled water and 10 hours to 40 It may be wet mixing for a period of time.

In one embodiment, the first powder forming step 120 is a step of forming a first powder by drying and then calcining the mixture.

According to one embodiment, in the first powder forming step, a PZNN-PZT-based piezoelectric ceramics composition is prepared by first calcining all materials except Pb in the mixture, then mixing the calcined composition powder and Pb and performing secondary calcining. it may be

According to one embodiment, the primary calcination temperature is 1,000 ° C. or higher, for example, 1,000 ° C. to 1,100 ° C. temperature range, except for Pb, in the step of proceeding to synthesize the mixed powder, and synthesizing the powder in the second The calcination temperature may be performed in a temperature range of 700 °C to 760 °C by mixing with Pb.

In one embodiment, the second powder forming step 130 is a step of forming a second powder by adding a low-temperature sintering additive to the first powder, wet mixing, and then drying.

In one embodiment, the low-temperature sintering additive may include at least one selected from the group consisting of lithium carbonate (Li ₂ CO ₃ ), boron carbonate (B ₂ CO ₃ ), and cadmium carbonate (CdCO ₃ ). there is.

Preferably, the low-temperature sintering additive may be lithium carbonate (Li ₂ CO ₃ ).

Accordingly, the piezoelectric ceramics sintered body produced by the method for producing a piezoelectric ceramics sintered body of the present invention is preferably xPb((Zn _0.8 Ni _0.2 ) _1/3 Nb _2/3 )O ₃ -(1-x)Pb (Zr _0.5 Ti _0.5 )O ₃ + Y wt% Li ₂ CO ₃ (0.10<x<0.30, 0.01<Y<0.5).

In one embodiment, the low-temperature sintering additive may be added in a range of 0.01 wt% to 0.5 wt% based on the total weight of the piezoelectric ceramics sintered body. Preferably, it may be in the range of 0.1% by weight to 0.3% by weight. If the low-temperature sintering additive is less than 0.01% by weight relative to the total weight of the piezoelectric ceramics sintered body, the effect of densifying the surface of ceramic particles cannot be exhibited when sintered at a low temperature. Grain boundary segregation within the crystal may hinder grain growth and degrade the piezoelectric properties of the material.

In one embodiment, the process of wet-mixing and drying the second powder may be repeatedly performed 1 to 6 times so that the low-temperature sintering additive is well mixed with the first powder and the size of the powder may be minimized.

In one embodiment, the forming of the piezoelectric body 140 is a step of forming a piezoelectric body by molding and then sintering the second powder.

In one embodiment, after pressing and molding the second powder into a desired shape, the sintering is performed at 850 °C to 900 °C; 860 °C to 900 °C; 3 hours to 10 hours at a temperature of 870° C. to 900° C. or 890° C. to 900° C.; 3 to 8 hours; or 3 hours to 5 hours; may be performed during Preferably, it may be performed at a temperature of 850 ℃ to 900 ℃ for 3 hours to 5 hours.

Low-temperature sintering is carried out at a temperature of 900 ° C. or less to prevent compositional change or structural deformation due to volatilization of PbO in the sintering step after molding the synthesized powder.

According to an embodiment, when the sintering temperature is less than 850 ° C., crystallization of the piezoelectric material may not occur, and when the sintering temperature is higher than 900 ° C., a change in composition due to volatilization of Pb may occur, resulting in degradation of properties of the piezoelectric material.

The piezoelectric ceramics sintered body produced by the manufacturing method of the piezoelectric ceramics sintered body of the present invention consists of (Pb, Zn, Ni, Nb)-(Pb, Zr, Ti) phases, and low-temperature sintering additives are added to the compound represented by PZNN-PZT. xPb((Zn _0.8 Ni _0.2 ) _1/3 Nb _2/3 )O ₃ -(1-x)Pb(Zr _0.5 Ti _0.5 )O ₃ + Y wt% low temperature sintering additive (0.10<x<0.30, 0.01<Y<0.5) may have a composition formula.

By adding the low-temperature sintering additive according to an embodiment of the present invention, it is possible to sinter at a low temperature of 900 ° C or less, so that structural deformation does not occur when manufactured as a layered piezoelectric body, and there is no problem of characteristic degradation due to compositional change of the material due to volatilization of PbO. It is possible to implement an acoustic actuator device having constant and conversion efficiency.

A multilayer piezoelectric body according to another embodiment of the present invention includes a piezoelectric ceramics sintered body layer manufactured by the piezoelectric ceramics sintered body or the method of manufacturing the piezoelectric ceramics sintered body according to one embodiment of the present invention; and an electrode layer formed on at least one of upper and lower surfaces of the piezoelectric ceramics sintered body layer. it could be

In one embodiment, the piezoelectric ceramics sintered body layer includes 2 to 10 layers; 2nd to 8th floor; 2nd to 5th floor; 5 to 10 layers; layer 5 to layer 8; or 7 to 10 layers; it may be laminated. Preferably, it may be 5 to 8 layers.

In one embodiment, the thickness of one layer of the piezoelectric ceramics sintered body is 20 μm to 40 μm; 20 μm to 30 μm; or 30 μm to 40 μm; it may be one.

In one embodiment, the electrode layer may use a Cu electrode, an Ag electrode, or an Ag-Pd electrode.

A piezoelectric speaker according to another embodiment of the present invention includes a laminated piezoelectric body according to an embodiment of the present invention; a diaphragm layer formed under the multilayer piezoelectric body; and a frame surrounding upper and lower side surfaces of the diaphragm.

According to an embodiment, the piezoelectric speaker may include a multilayer piezoelectric body, a diaphragm layer formed under the multilayer piezoelectric body to transmit vibrations, and a frame surrounding a side surface of the diaphragm.

According to one embodiment, the diaphragm layer may have a rectangular shape and include at least one flexible film having excellent elasticity.

According to one embodiment, the frame has an interior space open up and down, is coupled to a side surface of the diaphragm, serves to fix it up and down, and may be formed of a metal material.

A method of manufacturing a piezoelectric speaker according to another embodiment of the present invention includes bonding two types of films having different vibration characteristics with an epoxy material; Soldering (soldering) to the layered piezoelectric electrode portion according to an embodiment of the present invention; attaching the soldered multilayer piezoelectric body and the laminated film of the two types; and wrapping and attaching the periphery of the two types of laminated films with a frame.

In the step of adhering two types of films having different vibration characteristics with an epoxy material, epoxy is applied to the lower side of the polyether ether ketone (PEEK) film using a bar coater, and silicone rubber is attached to combine them.

In the step of soldering to the multilayer piezoelectric electrode portion according to an embodiment, soldering is performed to the electrode portion on the upper portion of the multilayer piezoelectric body so that each electrode layer is connected.

In the step of attaching the soldered multilayer piezoelectric body and the two types of laminated films according to one embodiment, epoxy is applied to the lower side of the multilayer piezoelectric body and then attached to the upper side of the film in which PEEK/Silicone rubber is laminated.

According to an embodiment, the step of wrapping and attaching a frame around the two types of laminated films is to fix the diaphragm to which the piezoelectric body is attached by attaching a steel frame having the same thickness to the top and bottom of the diaphragm around the diaphragm with epoxy. to finally manufacture a piezoelectric speaker.

Hereinafter, the present invention will be described in more detail by examples.

However, the following examples are only for illustrating the present invention, and the content of the present invention is not limited to the following examples.

[Example]

Manufacture of piezoelectric ceramics sintered body

High-purity powder (>98%) from Kojundo Chemical Laboratory was used in the experiment. Piezoelectric materials were synthesized using a general solid-state reaction method using PbO, ZrO ₂ , TiO ₂ , ZnO, Nb ₂ O ₅ and NiO as starting materials. The powder is weighed according to various compositional ratios of xPb(Zn _0.8 Ni _0.2 ) _1/3 Nb _2/3 O ₃ - (1-x)Pb(Zr _0.5 Ti _0.5 )O ₃ (PZNN-PZT, x = 0.10-0.30) It became. To ensure uniform dispersion, the powder was mixed with zirconia balls in an ethanol solution for 24 hours and dried at 120 °C for more than 4 hours. The resulting powder was subsequently subjected to two-step calcination (the first calcination temperature was around 1,100 °C and the second calcination temperature was around 720 °C). The Li ₂ CO ₃ dopant was mixed for 24 hours with the powder prepared by varying the concentration from 0.1 wt.% to 0.4 wt.%. An appropriate amount of 10% by weight polyvinyl alcohol (PVA) aqueous solution as a binder was added to the raw material powder, and a pressure of about 10 MPa was applied to mold the powder into a Ψ 10 mm disk. Cold isostatic pressing was performed using a water pressure of 130 MPa to make the molded ceramic have a more dense structure. Sintering was carried out continuously in the temperature range of 850–950 °C for 4 hours.

Manufacture of piezoelectric laminates

A multilayer piezoelectric actuator for a piezoelectric speaker was manufactured as follows. PZNN-PZT powders prepared for the production of green sheets for multi-layer piezoelectric actuators were mixed with solvents including ethanol, methyl ethyl ketone and dispersants in a ball mill for 24 hours. Subsequently, a binder (polyvinyl butyral) was added and ball milling was repeated to produce a slurry, and finally a green sheet having a thickness of ~40 μm was obtained by tape casting. The electrode paste was prepared by mixing 80 wt.% Ag and 20 wt.% Pd paste with a small amount of PZNN-PZT powder, binder (ethyl cellulose) and plasticizer in a 3-roll mill. Holes for pattern printing were punched in the green sheet prepared in the previous step, and electrode patterns corresponding to each layer were formed through screen printing. After stacking a total of seven layers, they were integrated by stacking at room temperature under a pressure of 0.04 MPa. After the upper and lower electrodes of the laminated sheet were printed, the respective layers were connected by cutting each component and terminating the corner portion. Sintering was performed in a belt-type furnace with high-temperature co-fired ceramic sheets placed on the top and bottom of the sample to prevent bending; A constant load was applied to the top during sintering. The samples were continuously fired for about 15 minutes at a final sintering temperature of 875 °C to fabricate multilayer piezoelectric actuators.

piezoelectric speaker manufacturing

6 is a plan view of a piezoelectric speaker manufactured according to an embodiment of the present invention.

Referring to FIG. 6 , the piezoelectric speaker may include a multilayer piezoelectric body, a diaphragm layer formed below the multilayer piezoelectric body and transmitting vibration, and a high rigidity stainless steel frame surrounding a side surface of the diaphragm.

A 12 × 16 × 0.32 mm ³ multilayer piezoelectric actuator was used to fabricate a piezoelectric speaker including a diaphragm made of polyetheretherketone (PEEK) and a silicone rubber film with different physical properties and dimensions. A high-rigidity stainless steel frame that effectively absorbs the vibration of the piezoelectric diaphragm and does not cause unnecessary vibration is used as a frame, and epoxy is used as an adhesive between each material for stable bonding.

The acoustic characteristics of the piezoelectric speaker were investigated by attaching it to the center of a baffle plate in an anechoic chamber with a sound insulation performance of 30 dB(A) and an acoustic wedge that blocks external noise. The distance between the reference microphone and the speaker was fixed at 10 cm. Totalonic distortion (THD) properties and sound pressure level (SPL) output in the audible frequency range (250-20,000 Hz) were measured by an audio analyzer (FX-00, NTi, Schaan, LI, Liechtenstein).

2 is a graph showing XRD analysis results of PZNN-PZT sintered bodies according to PZNN content prepared according to an embodiment of the present invention.

Referring to FIG. 2, as a result of synthesizing the composition according to an embodiment of the present invention, it is confirmed that a stable perovskite phase is formed without generation of a secondary phase. In particular, when x is 0.20 to 0.25, it can be expected to exhibit excellent piezoelectric properties by showing a Morphotropic Phase Boundary (MPB) region in which a tetragonal phase and a rhombohedral phase are somewhat mixed.

3 is a SEM image of a PZNN-PZT sintered body according to a doping content of lithium carbonate (Li ₂ CO ₃ ) prepared according to an embodiment of the present invention.

Referring to FIG. 3, when the added amount of lithium carbonate (Li ₂ CO ₃ ) was 0.1 wt%, the average particle size increased from 1.18 μm to 1.47 μm. It is observed that the particle size decreases when added more than that, which is judged to be that lithium carbonate (Li ₂ CO ₃ ) is added above the solubility limit and interferes with particle growth due to grain boundary segregation.

4 shows the results of measuring the electrical characteristics of the PZNN-PZT sintered body according to the doping content of lithium carbonate (Li ₂ CO ₃ ) prepared according to an embodiment of the present invention.

Referring to FIG. 4, when the addition amount of lithium carbonate (Li ₂ CO ₃ ) is 0.1 wt%, the piezoelectric constant (d ₃₃ ), electromechanical coupling coefficient (k _p ), and piezoelectric voltage coefficient (g ₃₃ ) are each 500 pC/ Even when sintered at a low temperature of 875 ℃ with N, 0.63, 43 mV / N, it showed similar or superior values to those when sintered at 950 ℃.

The above results indicate that Li ₂ CO ₃ has a low melting point of 723° C. and induces the formation of a liquid phase during sintering to densify the surfaces of ceramic particles, thereby having excellent piezoelectric properties even at low temperatures.

5 is a SEM image of a fracture surface of a multilayer piezoelectric body manufactured according to an embodiment of the present invention.

Referring to FIG. 5, xPb((Zn _0.8 Ni _0.2 ) _1/3 Nb _2/3 )O ₃ -(1-x)Pb(Zr _0.5 Ti _0.5 ) to which 0.1 wt% of lithium carbonate (Li ₂ CO ₃ ) was added ) O ₃ (0.15<x<0.30) It was confirmed that the laminated piezoelectric body fabricated using the piezoelectric ceramic composition had relatively good sintering at a low temperature of 875 °C.

7 is a cross-sectional view of a piezoelectric speaker according to an acoustic diaphragm structure having different sizes manufactured according to an embodiment of the present invention, and FIG. 8 shows simulation analysis results of frequency response characteristics of the piezoelectric speaker of FIG. 7 .

Referring to FIG. 8, when silicone rubber having a size smaller than that of the PEEK film, which is the lower diaphragm layer of the laminated piezoelectric body, is attached to the center of the lower part of the PEEK film, the silicone rubber acts as a mass in the core part where vibration occurs, and the output sound pressure level (SPL) in the entire frequency range ) characteristics are relatively evenly improved, and it can be seen that the average output sound pressure result is about 101 dB.

As described above, according to an embodiment of the present invention, a laminated piezoelectric body can be manufactured from a PZNN-PZT-based piezoelectric ceramic composition capable of being sintered at a low temperature, and a piezoelectric speaker having improved acoustic characteristics including the same can be manufactured.

As described above, although the embodiments have been described with limited drawings, those skilled in the art can apply various technical modifications and variations based on the above. For example, the described techniques may be performed in an order different from the method described, and/or components of the described system, structure, device, circuit, etc. may be combined or combined in a different form than the method described, or other components may be used. Or even if it is replaced or substituted by equivalents, appropriate results can be achieved.

Therefore, other implementations, other embodiments, and equivalents of the claims are within the scope of the following claims.

Claims (15)

A low-temperature sintering additive is added to the PZNN-PZT ceramics composition of Formula 1 below,
Piezoelectric Ceramics Sintered Body:
[Formula 1]
xPb((Zn _0.8 Ni _0.2 ) _1/3 Nb _2/3 )O ₃ -(1-x)Pb(Zr _0.5 Ti _0.5 )O ₃ (PZNN-PZT)
(0.10<x<0.30).
According to claim 1,
Wherein x is 0.20 to 0.25,
Piezoelectric ceramics sintered body.
According to claim 1,
The low temperature sintering additive,
At least one selected from the group consisting of lithium carbonate (Li ₂ CO ₃ ), boron carbonate (B ₂ CO ₃ ) and cadmium carbonate (CdCO ₃ ),
Piezoelectric ceramics sintered body.
According to claim 1,
The low-temperature sintering additive is in the range of 0.01% to 0.5% by weight relative to the total weight of the piezoelectric ceramics sintered body,
Piezoelectric ceramics sintered body.
Preparing a mixture by putting raw material powders containing PbO, ZrO ₂ , TiO ₂ , ZnO, NiO, and Nb ₂ O ₅ into a solvent so as to have a compositional formula of Formula 1 below;
drying and then calcining the mixture to form a first powder;
forming a second powder by adding a low-temperature sintering additive to the first powder, wet mixing, and then drying; and
forming a piezoelectric body by molding and then sintering the second powder;
including,
Manufacturing method of piezoelectric ceramics sintered body:
[Formula 1]
xPb((Zn _0.8 Ni _0.2 ) _1/3 Nb _2/3 )O ₃ -(1-x)Pb(Zr _0.5 Ti _0.5 )O ₃
(0.10<x<0.30).
According to claim 5,
Wherein x is 0.20 to 0.25,
Manufacturing method of piezoelectric ceramics sintered body.
According to claim 5,
Preparing the mixture is wet mixing the raw material powder with at least one solvent selected from the group consisting of methanol, ethanol, isopropanol and distilled water for 10 hours to 40 hours,
Manufacturing method of piezoelectric ceramics sintered body.
According to claim 5,
The low temperature sintering additive,
At least one selected from the group consisting of lithium carbonate (Li ₂ CO ₃ ), boron carbonate (B ₂ CO ₃ ) and cadmium carbonate (CdCO ₃ ),
Manufacturing method of piezoelectric ceramics sintered body.
According to claim 5,
The low-temperature sintering additive is added in the range of 0.01% to 0.5% by weight relative to the total weight of the piezoelectric ceramics sintered body,
Manufacturing method of piezoelectric ceramics sintered body.
According to claim 5,
The sintering is carried out at a temperature of 850 ℃ to 900 ℃ for 3 hours to 10 hours,
Manufacturing method of piezoelectric ceramics sintered body.
A piezoelectric ceramics sintered body layer produced by the piezoelectric ceramics sintered body or the method of manufacturing a piezoelectric ceramics sintered body according to claim 1; and
an electrode layer formed on at least one of upper and lower surfaces of the piezoelectric ceramics sintered body layer;
including,
Layered piezoelectric.
According to claim 11,
The piezoelectric ceramics sintered body layer,
Laminated from 2 to 10 layers,
Layered piezoelectric.
According to claim 11,
The thickness of one layer of the piezoelectric ceramics sintered body is 20 μm to 40 μm,
Layered piezoelectric.
The laminated piezoelectric body of claim 11;
a diaphragm layer formed under the multilayer piezoelectric body; and
a frame surrounding upper and lower side surfaces of the diaphragm;
including,
piezoelectric speaker.
Adhering two types of films having different vibration characteristics with an epoxy material;
soldering to the layered piezoelectric electrode of claim 11;
attaching the soldered multilayer piezoelectric body and the laminated film of the two types; and
Wrapping and attaching the periphery of the two types of laminated films with a frame;
including,
A method for manufacturing a piezoelectric speaker.

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