KR101090862B1 - Piezoelectric ceramics, manufacturing method thereof and ultrasonic nozzle using the same - Google Patents

Abstract

The invention _{0.02 Pb (Mn 1/3 Nb} 2/3) , the piezoelectric characteristic is improved while possible low-temperature co-fired with a high electromechanical coupling factor and the mechanical quality factor as a laminated piezoelectric actuator-type piezoelectric ceramic composition for an ultrasonic nozzle (Ni _{1 / 3 Nb 2/3) 0.12} (Zr 0 .50 Ti 0 .50) 0.86 O 3 + xMnO 2 + 0.2wt% Fe 2 O 3 + 0.2wt% CuO + 0.15wt% Nb 2 O 5 + 0.25wt% CeO 2 ( At this time, the piezoelectric ceramic composition containing the composition of 0 <x <= 3) was developed. In addition, Na ₂ CO ₃ and Li ₂ CO ₃ may be added to the composition as a sintering aid. The sintering temperature of the composition is in the range of 850 to 900 ℃.

Multilayer Piezo Actuator, Ultrasonic Nozzle, Piezoelectric Element, Low Temperature Sintering

Description

Piezoelectric Ceramics Composition, Method of Manufacturing the Same, and Ultrasonic Nozzle Apparatus Thereby {PIEZOELECTRIC CERAMICS, MANUFACTURING METHOD THEREOF AND ULTRASONIC NOZZLE USING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to piezoelectric ceramic compositions, and more particularly, to piezoelectric ceramic compositions capable of low-temperature sintering for multilayer piezoelectric actuator ultrasonic nozzles and methods for their preparation.

The present invention also relates to an ultrasonic nozzle device using the piezoelectric ceramic composition.

Recently, in order to atomize liquid fuel, a method of high pressure injection of liquid fuel into a thin hole of a tip using a high pressure pump is generally used. However, in the case of using such a high-pressure injection method, the surface area of the injected fuel particle diameters are nonuniform, resulting in incomplete combustion, and thus, there is a problem in that pollution generation and energy efficiency decrease.

However, as a method developed to solve this problem, the method of spraying liquid fuel using ultrasonic waves has excellent uniform particle size and atomization, so it is not only energy saving and pollution prevention, but also at low flow rate and low supply flow rate. It can be applied to various industries such as pharmaceutical application process and semiconductor manufacturing process. However, in order to improve the spray efficiency of the liquid fuel using ultrasonic vibration, it is important to improve the characteristics of the actuator as well as the mechanical mechanism of the nozzle.

In particular, the stacked piezoelectric actuator-type ultrasonic nozzle having excellent spraying efficiency due to the structure in which the piezoelectric elements are stacked is a technology for designing a small internal impedance for high power as compared to conventional ultrasonic nozzles. In addition, since the properties of the stacked piezoelectric elements influence the characteristics of the ultrasonic nozzle, control of the physical properties of the ceramics for piezoelectric actuators forming the piezoelectric elements is a key factor.

That is, such piezoelectric actuator ceramics must have a large electromechanical coupling coefficient (k _p ) for high energy conversion efficiency, and a large mechanical quality coefficient (Q _m ) to suppress temperature rise due to heat generation. In addition, the input voltage of the piezoelectric ceramics should be lowered to obtain high output characteristics.

However, when the sintering temperature of the multilayer piezoelectric ceramics is high, since the internal electrodes between the laminated structure layers are co-sintered with the ceramics, expensive Pd or Pt is contained instead of Ag electrodes having a melting point of about 960 ° C. Since Ag / Pd and Ag / Pt electrodes have to be used, manufacturing costs are high. Therefore, there is a demand for development of piezoelectric ceramics that can be sintered at a low temperature of 900 ° C or lower in order to use a low melting point Ag electrode.

Accordingly, the present invention was devised to solve the above problems, and an object of the present invention is to provide a piezoelectric ceramic composition and a method of manufacturing the same, which are excellent for piezoelectric actuator-type ultrasonic nozzles exhibiting excellent piezoelectric and dielectric properties.

In one aspect of the present invention for achieving the same object, the piezoelectric ceramic composition according to an aspect of the present invention, _{Pb (Mn 1/3 Nb 2} /3) 0.02 (Ni 1/3 Nb 2/3) 0.12 (Zr 0 Ti _{0 .50 .50) 0.86} O ₃ + 0.2wt% xMnO ₂ + Fe ₂ O ₃ + 0.2wt% + CuO composition of _{0.15wt% Nb 2 O 5 + 0.25wt} % CeO 2 ( wherein, 0 <x≤3 a) It may include.

In addition, in the piezoelectric ceramic composition according to another aspect of the present invention, Na ₂ CO ₃ and Li ₂ CO ₃ may be added to the composition.

In addition, the method of manufacturing a piezoelectric ceramic composition according to another aspect of the present invention is Pb (Mn _1/3 Nb _2/3 ) _0.02 (Ni _1/3 Nb _2/3 ) _0.12 (Zr _0.50 Ti _0.50 ) _0.86 O ₃ + xMnO ₂ +0.2 wt% Fe ₂ O ₃ +0.2 wt% CuO + 0.15 wt% Nb ₂ O ₅ +0.25 wt% CeO ₂ (At this time, a sample of 0 <x≤3) is weighed, mixed, pulverized, dried and calcined, and Na ₂ CO ₃ and Li ₂ CO ₃ are respectively added to the calcined sample and mixed and ground again. After the drying, and forming the dried sample and sintering it may be included. At this time, the sintering temperature may be in the range of 850 to 900 ℃.

As described above, in the present invention, a piezoelectric ceramic composition for a laminated piezoelectric actuator type ultrasonic nozzle having a high electromechanical coupling coefficient and a mechanical quality coefficient due to low-temperature firing and improved piezoelectric characteristics has been developed. The piezoelectric ceramic composition shows excellent spraying characteristics without excessive heat generation when used in a stacked piezoelectric actuator type ultrasonic nozzle, and can be utilized not only in a laminated device to such an ultrasonic nozzle but also in a device field requiring low temperature firing.

Hereinafter, the present invention will be described in detail.

The piezoelectric ceramic composition according to one embodiment of the present invention is based on the composition of Formula 1 below:

_{Pb (Mn 1/3 Nb 2} /3) 0.02 (Ni 1/3 Nb 2/3) 0.12 (Zr 0 .50 Ti 0 .50) 0.86 O 3 ( Formula 1)

In addition, in the present embodiment, MnO _{2 in the} range of greater than 0wt% for improving the piezoelectric constant, the electromechanical coupling coefficient, and the mechanical quality coefficient in the composition of Equation 1 and 3wt% or less, 0.2wt% Fe for improving the mechanical quality coefficient ₂ O ₃ , 0.2wt% CuO to improve piezoelectric and electromechanical coupling coefficients and mechanical quality coefficients, 0.15wt% Nb ₂ O ₅ to improve piezoelectric constants, and to improve piezoelectric and electromechanical coupling coefficients Each containing 0.25 wt% CeO ₂ . In addition, in one embodiment of the present invention, it is preferable that 0.2 wt% Na ₂ CO ₃ +0.2 wt% Li ₂ CO ₃ is added to this composition as a sintering aid. In addition, in one embodiment of the present invention, the sintering temperature of the composition may be a low temperature of 850-900 ℃.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings. However, the embodiments described below are provided to assist the overall understanding of the present invention, and the present invention is not limited to the above embodiments.

Example  One ( Stacked  Piezoelectric Of actuator  Produce)

In this example, a piezoelectric vibrator having the composition of Formula 2 was prepared by a general oxide mixing method:

Pb (Mn_{One / 3}Nb_{2 / 3})_0.02(Ni_{One / 3}Nb_{2 / 3})_0.12(Zr_{0 .50}Ti_{0 .50})_0.86O₃+ XMnO₂+ 0.2wt% Fe₂O₃+ 0.2wt% CuO + 0.15wt% Nb₂O₅+ 0.25wt% CeO₂ (Equation 2)

(At this time, 0wt% <x≤3wt%)

First, the composition of Formula 2 was weighted up to 10 ^-4 g with a powder having a purity of 99% or more, and ball milling for 24 hours using zirconia balls with added acetone as a dispersion medium. The ball mill powder was dried in a thermostat for at least 12 hours and then calcined at 850 ° C. for 2 hours. 0.2 wt% Na ₂ CO ₃ + 0.2wt% Li ₂ CO ₃ was added to the calcined powder as a sintering aid, followed by remixing and grinding for 24 hours, followed by drying. The dry powder was mixed with PVB (Ferro B73305) at a ratio of 72:28, tape cast by a doctor blade method, and the sheet was removed at 75 μm. The sheets were stacked and uniaxially formed at a pressure of 3000 psi at 80 ° C., burned out at 340 ° C. for 3 hours, and sintered at 900 ° C. for 120 minutes. After sintering, the electrode was coated by grinding to a thickness of 3.5 mm and heat-treated at 650 ° C. for 10 minutes. The specimen in which the electrode was formed was polarized at 20 mA / cm in 120 degreeC silicone oil. After 24 hours, dielectric and piezoelectric properties were measured by the resonance and anti-resonance method, and the effective electromechanical coupling coefficient k _eff and mechanical quality factor Q _m of the piezoelectric vibrator were obtained by the following equation.

(식 3)

(Equation 3)

(식 4)

(Equation 4)

Where Z _m is the impedance of the resonant frequency, C ₀ is the capacitance of the specimen measured at 1 kHz after polarization, f _r is the resonant frequency, and f _a is the anti-resonant frequency.

1A shows the structure of the stacked piezoelectric actuator according to the present embodiment, and FIG. 1B shows the internal electrode structure of each of the stacked piezoelectric vibrators. That is, referring to FIG. 1A, in this embodiment, the size of the laminated piezoelectric actuator 1 is manufactured as 26.5 (outer diameter) × 12 (inner diameter) × 3.5 mm ³ , and the annular piezoelectric vibrator 4 having six layers. Was laminated. The electrodes 2 were applied to the upper and lower portions thereof, and internal electrodes 5 were formed on the surfaces of the piezoelectric vibrators 4 polarized in the polarization direction 3, respectively.

FIG. 2 shows an X-ray diffraction pattern according to the amount of MnO ₂ added (0, 0.1, 0.2 wt%) of each composition in the piezoelectric vibrator for the stacked piezoelectric actuator according to the present embodiment. The crystal structure of the specimen showed characteristic peaks of the tetragonal phase (002) and (200) between 42 ° and 47 °, and the secondary phase increased with increasing MnO ₂ content.

3A-3C are scanning electron microscope (SEM) photographs of microstructures according to the amount of MnO ₂ added in the piezoelectric vibrator for the laminated piezoelectric actuator according to the present embodiment, and FIG. 3A is 0wt% MnO ₂ , and FIG. 3B is 0.1. wt% MnO _2, Figure 3c shows a photograph of the composition of 0.2wt% MnO ₂ were added. Referring to FIG. 3, the MnO ₂ addition amount increased to 0.1 wt%, the particle size increased, and the addition amount decreased, and the addition amount of MnO ₂ was 0, 0.1, 0.2 wt%, respectively. The size was 2.49, 2.71, 2.48 mu m.

Table 1 below shows the piezoelectric characteristics of the piezoelectric vibrator for the stacked piezoelectric actuator according to the present embodiment.

TABLE 1

At this time, the density, dielectric constant (ε _r ), electromechanical coupling coefficient (k _p ), mechanical quality coefficient (Q _m ), and piezoelectric constant (d ₃₃ ) in specimens added with 0.1 wt% MnO ₂ at a sintering temperature of 900 ° C. The values of 7.883 g / cm ³ , 1269, 0.608, 1101, and 380 pC / N are suitable for application as a low temperature sintered stacked piezoelectric actuator type ultrasonic nozzle.

Figure 4 shows the impedance characteristics of the piezoelectric vibrator for the stacked piezoelectric actuator according to the present embodiment. The impedance characteristic of the piezoelectric vibrator is an important criterion for determining the driving frequency when driving the ultrasonic nozzle. The resonant and anti-resonant frequencies of the piezoelectric vibrators were 55.95 Hz-60.05 Hz, and the effective electromechanical coupling coefficient (k _eff ) was excellent at 0.363. Table 2 shows the piezoelectric properties and equivalent circuit constants of the stacked annular piezoelectric vibrators.

Table 2

Example  2 ( Stacked  Piezoelectric Actuator  Manufacture of ultrasonic nozzles)

In this embodiment, the ultrasonic nozzle device shown in Fig. 5 is constructed using the stacked piezoelectric actuator of Example 1. That is, two piezoelectric vibrators 15 and 16 are coupled to the body 11 of the nozzle, and the power frequency unit 17 is composed of a power amplifier (NF BA4825) and a function generator (NF WF1946B) connected thereto. , The driving voltage was driven to 37V. Then, the liquid was stored in the container 12, and the amount of liquid was sprayed at a constant amount of 2 L / h when the nozzle was driven. After the first drive for the first 30 minutes, with a rest of 10 minutes, the second drive for 30 minutes was measured again. In order to measure the electrical characteristics of the stacked piezoelectric actuator ultrasonic nozzle, the output voltage and output power according to the input voltage were measured using an oscilloscope (Tektronix TDS3054), and the temperature rise according to the output power was measured by a contact thermometer.

6 is a graph showing the change of the surface temperature value of the nozzle oscillator according to the driving time. After 10 minutes of driving the nozzle was continuously rising and after 10 minutes it was confirmed that the stabilization while maintaining a heat generation of about 26 ℃. In the second drive, the heat generation was about 26.5 ° C. after 10 minutes without significant change with the first drive, and the temperature was increased by about 6 ° C. when the drive was performed at room temperature (20 ° C.). Therefore, it is considered that there is no problem in the device even after driving for a long time.

 7 is a graph illustrating a change in driving current and driving power according to driving time. The driving current was continuously decreased until 10 minutes after the nozzle driving for both the first and second driving, and then stabilized at about 260 mA after 10 minutes. As can be seen from the exothermic result of FIG. In addition, the value of the driving power was also reduced to 10 minutes after the nozzle drive, and then stabilized to 8.1 W after 10 minutes. The reason why the secondary drive is lower than the primary drive is because the surface temperature of the piezoelectric vibrator is increased by the primary drive, which means that the current and power are reduced than the primary drive.

In the above-described embodiments of the present invention, the powder characteristics such as the average particle size, distribution and specific surface area of the composition powder, the purity of the raw material, the amount of impurity added and the sintering conditions may vary slightly within the usual error range. Is quite natural to those of ordinary skill in the art.

In addition, the preferred embodiment of the present invention is disclosed for the purpose of illustration, anyone of ordinary skill in the art will be possible to various modifications, changes, additions, etc. within the spirit and scope of the present invention, such modifications, changes, Additions and the like should be considered to be within the scope of the claims.

1A is a schematic structural diagram of a stacked piezoelectric actuator according to the present embodiment.

Figure 1b is a photograph of the internal electrode of each piezoelectric vibrator laminated.

Figure 2 is an X-ray diffraction pattern according to the amount of MnO ₂ addition (0, 0.1, 0.2 wt%) of each composition in the piezoelectric vibrator for a laminated piezoelectric actuator according to an embodiment of the present invention.

Figure 3a-3c is a scanning electron microscope (SEM) photograph of the microstructure according to the amount of MnO ₂ addition (0, 0.1, 0.2 wt%) in the piezoelectric vibrator for a stacked piezoelectric actuator according to an embodiment of the present invention.

Figure 4 is a graph of the impedance characteristics of the piezoelectric vibrator for the stacked piezoelectric actuator according to an embodiment of the present invention.

5 is a schematic structural diagram of an ultrasonic nozzle device using a piezoelectric vibrator for a stacked piezoelectric actuator according to an embodiment of the present invention.

6 is a graph showing the change of the surface temperature value of the nozzle oscillator according to the driving time in the ultrasonic nozzle device using the piezoelectric vibrator for the stacked piezoelectric actuator according to an embodiment of the present invention.

7 is a graph showing a change in driving current and driving power according to driving time in an ultrasonic nozzle device using a piezoelectric vibrator for a stacked piezoelectric actuator according to an embodiment of the present invention.

Claims (5)

Piezoelectric ceramic composition comprising a composition represented by the following formula; _{Pb (Mn 1/3 Nb 2} /3) 0.02 (Ni 1/3 Nb 2/3) 0.12 (Zr 0 .50 Ti 0 .50) 0.86 O 3 + xMnO 2 + 0.2wt% Fe 2 O 3 + 0.2wt% CuO + 0.15wt% Nb ₂ O ₅ + 0.25wt% CeO ₂ (where 0 <x≤3) The method of claim 1, Na ₂ CO ₃ in the composition And Li ₂ CO ₃ are added, respectively. _{Pb (Mn 1/3 Nb 2} /3) 0.02 (Ni 1/3 Nb 2/3) 0.12 (Zr 0 .50 Ti 0 .50) 0.86 O 3 + xMnO 2 + 0.2wt% Fe 2 O 3 + 0.2wt% CuO + 0.15wt% Nb ₂ O ₅ + 0.25wt% CeO ₂ (At this time, weighing a sample of 0 <x≤3), mixing, pulverizing, drying and calcining; Adding Na ₂ CO ₃ and Li ₂ CO ₃ to the calcined sample and mixing, pulverizing, and drying them, respectively; Forming the dried sample and sintering the method for producing a piezoelectric ceramic composition, characterized in that it comprises. The method of claim 3, The sintering temperature is a manufacturing method of the piezoelectric ceramic composition, characterized in that 850 to 900 ℃. An ultrasonic nozzle device comprising at least one piezoelectric element comprising a piezoelectric ceramic composition having a composition according to claim 1.

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