KR101260675B1 - Method for preparation of piezoelectric element for low sintering and piezoelectric element using the same - Google Patents

Abstract

The present invention relates to a method for producing a low-temperature sintering piezoelectric material and a piezoelectric material using the same, and more particularly, has a composition formula of Pb (Zr, Ti) O ₃ -Pb (Ni, Nb) O ₃ (hereinafter, PZT-PNN). In the production of piezoelectric material, the excessive use of nickel oxide reduces the two-step calcination process to one step, and the oxide is added as a sintering aid and sintered at low temperature, thereby maximizing the electromechanical coupling coefficient and piezoelectric constant. The present invention relates to a piezoelectric method and a piezoelectric material using the same.

Description

Method for manufacturing low-temperature sintering piezoelectric material and piezoelectric material using the same {METHOD FOR PREPARATION OF PIEZOELECTRIC ELEMENT FOR LOW SINTERING AND PIEZOELECTRIC ELEMENT USING THE SAME}

The present invention relates to a method for producing a low-temperature sintering piezoelectric material and a piezoelectric material using the same, and more particularly, has a composition formula of Pb (Zr, Ti) O ₃ -Pb (Ni, Nb) O ₃ (hereinafter, PZT-PNN). In the production of piezoelectric material, the excessive use of nickel oxide reduces the two-step calcination process to one step, and the oxide is added as a sintering aid and sintered at low temperature, thereby maximizing the electromechanical coupling coefficient and piezoelectric constant. The present invention relates to a piezoelectric method and a piezoelectric material using the same.

PZT-based piezoelectric materials are piezoelectric transformers, ultrasonic vibrators, electromechanical ultrasonic transducers, ultrasonic motors and actuators, and filters with excellent piezoelectric and dielectric properties that are widely applied to ultrasonic equipment, imaging equipment, sound equipment, sensors, and communication equipment. And it is widely applied to the resonator and the like, and the trend of miniaturization and lightening of electronic products, many companies and research institutes are actively researching on it.

However, conventionally, when the PZT-based piezoelectric material is manufactured, the calcination step is performed twice according to a column bite method, and the reaction process is divided into two steps, so that the process is complicated and economically large.

In addition, based on the well-known Pb (Zr, Ti) O ₃ [PZT] in terms of piezoelectric composition, it employs a specific relaxer in PZT to improve piezoelectric properties and to achieve low temperature sintering using oxide-based additives. Technology and the like exist in the prior art, which is an active method while attracting attention as a research for suppressing the volatilization of PbO which is rapidly volatilized at a temperature of 1000 ° C. or higher as a problem about environmental pollution arises.

Therefore, conventional PZT series materials have a relatively high sintering temperature and are difficult to be applied to a lamination process using inexpensive internal electrodes, and when the sintering temperature is low, piezoelectric properties are severely low. Particularly, the calcination step is performed twice. There is a problem in that the reaction process is complicated and economically expensive. Therefore, there is a need for the development of a method for manufacturing a piezoelectric body by a new technology.

The technical problem to be achieved by the present invention is to sinter at low temperatures by adding an oxide as a sintering aid and to reduce the calcination step by one by controlling the amount of nickel oxide instead of performing the calcination step twice by the conventional column bite method. The purpose of this invention is to provide a PZT-based low-cost piezoelectric manufacturing method that is simple to reduce the time and cost, and is easy to manufacture in a general ceramic process (low temperature sintering), and does not deteriorate piezoelectric and dielectric properties. .

The present invention to solve the first technical problem,

1) preparing a mixture by wet mixing Pb ₂ O, ZrO ₂ , TiO ₂ , NiO and Nb ₂ O ₅ in a solvent;

2) calcining (calcination) the mixture to form a first powder;

3) adding an oxide to the first powder, wet mixing and drying to form a second powder; And

4) It provides a method for producing a low-temperature sintering piezoelectric material comprising the step of forming the piezoelectric by sintering the second powder for 1 hour to 10 hours at 700 to 1000 ℃ sintering after pressing.

The present invention to solve the second technical problem,

(1-y) Pb (Zr _{1 - x} Ti _x ) O ₃ -yPb (Ni _1/3 Nb _2/3 ) O ₃ + z mol% oxide (0 < A PZT-PNN piezoelectric body having a composition of x <0.7, 0.2 <y <0.4, and 1≤z≤10 is provided.

In order to solve the third technical problem,

0.65Pb (Zr _{1 - x} Ti _x ) O ₃ -0.35Pb (Ni _1/3 Nb _2/3 ) O ₃ + y mol% oxide (0 <x <0.7) prepared by the method of manufacturing a piezoelectric body according to the present invention A PZT-PNN piezoelectric body having a composition of 1 ≦ y ≦ 10) is provided.

In order to solve the fourth technical problem,

Provided is a stacked actuator including a piezoelectric body manufactured by the method of manufacturing a piezoelectric body according to the present invention.

<Definition of Terms>

The piezoelectric material refers to a material having a property of changing electrical energy and mechanical energy applied thereto, and the piezoelectric effect is an electromechanical coefficient (k _p) indicating an efficiency of converting mechanical energy into electrical energy. ) And its strain on the applied electrical energy, or d ₃₃ (piezoelectric charge constant), which is its charge accumulation on the applied mechanical energy. Therefore, the piezoelectric material having excellent electromechanical coupling coefficient and d ₃₃ can linearly change the electro-mechanical energy, thereby enabling accurate control of the mechanical conversion amount and conversely receiving external vibration signals as accurate linear electric signals. Can be. In addition, this conversion is due to the properties of the material itself, so the structure is simplified.

PZT-based piezoelectric material manufacturing method according to the present invention by adding an excessive amount of nickel oxide to reduce the two-step calcination process to a one-step calcination process to reduce time and cost, the process is simple, and by adding 0.1-10 mol% of oxide 700 Piezoelectric transformer, ultrasonic vibrator, electromechanical ultrasonic transducer, ultrasonic motor and actuator with high piezoelectric and dielectric properties due to no volatilization of PbO volatiles due to sintering at -1000 ° C and not sintering at high temperature. It has an effect that can be widely applied to filters, resonators, and the like.

In addition, the PZT-based piezoelectric material manufacturing method according to the present invention is added to the NiO in excess of the calcination process in one step calcination process and low-temperature sintering to produce a piezoelectric material, the piezoelectric material and the Ag electrode can be baked at the same time It has an effect that can be manufactured at low cost without the need to add other expensive additives upon firing.

Therefore, the PZT-based piezoelectric material manufacturing method according to the present invention has a great advantage that the piezoelectric material and the Ag electrode can be simultaneously fired, so that the process is simple and can be applied to an actual component that is laminated at a very low cost.

1 is a process chart showing a method for manufacturing a piezoelectric body according to the present invention.
Figure 2 is a graph showing the piezoelectric properties change according to the Zr / Ti ratio change when sintered at 1200 ℃ without adding CuO of the piezoelectric composition according to the present invention.
3 is a graph showing changes in piezoelectric properties of Examples 1 to 4 and Comparative Example 1. FIG.
4 is a graph showing changes in piezoelectric properties according to the heat treatment temperature of Example 3. FIG.
5 is a graph showing the degree of reactivity with the electrode of the piezoelectric body prepared according to the piezoelectric method according to the present invention.

In the present invention, in preparing a Pb (Zr, Ti) O ₃ -Pb (Ni, Nb) O ₃ (hereinafter, PZT-PNN) piezoelectric body, two steps of calcination are performed by controlling the content of nickel oxide. It was confirmed that it was sinterable at low temperature by adjusting to and adding an oxide as a sintering aid.

Method for producing a low-temperature sintering piezoelectric body according to the present invention

1) preparing a mixture by wet mixing Pb ₂ O, ZrO ₂ , TiO ₂ , NiO and Nb ₂ O ₅ in a solvent;

2) calcining (calcination) the mixture to form a first powder;

3) adding an oxide to the first powder, wet mixing and drying to form a second powder; And

4) after the press-molding of the second powder, and sintering at a sintering temperature of 700 to 1000 ℃ for 1 to 10 hours to form a piezoelectric body.

In the present invention, _{1) Pb 2 O, ZrO 2} , TiO 2, NiO , and Nb ₂ O ₅ content of ZrO ₂ 0.1-1 mol, TiO ₂ 0.1-1 with respect to 1 mol of Pb ₂ O in step mol, NiO 2-5 mol, Nb ₂ O ₅ It is preferable that 0.1-1 mol. Outside the above range, the reaction rate of PbO-Nb ₂ O ₅ is faster than the reaction rate of NiO-Nb ₂ O ₅ Pb ₂ Nb ₂ O Secondary phases of ₇ and NiO occur and are undesirable.

The NiO, if not added in excess, as the addition amount, the NiO-Nb ₂ O ₅ reaction speed of the more rapid than the rate of reaction of PbO-Nb ₂ O ₅ si-phase synthesis of pure _{PbNi 1/3 Nb 2/3} O 3 Without this, secondary phases of Pb ₂ Nb ₂ O ₇ and NiO are formed, and the reaction formula is as follows.

BPb₂Nb₂O₇ + CNiO : A,B,C는 상수 …… ① _{APbNi 1/3 Nb 2/3} O 3

BPb ₂ Nb ₂ O ₇ + CNiO: A, B, and C are constants. ... ①

At this time, since the reaction proceeds to the right most, the above-mentioned secondary phase is generated. In order to solve the above method, the column bite method was conventionally used. In this method, Ni ₂ Nb ₂ O _7, which has a slow reaction rate, is first synthesized and then resynthesized with other starting materials to give a uniform 0.65Pb. a _{(Zr 0 .42 Ti 0 .58)} O 3 -0.35Pb (Ni 1/3 Nb 2/3) obtaining the O _3, the process sequence is as follows.

Ni ₂ Nb ₂ O ₇ 1 primary synthesis _{=> PbO, Ni 2 Nb 2} O 7, Nb 2 O 5, ZrO 2, the basis weight of the TiO ₂ => ₂ primary synthesis

However, in the column bite method, the reaction process is divided into two stages, which complicates the process.

Therefore, the present invention synthesizes in a single process without using the column byte method as described above. In this case, the secondary phase disappears and the PbNi _1/3 Nb _2/3 O ₃ phase desired in the present invention can be obtained. Therefore , the present invention is very preferred in that the addition of the NiO in an excessive amount to reduce the conventional calcination step divided into two steps to improve the desired effect of the present invention.

In the step 1), the purity of the raw powder of Pb ₂ O, ZrO ₂ , TiO ₂ , NiO and Nb ₂ O ₅ is preferably at least 98.0%, the Pb ₂ O, ZrO ₂ , TiO ₂ , NiO and Nb ₂ O ₅ raw powder can be placed in a jar and wet mixed for 15-50 hours. In the present invention, the piezoelectric material having excellent physical properties can be manufactured by optimally designing the composition of PZT-PNN.

In the wet mixing, the raw material powder may be ground / mixed using a zirconia ball and a volatile solvent to prepare a mixture. Here, the volatile solvent is not limited in kind, for example, an alcohol solvent may be used, and distilled water may also be used.

In the present invention, in step 2), in order to carry out a drying process for volatilizing the volatile solvent used in step 1), it is preferable to calcinate the mixture at 700-1000 ° C. for 1 to 5 hours. If it is lower than the temperature, the supplied thermal energy is insufficient and uniform phase synthesis does not occur, and if it exceeds 1000 ° C, uniform phase synthesis does not occur due to volatilization of PbO, which is not preferable.

The composition formula of the piezoelectric body formed in step 2) is (1-y) Pb (Zr _{1 - x} Ti _x ) O ₃ -yPb (Ni _1/3 Nb _2/3 ) O ₃ (0 <x <0.7, 0.2 <y <0.4), preferably 0.65Pb (Zr _{1- x} Ti _x ) O ₃ -0.35Pb (Ni _1/3 Nb _2/3 ) O ₃ (0 <x <0.7).

In the present invention, in step 3), an oxide may be added to the first powder and wet mixed and dried for 15-50 hours using a volatile solvent, and the volatile solvent may be an alcohol solvent or distilled water. By performing the wet mixing again, the mixing of the mixed powder and the shape of the powder can be minimized.

The oxide may be selected from CuO, ZnO and MnO ₂ , and the oxide is preferably contained 0.1-10 mol%, which is not preferable because it does not improve the dielectric and piezoelectric properties outside the above range and must be reacted at high temperature. .

It is found that the dielectric and piezoelectric properties are changed by the amount of the oxide added. Accordingly, by adding an appropriate amount of the oxide, PZT-PNN piezoelectric materials having various physical properties can be improved. Among the oxides, in particular, CuO, when dissolved to 0.1-10 mol%, acts as a sintering aid, thereby increasing dielectric and piezoelectric properties with increasing density.

In the present invention, in step 4), the second powder is sintered at 700-1000 ° C. for 1 hour to 10 hours to form a piezoelectric body having a high piezoelectricity, high dielectric constant, low electric field, and small mechanical quality factor (Q _m ). can do.

The PZT-PNN piezoelectric body prepared by the method of manufacturing the piezoelectric body according to the present invention is (1-y) Pb (Zr _1-x Ti _x ) O ₃ -yPb (Ni _1/3 Nb _2/3 ) O ₃ + z mol It is characterized by having a composition of% oxide (0 <x <0.7, 0.2 <y <0.4, 1≤z≤10).

PZT-PNN piezoelectric material prepared by the method of manufacturing a piezoelectric body according to the present invention is 0.65Pb (Zr _1-x Ti _x ) O ₃ -0.35Pb (Ni _1/3 Nb _2/3 ) O ₃ + y mol% oxide ( It has a composition of 0 <x <0.7, 1 <= y <= 10).

The following presents a preferred embodiment to aid the understanding of the present invention. The following examples are provided only to more easily understand the present invention, and the present invention is not limited to the following examples.

Example  And Comparative example

Example  One

Pb ₂ O (223.2 g), ZrO ₂ (40.1 g), TiO ₂ (26.0 g), NiO (9.6 g) and Nb ₂ O ₅ (31.0 g) with a purity of 98% or higher purity Wet mixed together using ethanol for 24 hours. The wet-pulverized mixture was dried and calcined at 850 ° C. for 3 hours to synthesize a phase having a composition of 0.65PZ _{1 - x} T _x -0.35PNN to prepare a first powder. After the addition of 1, 2, 3, 4 and 5 mol% of CuO to the first powder, the mixture was wet mixed with alcohol for 48 hours and dried to prepare a second powder. The second powder was press molded into a cylindrical shaped body having a diameter of 16 mm and a height of 1.2 mm. Then, the molded second powder was sintered at 850 ° C. for 4 hours. The second powder was molded and sintered to form piezoelectric bodies according to the present invention, respectively.

After polishing the sample subjected to the sintering process and applying the electrode material, the piezoelectric property was measured 24 hours after providing a 4 kV / mm DC bias at 120 ° C. in silicon oil for 1 hour and measuring the characteristics of the piezoelectric body. Shown in

Example  2

A molded second powder was prepared in the same manner as in Example 1 except that the molded second powder was sintered at 875 ° C. for 4 hours, and the properties of the manufactured piezoelectric body were measured and the results are shown in FIG. 3.

Example  3

A molded second powder was prepared in the same manner as in Example 1 except that the second powder was sintered at 900 ° C. for 4 hours, and the properties of the manufactured piezoelectric body were measured and the results are shown in FIGS. 3 and 4.

Example  4

A molded second powder was prepared in the same manner as in Example 1 except that the molded second powder was sintered at 950 ° C. for 4 hours, and the properties of the manufactured piezoelectric body were measured and the results are shown in FIG. 3.

Comparative example  One

A molded second powder was prepared in the same manner as in Example 1 except that the molded second powder was sintered at 650 ° C. for 4 hours, and the properties of the manufactured piezoelectric body were measured and the results are shown in FIG. 3.

Comparative example  2

Except that the addition of 8.7 g of NiO was prepared in the same manner as in Example 1, and as a result, Comparative Example 2 confirmed that the secondary phase of Pb ₂ Nb ₂ O ₇ and NiO occurred unlike the piezoelectric material prepared in Example 1.

Composition analysis

In order to observe the piezoelectric properties that are changed according to the change of the piezoelectric composition by changing the piezoelectric composition by changing the amount of Z (Zr / Ti ratio change) of x of 0.65PZ _{1 - x} T _x -0.35PNN without CuO Compositional analysis was performed.

FIG. 2 is a diagram showing a change in piezoelectric properties according to the Zr / Ti ratio change in the case of sintering at 1200 ° C without adding CuO in the method of manufacturing a piezoelectric body.

Referring to Figure 2, unlike the piezoelectric material manufacturing method according to the present invention is a diagram showing the relative density according to the amount of Zr / Ti ratio change when sintered at 1200 ℃ without adding CuO, all regardless of the Zr / Ti ratio High values of 95% or higher.

The relative density may be used as a measure for determining whether the specimen is sintered, and when sintered at 1200 ° C., all of them may be judged to be well sintered regardless of the Zr / Ti ratio. Therefore, it can be seen that the change in piezoelectric properties generated by the change in Zr / Ti ratio is not due to the change in the degree of sintering but due to the change in structure.

2 shows the piezoelectric charge constant (d ₃₃ ), k _p , relative permittivity, dielectric loss, and Q _m when the piezoelectric body according to the present invention is sintered at 1200 ° C. without adding CuO.

All values except for Q _m when the ratio of Ti 0.58 il are exhibited up to Q _m exhibited a minimum. In general, the change of the structure from rhombohedral to tetragonal with the change of Zr / Ti ratio. Therefore, in the case of Ti ratio of about 0.58, it can be seen that phase coexistence of tetragonal and tetragonal crystals occurred, and accordingly, piezoelectric properties were improved. However, when sintered at a temperature of 1200 ℃, it was confirmed that the PbO is rapidly volatilized.

3 is a graph showing changes in piezoelectric properties according to CuO addition amounts and sintering temperatures of Examples 1 to 4 and Comparative Example 1. FIG.

Referring to FIG. 3, in the case of the specimen sintered at 650 ° C. (Comparative Example 1), the relative density was very low due to the lack of sintering temperature, and it was confirmed that the piezoelectric and dielectric properties were very low. However, in the case of specimens sintered at 850 ° C. or more (Examples 1 to 4), as the relative density increases as CuO is added, if more than 1 mol% of CuO is added, all the specimens have a relative density of about 98% or more. This may be due to the liquid phase sintering caused by the addition of CuO and densification of the specimen.

It can be seen that the piezoelectric properties shown in FIG. 3 are very low in the case of the specimen sintered at 650 ° C. (Comparative Example 1), which is due to the low sintering degree at the above temperature. At higher sintering temperatures, it can be seen that the piezoelectric properties increase with the addition of CuO up to about 1 mol% and saturate thereafter. This is due to the increase in sintering degree and the microstructure with increased particle size. Thus, referring to FIG. 3, the specimens with more than 1 mol% CuO added high piezoelectric properties of d ₃₃ = 620 pC / N, k _p = 0.64, and relative permittivity = 3750 even at low temperature sintering at 900 ° C (Example 3). In addition, when CuO was added, the piezoelectric constant, the electromechanical coupling coefficient, and the dielectric constant were high even at low sintering temperature of 1000 ° C. or less.

In the piezoelectric properties, the PNN-based piezoelectric ceramics manufactured by a general sintering method without using a specific additive previously can be sintered at a high sintering temperature of about 1200 ° C, but at this temperature, the composition is uneven due to volatilization of PbO. This appears and has a lot of difficulty of reproduction. In addition, there are environmental issues in the process due to volatilization. In addition, the high sintering temperature makes it difficult to apply to the lamination process. The piezoelectric composition (Example 3) prepared according to the method of manufacturing a piezoelectric body according to the present invention can be sintered at a low temperature of 900 ° C., and the piezoelectric constant is about 620 pC / N even in low temperature sintered specimens, and thus no deterioration in characteristics is observed. It can be seen. In general, when the piezoelectric composition having a sintering temperature of 900 ° C. or less is manufactured in a multi-layer, the piezoelectric body according to the present invention has various application possibilities in actual piezoelectric devices because the Ag electrode can be used and the stability of the structure during lamination.

4 is a graph showing changes in piezoelectric properties according to the post-heat treatment temperature of Example 3. FIG.

4, the composition best piezoelectric properties represented by a 0.65PZ _{0 .42} T _{0 .58} sintered at 900 ℃ -0.35PNN + x mol% of CuO composition (x is 1 to 5) (Example 3) In the case of 200 ℃ it can be seen that maintains a high value of d33 = 500 pC / N. This is because the phase transition temperature is about 200 ° C. in the cubic crystal of the present composition. In other words, it is expected that the present composition can be used without a significant change in the piezoelectric properties even in the temperature range up to 200 ° C.

In general, in the lamination process and the device fabrication process, the process temperature rises to about 160 ° C., so evaluation of the property change at 200 ° C. or less is essential. In the present invention, by reducing the content of PNN, the existing low phase transition temperature was raised to stabilize the property change.

5 shows the degree of reactivity with the electrode of the piezoelectric body produced by the method of manufacturing a piezoelectric body according to the present invention.

Referring to the XRD pattern with the electrode of FIG. 5, no secondary phase was found other than the peak judged by the electrode and the ceramic. From this, it can be seen that additional reaction does not occur between the ceramic and the electrode when co-fired with the Ag electrode at a temperature of 900 ℃. In the EDX line scan after co-firing, the interface between the electrode and the ceramic was neatly formed and there was no diffusion between the electrode element and the ceramic element. Therefore, it can be seen that the composition mentioned in the present invention can be sufficiently applied to the lamination process when the Ag electrode is used at 900 ° C.

As indicated above, the piezoelectric material manufacturing method according to the present invention is capable of sintering at a low temperature of 700-1000 ° C. by reducing the two-stage calcination process to one step by using an excessive amount of NiO and adding an oxide. By doing so, it was confirmed that the volatile material of the PbO was not volatilized without sintering even at low temperature without the appearance of a secondary phase.

In addition, the piezoelectric material manufactured according to the piezoelectric material manufacturing method according to the present invention was confirmed that it is sufficiently applicable to the lamination process when the Ag electrode was used at 900 ° C., and thus the piezoelectric transformer having high piezoelectricity and high dielectric constant had excellent piezoelectric and dielectric properties. It has been found to be applicable to ultrasonic vibrators, electromechanical ultrasonic transducers, ultrasonic motors and actuators, filters and resonators.

Therefore, it was confirmed that the piezoelectric bodies obtained from Examples 1 to 4 had much better piezoelectric and dielectric properties than the piezoelectric bodies obtained from Comparative Examples 1 and 2.

Advantages and features of the present invention, and methods of achieving the same will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the embodiments are to make the disclosure of the present invention complete, and the general knowledge in the technical field to which the present invention belongs. It is provided to fully convey the scope of the invention to those skilled in the art, and the present invention is defined only by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

Claims (7)

1) preparing a mixture by wet mixing PbO, ZrO ₂ , TiO ₂ , NiO and Nb ₂ O ₅ in a solvent;
2) calcining (calcination) the mixture to form a first powder;
3) adding an oxide to the first powder, wet mixing and drying to form a second powder; And
4) forming the piezoelectric body by sintering the second powder for 1 hour to 10 hours at a sintering temperature of 700 to 1000 ° C. after pressure molding;
In step _{1) PbO, ZrO 2, TiO} 2, NiO , and Nb ₂ O ₅ content of the ZrO ₂ 0.1-1 mol with respect to 1 mol of PbO, TiO ₂ 0.1-1 mol, 2-5 mol NiO, Nb ₂ O ₅ 0.1-1 mole, the method for producing a low-temperature sintering piezoelectric material. delete The method according to claim 1, wherein in step 1), the PbO, ZrO ₂ , TiO ₂ , NiO and Nb ₂ O ₅ raw powders are placed in a jar and wet mixed for 15-50 hours, and the solvent is an alcohol solvent or A method for producing a low-temperature sintering piezoelectric body, which is distilled water. The method of claim 1, wherein in the step 2), the mixture is calcined at 700-1000 ° C. for 1 hour to 5 hours. The method of claim 1, wherein in step 3), an oxide is added to the first powder and wet mixed and dried for 15-50 hours using a volatile solvent, and the oxide is selected from CuO, ZnO, and MnO ₂ , The oxide is a method for producing a low-temperature sintering piezoelectric material, characterized in that it contains 0.1-10 mol%. delete delete

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