KR101239275B1 - Low temperature sintering piezoelectric ceramic composition, manufacturing method thereof, and piezoelectric ceramic device using the same ceramic composition - Google Patents

Abstract

The present invention relates to a piezoelectric composition having an excellent piezoelectric constant and an electromechanical coupling coefficient, having a high Curie temperature, and capable of low temperature sintering, a method for manufacturing the same, and a piezoelectric element using the same, wherein the piezoelectric composition of the present invention is (1-xy) Pb (Zr _{1 - z} Ti _z ) O ₃ -xPb (Ni _1/3 Nb _2/3 ) O ₃ -yPb (Zn _1/3 Nb _2/3 ) O ₃ [(1-xy) PZ _{1 - z} T _z -xPNN-yPZN], x + y is 0.3≤x + y≤0.55, and z is 0.50≤z≤0.65. Method for producing a piezoelectric composition, (a) PbO, ZrO ₂ , TiO ₂ , NiO, ZnO, Nb ₂ O ₅ powder having a purity of 99% or more according to the composition, and (b) step (a) Further weighing ZnO and NiO by the weight amount of w mol% (0 <w ≦ 10) in (c) and wet mixing the powder weighted through the steps (a) and (b). Pulverizing and calcining, (d) wet mixing the calcined powder passed through step (c) with an alcohol solvent and drying, and (e) molding and sintering the dry powder subjected to step (d). Include.

Description

Low temperature sintering piezoelectric composition, method for manufacturing same, and piezoelectric element using the same {Low temperature sintering piezoelectric ceramic composition, manufacturing method etc, and piezoelectric ceramic device using the same ceramic composition}

The present invention relates to a piezoelectric composition for low temperature sintering, a method for manufacturing the same, and a piezoelectric element using the same. More specifically, the piezoelectric composition having a high Curie temperature with excellent piezoelectric constant and electromechanical coupling coefficient and capable of low temperature sintering, and It relates to a manufacturing method and a piezoelectric element using the same.

Lead zirconate titanate (PZT) -based piezoelectric ceramics are representative piezoelectric ceramics and are used in many piezoelectric devices such as micro actuators, energy harvesters, and piezoelectric generators.

However, conventionally studied PZT-based piezoelectric ceramics generate secondary phases such as Pb ₃ Nb ₄ O ₁₃ [PN] or PbNb ₂ O ₆ during ceramic phase synthesis, and most of them use a double phase synthesis method such as column bite method to remove them. The process was complicated.

In addition, when PNN is employed in PZT ceramics to improve the piezoelectric properties, expensive internal electrodes are used in the lamination process such as a multilayer actuator because a high sintering temperature of 1200 ° C. or more is required despite the excellent piezoelectric properties. There was a problem that should be. In order to lower the high sintering temperature of PZT, research results have been reported for the low temperature sintering by adding oxides such as CdO, ZnO and CuO as low temperature sintering aids, but it has lower piezoelectric properties than piezoelectric ceramics sintered at 1200 ℃. Came.

In the case of the PZT ceramic PNN it is employed, since the low Curie temperature of most PNN (T _c = -20 ℃), according with the temperature (T _c) of a low Curie below 200 ℃ many restrictions on its use and process There was this.

The present invention has been made in the technical background as described above, and an object thereof is to provide a piezoelectric composition capable of low-temperature sintering and having excellent piezoelectric constants and electromechanical coupling coefficients.

Another object of the present invention is to provide a piezoelectric composition having a high Curie temperature (T _c ) and usable in a wide temperature range.

In order to solve the above problems, the method for producing a piezoelectric composition according to one aspect of the present invention, (a) PbO, ZrO ₂ , TiO ₂ , NiO, ZnO, Nb ₂ O ₅ powder having a purity of 99% or more according to the composition (B) further weighing ZnO and NiO by w mol% (0 <w ≦ 10) of the basis weight in step (a), (c) step (a) and ( b) wet mixing and calcining the basis weight powder through step (d) and (d) wet mixing and drying the calcined powder passed through step (c) with an alcohol solvent, and (e) the (d) Molding and sintering the dry powder subjected to step).

Here, in step (e), it is preferable to sinter for 1 to 20 hours at 800 to 1000 ° C. After step (e), after (f) grinding the sintered sample, the electrode material is applied and polled. It may further comprise the step of.

The piezoelectric composition according to another aspect of the present invention is (1-xy) Pb (Zr _{1 - z} Ti _z ) O ₃ -x Pb (Ni _1/3 Nb _2/3 ) O ₃ -yPb (Zn _1/3 Nb _{2 / 3} ) O ₃ [(1-xy) PZ _{1 - z} T _z -xPNN-yPZN], wherein x + y is 0.3≤x + y≤0.55, z is 0.50≤z≤0.65 capable of low temperature sintering A piezoelectric composition, and according to another aspect of the present invention, a piezoelectric element including the piezoelectric composition as described above is provided.

According to the present invention, it is possible to produce homogeneous PZT-PNN-PZN piezoelectric ceramics by the uncomplicated high-synthesis reaction method, and to manufacture PZT-PNN-PZN piezoelectric ceramics having sinterable and excellent piezoelectric properties even at low temperature. It is possible.

In addition, PZT-PNN-PZN ceramics according to the present invention has a high Curie temperature (Tc), it is possible to manufacture and use a piezoelectric device in a wide temperature range.

1 and 2 are flowcharts illustrating a method of manufacturing a piezoelectric composition according to an embodiment of the present invention.
Figure 3 is the basis weight of the additional ZnO and NiO (0≤w≤2.0) of the w-phase synthesis by the _{0.65PZ 0 .46 T 0 .54 -0.175PNN-} 0.175PZN X-ray diffraction pattern of the ceramic at 880 ℃ .
4 is not added to a basis weight _{0.65PZ 0 .46 T 0 .54 -0.175PNN-} 0.175PZN ceramic density distribution of the sintered at various temperatures and having a basis weight in addition to ZnO and NiO (0≤w≤2.0) as much as w It is shown in comparison with the case.
5 is 0.65PZ sintered at 900 ℃ for 4 h _{1 - z T z -0.175PNN-0.175PZN} (0≤w≤2.0) shows the XRD diffraction pattern of the Ti amount of the piezoelectric material.
6 is 4 hours, and a ₁ 0.65PZ sintered for 16 hours at various temperatures _- a diagram showing the XRD diffraction pattern of the Ti amount in the _{z T z -0.175PNN-0.175PZN (0≤w≤2.0} ) piezoelectric material.
FIG. 7 is an electron micrograph showing changes in microstructure according to Ti amount of 0.65PZ _{1 - z} T _z -0.175PNN-0.175PZN (0 ≦ w ≦ 2.0) piezoelectric materials sintered at 900 ° C. for 4 hours and 16 hours. .
8 is 4 hours, and a ₁ 0.65PZ sintered for 16 hours at various temperatures _- a diagram showing the piezoelectric constant in accordance with the amount of Ti _{z T z -0.175PNN-0.175PZN (0≤w≤2.0} ) piezoelectric material.
Figure 9 is 4 hours, and a ₁ 0.65PZ sintered for 16 hours at various temperatures _- a view showing the electromechanical coupling factor according to the amount of Ti _{z T z -0.175PNN-0.175PZN (0≤w≤2.0} ) piezoelectric material.
Figure 10 is 4 hours, and a ₁ 0.65PZ sintered for 16 hours at various temperatures _- a diagram showing the dielectric constant according to the amount of Ti _{z T z -0.175PNN-0.175PZN (0≤w≤2.0} ) piezoelectric material.
11 is a diagram showing the variation of dielectric constant with temperature of _{0.65PZ 0 .46 T 0 .54 -0.175PNN-} 0.175PZN (0≤w≤2.0) piezoelectric material is sintered at 900 ℃ for 4 hours.

 Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. It is noted that the terms "comprises" and / or "comprising" used in the specification are intended to be inclusive in a manner similar to the components, steps, operations, and / Or additions.

In accordance with the present _{invention, Pb (ZrTi) O 3 [} PZT] suitable amount of the piezoelectric material based _{Pb (Ni 1/3 Nb 2/3) O} 3 [PNN] and _{Pb (Zn 1/3 Nb 2} /3) O 3 [PZN] is co-synthesized to produce a piezoelectric composition capable of low temperature sintering and having excellent piezoelectric constants and electromechanical coupling coefficients.

The chemical formula of the piezoelectric composition according to the present invention is (1-xy) Pb (Zr _{1 - z} Ti _z ) O ₃ -xPb (Ni _1/3 Nb _2/3 ) O ₃ -yPb (Zn _1/3 Nb _2/3 ) O ₃ [(1-xy) PZ _{1 - z} T _z -xPNN-yPZN], where 0.3 ≦ x + y ≦ 0.55 and z have a composition range of 0.50 ≦ z ≦ 0.65.

Now, the method for producing the piezoelectric composition according to the present invention will be described in detail. 1 is a flowchart illustrating a method of manufacturing a piezoelectric composition according to the present invention, and FIG. 2 is a flowchart illustrating step S110 of FIG. 1 in more detail.

As shown in Figure 1, the method for producing a piezoelectric composition according to the present invention consists of three steps.

Among these, the first step is to prepare a (1-xy) PZ _{1 - z} T _z - _x PNN-yPZN (0.25≤x + y≤0.55, 0.50≤z≤0.65) powder (S110).

Referring to step S110 in more detail with reference to FIG. 2, first, PbO, ZrO ₂ , TiO ₂ , NiO, ZnO, and Nb ₂ O ₅ powder having a purity of 99% or more as an initial raw material are weighed according to the composition (S111). In order to suppress the formation of the PN secondary phase and to form a homogeneous phase, additional weights of ZnO and NiO in a weighted amount of w mol% (0 <w ≦ 10) are further added (S112).

Conventionally, in order to homogeneously synthesize PZT-PNN or PZT-PZN piezoelectric ceramics, a double phase synthesis method such as column bite method was used. However, in the present invention, the secondary phase of PN phase is further added by adding Ni and Zn during initial powder synthesis. Homogeneous homogeneity without phases can be induced. This leads to the synthesis of a homogeneous phase leading to an improvement in piezoelectric properties and low temperature sintering. In addition, this method is commercially simple and easy, resulting in less expensive and homogeneous phases for mass production.

Next, the powder weighed in steps S111 and S112 is wet mixed with zirconia balls in polypropylene using an alcohol solvent for 24 hours (S113).

The powder mixed by wet mixing was dried in an oven at 100 ° C. (S114), and then calcined at 700 to 1000 ° C. for 1 to 10 hours (S115) to form a (1-xy) PZ _{1 - z} T _z -x PNN-yPZN phase. Synthesis (S116) (1-xy) PZ _{1 - z} T _z -x PNN-yPZN powder is prepared (S117).

Next, the mixed (1-xy) PZ _{1 - z} T _z -x PNN-yPZN powder is wet mixed with an alcohol solvent for 48 hours and then dried (S120).

Finally, the dried powder is sintered for 1 to 20 hours at 800 to 1000 ° C. after pressure molding into a cylindrical molded body (S130). The piezoelectric composition according to the embodiment of the present invention is prepared.

After grinding the sintered sample in this way, after applying the electrode material, after applying 3-4kV / mm DC bias for 1 hour at 120-150 ^o C temperature in silicone oil (poling) Measure

According to the present invention, the Curie temperature can be increased by increasing the content of PZN (140 ° C.) having a Curie temperature higher than PNN relative to PZT-PNN. In general, PZT-PNN piezoelectric ceramics have a low Curie temperature of 200 ° C. or less due to the low Curie temperature (-120 ° C.) of the PNN. Has a high Curie temperature, so that it can be applied to a wider range of use in the design of piezoelectric materials, and can minimize the reduction of piezoelectric properties occurring during the assembly process.

On the other hand, PZT-PNN ceramic has excellent piezoelectric properties, but the low temperature sintering process is not easy, and when the low temperature sintering aid is added, the piezoelectric properties are remarkably inferior. On the other hand, PZT-PZN ceramics exhibit relatively lower piezoelectric properties than PZT-PNN but have the advantage of being sinterable at 900 ° C. Thus, by adding PZT-PZN ceramics to PZT-PNN ceramics as in the present invention, a material satisfying the high piezoelectric properties of PZT-PNN and the low sintering temperature of PZT-PZN can be obtained. The piezoelectric material having high piezoelectric properties and capable of low-temperature sintering can use cheaper internal electrodes, and the majority of piezoelectric materials are used in a stack, and thus, a large production cost can be saved.

In the case of PZT piezoelectric ceramics, the piezoelectric properties are rapidly improved in the Morphotropic Phase boundar (MPB) region, so the composition near MPB should be found to improve the piezoelectric properties. However, in the case of PZT piezoelectric ceramics, the MPB composition changes with the addition of relaxer materials such as PNN and PZN. Therefore, the new MPB composition should be determined according to the content of PNN and PZN, and the phase change can be controlled by changing the ratio of Zr / Ti in PZT, which can be analyzed by analyzing the X-ray diffraction pattern.

Hereinafter, preferred embodiments of the present invention will be described.

The piezoelectric composition according to the preferred embodiment of the present invention is represented by the chemical formula 0.65Pb (Zr _{1 -z} Ti _z ) O ₃ -0.175Pb (Ni _1/3 Nb _2/3 ) O ₃ -0.175Pb (Zn _1/3 Nb _{2 / 3} ) O ₃ [0.65PZ _{1 - z} T _z -0.175PNN-0.175PZN]. Here, x = 0.175, y = 0.175, and z are 0.53≤z≤0.58.

In order to prepare such a piezoelectric composition, PbO, ZrO ₂ , TiO ₂ , NiO, ZnO, and Nb ₂ O ₅ powder having a purity of 99% or more as an initial raw material were basis weighted according to the composition. In addition, to suppress the formation of the PN secondary phase and to further weigh 2 mol% (w = 2) of ZnO and NiO in a weighted amount to form a homogeneous phase, and 24 hours with zirconia balls in polypropylene Wet mixing with alcohol solvent. The wet mixed pulverized powder was dried in an oven at 100 ° C., and then calcined at 880 ° C. for 4 hours to prepare a powder by synthesizing a 0.65PZ _{1 - z} T _z -0.175PNN-0.175PZN phase.

In order to reduce the particle size of the compatible 0.65PZ _{1 - z} T _z -0.175PNN-0.175PZN powder, the mixture was wet mixed with an alcohol solvent for 48 hours and then dried in an oven at 100 ° C.

 Subsequently, the dried powder was press-molded at a pressure of 0.5 t / cm 2 into a cylindrical molded body having a diameter of 16 mm and a height of about 1.2 to 1.3 mm, and then sintered at 800 to 1000 ° C. for 1 to 20 hours.

The sintered sample was polished to a constant thickness of 1 mm, and then silver was coated with an electrode material, followed by heat treatment at 550 ° C. for 10 minutes to form an electrode. In order to impart piezoelectric properties, the piezoelectric properties were measured 24 hours after polarization by applying a 3-4kV / mm DC bias for 1 hour at 120-150 ^° C. in silicon oil.

The sintering degree of the specimen was measured using the Archimedes method, and whether the calcined specimens were compatible with each other and the secondary phase formation of the specimens after sintering was confirmed by using an X-ray diffraction pattern. The piezoelectric constant (d ₃₃ ) was measured using a piezoelectric constant meter, and the electromechanical coupling coefficient (k _p ) of the specimen was measured using an impedance analyzer (HP4294A). Curie temperature of the specimen was determined by measuring the change in dielectric constant with temperature.

Figure 3 is the basis weight of the additional ZnO and NiO (0≤w≤2.0) of the w-phase synthesis by the _{0.65PZ 0 .46 T 0 .54 -0.175PNN-} 0.175PZN X-ray diffraction pattern of the ceramic at 880 ℃ . The addition of synthetic before adequate amount of ZnO and NiO is Pb ₃ O ₄ to ₁₃ of Nb suppress the formation of secondary prochlore, can help the homogeneous _{0.65PZ 0 .46 T 0 .54 -0.175PNN-} 0.175PZN phase synthesis.

In addition, referring to the density distribution of Figure 4 it can be confirmed the effect of homogeneous homogeneity on the sintering temperature. 4 is not added to a basis weight _{0.65PZ 0 .46 T 0 .54 -0.175PNN-} 0.175PZN ceramic density distribution of the sintered at various temperatures and having a basis weight in addition to ZnO and NiO (0≤w≤2.0) as much as w It is shown in comparison with the case. Homogeneous homogenous specimens (w = 2) were added at the low sintering temperature below 900 ° C by adding the appropriate amount of ZnO and NiO before phase synthesis, and low temperature sintering was possible without special additives. When this reference to Figure 3, a 0.65PZ _{0 .46} T _{0 .54} formation of -0.175PNN-0.175PZN ceramic homogeneous is meant to enable low-temperature sintering only the employment of the PZN-PZT PNN without any sintering aid.

5 is 0.65PZ sintered at 900 ℃ for 4 h _{1 - z T z -0.175PNN-0.175PZN} (0≤w≤2.0) shows the XRD diffraction pattern of the Ti amount of the piezoelectric material. In the case of z = 0.54, the rhombohedral phase and the tetragonal phase coexist. That is, it means that the MPB composition can be found by changing the ratio of Ti / Zr according to the content of PNN and PZN, and it can be seen that excellent piezoelectric properties can be realized near the MPB composition.

6 is 4 hours, and a ₁ 0.65PZ sintered for 16 hours at various temperatures _- a diagram showing the XRD diffraction pattern of the Ti amount in the _{z T z -0.175PNN-0.175PZN (0≤w≤2.0} ) piezoelectric material. As shown in Figure 6, it can be confirmed that the densification in all compositions up to a temperature of 900 ℃ or less. This further means that the sintering temperature is reduced by forming a homogeneous phase due to the basis weight NiO and ZnO, as well as low temperature sintering is possible due to the inclusion of PZN.

FIG. 7 is an electron micrograph showing changes in microstructure according to Ti amount of 0.65PZ _{1 - z} T _z -0.175PNN-0.175PZN (0 ≦ w ≦ 2.0) piezoelectric materials sintered at 900 ° C. for 4 hours and 16 hours. . Referring to FIG. 9, the specimen sintered at 900 ° C. for 4 hours showed a grain size of 5 μm or less, regardless of Ti content. On the other hand, when the sintering time was further increased, the grain size was grown to 10 μm, which was about twice as large. Since the piezoelectric properties increase as the grain size of the specimen increases, this indicates that the piezoelectric properties of the specimen can be improved by increasing the sintering time.

8 is 4 hours, and a ₁ 0.65PZ sintered for 16 hours at various temperatures _- a diagram showing the piezoelectric constant in accordance with the amount of Ti _{z T z -0.175PNN-0.175PZN (0≤w≤2.0} ) piezoelectric material. Referring to FIG. 8, the z-0.54 specimen sintered at 920 ° C. exhibited excellent piezoelectric properties of 623 pC / N. This is in addition to obtaining a proper MPB composition by controlling the Ti / Zr ratio, but also showing high piezoelectric properties at low sintering temperature with homogeneous homogeneity. In addition, z = 0.54 specimens sintered at 900 ° C. for 16 hours showed very good piezoelectric properties of 656 pC / N, due to the increased grain size as can be seen in FIG. 7 in addition to MPB, even at specimens below 900 ° C. It means that the piezoelectric properties can be further improved by an appropriate sintering time.

Figure 9 is 4 hours, and a ₁ 0.65PZ sintered for 16 hours at various temperatures _- a view showing the electromechanical coupling factor according to the amount of Ti _{z T z -0.175PNN-0.175PZN (0≤w≤2.0} ) piezoelectric material. Z = 0.54 specimens sintered at 920 ° C showed the best kp value of 72% and overall high kp value of 60% or more due to the tendency of good density. In addition, the tendency according to the Ti content showed similar results to excellent piezoelectric properties in the MPB region.

Figure 10 is 4 hours, and a ₁ 0.65PZ sintered for 16 hours at various temperatures _- a diagram showing the dielectric constant according to the amount of Ti _{z T z -0.175PNN-0.175PZN (0≤w≤2.0} ) piezoelectric material. The z = 0.54 specimens sintered at 920 ° C showed very good piezoelectric and electromechanical coupling coefficients and very low dielectric constants below 2500. Perhaps due to the employment of PZN, excellent piezoelectric properties were realized even at lower permittivity than PNN single employment. This means that if this material is applied to a generator, more power generation can be obtained, and also, when applied as an actuator, the actuator can be operated even at a smaller driving voltage, which is a great advantage when driving a generator or an actuator. Will have

11 is a diagram showing the variation of dielectric constant with temperature of _{0.65PZ 0 .46 T 0 .54 -0.175PNN-} 0.175PZN (0≤w≤2.0) piezoelectric material is sintered at 900 ℃ for 4 hours. PNN (Tc = -120 ° C.) and PZN (Tc = 140 ° C.) were completely dissolved with PZT (Tc = 360 ° C.) ceramics and showed a high value of 245 ° C., which is the median value of Tc of each component. By increasing the content of PZN it was possible to increase the low Tc of the existing PZT-PNN, which indicates that it can be manufactured and used in a wide temperature range has a very advantageous advantage in the actual device manufacturing.

While the invention has been described in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention. Accordingly, the appended claims will include such modifications and variations as long as they fall within the spirit of the invention.

Claims (5)

(1-xy) Pb (Zr _1-z Ti _z ) O ₃ -xPb (Ni _1/3 Nb _2/3 ) O ₃ -yPb (Zn _1/3 Nb _2/3 ) O ₃ [(1-xy) PZ _1-z T _z -xPNN-yPZN], wherein x + y is 0.3 ≦ x + y ≦ 0.55, and z is 0.50 ≦ z ≦ 0.65 as a method for producing a piezoelectric composition.
(a) weighing PbO, ZrO ₂ , TiO ₂ , NiO, ZnO, and Nb ₂ O ₅ powder having a purity of 99% or more according to the composition;
(b) further weighing ZnO and NiO by w mol% (0 <w ≦ 10) of the basis weight in step (a);
(c) wet grinding and calcining the powder weighed through the steps (a) and (b), and
(d) wet mixing the calcined powder, which has been passed through the step (c) with an alcohol solvent, and then drying the powder;
(e) Method for producing a piezoelectric composition comprising the step of molding and sintering the dry powder passed through the step (d) for 1 to 20 hours at 800 ~ 1000 ℃. delete The method of claim 1,
After the step (e)
(f) after polishing the sintered sample, applying and polling the electrode material. delete delete

Images