KR20080000010A - Multilayer type 2-2 piezo-composite ultrasonic transducer and method for the same - Google Patents

Abstract

A multilayer 2-2 piezo-composite ultrasonic transducer and a manufacturing method thereof are provided to cause a large displacement by a low voltage and to use a wide range of frequency. Two first inner electrode layers are exposed from a left side of a piezoceramic plate and directly contacted with a first outer electrode layer. The first inner electrode layers are not exposed from a right side of the piezoceramic plate but buried under a piezoelectric layer apart from a second outer electrode layer. Two second inner electrode layers are arranged to be opposed to the first inner electrode layers and contacted with the outer electrode layer, which is not contacted with the first inner electrode layers. The first and second inner electrode layers are alternatively arranged in the piezoelectric layers. When electric power is supplied to the outer electrode layers, a voltage is induced between the first and second inner electrode layers.

Description

Multilayer type 2-2 Piezo-Composite Ultrasonic Transducer and Method for the same

1 shows a 2-2 piezoelectric ceramic-polymer composite having a multilayer structure according to an embodiment of the present invention, (a) shows the structure of a piezoelectric ceramic-polymer composite having a 2-2 structure composed of multilayers. , (b) is a schematic diagram showing the direction of occurrence of displacement change due to voltage application after the electrode is placed and polled in the structure of (a), (c) is for each piezoelectric ceramic plate included in the composite of (a) Different arrangement models of external electrodes.

FIG. 2 is a photograph of a specimen of a 2-2 piezoelectric ceramic-polymer composite having a multilayer structure prepared according to an embodiment of the present invention.

3 is a SEM photograph after sintering of a 2-2 piezoelectric ceramic-polymer composite having a multilayer structure prepared according to an embodiment of the present invention, (a) shows a piezoelectric ceramic plate having a multilayer structure sintered at 900 ° C. for 4 hours. ) Is a SEM photograph observed from above, and (b) is a photograph observed from the side of a fractured cross section of a piezoelectric ceramic plate having a multilayer structure.

FIG. 4 is a displacement graph according to voltage of a 2-2 piezoelectric ceramic-polymer composite having a multilayer structure manufactured according to an embodiment of the present invention (where 31, 32, and 33 directions are defined in FIG. 1B), ( a) is a displacement graph of the composite of the present invention, and (b) is a displacement graph of a piezoelectric ceramic-polymer composite having a general 2-2 structure for comparison.

5 is a displacement graph in the direction of d33 according to the frequency of the 2-2 piezoelectric ceramic-polymer composite having a multilayer structure manufactured according to an embodiment of the present invention.

The present invention is a piezoelectric ceramic having a multi-layer structure consisting of 2-2 - related to a polymer composite material and, more particularly, the longitudinal vibration mode (d ₃₃₎ of the single-layer by forming the piezoelectric ceramic plate, a multi-layer structure having an inner electrode The present invention relates to a piezoelectric ceramic-polymer composite having a 2-2 structure composed of a multilayer, which is not limited in size and can improve the size of the longitudinal vibration mode.

Current ultrasonic transceivers use a composite of ceramic and polymer. The piezoelectric material using PZT shows excellent piezoelectric properties in each of the excellent vibration modes (d ₃₃ to 510 pC / N, d ₃₁ to -230 pC / N), but the hydrostatic piezoelectric property (d _h ) has a small disadvantage. Generally hydrostatic piezoelectric properties of the _{PZT (d h = d 33 +} 2 d 31) is substantially 50 pC / N out andoegi because large a d ₃₃ vibration mode in the thickness direction while maintaining a constant by reducing the lateral vibration mode of d ₃₁ An ultrasonic oscillator with d _h is used. In addition, pure PZT ceramics have a very high density of themselves, which causes problems in transmission and reception because the underwater impedance is very different from water. That is, when sound waves reach a medium of low density such as water and a medium of high density, such as ceramics, the absorption rate decreases due to the lack of absorption of the wave in the dense medium. As a result, ceramic-polymer piezoelectric composites have come out to reduce the density of piezoelectric materials to help absorb sound waves and to transmit and receive sound waves with directivity. According to the form, there are 10 types such as 1-3, 2-2, 0-3, 3-3, and the first number is ceramic and the second number is epoxy. For example, in the case of 1-3, a linear piezoelectric fiber of 1 is planted in a polymer matrix of 3, and in the case of 2-2, a plate-like piezoelectric plate is placed in a polymer plate. The most representative of such a ceramic-polymer composite is a piezoelectric ceramic-polymer composite using 1-3 or 2-2 mode. In the case of the 2-2 structure, since the piezoelectric plates are arranged in one direction, d ₃₃ is kept constant, while the respective plates are separated so that the d ₃₁ mode is suppressed and d _h is large. In addition, since the polymer density is low, the overall impedance is drastically lowered to achieve impedance matching between water and the piezoelectric body to maximize the efficiency of transmission and reception.

However, in the case of the conventional simple piezoelectric polymer composite having no internal electrode, the displacement of the piezoelectric body is limited to the value of the longitudinal piezoelectric constant (d ₃₃ ) or less, so that it is difficult to obtain a large displacement and the driving voltage (> 1000 V) of the piezoelectric body is high. There is this. In addition, because amplification is used at the resonant frequency to obtain a large displacement, the operating frequency is limited to the resonant frequency, so that ultrasonic waves having various frequencies cannot be generated.

Accordingly, the present invention has been made to solve the above problems of the prior art.

Accordingly, it is an object of the present invention to overcome the problem that the displacement of the piezoelectric body is limited by the longitudinal piezoelectric constant d ₃₃ of a single piezoceramic plate. It is possible to provide a 2-2 piezoelectric ceramic-polymer composite having a multilayered structure having a longitudinal piezoelectric constant and excellent piezoelectric properties. Such piezoelectric composites not only generate very large displacements at low voltages, but can also be ultrasonically oscillated at low frequencies, so that they can be used in ultrasonic oscillators.

It is also an object of the present invention to provide a method for producing a 2-2 piezoelectric ceramic-polymer composite having a multilayer structure by a coextrusion method.

Other objects and advantages of the present invention will be more clearly understood by the following detailed description of the invention.

The present invention provides a piezoelectric ceramic-polymer composite having a 2-2 structure in which a plurality of piezoelectric ceramic plates and a plurality of polymer resin plates are alternately bonded. A feature of the present invention is that the piezoelectric ceramic plates used in the piezoelectric ceramic-polymer composite having a 2-2 structure have a plurality of piezoelectric layers and internal electrode layers formed in a multilayer structure. That is, each of the piezoelectric ceramic plates is composed of a plurality of piezoelectric layers containing piezoelectric materials and one less internal electrode layer (s) than the number of piezoelectric layers interposed therebetween. In addition, the composite of the present invention is in contact with the internal electrode layers of each piezoelectric ceramic plate at the side of the piezoelectric ceramic plates (ie, the side of the piezoelectric ceramic-polymer composite) through the internal electrode layers or the top surface of the piezoelectric ceramic plates or A pair for forming a voltage on each piezoelectric layer of each piezoelectric ceramic plate by lamination or coating formed on the lower surface (ie, the upper or lower surface of the piezoelectric ceramic-polymer composite) in contact with the upper or lower piezoelectric layer of each piezoelectric ceramic plate. External electrode layers; In the above, the internal electrode layers formed on each of the piezoelectric ceramic plates are exposed at the left side of the piezoelectric ceramic plate to be in contact with the one external electrode layer, but are not exposed at the right side of the piezoelectric ceramic plate to be in contact with the other external electrode layer. And an external electrode layer formed on the left side of the first internal electrode layer which is not formed and on the contrary, is exposed on the right side of the piezoelectric ceramic plate and is in contact with the external electrode layer formed on the right side, but not exposed on the left side of the piezoelectric ceramic plate. Are alternately formed second internal electrode layers which are not in contact with each other. The external electrode layers are formed to be in contact with the internal electrode layers on one side of each piezoelectric ceramic plate (ie, the side of the piezoelectric ceramic-polymer composite) so that the adjacent internal electrode layers (first and second internal electrode layers) are formed. And a voltage is formed between the extension layer and the inner electrode layer formed on the upper surface or the lower surface (ie, the upper surface or the lower surface of the piezoelectric ceramic-polymer composite material) extending from the side surface of each piezoelectric ceramic plate. To make it possible.

In another aspect, the present invention provides a method for producing a 2-2 piezoelectric ceramic-polymer composite having a multilayer structure including the internal electrode as described above.

Hereinafter, the present invention will be described in detail with reference to the drawings.

1 shows a 2-2 piezoelectric ceramic-polymer composite having a multilayer structure according to an embodiment of the present invention, (a) shows the structure of a piezoelectric ceramic-polymer composite having a 2-2 structure composed of multilayers. , (b) is a schematic diagram showing the direction of occurrence of displacement change due to voltage application after the electrode is placed and polled in the structure of (a), (c) is for each piezoelectric ceramic plate included in the composite of (a) Different arrangement models of external electrodes.

As shown in Fig. 1A, the structure of a conventional piezoelectric ceramic-polymer composite having a structure of 2-2 is that a plurality of piezoelectric ceramic plates made of piezoelectric ceramics are arranged in parallel in one direction and a thermoplastic resin, for example, an epoxy resin therebetween. Has a matrix structure filled with. A feature of the present invention is that the piezoelectric ceramic plate used in the structure of the conventional piezoelectric ceramic-polymer composite having a 2-2 structure has a multilayer structure in which a plurality of piezoelectric layers and internal electrode layers are alternately stacked. Each piezoelectric ceramic plate includes five piezoelectric layers containing a piezoelectric material. Four piezoelectric layers are interposed between the piezoelectric layers, that is, one less than the number of piezoelectric layers. Such a piezoelectric ceramic plate may be generally manufactured by successive lamination of a piezoelectric layer and an internal electrode layer by a coextrusion method.

Referring to FIG. 1B, the shape of the internal electrodes, the connection structure with the external electrodes, and the occurrence of displacement of the piezoelectric ceramic-polymer composite matrix will be described. The directions mentioned in the description are based on the directions defined and defined according to the arrangement of FIG. 1B. One external electrode is integrally formed on the upper surface and the left side of the piezoelectric ceramic-polymer composite matrix, and the other external electrode is integrally formed on the lower surface and the right side.

In the present invention, the internal electrode layers are divided into two types. That is, the first internal electrode layer formed on the left side of the piezoelectric ceramic plate and in contact with one external electrode layer but not exposed on the right side of the piezoelectric ceramic plate and not in contact with the other external electrode layer and the second second electrode formed in the opposite shape It is divided into internal electrode layers. As shown in FIG. 1B, the two first inner electrode layers are exposed at the left side of the piezoelectric ceramic plate to directly contact one outer electrode layer, but are not exposed at the right side of the piezoelectric ceramic plate and buried in the piezoelectric layers by a certain distance. Not only does not directly contact other external electrode layers, but also is not electrically connected. The two second inner electrode layers correspond to the outer electrode layer to which the first inner electrode layers do not contact, in a form opposite to that of the first inner electrode layers. These first and second internal electrode layers are alternately arranged in the piezoelectric layers. Thus, as shown in the drawing, when power is supplied from the outside to the external electrode layers, a voltage is generated between the neighboring first and second internal electrode layers to form an electric field.

On the other hand, in the piezoelectric ceramic plate of the present invention, the external electrode layers not only directly contact the internal electrode layers on the side of the piezoelectric ceramic plate but also have their extension layers extending from the side and formed on the upper or lower surface of the piezoelectric ceramic plate. These extension layers are arranged to form a voltage between the internal electrode layers. In FIG. 1B, two first inner electrode layers and two second inner electrode layers are formed, and the outer electrode layers formed on the left side of the extension layers of the outer electrode layers to form a voltage with the inner electrode layers are extended to the upper surface. The external electrode layer formed on the right side with the extension layer extends to the lower surface and has an extension layer on the lower surface. On the contrary, when the extension layer is formed, it is obvious that a voltage cannot be formed between the internal electrode layers.

As shown in FIG. 1B, when the external electrodes are formed and polled under high voltage, polarization occurs in the multilayer stacking direction of the piezoelectric ceramic plate, and then an AC voltage of an appropriate frequency is applied to the electrodes. In the direction d ₃₃ a displacement change, ie contraction and expansion occurs. Such longitudinal displacement is limited to less than or equal to the longitudinal displacement of a single piezoelectric layer in a piezoelectric ceramic-polymer composite using a conventional piezoelectric ceramic plate having a single piezoelectric ceramic having no internal electrode, whereas the composite of the present invention has an internal electrode. Due to the multilayer structure, longitudinal displacement of a single piezoelectric layer may occur cumulatively, thereby obtaining a large displacement.

Meanwhile, FIG. 1C illustrates the structure of the piezoelectric ceramic plate and the external electrode having a different shape from the above, and a connection form thereof. As shown in FIG. 1C, a piezoelectric body having one first internal electrode layer and one second internal electrode layer is illustrated. In the ceramic plate (second of FIG. 1C), the external electrode layer formed on the left side thereof extends to have an extension layer formed on the lower surface thereof. In addition, in the piezoelectric ceramic plates (first and third in FIG. 1C) where the number of first internal electrode layers is one greater than the number of second internal electrode layers, the external electrode layers formed on the left side of the first internal electrode layer do not substantially extend to the upper and lower surfaces of the piezoelectric ceramic plates. The external electrode layer formed on the side has an extension layer extending to both the upper and lower surfaces. (When the number of the first internal electrode layers is less than the number of the first internal electrode layers, the shape becomes symmetrical to the above. However, this arrangement is consistent with the above. The internal electrode layer and the second internal electrode layer are relative concepts.)

Since the piezoelectric ceramic plate of the present invention as described above has not only a piezoelectric layer but also an internal electrode layer, it is preferably manufactured by co-sintering, and more preferably in order to use a low melting point conductive metal such as silver (Ag). It is manufactured by co-sintering. In addition, the piezoelectric ceramic plate of the present invention is preferably produced by a co-extrusion method. To this end, it is preferable to use a PZN-PZT composite in which PZN and PZT are complex as the piezoelectric material used in the present invention. In addition, in order to simultaneously form the internal electrode by co-extrusion, it is preferable to form the internal electrode with a mixture of the same material and metal as the components of the piezoelectric material, wherein silver (Ag) is used as the metal at low temperature after co-extrusion. Simultaneous firing is possible.

Prior patent application 2003-0089272 (filed date: December 10, 2003, publication number: 2005-0056331, published date: June 16, 2005) of the main inventors of the present invention is less than 1000 ℃, preferably 900 A PZN-PZT composite with a special composition capable of low temperature co-firing with silver (Ag) at or below C is disclosed. The special composition of such a PZN-PZT composite is that in the composition of the xPZN- (1-x) PZT composite, x is in the range of 0.1 to 0.6, preferably in the range of 0.3 to 0.5, and Pb (Zr _y , in the O ₃ composition Ti _{1 -y),} y may be a range of 0.35 ~ 0.55, PZN-PZT complex of _{xPb (Zn 1/3 Nb 2} /3) O 3 - (1-x) Pb (Zr y, Ti _{In the 1- y} ) O ₃ composition, x and y are chosen to be the composition of the Morphotropic Phase Boundary (MPB) region of the resulting PZN-PZT complex. Such a special composition of PZN-PZT is preferably required for carrying out co-firing with silver (Ag) in the method of the present invention, and the reason is well described in the above patent publication. Therefore, the said patent document is integrated in the specification of this invention.

The content of silver in the mixture of PZN-PZT composite and silver (Ag) used as the internal electrode in the present invention is preferably 30 to 80% by weight. When the content of silver is in the above range, there is no big difference from the electrical conductivity of pure silver, and thus it can sufficiently serve as an internal electrode. In the present invention, using the mixture as described above without using pure metal, in particular silver, as an internal electrode, which uses a high residual stress on the surface of the piezoelectric layer due to the large difference in thermal expansion coefficient between the piezoelectric layer and the conductive layer. This is to obtain excellent displacement characteristics and driving force. In addition, it is possible to obtain excellent durability by improving the interlayer adhesion between the piezoelectric layer and the internal electrode by co-extrusion.

Previous patent application No. 2003-0093527 (filed date: December 19, 2003, publication number: 2005-0061910, published date: June 23, 2005) of the main inventor of the present invention is a piezoelectric layer of PZN-PZT composite And an actuator comprising a conductive layer of a PZN-PZT / Ag mixture. Such actuators are manufactured by conventional extrusion and low temperature co-firing as conventional monolithic structures. This application proposes a special composition of piezoelectric materials for low temperature co-firing, complex construction of conductive layers for high residual stresses, and improvement of interlayer adhesion by co-extrusion. Therefore, the said patent document is integrated in the specification of this invention.

The piezoelectric ceramic plate of the present invention is preferably manufactured by co-extrusion, first preparing a mixture of a piezoelectric material and a thermoplastic resin for the piezoelectric layer and a mixture of a piezoelectric material / metal mixture and a thermoplastic resin for the internal electrode layer, the mixture To prepare a plate or block of a predetermined thickness. Piezoelectric ceramic plates are formed by coextruding these initial feedrods with the plates arranged in the desired structure and arrangement. Thereafter, the extruded body is heat-treated to burn off the thermoplastic resin contained in the extruded body and to sinter the piezoelectric material. At this time, the heat treatment process may be carried out in one step, but is usually performed in a first step of slowly heating to about 650 ℃ and a second process of slowly heating to a temperature of about 900 ℃ or less than 1000 ℃. The thermoplastic resin is removed in the first step, and the piezoelectric material is sintered in a PbO atmosphere in the second step.

The piezoelectric ceramic-polymer composite matrix can be obtained by arranging the sintered piezoelectric ceramic plates in a mold as described above and filling them with an epoxy resin to cure them. Ultrasonic oscillation is possible by forming an external electrode on the top, left and bottom and bottom and right sides of the composite matrix, polling, and then applying an AC voltage of a predetermined frequency. In this case, as the method of forming the external electrode layer, various methods such as lamination and coating may be used, but most simply, the electrode material is directly applied. Silver (Ag) may be used as a material of the external electrode layer.

Hereinafter, embodiments according to the present invention are presented. Since these embodiments are only intended to present specific examples of the present invention, it should not be understood that the scope of the present invention is limited thereto, and that various other variations and modifications may be possible.

Example

Specimen Manufacturing Method

The piezoelectric ceramic plate is made using PZN-PZT, PZN-PZT / Ag composite (internal electrode), and Ag (external electrode). PZN-PZT is a material capable of low temperature sintering (<900 oC) while having excellent piezoelectric properties. PZN-PZT / Ag composites are used as conductive electrode layers. PZN-PZT is a composition _{Pb ((Zn 1/3,} Nb 2/3) 0.2 (Zr 0 .5, Ti 0 .5) 0.8) with O _3, and the amount of Ag of the PZN-PZT / Ag composite 50 wt% It was set as.

PZN-PZT composites were prepared by a solid-phase method using a ball mill using high purity PbO, ZrO ₂ , TiO ₂ , Nb ₂ O ₅ , and ZnO as starting materials. The mixture was initially mixed for 12 hours for mixing and the dry powder was calcined at 850 ° C. for 4 hours. The milled powder was again ball milled for 24 hours to grind. Pure PZN-PZT powder was used for the preparation of the piezoelectric layer of the piezoelectric ceramic plate, and 50% PZN-PZT / 50% Ag powder was used for the preparation of the internal electrode layer. Ethylene ethyl acrylate (EEA 6182; Union Carbide, Danbury, CT) and Acryloid B67 (Rohm and Haas, Philadelphia, PA) were used. The mixture was mixed at 110 ° C. for 2 hours using an internal mixer. Heavy mineral oil (Aldrich Chemical Co. Inc.), stearic acid (Junsei Chemical, Japan) and polyethylene glycol (PEG1000, Acros Organics, NJ, USA) were added to maintain the same viscosity in both layers. The PZN-PZT and PZN-PZT / Ag mixtures were heated at 130 degrees using a 24mm * 24mm square mold to form a block by applying pressure and making them into 4.2 mm plates and 0.6 mm sheets, respectively, and then processing them to arrange the arrangement of FIG. 1A. By combining with five piezoelectric layers and four internal electrode layers, an initial feedrod was made and coextruded again at 105 ° C. into a plate approximately 2 mm thick (total height of the layers). The green sheet having such a multilayer structure is regularly cut at regular intervals in the longitudinal direction of the piezoelectric layer by using CNC machining equipment, and approximately 190 µm x 2 mm x 16 mm (the length of the piezoelectric layer). ), A piezoelectric ceramic plate was obtained. If the sheet materials are inflexible when coextrusion, there will be a step between the ends and the center due to the difference in the length of the piezoelectric layer and the inner electrode layer, but in practice both ends are coextruded under high pressure and heated conditions. At this stage, the flexibility of the piezoelectric layer material is generated so that a distribution is made to fill the voids, so that there is no substantial step difference. In order to remove the binder in the piezoelectric ceramic plate having such a multilayer structure, it was heated while slowly raising the temperature to 600 ℃. At the time of sintering, sintering was carried out in a PbO atmosphere in a well covered alumina crucible to prevent PbO volatilization. The sintered specimens (piezoelectric ceramic plates) were placed in a frame in a constant array, filled with degassing epoxy resin between them, and cured to obtain a multilayer piezoelectric ceramic-polymer composite matrix having a 2-2 structure. One external electrode layer was formed on the top and one side of the matrix, and another external electrode layer was formed on the other side of the matrix, and a high voltage was applied to poll the piezoelectric layer. Then an electric field of 50 V / mm was applied in the silicone oil heated to 70 degrees to measure the electrical properties. Piezoelectric properties were measured by piezoelectric d ₃₃ meter (model ZJ-3D, Institute of Acoustics, Beijing, China). In addition, displacement characteristics according to voltage were measured using a displacement sensor.

In FIG. 2, a specimen actually manufactured according to the present invention can be seen, and in FIG. 3, an enlarged SEM photograph of the specimen can be seen. In the piezoelectric ceramic-polymer composite matrix having a 2-2 structure, the piezoelectric ceramic plate had a thickness of about 190 μm and a channel length of about 880 μm. The thickness of each piezoelectric layer in the piezoelectric ceramic plate was about 260 μm and the thickness of the internal electrode layer was about 40 μm.

Experiment result

In the same manner as described above, a 2-2 piezoelectric ceramic-polymer composite ultrasonic oscillator having a multilayer structure was fabricated using a CNC machining method. According to an embodiment of the present invention it was used to _{0.2 (PbZn 1/3 Nb 2} /3) -0.8 (PbZr 0.5 Ti 0.5) , which can be low-temperature sintering, and show an excellent piezoelectric characteristics to the piezoelectric layer, the piezoelectric body itself, this d ₃₃ ~ 510 It has piezoelectric properties of pC / N, d ₃₁ ~ 230 pC / N, K _P ~ 0.65, K ^T ~ 1700, and 0.5PZN-PZT / 0.5Ag composite with good conductivity is possible with simultaneous internal sintering Was used. Piezoelectric properties were measured by applying an electric field of 50 V / mm, 1 kHz to the specimen thus prepared, and it is shown in Table 1.

Table 1

The 2-2 structured piezoelectric ceramic-polymer composite of the present invention exhibits excellent piezoelectric properties as compared to the conventional single layer 2-2 composite. That is, the value of the longitudinal piezoelectric constant (d ₃₃ ) is 1200 pC / N, which is much higher than that of the conventional piezoelectric constant of 340 pC / N. 4 is a displacement graph according to the electric field. In the case of Figure 4A is a multi-layered 2-2 composite, the direction for each of 33-, 31-, and 32- is the same as in Figure 1B. As the electric field is applied, the displacement in each direction changes linearly, and 6 x 10 ^-5 in 33 directions, 1.03 x 10 ^-5 in 31 directions, 0.2 x in 32 directions for an electric field of 50 V / mm, 1 kHz ¹⁰ shows the displacement of ^five. Defining the piezoelectric constant values from the slope of the displacement graph according to the electric field, d ₃₃ , d ₃₁ , and d ₃₂ show 1200 pC / N, -206 pC / N, and -40 pC / N, respectively. The d ₃₃ value is showing the results nearly identical with the results as measured by a d ₃₃ meter. For the purpose of comparison, it was shown in Figure 4B to measure the properties of a 2-2 composite consisting of a single layer. The calculated values of d ₃₃ , d ₃₁ and d ₃₂ were measured at 340 pC / N, -130 pC / N and -30 pC / N, respectively.

The hydrostatic piezoelectric constant value can be calculated from the following formula.

d _h = d ₃₃ + (d ₃₁ + d ₃₂ ) ------- (1)

g _h = d _h / ε ₃₃ ^T ------- (2)

FoM = d _h xg _h ------- (3)

Where d _h and g _h are the constants of the piezoelectric charge constants and the hydrostatic piezoelectric voltage constants, respectively, and the value of FoM (figure of merit) determines the piezoelectric characteristics. In the case of 2-2 composite of the multilayer d _h computed value is 954 pC / N value of the piezoelectric constant measured by ε ₃₃ ^T = 5100, ε ₀ In view of the constant voltage (g _h) is 21.1 mVm / N and the FOM is 20130 calculated as x 10 ^-15 m ² / N. The general 2-2 complex was used for comparison. d _h and g _h are 180 pC / N and 48.4 mVm / N, respectively, and the FOM is calculated as 8710 x 10 ^-15 m ² / N. The reason for this large value is due to the sharp increase in d ₃₃ . It is FIG. 5 which measured the displacement according to the frequency of a vertical direction, adding 10V. According to FIG. 5, in the embodiment according to the present invention, the resonant frequency is observed at 92 kHz and the corresponding piezoelectric constant is 4300 pC / N, and in the case of the general 2-2 structure, the resonant frequency is measured at 123 kHz. The piezoelectric constant is 600 pC / N.

Such a piezoelectric composite has a very large piezoelectric constant and can be used at a low voltage, and can be used at a wide range of frequencies. Therefore, the piezoelectric composite can be a very useful piezoelectric ultrasonic oscillator.

The present invention provides a multilayer 2-2 piezoelectric ceramic-polymer composite composed of a multilayered piezoelectric ceramic plate having a plurality of piezoelectric layers and internal electrodes and a polymer resin matrix. The piezoelectric ceramic-polymer composite according to the invention can be produced in particular by low temperature co-sintering and co-extrusion. According to the present invention, a piezoelectric ceramic plate of a piezoelectric ceramic-polymer composite having a 2-2 structure is formed in a multilayered form having a plurality of piezoelectric layers and internal electrodes. Thus, a piezoelectric ceramic-polymer having a 2-2 structure using a conventional single layer piezoelectric ceramic plate is provided. Overcoming the limitation that the longitudinal displacement of the composites are limited to below the longitudinal displacement of the piezoelectric ceramics can produce larger displacements, making it possible to generate large displacements at low voltages and to apply them to ultrasonic oscillators that can use a wide range of frequencies. can do.

Claims (17)

In the piezoelectric ceramic-polymer composite having a 2-2 structure in which a plurality of piezoelectric ceramic plates and a plurality of polymer resin plates are alternately bonded, Each of the piezoelectric ceramic plates is composed of a plurality of piezoelectric layers including piezoelectric materials and internal electrode layer (s) one less than the number of piezoelectric layers interposed therebetween, In contact with the inner electrode layers of each piezoelectric ceramic plate at the side of the piezoelectric ceramic plates (ie, the side of the piezoelectric ceramic-polymer composite) through the inner electrode layers or the top or bottom of the piezoelectric ceramic plates (ie the piezoelectric A pair of external electrode layers for forming a voltage on each piezoelectric layer of each piezoelectric ceramic plate by lamination or coating formed on the upper or lower surface of the ceramic-polymer composite) in contact with the upper or lower piezoelectric layer of each piezoelectric ceramic plate. , In the above, the internal electrode layers formed on each of the piezoelectric ceramic plates are exposed at the left side of the piezoelectric ceramic plate to be in contact with the one external electrode layer, but are not exposed at the right side of the piezoelectric ceramic plate to be in contact with the other external electrode layer. And an external electrode layer formed on the left side of the first internal electrode layer which is not formed and on the contrary, is exposed on the right side of the piezoelectric ceramic plate and is in contact with the external electrode layer formed on the right side, but not exposed on the left side of the piezoelectric ceramic plate. Are alternately formed second internal electrode layers which are not in contact with each other, The external electrode layers are formed to be in contact with the internal electrode layers on one side of each piezoelectric ceramic plate (ie, the side of the piezoelectric ceramic-polymer composite) so that the adjacent internal electrode layers (first and second internal electrode layers) are formed. And a voltage is formed between the extension layer and the inner electrode layer formed on the upper surface or the lower surface (ie, the upper surface or the lower surface of the piezoelectric ceramic-polymer composite material) extending from the side surface of each piezoelectric ceramic plate. Characterized in that Piezoelectric ceramic-polymer composite having a 2-2 structure composed of multiple layers. The method of claim 1, The number of the first internal electrode layers is greater than the number of the second internal electrode layers by one, and the external electrode layers contacting the first internal electrode layers are formed on the left side of the piezoelectric ceramic-polymer composite and the second The outer electrode layer in contact with the inner electrode layer (the outer electrode layer facing the outer electrode layer in contact with the first inner electrode layer when there is no second inner electrode layer (the number is zero)) is the right side of the piezoelectric ceramic-polymer composite. A piezoelectric ceramic-polymer composite having a structure of 2-2, wherein the piezoelectric ceramic-polymer composite is formed on the upper and lower surfaces of the piezoelectric ceramic-polymer composite. The method of claim 1, The number of the first inner electrode layer and the second inner electrode layer is the same, and the outer electrode layers contacting the inner electrode layers are formed on one side of the piezoelectric ceramic-polymer composite and extend therefrom. A piezoelectric ceramic-polymer composite having a 2-2 structure, which is formed on either of the upper and lower surfaces of the polymer composite. The method of claim 1, The piezoelectric material of the piezoelectric layer is a piezoelectric ceramic-polymer composite having a 2-2 structure, characterized in that the PZN-PZT composite complexed with PZN and PZT. The method of claim 4, wherein The internal electrode layer is a piezoelectric ceramic-polymer composite having a structure of 2-2, wherein the internal electrode layer is formed of PZN-PZT / Ag, which is a mixture of PZN-PZT composite and Ag. The method of claim 5, The content of Ag in the PZN-PZT / Ag is 30 to 80% by weight, the piezoelectric ceramic-polymer composite of 2-2 structure. The method of claim 6, In the composition of the xPZN- (1-x) PZT composite used in the PZN-PZT / Ag internal electrode layer and / or the PZN-PZT piezoelectric layer, x is in a range of 0.1 to 0.6. Piezoelectric ceramic-polymer composite. The method of claim 7, wherein In the Pb (Zr _y , Ti _{1 -y} ) O ₃ composition of the PZN-PZT composite used for the PZN-PZT / Ag internal electrode layer and / or the PZN-PZT piezoelectric layer, y is in the range of 0.35 to 0.55 A piezoelectric ceramic-polymer composite having a 2-2 structure. The method of claim 6, The PZN-PZT / Ag internal electrode layer and / or _{xPb (Zn 1/3 Nb 2} /3) of the PZN-PZT composites used for the PZN-PZT piezoelectric layer _{O 3 - (1-x)} Pb (Zr y, Ti _{In the 1 -y} ) O ₃ composition, x and y are selected to be the composition of the Morphotropic Phase Boundary (MPB) region of the resulting PZN-PZT composite, the piezoelectric ceramic-polymer of 2-2 structure Complex. The method of claim 1, The external electrode layer is a piezoelectric ceramic-polymer composite of 2-2 structure, characterized in that formed by coating Ag paste. The method of claim 1, The polymer resin matrix is a piezoelectric ceramic-polymer composite of 2-2 structure, characterized in that the epoxy resin. The method of claim 1, The composite is a piezoelectric ceramic-polymer composite of 2-2 structure, characterized in that applied to the ultrasonic oscillator. Mixing each of the piezoelectric layer material and the internal electrode material with a polymer resin, Extruding the piezoelectric layer material mixture and the internal electrode material mixture using a square mold to form a block, Forming a piezoelectric ceramic plate by chucking and arranging the blocks of the piezoelectric layer material mixture and the blocks of the internal electrode material mixture in order to form an initial feed rod, and then co-extrusion molding; Cutting and processing the green sheet having the multilayer structure by CNC machining equipment to form a piezoelectric ceramic plate having a desired dimension; Heat-treating the piezoelectric ceramic plate to burn off the mixed polymer resin and to sinter the piezoelectric material; Arranging the piezoelectric ceramic plates parallel to the mold at a predetermined interval, and filling and curing a polymer resin matrix between the piezoelectric ceramic plates to obtain a piezoelectric ceramic-polymer composite having a 2-2 structure, and Forming external electrode layers on the top and one side and the bottom and the other side of the piezoelectric ceramic-polymer composite. A method of manufacturing a piezoelectric ceramic-polymer composite having a 2-2 structure consisting of multiple layers. The method of claim 13, The piezoelectric material of the piezoelectric layer is a piezoelectric ceramic-polymer composite having a 2-2 structure, characterized in that the PZN-PZT composite complex PZN and PZT. The method of claim 14, Wherein the internal electrode layer is formed of PZN-PZT / Ag which is a mixture of PZN-PZT composite and Ag. The method of claim 15, The content of Ag in the PZN-PZT / Ag is 30 to 80% by weight, the method of manufacturing a piezoelectric ceramic-polymer composite having a 2-2 structure. The method of claim 16, In the composition of the xPZN- (1-x) PZT composite used in the PZN-PZT / Ag internal electrode layer and / or the PZN-PZT piezoelectric layer, x is in a range of 0.1 to 0.6. Method for producing a piezoelectric ceramic-polymer composite of the.

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