Design and fabrication of piezoelectric composites and transducers for (1-0)-3 and (2-0)-2

Abstract

The application discloses a design and preparation method of (1-0)-3 and (2-0)-2 piezoelectric composite materials and transducers. The method is used for reducing apparent rigidity and gravity density of piezoelectric unit material by constructing micropores in the piezoelectric unit and filling flexible polymers to form (1-0) or (2-0) piezoelectric units; then a plurality of piezoelectric units are arranged according to a certain array and then flexible polymers are poured to form (1-0)-3 or (2-0)-2 piezoelectric composite materials by polishing upper and lower surfaces or polishing two side surfaces, evaporating electrodes and re-polarizing; metal copper blocks are adhered to upper and lower surfaces of the composite materials to perform subsequent acoustic or ultrasonic transducer performance tests. Under the same voltage excitation, the (1-0)-3 and (2-0)-2 piezoelectric composite materials of the application have larger vibration amplitudes and enhanced acoustic emission performance; under the same ultrasonic wave radiation, the (1-0)-3 and (2-0)-2 piezoelectric composites of the application have higher acoustic signal receiving sensitivity due to the enhanced piezoelectric voltage constant g value.

Description

Technical Field

[0001] This invention relates to piezoelectric composite materials and devices, specifically to acoustic and ultrasonic transducers, and methods and techniques for improving the sensitivity of acoustic and ultrasonic transducers and preparing novel piezoelectric composite materials. Background Technology

[0002] Acoustic and ultrasonic transducers are fundamental technologies in modern industry, medicine, and national defense, and are widely used in daily life and production. Piezoelectric and ultrasonic transducers utilize the piezoelectric effect to convert electroacoustic energy into electrical energy. They can convert electrical signals into sound waves that propagate through media such as water, the human body, or air, and vice versa, enabling target identification and information acquisition within a medium. The transducer's transmission and reception performance is a key factor limiting the detection range and target identification accuracy of acoustic information within a medium. Enhancing the transmission and reception sensitivity of acoustic and ultrasonic transducers allows for better acquisition of acoustic information from a medium, which is of great significance in various acoustic and ultrasonic applications. In the medical and health field, high-resolution imaging of human tissues and organs is required. Many other fields also rely heavily on advanced acoustic and ultrasonic technologies.

[0003] Traditionally, high-frequency ultrasonic transducers utilize piezoelectric ceramic (or single-crystal) rods and ceramic (or single-crystal) sheets, cast with flexible polymers such as epoxy resin to form 1-3 or 2-2 type piezoelectric composite materials to achieve a high piezoelectric sensitivity coefficient g. The appropriate addition of flexible polymers does indeed improve the acoustic receiving sensitivity of ultrasonic transducers. However, the improvement effect of flexible polymers on ultrasonic transducers is limited. Excessive addition of flexible polymers significantly reduces the piezoelectric strain coefficient d of the piezoelectric composite material, which in turn leads to a sharp decrease in the piezoelectric (force-electric) voltage coefficient g. This is because the compliance and acoustic impedance of the piezoelectric rod and sheet units themselves remain unchanged; simply increasing the flexible polymer to further improve the piezoelectric voltage coefficient g of the transducer has reached a bottleneck. Overcoming this bottleneck is a major challenge in the field of acoustic and ultrasonic transducers. Summary of the Invention

[0004] To address the aforementioned challenges, this invention proposes a method to enhance the piezoelectric voltage coefficient g of piezoelectric composite materials and transducers by improving the structure of the piezoelectric rods and piezoelectric sheet units themselves. The researchers of this invention have noted that piezoelectric single crystals and piezoelectric ceramics are high-stiffness, high-density solid materials, exhibiting a severe mismatch in acoustic impedance with media such as water and air. Traditional 1-3 and 2-2 type composites of piezoelectric ceramics and single crystals with epoxy resin do not actually alter the inherent high stiffness and high-density properties of the piezoelectric ceramics and single crystals themselves. Therefore, this invention first reduces the apparent stiffness and gravitational density of piezoelectric ceramics and single-crystal materials by constructing a microporous array inside piezoelectric ceramics and single-crystal materials and then filling them with flexible polymers such as epoxy resin to form (1-0) type composite rod piezoelectric units and (2-0) type composite plate piezoelectric units. Then, multiple composite rod units and composite plate units are arranged in a certain array and filled with flexible polymers such as epoxy resin to form (1-0)-3 type and (2-0)-2 type piezoelectric composite materials. Finally, the required acoustic transducer or ultrasonic transducer and array are prepared by cutting, preparing electrodes, and repolarizing.

[0005] This method of preparing piezoelectric composite materials by designing a microporous array inside the piezoelectric unit, filling it with flexible polymers such as epoxy resin, and then arranging the piezoelectric units in an array and casting the flexible polymers, has many advantages. In terms of emission sensitivity, due to the reduced apparent stiffness (more compliant) and lighter weight of the piezoelectric composite rod and plate units, the vibration amplitude of these novel (1-0)-3 and (2-0)-2 type piezoelectric composite materials increases under the same voltage excitation, thereby improving the acoustic emission performance of the transducer. Furthermore, the microporous structure inside the piezoelectric unit is filled with flexible polymers such as epoxy resin. Since the density of these flexible polymers is much lower than that of the piezoelectric material, the acoustic impedance of these novel (1-0)-3 and (2-0)-2 type piezoelectric composite materials is reduced, resulting in a better match with the acoustic impedance of water and facilitating the reception of sound signals. Regarding receiving sensitivity, the microporous structure filled with flexible polymers such as epoxy resin reduces the equivalent dielectric constant of the piezoelectric unit itself, and also decreases the dielectric constant of the (1-0)-3 and (2-0)-2 type piezoelectric composite materials; while their piezoelectric strain coefficient d-value remains basically unchanged, it can also significantly improve the piezoelectric voltage coefficient g-value of the piezoelectric composite material. Therefore, the novel piezoelectric composite material of this invention has a high piezoelectric voltage coefficient g-value and a more matched acoustic impedance, which will undoubtedly enhance the acoustic wave receiving sensitivity of the piezoelectric composite acoustic transducer.

[0006] The receiving sensitivity of acoustic and ultrasonic transducers made from traditional 1-3 piezoelectric composite materials is closely related to the overall piezoelectric voltage coefficient g of the composite material. Generally, there are two methods to improve the overall piezoelectric voltage coefficient of 1-3 piezoelectric composite materials: one is to select piezoelectric materials with relatively high piezoelectric voltage coefficients, and the other is to optimize the percentage of flexible polymers (such as epoxy resin) in the 1-3 piezoelectric composite material to increase the overall piezoelectric voltage coefficient. However, both methods face a bottleneck. This invention further improves the piezoelectric voltage coefficient g of the piezoelectric composite material by designing uniformly or non-uniformly distributed micropore arrays within the piezoelectric material according to the sensitivity requirements of the sensitive parts, constructing (1-0) type composite rod piezoelectric units or (2-0) type composite plate piezoelectric units, and then constructing (1-0)-3 type or (2-0)-2 type array structures.

[0007] The (1-0) type composite rod piezoelectric unit and the (2-0) type composite plate piezoelectric unit have one or more micropores filled with flexible polymer, and the diameter of the micropores is preferably 0.05 to 1.0 mm.

[0008] Figure 1 This demonstrates the design concept proposed in this invention. Figure 1 (a) shows a (1-0) type piezoelectric unit, (b) shows a (1-0)-3 type array piezoelectric composite material, (c) shows a (2-0) type piezoelectric unit, and (d) shows a (2-0)-2 type array piezoelectric composite material.

[0009] In this invention, electrodes are plated on two opposing surfaces of the (1-0) type piezoelectric unit and the (2-0) type piezoelectric unit along their polarization direction. For example... Figure 2 The electrode designs of the (1-0)-3 and (2-0)-2 type piezoelectric composite material units are shown, wherein: (a) is the electrode design of the (1-0) type piezoelectric unit with micropores, (b) is the electrode design of the (1-0)-3 type piezoelectric composite material array, (c) is the electrode design of the (2-0) type piezoelectric unit with micropores, and (d) is the electrode design of the (2-0)-2 type piezoelectric composite material array. Figure 2 In the (1-0) and (2-0) type piezoelectric units, a pair of electrodes, either vertically or horizontally offset, are plated on two opposite sides (i.e., two opposite surfaces along the x-axis thickness direction), and the piezoelectric unit is polarized along the thickness (x-axis) direction. This offset design of the two side electrodes facilitates the extraction of the side electrodes after the subsequent piezoelectric unit array assembly. Tests show that the piezoelectric unit operates in d... 32 (or d) 31 The transverse vibration mode exhibits strong electromechanical coupling. Compared to d... 33 Operating modes (longitudinal vibration modes), based on d 32 (or d)31 Under the same voltage excitation, the end displacement of the modal piezoelectric element is greater, see... Figure 3 Therefore, using d 32 (or d) 31 The (1-0)-3 and (2-0)-2 type piezoelectric composite material transducers constructed with modal piezoelectric units are expected to have higher acoustic emission capabilities.

[0010] In this invention, the (1-0) type piezoelectric unit and the (2-0) type piezoelectric unit can also operate in d 33 The operating mode is advantageous for achieving higher acoustic wave receiving sensitivity. In this case, a pair of electrodes are plated on the upper and lower opposing surfaces (rather than the sides) of the piezoelectric unit, and the piezoelectric unit is polarized along the z-axis. This design can utilize the traditional 1-3 and 2-2 composite material preparation processes and methods.

[0011] This invention also provides d 32 (or d) 31 The preparation methods of modal (1-0)-3 and (2-0)-2 piezoelectric composite materials and transducers are as follows:

[0012] 1) Select piezoelectric ceramics and single crystal materials with high voltage electrical properties and electromechanical coupling, and prepare them into uniform sheet structures using a high-precision dicing machine;

[0013] 2) Prepare Ag electrodes or other highly conductive metal electrodes such as Au by misaligning the upper and lower surfaces of the sheet-like piezoelectric material;

[0014] 3) High-voltage polarization of the prepared piezoelectric sheet along the thickness direction: For piezoelectric ceramic sheets, the sample should be placed in silicone oil (temperature set to 120℃) for polarization, and the polarization electric field strength is set to the range of 2.0-3.5kV / cm; for piezoelectric single crystals, the polarization electric field strength is set to the range of 0.30-1.0kV / cm.

[0015] 4) After polarization, the piezoelectric sheet is designed with a uniformly or non-uniformly distributed micropore array according to the sensitivity requirements of the sensitive parts. The micropores are prepared by ultrasonic drilling or etching, preferably with a diameter of 0.05-1.0 mm. Flexible polymer (such as epoxy resin) is injected into the micropores. The micropores are then cut into the required uniform size to obtain thin rod-shaped (1-0) type or plate-shaped (2-0) type piezoelectric ceramic units or piezoelectric single crystal units.

[0016] 5) Based on the required piezoelectric unit array of the piezoelectric composite material, a flexible polymer (such as epoxy resin) mold framework is prepared using machining, injection molding, or 3D printing methods for the assembly of the piezoelectric units. For example... Figure 4 As shown.

[0017] 6) Insert (1-0) type or (2-0) type piezoelectric ceramics or piezoelectric single crystal units into the flexible polymer framework; during the assembly process, the flexible polymer and curing agent can be mixed by ultrasonic stirring to remove air bubbles; then pour the mixed flexible polymer into the framework with the piezoelectric unit array inserted.

[0018] 7) Place the sample obtained in step 6) into a vacuum pump to remove bubbles again; let it stand and cure at room temperature (usually 24 hours) and then take out the sample. Polish the upper and lower surfaces or two sides of the obtained sample. For example, first use 600 grit sandpaper for rough polishing, and then use 1200 grit sandpaper for fine polishing.

[0019] 8) After cleaning the polished upper and lower surfaces or two sides with alcohol, deposit gold or other electrodes by vapor deposition, and lead out the electrodes prepared by misalignment in step 2) to form a (1-0)-3 type or (2-0)-2 type piezoelectric composite material; then perform relevant electrical tests and characterization.

[0020] 9) After the samples obtained in step 8) have completed the relevant tests, copper blocks can be attached to the upper and lower surfaces of the (1-0)-3 or (2-0)-2 type piezoelectric composite material for subsequent acoustic transducer or ultrasonic transducer performance tests.

[0021] The (1-0) type composite rod piezoelectric unit and (2-0) type composite plate piezoelectric unit in the transducer provided by this invention can operate in d 31 or d 32 Transverse vibration modes, and can also operate in d 33 The preparation method of the piezoelectric composite material and transducer for the longitudinal vibration mode is the same as that of the conventional method, and will not be repeated here. Furthermore, the (1-0)-3 type or (2-0)-2 type piezoelectric composite material and transducer of the present invention can be extended to d... 15 Shear vibration modes, as well as other artificially designed modes, such as bending modes and torsional modes. The (1-0)-3 and (2-0)-2 type piezoelectric composite materials with microporous structures that operate in these piezoelectric vibration modes are suitable for applications such as underwater acoustic transducers, ultrasonic and medical ultrasonic transducers, and air transducers.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] (1) Since the mass of each piezoelectric unit in the (1-0)-3 type and (2-0)-2 type piezoelectric composite material is lighter, the vibration amplitude of the piezoelectric material will be larger under the same voltage excitation, thereby improving the acoustic emission performance of its acoustic transducer.

[0024] (2) In addition, the piezoelectric unit in this invention is filled with a flexible polymer (such as epoxy resin) due to its microporous structure. Since the flexible polymer has a very low density, the acoustic impedance of each piezoelectric unit will be reduced. This will make the transducer made of (1-0)-3 type and (2-0)-2 type composite piezoelectric material more matched with the acoustic impedance of water at its radiating end, which is beneficial for receiving sound wave signals and improving the receiving sensitivity.

[0025] (3) The microporous structure of the piezoelectric unit is filled with a flexible polymer (such as epoxy resin), which reduces the effective dielectric constant of the piezoelectric unit and thus reduces the dielectric constant ε of the (1-0) type and (2-0) type piezoelectric units; while the strain coefficient d of the piezoelectric unit remains basically unchanged, thereby increasing the piezoelectric voltage constant g (=d / ε) value related to the receiving sensitivity of the piezoelectric unit.

[0026] (4) When receiving acoustic radiation, the piezoelectric unit with microporous structure will produce a local micro-stress concentration effect in the porous part of the piezoelectric material from a mechanical point of view, thus producing a larger piezoelectric response, which helps to improve the sensitivity of the piezoelectric unit to acoustic waves and ultrasonic waves.

[0027] (5) Given a piezoelectric material, conventional methods rely on optimizing epoxy resin or other organic polymers, as well as optimizing the ratio of epoxy resin to piezoelectric units, to improve the piezoelectric voltage coefficient. Similarly, given a piezoelectric material, the piezoelectric unit micropores proposed in this invention, and the flexible polymer structure (1-0) and (2-0) type piezoelectric units constructed by casting epoxy resin and other polymers, make the piezoelectric units themselves more flexible; furthermore, by re-casting flexible polymers such as epoxy resin into the (1-0)-3 and (2-0)-2 type piezoelectric composite materials through the (1-0)-3 and (2-0)-2 type piezoelectric unit arrays, the piezoelectric composite material of this invention has a higher piezoelectric voltage coefficient g. Attached Figure Description

[0028] Figure 1 The present invention includes (1-0)-3 and (2-0)-2 type piezoelectric units and their piezoelectric composite materials, wherein: (a) is the structure of a (1-0) type piezoelectric unit with micropores, (b) is a schematic diagram of the (1-0)-3 type piezoelectric composite material structure constructed by an array of (1-0) type piezoelectric units, (c) is the structure of a (2-0) type piezoelectric unit with micropores, and (d) is a schematic diagram of the (2-0)-2 type piezoelectric composite material structure constructed by an array of (2-0) type piezoelectric units.

[0029] Figure 2The present invention provides designs for (1-0)-3 and (2-0)-2 type piezoelectric composite material unit electrodes, wherein: (a) is a (1-0) type piezoelectric unit electrode design with micropores, (b) is a (1-0)-3 type piezoelectric composite material array electrode design, (c) is a (2-0) type piezoelectric unit electrode design with micropores, and (d) is a (2-0)-2 type piezoelectric composite material array electrode design.

[0030] Figure 3 For piezoelectric elements of the same material and size, under the same voltage excitation, d 32 (or d) 31 Modal vibration displacement diagram, and d 33 Modal vibration displacement diagram.

[0031] Figure 4 An epoxy resin mold framework for preparing (1-0)-3 type piezoelectric composite materials.

[0032] Figure 5 Finite element simulations were performed at 10V to measure the emission voltage response (TVR) and total radiated power of (1-0) type piezoelectric unit samples with and without holes, ranging from 400kHz to 700kHz, where the hole diameter was 0.1mm.

[0033] Figure 6 The displacement responses of piezoelectric units with different numbers of holes (1-0) under AC excitation of 100V peak-to-peak at 1kHz are shown, where: (a) is the displacement response of a sample without holes, (b) is the displacement response of a sample with 2 holes, (c) is the displacement response of a sample with 3 holes, (d) is the displacement response of a sample with 5 holes, and (e) is the peak-to-peak value of the displacement response of samples with different numbers of holes; the hole diameter is set to 0.6mm for all samples.

[0034] Figure 7 To verify the receiving effect of the (1-0)-3 type piezoelectric composite material as an ultrasonic transducer, different samples were placed at the center of an ultrasonic cleaner filled with water (frequency 28kHz) to test the ultrasonic voltage response. Among them, (a) is the output voltage waveform of the sample without holes, (b) is the output voltage waveform of the sample with 2 holes, (c) is the output voltage waveform of the sample with 3 holes, (d) is the output voltage waveform of the sample with 5 holes, and (e) is the peak-to-peak value of the output voltage of the sample with different numbers of holes. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings and embodiments, but the scope of the invention is not limited in any way.

[0036] like Figure 1As shown, (a) presents a (1-0) type piezoelectric unit structure with microporous structure, and (b) presents a (1-0)-3 type piezoelectric composite material and ultrasonic transducer constructed based on a (1-0) type piezoelectric unit array, serving as one application example to verify the design concept proposed in this invention. In this invention, electrodes are plated on two sides (i.e., two opposing surfaces in the thickness direction) of the piezoelectric unit instead of the top and bottom surfaces, and the polarization direction of the piezoelectric unit is also in the thickness direction. This prepares for the subsequent fabrication of the piezoelectric unit composite transducer, because the piezoelectric unit operates in the d... 32 The modes exhibit a strong electromechanical coupling coefficient.

[0037] Figure 3 Finite element simulations are presented. The finite element simulation results show that, under the same voltage excitation, compared to d... 33 Operating modes, including microporous structure (1-0) type piezoelectric unit based on d 32 The modal has a larger end displacement. Therefore, using d 32 The (1-0)-3 type composite material transducer constructed with modal piezoelectric units has better emission performance.

[0038] d is prepared according to the following method 32 Modal (1-0)-3 type piezoelectric composite material and transducer:

[0039] 1) Select piezoelectric ceramics with high voltage and electromechanical coupling, and prepare them into uniform sheet structures using a high-precision dicing machine;

[0040] 2) Ag electrodes are prepared on the upper and lower surfaces of the sheet-like piezoelectric material;

[0041] 3) High-voltage polarization is performed on the piezoelectric sheet prepared in step 2) along the thickness direction: For piezoelectric ceramic sheets, the sample should be placed in silicone oil (temperature set to 120℃) for polarization, and the polarization electric field strength is set to the range of 2.0-3.5kV / cm; for piezoelectric single crystal wafers, the polarization electric field strength is set to the range of 0.30-1.0kV / cm.

[0042] 4) After polarization, the piezoelectric sheet is designed with a uniformly or non-uniformly distributed micropore array according to the sensitivity requirements of the sensitive parts. Micropores with a diameter of 0.06 mm are prepared using methods such as ultrasonic drilling or etching, and epoxy resin is injected. Then, it is cut to the required uniform size to obtain (1-0) type piezoelectric ceramics or piezoelectric single crystal units, such as... Figure 1 As shown in (a);

[0043] 5) Based on the required piezoelectric unit array of the piezoelectric composite material, prepare it using machining, injection molding, or 3D printing methods, such as... Figure 4 The epoxy resin mold frame shown is used for assembling the piezoelectric unit;

[0044] 6) Insert the (1-0) type piezoelectric ceramic unit into the epoxy resin frame; during the assembly process, mix the epoxy resin and curing agent by ultrasonic stirring and remove air bubbles, and then pour the mixed epoxy resin into the frame with the piezoelectric unit array inserted.

[0045] 7) Place the sample obtained in step 6) into a vacuum pump to remove bubbles again; after placing it at room temperature for 24 hours, take out the sample and polish the upper and lower surfaces of the obtained sample: first use 600 grit sandpaper for rough polishing, and then use 1200 grit sandpaper for fine polishing.

[0046] 8) After cleaning the polished upper and lower surfaces with alcohol, gold electrodes are deposited to form a (1-0)-3 type piezoelectric composite material; then relevant electrical tests are performed to characterize it.

[0047] 9) After the sample obtained in step 8) has completed the relevant tests, copper blocks are attached to the upper and lower surfaces of the (1-0)-3 type piezoelectric composite material for subsequent ultrasonic transducer performance tests.

[0048] Figure 4 An epoxy resin mold framework is presented. Based on the (1-0) type piezoelectric unit array required for the piezoelectric composite material, an epoxy resin mold framework is prepared using machining, injection molding, or 3D printing methods for direct insertion of the piezoelectric units. Then, the (1-0)-3 type piezoelectric composite material and transducer are constructed by casting epoxy resin. Precise insertion holes facilitate the parallel placement of the piezoelectric units, thereby promoting parallel longitudinal vibration and parallel longitudinal wave emission from each unit of the piezoelectric composite material.

[0049] Through standard piezoelectric d 33 The testing instrument can directly test the apparent piezoelectric coefficient d of (1-0) type piezoelectric units containing different numbers of micropores. eff The impedance analyzer was used to test the capacitance Cp and dielectric constant ε, and the density was tested using the water displacement method. The test results are shown in the table below:

[0050] <![CDATA[d eff ]]> 2980 2910 2853 2848 <![CDATA[C p (nF)]]> 18.53 17.59 17.1 16.5 <![CDATA[ε r,eff ]]> 189 179.4 174.42 168.3 <![CDATA[g eff ]]> 178.1 183 185 191 mass g 5.59 5.574 5.41 5.426 <![CDATA[density (g / cm 3 )]]> 3.169 3.135 3.067 3.028

[0051] The capacitance of the (1-0) type piezoelectric unit decreases with the increase of the number of holes. It can be verified that the overall dielectric constant of the constructed (1-0)-3 type piezoelectric composite material also decreases with the increase of the number of micropores, but the piezoelectric coefficient d remains almost unchanged, thereby improving the overall effective piezoelectric voltage coefficient g.

[0052] Figure 5The finite element simulation results of the (1-0) type piezoelectric element are shown: under 10V excitation and in the frequency range of 400-700kHz, the transmission voltage response (TVR) (the ratio of sound pressure to applied voltage at a distance of 1m from the transducer) and total radiated power as a function of frequency are presented for the (1-0) type piezoelectric element with three holes and the piezoelectric element without holes. The simulation results show that the (1-0)-3 type piezoelectric composite material with microporous structure improves both the transmission and reception performance of the ultrasonic transducer, verifying the idea proposed in this invention.

[0053] Figure 6 The displacement response of (1-0)-3 piezoelectric composite materials with different numbers of holes used as acoustic transducers under AC excitation of 1kHz and peak-to-peak value of 100V was analyzed. It can be seen that, under the same voltage, the emission performance of the (1-0)-3 piezoelectric composite material transducer first increases and then decreases with increasing number of holes. This verifies that the (1-0)-3 piezoelectric composite material with a microporous structure helps improve emission performance in ultrasonic transducers, while an excessive number of holes will degrade its performance. Too many holes may damage the material internally and affect emission performance.

[0054] Figure 7 The ultrasonic receiving performance of (1-0)-3 piezoelectric composite materials with different numbers of pores as ultrasonic transducers was verified. Different samples were placed at the center of an ultrasonic cleaner filled with water, and the output voltage was measured. Under the same power of ultrasonic radiation, the output voltage of the (1-0)-3 piezoelectric composite material can be used to measure its receiving sensitivity performance as an ultrasonic transducer; the composite material with three pores exhibited the highest peak-to-peak output voltage. This also verifies that the microporous structure of the (1-0)-3 piezoelectric composite material contributes to improved receiving performance in ultrasonic transducers.

[0055] The above examples use (1-0) type piezoelectric units and (1-0)-3 type piezoelectric composite materials as embodiments to illustrate the concept of the present invention. The same inventive concept can be applied to the (2-0) type piezoelectric units and (2-0)-2 type piezoelectric composite material embodiments.

[0056] Finally, it should be noted that the purpose of disclosing the embodiments is to help further understand the present invention. However, those skilled in the art will understand that various substitutions and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the present invention should not be limited to the content disclosed in the embodiments, and the scope of protection of the present invention is defined by the claims.

Claims

1. A piezoelectric composite material, comprising a plurality of (1-0) or (2-0) type piezoelectric units arranged in a certain array and filled with a flexible polymer, wherein the (1-0) type or (2-0) type piezoelectric units are internally provided with micropores and filled with a flexible polymer; characterized in that, The (1-0) type piezoelectric unit is a composite rod piezoelectric unit formed by constructing micropores inside piezoelectric ceramics or piezoelectric single crystal materials and filling them with flexible polymers. The (2-0) type piezoelectric unit is a composite plate piezoelectric unit formed by constructing micropores inside piezoelectric ceramics or piezoelectric single crystal materials and filling them with flexible polymers.

2. The piezoelectric composite material as described in claim 1, characterized in that, The diameter of the micropores is 0.05~1.0 mm.

3. The piezoelectric composite material as described in claim 1, characterized in that, The flexible polymer is epoxy resin.

4. An acoustic transducer, prepared from the (1-0)-3 type or (2-0)-2 type piezoelectric composite material as described in any one of claims 1 to 3, wherein the (1-0) type or (2-0) type piezoelectric unit constituting the (1-0)-3 type or (2-0)-2 type piezoelectric composite material operates at d 32 or d 31 Modality, or d 33 Modality.

5. The acoustic transducer as described in claim 4, characterized in that, The (1-0) or (2-0) type piezoelectric unit has electrodes plated on its two opposite sides, i.e., two opposite surfaces in the thickness direction, and the polarization direction of the piezoelectric unit is also in the thickness direction; the piezoelectric unit operates in d 32 or d 31 Transverse vibration modes.

6. The acoustic transducer as described in claim 4, characterized in that, The (1-0) or (2-0) type piezoelectric unit has electrodes plated on both its upper and lower end surfaces, and the polarization direction of the piezoelectric unit is along the longitudinal direction; the piezoelectric unit operates in d 33 Longitudinal vibration modes.

7. A method for preparing a piezoelectric composite material, wherein the piezoelectric composite material is d 32 or d 31 Modal (1-0)-3 or (2-0)-2 type piezoelectric composite materials, comprising the following steps: 1) Cut piezoelectric ceramics or piezoelectric single crystal materials into uniform sheet-like structures; 2) Electrodes are fabricated by misaligning the upper and lower surfaces of the sheet-like piezoelectric material prepared in step 1); 3) Polarize the piezoelectric sheet prepared in step 2) along the thickness direction; 4) Design a uniformly or non-uniformly distributed array of micropores on the polarized piezoelectric sheet, then drill holes and inject flexible polymer, and then cut the piezoelectric sheet into (1-0) type or (2-0) type piezoelectric units of uniform size; 5) Prepare a flexible polymer mold framework based on the piezoelectric unit array required by the piezoelectric composite material for the assembly of the piezoelectric units; 6) Insert the (1-0) type or (2-0) type piezoelectric unit into the flexible polymer frame, and then pour in the mixed flexible polymer and curing agent; 7) Remove air bubbles from the poured flexible polymer by vacuuming, and polish the upper and lower surfaces or two sides of the sample after allowing it to cure at room temperature. 8) Clean and polish the upper and lower surfaces or both sides and then deposit electrodes. Lead out the electrodes prepared by misalignment in step 2) to obtain (1-0)-3 type or (2-0)-2 type piezoelectric composite material.

8. The preparation method according to claim 7, characterized in that, The flexible polymer is epoxy resin.

9. The preparation method according to claim 7, characterized in that, The diameter of the micropores is 0.05~1.0 mm.

10. The preparation method according to claim 7, characterized in that, In step 3), for the piezoelectric ceramic sheet, it is placed in silicone oil for polarization, and the polarization electric field strength is set to 2.0-3.5 kV / cm; for the piezoelectric single crystal, the polarization electric field strength is set to 0.30-1.0 kV / cm.

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