Apparatus and method for ac poling a 2-2 piezoelectric composite

Abstract

An alternating current polarization device and method for 2-2 type piezoelectric composite material, the device comprises a voltage amplifier connected with an oscilloscope and a function generator, the voltage amplifier is connected with upper and lower electrodes of the 2-2 type piezoelectric composite material, and the 2-2 type piezoelectric composite material is immersed in silicon oil; the method is to prepare the 2-2 type piezoelectric composite material first, and prepare electrodes on opposite surfaces in the thickness direction of the 2-2 type piezoelectric composite material; then the 2-2 type piezoelectric composite material is placed into the alternating current polarization device, and it is ensured that the upper and lower electrodes are in good contact with the 2-2 type piezoelectric composite material; then the function generator is used to generate alternating current voltage with a symmetrical triangular wave, the voltage amplifier is used to amplify the voltage signal and apply to the 2-2 type piezoelectric composite material, the peak voltage, polarization frequency and polarization circle number of the alternating current voltage are set, and the 2-2 type piezoelectric composite material is polarized; after polarization is completed, the 2-2 type piezoelectric composite material is taken out; the whole piezoelectric and dielectric performance of the 2-2 type piezoelectric composite material is improved through the alternating current polarization mode, the procedure is simple, the time is short, and it is safe.

Description

Technical Field

[0001] This invention relates to the field of polarization technology for 2-2 type piezoelectric composite materials, and specifically to an AC polarization device and method for 2-2 type piezoelectric composite materials. Background Technology

[0002] Piezoelectric composites are composite materials formed by a piezoelectric phase composed of piezoelectric materials and a polymer phase composed of epoxy resin or other polymers, with a certain interconnected structure. Two-phase composites consist of two phases, while three-phase composites also exist. Two-phase composites can be further classified according to the different interconnection methods, with the most widely used being type 1-3 and type 2-2 piezoelectric composites. The interconnection method determines the electric field path and stress distribution in the composite material, which is influenced by the different spatial distributions of the two phases. In two-phase piezoelectric composites, the first number generally represents the interconnection of the piezoelectric phase, and the second number represents the interconnection of the polymer phase. 1 represents one-dimensional interconnection, i.e., interconnection in only one direction, generally linear; 2 represents interconnection in two directions, generally sheet-like; and 3 represents three-dimensional interconnection, generally continuous in all three directions.

[0003] The main performance advantages of type 2-2 piezoelectric composite materials in transducer fabrication are as follows: low acoustic impedance Z and low quality factor Q. m Value, good flexibility, high hydrostatic pressure and acoustic performance value d h ·g h With its weak lateral coupling, good controllability of piezoelectric phase distribution, and good temperature and pressure stability, the 2-2 type piezoelectric composite material is very suitable for the field of transducers. Therefore, it has been widely used and studied.

[0004] The polarization process is a key step in obtaining piezoelectric properties from piezoelectric materials. Currently, the only polarization method for 2-2 type piezoelectric composites is DC polarization. There are usually two DC polarization methods for 2-2 type piezoelectric composites: 1. Prepare the unpolarized piezoelectric material into a 2-2 type piezoelectric composite and then perform DC polarization (Wang W, Or SW, Yue Q, et al. Ternary piezoelectric single-crystal PIMNT based 2-2composite for ultrasonic transducer applications[J]. Sensors and Actuators a-Physical, 2013, 196:70.); 2. First perform DC polarization on the piezoelectric material, then prepare it into a 2-2 type piezoelectric composite and then prepare electrodes for secondary DC polarization (Xin F, Chen W. Research on Fabrication and Properties of 2-2PZT / Epoxy Piezoelectric Composite Materials[J]. Piezoelectrics and Acoustooptics, 2015, 37(4):646.). However, the aforementioned prior art has the following drawbacks:

[0005] 1) When DC polarizing piezoelectric materials to prepare 2-2 type piezoelectric composites, depolarization is prone to occur, and the effect after secondary DC polarization is not good, and it cannot effectively improve the piezoelectric and dielectric properties of the composite material; 2) When DC polarizing 2-2 type piezoelectric composites, continuous DC high voltage can easily break down the composite material; 3) When DC polarizing 2-2 type piezoelectric composites, the polarization time is generally 15-30 minutes, and secondary polarization takes twice as long, which is time-consuming and complicated; 4) Continuous DC high voltage polarization of samples and manual voltage increase pose certain safety risks. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the present invention aims to provide an AC polarization device and method for 2-2 type piezoelectric composite materials, which improves the overall piezoelectric and dielectric properties of 2-2 type piezoelectric composite materials through AC polarization. The procedure is simple, quick, and safe.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] An AC polarization device for a 2-2 type piezoelectric composite material includes a voltage amplifier connected to an oscilloscope and a function generator. The voltage amplifier is connected to the upper and lower electrodes of the 2-2 type piezoelectric composite material, which is immersed in silicone oil.

[0009] The contacts of the upper and lower electrodes of the 2-2 type piezoelectric composite material are located at the center of the 2-2 type piezoelectric composite material.

[0010] A method using an AC polarization device for a type 2-2 piezoelectric composite material includes the following steps:

[0011] Step 1: Prepare a 2-2 type piezoelectric composite material, and fabricate electrodes on opposite surfaces in the thickness direction of the 2-2 type piezoelectric composite material;

[0012] Step 2: Place the 2-2 type piezoelectric composite material prepared in Step 1 into an AC polarization device, ensuring good contact between the upper and lower electrodes and the 2-2 type piezoelectric composite material, and immerse the entire 2-2 type piezoelectric composite material in silicone oil at room temperature;

[0013] Step 3: Generate an AC voltage with a symmetrical triangular wave using a function generator, amplify the voltage signal using a voltage amplifier, and apply it to the 2-2 type piezoelectric composite material. Set the peak voltage, polarization frequency, and number of polarization cycles of the AC voltage and polarize the 2-2 type piezoelectric composite material. The peak voltage is proportional to the thickness of the 2-2 type piezoelectric composite material.

[0014] Step 4: After polarization is complete, wait for the voltage to return to zero, remove the 2-2 type piezoelectric composite material, clean the silicone oil on the surface of the 2-2 type piezoelectric composite material, and measure the properties of the 2-2 type piezoelectric composite material.

[0015] The AC polarization condition parameters in step 3 include: peak voltage of 0.8-1.5kV / mm, polarization frequency of 0.08-10Hz, and number of polarization cycles of 5-20.

[0016] The beneficial effects of this invention are as follows:

[0017] 1) This invention provides another effective polarization method for 2-2 type piezoelectric composite materials. AC polarization of 2-2 type piezoelectric composite materials can effectively improve their piezoelectric properties. 33 When the 2-2 type piezoelectric composite material is applied to devices such as underwater acoustic transducers, it is beneficial to expand the bandwidth and improve the resolution and other performance parameters of the transducer.

[0018] 2) Compared to the DC polarization followed by a secondary DC polarization of the 2-2 type piezoelectric composite material, the AC polarization method proposed in this invention simplifies the polarization process of the 2-2 type piezoelectric composite material and shortens the polarization time; it also eliminates the need for manual voltage boosting, ensuring safety.

[0019] 3) The AC polarization method of the present invention can successfully polarize the 2-2 type piezoelectric composite material, ensuring that the 2-2 type piezoelectric composite material can be well used in piezoelectric devices such as ultrasonic transducers, and increasing market compatibility.

[0020] 4) The spontaneous polarization vector sum of piezoelectric materials before polarization is zero, and they have no piezoelectricity; at room temperature and Curie temperature T C Applying an electric field can make the sum of the polarized dipole vectors inside the crystal greater than zero along the direction of the electric field, thus giving it piezoelectric properties. Therefore, for a long time, people have only used DC polarization with a fixed electric field direction to polarize 2-2 type composite materials. AC polarization with a constantly changing electric field direction has only been applied to the performance optimization of pure piezoelectric materials. The AC polarization method has not yet been applied to 2-2 type piezoelectric composite materials with both polymer and piezoelectric phases to verify the improvement of the overall performance of the composite material. Therefore, this invention overcomes the inertia of the prior art, fills the gap in this technical field, and produces unexpected technical effects. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the device structure according to an embodiment of the present invention.

[0022] Figure 2 This is a schematic diagram of the 2-2 type piezoelectric composite material prepared according to an embodiment of the present invention.

[0023] Figure 3 The waveform of the AC voltage applied to the piezoelectric composite material of Embodiment 2-2 of the present invention.

[0024] Figure 4 The piezoelectric strain constant d of the 2-2 type piezoelectric composite material after AC polarization and DC polarization in Example 1 is... 33 Comparison chart.

[0025] Figure 5 The piezoelectric strain constant d of the 2-2 type piezoelectric composite material after AC polarization and DC polarization in Example 2 is... 33 Comparison chart.

[0026] Figure 6 The piezoelectric strain constant d of the 2-2 type piezoelectric composite material after AC polarization and DC polarization in Example 3 is... 33 Comparison chart. Detailed Implementation

[0027] The present invention will be further described below with reference to the following embodiments and accompanying drawings.

[0028] Reference Figure 1An AC polarization device for a 2-2 type piezoelectric composite material includes a voltage amplifier connected to an oscilloscope and a function generator. The voltage amplifier is connected to the upper and lower electrodes of the 2-2 type piezoelectric composite material, which is immersed in silicone oil. The contacts of the upper and lower electrodes of the 2-2 type piezoelectric composite material are located at the center of the 2-2 type piezoelectric composite material. The function generator (DG1022, RIGOL) is used to generate the required waveform pulse, which is amplified by the voltage amplifier (PZD2000A, Trek) and applied to the 2-2 type piezoelectric composite material. The oscilloscope detects the applied pulse signal voltage.

[0029] This embodiment describes a method for obtaining a 2-2 type piezoelectric composite material with a PIN-PMN-PT single crystal piezoelectric phase through AC polarization using an AC polarization device. The method includes the following steps:

[0030] Step 1: Prepare a 2-2 type piezoelectric composite material and prepare electrodes on opposite surfaces in the thickness direction of the 2-2 type piezoelectric composite material to ensure that the surface of the 2-2 type piezoelectric composite material is flat and uniform, without cracks and impurities;

[0031] In this embodiment, a 2-2 type piezoelectric composite material was first prepared, with the piezoelectric phase being trigonal lead indium niobate-lead magnesium niobate-lead titanate (PIN-47%PMN-29%PT) and the polymer phase being Epo-Tek 301 epoxy resin. Electrodes were then fabricated, such as... Figure 2 As shown;

[0032] Step 2: Place the 2-2 type piezoelectric composite material prepared in Step 1 into an AC polarization device to ensure good contact between the upper and lower electrodes and the 2-2 type piezoelectric composite material. Immerse the entire 2-2 type piezoelectric composite material in silicone oil at room temperature for 3-5 minutes to enhance the electrode bonding strength and prevent breakdown.

[0033] Step 3: Generate an AC voltage with a symmetrical triangular wave using a function generator, as shown in the waveform below. Figure 3 As shown, a voltage amplifier is used to amplify the voltage signal and apply it to the 2-2 type piezoelectric composite material. The voltage peak value, polarization frequency and number of polarization cycles are set to polarize the 2-2 type piezoelectric composite material.

[0034] In this embodiment, the thickness of the piezoelectric composite material is 2mm, the peak voltage is set to 1kV / mm, the polarization frequency is 0.1Hz, and the number of polarization cycles is 8.

[0035] Step 4: After polarization is complete, wait for the voltage to return to zero, remove the 2-2 type piezoelectric composite material, clean the silicone oil on the surface of the 2-2 type piezoelectric composite material, and measure the properties of the 2-2 type piezoelectric composite material.

[0036] The beneficial effect of this embodiment is as follows: By preparing two sets of 2-2 type piezoelectric composite materials with the same structural parameters from the same PIN-PMN-PT piezoelectric single crystal material, one set was subjected to DC polarization and the other set was subjected to AC polarization as described above. It was found that the piezoelectric strain constant d of the 2-2 type piezoelectric composite material was higher under AC polarization than under DC polarization. 33 It can increase by an average of 34.5%, such as Figure 4 Table 1 shows a comparison of the piezoelectric properties of the 2-2 type piezoelectric composite material after AC polarization and DC polarization in Example 1. Moreover, the 2-2 type piezoelectric composite material treated by AC polarization can achieve a piezoelectric strain constant of up to 2000 pC / N, while the piezoelectric strain constant of the 2-2 type piezoelectric composite material with the same structural parameters prepared in the previous stage is generally 1200-1500 pC / N. Therefore, AC polarization is beneficial to improving the piezoelectric properties and electromechanical coupling properties of the 2-2 type piezoelectric single crystal composite material.

[0037] Table 1

[0038] <![CDATA[Q m ]]> <![CDATA[K t ]]> <![CDATA[d 33 (pC / N)]]> Z(Mrayl) DC polarization 16.87 0.79 1156.7 21.56 Exchange polarization 3.81 0.89 1556.4 21.42

[0039] Example 2: In Example 1, step 3, the peak voltage is changed to 0.8kV / mm, the polarization frequency is changed to 0.08Hz, and the number of polarization cycles is changed to 5.

[0040] The beneficial effect of this embodiment is as follows: Two sets of type 2 piezoelectric composite materials with the same structural parameters were prepared from the same PIN-PMN-PT piezoelectric single crystal material. One set was DC polarized, and the other was AC polarized. It was found that AC polarization resulted in a higher piezoelectric strain constant d of the type 2 piezoelectric composite material compared to DC polarization. 33 It can increase by an average of 29.3%, such as Figure 5 Table 2 shows the comparison of piezoelectric properties of the 2-2 type piezoelectric composite material after AC polarization and DC polarization in Example 2.

[0041] Table 2

[0042] <![CDATA[Q m ]]> <![CDATA[K t ]]> <![CDATA[d 33 (pC / N)]]> Z(Mrayl) DC polarization 17.06 0.81 1372.4 20.56 Exchange polarization 15.43 0.82 1774.2 19.42

[0043] Example 3: In Example 1, step 3, the peak voltage was changed to 1.5kV / mm, the polarization frequency was changed to 10Hz, and the number of polarization cycles was changed to 20.

[0044] The beneficial effect of this embodiment is as follows: Two sets of type 2 piezoelectric composite materials with the same structural parameters were prepared from the same PIN-PMN-PT piezoelectric single crystal material. One set was DC polarized, and the other was AC polarized. It was found that AC polarization resulted in a higher piezoelectric strain constant d of the type 2 piezoelectric composite material compared to DC polarization. 33 It can increase by an average of 15.4%, such as Figure 6Table 3 shows the comparison of piezoelectric properties of the 2-2 type piezoelectric composite material after AC polarization and DC polarization in Example 3.

[0045] Table 3

[0046] <![CDATA[Q m ]]> <![CDATA[K t ]]> <![CDATA[d 33 (pC / N)]]> Z(Mrayl) DC polarization 17.36 0.70 1234 23.41 Exchange polarization 12.34 0.81 1432 19.82

Claims

1. An AC polarization method for a type 2-2 piezoelectric composite material, characterized in that: An AC polarization device for a 2-2 type piezoelectric composite material includes a voltage amplifier connected to an oscilloscope and a function generator. The voltage amplifier is connected to the upper and lower electrodes of the 2-2 type piezoelectric composite material, which is immersed in silicone oil. The aforementioned AC polarization method includes the following steps: Step 1: Prepare a 2-2 type piezoelectric composite material, and fabricate electrodes on opposite surfaces in the thickness direction of the 2-2 type piezoelectric composite material; Step 2: Place the 2-2 type piezoelectric composite material prepared in Step 1 into an AC polarization device, ensuring good contact between the upper and lower electrodes and the 2-2 type piezoelectric composite material, and immerse the entire 2-2 type piezoelectric composite material in silicone oil at room temperature; Step 3: Generate an AC voltage with a symmetrical triangular wave using a function generator, amplify the voltage signal using a voltage amplifier, and apply it to the 2-2 type piezoelectric composite material. Set the peak voltage, polarization frequency, and number of polarization cycles of the AC voltage and polarize the 2-2 type piezoelectric composite material. The peak voltage is proportional to the thickness of the 2-2 type piezoelectric composite material. Step 4: After polarization is complete, wait for the voltage to return to zero, remove the 2-2 type piezoelectric composite material, clean the silicone oil on the surface of the 2-2 type piezoelectric composite material, and measure the properties of the 2-2 type piezoelectric composite material.

2. The method according to claim 1, characterized in that: The contacts of the upper and lower electrodes of the 2-2 type piezoelectric composite material are located at the center of the 2-2 type piezoelectric composite material.

3. The method according to claim 1, characterized in that, The AC polarization condition parameters in step 3 include: peak voltage of 0.8-1.5 kV / mm, polarization frequency of 0.08-10Hz, and number of polarization cycles of 5-20.

4. The method according to claim 3, characterized in that, The AC polarization condition parameters in step 3 include: peak voltage of 1 kV / mm, polarization frequency of 0.1 Hz, and polarization cycles of 8.

5. The method according to claim 3, characterized in that, The AC polarization condition parameters in step 3 include: peak voltage of 0.8 kV / mm, polarization frequency of 0.08 Hz, and polarization cycles of 5.

6. The method according to claim 3, characterized in that, The AC polarization condition parameters in step 3 include: peak voltage of 1.5 kV / mm, polarization frequency of 10 Hz, and polarization cycles of 20.

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