31-mode composite piezoelectric crystal and sensing sound head

Abstract

The utility model relates to a 31-mode composite piezoelectric crystal and a sensing sound head, which comprise a piezoelectric single crystal and a high-molecular polymer, the polarization direction of the piezoelectric single crystal is [011] direction, and the cutting direction is [100] direction (31 direction); the piezoelectric single crystal comprises a plurality of piezoelectric single crystal units, the high-molecular polymer comprises a plurality of high-molecular polymer units, and the piezoelectric single crystal units and the high-molecular polymer units are arranged in parallel at intervals; the composite piezoelectric crystal further comprises a first thin film electrode and a second thin film electrode, and the first thin film electrode and the second thin film electrode are located at the top and the bottom of a composite structure formed by the piezoelectric single crystal and the high-molecular polymer respectively. The electromechanical coupling coefficient k31 in the axial direction (31 direction) and the piezoelectric constant d31 in the axial direction of the piezoelectric crystal are improved, so that the bandwidth and the sensitivity of the sound head of the sensor are improved.

Description

Technical Field

[0001] The utility model relates to the technical field of piezoelectric single crystal materials and their manufacturing technologies, and particularly relates to a 31-mode composite piezoelectric crystal and a sensing sound head. Background Art

[0002] Piezoelectric materials can convert electrical energy and mechanical energy to transmit and receive ultrasonic signals, and are the core components among acoustic sensors. In recent years, some piezoelectric single crystals, such as relaxor ferroelectric single crystal lead magnesium niobate-lead titanate (abbreviated as PMN-PT) crystals and lead indium niobate-lead magnesium niobate-lead titanate (PIN-PMN-PT) crystals, have begun to be used in fields such as medical ultrasonic imaging, industrial non-destructive testing, and underwater sonar. When the chemical composition of lead titanate (abbreviated as PT) is close to the MPB phase boundary, the axial electromechanical coupling coefficient (k31) of this crystal can reach more than 90%, and the axial piezoelectric constant (d31) can reach more than 1500 pC / N, far exceeding the traditional lead zirconate titanate (abbreviated as PZT) piezoelectric ceramic materials, which can make the ultrasonic and sonar sensors with axial vibration have higher sensitivity and larger bandwidth.

[0003] However, if the piezoelectric crystal is directly used without domain engineering cutting, the piezoelectric effect of the sensor element in the axial direction (31 direction) will be weakened by the piezoelectric effects in other directions, resulting in the fact that the actual axial electromechanical coupling coefficient often cannot reach the ideal k31 value, and the axial piezoelectric constant cannot reach the ideal d31 value, thus unable to meet the requirements of most ultrasonic and sonar sensors for ultra-high bandwidth and sensitivity.

[0004] In view of the above problems, the present utility model document proposes a 31-mode composite piezoelectric crystal and a sensing sound head. Summary of the Utility Model

[0005] The purpose of the present utility model is to solve the disadvantages in the prior art that the actual axial electromechanical coupling coefficient often cannot reach the ideal k31 value and the axial piezoelectric constant cannot reach the ideal d31 value, and at the same time solve the disadvantages such as difficult crystal polarization and high material cost existing in the sensors of the thickness 33 mode, and propose a 31-mode composite piezoelectric crystal and a sensing sound head.

[0006] In order to achieve the above purpose, the present utility model adopts the following technical solutions:

[0007] A 31-mode composite piezoelectric crystal, comprising:

[0008] A piezoelectric single crystal and a polymer, wherein the polarization direction of the piezoelectric single crystal is the

[011] direction and the cutting direction is the

[100] direction (31 direction); the piezoelectric single crystal includes a plurality of piezoelectric single crystal units, the polymer includes a plurality of polymer units, and the piezoelectric single crystal units and the polymer units are arranged in parallel at intervals;

[0009] It further includes a first thin film electrode and a second thin film electrode, and the first thin film electrode and the second thin film electrode are respectively located at the top and bottom of the composite structure formed by the piezoelectric single crystal and the polymer.

[0010] In a possible design, the piezoelectric single crystal is any one of lead magnesium niobate-lead titanate crystals, PZN-PT crystals, and lead niobium indate-lead magnesium niobate-lead titanate crystals.

[0011] In a possible design, the cross-sectional width w of each piezoelectric single crystal unit is 5 μm - 10 mm, the aspect ratio ranges from 1 to 5 times, and the length-width ratio is greater than 2.5 times.

[0012] In a possible design, the polymer is epoxy resin.

[0013] In a possible design, the epoxy resin is filled with one or more of metal particles, oxide particles, foaming agents, and vacuum glass microspheres.

[0014] In a possible design, the volume fraction of the piezoelectric single crystal in the composite piezoelectric crystal is 20% - 80%.

[0015] In a possible design, both the first thin film electrode and the second thin film electrode are any one of chromium / gold spray coatings, nickel cadmium / gold spray coatings, nickel / gold spray coatings, silver plating layers, and copper plating layers.

[0016] A sensing sound head, comprising:

[0017] The 31-mode composite piezoelectric crystal described in any one of the above;

[0018] It further includes an acoustic matching layer;

[0019] It further includes an acoustic backing layer;

[0020] It further includes a first wire and a second wire. One ends of the first wire and the second wire are electrically connected to the first thin film electrode and the second thin film electrode respectively, and the other ends of the first wire and the second wire are electrically connected to the acoustic matching layer and the acoustic backing layer respectively; the

[100] direction (31 direction) of the crystal is the vibration sensing direction.

[0021] In a possible design, the acoustic matching layer and the acoustic backing layer are adhesively bonded to the adjacent first thin-film electrode and second thin-film electrode by any one of conductive adhesive, epoxy resin, and polyurethane.

[0022] Beneficial effects:

[0023] In the present utility model, by providing a composite piezoelectric crystal, the electromechanical coupling coefficient k31 and the piezoelectric constant d31 in the axial direction (31 direction) of the piezoelectric crystal can be further improved, so as to improve the bandwidth and sensitivity of the sensor sound head, and meet the requirements of miniaturized medical and underwater acoustic ultrasonic sensors for ultra-high bandwidth and sensitivity. Description of the drawings

[0024] Figure 1 It is a schematic structural diagram of the composite piezoelectric crystal of a 31-mode composite piezoelectric crystal and a sensing sound head proposed by the present utility model;

[0025] Figure 2 It is a partial side view structural diagram of the sensor sound head of a 31-mode composite piezoelectric crystal and a sensing sound head proposed by the present utility model.

[0026] In the figure: 1. Composite piezoelectric crystal; 12. Piezoelectric single crystal unit; 14. Polymer unit; 16. First thin-film electrode; 18. Second thin-film electrode; 2. Sensor sound head; 26. Acoustic matching layer; 28. Acoustic backing layer. Specific embodiments

[0027] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments.

[0028] Embodiment 1

[0029] Refer to Figure 1 、 Figure 2 , a 31-mode composite piezoelectric crystal and a sensing sound head, including:

[0030] A composite piezoelectric crystal 1, which includes a piezoelectric single crystal and a polymer. The polarization direction of the piezoelectric single crystal is the

[011] direction, and the cutting direction is

[100] ;

[0031] In an embodiment, the piezoelectric single crystal includes a plurality of piezoelectric single crystal units 12, the polymer includes a plurality of polymer units 14, and the piezoelectric single crystal units 12 and the polymer units 14 are arranged in parallel at intervals. Refer to the attached Figure 1 shown.

[0032] Optionally, the composite piezoelectric crystal 1 further includes a first thin-film electrode 16 and a second thin-film electrode 18 located on the upper surface and the lower surface of the composite piezoelectric crystal 1. Preferably, the thickness of the first thin-film electrode 16 and the second thin-film electrode 18 is 0.1 μm - 2 μm. The method of spraying the thin-film electrode can be chemical plating or magnetron sputtering. The first thin-film electrode 16 and the second thin-film electrode 18 can be a chromium / gold spray coating, or a nickel-cadmium / gold spray coating, or a nickel / gold spray coating, or silver plating, or copper plating. As an alternative embodiment, silver paste can be coated on the upper and lower surfaces of the composite piezoelectric crystal 1 and then dried by heating. Preferably, the thickness of the silver paste is 1 μm - 10 μm.

[0033] The length of the single piezoelectric crystal unit 12 is l, the width is w, and the height is t. The crystal orientations in the length, width, and height directions are

[100] , [0 - 11], and

[011] directions respectively. Preferably, the width w is between 5 μm and 10 mm, the aspect ratio of height to width (t:w) of the single piezoelectric crystal unit 12 is between 1 and 5, and the aspect ratio of length to width is more than 2.5.

[0034] The single piezoelectric crystal can be, for example, a lead magnesium niobate-lead titanate (abbreviated as PMN-PT) crystal, a PZN-PT crystal, or a lead indium niobate-lead magnesium niobate-lead titanate (PIN-PMN-PT) crystal. The cross-sectional width w of each single piezoelectric crystal unit 12 is preferably 5 μm - 10 mm, the aspect ratio of height to width is preferably 1 - 5, and the aspect ratio of length to width is more than 2.5. In the composite piezoelectric crystal 1, the volume fraction of the single piezoelectric crystal is preferably 20% - 80%.

[0035] The polymer can be an epoxy resin. In one embodiment, the epoxy resin is filled with one or more of metal particles, oxide particles, foaming agents, and vacuum glass microspheres.

[0036] This application can be used in the technical field of single piezoelectric crystal materials and their manufacturing, and can also be used in other fields applicable to this application.

[0037] Example 2

[0038] Reference Figure 2 , on the basis of Example 1, an improvement is made: a 31-mode composite piezoelectric crystal and a sensing sound head, which are applied to the technical field of single piezoelectric crystal materials and their manufacturing;

[0039] Furthermore, the present utility model further provides a sensor sound head 2 including the above-mentioned composite piezoelectric crystal 1. The sensor sound head 2, in addition to including the composite piezoelectric crystal 1, further includes a first wire and a second wire (not shown), an acoustic matching layer 26, and an acoustic backing layer 28. Among them, the first wire and the second wire are respectively led out from the first thin-film electrode 16 and the second thin-film electrode 18 and are respectively electrically connected to the acoustic matching layer 26 and the acoustic backing layer 28.

[0040] In a preferred embodiment, the acoustic matching layer 26 and the acoustic backing layer 28 are respectively bonded to the adjacent first thin film electrode 16 and second thin film electrode 18 by conductive adhesive, epoxy resin or polyurethane, as Figure 2 shown.

[0041] The present invention also provides a method for preparing the composite piezoelectric crystal 1, which includes the following technological steps:

[0042] (1) Select a suitable piezoelectric single crystal. In one embodiment, one can be selected from, for example, PMN-PT crystal, PZN-PT crystal and PIN-PMN-PT crystal;

[0043] (2) Orient the piezoelectric single crystal by Laue diffraction method to determine the

[011] ,

[100] and [0 - 11] directions;

[0044] (3) Cut parallel incisions along the

[100] direction of the piezoelectric single crystal, and the large face direction of the single crystal is the

[011] direction. In one embodiment, diamond automatic scribing can be used for cutting. In another embodiment, parallel incisions or grooves can be etched along the

[100] direction of the piezoelectric single crystal by using a plasma etching device, and the above plasma etching device can be, for example, an inductively coupled plasma etcher;

[0045] (4) Pour a high molecular polymer into the formed incisions. After curing, remove the excess high molecular polymer on the surface. Preferably, the high molecular polymer is epoxy resin;

[0046] (5) Spray the corresponding first thin film electrode 16 and second thin film electrode 18 on the upper and lower surfaces of the obtained composite structure of the piezoelectric single crystal and the high molecular polymer. Preferably, the thickness of the first thin film electrode 16 and the second thin film electrode 18 is 0.1μm - 2μm, and the method for spraying the thin film electrode can be magnetron sputtering method; the thin film electrode can be a chromium / gold spray coating, or a nickel cadmium / gold spray coating, or a nickel / gold spray coating, or silver plating, or copper plating; As an alternative embodiment, silver paste can be coated on the upper and lower surfaces of the composite piezoelectric crystal 1, and then dried by heating. Preferably, the thickness of the silver paste is 1μm - 10μm;

[0047] (6) Perform polarization treatment on the piezoelectric single crystal under the polarization condition of 0.2 - 1.0 kV / mm, and then the composite piezoelectric crystal 1 of the present invention is obtained.

[0048] Optionally, after the above step (4) and before step (5), a grinding and polishing treatment step for the cured epoxy resin can be performed, so that the piezoelectric single crystal is exposed on both the upper and lower surfaces, which is beneficial for better spraying of the thin film electrode.

[0049] The present utility model also discloses a method for manufacturing a sensor sound head 2 including the above-mentioned composite piezoelectric crystal 1. In addition to the above-mentioned step method, the method further includes the following technological steps:

[0050] (7) Lead out a first wire and a second wire on the first thin-film electrode 16 and the second thin-film electrode 18 of the composite piezoelectric crystal 1 respectively. The first wire and the second wire are respectively connected to the acoustic matching layer 26 and the acoustic backing layer 28, thereby forming the sensor sound head 2 in the acoustic sensor. Further, the acoustic matching layer 26 and the acoustic backing layer 28 can be adhered to the top of the adjacent first thin-film electrode 16 and the bottom of the second thin-film electrode 18 through conductive adhesive or epoxy resin or polyurethane.

[0051] In addition, the present utility model also tested the volume fraction of the piezoelectric single crystal in the composite piezoelectric crystal 1 and the corresponding acoustic impedance value of the composite piezoelectric crystal 1. See the following Table 3 for details:

[0052] Single crystal volume fraction Composite material acoustic impedance value (Mega Rayl (MRayl)) 0.3 6 0.35 7 0.4 8 0.45 9 0.5 10 0.55 11 0.6 12 0.65 13 0.7 14 1 20

[0053] Table 3 shows the law that when the PMN-PT piezoelectric crystal is made into the composite piezoelectric crystal 1 of the present utility model, the acoustic impedance changes with the change of the single-crystal volume fraction. When the volume fraction is smaller, the acoustic impedance value of the composite piezoelectric crystal 1 is closer to that of human tissue or seawater, which makes the acoustic matching in sensor design easier, the bandwidth of the sensor becomes wider, and the sensitivity is improved accordingly.

[0054] As described above, only the preferred specific embodiments of the present utility model are provided, but the protection scope of the present utility model is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present utility model, according to the technical solution and the inventive concept of the present utility model, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present utility model.

Claims

1. A 31-mode composite piezoelectric crystal, characterized in that, Comprising: A piezoelectric single crystal and a polymer. The polarization direction of the piezoelectric single crystal is the [011] direction, and the cutting direction is the [100] direction. The piezoelectric single crystal includes a plurality of piezoelectric single crystal units (12), and the polymer includes a plurality of polymer units (14). The piezoelectric single crystal units (12) and the polymer units (14) are arranged in parallel at intervals; It further includes a first thin film electrode (16) and a second thin film electrode (18). The first thin film electrode (16) and the second thin film electrode (18) are respectively located at the top and bottom of the composite structure formed by the piezoelectric single crystal and the polymer; The cross-sectional width w of each piezoelectric single crystal unit (12) is 5 μm - 10 mm, the aspect ratio ranges from 1 to 5 times, and the length-width ratio is greater than 2.5 times; The volume fraction of the piezoelectric single crystal in the composite piezoelectric crystal (1) is 20% - 80%.

2. The 31-mode composite piezoelectric crystal according to claim 1, characterized in that The piezoelectric single crystal is any one of lead magnesium niobate-lead titanate crystal, PZN-PT crystal, and lead niobium indate-lead magnesium niobate-lead titanate crystal.

3. A 31-mode composite piezoelectric crystal according to claim 1, wherein The polymer is epoxy resin.

4. A 31-mode composite piezoelectric crystal according to claim 3, characterized in that At least one filler such as metal particles, oxide particles, foaming agent, and vacuum glass microspheres is filled inside the epoxy resin.

5. A 31-mode composite piezoelectric crystal according to claim 1, characterized in that, The first thin film electrode (16) and the second thin film electrode (18) are both any one of a chromium / gold spray coating, a nickel cadmium / gold spray coating, a nickel / gold spray coating, a silver plating layer, and a copper plating layer.

6. A sensing sound head, characterized in that, Comprising: The 31-mode composite piezoelectric crystal according to any one of claims 1 - 5 above; It further includes an acoustic matching layer (26); It further includes an acoustic backing layer (28); It further includes a first wire and a second wire. One ends of the first wire and the second wire are respectively electrically connected to the first thin film electrode (16) and the second thin film electrode (18), and the other ends of the first wire and the second wire are respectively electrically connected to the acoustic matching layer (26) and the acoustic backing layer (28).

7. A sensing sound head according to claim 6, characterized in that, The acoustic matching layer (26) and the acoustic backing layer (28) are adhesively bonded to the adjacent first thin film electrode (16) and second thin film electrode (18) through any one of conductive glue, epoxy resin, and polyurethane.

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