PMN-pzt-based lead-based piezoelectric ceramic and preparation method and application thereof

Abstract

This invention belongs to the technical field of ceramic material preparation methods, specifically relating to a PMN-PZT-based lead-based piezoelectric ceramic, its preparation method, and its application. The general chemical formula of the PMN-PZT-based ternary lead-based piezoelectric ceramic is (Pb... 1‑x Sr x (Mg) 0.33 Nb 0.67 ) 0.2 (Zr y Ti 1‑y ) 0.8 The lead-based piezoelectric ceramic is prepared by the following steps: raw materials are weighed according to the stoichiometric relationships of the elements in the general chemical formula, ball-milled, and pre-fired to obtain powder; MnCO3 is weighed according to the stoichiometric relationships of the elements in the general chemical formula, added to the powder, and ball-milled to prepare a circular green body; the circular green body is then subjected to debinding treatment and sintered to obtain the lead-based piezoelectric ceramic. The lead-based piezoelectric ceramic has a dense structure, good electrochemical performance, and good temperature stability. It can be used to prepare piezoelectric transducers and has significant application value.

Description

Technical Field

[0001] This invention belongs to the technical field of ceramic material preparation methods, specifically relating to a PMN-PZT-based lead-based piezoelectric ceramic, its preparation method, and its application. Background Technology

[0002] The information disclosed in this background section is intended to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Piezoelectric ceramics are functional materials capable of converting between electrical and mechanical energy. Lead zirconate titanate-based piezoelectric ceramics, in particular, are widely used in electronic devices, piezoelectric actuators, medical ultrasonic transducers, and acoustic sensors due to their excellent performance, low cost, and ease of processing. In recent years, with advancements in science and technology, electronic components have become increasingly sophisticated and intelligent, placing higher demands on the performance of piezoelectric ceramics.

[0004] Ultrasonic transducers are widely used in medical, industrial, and scientific research fields due to their strong detection capabilities. Among various ultrasonic transducers, piezoelectric ultrasonic transducers are popular because of their outstanding advantages such as stable performance, large acoustic radiation area, high radiation efficiency, uniform directionality, and high sensitivity. Especially in hazardous conditions such as corrosive environments and radioactive radiation, piezoelectric transducers usually perform better.

[0005] To improve the transmission power, conversion efficiency, and other performance parameters of piezoelectric ultrasonic transducers, it is necessary not only to optimize the overall structure of the transducer but also to prepare materials that possess both high electromechanical and piezoelectric properties. In recent years, lead-based piezoelectric ceramics, represented by lead zirconate titanate and its modified piezoelectric ceramics, have long dominated the ultrasonic transducer materials market due to their excellent performance. However, none of these materials can simultaneously possess high piezoelectric and electromechanical properties, which directly limits their application scenarios. Therefore, developing a material with both high electromechanical and piezoelectric properties is of great significance. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the first objective of this invention is to provide a PMN-PZT-based lead-based piezoelectric ceramic; the PMN-PZT-based lead-based piezoelectric ceramic is composed of a first-phase original ceramic matrix and manganese carbonate (MnCO3) material, and has the characteristics of dense structure and excellent electrochemical performance.

[0007] The second objective of this invention is to provide a method for preparing the above-mentioned PMN-PZT-based lead-based piezoelectric ceramics; the preparation method has the advantages of simple operation, low cost and readily available raw materials.

[0008] A third objective of this invention is to provide applications of the aforementioned PMN-PZT-based lead-based piezoelectric ceramics; the PMN-PZT-based lead-based piezoelectric ceramics can be used to prepare piezoelectric ultrasonic transducers.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A PMN-PZT-based lead-based piezoelectric ceramic, wherein the PMN-PZT-based lead-based piezoelectric ceramic has a perovskite structure;

[0011] The PMN-PZT-based lead-based piezoelectric ceramic is prepared by doping manganese carbonate (MnCO3) onto a lead magnesium niobate-lead zirconate titanate (PMN-PZT) ceramic matrix; the general chemical formula of the PMN-PZT-based lead-based piezoelectric ceramic is (Pb 1-x Sr x (Mg) 0.33 Nb 0.67 ) 0.2 (Zr y Ti 1-y ) 0.8 -zwt%MnCO3, where 0.01≤x≤0.12, 0.47≤y≤0.53, 0.1≤z≤1.

[0012] The above-mentioned method for preparing PMN-PZT-based lead-based piezoelectric ceramics comprises the following steps:

[0013] (1) According to the general chemical formula (Pb) 1-x Sr x (Mg) 0.33 Nb 0.67 ) 0.2 (Zr y Ti 1-y ) 0.8 -zwt%MnCO3, where 0.01≤x≤0.12, 0.47≤y≤0.53, 0.1≤z≤1. Weigh out raw materials Pb3O4, MgO, Nb2O5, TiO2, SrCO3, and ZrO2, mix them, and obtain mixed raw materials.

[0014] (2) The mixed raw materials obtained in step (1) are dried, and zirconium oxide balls and anhydrous ethanol are added. The mixture is then ball-milled and pre-calcined to obtain powder.

[0015] (3) Weigh manganese carbonate (MnCO3) according to the stoichiometric relationship of each element in the chemical formula in step (1), add it to the powder obtained in step (2), ball mill it, add a binder and grind it, press it to obtain a round green body;

[0016] (4) The circular green body obtained in step (3) is subjected to debinding treatment and sintered to obtain the lead-based piezoelectric ceramic.

[0017] Furthermore, in step (2), the drying temperature is 75-100°C and the time is 12-24 hours.

[0018] Further, in step (2), the mass ratio of the mixed raw materials, zirconium oxide balls and anhydrous ethanol is 1:15:15.

[0019] Furthermore, in step (2), the ball milling time is 12 to 24 hours.

[0020] Furthermore, the ball milling process requires drying.

[0021] Furthermore, the drying temperature is 70°C.

[0022] Furthermore, in step (2), the pre-firing temperature is 850-1000℃ and the time is 3-6h.

[0023] Furthermore, in step (3), the ball milling time is 12 to 24 hours.

[0024] Furthermore, in step (3), the ball milling process requires drying.

[0025] Further, in step (3), the adhesive is polyvinyl butyral or polyvinyl alcohol.

[0026] Furthermore, in step (3), the pressurization is unidirectional; the pressure of the pressurization is 2 MPa; the diameter of the circular green blank is 10 mm and the thickness is 1 mm.

[0027] Further, in step (4), the temperature of the debinding treatment is 500-900℃ and the time is 3-6h; the temperature of the sintering is 1000-1300℃ and the time is 3-5h; the heating rate of the debinding treatment and the sintering is 1-5℃ / min.

[0028] Furthermore, in step (4), the lead-based piezoelectric ceramic can be polarized by silver to obtain a polarized lead-based piezoelectric ceramic.

[0029] Further, the silver polarization is carried out by the following steps: brushing silver paste onto both sides of the sintered ceramic sample, baking at 600°C for 30 min, placing it in silicone oil, and polarizing it under an electric field of 1-4 kV / mm for 45-70 min.

[0030] The above-mentioned PMN-PZT-based lead-based piezoelectric ceramics can be used to prepare piezoelectric ultrasonic transducers.

[0031] The PMN-PZT-based lead-based piezoelectric ceramic provided by this invention is prepared by doping PMN-PZT ceramic with manganese carbonate. The manganese carbonate enters into the grains of the ceramic matrix, and because manganese carbonate has a low melting point, it promotes the formation of a liquid phase during sintering. By lowering the sintering temperature and promoting grain growth, a uniform microstructure of the ceramic is achieved, thereby improving the density of the ceramic. Furthermore, by controlling the sintering conditions, the manganese carbonate itself does not undergo a phase transition. After the addition of manganese carbonate, the piezoelectric and electromechanical properties of the ceramic are significantly improved compared to the original ceramic.

[0032] Beneficial effects: (1) The PMN-PZT-based lead-based piezoelectric ceramic provided by the present invention has good crystallinity and exhibits a typical perovskite structure with dense grains, and has good dielectric and piezoelectric properties. The inverse piezoelectric coefficient of the PMN-PZT-based lead-based piezoelectric ceramic under an electric field of 1 to 4 kV / mm is 500 to 850 pm / V, and the piezoelectric coefficient d 33 It can reach 650-730 pC / N, and the planar electromechanical coupling coefficient k p =65-75%, Curie temperature T c The temperature can reach 270-300℃, and the dielectric loss tanδ is not higher than 0.02; the acoustic impedance of the PMN-PZT-based lead-based piezoelectric ceramic is less than 150MPa·s / m, and the mechanical quality factor is Q. m The range is 250 to 750.

[0033] (2) The PMN-PZT-based piezoelectric ceramic prepared by this invention can be used to prepare piezoelectric ultrasonic transducers. By doping lead-based ceramics with manganese carbonate, this invention can significantly improve the piezoelectric coefficient, electromechanical coupling coefficient, and mechanical quality factor of the ceramic, thereby obtaining a higher ultrasonic transducer pulse-echo amplitude. The ultrasonic pulse-echo amplitude of the piezoelectric ultrasonic transducer is 8.17V, and the -6dB bandwidth is 20kHz. Attached Figure Description

[0034] Figure 1 The XRD pattern of the PMN-PZT-based lead-based piezoelectric ceramic prepared in Example 1;

[0035] Figure 2 SEM image of the PMN-PZT-based lead-based piezoelectric ceramic prepared in Example 1;

[0036] Figure 3 Dielectric temperature spectrum of PMN-PZT-based lead-based piezoelectric ceramics prepared in Example 1;

[0037] Figure 4 Hysteresis loop diagram of PMN-PZT-based lead-based piezoelectric ceramics prepared in Example 1;

[0038] Figure 5 The image shows the unipolar strain curve of the PMN-PZT-based lead-based piezoelectric ceramic prepared in Example 1.

[0039] Figure 6 The bipolar strain curve of the PMN-PZT-based lead-based piezoelectric ceramic prepared in Example 1 is shown.

[0040] Figure 7 Frequency-impedance spectrum of PMN-PZT-based lead-based piezoelectric ceramic prepared in Example 1;

[0041] Figure 8 The XRD pattern of the PMN-PZT-based lead-based piezoelectric ceramic prepared in Example 2;

[0042] Figure 9 SEM image of the PMN-PZT-based lead-based piezoelectric ceramic prepared in Example 2;

[0043] Figure 10 Dielectric temperature spectrum of PMN-PZT-based lead-based piezoelectric ceramics prepared in Example 2;

[0044] Figure 11 Hysteresis loop diagram of PMN-PZT-based lead-based piezoelectric ceramics prepared in Example 2;

[0045] Figure 12 The image shows the unipolar strain curve of the PMN-PZT-based lead-based piezoelectric ceramic prepared in Example 2.

[0046] Figure 13 The image shows the bipolar strain curve of the PMN-PZT-based lead-based piezoelectric ceramic prepared in Example 2.

[0047] Figure 14 Frequency-impedance spectrum of PMN-PZT-based lead-based piezoelectric ceramic prepared in Example 2;

[0048] Figure 15 The XRD pattern of the PMN-PZT-based lead-based piezoelectric ceramic prepared in Example 3;

[0049] Figure 16 SEM image of the PMN-PZT-based lead-based piezoelectric ceramic prepared in Example 3;

[0050] Figure 17Dielectric temperature spectrum of PMN-PZT-based lead-based piezoelectric ceramics prepared in Example 3;

[0051] Figure 18 Hysteresis loop diagram of PMN-PZT-based lead-based piezoelectric ceramics prepared in Example 3;

[0052] Figure 19 The image shows the unipolar strain curve of the PMN-PZT-based lead-based piezoelectric ceramic prepared in Example 3.

[0053] Figure 20 Frequency-impedance spectrum of PMN-PZT-based lead-based piezoelectric ceramic prepared in Example 3;

[0054] Figure 21 SEM image of the PMN-PZT-based lead-based piezoelectric ceramic prepared in Comparative Example 1;

[0055] Figure 22 Dielectric temperature spectrum of PMN-PZT-based lead-based piezoelectric ceramic prepared in Comparative Example 1;

[0056] Figure 23 The ultrasonic transducer based on PMN-PZT-based lead-based piezoelectric ceramics prepared in Example 1

[0057] The received wave's time-domain waveform and frequency-domain spectrum;

[0058] Figure 24 Comparative Example 1: A PMN-PZT-based lead-based piezoelectric ceramic ultrasonic transducer was prepared.

[0059] The received wave's time-domain waveform and frequency-domain spectrum;

[0060] Figure 25 Frequency-impedance spectrum of PMN-PZT-based lead-based piezoelectric ceramic prepared for Comparative Example 1. Detailed Implementation

[0061] To provide a more detailed description of the present invention, the following specific implementation examples are given, but are only used to illustrate the present invention and make the steps clearer, and are not intended to limit the scope of application of the present invention.

[0062] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0063] The dielectric properties of the ceramic materials prepared in Example 1 and Comparative Examples 1-2 were tested according to the methods disclosed in the following national standards of the People's Republic of China: "Quasi-static Test Method for Hysteresis Loop of Ferroelectric Ceramic Materials" (GB / T6426-1999); "Test Method for Dielectric Properties of Dielectric Crystals" (GB / T16822-1997); "Test Method for Electric Field Strain Characteristics of Piezoelectric Ceramic Materials" (GB / T 16304-2008); "Test Method for Longitudinal Length Expansion Vibration Mode of Columns" (GB / T3389.5-1995); and "Test Method for Performance Parameters of Piezoelectric Ceramic Materials" (GB / T 3389-2008).

[0064] Example 1

[0065] PMN-PZT-based ceramics with 0.4 wt% MnCO3 composite (PMN-PZT-based lead-based piezoelectric ceramics), with the chemical formula (Pb... 0.94 Sr 0.06 (Mg) 0.33 Nb 0.67 ) 0.2 (Zr 0.485 Ti 0.515 ) 0.8 -0.4wt%MnCO3.

[0066] The specific preparation method includes the following steps:

[0067] (1) Weigh Pb3O4, MgO, Nb2O5, TiO2, SrCO3, and ZrO2 according to the above general chemical formula, and dry all raw materials at 90°C for 12 hours in a vacuum drying oven; then place the raw materials, zirconium oxide balls, and anhydrous ethanol in a nylon can at a mass ratio of 1:15:15, and ball mill the mixture on a planetary ball mill for 24 hours. After drying the ball-milled slurry at 70°C, place it in a muffle furnace and pre-calcine it at 850°C for 3 hours to obtain the pre-calcined powder.

[0068] (2) Weigh MnCO3 by mass percentage and add it to the pre-fired powder obtained in step (1). Ball mill for 24 hours, dry and add an appropriate amount of polyvinyl butyral binder for grinding and granulation. Unidirectional pressure molding is applied at 2MPa to obtain a ceramic circular green body with a diameter of about 10mm and a thickness of about 1mm.

[0069] (3) The ceramic circular green body obtained in step (2) is heated to 600℃ at a heating rate of 3℃ / min and held for 3h to remove the glue. The circular piece after glue removal is sintered at 1170-1240℃ and held for 3h to obtain PMN-PZT-based lead-based piezoelectric ceramic.

[0070] (4) Print high-temperature silver paste on both sides of the PMN-PZT-based lead-based piezoelectric ceramic obtained in step (3), bake at 600°C for 0.5 h to obtain PMN-PZT-based lead-based piezoelectric ceramic containing silver electrodes. After standing for 24 h, place it in silicone oil and polarize it for 15 min under an electric field of 3 kV / mm to obtain polarized PMN-PZT-based lead-based piezoelectric ceramic containing silver electrodes.

[0071] The crystal structure and microstructure of the PMN-PZT lead-based piezoelectric ceramic obtained in step (3) of this embodiment were analyzed, and the results are as follows: Figure 1 and Figure 2 As shown; Figure 1 The image shows the X-ray diffraction (XRD) pattern of the PMN-PZT-based lead-based piezoelectric ceramic prepared in this embodiment. As can be seen from the image, the prepared PMN-PZT-based ceramic has good crystallinity and exhibits a typical perovskite structure.

[0072] Figure 2 The image shows a scanning electron microscope (SEM) image of the PMN-PZT-based lead-based piezoelectric ceramic prepared in this embodiment. As can be seen from the image, the ceramic grains are densely sintered and have no obvious pores.

[0073] The dielectric properties of the PMN-PZT-based lead-based piezoelectric ceramic containing silver electrodes obtained in step (4) of this embodiment were tested.

[0074] Figure 3 The dielectric temperature spectrum of the PMN-PZT-based lead-based piezoelectric ceramic containing silver electrodes prepared in this embodiment is shown. The results show that the ferroelectric-paraelectric phase transition temperature of the ceramic is 292℃, and the dielectric loss is small from room temperature to 200℃, all less than 0.02.

[0075] Figure 4 The hysteresis loop diagram of the polarized PMN-PZT-based lead-based piezoelectric ceramic containing silver electrodes prepared in this embodiment shows that a saturated hysteresis loop is displayed under an electric field, indicating that the ceramic has good ferroelectric properties.

[0076] Figure 5 The image shows the unipolar strain curve of the polarized PMN-PZT-based lead-based piezoelectric ceramic with silver electrodes prepared in this embodiment under an electric field. The strain can reach 0.26% under a 4 kV electric field.

[0077] Figure 6 The bipolar strain curve of the PMN-PZT-based lead-based piezoelectric ceramic containing silver electrodes prepared in this embodiment shows a negative strain of 0.31% and a positive strain of 0.19%.

[0078] Figure 7The impedance and phase angle spectra of the polarized PMN-PZT-based piezoelectric ceramic containing silver electrodes prepared in Example 1 were measured at frequencies from 200 kHz to 350 kHz. Its resonant frequency was 232.9 kHz, and its anti-resonant frequency was 298.8 kHz. The impedance at the resonant frequency was 6.29 Ω, and the phase angle was 88.6°.

[0079] Example 2

[0080] PMN-PZT-based ceramics with 0.4 wt% MnCO3 composite (PMN-PZT-based lead-based piezoelectric ceramics), with the chemical formula (Pb... 0.96 Sr 0.04 (Mg) 0.33 Nb 0.67 ) 0.2 (Zr 0.485 Ti 0.515 ) 0.8 -0.4wt%MnCO3.

[0081] The specific preparation method includes the following steps:

[0082] (1) Weigh Pb3O4, MgO, Nb2O5, TiO2, SrCO3, and ZrO2 according to the above general chemical formula, and dry all raw materials at 90°C for 12 hours in a vacuum drying oven; then place the raw materials, zirconium oxide balls, and anhydrous ethanol (mass ratio of 1:15:15) in a nylon can and ball mill them on a planetary ball mill for 24 hours; after drying the ball-milled slurry at 70°C, place it in a muffle furnace and pre-calcine at 850°C for 3 hours to obtain the pre-calcined powder;

[0083] (2) Weigh MnCO3 according to the mass percentage ratio and add it to the pre-fired powder obtained in step (1). Ball mill for 24 hours again. After ball milling for 24 hours and drying, add an appropriate amount of polyvinyl butyral binder for grinding and granulation. Then, press the powder under unidirectional pressure at 2MPa to obtain a ceramic circular green body with a diameter of about 10mm and a thickness of about 1mm.

[0084] (3) The ceramic circular green body obtained in step (2) is heated to 600℃ at a heating rate of 3℃ / min and held for 3h for debinding treatment. The debinded circular piece is sintered at 1170~1240℃ for 3h to obtain PMN-PZT-based lead-based piezoelectric ceramic.

[0085] (4) Print high-temperature silver paste on both sides of the piezoelectric ceramic obtained in step (3), bake at 600°C for 0.5h to obtain PMN-PZT-based lead-based piezoelectric ceramic containing silver electrodes. After standing for 24h, place it in silicone oil and polarize it for 15min under an electric field of 3kV / mm to obtain the polarized PMN-PZT-based lead-based piezoelectric ceramic containing silver electrodes.

[0086] The crystal structure and microstructure of the PMN-PZT-based piezoelectric ceramic obtained in step (3) of this embodiment were analyzed, and the results are as follows: Figure 8 and Figure 9 As shown; Figure 8 The image shows the XRD pattern of the PMN-PZT-based lead-based piezoelectric ceramic prepared in this embodiment. As can be seen from the image, the PMN-PZT-based lead-based piezoelectric ceramic has good crystallinity and exhibits a typical perovskite structure.

[0087] Figure 9 The image shows a SEM image of the PMN-PZT-based lead-based piezoelectric ceramic prepared in Example 2. As can be seen from the image, the ceramic grains are densely sintered and have no obvious pores.

[0088] The dielectric properties of the PMN-PZT-based lead-based piezoelectric ceramic containing silver electrodes prepared in this embodiment were tested.

[0089] Figure 10 The dielectric temperature spectrum of the PMN-PZT-based lead-based piezoelectric ceramic containing silver electrodes prepared in this embodiment was tested in the temperature range of 0 to 350°C. The results show that its ferroelectric-paraelectric phase transition temperature is 288°C and the dielectric loss is less than 0.01 at room temperature.

[0090] Figure 11 The hysteresis loop diagram of the polarized PMN-PZT-based lead-based piezoelectric ceramic containing silver electrodes prepared in this embodiment shows that a saturated hysteresis loop is displayed under an electric field, indicating that the prepared ceramic has good ferroelectric properties.

[0091] Figure 12 The image shows the unipolar strain curve of the polarized PMN-PZT-based lead-based piezoelectric ceramic with silver electrodes prepared in this embodiment under an electric field. The strain can reach 0.194% under a 4 kV electric field.

[0092] Figure 13 The bipolar strain curve of the PMN-PZT-based lead-based piezoelectric ceramic containing silver electrodes prepared in this embodiment shows a negative strain of 0.28% and a positive strain of 0.17%.

[0093] Figure 14 The impedance and phase angle spectra of the polarized PMN-PZT-based piezoelectric ceramic with silver electrodes prepared in Example 2 were measured at frequencies from 200 kHz to 350 kHz. Its resonant frequency was 234.1 kHz, and its anti-resonant frequency was 293.2 kHz. The impedance at the resonant frequency was 6.6 Ω, and the phase angle was 88.2°.

[0094] Example 3

[0095] 0.8 wt% manganese carbonate (MnCO3) doped PMN-PZT-based ceramics, with the chemical formula (Pb 0.94 Sr 0.06 (Mg) 0.33 Nb 0.67 ) 0.2 (Zr 0.485 Ti 0.515 ) 0.8 -0.8wt%MnCO3.

[0096] The specific preparation method includes the following steps:

[0097] (1) Weigh Pb3O4, MgO, Nb2O5, TiO2, SrCO3, and ZrO2 according to the above general chemical formula, and dry all raw materials at 90°C for 12 hours in a vacuum drying oven; then place the raw materials, zirconium oxide balls, and anhydrous ethanol (mass ratio of 1:15:15) in a nylon can and ball mill them on a planetary ball mill for 24 hours; after drying the ball-milled slurry at 70°C, place it in a muffle furnace and pre-calcine at 850°C for 3 hours to obtain the pre-calcined powder;

[0098] (2) Weigh out MnCO3 according to the mass percentage ratio, add it to the pre-calcined powder, and ball mill again for 24 hours;

[0099] After ball milling for 24 hours and drying, an appropriate amount of polyvinyl butyral binder is added for grinding and granulation. The mixture is then unidirectionally pressurized at 2 MPa to obtain a ceramic circular green body with a diameter of about 10 mm and a thickness of about 1 mm.

[0100] (3) The ceramic circular green body obtained in step (2) is heated to 600℃ at a heating rate of 3℃ / min and held for 3h for debinding treatment. The debinded circular piece is sintered at 1170~1220℃ for 3h to obtain PMN-PZT-based lead-based piezoelectric ceramic.

[0101] (4) Print high-temperature silver paste on both sides of the piezoelectric ceramic obtained in step (3), bake at 600°C for 0.5h to obtain PMN-PZT-based lead-based piezoelectric ceramic containing silver electrodes. After standing for 24h, place it in silicone oil and polarize it for 15min under an electric field of 3kV / mm to obtain the polarized PMN-PZT-based lead-based piezoelectric ceramic containing silver electrodes.

[0102] The crystal structure and microstructure of the PMN-PZT-based lead-based piezoelectric ceramic obtained in step (3) of this embodiment were analyzed, and the results are as follows: Figure 15 and Figure 16 As shown; Figure 15 The image shows the XRD pattern of the PMN-PZT-based ceramic prepared in this embodiment. As can be seen from the image, the prepared PMN-PZT-based ceramic has good crystallinity and exhibits a typical perovskite structure.

[0103] Figure 16 The image shows the SEM image of the 0.8 wt% MnCO3-doped PMN-PZT-based ceramic prepared in Example 3. The image shows that the ceramic grains are densely sintered with no obvious pores.

[0104] The electrical properties of the polarized ceramic containing silver electrodes obtained in step (4) of this embodiment were tested.

[0105] Figure 17 The dielectric temperature spectrum of the PMN-PZT-based lead-based piezoelectric ceramic containing silver electrodes prepared in this embodiment was tested in the temperature range of 0 to 350°C. The results show that its ferroelectric-paraelectric phase transition temperature is 284°C and the dielectric loss is less than 0.01 at room temperature.

[0106] Figure 18 The hysteresis loop diagram of the polarized PMN-PZT-based lead-based piezoelectric ceramic containing silver electrodes prepared in this embodiment shows that a saturated hysteresis loop is displayed under an electric field, indicating that the prepared ceramic has good ferroelectric properties.

[0107] Figure 19 The image shows the unipolar strain curve of the polarized PMN-PZT-based lead-based piezoelectric ceramic with silver electrodes prepared in this embodiment under an electric field. The strain can reach 0.187% under a 4 kV electric field.

[0108] Figure 20 The impedance and phase angle spectra of the polarized PMN-PZT-based piezoelectric ceramic containing silver electrodes prepared in this embodiment were measured at frequencies from 200 kHz to 350 kHz. Its resonant frequency was 263.5 kHz, and its anti-resonant frequency was 305.1 kHz. The impedance at the resonant frequency was 1.88 Ω, and the phase angle was 89.6°.

[0109] Comparative Example 1

[0110] Undoped PMN-PZT-based piezoelectric ceramics, with the chemical formula (Pb 0.96 Sr 0.04 (Mg) 0.33 Nb 0.67 ) 0.2 (Zr 0.525 Ti 0.475 ) 0.8 .

[0111] The specific preparation method includes the following steps:

[0112] (1) Weigh Pb3O4, MgO, Nb2O5, TiO2, SrCO3, and ZrO2 according to the above general chemical formula, and dry all raw materials at 90°C for 12 hours in a vacuum drying oven; then place the raw materials, zirconium oxide balls, and anhydrous ethanol (mass ratio of 1:15:15) in a nylon can and ball mill them on a planetary ball mill for 24 hours; after drying the ball-milled slurry at 70°C, place it in a muffle furnace and pre-calcine at 850°C for 3 hours to obtain the pre-calcined powder;

[0113] (2) The pre-fired powder obtained in step (1) is ball-milled again for 24 hours, dried, and then an appropriate amount of polyvinyl butyral binder is added for grinding and granulation. The powder is then unidirectionally pressed and molded at 2MPa to obtain a ceramic circular green body with a diameter of about 10mm and a thickness of about 1mm.

[0114] (3) The ceramic circular green body obtained in step (2) is heated to 600℃ at a heating rate of 3℃ / min and held for 3h for debinding treatment. The debinded circular piece is sintered at 1240℃ for 3h to obtain PMN-PZT-based lead-based piezoelectric ceramic.

[0115] (4) Print high-temperature silver paste on both sides of the piezoelectric ceramic obtained in step (3), bake at 600°C for 0.5h to obtain PMN-PZT-based lead-based piezoelectric ceramic containing silver electrodes. After standing for 24h, place it in silicone oil and polarize it for 15min under an electric field of 3kV / mm to obtain the polarized PMN-PZT-based lead-based piezoelectric ceramic containing silver electrodes.

[0116] The microstructure of the PMN-PZT-based lead-based piezoelectric ceramic obtained in step (3) was analyzed. Figure 21 The image shows the SEM pattern of the undoped PMN-PZT-based ceramic prepared in Comparative Example 1. As can be seen from the image, the prepared PMN-PZT-based ceramic has uneven grain size and porosity.

[0117] The electrical properties of the PMN-PZT-based lead-based piezoelectric ceramics containing silver electrodes obtained in this comparative example after polarization were tested.

[0118] Figure 22 The dielectric temperature spectrum of the PMN-PZT-based lead-based piezoelectric ceramic with silver electrode prepared as Comparative Example 1 was obtained by testing in the temperature range of 0 to 350℃. The results show that its ferroelectric-paraelectric phase transition temperature is only 267℃, and the dielectric loss is greater than 0.01 at room temperature.

[0119] Figure 25The impedance and phase angle spectra of the polarized PMN-PZT-based lead-based piezoelectric ceramic containing silver electrodes prepared for Comparative Example 1 were measured at frequencies ranging from 200 kHz to 350 kHz. Its resonant frequency was 224.1 kHz, and its anti-resonant frequency was 252.31 kHz. The impedance at the resonant frequency was 44.6 Ω, and the phase angle was only 80.6°.

[0120] Application Examples

[0121] 1. Preparation of ceramics as piezoelectric ultrasonic transducers: The PMN-PZT lead-based piezoelectric ceramics prepared in Example 1 and Comparative Example 1 were ground to a diameter of 10 mm and a thickness of 0.5 mm. An alumina sheet with a diameter of 10 mm and a thickness of 2 mm was used as a matching layer, and a 200-mesh copper mesh was used as a shielding layer. They were encapsulated in a custom steel shell mold and used as the transmitting and receiving transducers, respectively. The transmitting transducer was connected by an AFG3022C signal generator from Tektronix Technology Co., Ltd., and the HEAS-20 power amplifier produced by Nanjing Fountain Technology Co., Ltd. was responsible for providing the system with an alternating signal. The transmitting and receiving transducers were placed in water at a depth of 30 cm along the same center line. Finally, the transmitting transducer was connected to a Keysight InfiniiVision DSOX3014T oscilloscope and a 2450 digital source meter to display the received wave time-domain waveform and frequency-domain spectrum of the ultrasonic transducer.

[0122] The pulse and echo response performance of the ultrasonic transducers prepared using the polarized PMN-PZT lead-based piezoelectric ceramics containing silver electrodes obtained in Example 1 and Comparative Example 1 were tested.

[0123] Figure 23 The received wave time-domain waveform and frequency domain spectrum of the PMN-PZT-based lead-based piezoelectric ceramic ultrasonic transducer with polarized silver electrodes prepared in Example 1 are shown. The prepared piezoelectric transducer has a received ultrasonic amplitude of 8.17V. Figure 24 The received wave time-domain waveform and frequency domain spectrum of the PMN-PZT-based lead-based piezoelectric ceramic ultrasonic transducer with polarized silver electrodes prepared for Comparative Example 1 are shown. The prepared piezoelectric transducer has a received ultrasonic amplitude of only 7.17V.

[0124] The above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made based on the essence of the content of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing PMN-PZT-based lead-based piezoelectric ceramics, characterized in that, The PMN-PZT-based lead-based piezoelectric ceramic has a general chemical formula of (Pb 1-x Sr x )(Mg 0.33 Nb 0.67 ) 0.2 (Zr y Ti 1-y ) 0.8 zwt% MnCO3, wherein 0.01≤x≤0.12, 0.47≤y≤0.53, and 0.1≤z≤1. The preparation method comprises the following steps: (1) Weigh Pb3O4, MgO, Nb2O5, TiO2, SrCO3, and ZrO2 according to the general chemical formula, mix them, and obtain mixed raw materials; (2) The mixed raw materials obtained in step (1) are dried, and zirconium oxide balls and anhydrous ethanol are added. The mixture is then ball-milled and pre-calcined to obtain powder. (3) Weigh MnCO3 according to the stoichiometric relationship of each element in the chemical formula in step (1), add it to the powder obtained in step (2), ball mill it, add a binder and grind it, press it to obtain a round green body; (4) The circular green body obtained in step (3) is subjected to debinding treatment and sintered to obtain the lead-based piezoelectric ceramic; In step (4), the temperature of the debinding treatment is 500~900°C, the time is 3~6 h, and the heating rate is 1~5°C / min; the temperature of the sintering is 1000~1300°C, the time is 3~5 h, and the heating rate is 1~5°C / min.

2. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of the mixed raw materials, zirconium oxide balls and anhydrous ethanol is 1:15:

15.

3. The preparation method according to claim 1, characterized in that, In step (2), the drying temperature is 75~100°C and the time is 12~24 h; The ball milling time is 12-24 hours; The ball milling process also requires drying. The pre-firing temperature is 850~1000℃, and the time is 3~6 h.

4. The preparation method according to claim 3, characterized in that, The drying temperature is 70°C.

5. The preparation method according to claim 1, characterized in that, In step (3), the adhesive is polyvinyl butyral or polyvinyl alcohol.

6. The preparation method according to claim 1, characterized in that, In step (3), the ball milling time is 12~24h; The ball milling process requires subsequent drying.

7. The application of the piezoelectric ceramic prepared by the method according to any one of claims 1-6 in the preparation of ultrasonic transducers.

Images