A PBZT-based piezoelectric ceramic for medical ultrasound transducers and its preparation method

Abstract

This invention relates to a PBZT-based piezoelectric ceramic for medical ultrasound transducers and its preparation method. The chemical formula of the PBZT-based piezoelectric ceramic of this invention is Pb. 0.94 Ba 0.06 (Zr 0.52 Ti 0.48 ) 0.94 (Mn 1 / 3 Nb 2 / 3 ) 0.06 O3+xwt%Fe2O3, where 0.1≤x≤0.7. This invention selects binary PBZT as the matrix material and obtains PZT-based piezoelectric materials with excellent electrical properties by co-doping Zr and Ti elements at the B site with Mn, Nb, and Fe. A piezoelectric ceramic material with excellent comprehensive performance, possessing high mechanical quality factor, high piezoelectric coefficient, and high Curie temperature, has been successfully prepared, suitable for high-power medical ultrasonic transducers.

Description

Technical Field

[0001] This invention belongs to the field of piezoelectric ceramic material preparation technology, specifically involving PBZT-based piezoelectric ceramics for medical ultrasound transducers and their preparation methods. Background Technology

[0002] Piezoelectric ceramics are functional materials capable of converting electrical energy into mechanical energy. In recent years, piezoelectric ceramic materials have been developing towards higher voltage and higher power applications. High-power piezoelectric ceramics are commonly used in welding, ultrasonic motors, and ultrasonic transducers. In practical applications, high-power piezoelectric devices generate intense vibrations within the ultrasonic frequency range, producing heat due to unavoidable mechanical and dielectric losses. Increased temperature leads to deterioration of the material's piezoelectric properties and drift in the device's resonant frequency, resulting in erratic operation of the high-power device. Therefore, the practicality of piezoelectric ceramics in high-power applications also depends on their low dielectric loss (tanδ) and high mechanical quality factor (Q). m ) and high Curie temperature (T C This is to avoid excessive heat loss during high-power transmission.

[0003] To meet the performance requirements of high-power applications, the most common solution is doping modification. Equivalent doping (such as using Ba) is one such method. 2+ Alkaline earth metal ions can shift the quasi-isomorphic phase boundary of the material towards the zirconium-rich side and, to some extent, suppress lead volatilization, promoting material densification and thus increasing the piezoelectric coefficient to a certain extent. Simultaneously, hard doping (or donor-acceptor complex doping, such as Mn and Nb co-doping) can partially replace Zr with low-valence metal ions. 4+ Ti 4+ Oxygen vacancies form, causing cell shrinkage and distortion, thus improving the mechanical quality factor. However, in practical medical ultrasound transducer applications, traditional single hard doping or conventional composite doping often faces the bottleneck of balancing piezoelectric performance and mechanical quality factor: while defect dipoles greatly improve the mechanical quality factor, their strong domain wall pinning effect often leads to a sharp decrease in the piezoelectric coefficient. Therefore, how to further control multiple defects by introducing novel transition metal ions (such as Fe ions) on a high-quality donor-acceptor co-doped PBZT substrate, breaking through the mutually restrictive performance bottlenecks, and developing piezoelectric ceramic materials with high mechanical quality factor, high piezoelectric coefficient, and excellent temperature stability has become a pressing technical challenge in the field of high-power piezoelectric ceramics. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a PBZT-based piezoelectric ceramic for medical ultrasound transducers and its preparation method.

[0005] In a first aspect, the present invention provides a PBZT-based piezoelectric ceramic material, wherein the chemical composition of the PBZT-based piezoelectric ceramic material is Pb. 0.94 Ba 0.06 (Zr 0.52 Ti 0.48 ) 0.94 (Mn 1 / 3 Nb 2 / 3 ) 0.06 O3+xwt%Fe2O3, where 0.1≤x≤0.7, and x=0.1, 0.3, 0.5, 0.7.

[0006] Furthermore, the mechanical quality factor of the PBZT-based piezoelectric ceramic material can reach 1197.

[0007] The piezoelectric coefficient of the PBZT-based piezoelectric ceramic material can reach 397 pC / N.

[0008] The Curie temperature of the PBZT-based piezoelectric ceramic material can reach 316°C.

[0009] Secondly, the present invention provides a method for preparing the above-mentioned PBZT-based piezoelectric ceramic material, the method comprising the following steps: (1) Pb3O4 powder, BaCO3 powder, ZrO2 powder, TiO2 powder, MnO2 powder and Nb2O5 powder were weighed according to the chemical composition stoichiometry of the above PBZT-based piezoelectric ceramic materials, and the raw material powder was obtained after mixing, drying and sieving. (2) The raw material powder is pre-fired to obtain ceramic powder; (3) The ceramic powder is added to Fe2O3 in different mass percentages and then subjected to secondary grinding, drying and sieving to obtain ceramic powder; (4) The ceramic powder is ground with polyvinyl alcohol solution (granulation) and then pressed into a preform (forming). (5) The ceramic preform is debonded, sintered with powder, and cooled to obtain the PBZT-based piezoelectric ceramic material.

[0010] Furthermore, the purity of the raw material powders mentioned in steps (1) and (3) is as follows: Pb3O4 > 97.3%, ZrO2 > 99.5%, TiO2 > 99.7%, and the purity of the remaining raw materials > 99.9%. The mixing method is planetary ball milling, the milling media are zirconium balls and deionized water, the weight ratio of material to water is 1:0.9, the weight ratio of balls to material is 3:1, the milling speed is 350 r / min, and the milling time is 4 h.

[0011] The drying temperature is 80-110℃, and the drying time is 8-12 hours; The sieve used for sieving has a mesh size of 60.

[0012] Furthermore, the preheating temperature mentioned in steps (2) and (3) is 800-830℃, preferably 800℃, the holding time is 4h, and the heating rate is 3℃ / min.

[0013] The second grinding method involves adding Fe2O3 to the pre-calcined powder at different mass percentages and then performing planetary ball milling. The milling media are zirconium balls and deionized water, with a material-to-water weight ratio of 1:0.9 and a ball-to-material weight ratio of 3:1. The milling speed is 350 r / min and the milling time is 4 h.

[0014] Furthermore, the concentration of the polyvinyl alcohol solution mentioned in step (4) is 5 wt%. The mass-to-volume ratio of ceramic powder to polyvinyl alcohol solution is 18 g: 6 ml; The pressure of the pressed embryo is 4t.

[0015] Furthermore, in step (5), the temperature for discharging the adhesive is 600°C, the holding time is 3 hours, and the heating rate is 2°C / min.

[0016] The powder used for sintering is PbZrO3 powder synthesized at 790℃, which is placed in a sealed zirconia crucible for sintering. The sintering temperature is 1200-1250℃, preferably 1250℃, the holding time is 2h, and the heating rate is 5℃ / min for the first 1000℃ and 3℃ / min for the subsequent 200-250℃.

[0017] Furthermore, step (5) also includes silver burning treatment and polarization treatment of the cooled ceramic sheet.

[0018] Furthermore, the silver firing process includes: polishing both sides of the cooled ceramic sheet to a smooth finish, coating the upper and lower surfaces of the ceramic sheet with silver electrodes by screen printing, and then firing the silver at 700°C for 15 minutes.

[0019] Furthermore, the polarization process includes: placing the silver-treated ceramic sheet in a 140°C oil bath and applying an alternating voltage of 3 kV / mm, polarizing for 20 minutes, and then letting it stand for 24 hours.

[0020] The beneficial technical effects of this invention are as follows: The Pb provided by this invention 0.94 Ba 0.06 (Zr 0.52 Ti 0.48 ) 0.94 (Mn 1 / 3 Nb 2 / 3 ) 0.06O3+xwt%Fe2O3 piezoelectric ceramic material was successfully prepared by altering the lattice distortion and phase structure caused by equivalent doping of Ba, Mn, Nb, and Fe, as well as donor-acceptor co-doping. The preparation process is stable, making it a strong candidate material for medical ultrasound transducers. Attached Figure Description

[0021] Figure 1 (a) Pb based piezoelectric ceramic materials prepared in Examples 1-4 0.94 Ba 0.06 (Zr 0.52 Ti 0.48 ) 0.94 (Mn 1 / 3Nb 2 / 3 ) 0.06 XRD pattern of O3+xwt%Fe2O3; (b) Magnified view of the diffraction peaks around 30-32°. Figure 2 Pb based piezoelectric ceramic materials prepared in Examples 1-4 0.94 Ba 0.06 (Zr 0.52 Ti 0.48 ) 0.94 (Mn 1 / 3Nb 2 / 3 ) 0.06 Scanning electron microscopy pattern of O3+xwt%Fe2O3 Figure 3 Pb based piezoelectric ceramic materials prepared in Examples 1-4 0.94 Ba 0.06 (Zr 0.52 Ti 0.48 ) 0.94 (Mn 1 / 3Nb 2 / 3 ) 0.06 Curves showing the mechanical quality factor and piezoelectric coefficient of O3+xwt%Fe2O3 as a function of x. Figure 4 Pb based piezoelectric ceramic materials prepared in Examples 1-4 0.94 Ba 0.06 (Zr 0.52 Ti 0.48 ) 0.94 (Mn 1 / 3Nb 2 / 3 ) 0.06 The dielectric constant (ε) of O3+xwt%Fe2O3 samples with different Fe2O3 doping amounts at a test frequency of 1kHz. r Evolution of dielectric loss (tanδ) with temperature Detailed Implementation

[0022] The present invention will be further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0023] First, this invention discloses a PBZT-based piezoelectric ceramic material for medical ultrasound transducers. The chemical composition of the PBZT-based piezoelectric ceramic material is Pb. 0.94 Ba 0.06 (Zr 0.52 Ti 0.48 ) 0.94 (Mn 1 / 3 Nb 2 / 3 ) 0.06 O3+xwt%Fe2O3, where 0.1≤x≤0.7, and x=0.1, 0.3, 0.5, 0.7.

[0024] This invention selects PBZT, a binary piezoelectric material, as the matrix material and obtains PZT-based piezoelectric materials with excellent electrical properties by co-doping Zr and Ti elements at the B site with Mn, Nb, and Fe. It is believed that Nb... 5+ It enters the B site in the crystal lattice and replaces (Zr, Ti). 4+ Defect dipoles are formed, leading to high-valence substitution and charge compensation for lead vacancies. These defect dipoles contribute to polarization intensity, which in turn contributes to piezoelectric properties. Therefore, the increase in defect dipoles induced by Nb doping helps improve piezoelectric performance. It is believed that Mn... 2+ Replace the B-position (Zr, Ti) 4+ Ions form defect dipoles, undergoing low-valence substitution and charge compensation for oxygen vacancies. These defect dipoles pinnate domain walls, preventing domain flipping, reducing losses, and thus improving the mechanical quality factor. Fe 3+ B-site substitution (Zr, Ti) as acceptor ions enter the crystal lattice 4+ To maintain local charge balance, oxygen vacancies are generated in the crystal lattice, forming defect dipoles. These defect dipoles can strongly pin the domain wall motion, thus giving the material a pronounced "hardening" characteristic. 2+ Radius greater than Pb 2+ When doped, it occupies the A site, causing distortion in the crystal structure. During polarization, it facilitates the 90° rotation of the electric domains, thereby improving the dielectric and piezoelectric properties.

[0025] As x increases, Fe 3+ As the doping amount of ions increases, the pinning effect of the defect dipoles formed on the domain walls is enhanced, leading to an increase in the piezoelectric coefficient and a slight decrease in the mechanical quality factor.

[0026] The piezoelectric coefficient of the PBZT-based piezoelectric ceramic material was tested using a ZJ-6BN quasi-static piezoelectric constant tester from the Institute of Acoustics, Chinese Academy of Sciences. The resonant frequency, anti-resonant frequency, and impedance of the PBZT-based piezoelectric ceramic material were tested using a Tongguo Technology HCT-1821 high and low temperature dielectric testing system. The mechanical quality factor was calculated using resonant and anti-resonant frequencies according to the IEEE standard.

[0027] In some embodiments, the mechanical quality factor of the PBZT-based piezoelectric ceramic material can reach 1197; the piezoelectric coefficient of the PBZT-based piezoelectric ceramic material can reach 397 pC / N; and the Curie temperature of the PBZT-based piezoelectric ceramic material can reach 316°C.

[0028] The following is an exemplary description of the preparation method of the PBZT-based piezoelectric ceramic material for medical ultrasound transducers provided by the present invention, wherein the preparation method of the PBZT-based piezoelectric ceramic material may include the following steps: (1) Pb3O4 powder, BaCO3 powder, ZrO2 powder, TiO2 powder, MnO2 powder and Nb2O5 powder were weighed according to the chemical composition stoichiometry of the above PBZT-based piezoelectric ceramic materials, mixed, dried and sieved to obtain raw material powder; (2) The raw material powder is pre-fired to obtain ceramic powder; (3) The ceramic powder is added to Fe2O3 in different mass percentages and then subjected to secondary grinding, drying and sieving to obtain ceramic powder; (4) The ceramic powder is ground with polyvinyl alcohol solution (granulation) and then pressed into a preform (forming). (5) The ceramic preform is debonded, sintered with powder, and cooled to obtain the PBZT-based piezoelectric ceramic material.

[0029] In some embodiments, the purity of the raw material powders in steps (1) and (3) is: Pb3O4 > 97.3%, ZrO2 > 99.5%, TiO2 > 99.7%, and the purity of the remaining raw materials > 99.9%; the mixing method is planetary ball milling, the ball milling media are zirconium balls and deionized water, wherein the weight ratio of material to water is 1:0.9, the weight ratio of balls to material is 3:1, the ball milling speed is 350 r / min, and the ball milling time is 4 h. The drying temperature is 80-110℃, and the drying time is 8-12 h; the sieve mesh number is 60 mesh.

[0030] In some embodiments, the pre-firing temperature in step (2) is 800-830℃, preferably 800℃, the holding time is 4h, and the heating rate is 3℃ / min. The purpose of pre-firing is to allow the oxides in the components to react fully to form a solid solution, so that the required main crystalline phase can be completely formed during sintering. The pre-firing temperature should not be too high, otherwise the material will be too hard and difficult to crush. The pre-firing temperature should also not be too low, otherwise the reaction will be incomplete and the performance will decrease.

[0031] In some embodiments, the secondary milling in step (3) is planetary ball milling. Fe2O3 is added to the pre-calcined powder in different mass percentages, and then planetary ball milling is performed. The milling media are zirconium balls and deionized water, wherein the weight ratio of material to water is 1:0.9, the weight ratio of balls to material is 3:1, the milling speed is 350 r / min, and the milling time is 4 h. The purpose of the secondary ball milling is to break down the powder, making the pre-calcined powder smaller and more uniform in size, and at the same time improving the surface activity of the pre-calcined powder.

[0032] In some embodiments, the concentration of the polyvinyl alcohol solution in step (4) is 5 wt%. The mass-to-volume ratio of ceramic powder to polyvinyl alcohol solution is 18 g: 6 ml; the pressure of the pressed preform is 4 t. The purpose of granulation is to improve the flowability of the powder, facilitating the next molding step.

[0033] In some embodiments, the temperature for removing the adhesive in step (5) is 600°C, the holding time is 3 hours, and the heating rate is 2°C / min. Removing the adhesive involves expelling the organic binder from the ceramic at a lower temperature to prevent the organic binder from melting during sintering due to rapid heating, which could cause large pores and cracks in the ceramic and lead to deterioration of the piezoelectric ceramic's performance.

[0034] In some embodiments, the powder used for sintering in step (5) is PbZrO3 powder synthesized at 790℃, which is placed in a sealed zirconia crucible for sintering. The sintering temperature is 1200-1250℃, preferably 1250℃, the holding time is 2h, and the heating rate is 5℃ / min for the first 1000℃ and 3℃ / min for the last 200-250℃. The sintering process of piezoelectric ceramics generally results in volume shrinkage, increased density, and enhanced strength. Sintering is an important step in the preparation of piezoelectric ceramic materials. The sintering process has a significant impact on its microstructure, grain size, and internal defects. If the sintering temperature is too high or the holding time is too long, the grains will grow abnormally, and severe lead volatilization will cause the stoichiometric ratio of the ceramic to deviate, thereby reducing the performance of the ceramic material. If the sintering temperature is too low or the holding time is too short, the ceramic material cannot be sufficiently densified, leaving more pores inside the ceramic, which affects the mechanical strength and piezoelectric properties of the material.

[0035] In some embodiments, step (5) further includes silver burning and polarization treatment of the cooled ceramic sheet.

[0036] In some embodiments, the silver-coating process includes: polishing both sides of the cooled ceramic sheet until smooth; coating the upper and lower surfaces of the ceramic sheet with silver electrodes via screen printing; and then firing the silver at 700°C for 15 minutes. To remove impurities and defects from the upper and lower surfaces of the piezoelectric ceramic sheet and ensure surface flatness, the sintered piezoelectric ceramic sheet needs to be polished. The silver coating is a preparation for subsequent polarization.

[0037] In some embodiments, the polarization process includes: placing the silver-calcined ceramic sheet in an oil bath at 140°C and applying an alternating voltage of 3 kV / mm, polarizing for 20 minutes, and then letting it stand for 24 hours. Silver-calcined piezoelectric ceramics only exhibit piezoelectric properties after polarization because the ferroelectric domains of piezoelectric ceramics are isotropically arranged before polarization and do not macroscopically exhibit piezoelectric properties. Polarization causes the ferroelectric domains of the piezoelectric ceramic to align regularly along the electric field direction under the action of a DC voltage, thus allowing the material to exhibit piezoelectric properties. Furthermore, when the external voltage is removed, the spontaneous polarization between the ceramic grains maintains the original electric field direction. The polarization process also has a significant impact on the performance of piezoelectric ceramics. When the polarization electric field is small, the domain deflection is incomplete, resulting in lower piezoelectric performance.

[0038] This invention employs a solid-state sintering method to prepare PBZT-based piezoelectric ceramic materials through steps including batching, mixing, pre-firing, secondary grinding, granulation, molding, debinding, sintering, silver calcination, and polarization treatment. The process is simple, reproducible, and produces materials with excellent and easily controllable properties. Furthermore, the piezoelectric ceramic material provided by this invention has a simple composition and achieves high mechanical quality factor, Curie temperature, and piezoelectric coefficient, making it suitable for applications in medical ultrasound transducers.

[0039] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0040] Example 1

[0041] The PBZT-based piezoelectric ceramic material Pb provided in this embodiment 0.94 Ba 0.06 (Zr 0.52 Ti 0.48 )0.94 (Mn 1 / 3 Nb 2 / 3 ) 0.06 The preparation method of O3+xwt%Fe2O3, x=0.1 includes the following steps: (1) Place the weighed raw materials into a nylon can, use zirconia balls and deionized water as the ball milling media, mix them according to the mass ratio of raw materials:deionized water = 1:0.9 and zirconia balls:raw materials = 3:1, and mix them thoroughly on a planetary ball mill for 4 hours; after drying, pass them through a 60-mesh sieve to obtain raw material powder; (2) The above raw material powder was placed in a 50ml alumina covered crucible and heated to 800℃ in a muffle furnace at a heating rate of 3℃ / min. The temperature was held for 4 hours to obtain ceramic pre-synthesized powder. Fe2O3 powder was added to the obtained ceramic pre-synthesized powder at a ratio of 0.1wt%, and then mixed according to the mass ratio of ceramic pre-synthesized powder:deionized water = 1:0.9 and zirconia balls:ceramic pre-synthesized powder = 3:1. The mixture was further ground on a planetary ball mill for 4 hours and then dried to obtain ceramic powder. (3) 5% PVA binder was added to the ceramic powder to granulate it, and then dried in an oven at 90℃ for 30 min. After passing through a 60-mesh sieve, it was pressed into shape under a pressure of 4t to obtain a ceramic green body. (4) The ceramic blank is heated to 600℃ at a heating rate of 2℃ / min and held for 3 hours to remove the binder; then the ceramic blank after binder removal is embedded in PbZrO3 powder synthesized at 790℃, and then placed in a sealed zirconia saggar for sintering. The sintering temperature is 1250℃, the holding time is 2 hours, and the heating rate is 5℃ / min for the first 1000℃ and 3℃ / min for the last 250℃. Then it is cooled to room temperature in the furnace. After cooling, the ceramic sheet is polished on both sides, ultrasonically cleaned and dried, and then silver electrodes are deposited using screen printing. The sheet is then fired at 700℃ for 15 minutes. The silver-treated ceramic sheet was placed in an oil bath at 140°C and subjected to an alternating voltage of 3 kV / mm. After polarization for 20 minutes, it was allowed to stand for 24 hours to complete the polarization treatment, thus obtaining the PBZT-based piezoelectric ceramic material.

[0042] Example 2

[0043] The preparation method of the PBZT-based piezoelectric ceramic material provided in this embodiment is the same as that in Example 1, with the main difference being that x = 0.3.

[0044] Example 3

[0045] The preparation method of the PBZT-based piezoelectric ceramic material provided in this embodiment is the same as that in Example 1, with the main difference being that x=0.5.

[0046] Example 4

[0047] The preparation method of the PBZT-based piezoelectric ceramic material provided in this embodiment is the same as that in Example 1, with the main difference being that x = 0.7.

[0048] Figure 1 Pb based piezoelectric ceramic materials prepared in Examples 1-4 0.94 Ba 0.06 (Zr 0.52 Ti 0.48 ) 0.94 (Mn 1 / 3Nb 2 / 3 ) 0.06 The XRD patterns of O3+xwt%Fe2O3 showed that all ceramic samples exhibited a single perovskite phase structure. No obvious impurity phase diffraction peaks were observed within the instrument's detection limit, proving that Fe ions were completely dissolved in the PBZT-6MN lattice, forming a homogeneous solid solution. The characteristic diffraction peaks near 30°–32° showed a slight shift with increasing Fe doping concentration. This shift is due to the presence of Fe... 3+ Radius smaller than Zr 4 + Substitution at the B site will lead to shrinkage of the unit cell volume. According to the Bragg equation 2dsinθ=nλ, the decrease in interplanar spacing d causes the diffraction angle 2θ to shift to higher angles.

[0049] Figure 2 Pb based piezoelectric ceramic materials prepared in Examples 1-4 0.94 Ba 0.06 (Zr 0.52 Ti 0.48 ) 0.94 (Mn 1 / 3Nb 2 / 3 ) 0.06 Scanning electron microscopy (SEM) images of O3+xwt%Fe2O3 show that all samples exhibit clear grain boundaries and a relatively dense microstructure. The grain size initially increases and then decreases with increasing Fe content, reaching its maximum at x=0.5.

[0050] Figure 3 Pb based piezoelectric ceramic materials prepared in Examples 1-4 0.94 Ba 0.06 (Zr 0.52 Ti 0.48 ) 0.94 (Mn 1 / 3Nb 2 / 3 ) 0.06The graph shows the mechanical quality factor and piezoelectric coefficient of O3+xwt%Fe2O3 as a function of x. It can be seen from the graph that the piezoelectric coefficient first increases and then decreases, reaching a maximum value of 397 at x=0.5. Within the range of x from 0.1 to 0.5, Q... m It remains at a high level, which is the most obvious modification effect achieved by Fe doping. High Q m This means that the material has low mechanical energy loss in the resonant state, and when x increases to 0.7, Q... m The significant decrease indicates that the material is gradually transitioning from a "hard" state to a "soft" state or a high leakage conductivity state.

[0051] Figure 4 Pb based piezoelectric ceramic materials prepared in Examples 1-4 0.94 Ba 0.06 (Zr 0.52 Ti 0.48 ) 0.94 (Mn 1 / 3Nb 2 / 3 ) 0.06 The dielectric constant (ε) of O3+xwt%Fe2O3 samples with different Fe2O3 doping amounts at a test frequency of 1kHz. r The evolution of dielectric constant (tanδ) with temperature shows that as the doping concentration (x) increases, the dielectric constant first increases and then decreases, reaching its maximum at x=0.5. This trend is similar to the evolution of grain size, mainly attributed to the large, uniformly distributed grains and dense microstructure. The high density, optimized crystallinity, and increased grain size of the sample collectively contribute to the high dielectric constant. Meanwhile, the Curie temperature of the sample is in the range of 313~321℃, and the high Curie temperature is beneficial for the application of this ceramic in the field of medical ultrasonic transducers.

Claims

1. A PBZT-based piezoelectric ceramic material, characterized in that, The chemical composition of the PBZT-based piezoelectric ceramic material is Pb. 0.94 Ba 0.06 (Zr 0.52 Ti 0.48 ) 0.94 (Mn 1 / 3 Nb 2 / 3 ) 0.06 O3+xwt%Fe2O3, where 0.1≤x≤0.7, and x=0.1, 0.3, 0.5, 0.

7.

2. The PBZT-based piezoelectric ceramic material according to claim 1, characterized in that, The mechanical quality factor of the PBZT-based piezoelectric ceramic material can reach 1197. The piezoelectric coefficient of the PBZT-based piezoelectric ceramic material can reach 397 pC / N. The Curie temperature of the PBZT-based piezoelectric ceramic material can reach 316°C.

3. A PBZT-based piezoelectric ceramic for medical ultrasound transducers according to claim 1 or 2, and its preparation method thereof, characterized in that, The preparation method includes the following steps: (1) PBZT-based piezoelectric ceramics were synthesized by traditional solid-state method. Pb3O4 powder, BaCO3 powder, ZrO2 powder, TiO2 powder, MnO2 powder and Nb2O5 powder were weighed according to the chemical composition stoichiometry of the above PBZT-based piezoelectric ceramic materials. The raw material powders were obtained by mixing, drying and sieving. (2) The raw material powder is pre-fired to obtain ceramic powder; (3) The ceramic powder is added to Fe2O3 in different mass percentages and then subjected to secondary grinding, drying and sieving to obtain ceramic powder; (4) The ceramic powder is ground with polyvinyl alcohol solution (granulation) and then pressed into a preform (forming). (5) The ceramic preform is debonded, sintered with powder, and cooled to obtain the PBZT-based piezoelectric ceramic material.

4. The preparation method according to claim 3, characterized in that, The purity of the raw material powders mentioned in steps (1) and (3) is as follows: Pb3O4 > 97.3%, ZrO2 > 99.5%, TiO2 > 99.7%, and the purity of the remaining raw materials > 99.9%. The mixing method is planetary ball milling, with zirconium balls and deionized water as the milling media. The materials are: The water weight ratio was 1:0.9, the ball-to-material weight ratio was 3:1, the ball mill speed was 350 r / min, and the ball milling time was 4 h. The drying temperature is 80-110℃, and the drying time is 8-12 hours; The sieve used for sieving has a mesh size of 60.

5. The preparation method according to claim 3 or 4, characterized in that, The preheating temperature mentioned in steps (2) and (3) is 800-830℃, preferably 800℃, the holding time is 4h, and the heating rate is 3℃ / min. The second milling method involves adding Fe2O3 to the pre-calcined powder at different mass percentages, followed by planetary ball milling. The milling media are zirconium balls and deionized water. The water weight ratio was 1:0.9, the ball-to-material weight ratio was 3:1, the ball mill speed was 350 r / min, and the ball milling time was 4 h.

6. The preparation method according to any one of claims 3-5, characterized in that, The concentration of the polyvinyl alcohol solution mentioned in step (4) is 5 wt%. The mass-to-volume ratio of ceramic powder to polyvinyl alcohol solution is 18 g: 6 ml. The pressure of the pressed embryo is 4t.

7. The preparation method according to any one of claims 3-6, characterized in that, The temperature for discharging adhesive in step (5) is 600℃, the holding time is 3h, and the heating rate is 2℃ / min. The powder used for sintering is PbZrO3 powder synthesized at 790℃, which is placed in a sealed zirconia crucible for sintering. The sintering temperature is 1200-1250℃, preferably 1250℃, the holding time is 2h, and the heating rate is 5℃ / min for the first 1000℃ and 3℃ / min for the subsequent 200-250℃.

8. The preparation method according to any one of claims 3-6, characterized in that, Step (5) also includes silver burning treatment and polarization treatment of the cooled ceramic sheet.

9. The preparation method according to claim 3, characterized in that, The silver firing process includes: polishing both sides of the cooled ceramic sheet until smooth, coating the upper and lower surfaces of the ceramic sheet with silver electrodes by screen printing, and then firing the silver at 700°C for 15 minutes.

10. The preparation method according to claim 3, characterized in that... The polarization process includes: placing the silver-treated ceramic sheet in a 140°C oil bath and applying an alternating voltage of 3 kV / mm, polarizing for 20 minutes and then letting it stand for 24 hours.

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