Textured porous ceramic with low acoustic impedance and high piezoelectric property as well as preparation and polarization method of textured porous ceramic
Low acoustic impedance high voltage textured porous ceramics were prepared by using a pore-forming agent combustion method and a vacuum negative pressure silicone oil infiltration polarization method. This solved the problems of acoustic impedance mismatch and insufficient polarization in porous piezoelectric ceramics, and improved the piezoelectric performance and polarization stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-18
- Publication Date
- 2026-03-13
AI Technical Summary
Existing piezoelectric ceramics suffer from acoustic impedance mismatch, insufficient polarization, and decreased piezoelectric performance in porous structures, making it difficult to simultaneously achieve low acoustic impedance, high piezoelectric performance, and good polarization stability.
Air/ceramic composite porous structures were prepared by pore-forming agent combustion method. By combining texturing technology and vacuum negative pressure silicone oil infiltration polarization method, low acoustic impedance high voltage textured porous ceramics were prepared. The porous structure was constructed by pore-forming agent combustion method and silicone oil was infiltrated before polarization to avoid electric field breakdown and ensure polarization stability.
Significantly reducing material density and acoustic impedance, improving piezoelectric properties, enhancing polarization efficiency and safety, and enabling high-performance applications of porous ceramics.
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Figure CN121651986A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of ceramic materials technology, and in particular to a low acoustic impedance, high voltage-performance textured porous ceramic and its preparation and polarization method. Background Technology
[0002] Piezoelectric ceramics, due to their excellent electromechanical conversion properties, are widely used in the field of ultrasonic transducers, playing an important role in medical ultrasound imaging, underwater acoustic detection, and non-destructive testing. As the core functional material of ultrasonic transducers, the comprehensive performance of piezoelectric ceramics directly determines the transducer's bandwidth, sensitivity, and signal-to-noise ratio.
[0003] Most commercially available piezoelectric ceramics have a dense structure and generally high acoustic impedance. This results in a serious acoustic impedance mismatch with application media such as water and biological tissues, leading to reduced acoustic energy transmission efficiency and low hydrostatic pressure quality factor, thus limiting their further application in the field of high-precision ultrasonic detection.
[0004] Introducing pores into piezoelectric ceramics to form a porous structure can effectively reduce material density and acoustic impedance, while simultaneously decreasing the dielectric constant, thereby significantly improving the hydrostatic quality factor. This makes porous piezoelectric ceramics an effective way to improve acoustic matching performance. However, with increasing porosity, the effective piezoelectric phase volume fraction in porous piezoelectric ceramics decreases, and its piezoelectric constant decreases significantly, leading to a reduction in transducer sensitivity.
[0005] Texturing techniques, by controlling the microstructure of piezoelectric ceramics, enable grains to grow in a preferred orientation along specific crystal directions, thereby significantly improving the intrinsic piezoelectric properties of the material. Studies have shown that the piezoelectric properties of textured piezoelectric ceramics can approach or even reach the level of single crystals. However, most existing textured piezoelectric ceramics have a dense structure, and effectively introducing texturing techniques into porous piezoelectric ceramic systems still faces the following challenges:
[0006] (1) The pore-forming agent is easily corroded and destroyed by organic solvents during the casting process, resulting in the loss of control of the pore structure;
[0007] (2) The presence of pores makes it easy for electric field breakdown and leakage current to occur during polarization, resulting in insufficient polarization;
[0008] (3) It remains difficult to achieve high orientation, high electrical performance and low acoustic impedance simultaneously in porous systems.
[0009] Therefore, there is an urgent need for a textured porous piezoelectric ceramic material that combines low acoustic impedance, high piezoelectric performance, and good polarization stability, as well as its preparation and polarization methods. Summary of the Invention
[0010] This invention addresses the problem of severe acoustic impedance mismatch between the key sound-generating material and the medium in existing piezoelectric ultrasonic transducers. It develops porous piezoelectric ceramics that combine air and ceramics by using a pore-forming agent combustion method to achieve control over acoustic impedance characteristics. Furthermore, it employs piezoelectric ceramic texture technology, combined with a method of fully polarizing the material by allowing vacuum negative pressure silicone oil to penetrate the material pores before polarization, thereby solving the problem of low piezoelectric performance of porous ceramics.
[0011] To solve the above-mentioned technical problems, the present invention provides a low acoustic impedance high voltage textured porous ceramic with the chemical formula (Ba). x Ca 1-x (Zr) y Ti 1-y O3-2mol%M, where M is a combustion aid, and 0.8 <x<1,0.8<y<1,0<z<3。
[0012] In the aforementioned textured porous ceramics, the sintering aid M is LiCO3 or CuO.
[0013] In the aforementioned textured porous ceramics, the textured porous ceramics are prepared by a pore-forming agent combustion method.
[0014] In the aforementioned textured porous ceramics, the pore-forming agent includes, but is not limited to, polymethyl methacrylate, polyethylene oxide, polyethylene, stearic acid, polystyrene, etc., with a content of 1wt% to 50wt% of the matrix powder and a particle size of 0.1-100μm.
[0015] In the aforementioned textured porous ceramics, the textured porous ceramic material is obtained at a sintering temperature of 1350°C to 1650°C, and the textured porous ceramic material is formed along
[001] . c The grains are of preferred orientation, with uniform grain size, consistent porosity, and a preferred orientation degree of over 93%.
[0016] In the aforementioned textured porous ceramics, during the preparation of the textured porous ceramic material casting slurry, a system without xylene or other corrosive pore-forming agent solvents is used, and the pore-forming agent and dispersant such as fish oil are mixed separately, followed by short-time ball milling.
[0017] In the aforementioned textured porous ceramics, before polarization, the textured porous ceramic material is permeated with silicone oil through a vacuum negative pressure process. Since the breakdown field strength of air is only about 30 kV / cm, filling the pores with silicone oil can effectively prevent electric field breakdown and reduce leakage current caused by the pore structure.
[0018] This invention also provides a method for preparing and polarizing low acoustic impedance high voltage textured porous ceramics, comprising the following steps:
[0019] 1) According to the general chemical formula (Ba x Ca 1-x(Zr) y Ti 1-y Weigh the raw materials, where 0.8 < x < 1, 0.8 < y < 1, 0 < z < 3, and M is a sintering aid;
[0020] 2) After the raw materials are first ball-milled and mixed, they are pre-calcined to obtain perovskite phase matrix fine powder. Then, a calcination aid is added and the mixture is ball-milled a second time to obtain doped matrix fine powder.
[0021] 3) A casting slurry is prepared using a casting solvent system that does not corrode the pore-forming agent. The pore-forming agent and dispersant are mixed separately and ball-milled for a short time. Then, they are mixed with the matrix fine powder and BaTiO3 plate-shaped seed crystal template to obtain a uniform casting slurry.
[0022] 4) The cast slurry is cast, dried, cut and stacked, and then hot-pressed at a lower temperature and pressure to obtain a green preform;
[0023] 5) The green embryo is subjected to pore-forming agent combustion removal and high-temperature sintering to obtain a grain-like structure. <001> Textured porous ceramics with preferred crystal orientation;
[0024] 6) Before polarization, the textured porous ceramic is subjected to vacuum negative pressure treatment to allow silicone oil to penetrate into its pores, and then a DC electric field is applied for polarization treatment.
[0025] Compared with the prior art, the present invention has at least the following beneficial effects:
[0026] 1) Balancing low acoustic impedance and high voltage performance, an air / ceramic composite porous structure is constructed using a pore-forming agent combustion method, effectively reducing material density and acoustic impedance; simultaneously, texturing technology is introduced to allow grains to grow along... <001> Highly preferred crystal orientation significantly enhances the piezoelectric properties of porous ceramics.
[0027] 2) Overcoming the piezoelectric performance degradation problem caused by porous structure, the textured grain structure compensates for the reduction of piezoelectric phase caused by the introduction of pores, making the piezoelectric constant of porous ceramics significantly higher than that of ordinary porous ceramics with the same porosity, and even better than that of dense ordinary ceramics.
[0028] 3) To avoid damage to the pore-forming agent during the casting process, a xylene-free casting solvent system that does not corrode the pore-forming agent is used. The pore-forming agent and dispersant are mixed separately and then subjected to short-time ball milling to effectively maintain the integrity of the pore-forming agent and ensure that the pore structure is uniform and controllable.
[0029] 4) Significantly improves the polarization efficiency and safety of porous ceramics. By using vacuum negative pressure before polarization, silicone oil penetrates into the material pores, replacing the air in the pores, significantly increasing the breakdown field strength and reducing leakage current, enabling porous ceramics to achieve full and stable polarization under high electric field.
[0030] 5) The process is controllable and has good repeatability, making it suitable for engineering applications. The preparation method of this invention has a clear process route, a wide parameter range, and good repeatability, making it suitable for the large-scale preparation of key piezoelectric materials for high-performance ultrasonic transducers. Attached Figure Description
[0031] Figure 1 This is the XRD pattern of BCTZ textured porous ceramic;
[0032] Figure 2 This is a SEM image of BCTZ textured porous ceramic after thermal etching;
[0033] Figure 3 This is a PE curve of BCTZ porous ceramics with different pore-forming agent mass ratios. Detailed Implementation
[0034] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
[0035] In the following description, certain specific details are set forth for the purpose of illustrating various disclosed embodiments in order to provide a thorough understanding of the various disclosed embodiments. However, those skilled in the art will recognize that embodiments may be practiced without one or more of these specific details. In other instances, well-known apparatuses, structures, and techniques associated with this application may not have been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments.
[0036] Example 1:
[0037] This embodiment provides a textured porous ceramic material that combines low acoustic impedance and high voltage performance, with the chemical formula (Ba). x Ca 1-x (Zr) y Ti 1-y O3-z mol%M, where M is a sintering aid such as LiCO3 or CuO, and 0.8 <x<1,0.8<y<1,0<z<3。
[0038] This embodiment also provides a method for preparing and polarizing the textured porous ceramic material, which is carried out according to the following steps:
[0039] 1. Preparation of matrix powder
[0040] The target chemical formula for textured porous ceramics is (Ba 0.95 Ca 0.05 (Zr)0.06 Ti 0.94 BaCO3 powder, CaCO3 powder, TiO2 powder, ZrO2 and template seed crystal were weighed based on the stoichiometric ratio of O3.
[0041] BaCO3 powder, CaCO3 powder, TiO2 powder, and ZrO2 were ball-milled for 24 hours at a speed of 320 r / min and then dried to obtain a mixed raw material. The mixed raw material was then pre-calcined at a temperature of 950°C for 90 minutes to obtain a pure perovskite phase matrix fine powder.
[0042] The matrix powder was mixed with sintering aids such as LiCO3 and CuO and then ball-milled a second time to obtain the doped matrix powder.
[0043] II: Preparation of Casting Slurry and Addition of Pore-forming Agent
[0044] Since the organic pore-forming agent for porous ceramics is soluble in xylene, a traditional casting solvent, and water, as a solvent, has high surface tension and easily generates and leaves microbubbles, an equal mass of ethanol is used as a substitute. The fine matrix powder, solvent, plasticizer, and binder are ball-milled and mixed for 12 to 48 hours. At the same time, the pore-forming agent, dispersant, and ethanol are mixed using magnetic stirring.
[0045] The conventional solvent is a xylene-ethanol mixture, the dispersant is melted herring oil, the plasticizer is polyalkylene glycol and butyl benzyl phthalate, and the binder is polyvinyl butyral.
[0046] The matrix powder, pore-forming agent, and a certain volume fraction of BaTiO3 sheet seed template prepared in the laboratory were mixed and then subjected to low-speed ball milling for 12-48 hours to obtain a uniform casting slurry.
[0047] Adjust the height of the squeegee of the casting machine to 0.05-0.5 mm, set the squeegee moving speed to 0.1-5 cm / s, turn on the casting machine and pour the slurry onto the casting machine for casting and shaping. After a short period of standing, the cast film belt is obtained after drying.
[0048] III: Preparation and Polarization Treatment of Textured Porous Ceramics
[0049] Compared to traditional piezoelectric textured ceramic hot pressing molding processes, this method involves adding a pore-forming agent to the system. To prevent the film material from overflowing at the mold edge, the hot pressing temperature and pressure need to be reduced accordingly. The specific process conditions are as follows: the film is cut to the required size and then stacked. Uniaxial hot pressing is then performed at a temperature of 50–80°C and a pressure of 5–50 MPa to finally obtain the preform block.
[0050] The bulk material was placed in a resistance wire furnace. To prevent the pore-forming agent from burning too quickly and causing pore collapse, the sintering furnace program was set to slowly heat to 400–800 °C at a rate of 0.1–0.5 °C / min, followed by a holding time of 1–12 h to ensure complete removal of organic matter from the green body. During the ceramic sintering stage, a crucible was used for covering, and platinum sheets were used to wrap the ceramic to ensure uniform temperature. After sintering at 1350°C–1650°C for 10 min–24 h, the desired product was obtained. <001> Oriented BCTZ textured porous ceramics.
[0051] After depositing gold electrodes on the textured porous ceramic surface by magnetron sputtering, the surface is immersed in silicone oil and vacuum treated at -1 MPa for 5 to 30 minutes to allow the silicone oil to fully penetrate the material pores. Subsequently, the surface is placed directly in a polarization device and DC polarized within an electric field strength range of 10 kV / cm to 70 kV / cm.
[0052] To further illustrate the work of this patent, a detailed description is provided below with reference to the accompanying drawings.
[0053] Figure 1 This refers to the preparation of (Ba) microspheres using polystyrene (PS) microspheres with an average particle size of 10 μm (hereinafter referred to as PS10) as a pore-forming agent. 0.95 Ca 0.05 (Zr) 0.06 Ti 0.94 The X-ray diffraction (XRD) pattern of the O3 textured porous piezoelectric ceramic shows that the ceramic has a low baseline, high diffraction peak intensity, flat baseline, and perfect crystallization. Comparison with the PDF card shows that the BCTZ textured ceramic belongs to the perovskite structure and has a texture degree of 93%.
[0054] The surface morphology of the piezoelectric porous textured ceramic was observed and characterized using scanning electron microscopy (SEM). The porous textured ceramic was prepared using PS10 as a pore-forming agent, and its composition was (Ba... 0.95 Ca 0.05 (Zr) 0.06 Ti 0.94 O3. (e.g.) Figure 2 As shown, the grain size is uniform, the pore distribution is consistent, and most of them grow around the grain boundaries, and the BT template can be clearly observed.
[0055] Measured using a ferroelectric testing system (Ba 0.95 Ca 0.05 (Zr) 0.06 Ti 0.94Ferroelectric properties of O3 porous ceramic samples. Gold was sputtered onto the upper and lower surfaces of the ceramic samples. By varying the magnitude of the applied electric field, the hysteresis loops of the samples under different field strengths could be measured. The polarization intensity P of the ferroelectric material exhibits a nonlinear relationship with the electric field E, showing a hysteresis phenomenon. After one cycle of the electric field, a closed hysteresis loop (PE curve) is formed. Figure 3 The PE curves of BCTZ porous ceramics with different pore-forming agent mass fractions are presented, and the electric field strength was measured at 20 kV / cm. The coercive field E of the BCTZ porous ceramics is also shown. c The value of the polarization electric field hardly changes with the pore-forming agent content, indicating that the required polarization electric field is close to the required value.
[0056] Table 1 lists (Ba 0.95 Ca 0.05 (Zr) 0.06 Ti 0.94 Piezoelectric properties of porous piezoelectric ceramics and textured ceramics under two different treatment conditions. 33 One method involves conventional polarization, while the other involves polarization after silicone oil has penetrated the material's pores under vacuum. The data in the table shows that textured ceramics exhibit significantly improved piezoelectric properties compared to conventional ceramics; the sample polarized after vacuuming and silicone oil penetration demonstrates even higher piezoelectric properties due to more complete polarization.
[0057] Table 1. Piezoelectric constant d of porous ceramics 33
[0058]
[0059] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A textured porous ceramic with low acoustic impedance and high electrical performance, characterized in that: The general chemical formula of this textured porous ceramic is (Ba x Ca 1-x (Zr) y Ti 1-y O3-z mol%M, where M is a combustion aid, and 0.8 <x<1,0.8<y<1,0<z<3。 2. The low acoustic impedance, high voltage electrical performance textured porous ceramic according to claim 1, characterized in that: The sintering aid M is LiCO3 or CuO.
3. The low acoustic impedance, high voltage electrical performance textured porous ceramic according to claim 1, characterized in that: The textured porous ceramic is prepared by a pore-forming agent combustion method.
4. The low acoustic impedance, high voltage electrical performance textured porous ceramic according to claim 1, characterized in that: The pore-forming agent includes, but is not limited to, polymethyl methacrylate, polyethylene oxide, polyethylene, stearic acid, polystyrene, etc., with a content of 1wt% to 50wt% of the matrix powder and a particle size of 0.1-100μm.
5. The low acoustic impedance, high voltage electrical performance textured porous ceramic according to claim 1, characterized in that: The textured porous ceramic is obtained at a sintering temperature of 1350°C to 1650°C, and the textured porous ceramic material is formed along [001]. c The grains are of preferred orientation, with uniform grain size, consistent porosity, and a preferred orientation degree of over 93%.
6. The low acoustic impedance, high voltage electrical performance textured porous ceramic according to claim 1, characterized in that: In the preparation of textured porous ceramic casting slurry, a system of non-corrosive pore-forming agent solvent is used, and the pore-forming agent and dispersant are mixed separately, followed by short-time ball milling.
7. The low acoustic impedance, high voltage electrical performance textured porous ceramic according to claim 1, characterized in that: Before polarization, the textured porous ceramic is subjected to a vacuum negative pressure process to allow silicone oil to penetrate into the material pores. The silicone oil filling of the pores effectively prevents electric field breakdown and reduces leakage current caused by the pore structure.
8. A method for preparing and polarizing textured porous ceramics with low acoustic impedance and high electrical properties, characterized in that, Includes the following steps: 1) According to the general chemical formula (Ba x Ca 1-x (Zr) y Ti 1-y Weigh the raw materials, where 0.8 < x < 1, 0.8 < y < 1, 0 < z < 3, and M is a sintering aid; 2) After the raw materials are first ball-milled and mixed, they are pre-calcined to obtain perovskite phase matrix fine powder. Then, a calcination aid is added and the mixture is ball-milled a second time to obtain doped matrix fine powder. 3) A casting slurry is prepared using a casting solvent system that does not corrode the pore-forming agent. The pore-forming agent and dispersant are mixed separately and ball-milled for a short time. Then, they are mixed with the doped matrix fine powder and BaTiO3 plate-shaped seed crystal template to obtain a uniform casting slurry. 4) The cast slurry is cast, dried, cut and stacked, and then hot-pressed to obtain a raw preform; 5) The green embryo is subjected to combustion to remove the pore-forming agent and high-temperature sintering to obtain a grain-like structure. <001> Textured porous ceramics with preferred crystal orientation; 6) After depositing gold electrodes on the textured porous ceramic surface by magnetron sputtering, the surface is immersed in silicone oil and subjected to vacuum negative pressure treatment to allow the silicone oil to penetrate into its pores. Then, a DC electric field is applied for polarization treatment.