High-performance piezoelectric ceramic

Abstract

The invention discloses a high-performance piezoelectric ceramic, and belongs to the field of piezoelectric ceramics. The formula of the high-performance piezoelectric ceramic material is Pb (Zr0. 505Ti0. 495) O3-x% Fe2O3, the value ranges of x in the raw material formula are 0.1%, 0.3%, 0.5%, 0.7%, 1% and 1.5%, the piezoelectric ceramic is prepared by adopting a solid-phase ball milling method, and the preparation process comprises the following steps: proportioning, mixing and crushing, pre-pressing, pre-sintering, secondary ball milling, molding, plastic removal, sintering, electrode loading, polarization and measurement. The performance of the material is improved by adding the Fe element, so that the high-performance novel piezoelectric ceramic meets the production requirements.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric ceramics technology, and in particular to a high-performance piezoelectric ceramic. Background Technology

[0002] Piezoelectric ceramics are functional ceramic materials capable of converting mechanical energy into electrical energy and vice versa, belonging to an important branch of electronic ceramics. The piezoelectricity of piezoelectric ceramics stems from the spontaneous polarization characteristics in their crystal structure. Below the Curie temperature, piezoelectric ceramics exhibit ferroelectricity, and their spontaneous polarization direction can be altered by an external electric field. Through DC high-voltage polarization treatment, the internal domains of the ceramic are preferentially oriented along the direction of the electric field, thus exhibiting macroscopic piezoelectricity.

[0003] In recent years, atmospheric pressure cold plasma has attracted attention in new research areas within academia, particularly in biomedical applications. Studies have found that cold plasma at atmospheric pressure possesses superior properties such as low gas temperature and high particle activity. When used medically, cold plasma does not harm human biological tissues. Even when its temperature is slightly above room temperature, it does not cause significant thermal damage. It can even effectively eliminate various bacteria, fungi, and other microorganisms. Cold plasma therapy is used in medical treatments such as hemostasis, wound healing, and tumor treatment, as well as in cosmetic procedures such as facial wrinkle and scar removal.

[0004] Piezoelectric ceramic materials used in cold plasma emitters require high boost ratios and conversion efficiencies, as well as reduced heat loss. Most importantly, they also need high mechanical quality factors, such as Q. m and electromechanical coupling coefficient k p The most important component in a cold plasma emitter is the piezoelectric ceramic transformer. Therefore, to stay ahead in the medical field, further research on piezoelectric ceramic materials is necessary. Summary of the Invention

[0005] The purpose of this invention is to provide a high-performance piezoelectric ceramic to solve the problem of low performance of existing PZT series ceramics.

[0006] To address the aforementioned technical problems, this invention provides a high-performance piezoelectric ceramic.

[0007] The material formula is: Pb(Zr) 0.505 Ti 0.495 The raw material formula is 0.1%, 0.3%, 0.5%, 0.7%, 1%, and 1.5% Fe2O3.

[0008] In one embodiment, it is prepared by the following method:

[0009] The proportions of each component are calculated based on the chemical formula, and the particle size of the raw material does not exceed 2μm.

[0010] Solid-phase ball milling is performed by first stirring the slurry, then ball milling at low speed and then ball milling at high speed. After the ball milling is completed, the slurry is dried for later use.

[0011] The dried slurry is pre-pressed into mixed briquettes and then pre-fired. After pre-firing, it is crushed to obtain PZT powder.

[0012] Six portions of PZT powder, each weighing 100g, were mixed with 0.1%, 0.3%, 0.5%, 0.7%, 1%, and 1.5% Fe₂O₃ by mass, respectively, along with 6g of deionized water, to obtain Fe-doped powder. 3+ The PZT ceramic powder was processed by filling six portions of mixed ceramic slurry into the barrel of a high-efficiency ball mill for secondary refining.

[0013] The refined powder is granulated, the granules are formed into a green body and then plasticized.

[0014] Ceramics are formed by sintering at 1100℃ for 2 hours.

[0015] After sintering, an upper electrode and polarization are performed to form a high-performance piezoelectric ceramic.

[0016] In one embodiment, the volume of the grinding ball accounts for 30%-40% of the total volume of the grinding ball, material, and water, and the weight ratio of the grinding ball, material, and water is 2:1:0.6. The grinding ball is subjected to the combined action of centrifugal force, friction, and gravity generated by the motor, forming collision, cyclic tumbling, and rotation movements, so that the powder in it is subjected to impact and friction grinding, thereby achieving mixing and fine pulverization.

[0017] In one embodiment, the pre-firing is carried out at a temperature lower than the sintering temperature; the pre-firing process is as follows:

[0018] 500℃~600℃: No reaction

[0019] 600℃~700℃: PbO + TiO2 → PbTiO3 (Pb3O4 decomposes into PbO at 630℃)

[0020] 700℃~750℃:PbTiO3+PbO+TiO2→Pb(Zr 1-X Ti X O3

[0021] 750℃~800℃: PbTiO3+Pb(Zr) 1-X Ti X O3→Pb(Zr) 0.5 Ti 0.5 O3

[0022] The pre-firing process is as follows: the pre-pressed block material is placed in an alumina crucible, sealed with a lid, and pre-firing in a muffle furnace at 800°C for 2 hours.

[0023] In one embodiment, the granulation method includes: taking out the refined ceramic slurry from the barrel, ball milling and mixing the ceramic slurry with a polyvinyl alcohol solution accounting for 5% of the material weight until uniform; then feeding the ceramic slurry into a spray granulator, and sieving the resulting powder through a 120-mesh sieve.

[0024] In one embodiment, the forming method includes: loading granulated granules into a steel mold of the desired shape, and using a mold plug under external force, causing the granules to approach each other within the mold and firmly connect the granules together by internal forces, thus forming a blank that maintains the corresponding shape.

[0025] In one embodiment, the plastic removal method includes: loading the billet into a breathable refractory trough plate, pushing it into a plastic removal furnace with an oxygen atmosphere, removing the plastic according to a preset heating curve, the temperature curve being set to heat up to 650°C for 12 hours at a heating rate of 52°C / h and then hold for 2 hours, during which the furnace door is slightly opened, and after the holding period is completed, the power is turned off and the furnace is cooled.

[0026] In one embodiment, the method for adding the electrode includes: ultrasonically cleaning and drying a ceramic sheet, coating both the top and bottom surfaces with silver paste, drying at 80°C, and then holding it at 650°C for 30 minutes to obtain a silver electrode.

[0027] In one embodiment, the polarization method includes: using an oil bath piezoelectric polarization device, immersing a sample coated with a silver electrode in silicone oil for 15 minutes to polarize it, with a polarization electric field of 3 kV / mm; at the start of the polarization test, slowly increasing the voltage so that the voltage increase does not exceed 0.02 kV / second, until the voltage reaches 3 kV.

[0028] This invention provides a high-performance piezoelectric ceramic with the following material formulation: Pb(Zr) 0.505 Ti 0.495 The raw material formulation contains 0.1% Fe₂O₃ (x%), where x ranges from 0.1%, 0.3%, 0.5%, 0.7%, 1%, to 1.5%. The high-performance piezoelectric ceramic of this invention is prepared using a solid-state ball milling method. The preparation process includes: batching, mixing and pulverizing, pre-pressing, pre-firing, secondary ball milling, molding, plastic removal, sintering, electrode application, polarization, and measurement. This invention improves the material's properties by adding Fe, resulting in a high-performance novel piezoelectric ceramic that meets production requirements. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the preparation process of a high-performance piezoelectric ceramic provided by the present invention. Detailed Implementation

[0030] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a further detailed explanation of the high-performance piezoelectric ceramic proposed in this invention. The advantages and features of this invention will become clearer from the following description. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of this invention.

[0031] This invention provides a high-performance piezoelectric ceramic with the following material formulation: Pb(Zr) 0.505 Ti 0.495 The raw material formula is 0.1%, 0.3%, 0.5%, 0.7%, 1%, and 1.5% Fe2O3.

[0032] The manufacturing process of this high-performance piezoelectric ceramic is as follows:

[0033] 1. Ingredients:

[0034] The proportions of each component are calculated based on the chemical formula. In order for the chemical reaction of piezoelectric ceramics to proceed smoothly, the particle size of the raw materials is generally required to be no more than 2μm. For additives added in very small amounts, their fineness is particularly important. Fe element is added using Fe2O3.

[0035] 2. Mixing and grinding:

[0036] The traditional solid-phase ball milling method is used, with the ball volume accounting for 30%-40% of the total volume of the ball, material, and water. The weight ratio of ball, material, and water is 2:1:0.6. The slurry needs to be pre-stirred in a mixing tank for 7 minutes. After low-speed ball milling for 45 seconds, if no abnormalities are found, high-speed ball milling begins. The ball milling time is 12 hours. After ball milling, the slurry is dried for later use. The grinding balls rely on the combined action of centrifugal force, friction, and gravity generated by the motor to create collisions, tumbling, and rotation, causing the powder within to be impacted and ground, thereby achieving mixing and fine pulverization.

[0037] 3. Pre-compression, pre-firing, and secondary ball milling:

[0038] Generally, the mixture is pressed into blocks and then pre-fired. The purpose of pre-pressing is to enhance the contact between material particles, making the raw materials more tightly bound, which is conducive to the reaction between materials and facilitates the formation of diffusion. At the same time, pre-pressing reduces the contact area between the material and air, reducing the volatilization of PbO. This invention pours the powder into a mold and presses it into blocks.

[0039] Pre-firing is a solid-state reaction process carried out at a temperature lower than the sintering temperature. Therefore, it involves allowing diffusion between atoms below the melting point, followed by chemical reactions of various raw materials to ultimately produce the desired product. Pre-firing ensures a thorough and uniform solid-state chemical reaction, forming a solid solution with a fixed composition and establishing the main crystalline phase. It also removes carbon dioxide and moisture from the raw materials, reducing firing shrinkage and deformation of the green body, thus facilitating control of the product's dimensions.

[0040] The pre-firing process is as follows:

[0041] 500℃~600℃: No reaction

[0042] 600℃~700℃: PbO + TiO2 → PbTiO3 (Pb3O4 decomposes into PbO at 630℃)

[0043] 700℃~750℃:PbTiO3+PbO+TiO2→Pb(Zr 1-X Ti X O3

[0044] 750℃~800℃: PbTiO3+Pb(Zr) 1-X Ti X O3→Pb(Zr) 0.5 Ti 0.5 O3

[0045] The pre-firing process of the present invention is as follows: the pre-pressed block material is placed in an alumina crucible, sealed with a lid, and pre-firing in a muffle furnace at 800°C for 2 hours.

[0046] After pre-calcination, the material is crushed to obtain PZT powder. Six portions of 100g each of PZT powder are weighed out. Fe2O3 with a mass fraction of 0.1%, 0.3%, 0.5%, 0.7%, 1%, and 1.5% is added to each portion of PZT powder, along with 6g of deionized water. The mixture is then mixed to obtain Fe-doped powder. 3+ The PZT ceramic powders were designated as No. 1, 2, 3, 4, 5, and 6, respectively. The mixed ceramic slurry was fed into the barrel of a high-efficiency ball mill for secondary refining treatment for 24 hours.

[0047] 4. Granulation:

[0048] In order to improve the flowability and adhesion of the powder, making it easy to fill the mold evenly and fully, and to give the molded blank a certain mechanical strength, prevent cracks in the pressed ceramic blank, and facilitate the demolding of the blank, the refined ceramic slurry is granulated.

[0049] The granulation process of this invention involves taking the refined ceramic slurry out of the feed cylinder, ball milling and mixing the ceramic slurry with approximately 5% PVA solution by weight until homogeneous. The ceramic slurry is then fed into a spray granulator, and the resulting powder is sieved through a 120-mesh screen.

[0050] Spray drying granulation produces spherical granules with good flowability and quality. It also allows for high-volume, continuous, and efficient production with reduced labor intensity and improved working conditions. While suitable for mass production, it is costly in terms of equipment.

[0051] 5. Molding and Delamination:

[0052] Forming involves pressing granules into a green body of the desired shape and specifications, creating conditions for sintering. During forming, granulated granules are loaded into a steel mold of a specific shape. With the aid of a mold stopper, and under external force, the granules move closer together within the mold, and are firmly linked together by internal forces to form a green body maintaining a specific shape. The forming effect depends on the pressure, the flowability of the granules, and the flatness of the mold. The ceramic green body pressed using a benchtop powder press in this invention has a size of [missing information].

[0053] Plastic removal: The formed green body contains a large amount of PVA binder. The presence of this binder causes numerous pores during high-temperature sintering, affecting the mechanical strength and various properties of the green body. Therefore, it is necessary to remove this binder. Plastic removal removes the PVA and moisture added during granulation, which helps eliminate pores in the green body and improves the density of the ceramic.

[0054] The process involves loading the billet into a refractory trough with good air permeability, pushing it into a plastic discharge furnace with a good oxygen atmosphere, and discharging the plastic according to a certain heating curve. The temperature curve is set to heat the billet to 650℃ at a heating rate of 52℃ / h for 12 hours, then hold it at that temperature for 2 hours, during which the furnace door is slightly opened. After the holding period, the power is turned off and the furnace is cooled.

[0055] 6. Sintering:

[0056] Sintering is a process in which atoms between particles diffuse to form compounds at high temperatures. It is also a process of grain boundary movement. Surface diffusion is the primary mass transfer mechanism during sintering. The sintering process is essentially a process of reducing the surface energy of ceramics, and the surface energy of the grains or particles is the driving force behind sintering.

[0057] The sintering temperature in this experiment was 1100℃, and the holding time was 2 hours.

[0058] 7. Upper electrode:

[0059] Piezoelectric ceramics are insulators, so a conductive metal layer needs to be coated on both the top and bottom surfaces before polarization. Silver is the most commonly used ceramic electrode. After ultrasonic cleaning and drying, silver paste is coated on both the top and bottom surfaces. After drying at 80°C, the silver electrode is obtained by holding it at 650°C for 30 minutes.

[0060] 8. Polarization:

[0061] The purpose of polarization is to orient the domains of piezoelectric ceramics along the direction of a strong DC electric field, thus exhibiting polarity and the piezoelectric effect. The conditions for polarization are polarization voltage, temperature, and time. The magnitude of the polarization voltage (kV) depends on the coercive field EC of the piezoelectric ceramic, and is generally 2-3 times EC. Generally, the higher the voltage, the more complete the polarization. Under the condition of a fixed polarization electric field and polarization time, a higher polarization temperature facilitates domain orientation and is beneficial for polarization. A longer polarization time results in more complete domain orientation and is conducive to stress relaxation during polarization.

[0062] The polarization experimental apparatus used in this invention is an oil bath piezoelectric polarization device. The sample coated with silver electrodes is placed in silicone oil for polarization for 15 minutes, and the polarization electric field is 3 kV / mm. At the beginning of the polarization test, the voltage is slowly increased so that the voltage increase does not exceed 0.02 kV / second, until the voltage reaches 3 kV.

[0063] 9. Measurement of piezoelectric properties:

[0064] Measuring the piezoelectric constant d 33 Electromechanical coupling coefficient kp, relative permittivity Mechanical quality factors such as Qm and loss tanδ.

[0065] The experimental results are shown in Table 1:

[0066] Table 1 shows the external dimensions. Wafer measurement results

[0067]

[0068]

[0069] The preparation method described in this invention, in which PZT is doped with 0.5% Fe2O3, exhibits the best overall dielectric and piezoelectric properties.

[0070] The preparation process of this method is consistent with the traditional solid-state grinding method. The preparation method is simple and mature, and the piezoelectric constant d at room temperature is obtained. 33 The electromechanical coupling coefficient is 333 pc / N, the relative permittivity εT r3 is 1475, and the mechanical quality factor Q is 1475. m=1807, dielectric loss tanδ=1.42%, can be used as a ceramic material for cold plasma emitters in the field of biomedical aesthetics.

[0071] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. A high-performance piezoelectric ceramic, characterized in that, The material formula is: Pb(Zr) 0.505 Ti 0.495 The raw material formula is 0.1%, 0.3%, 0.5%, 0.7%, 1%, and 1.5% Fe2O3.

2. The high-performance piezoelectric ceramic as described in claim 1, characterized in that, It is prepared by the following method: The proportions of each component are calculated based on the chemical formula, and the particle size of the raw material does not exceed 2μm. Solid-phase ball milling is performed by first stirring the slurry, then ball milling at low speed and then ball milling at high speed. After the ball milling is completed, the slurry is dried for later use. The dried slurry is pre-pressed into mixed briquettes and then pre-fired. After pre-firing, it is crushed to obtain PZT powder. Six portions of PZT powder, each weighing 100g, were mixed with 0.1%, 0.3%, 0.5%, 0.7%, 1%, and 1.5% Fe₂O₃ by mass, respectively, along with 6g of deionized water, to obtain Fe-doped powder. 3+ The PZT ceramic powder was processed by filling six portions of mixed ceramic slurry into the barrel of a high-efficiency ball mill for secondary refining. The refined powder is granulated, the granules are formed into a green body and then plasticized. Ceramics are formed by sintering at 1100℃ for 2 hours. After sintering, an upper electrode and polarization are performed to form a high-performance piezoelectric ceramic.

3. The high-performance piezoelectric ceramic as described in claim 2, characterized in that, The volume of the grinding ball accounts for 30%-40% of the total volume of the grinding ball, material, and water, and the weight ratio of the grinding ball, material, and water is 2:1:0.

6. The grinding ball is generated by the combined action of centrifugal force, friction, and gravity generated by the motor, forming collision, cyclic tumbling, and rotation movements, so that the powder in it is subjected to impact and friction grinding, thereby achieving mixing and fine pulverization.

4. The high-performance piezoelectric ceramic as described in claim 2, characterized in that, The pre-firing is carried out at a temperature lower than the sintering temperature; the pre-firing process is as follows: 500℃~600℃: No reaction 600℃~700℃: PbO + TiO2 → PbTiO3 (Pb3O4 decomposes into PbO at 630℃) 700℃~750℃:PbTiO3+PbO+TiO2→Pb(Zr) 1-X Ti x O3 750℃~800℃:PbTiO3+Pb(Z r-X You X )O3→Pb(Zr 0.5 You 0.5 )O3 The pre-firing process is as follows: the pre-pressed block material is placed in an alumina crucible, sealed with a lid, and pre-firing in a muffle furnace at 800°C for 2 hours.

5. The high-performance piezoelectric ceramic as described in claim 2, characterized in that, The granulation method includes: taking out the refined ceramic slurry from the barrel, ball milling and mixing the ceramic slurry with a polyvinyl alcohol solution accounting for 5% of the material weight until uniform; then feeding the ceramic slurry into a spray granulator, and sieving the prepared powder through a 120-mesh sieve.

6. The high-performance piezoelectric ceramic as described in claim 2, characterized in that, The forming method includes: loading granulated granules into a steel mold of the desired shape; with the help of a mold plug under external force, the granules move closer to each other in the mold and are firmly linked together by internal forces to form a blank that maintains the corresponding shape.

7. The high-performance piezoelectric ceramic as described in claim 2, characterized in that, The method of removing plastic includes: loading the billet into a breathable refractory trough plate, pushing it into a plastic removal furnace with an oxygen atmosphere, removing plastic according to a preset heating curve, the temperature curve being set to heat up to 650℃ for 12 hours at a heating rate of 52℃ / h and then hold for 2 hours, during which the furnace door is slightly opened, and after the holding is completed, the power is turned off and the furnace is cooled.

8. The high-performance piezoelectric ceramic as described in claim 2, characterized in that, The method for applying the upper electrode includes: ultrasonically cleaning and drying a ceramic sheet, coating both the top and bottom surfaces with silver paste, drying at 80°C, and then holding at 650°C for 30 minutes to obtain a silver electrode.

9. The high-performance piezoelectric ceramic as described in claim 2, characterized in that, The polarization method includes: using an oil bath piezoelectric polarization device, immersing the sample coated with silver electrodes in silicone oil for 15 minutes to polarize, with a polarization electric field of 3kV / mm; at the start of the polarization test, slowly increasing the voltage so that the voltage increase does not exceed 0.02kV / second, until the voltage reaches 3kV.

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