A piezoelectric ceramic, its preparation method and application

Abstract

A piezoelectric ceramic, a preparation method thereof and an application thereof, which relate to the field of piezoelectric ceramics. This method is different from the two-step sintering process of traditional sintering processes. By effectively controlling the changes in sintering temperature and holding time and the formula of raw materials, the densification sintering of lead-free piezoelectric ceramics is achieved; the piezoelectric ceramic preparation method provided in this application reduces the volatilization of alkali metal elements such as K and Na at high temperatures, is beneficial to the stability of the formula stoichiometry, reduces the generation of impurity phases, and thus improves the density and process stability of the ceramics; the piezoelectric ceramics of this application have high piezoelectric performance, density and mechanical properties, and at the same time are environmentally friendly; the piezoelectric ceramics provided by the present invention have broad application prospects and can be applied to a fiber scanner in the field of laser display and configured as an actuator. The actuator utilizes the inverse piezoelectric effect of the piezoelectric ceramic to control the vibration scanning of the optical fiber on the actuator, thereby realizing laser scanning imaging.

Description

Technical Field

[0001] The present invention relates to the field of piezoelectric ceramics, and in particular, to a piezoelectric ceramic, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, due to their excellent ferroelectric and piezoelectric properties, piezoelectric ceramics have been widely used in fields such as machinery and the electronics industry. Traditional lead zirconate titanate (PZT)-based piezoelectric ceramics have excellent piezoelectric properties and can be doped and modified to adjust device performance to meet different requirements, and are currently the most widely used piezoelectric ceramics. However, the content of lead oxide in these lead-based piezoelectric ceramic materials accounts for about 70% of the total raw materials, and it will cause serious harm to humans and the ecological environment during production, use, and post-disposal processes. In recent years, countries around the world have legislated to prohibit the use of lead-containing electronic materials. For example, the decree on "Restriction of Hazardous Substances in Electrical and Electronic Equipment" (WEEE) passed by the European Parliament, the "Household Electronics Recycling Act" passed by Japan, and the "Administrative Measures for Pollution Prevention and Control of Electronic Information Products" issued by the Ministry of Information Industry of China in 2006 have all strictly limited the content of harmful substances such as lead in electronic devices. Therefore, the research and development of new environmentally friendly lead-free piezoelectric ceramic materials that can replace lead-based piezoelectric ceramics has become one of the research hotspots in the field of piezoelectric ceramics worldwide.

[0003] Currently, lead-free piezoelectric ceramics can be mainly divided into three structures, namely perovskite structure, tungsten bronze structure, and bismuth layer structure. Among them, perovskite structure piezoelectric ceramics have become the most widely studied type of lead-free piezoelectric ceramics due to their excellent piezoelectric properties and the compatibility of the preparation process with traditional lead-based ceramic processes. Common perovskite structure lead-free piezoelectric ceramics mainly include BT-based, sodium bismuth titanate (Bi 0.5 Na 0.5 TiO3, BNT)-based, and potassium sodium niobate (K 0.5 Na 0.5 NbO3, KNN)-based systems. Among them, the Curie temperature of BT piezoelectric ceramics is relatively low (T C ≈120 °C), and the sintering temperature is high (about 1350 °C). Currently, it is more used in dielectric materials due to its high dielectric performance characteristics; BNT ceramics are limited in further applications due to a large coercive field at room temperature (Ec≈73 kV / cm) and a relatively low depolarization temperature (about 100 °C); while KNN-based lead-free piezoelectric ceramics are considered to be the most likely lead-free piezoelectric ceramic system to replace PZT-based piezoelectric ceramics due to their relatively high piezoelectric properties and Curie temperature (T C ≈410 °C).

[0004] However, the existing KNN-based lead-free piezoelectric ceramics have the disadvantages of "relatively low piezoelectric performance, density, and material stability". Summary of the Invention

[0005] An object of the present invention is to provide a piezoelectric ceramic having high piezoelectric properties, density, and mechanical properties, and also having environmental friendliness.

[0006] Another object of the present invention is to provide a method for preparing a piezoelectric ceramic. The preparation process is simple and energy-consuming. The two-step sintering process adopted is different from the traditional sintering process. By controlling the changes in sintering temperature and holding time, densification sintering of the piezoelectric ceramic can be achieved. At the same time, complex sintering equipment such as hot pressing sintering and plasma sintering is not required, and densification sintering can be achieved with an ordinary sintering furnace, reducing equipment costs and facilitating industrial production. In addition, the method for preparing a piezoelectric ceramic according to the present invention reduces the volatilization of alkali metal elements such as K and Na at high temperatures, is conducive to the stability of the formulation stoichiometry, reduces the generation of impurity phases, and thus improves the density and process stability of the ceramic.

[0007] Another object of the present invention is to provide an application of a piezoelectric ceramic. It is applied to the field of laser display technology and is configured as an actuator in a laser display device.

[0008] The present invention solves its technical problems by adopting the following technical solutions.

[0009] The present invention provides a method for preparing a piezoelectric ceramic, which includes the following steps:

[0010] Ingredient preparation: Select raw materials and calculate and prepare ingredients according to the chemical formula (0.96)[K 0.48 Na 0.52 Nb 0.949 Li 0.001 Sb 0.05 O3]-0.04[Bi 0.5 (K 0.15 Na 0.85 ) 0.5 Zr (x) Hf (1-x) O3], to obtain a first raw material; wherein, x = 0.05 - 0.35;

[0011] Ball milling: Perform ball milling on the first raw material to obtain a first sample;

[0012] Pre-sintering: Keep the first sample at 850 - 950 °C for 6 - 10 h to obtain a second sample;

[0013] Forming: Perform forming processing on the second sample according to the target forming shape to obtain a formed third sample;

[0014] Debinding: Keep the third sample at 500 - 950 °C for debinding to obtain a fourth sample;

[0015] Sintering: Sinter the fourth sample to obtain the fifth sample;

[0016] Silver electrode coating: Brush silver paste on the upper and lower surfaces of the fifth sample, and then keep it at 500 - 900 °C for 10 - 40 min to obtain the sixth sample;

[0017] High - voltage polarization: Place the sixth sample in a constant - temperature environment of 20 - 90 °C, apply a high voltage of 2 - 4 kV for polarization, and the pressure - holding time is 15 - 30 min.

[0018] Optionally, in a preferred embodiment of the present invention, the third sample is a piezoelectric ceramic sheet;

[0019] The forming process of the piezoelectric ceramic sheet includes: After grinding the second sample, granulation and tabletting are carried out in sequence to obtain the third sample.

[0020] Preferably, in a preferred embodiment of the present invention, a polyvinyl alcohol solution with a mass fraction of 5 - 12% of binder is added during granulation after grinding the second sample.

[0021] Further, in a preferred embodiment of the present invention, the sintering process of the piezoelectric ceramic sheet includes: Keep the fourth sample at 1100 - 1200 °C for 1 - 15 min, then cool it down to 900 - 1060 °C, and keep it at this temperature for 3 - 25 h to obtain the fifth sample.

[0022] Even further, in a preferred embodiment of the present invention, during the process of cooling down to 900 - 1060 °C, the cooling rate is 5 - 20 °C / min.

[0023] Optionally, in a preferred embodiment of the present invention, x = 0.05 - 0.25.

[0024] Optionally, in a preferred embodiment of the present invention, x = 0.15.

[0025] Further optionally, in a preferred embodiment of the present invention, when carrying out ball - milling treatment on the first sample, anhydrous ethanol is first added to the first sample and then ball - milling treatment is carried out. The ball - milling time is 8 - 24 h, and the rotation speed of the ball mill is 150 - 500 r / min;

[0026] The preparation method of the piezoelectric ceramic further includes: Aging the piezoelectric ceramic obtained after high - voltage polarization at room temperature for 24 hours, and then carrying out performance testing.

[0027] The present invention also provides a piezoelectric ceramic, which is prepared according to the above - mentioned preparation method of the piezoelectric ceramic.

[0028] The present invention also provides an application of a piezoelectric ceramic as described above. The piezoelectric ceramic is applied to the field of display technology, and the display technology field is the field of laser display technology;

[0029] The laser display technology includes a laser display device. The laser display device includes an optical fiber scanner. The optical fiber scanner includes an actuating part, and the piezoelectric ceramic is configured as the actuating part.

[0030] The beneficial effects of the piezoelectric ceramic, its preparation method and application provided by the embodiments of the present invention are as follows: The preparation method of the piezoelectric ceramic provided by the embodiments of the present invention has a simple preparation process and low energy consumption. The two-step sintering process adopted is different from the traditional sintering process. By controlling the changes in sintering temperature and holding time, the densification sintering of the piezoelectric ceramic can be realized. At the same time, complex sintering equipment such as hot pressing sintering and plasma sintering is not required, and densification sintering can be achieved with an ordinary sintering furnace, reducing the equipment cost and being conducive to industrial production; In addition, the preparation method of the piezoelectric ceramic provided by the embodiments of the present invention reduces the volatilization of alkali metal elements such as K and Na at high temperatures, is conducive to the stability of the formula stoichiometry ratio, reduces the generation of impurity phases, and thus improves the density and process stability of the ceramic; The piezoelectric ceramic provided by the present invention has high piezoelectric properties, density and mechanical properties, and also has environmental friendliness; When the piezoelectric ceramic provided by the present invention is applied to the field of laser display technology, it can be configured as an actuator in a laser scanning device, has good piezoelectric driving performance and stability, and has good and broad application prospects. Description of the Drawings

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, so they should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can also be obtained based on these drawings without creative efforts.

[0032] Figure 1 XRD pattern of the KNNLS-BKNZxH(1-x) based piezoelectric ceramic provided by the embodiment of the present invention;

[0033] Figure 2 SEM image of the KNNLS-BKNZxH(1-x) based piezoelectric ceramic provided by the embodiment of the present invention;

[0034] Figure 3 Piezoelectric performance d of the KNNLS-BKNZxH(1-x) based piezoelectric ceramic provided by the embodiment of the present invention 33 and Curie temperature T C ;

[0035] FIG. 4 is the temperature dependence of dielectric permittivity of the KNNLS-BKNZxH(1-x) based piezoelectric ceramics provided by the embodiment of the present invention, where Figure 4a , Figure 4b , Figure 4c and Figure 4d respectively represent the temperature dependence of dielectric permittivity of the KNNLS-BKNZxH(1-x) piezoelectric ceramics when x is 0.05, 0.15, 0.25, and 0.35;

[0036] Figure 5 are the dielectric loss and dielectric constant of the KNNLS-BKNZxH(1-x) piezoelectric ceramics provided by the embodiment of the present invention;

[0037] Figure 6 are the mechanical quality factor and electromechanical coupling coefficient of the KNNLS-BKNZxH(1-x) piezoelectric ceramics provided by the embodiment of the present invention. Detailed implementation manners

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. For those not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturers are followed. The reagents or instruments not specified in the manufacturer are all conventional products that can be obtained through commercial purchase.

[0039] The piezoelectric ceramics, their preparation methods, and applications in the embodiments of the present invention will be specifically described below.

[0040] A preparation method of a piezoelectric ceramic provided by an embodiment of the present invention includes the following steps:

[0041] S1. Batching: Select corresponding raw materials according to the element requirements, and then calculate and batch according to the chemical formula (0.96)[K 0.48 Na 0.52 Nb 0.949 Li 0.001 Sb 0.05 O3]-0.04[Bi 0.5 (K 0.15 Na 0.85 ) 0.5 Zr (x) Hf (1-x) O3] to obtain the first raw material; it should be noted that x in the component [Bi 0.5 (K 0.15 Na 0.85 ) 0.5 Zr (x) Hf (1-x) O3] represents the molar amount of Zr 4+ , and the value range of x is between 0.05 and 0.35. It should be emphasized that [Bi0.5 (K 0.15 Na 0.85 ) 0.5 Zr (x) Hf (1-x) Among the components of [O3], the K element is not necessarily only the K element in other embodiments, and it can also be other alkali metal elements such as sodium and lithium.

[0042] Furthermore, it should be noted that in the embodiments of the present invention, according to the chemical formula (0.96)[K 0.48 Na 0.52 Nb 0.949 Li 0.001 Sb 0.05 O3]-0.04[Bi 0.5 (K 0.15 Na 0.85 ) 0.5 Zr (x) Hf (1-x) O3] when calculating and batching, the purity of the selected raw materials corresponding to each element should be greater than 99%. Optionally, the raw material for providing the K element can be K2CO3, the raw material for providing the Na element can be Na2CO3, the raw material for providing the Nb element can be Nb2O5, the raw material for providing the Li element can be Li2CO3, the raw material for providing the Sb element can be Sb2O3, the raw material for providing the Bi element can be Bi2O3, the raw material for providing the Zr element can be ZrO2, and the raw material for providing the Hf element can be HfO2. It should be emphasized that in other embodiments of the present invention, it is not limited to the raw materials corresponding to each element provided in the embodiments of the present invention, and it can also be other raw materials corresponding to each element, as long as it can provide the corresponding element for the first raw material.

[0043] Optionally, in the preferred embodiments of the present invention, x = 0.05, 0.15, 0.25, and 0.35. It should be noted that in addition to x = 0.05, 0.15, 0.25, and 0.35 in the embodiments of the present invention, in other embodiments of the present invention, x can also be any value between 0.05 and 0.35, such as 0.1, 0.2, and 0.3, etc. It should be emphasized that the preferred range of x in the embodiments of the present invention is 0.05 - 0.15, and the preferred value of x is 0.15.

[0044] Furthermore, for the convenience of explaining the embodiments of the present invention, the chemical formula constructed from the raw material formula provided in the embodiments of the present invention is (0.96)[K 0.48 Na 0.52 Nb 0.949 Li 0.001 Sb 0.05 O3]-0.04[Bi 0.5 (K0.15 Na 0.85 ) 0.5 Zr (x) Hf (1-x) O3], which can be abbreviated as KNNLS - BKNZxH(1 - x). It should be emphasized that by selecting raw materials according to the number of moles during the batching process, the specific formula of the first raw material is controlled from the elements and corresponding ratios, that is, first using Li + 、Sb 5+ elements partially replace Nb in (KNaNbO3) 5+ and then adding a new component BKNZH, thereby improving the piezoelectric properties and temperature stability of the ceramic, realizing the modification of KNN - based piezoelectric ceramics, and forming KNNLS - BKNZxH(1 - x) piezoelectric ceramics, which provides a good material structure basis for the excellent properties of the final piezoelectric ceramics.

[0045] S2. Ball milling: The first raw material is ball - milled to obtain a first sample. It should be noted that by ball - milling the first raw material, the powder dispersibility of the first raw material can be better and the specific surface area can be larger, which is convenient for the next pre - sintering. It should be emphasized that in the preferred embodiment of the present invention, when ball - milling the first sample, anhydrous ethanol is first added to the first sample to fully dissolve and disperse the first raw material, and then ball - milling is carried out. The ball - milling time is limited to 8 - 24 h, and the rotation speed of the ball mill is limited to 150 - 500 revolutions / min to ensure the best ball - milling effect.

[0046] S3. Pre - sintering: The first sample is kept at 850 - 950 °C for 6 - 10 h to obtain a second sample. It should be noted that pre - sintering is a heat treatment process for the first sample, aiming to improve the composition and microstructure of the first sample, which can increase the subsequent processing efficiency and reduce the processing cost.

[0047] S4. Forming: The second sample is formed according to the target forming shape to obtain a formed third sample.

[0048] Optionally, in the preferred embodiment of the present invention, the third sample is a piezoelectric ceramic sheet, that is, the target forming shape is sheet - like. Specifically, the forming process of the piezoelectric ceramic sheet includes: after grinding the second sample, granulation and tableting are carried out in sequence to obtain the third sample. It should be noted that a polyvinyl alcohol solution with a mass fraction of 5 - 12% is added during granulation after grinding the second sample. Adding a binder can help with granulation and tableting. And in other embodiments of the present invention, the binder is not limited to the polyvinyl alcohol solution and can also be other binders.

[0049] It should be further noted that the form of the piezoelectric ceramic provided in the embodiment of the present invention is not only the piezoelectric ceramic sheet as described above, but also other target forming forms, such as a piezoelectric ceramic tube (tubular).

[0050] S5. Debinding: The third sample is kept at 500 - 950 °C for debinding to obtain a fourth sample. It should be noted that the purpose of debinding is to remove various additives during forming, such as the binder polyvinyl alcohol, after forming.

[0051] S6. Sintering: The fourth sample is sintered to obtain a fifth sample. Specifically, when formed into a piezoelectric ceramic sheet, the sintering process of the piezoelectric ceramic sheet includes: keeping the fourth sample at 1100 - 1200 °C for 1 - 15 min, then cooling to 900 - 1060 °C and keeping it for 3 - 25 h to obtain the fifth sample. Among them, during the process of cooling to 900 - 1060 °C, the cooling rate is 5 - 20 °C / min.

[0052] It should be noted that the S6 sintering process is an important link to sinter the fourth sample into porcelain, and its heat preservation parameters and cooling parameters are both important indicators during the sintering process, which determine the essential properties of the fifth sample as a ceramic. In order to optimize and control the good performance of the fifth sample as a piezoelectric ceramic, the embodiment of the present invention requires that during sintering, the cooling rate is limited to 5 - 20 °C / min during the process of cooling to 900 - 1060 °C (this cooling rate can inhibit the grain boundary migration after the formation of a connected skeleton between particles in the ceramic microstructure and make the ceramic sample completely dense by using the grain boundary diffusion effect).

[0053] It is further necessary to emphasize that the above two-step sintering method provided by the embodiment of the present invention has a good advantage over the traditional solid phase method. Specifically, for the traditional solid phase method sintering, since high temperature and long-term heat preservation are required, the pores and grain boundaries can move together, resulting in the gradual growth of the grains and the gradual shrinkage of the pores, thereby improving the density. However, in the later stage of sintering, due to the bridging effect between the grain boundaries, the migration rate of the pores is reduced, and even the phenomenon of being pinned occurs. At this time, the pores leave the grain boundaries and are surrounded by the grains, resulting in the lengthening of the diffusion path of the material and the reduction of the diffusion rate, making it almost impossible to further shrink and eliminate the pores. Further sintering in this case is difficult to improve the density of the ceramic. On the contrary, the grain size will continue to grow, and even a few grains will grow abnormally, so that the residual small pores are more wrapped in the depth of the large grains, which is not good for the performance and use of the ceramic. The two-step sintering of the new process provided by the embodiment of the present invention does not require high temperature and long-term heat preservation, and the abnormal growth of grains can be eliminated. Specifically, the first step of the two-step sintering can achieve a subcritical unstable state of pores in the ceramic, providing an important basic condition for the subsequent second step of low-temperature sintering. However, for the second step of low-temperature sintering, the ceramic particles are "frozen", and the grain boundaries form a "bridge" structure, which restricts the migration of pores and grain boundaries. Under long-term heat preservation, since the activation energy of grain boundary diffusion is less than the activation energy of grain boundary migration, grain boundary diffusion becomes the main mechanism of ceramic densification, which plays an important role in obtaining grains of uniform size.

[0054] S7, silvering the electrode: brush the upper and lower surfaces of the fifth sample with silver paste, and then keep the temperature at 500-900°C for 10-40 minutes to obtain the sixth sample. It should be noted that in other embodiments of the present invention, the electrode can also be silvered by silver layer infiltration, chemical deposition and vacuum coating.

[0055] S8, high voltage polarization: placing the sixth sample in a constant temperature environment of 20-90°C, applying a high voltage of 2-4kV for polarization, and maintaining the voltage for 15-30min. It should be noted that the high voltage polarization makes the electric domains inside the ceramic oriented, thereby maximizing the piezoelectric properties of the ceramic.

[0056] Furthermore, the preparation method of the piezoelectric ceramic provided in the embodiment of the present invention also includes an aging test, that is: the piezoelectric ceramic obtained after high-voltage polarization is aged at room temperature for 24 hours, and then a performance test is performed (after aging is stable, various indicators are tested to see whether the expected performance requirements are met).

[0057] It should be emphasized that in the piezoelectric ceramic preparation method provided by the embodiments of the present invention, for the parameter values involving parameter ranges, they can be any point values within the corresponding parameter ranges, and are not limited to the point values or preferred values exemplified in this embodiment. For example, during the ball milling process, the ball milling time is limited to 8 - 24 h, and the rotational speed of the ball mill is limited to 150 - 500 revolutions per minute. This correspondingly means that the ball milling time can be any duration within the 8 - 24 h interval (such as 8.5 h, 9 h, or 10 h, etc.), and the rotational speed of the ball mill is any rotational speed within the 150 - 500 revolutions per minute parameter interval (such as 160 revolutions per minute, 182 revolutions per minute, 265 revolutions per minute, etc.). It is impossible to list all the point values within the parameter intervals in the embodiments of this application specification. Therefore, the corresponding parameter ranges actually represent each point value within the parameter interval range. Hence, parameter adjustment examples will not be given in full in the embodiment part of this specification.

[0058] The present invention also provides a piezoelectric ceramic, which is prepared according to the piezoelectric ceramic preparation method provided by the above embodiments of the present invention. The piezoelectric ceramic provided by the embodiments of the present invention has high piezoelectric performance, density, and mechanical properties, and also has environmental friendliness.

[0059] The present invention also provides an application of the piezoelectric ceramic as described above. The piezoelectric ceramic is applied to the field of display technology. Optionally, the field of display technology is the field of laser display technology. It should be noted that the laser display technology includes laser display devices, the laser display devices include fiber scanners, the fiber scanners include actuating parts, the piezoelectric ceramic is configured as the actuating part, and the actuating part uses the inverse piezoelectric effect of the piezoelectric ceramic to control the vibration scanning of the optical fiber on the actuating part, thereby realizing laser scanning imaging. It should be noted that the application of the piezoelectric ceramic provided by the embodiments of the present invention is not limited to the actuating part of the fiber scanner provided by the embodiments of the present invention. In other embodiments of the present invention, it can also be applied to components configured in other fields, such as atomizing sheets, as long as they can utilize the piezoelectric effect or inverse piezoelectric effect of the piezoelectric ceramic provided by the embodiments of the present invention.

[0060] The features and properties of the present invention will be further described in detail below in conjunction with embodiments.

[0061] Embodiment 1

[0062] This embodiment provides a method for preparing a piezoelectric ceramic, and its specific preparation process is as follows:

[0063] 1. Batching: According to the selected raw materials and molar masses, in accordance with the formula chemical formula (0.96)[K 0.48 Na 0.52 Nb 0.949 Li 0.001 Sb0.05 [O3]-0.04[Bi 0.5 (K 0.15 Na 0.85 ) 0.5 Zr (x) Hf (1-x) [O3] is calculated and proportioned to obtain the first raw material; where x represents the molar amount of Zr 4+ , and x = 0.05.

[0064] 2. Ball milling: The first raw material is ball milled to obtain the first sample. Specifically, the prepared first raw material is put into a ball mill jar containing ball milling beads, anhydrous ethanol is added, and it is transferred to a ball mill for ball milling. The ball milling time is 8 - 24 hours, and the rotation speed is 150 - 500 revolutions / min.

[0065] 3. Pre - sintering: The first sample is transferred to a muffle furnace, and the program is set to keep warm at 850 - 950 °C for 6 - 10 h to obtain the second sample.

[0066] 4. Granulation and tabletting: The second sample is put into a mortar and finely ground, a binder PVA solution (5 - 12 wt%) is added for granulation, and it is poured into a mold with a diameter of 10 - 15 mm, and tabletted under a pressure of 10 - 20 MPa with a powder tabletting machine to obtain the third sample.

[0067] 5. Debinding: The third sample is transferred to a debinding furnace and kept warm at 500 - 950 °C for debinding to obtain the fourth sample.

[0068] 6. Sintering: The fourth sample is sintered by a two - step sintering method to obtain the fifth sample; specifically, the first - step sintering temperature is 1100 - 1200 °C, keep warm for 1 - 15 min, then quickly cool down to 900 - 1060 °C, and keep warm for 3 - 25 h.

[0069] 7. Silver electrode coating: Silver paste is brushed on the upper and lower surfaces of the fifth sample obtained after sintering, and then kept warm at 500 - 900 °C for 10 - 40 min to obtain the sixth sample;

[0070] 8. High - voltage polarization: The sixth sample is placed in a constant - temperature silicone oil bath at 20 - 90 °C, and a high voltage of 2 - 4 kv is applied for polarization. The pressure - holding time is 15 - 30 min. It should be noted that usually, after polarization, it needs to be aged at room temperature for 24 h before electrical property testing can be carried out.

[0071] This embodiment also provides a piezoelectric ceramic, which is prepared by the preparation method of the piezoelectric ceramic provided in this embodiment.

[0072] This embodiment also provides an application of the piezoelectric ceramic as described above, which is applied to the field of laser display technology. Specifically, the laser display technology includes a laser display device, the laser display device includes an optical fiber scanner, and the optical fiber scanner includes an actuating part, and the actuating part is prepared from the piezoelectric ceramic provided by this embodiment. It should be noted that the actuating part controls the vibration scanning of the optical fiber on the actuating part through the inverse piezoelectric effect principle of the piezoelectric ceramic.

[0073] Embodiment 2

[0074] This embodiment is substantially the same as the piezoelectric ceramic and its preparation method provided in Embodiment 1. The difference is that in the preparation process of the piezoelectric ceramic provided in this embodiment, the ratio of the formula used is different from that in Embodiment 1. In the batching process of this embodiment, the molar amount x of Zr 4+ is 0.15.

[0075] Embodiment 3

[0076] This embodiment is substantially the same as the piezoelectric ceramic and its preparation method provided in Embodiment 1. The difference is that in the preparation process of the piezoelectric ceramic provided in this embodiment, the ratio of the formula used is different from that in Embodiment 1. In the batching process of this embodiment, the molar amount x of Zr 4+ is 0.25.

[0077] Embodiment 4

[0078] This embodiment is substantially the same as the piezoelectric ceramic and its preparation method provided in Embodiment 1. The difference is that in the preparation process of the piezoelectric ceramic provided in this embodiment, the ratio of the formula used is different from that in Embodiment 1. In the batching process of this embodiment, the molar amount x of Zr 4+ is 0.35.

[0079] Furthermore, in order to verify and illustrate the technical effects of the piezoelectric ceramic and its preparation and application provided in the embodiments of the present invention, this application elaborates through some embodiment samples provided by the present invention. Specifically:

[0080] Please refer to Figure 1 , Figure 1 is the XRD pattern of the KNNLS-BKNZxH(1-x)-based lead-free piezoelectric ceramic provided by the embodiment of the present invention. As Figure 1As shown, the KNNLS-BKNZxH(1-x) lead-free piezoelectric ceramics have a single perovskite structure, indicating that the addition of the new component BKNZxH(1-x) makes the ceramics have a stable solid solution. When x = 0.05 and 0.15, the KNNLS-BKNZxH(1-x) piezoelectric ceramics have an R-T multiphase coexisting crystal structure. When x > 0.15, the phase structure of the KNNLS-BKNZxH(1-x) piezoelectric ceramics changes, and the double peak becomes a single peak, mainly showing a rhombohedral phase structure, which indicates that Zr 4+ / Hf + has a great influence on the phase structure of the KNNLS-BKNZxH(1-x) lead-free piezoelectric ceramics. When the KNNLS-BKNZxH(1-x) ceramics have an R-T multiphase coexisting crystal structure (x = 0.05 and 0.15), they have the best piezoelectric properties.

[0081] Furthermore, Figure 2 Figure Figure 2 is the SEM image of the KNNLS-BKNZxH(1-x) lead-free piezoelectric ceramics provided by the embodiment of the present invention. It can be seen from the figure that when x = 0.05 and 0.15, the KNNLS-BKNZxH(1-x) piezoelectric ceramics have a dense crystal structure, mainly composed of large grains of 20-30 microns and small grains filled in the gaps between the large grains. When x > 0.15, the large grains gradually decrease, indicating that as Zr 4+ / Hf + increases, the excess Zr 4+ gradually precipitates onto the grain boundaries, inhibiting the growth of grains.

[0082] Furthermore, Figure 3 Figure Figure 3 is the piezoelectric property d 33 and Curie temperature T C of the KNNLS-BKNZxH(1-x) lead-free piezoelectric ceramics provided by the embodiment of the present invention. From the data in the figure, it can be seen that when x = 0.15, the KNNLS-BKNZxH(1-x) piezoelectric ceramics have the best piezoelectric properties (d 33 = 570±10 pC / N) and a relatively high Curie temperature (T C = 216 °C), which is consistent with the analysis results of XRD and SEM.

[0083] Furthermore, Figure 4 is the dielectric temperature curve (1000 hz) of the KNNLS-BKNZxH(1-x) piezoelectric ceramics provided by the embodiment of the present invention. Through the data of this dielectric temperature curve, the dielectric constant (1000 hz) and dielectric loss of the ceramics can be obtained, that is Figure 5For the dielectric loss and dielectric constant of the KNNLS-BKNZxH(1-x) piezoelectric ceramics provided by the embodiments of the present invention, as can be seen from the figure, when x = 0.15, the piezoelectric ceramics have a relatively high dielectric constant of 3352 and a relatively low dielectric loss of 0.0286.

[0084] Furthermore, Figure 6 For the mechanical quality factor and electromechanical coupling coefficient of the KNNLS-BKNZxH(1-x) piezoelectric ceramics provided by the embodiments of the present invention, as shown in the figure, when x = 0.15, the KNNLS-BKNZxH(1-x) piezoelectric ceramics have the best mechanical properties, that is, Qm = 31, kp = 0.63, which is consistent with the above XRD, SEM and piezoelectric / dielectric property results.

[0085] In summary, the method for preparing piezoelectric ceramics provided by the embodiments of the present invention uses a two-step sintering method different from the traditional sintering method, and prepares KNNLS-BKNZxH(1-x) piezoelectric ceramics by adding a second component. This ceramic has an R-T multiphase coexisting crystal structure at room temperature, a relatively high density, and excellent piezoelectric and mechanical properties: d 33 = 570 ± 10 pC / N, T C = 216 °C, tanδ = 0.0286, ε γ = 3352, Qm = 31, kp = 0.63. These properties can be comparable to those of PZT piezoelectric ceramics. Therefore, it can be judged that this system of lead-free piezoelectric ceramics has good research prospects.

[0086] The above-described embodiments are some embodiments of the present invention, rather than all embodiments. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

Claims

1. A preparation method of piezoelectric ceramics, characterized in that, It includes the following steps: Ingredients: Select raw materials and calculate and prepare ingredients according to the chemical formula (0.96)[K 0.48 Na 0.52 Nb 0.949 Li 0.001 Sb 0.05 O3]-0.04[Bi 0.5 (K 0.15 Na 0.85 ) 0.5 Zr (x) Hf (1-x) O3], and obtain the first raw material; wherein, x = 0.15; Ball milling: Ball mill the first raw material to obtain a first sample; Pre-sintering: Keep the first sample at 850 - 950 °C for 6 - 10 h to obtain a second sample; Forming: Process the second sample according to the target forming shape to obtain a formed third sample; Debinding: Keep the third sample at 500 - 950 °C for debinding to obtain a fourth sample; Sintering: Keep the fourth sample at 1100 - 1200 °C for 1 - 15 min, then cool it down to 900 - 1060 °C and keep it for 3 - 25 h to obtain a fifth sample. Among them, during the process of cooling down to 900 - 1060 °C, the cooling rate is 5 - 20 °C / min; Silver electrode coating: Brush silver paste on the upper and lower surfaces of the fifth sample, and then keep it at 500 - 900 °C for 10 - 40 min to obtain a sixth sample; High - voltage polarization: Place the sixth sample in a constant - temperature environment of 20 - 90 °C, apply a high voltage of 2 - 4 kv for polarization, and the pressure - holding time is 15 - 30 min.

2. The preparation method of the piezoelectric ceramic according to claim 1, characterized in that, The third sample is a piezoelectric ceramic sheet; The forming process of the piezoelectric ceramic sheet includes: After grinding the second sample, granulating and pressing are carried out in sequence to obtain the third sample.

3. The preparation method of the piezoelectric ceramic according to claim 2, wherein, When granulating after grinding the second sample, a polyvinyl alcohol solution with a mass fraction of 5 - 12% is also added as a binder.

4. The preparation method of the piezoelectric ceramic according to claim 1, characterized in that, When ball - milling the first sample, anhydrous ethanol is first added to the first sample and then ball - milling is carried out. The ball - milling time is 8 - 24 h, and the rotation speed of the ball mill is 150 - 500 revolutions per minute; The preparation method of the piezoelectric ceramic also includes: Aging the piezoelectric ceramic obtained after high - voltage polarization at room temperature for 24 hours, and then carrying out performance testing.

5. A piezoelectric ceramic, characterized in that, The piezoelectric ceramic is prepared by the preparation method of the piezoelectric ceramic according to any one of claims 1 - 4.

6. An application of a piezoelectric ceramic as described in claim 5, characterized in that, The piezoelectric ceramic is applied to the display technology field, and the display technology field is the laser display technology field; The laser display technology includes a laser display device. The laser display device includes an optical fiber scanner. The optical fiber scanner includes an actuating part, and the piezoelectric ceramic is configured as the actuating part.

Images