Lead-free piezoelectric ceramic capable of being used for road vibration energy collecting device and preparation method and application of lead-free piezoelectric ceramic

Abstract

The invention provides lead-free piezoelectric ceramic capable of being used for a road vibration energy collecting device and a preparation method and application of the lead-free piezoelectric ceramic, and relates to the technical field of ceramic material preparation. The tabletting ceramic is prepared by the following steps: S1, respectively drying the required raw materials, weighing according to the chemical composition of the piezoelectric ceramic, and mixing to obtain a uniform mixture I; s2, performing primary ball milling, sieving, washing and drying on the mixture I to obtain a mixture II; s3, pre-sintering the mixture II, and then carrying out secondary ball milling to obtain a mixture III; s4, the mixture III is sieved and subjected to centrifugal granulation, then tabletting forming is conducted, and a test piece is obtained; and S5, discharging glue from the test piece, sintering, and carrying out polarization treatment to obtain the lead-free piezoelectric ceramic. The lead-free piezoelectric ceramic material provided by the invention shows excellent piezoelectric property near Curie temperature, and has good dielectric stability and long-term service capability in a road environment.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic material preparation, and in particular to a lead-free piezoelectric ceramic that can be used in a road vibration energy harvesting device, and a preparation method and application thereof. Background Art

[0002] Road vibration energy harvesting technology based on the piezoelectric effect boasts high electromechanical conversion efficiency, a simple structure, and immunity to electromagnetic interference. Furthermore, its use of lead-free, environmentally friendly materials makes it environmentally friendly and pollution-free. It provides stable power for traffic facility monitoring equipment and wireless sensors, ensuring full lifecycle monitoring of traffic facilities in complex service environments. Numerous researchers at home and abroad continue to explore key technologies such as the preparation process of road piezoelectric ceramics, transducer structure design, and energy conversion circuits. However, research on high-performance piezoelectric materials specifically suitable for road piezoelectric energy harvesting is still in its early stages. With the widespread adoption of the lead-free environmental protection concept, lead-free piezoelectric materials show promising development prospects in the field of road vibration energy harvesting. To meet the practical needs of road piezoelectric power generation systems for efficient energy conversion and heavy traffic load conditions, the developed lead-free piezoelectric ceramics must possess excellent mechanical strength, electrical properties, and fatigue stability, placing higher technical demands on the material's comprehensive performance.

[0003] When piezoelectric ceramics are used on a large scale in complex road service environments, two key conditions must be met to achieve optimal power generation performance. (1) The daily operating temperature range of roads is usually -10°C to 80°C. When the ambient temperature exceeds the Curie temperature of the ceramic, its piezoelectric properties will quickly lose value. To ensure the stability of ceramic performance, the Curie temperature is usually required to be at least twice the working ambient temperature. (2) The piezoelectric charge constant is negatively correlated with the Curie temperature, that is, the higher the Curie temperature, the lower the charge constant. Since the piezoelectric charge constant directly affects the power generation efficiency, it is necessary to regulate the Curie temperature of the ceramic to a reasonable level through appropriate element doping, thereby maximizing its piezoelectric charge constant and achieving excellent energy conversion performance. Research on ceramic element doping has been relatively mature, especially in the field of lead-containing piezoelectric materials. However, systematic research on lead-free piezoelectric ceramic formulations under road coupling is still relatively scarce, and related exploration is still in its infancy. Summary of the Invention

[0004] In light of this, the present invention proposes a lead-free piezoelectric ceramic for road vibration energy harvesting devices, as well as its preparation method and application. This material not only meets the durability and mechanical stability requirements of road engineering, but also further optimizes energy conversion efficiency, exhibiting excellent piezoelectric properties, a high electromechanical coupling coefficient, and a large dielectric constant.

[0005] In a first aspect, the present application provides a lead-free piezoelectric ceramic for a road vibration energy harvesting device, the chemical composition of the piezoelectric ceramic comprising: 0.95K 0.48 Na 0.52 Nb 0.96 Sb 0.04 O3-0.05Na 0.5 Bi 0.5×(1+x) ZrO3, wherein the value of x is in the range of -0.03≤x≤0.09.

[0006] Further, the value of x is -0.03, 0, 0.03, 0.06 or 0.09.

[0007] In a second aspect, the present application relates to a preparation method of the above-mentioned lead-free piezoelectric ceramic, comprising the following steps: S1, after drying the required raw materials respectively, weighing and mixing according to the chemical composition of the piezoelectric ceramic to obtain a uniform mixture I; S2, once ball milling, sieving, washing and drying the mixture I to obtain a mixture II; S3, pre-sintering the mixture II, followed by secondary ball milling to obtain a mixture III; S4, sieving the mixture III and centrifugal granulation, followed by tabletting to obtain a test piece; S5, after the test piece is degassed, sintered and polarized to obtain the lead-free piezoelectric ceramic.

[0008] Further, in step S1, the raw materials include but are not limited to K2CO3, Na2CO3, Nb2O5, Sb2O3, Bi2O3 and ZrO2.

[0009] Further, in step S2, the rotation speed of the first ball milling is 200-250 revolutions per minute, and the time is not less than 20h.

[0010] Further, in step S3, the pre-sintering temperature is 850-860℃, and the time is 6-8h.

[0011] Further, in step S4, the centrifugal temperature is 100-120℃, and the centrifugal time is not less than 18h.

[0012] Further, in step S4, the conditions of tabletting include: the initial pressure is 8-10MPa, the time is 25-30s, and the final pressure is 220-230MPa.

[0013] Further, in step S5, the degassing conditions include: the test piece is heated from the initial temperature to 750-800℃ at a rate of 2-4℃ / min, and then cooled to 20-28℃ after holding for 2-3h.

[0014] Furthermore, in step S5, the sintering conditions include: heating the test piece from the initial temperature to 1100-1150°C at a rate of 3-6°C / min, keeping the temperature for 12-14 hours, and then cooling to 20-28°C.

[0015] Furthermore, in step S5, the polarization conditions include: an applied electric field strength of 2-4 kV / mm and a time of 5-25 min.

[0016] In a third aspect, the present invention also relates to the application of the above-mentioned lead-free piezoelectric ceramics that can be used in road vibration energy harvesting devices, that is, after the lead-free piezoelectric ceramics are subjected to patch and curing treatments, a drum-type piezoelectric transducer is prepared.

[0017] The lead-free piezoelectric ceramics of the present invention that can be used in a road vibration energy harvesting device, as well as their preparation method and application, have the following beneficial effects compared to the prior art: The lead-free piezoelectric ceramics prepared by the present invention have excellent electromechanical properties and environmental adaptability.

[0018] The piezoelectric transducer prepared based on lead-free piezoelectric ceramics in the present invention has an open-circuit piezoelectric degradation rate of only 2.9% after 2.1 million continuous loadings under an external load of 80kΩ. It has excellent power generation stability and can meet the long-term service needs of roads, providing strong support for the application of piezoelectric energy capture technology in the transportation field. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 A schematic diagram of the process for preparing a lead-free piezoelectric ceramic formula that can be used in a road vibration energy harvesting device according to the present invention; Figure 2 XRD patterns of the lead-free piezoelectric ceramics used in road vibration energy harvesting devices prepared in Examples 1 to 5 of the present invention; Figure 3 This is an SEM image of the lead-free piezoelectric ceramics used in road vibration energy harvesting devices prepared in Examples 1 to 5 of the present invention; Figure 4 The dielectric temperature diagram of the lead-free piezoelectric ceramics used in the road vibration energy harvesting device prepared in Examples 1 to 5 of the present invention; Figure 5 This is the open-circuit voltage waveform of the lead-free piezoelectric ceramic drum transducer that can be used in a road vibration energy harvesting device prepared in an example of the present invention. DETAILED DESCRIPTION

[0021] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0022] This invention provides a lead-free piezoelectric ceramic that can be used in road vibration energy harvesting devices. This piezoelectric ceramic, based on lead-free piezoelectric materials, utilizes vibration energy harvesting technology. Due to its environmental friendliness, high electromechanical conversion efficiency, simple structure, and immunity to electromagnetic interference, it can provide continuous and environmentally friendly energy support for low-power wireless sensing devices in transportation infrastructure, reducing the potential ecological pollution and health risks associated with the use of traditional lead-containing materials. Furthermore, it effectively alleviates technical bottlenecks faced by monitoring systems in complex environments, such as wiring difficulties, limited energy acquisition, and poor data transmission, thereby enabling green and intelligent upgrades to infrastructure status perception.

[0023] It is well known to those skilled in the art that the Curie temperature (T c ) is the key critical temperature for the transition from ferroelectric phase to paraelectric phase and from trigonal system to tetragonal system in lead-free piezoelectric ceramics, which has a significant impact on the dielectric and piezoelectric properties of the material. During the heating process, the dielectric constant (ε r ) shows a trend of first increasing and then decreasing. At this time, the electric domain activity is enhanced and the migration ability of the domain wall is improved, which is conducive to the polarization process. However, when the temperature exceeds T c When the spontaneous polarization disappears, the material transforms into the paraelectric phase, resulting in a piezoelectric coefficient d 33 The polarization process is essentially a process of orderly arrangement of electric domains, in which the 90° domain reversal requires overcoming a high energy barrier. Prolonging the polarization time helps to improve the orderliness of the domain structure, thereby enhancing the piezoelectric response. The doping of Bi elements will cause lattice distortion and local stress fluctuations, thereby weakening the structural stability of the material and causing T c Therefore, T should be considered comprehensively in material design. c with d 33 to optimize the overall performance.

[0024] The main chemical composition of the lead-free piezoelectric ceramic material provided by the present invention is: 0.95K 0.48 Na 0.52 Nb 0.96 Sb 0.04 O3-0.05Na 0.5Bi 0.5×(1+x) ZrO3. The pressed ceramic is prepared by the following steps: Figure 1 As shown: S1. After the required raw materials are dried separately, they are weighed and mixed according to the chemical composition of the piezoelectric ceramic to obtain a uniform mixture I; S2. The mixture I is ball-milled, sieved, rinsed and dried to obtain a mixture II; S3. The mixture II is pre-sintered, and then ball-milled twice to obtain a mixture III; S4. The mixture III is sieved and centrifuged into granules, and then pressed into tablets to obtain test pieces; S5. The test piece is debinded, sintered, and polarized to obtain a lead-free piezoelectric ceramic.

[0025] The present invention will be further described below with reference to specific examples, but the scope of protection of the present invention is not limited by the following examples. Unless otherwise specified, the materials mainly involved in the following examples are conventional commercial products.

[0026] Example 1 This embodiment provides a lead-free piezoelectric ceramic that can be used in a road vibration energy harvesting device, which is prepared by the following steps: S1, potassium carbonate, sodium carbonate, niobium pentoxide, antimony trioxide, bismuth oxide and zirconium dioxide are placed separately in an electric blast drying oven to remove excess moisture; then 0.95K 0.48 Na 0.52 Nb 0.96 Sb 0.04 O3-0.05Na 0.5 Bi 0.5×(1+x) ZrO3, wherein x = -0.03, weigh the raw materials and mix them evenly to obtain mixed material I; S2. Ball mill the mixture I. Before ball milling, add an appropriate amount of anhydrous ethanol to the ball mill jar and clean it by idling until the liquid becomes transparent. Then, control the speed to 230 rpm and ball mill for 22 h, using intermittent alternation to ensure uniform mixing. After the ball milling is completed, pass it through a 200-mesh sieve, rinse it, collect the slurry, and then dry it at 80°C to obtain mixture II. S3. Sintering the mixture II at 860°C for 7 hours, then taking 3 g of the powder, adding 6 drops of 7% polyvinyl alcohol aqueous solution, zirconium balls and anhydrous ethanol in a ball mill, and performing secondary ball milling. After ball milling for 20 hours, the mixture III was obtained; S4. Pass mixture III through a 300-mesh sieve to remove large particles and ensure material purity, then centrifuge and granulate at 110°C for 18 hours. Weigh 0.25 g of the powder and place it into a 15 mm diameter stainless steel mold. Press the mold under a pressure of 8 MPa for 30 seconds to produce a test piece with a thickness of 2 mm and a diameter of 15 mm. Then, consolidate and compact the piece under a pressure of 225 MPa. S5. Place the test piece in a high-temperature debinding furnace, heat it to 780℃ at a constant speed of 3℃ / min, keep it warm for 2.5 hours and then cool it naturally to room temperature; then heat it to 1150℃ at a rate of 5℃ / min and sinter it for 12 hours, then cool it to room temperature to obtain a lead-free piezoelectric ceramic with a diameter of 15mm; then, wipe the surface of the lead-free piezoelectric ceramic with anhydrous ethanol and polish it with fine sandpaper, then use vertical screen printing technology to evenly apply conductive silver paste, apply twice on each side, after drying, heat it to 680℃ at a rate of 5℃ / min and keep it warm for 30 minutes, then cool it to room temperature, polish the edge and side silver layer of the ceramic to prevent the electrodes on both sides from conducting; finally, apply an external electric field strength of 4 kV / mm and polarize for 15 minutes, let it stand at room temperature for 24 hours to obtain a lead-free piezoelectric ceramic.

[0027] The lead-free piezoelectric ceramics prepared above were subjected to SEM imaging, XRD analysis and ferroelectric property testing.

[0028] The only difference between Examples 2 to 5 and Comparative Examples 1 to 2 and Example 1 is the value of x. The values ​​of x and the performance test results in Examples 2 to 5 and Comparative Examples 1 to 2 are shown in Table 1 below.

[0029] Table 1 The values ​​of x and their performance test results in Examples 1 to 5 and Comparative Examples 1 to 2

[0030] As shown in Table 1, the lead-free piezoelectric ceramics prepared by the present invention and used in road vibration energy harvesting devices have excellent piezoelectric and dielectric properties. d 33 、 K p and Q m The change trend is consistent. The overall trend is first increasing and then decreasing. When x=0.06 d 33 、 K p and Q m All of them reach the maximum value of 530pC / N, 0.655, 35.32, compared with x=0 d 33 、 K p and Q m An increase of 13%, 7.54% and 11.21% respectively.

[0031] It can also be seen from Table 1 that when the non-stoichiometric ratio of Bi is lower than 0, the electrical properties of lead-free piezoelectric ceramics are reduced. Therefore, it can be seen that increasing the content of Bi has a positive effect on improving the performance of Bi-KNNS-NZ piezoelectric ceramics. However, when the non-stoichiometric ratio increases to more than 0.06, the piezoelectric performance of the ceramic decreases. d 33 、 K p and Q m The performance of the piezoelectric ceramics began to decline, and the performance improvement of the piezoelectric ceramics stopped. Therefore, the inventors believe that the electrical performance of the 0.06Bi-KNNS-NZ lead-free piezoelectric ceramics is the best. In contrast, Comparative Examples 1 and 2 show that when the Bi content is too high or too low, the performance does not meet the requirements of Roadfarm.

[0032] Combined with Examples 1 to 5 and Figure 2 It can be seen that different non-stoichiometric ratios of Bi elements do not affect the perovskite structure of the piezoelectric ceramics. In addition, due to the similar characteristics of the lattice parameters, the characteristic diffraction peaks corresponding to the orthorhombic ferroelectric phase and the tetragonal ferroelectric phase partially overlap. From the splitting of the (002) and (200) diffraction peaks, and the increase in the non-stoichiometric ratios of different Bi elements, the intensity changes inside the KNNS-NZ piezoelectric ceramics indicate that the Bi-KNNS-NZ piezoelectric ceramic system has an evolution process of R phase and T phase, and the phase structure of Bi-KNNS-NZ is a typical structural feature of the coexistence of rhombic and tetragonal phases. The results prove that the experimental piezoelectric ceramic material has a good and stable crystal structure, which ensures the piezoelectric performance.

[0033] Combined with Examples 1 to 5 and Figure 3 It can be seen that when the Bi element doping content is low, the crystal structure of the piezoelectric ceramic is relatively loose, the density is low and there are more pores between the crystals; with the increase of Bi element doping, the density between the crystals is improved and the pores become less. When x=0.06, the boundaries between the grains are clearly distinguishable, the particle morphology is regular and full, and there is a rich texture. There are no pores in the sample, and no pyrochlore phase exists. Its microscopic morphology is good, showing an ideal state.

[0034] Combined with Examples 1 to 5 and Figure 4 It can be seen that as the temperature gradient increases, the lead-free piezoelectric ceramics prepared in Examples 1 to 5 all show obvious dielectric anomaly peaks. The corresponding temperature at this time is the Curie temperature of the piezoelectric ceramic test piece, which is also the boundary of the material's transition from ferroelectric phase to paraelectric phase and from rhombohedral phase to tetragonal phase. It can also be seen from the figure that as the temperature increases, the dielectric constant (ε r) first rises and then falls. During the rising phase, as the temperature gradually increases, the activity of the electric domains increases significantly, making the transition easier. When the temperature exceeds a certain critical value, the piezoelectric ceramic material undergoes a transition from a ferroelectric phase to a paraelectric phase, causing a sharp drop in piezoelectric performance and a significant increase in dielectric loss. Furthermore, with increasing Bi doping, the Curie temperature of the piezoelectric ceramic decreases.

[0035] Using Example 4 as an example, the inventors designed Examples 6-13 and Comparative Examples 3-6 by adjusting the polarization conditions. By adjusting the electric field intensity and polarization time, the alignment of the ferroelectric domains in the piezoelectric ceramics and their impact on piezoelectric performance were observed. The specific polarization conditions and performance test results for Examples 6-13 and Comparative Examples 3-6 are shown in Table 2 below.

[0036] Table 2 Polarization conditions and performance test results of Examples 4, 6 to 13 and Comparative Examples 3 to 6

[0037] As shown in Table 2, when the polarization voltage of 0.06Bi-KNNS-NZ piezoelectric ceramics is less than 2V or the polarization time is less than 5 minutes, the polarization effect of the piezoelectric ceramics is not significant, and its various performances do not meet the conditions for road energy capture use. Under the conditions of polarization voltage of 2 to 4V and polarization time of 5 to 25 minutes, with the increase of polarization voltage, its piezoelectric constant d33, electromechanical coupling coefficient Kp and mechanical quality factor Qm all increase significantly, reaching 530pC / N, 0.655 and 35.32 respectively at 4kV / mm, which is a significant improvement over 2kV / mm. However, when the voltage is further increased to 4.5kV / mm, electrode breakdown occurs, indicating that 4kV / mm is the optimal polarization voltage. Further research into the poling time revealed that electrical properties initially increased and then decreased with increasing poling time, reaching their optimum at 15 minutes. This is attributed to the gradual completion of the alignment of the electrical domains (particularly the 90° domains). However, excessively long poling times (e.g., 60 minutes) can easily lead to performance degradation. Therefore, the inventors believe that the ceramic achieves optimal piezoelectric performance when the electric field strength is 4 kV / mm and the poling time is 15 minutes.

[0038] In summary, at a polarization voltage of 4 V and a polarization time of 15 minutes, the 0.06Bi-KNNS-NZ lead-free ceramic Tc 220℃, which is significantly better than the operating temperature range of road piezoelectric energy harvesting system (-15℃ to 85℃), and d 33 It reaches 530 pC / N, meeting the needs of road power supply and showing good thermal stability and application potential.

[0039] The inventors used the method of preparing a 15 mm piezoelectric ceramic sheet in Example 4 as an example to prepare a 65 mm piezoelectric ceramic sheet to prepare a drum-type piezoelectric transducer. The specific method is as follows: S1, potassium carbonate, sodium carbonate, niobium pentoxide, antimony trioxide, bismuth oxide and zirconium dioxide are placed separately in an electric blast drying oven to remove excess moisture; then 0.95K 0.48 Na 0.52 Nb 0.96 Sb 0.04 O3-0.05Na 0.5 Bi 0.5×(1+x) ZrO3, wherein x = -0.03, weigh the raw materials and mix them evenly to obtain mixed material I; S2. Ball mill the mixture I. Before ball milling, add an appropriate amount of anhydrous ethanol to the ball mill jar and clean it by idling until the liquid becomes transparent. Then, control the speed to 230 rpm and ball mill for 22 h, using intermittent alternation to ensure uniform mixing. After the ball milling is completed, pass it through a 200-mesh sieve, rinse it, collect the slurry, and then dry it at 80°C to obtain mixture II. S3. Sintering the mixed material II at 860°C for 7 hours, then taking 150 g of the powder, adding dropwise 25 ml of a 7% polyvinyl alcohol aqueous solution, zirconium balls, and anhydrous ethanol into a ball mill, and performing a secondary ball milling. After ball milling for 20 hours, the mixed material III was obtained. S4. Pass the mixture III through a 300-mesh sieve to remove large particles and ensure material purity. Then, centrifuge and granulate at 110°C for 18 hours. Weigh 120 g of the powder and press it into a 10 cm thick test piece using a 65 mm diameter mold at a pressure of 8 MPa for 30 seconds. Then, consolidate and compact it under a pressure of 225 MPa. S5. Place the test piece in a high-temperature debinding furnace, heat it to 780℃ at a constant speed of 3℃ / min, keep it warm for 2.5 hours and then cool it naturally to room temperature; then heat it to 1150℃ at a rate of 5℃ / min and sinter it for 12 hours, then cool it to room temperature to obtain a lead-free piezoelectric ceramic with a diameter of 65mm; then, wipe the surface of the lead-free piezoelectric ceramic with anhydrous ethanol and polish it with fine sandpaper, then use vertical screen printing technology to evenly apply conductive silver paste, apply twice on each side, after drying, heat it to 680℃ at a rate of 5℃ / min and keep it warm for 30 minutes, then cool it to room temperature, polish the edge and side silver layer of the ceramic to prevent the electrodes on both sides from conducting; finally, apply an external electric field strength of 4 kV / mm and polarize for 15 minutes, then let it stand at room temperature for 24 hours to obtain a lead-free piezoelectric ceramic.

[0040] S6. Bond the lead-free piezoelectric ceramic prepared in step S5 to a 304 stainless steel sheet using structural adhesive, and dry and cure at 75° C. for 5 hours to obtain a drum-type piezoelectric transducer.

[0041] The prepared drum piezoelectric transducer was placed in a three-channel fatigue testing machine to test its fatigue performance. The test method included: subjecting the 0.06Bi-KNNS-NZ lead-free piezoelectric ceramic drum transducer to 2.1 million continuous loads (equivalent to approximately one year of traffic load) at an excitation displacement of 0.5mm and 10Hz, under an 80kΩ external load. The load voltage waveform and load output voltage RMS graph were obtained. The test results are shown in the figure below. Figure 5 shown.

[0042] Depend on Figure 5 It can be seen that after 2.1 million load cycles, the load output voltage remained stable. During the initial stages of the load test, the output voltage fluctuated, with the transducer's output voltage dropping before slowly recovering and stabilizing. This phenomenon fully demonstrates the excellent recovery capabilities of this lead-free ceramic transducer. The output voltage degraded from an initial 5.667V to 5.498V with a degradation rate of only 2.9%, demonstrating the excellent fatigue resistance of this lead-free piezoelectric ceramic transducer.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A lead-free piezoelectric ceramic that can be used in a road vibration energy harvesting device, characterized in that: The chemical composition of the piezoelectric ceramic is: 0.95K 0.48 Na 0.52 Nb 0.96 Sb 0.04 O3-0.05Na 0.5 Bi 0.5×(1+x) ZrO3, wherein the value range of x is: -0.03≤x≤0.

09.

2. A method for preparing a lead-free piezoelectric ceramic that can be used for a road vibration energy harvesting device as claimed in claim 1, characterized in that: The following steps are involved: S1. After drying the required raw materials separately, weighing and mixing according to the chemical composition of the piezoelectric ceramic to obtain a uniform mixture I; S2, ball milling, sieving, rinsing and drying the mixture I to obtain the mixture II; S3, pre-sintering the mixture II, and then performing a second ball milling to obtain the mixture III; S4, sieving the mixed material III and centrifuging to granulate, and then pressing into tablets to obtain test tablets; S5. Debinding the test piece, sintering it, and polarizing it to obtain a lead-free piezoelectric ceramic.

3. The method for preparing the lead-free piezoelectric ceramics that can be used for road vibration energy harvesting devices according to claim 2, characterized in that: In step S1, the raw materials include but are not limited to K2CO3, Na2CO3, Nb2O5, Sb2O3, Bi2O3 and ZrO2.

4. The method for preparing the lead-free piezoelectric ceramics that can be used for road vibration energy harvesting devices according to claim 2, characterized in that: In step S2, the rotation speed of the first ball milling is 200-250 rpm, and the time is not less than 20 hours.

5. The method for preparing the lead-free piezoelectric ceramics that can be used for a road vibration energy harvesting device according to claim 2, wherein: In step S3, the pre-sintering temperature is 850-860° C. and the time is 6-8 hours.

6. The method for preparing the lead-free piezoelectric ceramics that can be used for road vibration energy harvesting devices according to claim 2, characterized in that: In step S4, the centrifugation temperature is 100-120° C., and the centrifugation time is not less than 18 hours.

7. The method for preparing the lead-free piezoelectric ceramics that can be used for road vibration energy harvesting devices according to claim 6, characterized in that: In step S4, the tableting conditions include: an initial pressure of 8-10 MPa, a time of 25-30 s, and a final pressure of 220-230 MPa.

8. The method for preparing the lead-free piezoelectric ceramics that can be used for road vibration energy harvesting devices according to claim 2, characterized in that: In step S5, the debinding conditions include: heating the test piece from the initial temperature to 750°C-800°C at a rate of 2°C-4°C / min, keeping the temperature for 2-3 hours, and then cooling to 20-28°C; The sintering conditions include: heating the test piece from an initial temperature to 1100° C. to 1150° C. at a rate of 3° C. to 6° C. / min, keeping the temperature for 12 to 14 hours, and then cooling to 20 to 28° C.

9. The method for preparing the lead-free piezoelectric ceramics that can be used for road vibration energy harvesting devices according to claim 8, characterized in that: In step S5, the polarization conditions include: an applied electric field strength of 2-4 kV / mm and a time of 5-25 min.

10. An application of the lead-free piezoelectric ceramics for road vibration energy harvesting devices according to claim 1, characterized in that: The lead-free piezoelectric ceramic is subjected to patch and curing treatments to produce a drum-type piezoelectric transducer.

Images