Method for improving piezoelectric coefficient of bismuth layered piezoelectric ceramic material

Abstract

The invention provides a method for improving the piezoelectric coefficient of a bismuth layered piezoelectric ceramic material. The method comprises the following steps: carrying out primary high-temperature heat treatment and primary polarization treatment on the bismuth layered piezoelectric ceramic material; wherein the bismuth layered piezoelectric ceramic material is CaBi2Nb2O9, CaBi2Nb1. 975W0. 025O9 or Ca0. 94Bi2. 06Nb2O, the temperature of the primary high-temperature heat treatment is 1000 to 1050 DEG C, the temperature of the primary polarization treatment is 160 to 200 DEG C, and the time of the primary polarization treatment is 5 to 30 minutes.

Description

Technical Field

[0001] The invention belongs to the field of high-temperature piezoelectric ceramic material technology processing, and in particular relates to a method for improving the piezoelectric coefficient of a bismuth layered piezoelectric ceramic material. Background Art

[0002] High-temperature piezoelectric vibration sensors, with their advantages of self-generation, wide measurement range, high operating temperature, and radiation resistance, are the irreplaceable sensor of choice for vibration monitoring of critical equipment in harsh environments such as high temperatures and high speeds. The operating conditions of key components such as the intake ducts and casings of my country's advanced aero-engines, as well as the fuel assemblies, control rods, and cooling ducts used in third-generation nuclear power technology, all require high-temperature piezoelectric vibration sensors above 650°C for broadband vibration monitoring.

[0003] Piezoelectric ceramic materials are the core sensitive components of piezoelectric vibration sensors, which realize the key function of converting the vibration acceleration signal into an electrical signal. c Above 900℃, it has extremely low dielectric loss and ultra-high resistivity, which can fully meet the use requirements in the above harsh environments and perform real-time broadband vibration monitoring of important components of aircraft engines and nuclear power plants. However, due to its low piezoelectric coefficient (piezoelectric coefficient d 33 Usually lower than 10pC / N), which seriously restricts the widespread use of CaBi2Nb2O9-based piezoelectric ceramic materials in harsh environments. It is also one of the reasons why my country's research on high-temperature piezoelectric vibration sensors for 650℃ has not made a breakthrough.

[0004] Currently, optimizing the composition through A / B-site ion doping is a common method for improving the piezoelectric coefficient of CaBi2Nb2O9-based piezoelectric ceramics. For example, the piezoelectric coefficient of La doping at the A-site is 11.7pC / N, and the piezoelectric coefficient of Zr doping at the B-site is 11.6pC / N. Another method for improving piezoelectric properties is to prepare CaBi2Nb2O9-based piezoelectric ceramics with specific crystal plane orientations through texturing, which can increase the piezoelectric coefficient from 6pC / N to 19pC / N. However, due to the complex and difficult process flow, large-scale application is not possible. At the same time, the unique crystal structure of bismuth layered piezoelectric ceramics results in low lattice tolerance, making it impossible to enhance piezoelectric activity by constructing phase boundaries, as is done with perovskite-structured piezoelectric materials. Furthermore, numerous studies have shown that optimizing the composition through A / B site ion doping results in minimal lattice distortion in bismuth layered piezoelectric ceramics, which cannot significantly enhance their piezoelectric coefficient. Furthermore, ion doping is highly accidental, and the addition of impurity elements is generally detrimental to the piezoelectric performance of bismuth layered piezoelectric ceramics. Therefore, finding a simple and universal method to enhance the piezoelectric coefficient of bismuth layered piezoelectric ceramics is a key challenge that needs to be overcome in this field. Summary of the Invention

[0005] The present invention aims to improve the piezoelectric coefficient d of existing bismuth-layered structure piezoelectric ceramics 33 , and the present invention provides a simple and general method that can significantly improve the piezoelectric coefficient d of bismuth-layered structure piezoelectric ceramic materials 33 .

[0006] The present invention provides a method for improving the piezoelectric coefficient of bismuth-layered piezoelectric ceramic materials, including: performing a high-temperature heat treatment and a polarization treatment on the bismuth-layered piezoelectric ceramic materials once; wherein, the bismuth-layered piezoelectric ceramic materials are CaBi2Nb2O9, CaBi2Nb 1.975 W 0.025 O9 or Ca 0.94 Bi 2.06 Nb2O9, the temperature of the high-temperature heat treatment is 1000-1050°C, and the temperature of the polarization treatment is 160-200°C, and the time is 5-30 min.

[0007] Preferably, the bismuth-layered piezoelectric ceramic material is CaBi2Nb 1.975 W 0.025 O9, and the temperature of the high-temperature heat treatment is 1000-1030°C.

[0008] Preferably, the diameter of the bismuth-layered piezoelectric ceramic material is 10-13 mm, and the thickness is 0.5-1 mm.

[0009] Preferably, the heating rate of the high-temperature heat treatment is 2-10°C / min; the time of the high-temperature heat treatment is 10-60 min.

[0010] Preferably, the electric field strength of the polarization treatment is 8-20 kV / mm.

[0011] The Curie temperature of the bismuth-layered piezoelectric ceramic material system described in the present invention is higher than 900°C, which is the highest value among the reported bismuth-layered piezoelectric materials at present, and is the preferred material for piezoelectric ceramics of high-temperature piezoelectric vibration sensors used at 650°C and above. The Curie temperature of the bismuth-layered structure piezoelectric ceramic material (Na 0.5 Bi 2.5 Nb2O9) reported in the prior art is only 700°C, which can only meet the use of high-temperature piezoelectric vibration sensors at 482°C and cannot meet the use at 650°C and above. As is well known, the higher the Curie temperature of a piezoelectric material, the more stable its crystal structure and the greater the difficulty in improving its performance. Therefore, the difficulty of improving the piezoelectric coefficient of the bismuth-layered piezoelectric ceramic material system described in the present invention far exceeds that of Na 0.5 Bi 2.5Nb2O9, however, the present invention only needs one high-temperature heat treatment and one polarization treatment to increase the piezoelectric coefficient of the bismuth layered piezoelectric ceramic material by 100% to 150%. The method of the present invention is not only simpler, but also, in the case where the piezoelectric performance is more difficult to improve, the method of the present invention can increase the piezoelectric coefficient by more than the existing Na 0.5 Bi 2.5 Several times that of Nb2O9.

[0012] The present invention can reduce the piezoelectric coefficient d of the bismuth layered piezoelectric ceramic by one high temperature heat treatment and one polarization treatment. 33 The improvement is 100% to 150%, which is because the high temperature heat treatment can eliminate the element segregation at the grain boundary of the bismuth layered piezoelectric ceramic. Specifically, the surface and cross-sectional morphology of the bismuth layered piezoelectric ceramic after heat treatment (such as Figure 3 As shown in the figure, the grain boundary segregation is basically completely transformed after the 1000℃ heat treatment. According to the relevant theory of Gibbs interface thermodynamics, the structure and chemical composition of the grain boundary determine the thermodynamic state. In most cases, the increase in temperature will lead to an increase in grain boundary energy, and the diffusion rate of ions is positively correlated with the temperature. In addition, as the temperature increases, the lattice solubility of the piezoelectric ceramic increases, and the W ions segregated to the grain boundary are more likely to move into the grain. The two work together to eliminate grain boundary segregation. The concentration distribution of W ions at the grain boundary after 1000℃ heat treatment was measured by transmission electron microscopy (as shown in the figure). Figure 4 (a)), the statistical results are as follows Figure 4 As shown in (b), it was found that the W ion concentration gradually decreased with the distance from the grain boundary, and the W element concentration inside the grain returned to the doping concentration, which once again proved that the W element segregated to the grain boundary after the 1000℃ heat treatment migrated into the grain through the heat treatment, increased the lattice distortion, and increased the residual polarization strength of the bismuth layered piezoelectric ceramic, thereby greatly improving its piezoelectric performance.

[0013] Beneficial effects:

[0014] The method for improving the piezoelectric coefficient of bismuth layered piezoelectric ceramics provided by the present invention has the following advantages: (1) Compared with the ceramic samples that have not been subjected to high temperature heat treatment, the high temperature heat treatment process of the present invention can significantly improve the piezoelectric coefficient d of the bismuth layered piezoelectric ceramic material. 33 , the piezoelectric coefficient d of the bismuth layered piezoelectric ceramic material 33 The performance has been improved by 100-150%, which has played an important role in promoting the research on high-temperature piezoelectric vibration sensors for use at 650°C. (2) Compared with the prior art method of improving the piezoelectric coefficient of bismuth layered piezoelectric ceramics by optimizing the composition design through A / B site ion doping, the method of the present invention can accurately and significantly improve the piezoelectric coefficient d of bismuth layered piezoelectric ceramic materials.33 ; (3) Compared with the method of improving the piezoelectric coefficient of bismuth layer-structured piezoelectric ceramics through the texturing process in the prior art, the method of the present invention has a simple process, a short processing time, does not require complex equipment, and can be mass-produced. Description of the Drawings

[0015] Figure 1 Piezoelectric coefficient d of CaBi2Nb 1.975 W 0.025 O9 piezoelectric ceramics before and after heat treatment at 1000 °C; 33 Relationship diagram of the piezoelectric coefficient d varying with the polarization electric field strength; Figure 2 Piezoelectric coefficient d of CaBi2Nb 1.975 W 0.025 O9 piezoelectric ceramics before and after heat treatment at 900 °C and 1000 °C; 33 Relationship diagram of the piezoelectric coefficient d varying with the polarization electric field strength; Figure 3 Surface and cross-sectional morphologies of CaBi2Nb 1.975 W 0.025 O9 after heat treatment at different temperatures; where a1 - a4 are the surface morphologies of untreated, heat-treated at 900 °C, 950 °C, and 1000 °C respectively; b1 - b4 are the cross-sectional morphologies of untreated, heat-treated at 900 °C, 950 °C, and 1000 °C respectively; Figure 4 (a) Concentration distribution of W element at the grain boundary of CaBi2Nb 1.975 W 0.025 O9 piezoelectric ceramics after heat treatment at 1000 °C, (b) Statistical results of the W ion concentration at the grain boundary; Figure 5 Piezoelectric coefficient d of CaBi2Nb 1.975 W 0.025 O9 after heat treatment at untreated, 900 °C, 950 °C, and 1000 °C; Figure 6 Piezoelectric coefficient d of CaBi2Nb 1.975 W 0.025 O9 piezoelectric ceramics before and after heat treatment at 1000 °C and 1100 °C; 33 Relationship diagram of the piezoelectric coefficient d varying with the polarization electric field strength; Figure 7 Piezoelectric coefficient d of CaBi2Nb 1.975 W 0.025 O9 piezoelectric ceramics before and after heat treatment at 1000 °C, polarization for 1 min and 10 min; 33 Relationship diagram of the piezoelectric coefficient d varying with the polarization electric field strength. Detailed Embodiments

[0016] To further illustrate the content, features and actual effects of the present invention, the present invention will be described in detail below in conjunction with embodiments. It should be noted that the modified methods designed by the present invention are not limited to these specific embodiments. Without departing from the spirit and connotation of the design of the present invention, equivalent replacements and modifications made by those skilled in the art on the basis of reading the content of the present invention are also within the scope of protection required by the present invention.

[0017] The present invention uses high-temperature heat treatment to eliminate element segregation at the grain boundaries of bismuth-layered piezoelectric ceramics, and combines polarization treatment to greatly improve the piezoelectric coefficient of bismuth-layered piezoelectric ceramics.

[0018] The following exemplarily illustrates the method for improving the piezoelectric coefficient of bismuth-layered piezoelectric ceramic materials provided by the present invention.

[0019] Process large-sized cylindrical bismuth-layered piezoelectric ceramic materials into standard pieces, heat-treat them at 1000 - 1050 °C for 10 - 60 min, and then polarize them for 5 - 30 min under the conditions of a polarization electric field strength of 8 - 20 kV / mm and a polarization temperature of 160 - 200 °C.

[0020] In an alternative embodiment, the bismuth-layered piezoelectric ceramic material is CaBi2Nb2O9, CaBi2Nb 1.975 W 0.025 O9 or Ca 0.94 Bi 2.06 Nb2O9. The Curie temperature of the bismuth-layered piezoelectric ceramic materials of the present invention is higher than 900 °C, which is the preferred piezoelectric ceramic for piezoelectric vibration sensors at 600 °C and above temperatures, and can realize real-time monitoring of the health status of main devices such as aero-engine casings, ducts, and nuclear power plant cooling pipes.

[0021] The diameter of the standard piece is 10 - 13 mm, and the thickness is 0.5 - 1 mm.

[0022] The purpose of the heat treatment of the present invention is to eliminate element segregation at the grain boundaries of the bismuth-layered structure piezoelectric ceramic materials. If the heat treatment temperature is too low, the element segregation at the grain boundaries of the ceramics cannot be eliminated; if the heat treatment temperature is too high, the volatilization rate of Bi elements increases significantly, resulting in the failure of bismuth-layered piezoelectric ceramics. If the heat treatment time is too short, the element segregation at the grain boundaries of the ceramics has no time to be eliminated; if the heat treatment time is too long, the accumulated amount of volatilized Bi elements is too much, which will also cause the failure of bismuth-layered piezoelectric ceramics.

[0023] The heating rate of the heat treatment is 2 - 10 °C / min.

[0024] Polarization treatment is the key process to endow bismuth layer-structured piezoelectric ceramic materials with piezoelectric properties. Piezoelectric ceramics can only obtain piezoelectric coefficients after polarization. However, the sufficient polarization electric field intensity of bismuth layer piezoelectric ceramics is close to its breakdown electric field intensity. Therefore, if the polarization electric field intensity is less than 8 kV / mm, due to insufficient polarization, the piezoelectric coefficient is low, seriously affecting its use. But if the polarization electric field intensity is greater than 20 kV / mm, it will cause the bismuth layer piezoelectric ceramics to fail due to electric breakdown because it is higher than the electric shock electric field of the bismuth layer piezoelectric ceramics. If the polarization time is too short, the piezoelectric coefficient will be small due to insufficient polarization time. If the polarization time is too long, not only will a large amount of energy be wasted, but the bismuth layer piezoelectric ceramics will also be damaged.

[0025] The following further gives examples to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention all fall within the protection scope of the present invention. The specific process parameters and the like in the following examples are only an example within a suitable range, that is, those skilled in the art can make selections within a suitable range through the description in this article, rather than being limited to the specific values in the following examples.

[0026] Example 1

[0027] (1) Process the CaBi2Nb 1.975 W 0.025 O9 bismuth layer-structured piezoelectric ceramic material sample into a standard piece (diameter 11 mm, thickness 0.5 mm), heat it to 1000 °C at a heating rate of 1.2 °C / min, perform heat treatment for 30 min, and then cool it to room temperature with the furnace.

[0028] (2) At 200 °C, polarize the heat-treated samples at polarization electric field intensities of 8 kV / mm, 12 kV / mm, and 16 kV / mm for 10 minutes respectively, and measure their piezoelectric coefficient d 33 to be 3.4 pC / N, 9.0 pC / N, and 13.5 pC / N.

[0029] Comparative Example 1

[0030] The method for improving the piezoelectric coefficient of the bismuth layer piezoelectric ceramic material in this Comparative Example 1 refers to Example 1, and the difference is only that: the bismuth layer-structured piezoelectric ceramic material sample is not subjected to the high-temperature heat treatment in step (1), and directly polarize the sample at 200 °C at polarization electric field intensities of 8 kV / mm, 12 kV / mm, and 16 kV / mm for 10 minutes respectively, and measure its piezoelectric coefficient d 33 which are 0.7 pC / N, 2.6 pC / N, and 5.5 pC / N respectively.

[0031] Figure 1CaBi2Nb before heat treatment and after heat treatment at 1000 °C 1.975 W 0.025 The piezoelectric coefficient d of O9 piezoelectric ceramics 33 Relationship diagram with the change of polarization electric field strength. It can be seen from the figure that CaBi2Nb 1.975 W 0.025 For the bismuth layer-structured piezoelectric ceramic material of O9, after heat treatment at 1000 °C, the piezoelectric coefficient d 33 Increases by 100 - 150%, and the effect is significant.

[0032] Comparative Example 2

[0033] The method for improving the piezoelectric coefficient of the bismuth layer piezoelectric ceramic material in this Comparative Example 2 refers to Example 1, with the only difference being that in step (1), the heat treatment temperature is 900 °C.

[0034] The piezoelectric coefficients d of the bismuth layer piezoelectric ceramic material in this Comparative Example 2 measured under polarization field strengths of 8 kV / mm, 12 kV / mm, and 16 kV / mm 33 Are 0.6 pC / N, 2.4 pC / N, and 5.6 pC / N.

[0035] Figure 2 CaBi2Nb before heat treatment at 900 °C and after heat treatment at 1000 °C 1.975 W 0.025 The piezoelectric coefficient d of O9 piezoelectric ceramics 33 Relationship diagram with the change of polarization electric field strength. It can be seen from the figure that for CaBi2Nb after heat treatment at 900 °C 1.975 W 0.025 The piezoelectric coefficient d of O9 33 Is significantly lower than that of CaBi2Nb after heat treatment at 1000 °C 1.975 W 0.025 The piezoelectric coefficient d of O9 33 .

[0036] Figure 3 CaBi2Nb 1.975 W 0.025 Surface and cross-sectional morphologies of O9 after heat treatment at different temperatures. Among them, a1 - a4 are the surface morphologies of as - received, heat - treated at 900 °C, 950 °C, and 1000 °C respectively; b1 - b4 are the cross - sectional morphologies of as - received, heat - treated at 900 °C, 950 °C, and 1000 °C respectively. From Figure 3 a1 and Figure 3 b1, it can be seen that for as - received CaBi2Nb 1.975 W 0.025 O9 ceramics, there are a large number of second phases formed due to element segregation at the grain boundaries ( Figure 3 a1 and Figure 3The white area in b1), which will seriously reduce the piezoelectric properties of the bismuth-layered piezoelectric ceramic material of the present invention. From Figure 3 a2 and Figure 3 b2, it can be seen that after heat treatment at 900 °C, the second phase formed by grain boundary segregation in the backscattered electron image of CaBi2Nb 1.975 W 0.025 O9 ceramic has no obvious change ( Figure 3 the number of white areas in a2 and 3b2 is compared with Figure 3 a1 and 3b1 has no obvious change). From Figure 3 a3 and Figure 3 b3, it can be seen that after heat treatment at 950 °C, part of the second phase formed by grain boundary segregation of the ceramic is eliminated, and the piezoelectric coefficient d 33 is increased to 8.9 pC / N. From Figure 3 a4 and Figure 3 b4, it can be seen that after heat treatment at 1000 °C, the second phase at the grain boundary in the backscattered electron image basically disappears ( Figure 3 the white areas in a4 and 3b4 basically disappear), and after the elimination of the second phase, the piezoelectric properties of the bismuth-layered piezoelectric ceramic material of the present invention are greatly improved. It can be seen from this that high-temperature heat treatment can eliminate the second phase formed by element segregation at the grain boundaries of the bismuth-layered structure piezoelectric ceramic material, but if the heat treatment temperature is too low, the second phase generated by segregation cannot be eliminated.

[0037] Figure 5 The ferroelectric hysteresis loop diagrams of CaBi2Nb 1.975 W 0.025 O9 before heat treatment, after heat treatment at 900 °C, after heat treatment at 950 °C, and after heat treatment at 1000 °C. It can be seen from the figure that the ferroelectric hysteresis loops of CaBi2Nb 1.975 W 0.025 O9 before heat treatment and after heat treatment at 900 °C have no obvious change, which is consistent with the test results of the backscattered electrons. After heat treatment at 1000 °C, due to the elimination of the second phase, its remanent polarization intensity (P r ) is significantly improved. According to the piezoelectric coefficient calculation formula d 33 = 2Qε r P r it can be seen that d 33 also increases accordingly. Therefore, by adopting high-temperature heat treatment, the second phase formed by element segregation at the grain boundaries of the bismuth-layered piezoelectric ceramic can be eliminated, the remanent polarization intensity of the bismuth-layered piezoelectric ceramic can be improved, and thus its piezoelectric properties can be greatly improved.

[0038] Comparative Example 3

[0039] The method for increasing the piezoelectric coefficient of the bismuth-layered piezoelectric ceramic material in this Comparative Example 3 refers to Example 1, and the only difference is that: in step (1), the heat treatment temperature is 1100 °C.

[0040] The piezoelectric coefficient d of the bismuth-layered piezoelectric ceramic material in Comparative Example 3 measured at polarization field strengths of 8 kV / mm, 12 kV / mm, and 16 kV / mm 33 was 2.5 pC / N, 8.1 pC / N, and 11.8 pC / N.

[0041] Figure 6 was CaBi2Nb after heat treatment at 1000 °C and after heat treatment at 1100 °C 1.975 W 0.025 O9 piezoelectric ceramic piezoelectric coefficient d 33 Graph of the relationship between the piezoelectric coefficient d and the polarization electric field strength. As can be seen from the figure, the piezoelectric coefficient d of CaBi2Nb 1.975 W 0.025 O9 after heat treatment at 1100 °C 33 was significantly lower than that of CaBi2Nb 1.975 W 0.025 O9 after heat treatment at 1000 °C 33 , because the heat treatment temperature was too high, and the Bi element in CaBi2Nb 1.975 W 0.025 O9 volatilized excessively, rendering the bismuth-layered piezoelectric ceramic ineffective.

[0042] Table 1 shows the piezoelectric coefficient d of CaBi2Nb 1.975 W 0.025 O9 piezoelectric ceramic measured at polarization field strengths of 8 kV / mm, 12 kV / mm, and 16 kV / mm after no heat treatment, heat treatment at 900 °C, 950 °C, 1000 °C, and 1100 °C 33 .

[0043] Table 1: Not heat-treated Heat-treated at 900 °C Heat-treated at 950 °C Heat-treated at 1000 °C Heat-treated at 1100 °C 8 kV / mm 0.7 pC / N 0.6 pC / N 2.3 pC / N 3.4 pC / N 2.5 pC / N 12 kV / mm 2.6 pC / N 2.4 pC / N 4.5 pC / N 9.0 pC / N 8.1 pC / N 16 kV / mm 5.5 pC / N 5.6 pC / N 8.9 pC / N 13.5 pC / N 11.8 pC / N

[0044] Comparative Example 4

[0045] The method for increasing the piezoelectric coefficient of the bismuth-layered piezoelectric ceramic material in Comparative Example 4 refers to Example 1, with the only difference being that the polarization treatment time in step (2) was 1 min.

[0046] The piezoelectric coefficient d of the bismuth-layered piezoelectric ceramic material in Comparative Example 4 measured at polarization field strengths of 8 kV / mm, 12 kV / mm, and 16 kV / mm 33 was 2.4 pC / N, 7 pC / N, and 11 pC / N.

[0047] Table 2 shows CaBi2Nb 1.975 W 0.025The piezoelectric coefficient d of O9 piezoelectric ceramics after heat treatment at 1000 °C and poled for 1 min, 10 min respectively under the poling field strengths of 8 kV / mm, 12 kV / mm, 16 kV / mm 33 。

[0048] Table 2: 8 kV / mm 12 kV / mm 16 kV / mm 10 min 3.4 pC / N 9.0 pC / N 13.5 pC / N 1 min 2.4 pC / N 7.0 pC / N 11 pC / N

[0049] Figure 7 The piezoelectric coefficient d of CaBi2Nb 1.975 W 0.025 O9 piezoelectric ceramics after heat treatment at 1000 °C and poled for 1 min, 10 min respectively 33 Relationship diagram of the piezoelectric coefficient d varying with the poling electric field strength. It can be seen from the figure that the piezoelectric coefficient d of CaBi2Nb 1.975 W 0.025 O9 piezoelectric ceramics after poling for 1 min 33 is significantly lower than that of CaBi2Nb 1.975 W 0.025 O9 piezoelectric ceramics after poling for 10 min. This is because the poling time is too short, and the insufficient poling time results in a small piezoelectric coefficient of CaBi2Nb 33 W 1.975 O9 piezoelectric ceramics. 0.025 ​

Claims

1. A method for improving the piezoelectric coefficient of bismuth layer-structured piezoelectric ceramic materials, characterized in that, including: Perform a high-temperature heat treatment and a poling treatment on the bismuth-layered piezoelectric ceramic material; wherein, the bismuth-layered piezoelectric ceramic material is CaBi2Nb2O9, CaBi2Nb 1.975 W 0.025 O9 or Ca 0.94 Bi 2.06 Nb2O. The temperature of the high-temperature heat treatment is 1000 - 1050 °C, and the temperature of the poling treatment is 160 - 200 °C, and the time is 5 - 30 min.

2. The method according to claim 1, wherein The bismuth layer-structured piezoelectric ceramic material is CaBi2Nb 1.975 W 0.025 O9, and the temperature of the first high-temperature heat treatment is 1000 to 1030 °C.

3. The method according to claim 1 or 2, characterized in that, The diameter of the bismuth layer-structured piezoelectric ceramic material is 10 to 13 mm, and the thickness is 0.5 to 1 mm.

4. The method according to any one of claims 1 to 3, characterized in that The heating rate of the first high-temperature heat treatment is 2 to 10 °C / min; the time of the first high-temperature heat treatment is 10 to 60 min.

5. The method according to any one of claims 1-4, characterized in that, The electric field strength of the first polarization treatment is 8 to 20 kV / mm.

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