Multi-ion doped modified CBT piezoelectric ceramic and low-temperature preparation method thereof

Abstract

The application relates to the technical field of piezoelectric ceramic materials, in particular to a multi-ion doped modified CBT piezoelectric ceramic and a low-temperature preparation method thereof. 0.6 Na 0.2 Pr 0.07 Gd 0.01 Bi 2.12 Ta 2‑3x Nb x W x Mn x O9, wherein 0.1<=x<=0.6; wherein Na, Pr and Gd enter the A position of the crystal lattice, and Nb, W and Mn enter the B position of the crystal lattice. The application realizes low-temperature sintering preparation by optimizing the crystal structure and reducing sintering activation energy through multi-ion synergic doping modification, and the obtained piezoelectric ceramic has good piezoelectric performance.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric ceramic materials technology, and in particular to a multi-ion doped modified CBT piezoelectric ceramic and its low-temperature preparation method. Background Technology

[0002] CaBi₂Ta₂O₉ (CBT) is a typical bismuth-layered high-temperature piezoelectric ceramic, possessing both a high Curie temperature and excellent thermal stability, and shows promising application prospects in high-temperature sensing, ultrasonic testing, and structural health monitoring. With the increasing demand for in-situ monitoring of high-temperature components in critical equipment, the direct fabrication of piezoelectric ceramic coatings and direct-write transducers on component surfaces using thermal spraying technology has become an important development direction for high-temperature piezoelectric devices.

[0003] However, CBT piezoelectric ceramics still have significant shortcomings in practical applications: On the one hand, ceramic coatings prepared by thermal spraying generally require subsequent high-temperature heat treatment to improve density, enhance particle bonding, and optimize piezoelectric properties, while the sintering temperature of traditional CBT piezoelectric ceramics is as high as 1100~1200℃. Excessively high heat treatment temperatures can easily lead to matrix deterioration, thermal stress accumulation, and interface mismatch failure, while also damaging the surface performance of components, severely restricting their integrated application in temperature-sensitive substrates and high-end equipment surfaces.

[0004] On the other hand, the high-temperature sintering process can also induce pores and microcracks inside the ceramic, while causing element volatilization, further hindering the densification process of the ceramic, deteriorating the electrical and piezoelectric properties, and ultimately reducing the detection sensitivity and long-term service reliability of piezoelectric devices. Summary of the Invention

[0005] The purpose of this invention is to provide a CBT piezoelectric ceramic modified by multiple ion doping and its low-temperature preparation method. By modifying the ceramic by multiple ion synergistic doping, the crystal structure is optimized, the ion diffusion and migration rate are promoted, and the sintering activation energy is reduced, thereby realizing the preparation by low-temperature sintering. The resulting piezoelectric ceramic has good piezoelectric properties.

[0006] To achieve the above objectives, this invention provides a multi-ion-doped modified CBT piezoelectric ceramic, which is prepared by low-temperature sintering. The general chemical formula of the piezoelectric ceramic is: Ca 0.6 Na 0.2 Pr 0.07 Gd 0.01 Bi 2.12 Ta 2-3x Nb x W x Mn x O9, where 0.1≤x≤0.6; where Na, Pr, and Gd enter the A sites of the crystal lattice, and Nb, W, and Mn enter the B sites of the crystal lattice.

[0007] Preferably, the temperature for low-temperature sintering is 850~1000℃.

[0008] This invention also provides a low-temperature preparation method for the above-mentioned multi-ion doped modified CBT piezoelectric ceramic, comprising the following steps: S1. Weigh the raw materials according to the general chemical formula of piezoelectric ceramics; crush the raw materials by ball milling and mix them evenly, pre-fire them, cool them and then ball mill them again to obtain CBT piezoelectric ceramic powder with multi-ion doping modification. S2. Add polyvinyl alcohol solution to the multi-ion doped modified CBT piezoelectric ceramic powder obtained in S1 for granulation, and press the resulting granules into sheets to obtain multi-ion doped modified CBT piezoelectric ceramic sheets. S3. After removing the binder from the multi-ion doped modified CBT piezoelectric ceramic sheet obtained in S2, sinter it at a low temperature to obtain the sintered CBT piezoelectric ceramic sheet. S4. Coat the surface of the sintered CBT piezoelectric ceramic sheet obtained in S3 with silver paste and heat it to burn silver. After cooling, place it in silicone oil for electric field polarization to obtain CBT piezoelectric ceramic modified with multiple ion doping.

[0009] Preferably, in S1, the dispersion medium for ball milling is anhydrous ethanol, the mass ratio of the dispersion medium to the total amount of raw materials is 1:1~1.5, the ball milling speed is 100~450 rpm, and the ball milling time is 10~24 h.

[0010] Preferably, in S1, the pre-firing temperature is 850~950℃ and the pre-firing time is 2~4h.

[0011] Preferably, in S2, the concentration of the polyvinyl alcohol solution is 5-10 wt%, and the amount of polyvinyl alcohol solution used is 10-15 wt% of the multi-ion doped modified CBT piezoelectric ceramic powder.

[0012] Preferably, in S2, the pressure for pressing the sheet is 10~20MPa, the diameter of the sheet is 10~15mm, and the thickness of the sheet is 0.8~1.2mm.

[0013] Preferably, in S3, the temperature for debinding is 450~550℃, the time for debinding is 4~10h, the temperature for low-temperature sintering is 850~1000℃, and the time for low-temperature sintering is 2~4h.

[0014] Preferably, in S4, the coating mass of the silver paste is 5-15 wt% of the mass of the sintered CBT piezoelectric ceramic sheet; the heat treatment temperature for silver firing is 650-750℃, and the time is 10-20 min.

[0015] Preferably, in S4, the temperature of the silicone oil is 180~220℃; the electric field strength for electric field polarization is 5~10kV / mm; and the electric field polarization time is 15~30min.

[0016] Mechanism of the invention: The performance improvement of CBT piezoelectric ceramics modified by multi-ion doping mainly stems from the local crystal structure reconstruction caused by the synergistic regulation of A-sites and B-sites. In this invention, Na, Pr, and Gd are incorporated into the A-sites of the crystal lattice, while Nb, W, and Mn are incorporated into the B-sites. The coexistence of different ionic radii, valence states, and bonding characteristics increases the system's configuration entropy and introduces significant local lattice distortion in the perovskite-like layer of CBT. Substituted ions can enter the CBT main lattice, leading to changes in octahedral tilt, rotation, and BO bond vibrations, thus forming local polar disorder. This local polar disorder enhances in-plane polarization rotation capability and reduces local domain flipping voltage, ultimately strengthening the macroscopic piezoelectric response. On the other hand, multi-ion doping lowers the energy barrier for grain boundary diffusion and densification processes, while small-radius B-site ions promote mass migration and grain growth, enabling the ceramic to achieve better sintering at lower temperatures.

[0017] Therefore, the present invention employs the above-mentioned multi-ion doped modified CBT piezoelectric ceramic and its low-temperature preparation method, which has the following beneficial effects: (1) The CBT piezoelectric ceramic modified by multi-ion doping of the present invention is reduced from the traditional 1100~1200℃ to 850~1000℃, avoiding element volatilization, and can be directly integrated on the temperature-sensitive substrate and the surface of high-end equipment. (2) The CBT piezoelectric ceramic modified by multi-ion doping of the present invention has a pure bismuth layered structure phase, no impurity phase, controllable lattice defects, excellent high temperature stability, and excellent piezoelectric and dielectric properties. (3) The low-temperature preparation method of the present invention is simple, stable, easy to operate, and convenient for industrial production.

[0018] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0019] Figure 1 These are the XRD patterns of the CBT piezoelectric ceramics modified by multi-ion doping in comparative examples and Examples 1-4 of this invention; Figure 2 These are piezoelectric performance diagrams of the CBT piezoelectric ceramics modified by multi-ion doping in comparative examples and Examples 1-4 of this invention; Figure 3 This is a schematic diagram showing the change of dielectric constant of the CBT piezoelectric ceramics modified by multi-ion doping in the comparative examples and Examples 1-4 of this invention as a function of temperature. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments. Unless otherwise defined, the technical or scientific terms used in this invention should be understood in their ordinary sense by those skilled in the art. The features mentioned above or in the specific examples mentioned in this invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the invention and are not intended to limit the scope of the invention.

[0021] This invention provides a multi-ion-doped modified CBT piezoelectric ceramic, which is prepared by low-temperature sintering. The general chemical formula of the piezoelectric ceramic is: Ca 0.6 Na 0.2 Pr 0.07 Gd 0.01 Bi 2.12 Ta 2-3x Nb x W x Mn x O9, where 0.1≤x≤0.6; where Na, Pr, and Gd enter the A sites of the crystal lattice, and Nb, W, and Mn enter the B sites of the crystal lattice.

[0022] The multi-ion doped modified CBT piezoelectric ceramic of the present invention achieves the unity of low-temperature sintering and improved piezoelectric performance by multi-ion synergistic doping, while maintaining the high Curie temperature and high-temperature stability of the bismuth layered structure.

[0023] In this invention, Na, Pr, and Gd introduce size and valence disorder at the A-site, regulating the local strain and defect structure of the perovskite-like layer; Nb 5+ As with Ta 5+ B-site substituents with the same valence and similar radius are beneficial for stabilizing the solid solution structure and regulating polarizability; W 6+ and Mn 2+ The high-valence and low-valence B-site ions, respectively, form complementary valence states, introducing significant radius mismatch and octahedral distortion while maintaining average charge balance. The co-occupancy of multiple ions at the A and B sites increases the system's configuration entropy and induces octahedral distortion, thereby enhancing local polar disorder and in-plane polarization rotation capabilities. This structural effect reduces grain boundary diffusion and densification barriers, lowering the sintering temperature; it also lowers the domain flipping barrier, improving remanent polarization and local piezoelectric response, thus enhancing electrical performance. Therefore, the multi-ion doped CBT piezoelectric ceramic of this invention possesses the potential for low-temperature fabrication, high-temperature stability, and application in high-temperature piezoelectric devices.

[0024] Preferably, the low-temperature sintering temperature is 850~1000℃. The low-temperature sintering temperature of the present invention is much lower than that of traditional CBT piezoelectric ceramics, which effectively avoids the accumulation of thermal stress caused by high temperature, and at the same time suppresses the volatilization of volatile elements such as bismuth and the generation of internal pores in the ceramic.

[0025] This invention also provides a low-temperature preparation method for the above-mentioned multi-ion doped modified CBT piezoelectric ceramic, comprising the following steps: S1. Weigh the raw materials according to the general chemical formula of piezoelectric ceramics; crush the raw materials by ball milling and mix them evenly, pre-fire them, cool them and then ball mill them again to obtain CBT piezoelectric ceramic powder with multi-ion doping modification. S2. Add polyvinyl alcohol solution to the multi-ion doped modified CBT piezoelectric ceramic powder obtained in S1 for granulation, and press the resulting granules into sheets to obtain multi-ion doped modified CBT piezoelectric ceramic sheets. S3. After removing the binder from the multi-ion doped modified CBT piezoelectric ceramic sheet obtained in S2, sinter it at a low temperature to obtain the sintered CBT piezoelectric ceramic sheet. S4. Coat the surface of the sintered CBT piezoelectric ceramic sheet obtained in S3 with silver paste and heat it to burn silver. After cooling, place it in silicone oil for electric field polarization to obtain CBT piezoelectric ceramic modified with multiple ion doping.

[0026] In some specific embodiments of the present invention, the raw materials in S1 are calcium carbonate, sodium carbonate, praseodymium oxide, gadolinium oxide, bismuth oxide, tantalum oxide, niobium pentoxide, tungsten oxide, and manganese dioxide.

[0027] Preferably, in S1, the dispersion medium for ball milling is anhydrous ethanol, the mass ratio of the dispersion medium to the total amount of raw materials is 1:1~1.5, the ball milling speed is 100~450 rpm, and the ball milling time is 10~24 h.

[0028] Preferably, in S1, the pre-firing temperature is 850~950℃, and the pre-firing time is 2~4h. This invention promotes the initial solid-phase reaction between raw material powders through pre-firing, causing the carbonate and other raw materials to decompose earlier and the oxide components to form a CBT-based bismuth layered main crystalline phase. Pre-firing reduces gas release and unreacted residual phases during the final sintering process, reducing porosity, cracking, and component segregation. It also allows for more complete grain boundary diffusion and densification during the final sintering process, reducing internal porosity and creating a more uniform electric field distribution, which is beneficial for subsequent polarization and domain flipping, thereby improving the electrical properties of the ceramic.

[0029] Preferably, in S2, the concentration of the polyvinyl alcohol solution is 5-10 wt%, and the amount of polyvinyl alcohol solution used is 10-15 wt% of the multi-ion doped modified CBT piezoelectric ceramic powder. By controlling the concentration and amount of polyvinyl alcohol solution within the above range, this invention can improve the powder flowability and green body mechanical strength, and help obtain a green body with a more uniform density.

[0030] Preferably, in step S2, the pressing pressure is 10-20 MPa, the diameter of the pressed sheet is 10-15 mm, and the thickness of the pressed sheet is 0.8-1.2 mm. By controlling the pressing parameters within the above range, this invention can obtain ceramic green bodies with regular shapes, moderate strength, and relatively uniform density. This promotes powder particle rearrangement and compact packing, improves green body strength, reduces edge chipping and cracking during demolding and handling, and avoids uneven sintering shrinkage and cracking risks caused by excessively large sample sizes. It also improves the uniformity of the internal electric field distribution, which is beneficial for full polarization, thereby enhancing the electrical properties of the final ceramic.

[0031] Preferably, in S3, the temperature for debinding is 450~550℃, the time for debinding is 4~10 h, the temperature for low-temperature sintering is 850~1000℃, and the time for low-temperature sintering is 2~4 h.

[0032] This invention removes organic binders such as polyvinyl alcohol before sintering by controlling the temperature and time of debinding within the aforementioned range, thus eliminating organic residues and concentrated venting during subsequent sintering. This facilitates the gradual decomposition and removal of organic matter from the interior of the green body, reducing the risk of porosity, microcracks, and delamination, thereby providing a green body with a uniform structure and fewer defects for subsequent sintering.

[0033] By controlling the low-temperature sintering time within the above-mentioned range, this invention promotes intergranular grain boundary diffusion, pore shrinkage, and moderate grain growth, thereby improving density, reducing residual porosity, improving the uniformity of internal electric field distribution, reducing the loss of volatile components, and suppressing abnormal grain growth and impurity phases.

[0034] Preferably, in S4, the coating mass of the silver paste is 5-15 wt% of the mass of the sintered CBT piezoelectric ceramic sheet; the heat treatment temperature for silver firing is 650-750℃, and the time is 10-20 min.

[0035] By controlling the coating quality of the silver paste within the aforementioned range, this invention ensures that the electrode completely covers the sample surface, reduces contact resistance, and ensures that the applied electric field is uniformly distributed in the ceramic thickness direction, thereby improving the accuracy of dielectric, ferroelectric, impedance, and piezoelectric performance testing.

[0036] This invention improves electrode conductivity and adhesion by controlling the temperature and time of silver burning within the above-mentioned range, removing organic carriers and solvents from the silver paste, and promoting the formation of sintering necks and continuous conductivity between silver particles.

[0037] Preferably, in S4, the temperature of the silicone oil is 180~220℃; the electric field strength for electric field polarization is 5~10kV / mm; and the electric field polarization time is 15~30min. This invention, by controlling the electric field polarization parameters within the above range, utilizes thermal activation to enhance the mobility of ferroelectric domain walls, reduces the domain flipping barrier, and makes it easier for the ceramic to form stable macroscopic residual polarization under an applied electric field. This provides sufficient driving force for ferroelectric domain flipping, causing the domains to align along the thickness direction, stabilizing the polarization state, and thus improving piezoelectric properties.

[0038] Example 1 The general chemical formula of the piezoelectric ceramic in this embodiment is: Ca 0.6 Na 0.2 Pr 0.07 Gd 0.01 Bi 2.12 Ta 1.7 Nb 0.1 W 0.1 Mn 0.1 O9 (when x=0.1). Its low-temperature preparation method includes the following steps: S1. Weigh the raw materials calcium carbonate, sodium carbonate, praseodymium oxide, gadolinium oxide, bismuth oxide, tantalum oxide, niobium pentoxide, tungsten oxide, and manganese dioxide according to the general chemical formula of piezoelectric ceramics. Perform a first ball milling on each raw material, mix thoroughly, and hold at 870℃ for 4 hours. After pre-firing at this temperature, cool to room temperature and perform a second ball milling to obtain multi-ion-doped modified CBT piezoelectric ceramic powder. Anhydrous ethanol was used as the dispersion medium for both the first and second ball milling processes, with a mass ratio of raw materials to anhydrous ethanol of 1:1.5. Both ball millings were performed on a planetary ball mill at 450 rpm for 10 hours. After each ball milling, the powder was dried under a baking lamp for 3 hours.

[0039] S2. Add a polyvinyl alcohol solution with a CBT piezoelectric ceramic powder content of 11wt% and a concentration of 8wt% to the multi-ion doped modified CBT piezoelectric ceramic powder obtained in S1 for granulation. Press the resulting granules into discs with a diameter of about 14mm and a thickness of about 0.9mm under a pressure of 20MPa to obtain multi-ion doped modified CBT piezoelectric ceramic discs.

[0040] S3. The CBT piezoelectric ceramic sheet modified by multi-ion doping obtained in S2 is heat-treated at 550℃ for 4 hours to remove the binder, and then sintered at 850℃ for 3 hours to obtain the sintered CBT piezoelectric ceramic sheet.

[0041] S4. Coat the surface of the sintered CBT piezoelectric ceramic sheet obtained in S3 with silver paste accounting for 12wt% of its mass, hold at 700℃ for 10min, cool to room temperature after holding, and then polarize in silicone oil at 200℃ under an electric field strength of 5kV / mm for 30min to obtain multi-ion doped modified CBT piezoelectric ceramic.

[0042] Example 2 The general chemical formula of the piezoelectric ceramic in this embodiment is: Ca 0.6 Na 0.2 Pr 0.07 Gd 0.01 Bi 2.12 Ta 1.4 Nb 0.2 W 0.2 Mn 0.2 O9 (when x=0.2). Its low-temperature preparation method includes the following steps: S1. Weigh the raw materials calcium carbonate, sodium carbonate, praseodymium oxide, gadolinium oxide, bismuth oxide, tantalum oxide, niobium pentoxide, tungsten oxide, and manganese dioxide according to the general chemical formula of piezoelectric ceramics. Perform a first ball milling on each raw material, mix thoroughly, and hold at 890℃ for 2 hours. After holding at 890℃, cool to room temperature and perform a second ball milling to obtain multi-ion-doped modified CBT piezoelectric ceramic powder. Anhydrous ethanol was used as the dispersion medium for both the first and second ball milling processes, with a mass ratio of raw materials to anhydrous ethanol of 1:1.5. Both ball millings were performed on a planetary ball mill at 300 rpm for 18 hours. After the first ball milling, the powder was dried under a heat lamp for 2 hours, and after the second ball milling, it was dried under a heat lamp for 3 hours.

[0043] S2. Add a 12wt% CBT piezoelectric ceramic powder solution with a concentration of 10wt% to the multi-ion doped modified CBT piezoelectric ceramic powder obtained in S1 for granulation. Press the resulting granules into discs with a diameter of about 13mm and a thickness of about 1mm under a pressure of 15MPa to obtain multi-ion doped modified CBT piezoelectric ceramic discs.

[0044] S3. The CBT piezoelectric ceramic sheet modified by multi-ion doping obtained in S2 is heat-treated at 450℃ for 10h to remove the binder, and then sintered at 900℃ for 2h to obtain the sintered CBT piezoelectric ceramic sheet.

[0045] S4. Coat the surface of the sintered CBT piezoelectric ceramic sheet obtained in S3 with silver paste accounting for 5wt% of its mass, hold at 750℃ for 10min, cool to room temperature after holding, and then polarize in silicone oil at 200℃ under an electric field strength of 10kV / mm for 16min to obtain multi-ion doped modified CBT piezoelectric ceramic.

[0046] Example 3 The general chemical formula of the piezoelectric ceramic in this embodiment is: Ca 0.6 Na 0.2 Pr 0.07 Gd 0.01 Bi 2.12 Ta 1.1 Nb 0.3 W 0.3 Mn 0.3 O9 (when x=0.3). Its low-temperature preparation method includes the following steps: S1. Weigh the raw materials calcium carbonate, sodium carbonate, praseodymium oxide, gadolinium oxide, bismuth oxide, tantalum oxide, niobium pentoxide, tungsten oxide, and manganese dioxide according to the general chemical formula of piezoelectric ceramics. Perform a first ball milling on each raw material, mix thoroughly, and hold at 850℃ for 3 hours. After holding at 850℃, cool to room temperature and perform a second ball milling to obtain multi-ion-doped modified CBT piezoelectric ceramic powder. Anhydrous ethanol was used as the dispersion medium for both the first and second ball milling processes, with a mass ratio of raw materials to anhydrous ethanol of 1:1.5. Both ball millings were performed on a planetary ball mill at 200 rpm for 20 hours. After both ball millings, the powder was dried under a baking lamp for 3 hours.

[0047] S2. Add a 13wt% polyvinyl alcohol solution with a CBT piezoelectric ceramic powder content of 13wt% and a concentration of 10wt% to the multi-ion doped modified CBT piezoelectric ceramic powder obtained in S1 for granulation. Press the resulting granules into discs with a diameter of about 15mm and a thickness of about 0.8mm under a pressure of 20MPa to obtain multi-ion doped modified CBT piezoelectric ceramic discs.

[0048] S3. The CBT piezoelectric ceramic sheet modified by multi-ion doping obtained in S2 is heat-treated at 500℃ for 8 hours to remove the binder, and then sintered at 900℃ for 4 hours to obtain the sintered CBT piezoelectric ceramic sheet.

[0049] S4. Coat the surface of the sintered CBT piezoelectric ceramic sheet obtained in S3 with silver paste accounting for 15wt% of its mass, hold at 650℃ for 15min, cool to room temperature after holding, and then polarize in silicone oil at 200℃ under an electric field strength of 10kV / mm for 25min to obtain multi-ion doped modified CBT piezoelectric ceramic.

[0050] Example 4 The general chemical formula of the piezoelectric ceramic in this embodiment is: Ca 0.6 Na 0.2 Pr 0.07 Gd 0.01 Bi 2.12 Ta 0.8 Nb0.4 W 0.4 Mn 0.4 O9 (when x=0.4). Its low-temperature preparation method includes the following steps: S1. Weigh the raw materials calcium carbonate, sodium carbonate, praseodymium oxide, gadolinium oxide, bismuth oxide, tantalum oxide, niobium pentoxide, tungsten oxide, and manganese dioxide according to the general chemical formula of piezoelectric ceramics. Perform a first ball milling on each raw material, mix thoroughly, and hold at 850℃ for 4 hours. After holding at 850℃, cool to room temperature and perform a second ball milling to obtain multi-ion-doped modified CBT piezoelectric ceramic powder. Anhydrous ethanol was used as the dispersion medium for both the first and second ball milling processes, with a mass ratio of raw materials to anhydrous ethanol of 1:1.5. Both ball millings were performed on a planetary ball mill at 400 rpm for 11 hours. After the first ball milling, the powder was dried under a heat lamp for 2 hours, and after the second ball milling, it was dried under a heat lamp for 3 hours.

[0051] S2. Add a polyvinyl alcohol solution with a CBT piezoelectric ceramic powder content of 14wt% and a concentration of 6wt% to the multi-ion doped modified CBT piezoelectric ceramic powder obtained in S1 for granulation. Press the resulting granules into discs with a diameter of about 10mm and a thickness of about 1.2mm under a pressure of 18MPa to obtain multi-ion doped modified CBT piezoelectric ceramic discs.

[0052] S3. The CBT piezoelectric ceramic sheet modified by multi-ion doping obtained in S2 is heat-treated at 500℃ for 7 hours to remove the binder, and then sintered at 900℃ for 4 hours to obtain the sintered CBT piezoelectric ceramic sheet.

[0053] S4. Coat the surface of the sintered CBT piezoelectric ceramic sheet obtained in S3 with silver paste accounting for 10wt% of its mass, hold at 750℃ for 12min, cool to room temperature after holding, and then polarize in silicone oil at 220℃ under an electric field strength of 10kV / mm for 30min to obtain multi-ion doped modified CBT piezoelectric ceramic.

[0054] Example 5 The general chemical formula of the piezoelectric ceramic in this embodiment is: Ca 0.6 Na 0.2 Pr 0.07 Gd 0.01 Bi 2.12 Ta 0.5 Nb 0.5 W 0.5 Mn 0.5 O9 (when x=0.5). Its low-temperature preparation method includes the following steps: S1. Weigh the raw materials calcium carbonate, sodium carbonate, praseodymium oxide, gadolinium oxide, bismuth oxide, tantalum oxide, niobium pentoxide, tungsten oxide, and manganese dioxide according to the general chemical formula of piezoelectric ceramics. Perform a first ball milling on each raw material, mix thoroughly, and hold at 950℃ for 3 hours. After holding at 950℃, cool to room temperature and perform a second ball milling to obtain multi-ion-doped modified CBT piezoelectric ceramic powder. Anhydrous ethanol was used as the dispersion medium for both the first and second ball milling processes, with a mass ratio of raw materials to anhydrous ethanol of 1:1.5. Both ball millings were performed on a planetary ball mill at 100 rpm for 24 hours. After the first ball milling, the powder was dried under a baking lamp for 2 hours, and after the second ball milling, it was dried under a baking lamp for 3 hours.

[0055] S2. Add a 15wt% CBT piezoelectric ceramic powder solution with a concentration of 10wt% to the multi-ion doped modified CBT piezoelectric ceramic powder obtained in S1 for granulation. Press the resulting granules into discs with a diameter of about 10mm and a thickness of about 1.2mm under a pressure of 10MPa to obtain multi-ion doped modified CBT piezoelectric ceramic discs.

[0056] S3. The CBT piezoelectric ceramic sheet modified by multi-ion doping obtained in S2 is heat-treated at 550℃ for 4 hours to remove the binder, and then sintered at 950℃ for 4 hours to obtain the sintered CBT piezoelectric ceramic sheet.

[0057] S4. Coat the surface of the sintered CBT piezoelectric ceramic sheet obtained in S3 with silver paste accounting for 10wt% of its mass, hold at 650℃ for 20min, cool to room temperature after holding, and then polarize in silicone oil at 200℃ under an electric field strength of 8kV / mm for 15min to obtain multi-ion doped modified CBT piezoelectric ceramic.

[0058] Example 6 The general chemical formula of the piezoelectric ceramic in this embodiment is: Ca 0.6 Na 0.2 Pr 0.07 Gd 0.01 Bi 2.12 Ta 0.2 Nb 0.6 W 0.6 Mn 0.6 O9 (when x=0.6). Its low-temperature preparation method includes the following steps: S1. Weigh the raw materials calcium carbonate, sodium carbonate, praseodymium oxide, gadolinium oxide, bismuth oxide, tantalum oxide, niobium pentoxide, tungsten oxide, and manganese dioxide according to the general chemical formula of piezoelectric ceramics. Perform a first ball milling on each raw material, mix thoroughly, and hold at 900℃ for 3 hours. After holding at 900℃, cool to room temperature and perform a second ball milling to obtain multi-ion-doped modified CBT piezoelectric ceramic powder. Anhydrous ethanol was used as the dispersion medium for both the first and second ball milling processes, with a mass ratio of raw materials to anhydrous ethanol of 1:1.5. Both ball millings were performed on a planetary ball mill at 100 rpm for 24 hours. After the first ball milling, the powder was dried under a baking lamp for 2 hours, and after the second ball milling, it was dried under a baking lamp for 3 hours.

[0059] S2. Add a polyvinyl alcohol solution with a CBT piezoelectric ceramic powder content of 13wt% and a concentration of 10wt% to the multi-ion doped modified CBT piezoelectric ceramic powder obtained in S1 for granulation. Press the resulting granules into discs with a diameter of about 10mm and a thickness of about 1.1mm under a pressure of 10MPa to obtain multi-ion doped modified CBT piezoelectric ceramic discs.

[0060] S3. The CBT piezoelectric ceramic sheet modified by multi-ion doping obtained in S2 is heat-treated at 550℃ for 4 hours to remove the binder, and then sintered at 950℃ for 4 hours to obtain the sintered CBT piezoelectric ceramic sheet.

[0061] S4. Coat the surface of the sintered CBT piezoelectric ceramic sheet obtained in S3 with silver paste accounting for 10wt% of its mass, hold at 650℃ for 20min, cool to room temperature after holding, and then polarize in silicone oil at 200℃ under an electric field strength of 7kV / mm for 15min to obtain multi-ion doped modified CBT piezoelectric ceramic.

[0062] Comparative Example The chemical formula of this comparative piezoelectric ceramic is: Ca 0.6 Na 0.2 Pr 0.07 Gd 0.01 Bi 2.12 Ta₂O₉ (at x=0.0). Its low-temperature preparation method includes the following steps: S1. Weigh the raw materials calcium carbonate, sodium carbonate, praseodymium oxide, gadolinium oxide, bismuth oxide, and tantalum oxide according to the general chemical formula of piezoelectric ceramics. Perform a first ball milling to crush the raw materials and mix them evenly. Then, hold the mixture at 850℃ for 3 hours. After pre-firing at this temperature, cool to room temperature and perform a second ball milling to obtain multi-ion-doped modified CBT piezoelectric ceramic powder. The dispersion medium for both the first and second ball milling is anhydrous ethanol, with a mass ratio of the total amount of each raw material to anhydrous ethanol of 1:1.5. Both the first and second ball millings are performed on a planetary ball mill at 100 rpm for 24 hours. After the first ball milling, dry the powder under a baking lamp for 2 hours, and after the second ball milling, dry it under a baking lamp for 3 hours.

[0063] S2. Add a 10wt% polyvinyl alcohol solution to the multi-ion doped modified CBT piezoelectric ceramic powder obtained in S1 for granulation. Press the resulting granules into discs with a diameter of about 10mm and a thickness of about 1.2mm under a pressure of 10MPa to obtain multi-ion doped modified CBT piezoelectric ceramic discs.

[0064] S3. The CBT piezoelectric ceramic sheet modified by multi-ion doping obtained in S2 is heat-treated at 550℃ for 4 hours to remove the binder, and then sintered at 850℃ for 4 hours to obtain the sintered CBT piezoelectric ceramic sheet.

[0065] S4. Coat the surface of the sintered CBT piezoelectric ceramic sheet obtained in S3 with silver paste accounting for 10wt% of its mass, hold at 650℃ for 20min, cool to room temperature after holding, and then polarize in silicone oil at 180℃ under an electric field strength of 5kV / mm for 15min to obtain multi-ion doped modified CBT piezoelectric ceramic.

[0066] Performance testing: The multi-ion-doped modified CBT piezoelectric ceramics prepared in Comparative Examples and Examples 1-4 were characterized by X-ray diffraction (XRD), and the results are as follows: Figure 1 As shown, the CBT piezoelectric ceramics modified by multi-ion doping in the comparative examples and Examples 1-4 are all pure bismuth layered structure phases with no impurity phase diffraction peaks, good crystallinity, and stable lattice structure.

[0067] The multi-ion-doped modified CBT piezoelectric ceramics prepared in comparative examples and Examples 1-4 were subjected to a ZJ-3 quasi-static test at the Institute of Acoustics, Chinese Academy of Sciences. d 33 The piezoelectric constant was tested using the instrument. The results are as follows: Figure 2 As shown, the piezoelectric coefficient of the comparative example is... d 33 The piezoelectric coefficient of Example 1 is 7.5 pC / N. d 33The piezoelectric coefficient of Example 2 is 10 pC / N. d 33 The piezoelectric coefficient of Example 3 is 14 pC / N. d 33 The piezoelectric coefficient of Example 4 is 10.2 pC / N. d 33 The ratio is 7 pC / N. This demonstrates that the multi-ion doped CBT piezoelectric ceramic of this invention exhibits improved piezoelectric properties. Na, Pr, and Gd introduce size and valence disorder at the A-site, regulating the local strain and defect structure of the perovskite-like layer; Nb... 5+ As with Ta 5+ B-site substituents with the same valence and similar radius are beneficial for stabilizing the solid solution structure and regulating polarizability; W 6+ and Mn 2+ These ions, acting as high-valence and low-valence B-site ions respectively, form complementary valence states. High doping levels and secondary grain growth lead to a decrease in average grain size, restricting domain wall flipping and resulting in... d 33 Reducing the amount of doping introduces significant radius mismatch and octahedral distortion while maintaining the average charge balance, thereby lowering the domain flipping barrier, improving residual polarization and local piezoelectric response, and enhancing electrical performance.

[0068] The dielectric constant of the multi-ion-doped modified CBT piezoelectric ceramics prepared in Comparative Examples and Examples 1-4 was measured as a function of temperature using an Agilent 4980A precision impedance meter connected to a temperature-controlled furnace. The results are as follows: Figure 3 As shown, the Curie temperature for the comparative example is 913℃, the Curie temperature for Example 1 is 885℃, the Curie temperature for Example 2 is 849℃, the Curie temperature for Example 3 is 795℃, and the Curie temperature for Example 4 is 752℃. This demonstrates that the prepared multi-ion-doped modified CBT piezoelectric ceramics, with multiple ions occupying the A-site and B-site, increase the system's configuration entropy and induce octahedral distortion, thereby enhancing local polar disorder and in-plane polarization rotation capabilities. This structural effect, on the one hand, reduces the grain boundary diffusion and densification energy barrier, thus lowering the sintering temperature.

[0069] Therefore, this invention employs the above-mentioned multi-ion doped modified CBT piezoelectric ceramic and its low-temperature preparation method. Under low-temperature sintering conditions of 850~1000℃, a bismuth layered piezoelectric ceramic with pure phase, excellent piezoelectric properties, and high Curie temperature is successfully obtained. This effectively solves the problems of excessively high sintering temperature, easy damage to the matrix, and poor density and electrical properties of traditional CBT piezoelectric ceramics, and has important engineering application value.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A CBT piezoelectric ceramic modified with multiple ion doping, characterized in that: Piezoelectric ceramics are prepared by low-temperature sintering. The general chemical formula of piezoelectric ceramics is: Ca 0.6 Na 0.2 Pr 0.07 Gd 0.01 Bi 2.12 Ta 2-3x Nb x W x Mn x O9, where 0.1≤x≤0.6; where Na, Pr, and Gd enter the A sites of the crystal lattice, and Nb, W, and Mn enter the B sites of the crystal lattice.

2. The CBT piezoelectric ceramic modified with multi-ion doping according to claim 1, characterized in that: The temperature for low-temperature sintering is 850~1000℃.

3. A low-temperature preparation method for a multi-ion-doped modified CBT piezoelectric ceramic as described in any one of claims 1-2, characterized in that: Includes the following steps: S1. Weigh the raw materials according to the general chemical formula of piezoelectric ceramics; crush the raw materials by ball milling and mix them evenly, pre-fire them, cool them and then ball mill them again to obtain CBT piezoelectric ceramic powder with multi-ion doping modification. S2. Add polyvinyl alcohol solution to the multi-ion doped modified CBT piezoelectric ceramic powder obtained in S1 for granulation, and press the resulting granules into sheets to obtain multi-ion doped modified CBT piezoelectric ceramic sheets. S3. After removing the binder from the multi-ion doped modified CBT piezoelectric ceramic sheet obtained in S2, sinter it at a low temperature to obtain the sintered CBT piezoelectric ceramic sheet. S4. Coat the surface of the sintered CBT piezoelectric ceramic sheet obtained in S3 with silver paste and heat-keep it for silver firing. After cooling, the ceramic is placed in silicone oil for electric field polarization to obtain CBT piezoelectric ceramics modified with multiple ion doping.

4. The low-temperature preparation method of multi-ion doped modified CBT piezoelectric ceramic according to claim 3, characterized in that: In S1, the dispersion medium for ball milling is anhydrous ethanol, the mass ratio of the dispersion medium to the total amount of raw material is 1:1~1.5, the ball milling speed is 100~450 rpm, and the ball milling time is 10~24 h.

5. The low-temperature preparation method of multi-ion doped modified CBT piezoelectric ceramic according to claim 3, characterized in that: In S1, the pre-firing temperature is 850~950℃, and the pre-firing time is 2~4h.

6. The low-temperature preparation method of multi-ion doped modified CBT piezoelectric ceramic according to claim 3, characterized in that: In S2, the concentration of the polyvinyl alcohol solution is 5~10wt%, and the amount of polyvinyl alcohol solution used is 10~15wt% of the CBT piezoelectric ceramic powder modified by multi-ion doping.

7. The low-temperature preparation method of multi-ion doped modified CBT piezoelectric ceramic according to claim 3, characterized in that: In S2, the pressure for pressing the sheet is 10~20MPa, the diameter of the sheet is 10~15mm, and the thickness of the sheet is 0.8~1.2mm.

8. The low-temperature preparation method of multi-ion doped modified CBT piezoelectric ceramic according to claim 3, characterized in that: In S3, the temperature for debinding is 450~550℃, the time for debinding is 4~10h, the temperature for low-temperature sintering is 850~1000℃, and the time for low-temperature sintering is 2~4h.

9. The low-temperature preparation method of multi-ion doped modified CBT piezoelectric ceramic according to claim 3, characterized in that: In S4, the coating mass of silver paste is 5~15wt% of the mass of the sintered CBT piezoelectric ceramic sheet; the holding temperature for silver firing is 650~750℃, and the time is 10-20min.

10. The low-temperature preparation method of multi-ion doped modified CBT piezoelectric ceramic according to claim 3, characterized in that: In S4, the temperature of the silicone oil is 180~220℃; the electric field strength for electric field polarization is 5~10kV / mm; and the electric field polarization time is 15~30min.

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