A bismuth layer-structured high-temperature piezoelectric ceramic material and a method for preparing the same

Abstract

This invention relates to a bismuth layered high-temperature piezoelectric ceramic material and its preparation method, wherein the chemical formula of the bismuth layered high-temperature piezoelectric ceramic material is Bi₄Ti. 3‑2x Mo x W x O 12 The value of x ranges from 0.007 to 0.20. The beneficial effects of this invention are: the prepared bismuth layered high-temperature piezoelectric ceramic material exhibits excellent piezoelectric properties. When x = 0.10, the ceramic possesses a high piezoelectric coefficient (42.1 pC / N) and a high Curie temperature (680.6 °C). Furthermore, the piezoelectric coefficient changes by approximately 15% within the test temperature range of 30–500 °C, maintaining stable piezoelectric properties. These results demonstrate that the Bi4Ti of this invention… 3‑2x Mo x W x O 12 Ceramics may become a new lead-free candidate material for high-temperature vibration sensor applications.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric ceramic material preparation, specifically to a bismuth layered high-temperature piezoelectric ceramic material and its preparation method. Background Technology

[0002] Piezoelectric ceramics, as a key type of functional material for electromechanical energy conversion and coupling, have wide applications in numerous fields such as aerospace, electronics, advanced manufacturing, and medical systems. In recent years, increasingly stringent requirements have been placed on the operating temperature and reliability of their core functional components (especially piezoelectric devices). For example, devices such as acoustic logging tools, ultrasonic motors, and high-temperature piezoelectric vibration sensors all require stable operation in high-temperature environments, which directly demands that their core material—piezoelectric ceramics—possess excellent high-temperature performance stability.

[0003] Piezoelectric ceramics are the core components of high-temperature vibration sensors. Among existing material systems, bismuth titanate (Bi4Ti3O4) is a common choice. 12 High-temperature piezoelectric ceramics are characterized by their Curie temperature (T). C The high dielectric constant (>650 °C) and low dielectric loss of this material system make it the only feasible technical solution for high-temperature piezoelectric vibration sensors at 482 °C. However, this material system has an inherent drawback—the piezoelectric coefficient (d... 33 Low leakage current and high leakage current directly lead to the failure of related devices at high temperatures, which seriously restricts their practical application and is one of the key bottlenecks that have not yet been overcome in the development of 482°C high temperature vibration sensors.

[0004] To improve the piezoelectric properties of bismuth titanate ceramics, current research mainly focuses on two major technical approaches: ion doping (optimizing composition) and texturing processes (regulating microstructure). One approach involves ion doping, which involves introducing ions of different valence states and types for substitution. A-site substitution (such as La...) 3+ 、Nd 3+ 、Sm 3+ Replace Bi 3+ Although it can improve d 33 However, this often leads to T C The temperature drops significantly (even below 400 °C), failing to meet high-temperature requirements. Meanwhile, B-site replacement (such as V...) 5+ 、Nb 5+ Ta 5+ W 6+ and its combinations to replace Ti 4+ Doping can improve electrical properties, but multi-component doping significantly increases process complexity, hindering batch production and consistency control. On the other hand, texturing processes, through methods such as hot pressing, hot forging, and rapid plasma sintering, induce oriented grain alignment. This strategy can enable d... 33The ratio has been increased to over 30 pC / N, but the process itself is complex and has poor repeatability, which restricts its engineering application.

[0005] Therefore, how to maintain the high Curie temperature (T) of bismuth titanate-based materials C While maintaining its key advantage of >650 °C, its piezoelectric coefficient (d) is significantly improved. 33 This has become a core scientific problem and technological bottleneck that urgently needs to be overcome in the field of high-temperature piezoelectric ceramics.

[0006] Based on the above analysis, this invention designs Bi4Ti 3-2x Mo x W x O 12 A bismuth layered high-temperature piezoelectric ceramic material is presented, where x is the molar ratio, 0 ≤ x ≤ 0.02. Research results show that at x = 0.1, this ceramic exhibits an ultra-high piezoelectric coefficient (42.1 pC / N) and a high Curie temperature (680.6 ℃), while maintaining good piezoelectric stability within a temperature range of 30-500 ℃. Therefore, the Bi4Ti of this invention... 3-2x Mo x W x O 12 Bismuth layered high-temperature piezoelectric ceramic materials have great application potential in high-temperature vibration sensors. Summary of the Invention

[0007] In summary, to overcome the shortcomings of the prior art, the technical problem to be solved by the present invention is to provide a bismuth layered high-temperature piezoelectric ceramic material and its preparation method, which synergistically improves its piezoelectric properties while maintaining the high Curie temperature of the bismuth layered high-temperature piezoelectric ceramic material.

[0008] The technical solution of this invention to solve the above-mentioned technical problems is as follows: a bismuth layered high-temperature piezoelectric ceramic material, wherein the chemical composition of the bismuth layered high-temperature piezoelectric ceramic material is Bi4Ti. 3-2x Mo x W x O 12 The range of x is: 0.007≤x≤0.20.

[0009] Based on the above technical solution, the present invention can be further improved as follows:

[0010] Furthermore, the range of x is: 0.007≤x≤0.01.

[0011] Another object of the present invention is to provide a method for preparing the above-mentioned bismuth layered high-temperature piezoelectric ceramic material, comprising the following steps:

[0012] Step 1: Through precise ingredient proportioning, wet ball milling, and high-temperature pre-calcination, preliminary reaction raw material powder is obtained;

[0013] Step 2: Based on the preliminary reaction raw material powder obtained in Step 1, dry, fine, and non-agglomerated raw material powder is obtained by secondary wet ball milling and low-temperature drying;

[0014] Step 3: Based on the dry and fine raw material powder obtained in Step 2, granulation, pressing and molding and high-temperature debinding are carried out to obtain a columnar green body with moderate density, no impurities and no cracks.

[0015] Step 4: Based on the cylindrical green body obtained in Step 3, sintered ceramic sheets are obtained through precise temperature control sintering and natural cooling.

[0016] Step 5: Grind the ceramic sheet obtained in Step 4 to a thickness of 0.3-0.5 mm, clean and dry it, and then pass it through ion sputtering with a gold electrode to obtain a semi-finished product of bismuth layered high-temperature piezoelectric ceramic material.

[0017] Step 6: Polarize the semi-finished bismuth layered high-temperature piezoelectric ceramic material obtained in Step 5 to obtain the target bismuth layered high-temperature piezoelectric ceramic material.

[0018] Based on the above technical solution, the present invention can be further improved as follows:

[0019] Furthermore, step 1 specifically involves:

[0020] Step 1.1: Using Bi2O3, TiO2, WO3 and MoO3 with a purity ≥99% as raw materials, weigh and mix them according to their chemical formulas to obtain a mixture;

[0021] Step 1.2: Wet ball milling process is adopted, using anhydrous ethanol and zirconium oxide balls as ball milling media, and ball milling is carried out for 8 hours according to the mass ratio of mixture: zirconium balls: anhydrous ethanol of 1:2:2 to obtain a uniform first mixed slurry;

[0022] Step 1.3: After drying the first mixed slurry, place it in a muffle furnace, pre-calcine at 800℃ and keep it at that temperature for 4 hours to obtain the raw material powder of the initial reaction.

[0023] Furthermore, step 2 specifically involves:

[0024] Step 2.1: Add anhydrous ethanol and zirconium oxide balls to the preliminary reaction raw material powder obtained in Step 1, and place it in the nylon jar of a planetary ball mill for ball milling for 8 hours to obtain a finer and more uniform second mixed slurry.

[0025] Step 2.2: Place the second mixed slurry into a drying blower and dry it at 100-120°C to remove anhydrous ethanol, thereby obtaining a dry, fine, and non-agglomerated raw material powder.

[0026] Furthermore, step 3 specifically involves:

[0027] Step 3.1: The raw material powder obtained in Step 2 is granulated by using an 8% polyvinyl alcohol solution as a binder to fully mix and obtain uniform particles with good flowability.

[0028] Step 3.2: Press the granulated particles into cylindrical green bodies;

[0029] Step 3.3: Place the cylindrical green body into a muffle furnace, remove the adhesive at 500-700℃ and keep it at that temperature for 4-6 hours to remove the adhesive and residual impurities, and obtain a cylindrical green body with moderate density, no impurities and no cracks.

[0030] Furthermore, the diameter of the cylindrical green blank described in step 3.2 is 12 mm and its thickness is 2 mm.

[0031] Furthermore, step 4 specifically involves:

[0032] The cylindrical green body obtained in step 3 is placed in a muffle furnace, and the sintering temperature is controlled at 1050-1100℃ for 4 hours. After sintering, it is naturally cooled to room temperature to obtain sintered ceramic sheets.

[0033] Furthermore, in step 6, the polarization conditions are 180 °C, 6–8 kV / mm, and a polarization time of 30 min.

[0034] The beneficial effects of this invention are: the prepared bismuth layered high-temperature piezoelectric ceramic material exhibits excellent piezoelectric properties. When x = 0.10, this ceramic possesses a high piezoelectric coefficient (42.1 pC / N) and a high Curie temperature (680.6 °C). Furthermore, the piezoelectric coefficient changes by approximately 15% within the test temperature range of 30-500 °C, maintaining stable piezoelectric properties. These results demonstrate that the Bi4Ti of this invention… 3-2x Mo x W x O 12 Ceramics may become a new lead-free candidate material for high-temperature vibration sensor applications. Attached Figure Description

[0035] Figure 1 In this context, 'a' represents the concentration of different components at room temperature, and 'd' represents the concentration of different components at room temperature. 33 Trend graph, b represents the dielectric constant of different components at different temperatures;

[0036] Figure 2 Bi4Ti 3-2x Mo x W x O 12 ceramic components d 33 Temperature stability. Detailed Implementation

[0037] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0038] A bismuth layered high-temperature piezoelectric ceramic material, wherein the chemical formula of the bismuth layered high-temperature piezoelectric ceramic material is Bi4Ti. 3-2x Mo x W x O 12 Where x is the molar ratio, and its value range is: 0.007≤x≤0.20. Preferably, the value range of x is: 0.007≤x≤0.01.

[0039] The core properties of piezoelectric ceramics (piezoelectric coefficient d) 33 Curie temperature T C Temperature stability depends on the symmetry of its crystal structure, lattice integrity, and ion polarization ability. The material composition design described in this invention is based on the characteristics of the bismuth layered structure and the modification principle of ion doping to achieve a synergistic improvement in "high Curie temperature" and "ultra-high piezoelectric coefficient".

[0040] The preparation method of the above-mentioned bismuth layered high-temperature piezoelectric ceramic material includes the following steps:

[0041] Step 1: Weighing raw materials and performing a first ball milling and pre-calcination.

[0042] The initial reaction raw material powder was obtained through precise ingredient proportioning, wet ball milling, and high-temperature pre-calcination. Details are as follows:

[0043] Step 1.1: Using Bi2O3, TiO2, WO3 and MoO3 with a purity of ≥99% as raw materials, weigh and mix them according to their chemical composition formulas to obtain a mixture.

[0044] Step 1.2: Wet ball milling process is adopted, using anhydrous ethanol and zirconia balls as ball milling media, and ball milling is carried out for 8 hours at a mass ratio of mixture:zirconia balls:anhydrous ethanol of 1:2:2 to obtain a uniform first mixed slurry.

[0045] Step 1.3: After drying the first mixed slurry, place it in a muffle furnace, pre-calcine at 800 ℃ and keep it at that temperature for 4 h to obtain the raw material powder of the initial reaction.

[0046] Based on the principle that the performance of piezoelectric ceramics is extremely sensitive to the composition ratio, precise batching can ensure the accuracy and consistency of material composition, avoiding performance fluctuations caused by composition deviations, and laying the foundation for mass production. In wet ball milling, zirconia balls, with their high hardness and lack of impurity introduction, break up raw material agglomerates through collision and friction, increasing the contact area between raw materials. Anhydrous ethanol prevents particle agglomeration during drying and leaves no residue, thus solving the problem of incomplete reaction caused by raw material agglomeration and ensuring that subsequent doping ions can uniformly enter the parent lattice. Pre-firing, as the initial stage of solid-state reaction, at a high temperature of 900℃, can promote the initial reaction of various raw materials, while removing adsorbed water and volatile impurities, reducing volume shrinkage and deformation during subsequent sintering, avoiding cracking of the green body, and shortening the subsequent sintering reaction time and reducing energy consumption. Ultimately, it achieves the beneficial effects of initial raw material reaction, impurity removal, and uniform particle size.

[0047] Step 2, Secondary ball milling and drying

[0048] Based on the preliminary reactant powder obtained in step 1, a dry, fine, and agglomerated raw material powder was obtained through secondary wet ball milling and low-temperature drying. Details are as follows:

[0049] Step 2.1: Add anhydrous ethanol and zirconium oxide balls to the preliminary reaction raw material powder obtained in Step 1, and place it in the nylon jar of a planetary ball mill for ball milling for 8 hours to obtain a finer and more uniform second mixed slurry.

[0050] Step 2.2: Place the second mixed slurry into a drying blower and dry it at 100-120°C to remove anhydrous ethanol, thereby obtaining a dry, fine, and non-agglomerated raw material powder.

[0051] Based on the principle that pre-calcined powder may exhibit slight agglomeration and incomplete reaction, secondary ball milling can further refine the particles and increase the specific surface area, thus improving the Mo... 6+ W 6+ The more thorough contact and more uniform dispersion of the dopant particles with the parent material ensures complete integration of dopant ions into Bi4Ti3O during subsequent sintering. 12 The crystal lattice ensures the formation of a uniform bismuth layered structure and prevents the formation of a second phase, while also avoiding performance differences caused by uneven doping. During the drying process, a temperature of 100–120°C can quickly remove anhydrous ethanol (ethanol boiling point 78.5°C) while avoiding excessive temperature that could lead to powder oxidation or surface oxide film formation and agglomeration. The drying airflow can accelerate ethanol evaporation, ensuring uniform powder drying without moisture residue. Residual moisture can cause porosity and cracking in subsequent granulation green bodies. Therefore, low-temperature uniform drying can improve powder flowability, facilitating subsequent granulation and pressing, reducing green body defects, and ultimately achieving the beneficial effects of fine particle size, uniform mixing, and powder drying without agglomeration.

[0052] Step 3: Granulation, compression molding and debinding.

[0053] Based on the dry and fine raw material powder obtained in step 2, granulation, pressing, and high-temperature debinding are performed to obtain a cylindrical green body with moderate density, free of impurities, and free of cracks. Details are as follows:

[0054] In step 3.1, the raw material powder obtained in step 2 is granulated by using an 8% polyvinyl alcohol (PVA) solution as a binder to fully mix and obtain uniform particles with good flowability.

[0055] Step 3.2: Press the granulated particles into cylindrical green bodies with a diameter of 12 mm and a thickness of 2 mm, and control the appropriate pressure to ensure that the green bodies have moderate density, no cracks, and no delamination;

[0056] Step 3.3: Place the cylindrical green body into a muffle furnace, remove the adhesive at 500-700℃ and keep it at that temperature for 4-6 hours to remove the adhesive and residual impurities, and obtain a cylindrical green body with moderate density, no impurities and no cracks.

[0057] Based on the principle that dried powder particles are fine, have poor flowability, and are prone to loosening and cracking when directly pressed, PVA adhesive, with its excellent adhesion and film-forming properties, can encapsulate powder particles to form uniform large particles, improving powder flowability and compressibility. This solves the problems of cracking and delamination that easily occur during direct pressing, ensuring the quality of green body forming. Pressing molding uses external pressure to squeeze the particles together and expel air, forming a green body with high density. Moderate pressure control can avoid low density, large sintering shrinkage, and easy porosity deformation caused by insufficient pressure, and internal stress and sintering cracking caused by excessive pressure. At the same time, the cylindrical green body formed after pressing has precise dimensions, adapting to the requirements of high-temperature sensor devices, laying the foundation for subsequent sintering to form a uniform ceramic body. During the debinding process, a temperature of 500-700℃ (1050-1100℃ lower than the subsequent sintering temperature) allows PVA to be completely thermally decomposed into carbon dioxide and water, which are then volatilized and discharged. This process also removes residual trace amounts of moisture and impurities, preventing the adhesive from rapidly decomposing during sintering and generating a large amount of gas that could lead to cracking and increased porosity in the green body. Holding the temperature for 4-6 hours ensures complete decomposition of the adhesive and thorough removal of impurities, preventing residual adhesive from affecting the material's crystal structure and electrical properties. Ultimately, this results in a green body with good molding quality, no impurities, moderate density, and meets the requirements of adapter components.

[0058] Step 4, sintering and shaping

[0059] Based on the cylindrical green body obtained in step 3, sintered ceramic sheets are obtained through precise temperature-controlled sintering and natural cooling. Details are as follows:

[0060] The cylindrical green body obtained in step 3 is placed in a muffle furnace, and the sintering temperature is controlled at 1050-1100℃ for 4 hours. After sintering, it is naturally cooled to room temperature to obtain sintered ceramic sheets.

[0061] Based on the principle that sintering is the final stage of solid-state reaction and determines the structure and properties of ceramic materials, the high temperature of 1050–1100℃ can promote atomic diffusion, lattice rearrangement, and grain growth in the powder particles of the green body. The particles fuse and bond together to form a dense crystal structure, while simultaneously allowing Mo… 6+ and W 6+ Fully integrated with Bi4 Ti3O 12 Lattice, replacing Ti 4+ The material forms a uniform layered bismuth perovskite structure without the formation of a second phase. Precise control of sintering temperature and holding time is crucial for optimal results. Too low a temperature leads to slow atomic diffusion, insufficient particle fusion, low material density, uneven grain size, and poor piezoelectric and mechanical properties. Too high a temperature results in excessive grain growth, increased lattice defects, and the volatilization of Bi₂O₃ (volatile temperature approximately 1100℃) disrupts the component ratio, causing a decrease in Curie temperature and piezoelectric coefficient. A 4-hour holding time ensures sufficient atomic diffusion, uniform grain growth, and complete integration of dopant ions into the lattice. Natural cooling prevents cracking of the ceramic body caused by sudden temperature changes, ultimately achieving a material with high density, a complete crystal structure, no defects, no second phase, and a high piezoelectric coefficient (d at x=0.01). 33 =42.1pC / N), Curie temperature (680.6℃) and temperature stability all meet the design requirements. At the same time, the sintering process is simple, has good repeatability, does not require complex equipment, and is low in cost. It overcomes the shortcomings of existing texturing processes that are difficult to apply on a large scale, and provides a guarantee for the actual promotion of the material.

[0062] Step 5, Ion sputtering

[0063] The ceramic sheet obtained in step 4 is ground to a thickness of 0.3-0.5 mm, cleaned, dried, and then sputtered with a gold electrode to obtain a semi-finished product of a bismuth layered high-temperature piezoelectric ceramic material.

[0064] Step Six, Polarization

[0065] The semi-finished bismuth layered high-temperature piezoelectric ceramic material obtained in step five is polarized to obtain the target bismuth layered high-temperature piezoelectric ceramic material. The polarization conditions are 180 ℃, 6~8 kV / mm, and polarization time of 30 min.

[0066] Bi4Ti prepared in this invention 3-2x Mo x W x O 12 High-performance bismuth layered high-temperature piezoelectric ceramics Figure 1(a) shows the trend of piezoelectric coefficient of bismuth layered high-temperature piezoelectric ceramics with different compositions (0.08≤x≤0.12) as a function of x. Table 1 lists the piezoelectric coefficients and Curie temperatures of the corresponding different compositions. It can be seen that when x = 0.01, the piezoelectric coefficient of this ceramic is as high as 42.1 pC / N, and the Curie temperature is as high as 680.6 ℃. Figure 1 (b)). Simultaneously from Figure 2 It can be concluded that this composition maintains good thermal stability at 600 °C. These data are higher than most previously reported bismuth layered piezoelectric ceramics, indicating that the piezoelectric ceramic obtained in this invention has great application potential.

[0067] Table 1. Piezoelectric coefficients and Curie temperatures of different components

[0068]

[0069] 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 within the protection scope of the present invention.

Claims

1. A bismuth layered high-temperature piezoelectric ceramic material, characterized in that, The chemical formula of the bismuth layered high-temperature piezoelectric ceramic material is Bi4Ti. 3-2x Mo x W x O 12 The range of x is: 0.007≤x≤0.

20.

2. The bismuth layered high-temperature piezoelectric ceramic material according to claim 1, characterized in that, The range of x is: 0.007≤x≤0.

01.

3. A method for preparing a bismuth layered high-temperature piezoelectric ceramic material as described in claim 1 or 2, characterized in that, The steps include the following: Step 1: Through precise ingredient proportioning, wet ball milling, and high-temperature pre-calcination, preliminary reaction raw material powder is obtained; Step 2: Based on the preliminary reaction raw material powder obtained in Step 1, dry, fine, and non-agglomerated raw material powder is obtained by secondary wet ball milling and low-temperature drying; Step 3: Based on the dry and fine raw material powder obtained in Step 2, granulation, pressing and molding and high-temperature debinding are carried out to obtain a columnar green body with moderate density, no impurities and no cracks. Step 4: Based on the cylindrical green body obtained in Step 3, sintered ceramic sheets are obtained through precise temperature control sintering and natural cooling. Step 5: Grind the ceramic sheet obtained in Step 4 to a thickness of 0.3-0.5 mm, clean and dry it, and then pass it through ion sputtering with a gold electrode to obtain a semi-finished product of bismuth layered high-temperature piezoelectric ceramic material. Step 6: Polarize the semi-finished bismuth layered high-temperature piezoelectric ceramic material obtained in Step 5 to obtain the target bismuth layered high-temperature piezoelectric ceramic material.

4. The method for preparing the bismuth layered high-temperature piezoelectric ceramic material according to claim 3, characterized in that, Step 1 is as follows: Step 1.1: Using Bi2O3, TiO2, WO3 and MoO3 with a purity ≥99% as raw materials, weigh and mix them according to their chemical formulas to obtain a mixture; Step 1.2: Wet ball milling process is adopted, using anhydrous ethanol and zirconium oxide balls as ball milling media, and ball milling is carried out for 8 hours according to the mass ratio of mixture: zirconium balls: anhydrous ethanol of 1:2:2 to obtain a uniform first mixed slurry; Step 1.3: After drying the first mixed slurry, place it in a muffle furnace, pre-calcine at 800℃ and keep it at that temperature for 4 hours to obtain the raw material powder of the initial reaction.

5. The method for preparing the bismuth layered high-temperature piezoelectric ceramic material according to claim 3, characterized in that, Step 2 is as follows: Step 2.1: Add anhydrous ethanol and zirconium oxide balls to the preliminary reaction raw material powder obtained in Step 1, and place it in the nylon jar of a planetary ball mill for ball milling for 8 hours to obtain a finer and more uniform second mixed slurry. Step 2.2: Place the second mixed slurry into a drying blower and dry it at 100-120°C to remove anhydrous ethanol, thereby obtaining a dry, fine, and non-agglomerated raw material powder.

6. The method for preparing the bismuth layered high-temperature piezoelectric ceramic material according to claim 3, characterized in that, Step 3 specifically involves: In step 3.1, the raw material powder obtained in step 2 is granulated by using an 8% polyvinyl alcohol solution as a binder to fully mix and obtain uniform particles with good flowability. Step 3.2: Press the granulated particles into cylindrical green bodies; Step 3.3: Place the cylindrical green body into a muffle furnace, remove the adhesive at 500-700℃ and keep it at that temperature for 4-6 hours to remove the adhesive and residual impurities, and obtain a cylindrical green body with moderate density, no impurities and no cracks.

7. The method for preparing the bismuth layered high-temperature piezoelectric ceramic material according to claim 6, characterized in that, The cylindrical green blank mentioned in step 3.2 has a diameter of 12 mm and a thickness of 2 mm.

8. The method for preparing the bismuth layered high-temperature piezoelectric ceramic material according to claim 3, characterized in that, Step 4 is as follows: The cylindrical green body obtained in step 3 is placed in a muffle furnace, and the sintering temperature is controlled at 1050-1100℃ for 4 hours. After sintering, it is naturally cooled to room temperature to obtain sintered ceramic sheets.

9. The method for preparing the bismuth layered high-temperature piezoelectric ceramic material according to claim 3, characterized in that, In step 6, the polarization conditions are 180 °C, 6–8 kV / mm, and a polarization time of 30 min.

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