Lead metaniobate-based piezoelectric ceramics, methods of making and applications thereof

Abstract

The application relates to the technical field of functional ceramic materials, in particular to a lead metaniobate-based piezoelectric ceramic, a preparation method and application thereof. The high-dielectric high-curie-temperature lead metaniobate-based piezoelectric ceramic has a chemical formula of Pb 0.87‑x Ba 0.12 Ca 0.01 La x Nb 1.9 W 0.1 O6+0.1wt%CeO2+0.05wt%Cr2O3, wherein 0<=x<=0.015. The obtained lead metaniobate-based piezoelectric ceramic has the characteristics of excellent electrical performance and high curie temperature, and has a d 33 =105pC / N, k t =0.41, epsilon r =510, T c =536 DEG C, tan delta=0.45%, and has high dielectric performance and piezoelectric constant under the premise of high curie temperature, and the comprehensive performance is superior to that of the existing lead metaniobate-based piezoelectric ceramic.

Description

Technical Field

[0001] This invention relates to the field of functional ceramic materials technology, specifically to lead niobate-based piezoelectric ceramics, their preparation methods, and applications. Background Technology

[0002] Piezoelectric ceramics are functional ceramic materials that can convert mechanical energy into electrical energy and vice versa. They are mainly used in functional devices such as detectors, sensors, and transducers, playing a vital role in fields such as oil exploration, ultrasonic welding, industrial inspection, and aerospace. With the rapid development of modern technology, the application scenarios of piezoelectric devices have shifted from conventional environments to extreme high-temperature environments. In the aerospace field, high-temperature accelerometers with piezoelectric ceramics as their core components are mounted on the wings of space shuttles to monitor their operational status; in the oil exploration field, piezoelectric probe sensors need to maintain good temperature stability during drilling. Furthermore, there is a significant demand for high-temperature piezoelectric ceramics in fields such as high-temperature power equipment and automotive engines.

[0003] Currently, most piezoelectric ceramics used in the market are traditional lead zirconate titanate (PZT) piezoelectric ceramics. As a crucial pillar of the piezoelectric materials industry, PZT possesses advantages such as high piezoelectric coefficient, stable performance, high mechanical strength, and mature manufacturing processes. However, traditional PZT-based piezoelectric ceramics are limited by their relatively low Curie temperature (Ti). c (Approximately 360℃). In practical applications of piezoelectric devices, to prevent severe thermal depolarization and ensure safe and stable operation, their service operating temperature is typically strictly controlled at half the Curie temperature (i.e., 1 / 2T). c The inherent limitation of PZT piezoelectric ceramics (approximately 180℃) restricts their application in extreme high-temperature environments. Currently, piezoelectric single-crystal materials are used in some cases to meet special high-temperature piezoelectric requirements, but their preparation process is complex, costly, and has limited resistance to mechanical shock, hindering large-scale industrial applications. Therefore, exploring and developing novel high-temperature piezoelectric ceramics with relatively low cost, mature technology, and excellent overall performance is of great practical significance.

[0004] Lead niobate (PbNb₂O₆)-based piezoelectric ceramics possess advantages such as high Curie temperature, strong anisotropy, and good resistance to depolarization, showing great promise for applications in high-temperature environments. However, current PbNb₂O₆-based piezoelectric ceramics suffer from drawbacks such as low piezoelectric activity, low electromechanical coupling coefficient, and difficulty in sintering, limiting their practical applications. To address these shortcomings, researchers both domestically and internationally have employed methods such as ion doping and process improvements to overcome the relatively low piezoelectric performance. Currently, a common phenomenon exists in various piezoelectric ceramic systems where piezoelectric performance and Curie temperature are mutually restrictive; that is, piezoelectric ceramics prepared by conventional solid-state synthesis methods exhibit varying degrees of decrease in Curie temperature while improving piezoelectric performance. Therefore, researchers need to comprehensively consider the relationship between these two factors and develop PbNb₂O₆-based piezoelectric ceramics with excellent comprehensive performance for extreme high-temperature environments. This would play a significant role in promoting the upgrading of the petroleum exploration and related instrument industries and further advancing the field of high-temperature piezoelectricity. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a lead niobate-based piezoelectric ceramic with high piezoelectric properties and Curie temperature, low dielectric loss, and overall performance superior to commercially available lead niobate-based piezoelectric ceramics.

[0006] Another objective of this invention is to provide a method for preparing lead niobate-based piezoelectric ceramics, which has the advantages of simple preparation process, excellent electrical properties and low cost.

[0007] The third objective of this invention is to provide an application of lead niobate-based piezoelectric ceramics for use in high-temperature sensors and acoustic logging transducers.

[0008] This invention is achieved using the following technical solution: The lead niobate-based piezoelectric ceramic described herein has the chemical formula Pb. 0.87- x Ba 0.12 Ca 0.01 La x Nb 1.9 W 0.1 O6 + 0.1wt%CeO2 + 0.05wt%Cr2O3, where 0 ≤ x ≤ 0.015.

[0009] The x = 0, 0.005, 0.01, or 0.015.

[0010] The preparation method of the lead niobate-based piezoelectric ceramic includes the following steps: (1) Weigh the raw materials according to the stoichiometric ratio of the elements in the general chemical formula of lead niobate-based piezoelectric ceramic materials, and obtain the pre-synthesized powder by ball milling, drying and synthesis. (2) The powder is placed in a ball mill jar for secondary ball milling, discharge, drying, sieving and then granulation; (3) The granulated powder is pressed into blanks, and after debinding, it is sintered to obtain lead niobate-based piezoelectric ceramic sheets; (4) The piezoelectric ceramic is processed to obtain a standard circular piece with a diameter of 20 mm and a thickness of 2 mm, thereby obtaining a standard-sized piezoelectric ceramic material; (5) Coat the ceramic sheet obtained in step (4) with silver paste and perform a silver baking step to obtain a piezoelectric ceramic with silver electrodes; (6) Polarize the ceramic sheet with silver electrode in step (5) to obtain the lead niobate-based piezoelectric ceramic product.

[0011] In step (1), the raw materials are Pb3O4, BaCO3, CaCO3, La2O3, Nb2O5, WO3, CeO2, and Cr2O3.

[0012] In step (1), the ball mill jar is made of polyurethane, the ball milling medium is deionized water, and the mass ratio of water to raw material is 1:2; the ball milling speed is 50-60 r / min, and the time is 18-24 h.

[0013] The drying temperature is 100-150℃ and the time is 4-6 hours; the synthesis temperature is 850℃-870℃ and the time is 2-4 hours.

[0014] The granulation process involves granulating the sieved powder with a polyvinyl alcohol aqueous solution. The mass-to-volume ratio (g / mL) of the sieved powder to PVA is (9-11):1. The sieve mesh size is 100 mesh, and the resulting pellets are 25 mm in diameter, 3 mm thick, and have a density of 3.8 g / cm³. 3 -4.0g / cm 3 .

[0015] In step (3), the debinding conditions are to raise the temperature to 650℃-670℃ at a rate of 1℃ / min-2℃ / min, hold the temperature for 2h-3h, and then cool it with the furnace; the sintering conditions are to raise the temperature of the debinded sample to 500℃ at 3℃ / min, then raise the temperature to 1190℃-1230℃ at 2℃ / min, hold the temperature for 2h-4h, and then cool it with the furnace.

[0016] The polarization conditions in step (6) are: polarization temperature 140℃-160℃, polarization voltage 10kV-14kV, and polarization time 15min-30min.

[0017] The aforementioned lead niobate-based piezoelectric ceramics are used in high-temperature sensors and acoustic logging transducers.

[0018] Compared with the prior art, the beneficial effects of the present invention are: (1) The preparation process of the lead niobate-based piezoelectric ceramic material of the present invention is simple and has good repeatability, which makes the present invention meet the requirements for mass application in industry and has been mass-produced.

[0019] (2) The lead niobate-based piezoelectric ceramic material of the present invention has excellent comprehensive properties, and its d 33 =105pC / N, k t =0.41, ε r =510, T c =536℃, tanδ=0.45%, possessing both high dielectric properties and high piezoelectric constant under the premise of high Curie temperature, and its comprehensive performance is superior to existing lead niobate piezoelectric ceramics.

[0020] (3) The lead niobate-based piezoelectric ceramic materials of the present invention are all prepared using domestically produced industrial raw materials, which are low in cost and can be used in high-temperature sensors and acoustic logging transducers. Attached Figure Description

[0021] Figure 1 The image shows the X-ray diffraction pattern of the lead niobate-based piezoelectric ceramic prepared in Example 2.

[0022] Figure 2 The temperature spectrum of the high-temperature capacitor of the lead niobate-based piezoelectric ceramic prepared in Example 1 is shown.

[0023] Figure 3 The temperature spectrum of the high-temperature capacitor of the lead niobate-based piezoelectric ceramic prepared in Example 2.

[0024] Figure 4 The temperature spectrum of the high-temperature capacitor of the lead niobate-based piezoelectric ceramic prepared in Example 3 is shown.

[0025] Figure 5 The temperature spectrum of the high-temperature capacitor of the lead niobate-based piezoelectric ceramic prepared in Example 4.

[0026] Figure 6 The temperature spectrum of the high-temperature capacitor of the lead niobate-based piezoelectric ceramic prepared in Comparative Example 1.

[0027] Figure 7 The temperature spectrum of the high-temperature capacitor of the lead niobate-based piezoelectric ceramic prepared in Comparative Example 2. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below.

[0029] This invention provides a lead niobate-based piezoelectric ceramic, the core of which lies in the multi-element composite doping modification of the lead niobate (PbNb2O6) matrix material and the optimization of the preparation process, thereby improving the piezoelectric and dielectric properties of the material while maintaining a high Curie temperature.

[0030] Chemical formulas for ceramic materials: The piezoelectric ceramic proposed in this invention has the general chemical formula Pb. 0.87-x Ba 0.12 Ca 0.01 La x Nb 1.9 W 0.1 O6 + 0.1wt%CeO2 + 0.05wt%Cr2O3, where 0 ≤ x ≤ 0.015. This chemical formula is designed based on the following technical considerations: Matrix composition and solid solution formation: Lead metaniobate (PbNb2O6) belongs to the tungsten bronze structure and has a naturally high Curie temperature (approximately 570°C), making it an excellent matrix for high-temperature piezoelectric materials. This invention uses Ba... 2+ and Ca 2+ The ion partially substitutes Pb at the A site. 2+ Ions. Among them, Ba is introduced. 2+ It helps stabilize the tungsten bronze phase and effectively "softens" the ceramic, increasing the degree of freedom of domain wall movement, thus tending to increase the piezoelectric constant d. 33 and dielectric constant ε r Introducing a small amount of Ca 2+ This can regulate lattice distortion, which plays a positive role in stabilizing material properties, inhibiting abnormal grain growth, and maintaining a high Curie temperature. At the same time, the stoichiometric ratio of Pb at the A site and Nb at the B site is set to a non-ideal 1:2, and ion vacancies are pre-set at the A site and B site, which is beneficial for densification and performance control during subsequent sintering.

[0031] Donor doping modification: B-site donor doping: W 6+ The ion substitutes Nb at the B site 5+ Donor doping involves the substitution of low-valence ions by high-valence ions. This type of doping can compensate for charge by generating A-site lead vacancies, promoting liquid phase formation during sintering, lowering the sintering temperature, and increasing the density of ceramics. On the other hand, the donor doping effect helps to "soften" the material, i.e., reduce the coercive field and increase the activity of domain wall motion, thereby benefiting the improvement of piezoelectric and dielectric properties.

[0032] A-site donor doping: La 3+ The ion substitutes Pb at the A site 2+ Ions, also donor-doped. Their effect is similar to W. 6+Synergy further enhances the "soft" properties of ceramics. This is achieved by adjusting the La... 3+ The doping amount x (0 ≤ x ≤ 0.015) can finely control the balance between the piezoelectric properties and the Curie temperature of the material. Experimental data show that an appropriate amount of La... 3+ It can improve d 33 and ε r However, excessive doping may cause the Curie temperature to drop too quickly, deviating from the goal of high Curie temperature of this invention.

[0033] Synergistic effect of sintering aids: CeO2 (0.1 wt%) and Cr2O3 (0.05 wt%), added by weight percentage, mainly act as sintering aids and performance fine-tuning agents. CeO2 can effectively inhibit grain growth, resulting in a fine and uniform grain structure, which is beneficial to improving the stability of the material's mechanical and electrical properties. Cr2O3, as an effective sintering aid, can lower the sintering temperature and, to some extent, help reduce dielectric loss (tanδ). The combined addition of these two oxides synergistically improves the sintering characteristics and final overall electrical properties of the ceramic.

[0034] Regarding the preparation methods of ceramic materials: This invention employs a traditional solid-state reaction method to prepare the piezoelectric ceramic. This method is mature, cost-controllable, and suitable for industrial production. The raw materials used in this invention (Pb3O4, BaCO3, CaCO3, La2O3, Nb2O5, WO3, Cr2O3, CeO2) are all commercially available industrial-grade or analytical-grade reagents, widely available, and inexpensive, meeting the needs of mass production.

[0035] Raw materials and mixing: High-purity oxides (Pb3O4, Nb2O5, WO3, Cr2O3, CeO2) and carbonates (BaCO3, CaCO3) are used as raw materials to ensure the accuracy of the final product composition. Pb3O4 is chosen instead of PbO because of its higher reactivity in the pre-calcination stage and lower raw material cost. Wet ball milling (one-stage ball milling) is used, with appropriate material-to-water ratio, rotation speed, and time set to ensure uniform mixing of the various raw material powders, which is the basis for the subsequent solid-phase reaction to proceed fully.

[0036] Pre-firing (synthesis) and secondary ball milling: Pre-firing is carried out at 850℃-870℃ to allow the uniformly mixed raw materials to undergo a solid-phase reaction, initially synthesizing the target tungsten bronze phase structure. This temperature range was chosen to balance the reaction rate with preventing Pb volatilization and severe powder agglomeration. Secondary ball milling after pre-firing aims to break up the agglomerates formed during synthesis, reduce powder particle size, and improve the sintering activity of the powder, laying the foundation for obtaining high-density ceramic products.

[0037] Granulation and Molding: PVA solution is used for granulation to improve the flowability and filling properties of the powder, resulting in a more uniform density distribution within the blank during pressing and molding, thus preventing cracking or deformation during sintering due to uneven density. The set parameters, such as the ratio of powder to PVA and the sieve mesh size, are all designed to obtain granules suitable for dry pressing.

[0038] Debinding and sintering: Debonding: This is a crucial pretreatment step. Slow heating rate (1-2℃ / min) and holding at 650-670℃ ensure that the PVA adhesive can be slowly and completely decomposed and expelled without causing defects such as microcracks in the preform due to rapid gas escape.

[0039] Sintering: This is a crucial step in densifying the ceramic green body. The selection of sintering temperature (1190-1230℃) and holding time (2-4h) is critical, determining the final density, grain size, and electrical properties of the ceramic. The temperature range provided in this invention is an optimized sintering window for the specific chemical composition, within which a dense grain structure and excellent properties can be obtained. The segmented heating program helps ensure small internal and external temperature differences and uniform heating for large-sized samples.

[0040] It should be noted that in lead metaniobate systems, PbO exhibits a certain degree of volatility during high-temperature sintering (≥1190℃), which may affect the final stoichiometry and piezoelectric properties of the ceramic. The sintering furnace and alumina crucible used in this invention have undergone long-term use, resulting in a stable lead atmosphere within the furnace chamber and crucible. This effectively suppresses excessive PbO volatilization. Therefore, a conventional sintering process without additional protection can yield ceramic products with stable composition and excellent performance. If replacing equipment or crucibles initially, as a precaution, a small amount of lead atmosphere flakes can be placed inside the crucible during sintering to supplement the lead partial pressure within the furnace and ensure sintering quality. This measure can be flexibly selected according to actual production conditions without affecting the versatility and operability of the method described in this invention.

[0041] Post-processing (electrode preparation and polarization): After sintering, the ceramic sheet needs to be coated with silver paste and baked to form electrodes, providing conductive connections for polarization and performance testing. Polarization is achieved by applying a strong DC electric field (10-14kV, corresponding to a field strength of approximately 5-7kV / mm) at conditions above room temperature but below the Curie temperature (140-160℃), causing the spontaneous polarization electric dipole moment inside the ferroelectric body to preferentially align along the direction of the electric field. The selection of these polarization conditions aims to ensure sufficient polarization while avoiding electrical breakdown, thereby enabling the ceramic to exhibit a piezoelectric effect macroscopically.

[0042] Applications of ceramic materials: The piezoelectric ceramic prepared by this invention possesses both a high Curie temperature and excellent piezoelectric and dielectric properties. The high Curie temperature ensures stable piezoelectric characteristics even at high temperatures, making it less prone to thermal depolarization and failure. The excellent piezoelectric and dielectric properties mean that it exhibits high electromechanical conversion efficiency and sensitivity when used as a sensing or transducer element. Therefore, this material is particularly suitable for high-temperature sensors (such as those used for vibration monitoring of aero-engines and high-temperature pressure monitoring in industrial processes) and acoustic logging transducers (used in downhole high-temperature and high-pressure environments during oil exploration) where both operating temperature and performance requirements are high.

[0043] The technical solution of the present invention will be described in detail below through specific embodiments.

[0044] Example 1 A method for preparing lead niobate-based piezoelectric ceramic materials includes the following steps: According to the chemical formula Pb 0.87 Ba 0.12 Ca 0.01 Nb 1.9 W 0.1 Weigh out 500g of dried raw materials: Pb3O4 (99.66% purity), BaCO3 (99.10% purity), CaCO3 (99% purity), Nb2O5 (99% purity), WO3 (99.99% purity), CeO2 (99% purity), and Cr2O3 (99% purity). Place the weighed raw materials into a ball mill jar and add 1000ml of deionized water. The sample was ball-milled for 18 hours on a roller mill. The slurry after ball milling was placed in an oven and dried at 150°C. After drying, the sample was ground into powder using a mortar and pestle and passed through an 80-mesh sieve. The powder was then placed in a crucible and kept at 850°C for 2 hours. The pre-calcined sample was ground into powder using a mortar and pestle and placed in a ball mill jar. 1000 ml of deionized water was added, and the sample was ball-milled a second time for 24 hours. The ball-milled slurry was separated from the zirconium balls and placed in an oven to dry at 150°C. The dried base material was then ground and passed through a 100-mesh sieve to obtain the powder base material.

[0045] Weigh 200g of powder base material, then add 20ml of 6% PVA solution and grind. After pressing into large pieces, crush into smaller pieces and pass through a 100-mesh sieve. The resulting product is a round disc with a diameter of 25mm, a thickness of 3mm, and a density of 3.95g / cm³. 3The molded sample was placed in a furnace for debinding under the following conditions: heating to 650℃ at a rate of 1℃ / min, holding for 2 hours, and then cooling in the furnace to obtain a ceramic green body. The green body was then sintered in a muffle furnace: the temperature was increased from room temperature to 500℃ at a rate of 3℃ / min, then increased to 1200℃ at a rate of 2℃ / min, held for 2 hours, and then cooled in the furnace to prepare a lead-niobate-based piezoelectric ceramic material. The piezoelectric ceramic was processed to obtain a standard circular disc with a diameter of 20mm and a thickness of 2mm (referencing national standard GB / T2414.1-1998), obtaining a standard-sized piezoelectric ceramic material. The ceramic disc was coated with silver paste and baked to obtain a piezoelectric ceramic with silver electrodes. The ceramic disc with silver electrodes was polarized under the following conditions: polarization temperature 160℃, polarization voltage 10000V, and polarization time 30min, to obtain the finished lead-niobate-based piezoelectric ceramic.

[0046] Example 2 A method for preparing lead niobate-based piezoelectric ceramic materials includes the following steps: According to the chemical formula Pb 0.865 Ba 0.12 Ca 0.01 La 0.005 Nb 1.9 W 0.1 Weigh out 500g of dried Pb3O4 (99.66% purity), BaCO3 (99.10% purity), CaCO3 (99% purity), La2O3 (99.99% purity), Nb2O5 (99% purity), WO3 (99.99% purity), CeO2 (99% purity), and Cr2O3 (99% purity) raw materials respectively. Place them in a ball mill jar and add 100... 0 ml of deionized water was used to ball mill the sample for 18 hours on a roller mill. The slurry after ball milling was placed in an oven and dried at 150°C. After drying, the sample was ground into powder using a mortar and pestle and passed through an 80-mesh sieve. The powder was then placed in a crucible and kept at 850°C for 2 hours. The pre-calcined sample was ground into powder using a mortar and pestle and placed in a ball mill jar. 1000 ml of deionized water was added, and the sample was ball milled a second time for 24 hours. The slurry after ball milling was separated from the zirconium balls and placed in an oven to dry at 150°C. The dried base material was then ground and passed through a 100-mesh sieve to obtain the powder base material.

[0047] Weigh 200g of powder base material, then add 20ml of 6% PVA solution and grind. After pressing into large pieces, crush into smaller pieces and pass through a 100-mesh sieve. The resulting product is a round disc with a diameter of 25mm, a thickness of 3mm, and a density of 3.93g / cm³. 3The molded sample was placed in a furnace for debinding under the following conditions: heating to 650℃ at a rate of 1℃ / min, holding for 2 hours, and then cooling in the furnace to obtain a ceramic green body. The green body was then sintered in a muffle furnace: the temperature was increased from room temperature to 500℃ at a rate of 3℃ / min, then increased to 1200℃ at a rate of 2℃ / min, held for 2 hours, and then cooled in the furnace to prepare a lead-niobate-based piezoelectric ceramic material. The piezoelectric ceramic was processed to obtain a standard circular disc with a diameter of 20mm and a thickness of 2mm (referencing national standard GB / T2414.1-1998), obtaining a standard-sized piezoelectric ceramic material. The ceramic disc was coated with silver paste and baked to obtain a piezoelectric ceramic with silver electrodes. The ceramic disc with silver electrodes was polarized under the following conditions: polarization temperature 160℃, polarization voltage 10000V, and polarization time 30min, to obtain the finished lead-niobate-based piezoelectric ceramic.

[0048] Example 3 A method for preparing lead niobate-based piezoelectric ceramic materials includes the following steps: According to the chemical formula Pb 0.86 Ba 0.12 Ca 0.01 La 0.01 Nb 1.9 W 0.1 Weigh out 500g of dried Pb3O4 (99.66% purity), BaCO3 (99.10% purity), CaCO3 (99% purity), La2O3 (99.99% purity), Nb2O5 (99% purity), WO3 (99.99% purity), CeO2 (99% purity), and Cr2O3 (99% purity) raw materials respectively. Place them in a ball mill jar and add 100... 0 ml of deionized water was used to ball mill the sample for 18 hours on a roller mill. The slurry after ball milling was placed in an oven and dried at 150°C. After drying, the sample was ground into powder using a mortar and pestle and passed through an 80-mesh sieve. The powder was then placed in a crucible and kept at 850°C for 2 hours. The pre-calcined sample was ground into powder using a mortar and pestle and placed in a ball mill jar. 1000 ml of deionized water was added, and the sample was ball milled a second time for 24 hours. The slurry after ball milling was separated from the zirconium balls and placed in an oven to dry at 150°C. The dried base material was then ground and passed through a 100-mesh sieve to obtain the powder base material.

[0049] Weigh 200g of powder base material, then add 20ml of 6% PVA solution and grind. After pressing into large pieces, crush into smaller pieces and pass through a 100-mesh sieve. The resulting product is a round disc with a diameter of 25mm, a thickness of 3mm, and a density of 3.96g / cm³. 3The molded sample was placed in a furnace for debinding under the following conditions: heating to 650℃ at a rate of 1℃ / min, holding for 2 hours, and then cooling in the furnace to obtain a ceramic green body. The green body was then sintered in a muffle furnace: the temperature was increased from room temperature to 500℃ at a rate of 3℃ / min, then increased to 1200℃ at a rate of 2℃ / min, held for 2 hours, and then cooled in the furnace to prepare a lead-niobate-based piezoelectric ceramic material. The piezoelectric ceramic was processed to obtain a standard circular disc with a diameter of 20mm and a thickness of 2mm (referencing national standard GB / T2414.1-1998), obtaining a standard-sized piezoelectric ceramic material. The ceramic disc was coated with silver paste and baked to obtain a piezoelectric ceramic with silver electrodes. The ceramic disc with silver electrodes was polarized under the following conditions: polarization temperature 160℃, polarization voltage 10000V, and polarization time 30min, to obtain the finished lead-niobate-based piezoelectric ceramic.

[0050] Example 4 A method for preparing lead niobate-based piezoelectric ceramic materials includes the following steps: According to the chemical formula Pb 0.855 Ba 0.12 Ca 0.01 La 0.015 Nb 1.9 W 0.1 Weigh out 500g of dried Pb3O4 (99.66% purity), BaCO3 (99.10% purity), CaCO3 (99% purity), La2O3 (99.99% purity), Nb2O5 (99% purity), WO3 (99.99% purity), CeO2 (99% purity), and Cr2O3 (99% purity) raw materials respectively. Place them in a ball mill jar and add 100... 0 ml of deionized water was used to ball mill the sample for 18 hours on a roller mill. The slurry after ball milling was placed in an oven and dried at 150°C. After drying, the sample was ground into powder using a mortar and pestle and passed through an 80-mesh sieve. The powder was then placed in a crucible and kept at 850°C for 2 hours. The pre-calcined sample was ground into powder using a mortar and pestle and placed in a ball mill jar. 1000 ml of deionized water was added, and the sample was ball milled a second time for 24 hours. The slurry after ball milling was separated from the zirconium balls and placed in an oven to dry at 150°C. The dried base material was then ground and passed through a 100-mesh sieve to obtain the powder base material.

[0051] Weigh 200g of powder base material, then add 20ml of 6% PVA solution and grind. After pressing into large pieces, crush into smaller pieces and pass through a 100-mesh sieve. The resulting product is a round disc with a diameter of 25mm, a thickness of 3mm, and a density of 3.95g / cm³. 3The molded sample was placed in a furnace for debinding under the following conditions: heating to 650℃ at a rate of 1℃ / min, holding for 2 hours, and then cooling in the furnace to obtain a ceramic green body. The green body was then sintered in a muffle furnace: the temperature was increased from room temperature to 500℃ at a rate of 3℃ / min, then increased to 1200℃ at a rate of 2℃ / min, held for 2 hours, and then cooled in the furnace to prepare a lead-niobate-based piezoelectric ceramic material. The piezoelectric ceramic was processed to obtain a standard circular disc with a diameter of 20mm and a thickness of 2mm (referencing national standard GB / T2414.1-1998), obtaining a standard-sized piezoelectric ceramic material. The ceramic disc was coated with silver paste and baked to obtain a piezoelectric ceramic with silver electrodes. The ceramic disc with silver electrodes was polarized under the following conditions: polarization temperature 160℃, polarization voltage 10000V, and polarization time 30min, to obtain the finished lead-niobate-based piezoelectric ceramic.

[0052] Comparative Example 1 A method for preparing lead niobate-based piezoelectric ceramic materials includes the following steps: According to the chemical formula Pb 0.88 Ba 0.12 Nb 1.9 W 0.1 Weigh out 500g of dried Pb3O4 (99.66% purity), BaCO3 (99.10% purity), Nb2O5 (99% purity), WO3 (99.99% purity), CeO2 (99% purity), and Cr2O3 (99% purity) raw materials respectively. Place them in a ball mill jar and add 1000ml of deionized water. Then, ball mill the materials on a roller mill. After 18 hours of ball milling, the slurry was placed in an oven and dried at 150°C. After drying, the sample was ground into powder using a mortar and pestle and passed through an 80-mesh sieve. The powder was then placed in a crucible and kept at 850°C for 2 hours. The pre-calcined sample was ground into powder using a mortar and pestle and placed in a ball mill jar. 1000 ml of deionized water was added, and the sample was ball milled a second time for 24 hours. The ball-milled slurry was separated from the zirconium balls and placed in an oven to dry at 150°C. The dried base material was then ground and passed through a 100-mesh sieve to obtain the powder base material.

[0053] Weigh 200g of powder base material, then add 20ml of 6% PVA solution and grind. After pressing into large pieces, crush into smaller pieces and pass through a 100-mesh sieve. The resulting product is a round disc with a diameter of 25mm, a thickness of 3mm, and a density of 3.95g / cm³. 3The molded sample was placed in a furnace for debinding under the following conditions: heating to 650℃ at a rate of 1℃ / min, holding for 2 hours, and then cooling in the furnace to obtain a ceramic green body. The green body was then sintered in a muffle furnace: the temperature was increased from room temperature to 500℃ at a rate of 3℃ / min, then increased to 1200℃ at a rate of 2℃ / min, held for 2 hours, and then cooled in the furnace to prepare a lead-niobate-based piezoelectric ceramic material. The piezoelectric ceramic was processed to obtain a standard circular disc with a diameter of 20mm and a thickness of 2mm (referencing national standard GB / T2414.1-1998), obtaining a standard-sized piezoelectric ceramic material. The ceramic disc was coated with silver paste and baked to obtain a piezoelectric ceramic with silver electrodes. The ceramic disc with silver electrodes was polarized under the following conditions: polarization temperature 160℃, polarization voltage 10000V, and polarization time 30min, to obtain the finished lead-niobate-based piezoelectric ceramic.

[0054] Comparative Example 2 A method for preparing lead niobate-based piezoelectric ceramic materials includes the following steps: According to the chemical formula Pb 0.875 Ba 0.12 Ca 0.005 Nb 1.9 W 0.1 Weigh out 500g of dried raw materials: Pb3O4 (99.66% purity), BaCO3 (99.10% purity), CaCO3 (99% purity), Nb2O5 (99% purity), WO3 (99.99% purity), CeO2 (99% purity), and Cr2O3 (99% purity). Place the weighed raw materials into a ball mill jar and add 1000ml of deionized water. The sample was ball-milled for 18 hours on a roller mill. The slurry after ball milling was placed in an oven and dried at 150°C. After drying, the sample was ground into powder using a mortar and pestle and passed through an 80-mesh sieve. The powder was then placed in a crucible and kept at 850°C for 2 hours. The pre-calcined sample was ground into powder using a mortar and pestle and placed in a ball mill jar. 1000 ml of deionized water was added, and the sample was ball-milled a second time for 24 hours. The ball-milled slurry was separated from the zirconium balls and placed in an oven to dry at 150°C. The dried base material was then ground and passed through a 100-mesh sieve to obtain the powder base material.

[0055] Weigh 200g of powder base material, then add 20ml of 6% PVA solution and grind. After pressing into large pieces, crush into smaller pieces and pass through a 100-mesh sieve. The resulting product is a round disc with a diameter of 25mm, a thickness of 3mm, and a density of 3.93g / cm³. 3The molded sample was placed in a furnace for debinding under the following conditions: heating to 650℃ at a rate of 1℃ / min, holding for 2 hours, and then cooling in the furnace to obtain a ceramic green body. The green body was then sintered in a muffle furnace: the temperature was increased from room temperature to 500℃ at a rate of 3℃ / min, then increased to 1200℃ at a rate of 2℃ / min, held for 2 hours, and then cooled in the furnace to prepare a lead-niobate-based piezoelectric ceramic material. The piezoelectric ceramic was processed to obtain a standard circular disc with a diameter of 20mm and a thickness of 2mm (referencing national standard GB / T2414.1-1998), obtaining a standard-sized piezoelectric ceramic material. The ceramic disc was coated with silver paste and baked to obtain a piezoelectric ceramic with silver electrodes. The ceramic disc with silver electrodes was polarized under the following conditions: polarization temperature 160℃, polarization voltage 10000V, and polarization time 30min, to obtain the finished lead-niobate-based piezoelectric ceramic.

[0056] The test data for Examples 1-4 and Comparative Examples 1-2 are shown in Table 1.

[0057] Table 1: Test data of Examples 1-4 and Comparative Examples 1-2

[0058] According to the data in Table 1, Example 2 of this invention prepared a lead niobate-based piezoelectric ceramic material with a doping amount of x=0.005, and its relative permittivity ε r and piezoelectric constant d 33 The performance of Example 2 is superior to that of the comparative piezoelectric ceramic material. It not only possesses excellent piezoelectric properties but also maintains a high Curie temperature, exhibiting relatively small capacitance change at 300°C. The results demonstrate that this invention can effectively improve the dielectric constant, piezoelectric constant, and electromechanical coupling coefficient of lead niobate-based piezoelectric ceramic materials, resulting in materials with excellent overall performance.

[0059] The above parameters were tested according to the national standards GB / T3389-2008 "Test Methods for Performance Parameters of Piezoelectric Ceramic Materials" and GB / T2414.1-1998 "Test Methods for Performance of Piezoelectric Ceramic Materials: Radial Tensile Vibration Mode of Circular Sheets". 33 Using quasi-static d 33 The tester obtained the following result: k t The resonant and anti-resonant frequencies of the sample were determined using the bridge method and obtained from tables; the capacitance and tanδ were determined using a capacitance bridge instrument; and the relative permittivity was calculated using a formula. ; C T Piezoelectric ceramic capacitor, unit: F; t: Thickness of the piezoelectric ceramic, in mm; d: Diameter of the piezoelectric ceramic, unit: mm; ε0: Vacuum permittivity, 8.854 × 10⁻⁶ -12 F / m.

[0060] The following is a brief description of the embodiments of the present invention and the accompanying drawings with reference to the comparative examples: Figure 1 The image shows the X-ray diffraction (XRD) pattern of the lead niobate-based piezoelectric ceramic prepared in Example 2. As can be seen from the figure, all diffraction peaks can be indexed to an orthorhombic tungsten bronze structure, with no obvious impurity phase peaks, indicating that the doping ions (such as La) are... 3+ W 6+ (etc.) has been successfully dissolved into the main phase lattice, forming a single solid solution.

[0061] Figures 2-5 The high-temperature capacitance temperature spectrum (i.e., relative permittivity ε) of the lead niobate-based piezoelectric ceramics prepared in Examples 1 to 4 are shown below. r (The curve showing the change of dielectric constant with temperature T). The temperature corresponding to the peak value of the dielectric constant in the figure is the Curie temperature T. c As can be seen from the figure: Figure 2 (Example 1, x=0)T c ≈558℃; Figure 3 (Example 2, x=0.005)T c ≈536℃; Figure 4 (Example 3, x=0.01)T c ≈506℃; Figure 5 (Example 4, x=0.015)T c ≈492℃. Data shows that as the La doping concentration changes, the temperature of the material increases. c It exhibits certain nonlinear fluctuations; in particular, Example 2, while obtaining good piezoelectric performance, still maintains a high Curie temperature above 500°C, achieving a good balance between piezoelectric activity and temperature resistance.

[0062] Figure 6 and Figure 7 The images show the high-temperature capacitance temperature spectra of the lead niobate-based piezoelectric ceramics prepared in Comparative Example 1 and Comparative Example 2, respectively. Specifically, the T1 of Comparative Example 1 is shown below. c Approximately 568℃, compared to T in Comparative Example 2. c The temperature is approximately 565°C. Compared to the comparative example, the embodiments of the present invention, through multi-element composite doping design, effectively improve the dielectric and piezoelectric properties of the material while maintaining a high Curie temperature (>500°C, superior to conventional piezoelectric ceramics) to meet the requirements of high-temperature applications.

Claims

1. A lead metaniobate-based piezoelectric ceramic, characterized in that, The chemical formula of the piezoelectric ceramic material is Pb 0.87- x Ba 0.12 Ca 0.01 La x Nb 1.9 W 0.1 O6 + 0.1wt%CeO2 + 0.05wt%Cr2O3, where 0 ≤ x ≤ 0.

015.

2. The lead metaniobate-based piezoelectric ceramic according to claim 1, characterized in that, The x = 0, 0.005, 0.01, or 0.

015.

3. A method for preparing lead niobate-based piezoelectric ceramics according to claim 1 or 2, characterized in that, Includes the following steps: (1) Weigh the raw materials according to the stoichiometric ratio, and perform ball milling, drying and synthesis to obtain pre-synthesized powder; (2) The pre-synthesized powder is subjected to secondary ball milling, drying, sieving and granulation to obtain the granulated powder to be pressed; (3) The granulated powder is pressed into shape, and after debinding and sintering, a lead niobate-based piezoelectric ceramic sheet is obtained; (4) The piezoelectric ceramic sheet is processed, coated with electrodes and polarized to obtain the lead niobate-based piezoelectric ceramic product.

4. The method for preparing lead niobate-based piezoelectric ceramics according to claim 3, characterized in that, In step (1), the raw materials are Pb3O4, BaCO3, CaCO3, La2O3, Nb2O5, WO3, CeO2, and Cr2O3.

5. The method for preparing lead niobate-based piezoelectric ceramics according to claim 4, characterized in that, The conditions for the first ball milling in step (1) are as follows: deionized water is used as the ball milling medium, the mass ratio of raw material to medium is 1:2, the ball milling speed is 50-60 r / min, and the ball milling time is 18-24 h.

6. The method for preparing lead niobate-based piezoelectric ceramics according to claim 3, characterized in that, The synthesis conditions in step (1) are: heat preservation at 850℃-870℃ for 2-4 hours.

7. The method for preparing lead niobate-based piezoelectric ceramics according to claim 3, characterized in that, In step (2), polyvinyl alcohol aqueous solution is used as a binder for granulation, and the mass-volume ratio of the powder obtained after sieving to the polyvinyl alcohol aqueous solution is (9-11):

1.

8. The method for preparing lead niobate-based piezoelectric ceramics according to claim 3, characterized in that, In step (3), the debinding conditions are as follows: the temperature is increased to 650℃-670℃ at a rate of 1℃ / min-2℃ / min, held for 2h-3h, and then cooled with the furnace; the sintering conditions are as follows: the debinded sample is heated to 500℃ at a rate of 3℃ / min, then heated to 1190℃-1230℃ at a rate of 2℃ / min, held for 2h-4h, and then cooled with the furnace.

9. The method for preparing lead niobate-based piezoelectric ceramics according to claim 3, characterized in that, The polarization treatment conditions in step (4) are: applying a voltage of 10-14kV at a temperature of 140-160℃ for 15-30 minutes.

10. An application of the lead niobate-based piezoelectric ceramic according to claim 1 or 2, characterized in that, Used in high-temperature sensors or acoustic logging transducers.

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