High-temperature piezoelectric ceramic material, preparation method and application

Abstract

The application discloses a high-temperature piezoelectric ceramic material, a preparation method and application, and belongs to the high-temperature piezoelectric ceramic material field. The application provides a high-temperature piezoelectric ceramic material, which is a samarium oxide doped lead ytterbium niobate-lead titanate piezoelectric ceramic material. The material is prepared by doping Sm2O3 in a lead ytterbium niobate-lead titanate binary system, and has high Curie temperature and further improved piezoelectric performance. Meanwhile, compared with existing ceramics, the piezoelectric performance of the ceramic at high temperature is more excellent. The application provides a preparation method of the high-temperature piezoelectric ceramic material, which can avoid the occurrence of a second phase in the ceramic, successfully realize stable sintering of the PYN-PT based material, and the ceramic prepared by the method has uniform particle size and high density. The preparation method has the advantages of simple process, low sintering temperature, low cost and suitability for large-scale industrial production, and has a wide application prospect in the field of high-temperature piezoelectric materials and devices.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature piezoelectric ceramic materials, and in particular to a high-temperature piezoelectric ceramic material, its preparation method and its application. Background Technology

[0002] With the rapid development of high technology, the application scope of piezoelectric materials has been further expanded. Some important fields urgently need electronic devices that can work stably at high temperatures, such as high-power ultrasonic transducers used in industrial ultrasonic processing and ultrasonic welding, high-temperature ultrasonic positioning detectors used in nuclear reactors, and fuel injection piezoelectric valves used in internal combustion engines. The manufacturing of these electronic devices must use high-temperature piezoelectric ceramic materials with high Curie temperature and excellent piezoelectric properties to ensure that piezoelectric devices can work normally in a wide temperature range.

[0003] Currently, lead zirconate titanate ceramics are widely used in industry, but these lead zirconate titanate piezoelectric ceramics are difficult to simultaneously meet the above requirements: for example, although PZT-5A piezoelectric ceramics have a high Curie temperature (T... c (approximately 365℃), but its piezoelectric properties are relatively poor (d 33 Approximately 374 pC / N); PZT-5H has relatively good piezoelectric properties (d 33 Approximately 593 pC / N), but because the Curie temperature was too low (T... c The temperature of high-temperature piezoelectric ceramics (approximately 193℃) is unsuitable for use at higher temperatures. While piezoelectric ceramics with high Curie temperatures, such as tungsten bronze or bismuth layered structures, can be used above 300℃, their piezoelectric properties are relatively low, failing to meet the requirements for high-performance electromechanical applications. Therefore, developing high-temperature piezoelectric materials with excellent performance, low cost, and good temperature stability has become a current research hotspot.

[0004] Pb(Yb 0.5 Nb 0.5 PbTiO3 (PYN-PT) is a binary ceramic system with a Curie temperature of T0. c At approximately 370℃, it can withstand high-temperature environments while maintaining good piezoelectric properties, thus improving the operating temperature range of piezoelectric devices. Furthermore, its cost is relatively low and its synthesis process is relatively simple. Therefore, Pb(Yb) 0.5 Nb 0.5PbTiO3-O3 piezoelectric ceramics are a ceramic system with significant research and practical application value. However, the perovskite structure of PYN-PT itself has poor stability, making the preparation of single-phase perovskite PYN-PT difficult, and its piezoelectric properties are relatively low, which greatly limits its application. Existing research has shown that elemental doping can improve the piezoelectric properties of lead-based perovskite iron piezoelectric ceramics, but the Curie temperature of the piezoelectric material often decreases significantly after doping modification. Therefore, developing PYN-PT-based high-temperature piezoelectric ceramic materials with superior piezoelectric properties while ensuring a high Curie temperature is of significant research and application value. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a high-temperature piezoelectric ceramic material, its preparation method, and its application.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A method for preparing a high-temperature piezoelectric ceramic material includes the following steps:

[0008] (1) According to (1-x)Pb(Yb 0.5 Nb 0.5 The stoichiometric ratio of YbNbO4, PbO, TiO2 and Sm2O3 was determined by weighing YbNbO4, PbO, TiO2 and Sm2O3 respectively, mixing the raw materials and then ball milling them once. After drying, a mixed powder was obtained; wherein, x = 0.45~0.52, y = 0.05~2;

[0009] (2) The mixed powder is pre-fired at 800-900℃ for more than 2 hours. After pre-firing, it is cooled to room temperature to obtain ceramic powder. Then, it is subjected to secondary ball milling, drying, grinding, granulation and sieving to obtain powder with uniform particles.

[0010] (3) The uniformly sized powder is pressed into a blank to obtain a green body; the green body is buried in a crucible containing the ceramic powder and kept at 500-600℃ to remove organic matter; then, a multi-stage sintering annealing method is used for sintering:

[0011] The temperature is raised from room temperature to 1050–1100℃, then cooled in the furnace to 900–1000℃, held at 900–1000℃ for 2–4 hours, and then allowed to cool naturally to room temperature.

[0012] Annealing is performed at 800–900℃ for 1–2 hours, followed by natural cooling to room temperature in the furnace to obtain high-temperature piezoelectric ceramic materials.

[0013] Furthermore, in step (1), the amount of PbO added is 2 to 6% excess of its own stoichiometry.

[0014] Furthermore, in step (3), the temperature is increased to 1050-1100℃ at room temperature at a rate of 3-5℃ / min;

[0015] During annealing, the temperature is increased to 800-900℃ at a rate of 8-10℃ / min.

[0016] Furthermore, step (3) is followed by silver polarization.

[0017] Further: the high-temperature piezoelectric ceramic material is polished, silver paste is coated on the surface, and the silver paste is sintered and then naturally cooled to room temperature; subsequently, the silver-coated ceramic is placed in silicone oil and a DC electric field is applied to polarize it.

[0018] A high-temperature piezoelectric ceramic material with the general chemical formula (1-x)Pb(Yb 0.5 Nb 0.5 O3-xPbTiO3–ymol%Sm2O3, belongs to the perovskite type structure, where 0.45≤x≤0.52 and 0.05≤y≤2.

[0019] Furthermore, when x = 0.48–0.52 and y = 0.05–2, it has a quasi-isomorphic phase boundary.

[0020] Furthermore, the small-signal piezoelectric coefficient d 33 =238~584pC / N@25℃, d 33 =320~578pC / N@200℃, d 33 =320~457pC / N@300℃; Large-signal piezoelectric coefficient d 33 *=305~613pm / V@25℃,d 33 * = 394~757pm / V@200℃; Curie temperature is T c =316~380℃;

[0021] Electrostriction S = 0.18–0.27% @ 25℃, S = 0.24–0.30% @ 200℃.

[0022] Furthermore, the piezoelectric devices are manufactured to operate at temperatures ranging from room temperature to 300°C.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] This invention provides a high-temperature piezoelectric ceramic material, specifically a samarium oxide-doped lead ytterbate-lead titanate piezoelectric ceramic material. By doping Sm₂O₃ into the lead ytterbate-lead titanate binary system, the resulting material exhibits both a high Curie temperature and further enhanced piezoelectric properties. Specifically, testing and analysis revealed that: ① the Curie temperature of this high-temperature piezoelectric ceramic system is not lower than 316℃ and can reach a maximum of 380℃; ② at room temperature, the piezoelectric coefficient of this high-temperature piezoelectric ceramic system is not lower than 238 pC / N and can reach a maximum of 584 pC / N; at 200℃, the piezoelectric coefficient of this high-temperature piezoelectric ceramic system is not lower than 320 pC / N and can reach a maximum of 578 pC / N; and at 300℃, the piezoelectric coefficient of this high-temperature piezoelectric ceramic system is not lower than 320 pC / N and can reach a maximum of 457 pC / N.

[0025] This invention provides a method for preparing high-temperature piezoelectric ceramic materials, which can successfully prepare a single perovskite phase, avoiding the pyrochlore structure easily generated by other sintering methods. Furthermore, the ceramics prepared by this method have uniform particle size and high density. The preparation method of this invention is simple, has a low sintering temperature, low cost, and is suitable for large-scale industrial production, showing broad application prospects in the field of high-temperature piezoelectric devices. Because the tolerance factor of PYN-PT-based materials is close to the critical value, the perovskite structure is unstable. Previous simple sintering methods easily caused problems such as the formation of a second phase and low density in PYN-PT-based ceramics, thus affecting the electrical properties of the ceramics. The multi-stage sintering and annealing method provided by this invention first rapidly activates the ceramic powder at a high temperature to improve its reactivity; then, it is sintered at a lower temperature to avoid excessive grain growth, promote ceramic densification, and reduce lead volatilization. During the high-temperature sintering process, excess PbO can promote liquid-phase sintering of the ceramic, which is beneficial to ceramic densification and can also compensate for its volatilization losses. However, PbO segregated at the grain boundaries after sintering can affect various properties of the ceramic. Therefore, annealing is performed to eliminate excess PbO and avoid its adverse effects on the electrical properties of the ceramic. This invention achieves stable sintering of PYN-PT based materials by rationally setting the sintering temperature and time at each stage, avoiding the sintering process window where a second phase appears in the ceramic.

[0026] This invention provides an application of high-temperature piezoelectric ceramic material, which, due to its high Curie temperature and excellent piezoelectric properties, can ensure that piezoelectric devices can operate normally within a wide temperature range. Piezoelectric devices made of high-temperature piezoelectric ceramic material can operate stably at 300°C. Attached Figure Description

[0027] Figure 1 XRD diffraction patterns of samarium oxide-doped lead ytterbate-lead titanate piezoelectric ceramic samples prepared in comparative examples and Examples 1-4;

[0028] Figure 2 Scanning electron microscope (SEM) images of the samarium oxide-doped lead ytterbium niobate-lead titanate piezoelectric ceramic samples prepared in Examples 1-4;

[0029] Figure 3 Hysteresis curves of samarium oxide-doped lead ytterbate-lead titanate piezoelectric ceramic samples prepared in comparative examples and Examples 1-4 at 1 Hz at room temperature.

[0030] Figure 4 This is a graph showing the Curie temperature variations of different components in the samarium oxide-doped lead ytterbate-lead titanate piezoelectric ceramic sample of the present invention.

[0031] Figure 5 The temperature-dependent piezoelectric coefficient test curves of the samarium oxide-doped lead ytterbate-lead titanate piezoelectric ceramic samples prepared in comparative examples and Examples 1-4 are shown.

[0032] Figure 6 The graph shows the piezoelectric coefficient and planar electromechanical coupling coefficient of the samarium oxide-doped lead ytterbate-lead titanate piezoelectric ceramic sample prepared in Example 1 as a function of annealing temperature. Detailed Implementation

[0033] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0034] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0035] The present invention will now be described in further detail with reference to the accompanying drawings:

[0036] To address the problems of existing technologies, the present invention aims to overcome the shortcomings of existing technologies and provide a samarium oxide-doped PYN-PT-based high-temperature piezoelectric ceramic material with an operating temperature exceeding 300℃ and possessing both high Curie temperature and high piezoelectric performance, along with its preparation method. This invention balances the relationship between Curie temperature and piezoelectric performance, developing a novel high-temperature piezoelectric ceramic. Through rare earth element doping modification and material composition design, and via a multi-stage sintering and annealing process, a novel high-temperature piezoelectric ceramic material with high Curie temperature and high piezoelectric constant is prepared. The samarium oxide-doped PYN-PT-based high-temperature piezoelectric ceramic of this invention meets the higher requirements for piezoelectric materials in devices operating at high temperatures. Compared with commercial lead zirconate titanate piezoelectric materials, it exhibits significant advantages in Curie temperature and piezoelectric coefficient, and the preparation process is simple, low-cost, and has good reproducibility.

[0037] To address the issue that existing piezoelectric ceramics cannot simultaneously meet specific performance requirements in terms of Curie temperature and overall electrical properties, a synergistic strategy of rare earth element doping and altering the PT solid solution ratio is employed to enhance performance tunability. Sm₂O₃ doping is used to regulate the ceramic microstructure, creating a locally non-uniform structure and enhancing its piezoelectric properties. Utilizing the tetragonal crystal structure of PT, the quasi-isomorphic phase boundary of the piezoelectric ceramic is controlled by altering the PT solid solution ratio, resulting in a wider range of trigonal and tetragonal phase coexistence regions. This synergistic strategy effectively improves the piezoelectric properties of lead-based perovskite piezoelectric ceramics while maintaining a high Curie temperature, and simultaneously optimizes their ferroelectricity and increases strain, providing a new approach for the application of lead-based perovskite materials in high-temperature piezoelectric devices. Specifically, the chemical composition of the high-performance high-temperature piezoelectric ceramic material used in this invention, with a temperature exceeding 300℃, conforms to the general chemical formula: (1-x)Pb(Yb 0.5 Nb 0.5 O3-xPbTiO3–ymol%Sm2O3, wherein x = 0.45–0.52, y = 0.05–2. Preferably, x = 0.45, 0.48, 0.50 or 0.52, y = 0.25, 0.5, 0.75, or 1.

[0038] This invention employs the above-mentioned composition and regulates the quasi-isomorphic phase boundary to improve the piezoelectric coefficient of the high-temperature piezoelectric ceramic while ensuring a high Curie temperature (316–380°C). This meets the requirements of high-temperature piezoelectric ceramic components for high-temperature piezoelectric ceramic materials, strongly promoting the application of high-temperature piezoelectric ceramic materials in high-temperature fields. It is expected to be used in high-temperature piezoelectric devices operating at 200–300°C. In some examples, the room temperature piezoelectric coefficient of the high-temperature piezoelectric ceramic is 238–584 pC / N (preferably 474–584 pC / N), the piezoelectric coefficient at 200°C is 320–578 pC / N (preferably 447–578 pC / N), and the piezoelectric coefficient at 300°C is 320–457 pC / N (preferably 340–457 pC / N).33 * = 305~613pm / V@25℃ (preferably 495~613pm / V), Curie temperature 316~380℃, strain 0.18~0.27%, remanent polarization 27.5~39.6μC / cm 2 The depolarization temperature is 345–380℃. This is similar to that of undoped PYN-50PT(T C =367℃, T d =350℃, d 33 =394pC / N@25℃, d 33 =286pC / N@200℃, d 33 =242pC / N@300℃, d 33 * = 334 pm / V @ 25℃, strain is 0.18%, P r =19.5μC / cm 2 Compared to [other materials], the overall performance of the material is significantly improved.

[0039] This invention also provides a method for preparing high-performance high-temperature piezoelectric ceramic materials with a working temperature exceeding 300℃. First, a YbNbO4 precursor is synthesized, followed by the synthesis of samarium oxide-doped Pb(YbO4)2O3. 0.5 Nb 0.5 Lead ytterbate-lead titanate (PbTiO3) solid solution ceramic powder was sintered using a multi-stage sintering and annealing method to prepare high-voltage piezoelectric ceramic materials with lead ytterbate-lead titanate (PTiO3) properties. The specific steps included are as follows:

[0040] (1) Preparation of YbNbO4 precursor: Yb2O3 powder and Nb2O5 powder were mixed at a molar ratio of 1:1. The material, zircon and anhydrous ethanol were mixed at a mass ratio of 1:2:(0.5~1.0) and ball-milled for 12~18h. Then, the mixture was dried, ground and briquetted in sequence, and then kept at 1100~1200℃ for 4~6h to obtain YbNbO4 precursor.

[0041] (2)(1-x)Pb(Yb 0.5 Nb 0.5Preparation of PbO3-xPbTiO3-ymol%Sm2O3 piezoelectric ceramic material: PbO powder, TiO2 powder, Sm2O3 powder and YbNbO4 powder obtained in step (1) are used as raw materials and weighed according to the molar ratio of (1.02~1.06):x:0.01*y:0.5(1-x). Then, the whole batch, zircon and anhydrous ethanol are mixed in the mass ratio of 1:2:(0.5~1.0) and ball-milled for 12~18h. Then, the powder is dried, ground and pressed into blocks in sequence, and then kept at 800~900℃ for 2~4h to obtain pre-fired powder, in which x=0.45~0.52, y=0.05~2, and PbO excess is 2~6mol%.

[0042] (3) After crushing the pre-fired powder obtained in step (2), mix the material, zircon and anhydrous ethanol in a mass ratio of 1:2:(0.5~1.0) and then ball mill for 12~18h. After drying, grind and pass through a 120-mesh sieve. Add 6~10% of polyvinyl alcohol aqueous solution (PVA) to granulate. The mass concentration of PVA is 2~5%. After granulation, pass through 40-mesh and 80-mesh sieves to obtain uniform powder. After standing for 12~24h, press the uniform powder into shape under a pressure of 10~15MPa. Place it in a muffle furnace and heat it to 500~600℃ at 3~5℃ / min and hold for 1~3h to remove the binder and obtain ceramic blank for later use.

[0043] (4) The green body processed in step (3) is embedded in a 15mL independent crucible containing powder with the same composition as the green body and sintered using a multi-stage sintering and annealing method: In the first stage, the furnace temperature is raised to 1050-1100℃, and then the furnace is rapidly cooled to 900-1000℃; in the second stage, the furnace is held at 900-1000℃ for 2-4 hours and then naturally cooled to room temperature; in the third stage, the furnace is annealed at 800-900℃ for 1-2 hours with a heating rate of 10℃ / min and then naturally cooled to room temperature to obtain a high-performance high-temperature piezoelectric ceramic material with a service temperature of over 300℃.

[0044] (5) Polish the sintered ceramic sheet with sandpaper of different grits to obtain a thin ceramic sheet with a bright and smooth surface. Coat the front and back sides of the sample with silver electrode paste evenly and heat it at 500-600℃ for 10-30 minutes to obtain a high Curie temperature high voltage coefficient ceramic material.

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, only a few preferred embodiments are selected below and described in further detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0046] Example 1:

[0047] The chemical composition of piezoelectric ceramics is Pb(Yb) 0.5 Nb 0.5 The preparation method of O3–0.5PbTiO3–0.5mol%Sm2O3 includes the following steps:

[0048] (1) PbO powder, TiO2 powder, YbNbO4 powder and Sm2O3 powder were weighed in a molar ratio of 1.05:0.5:0.5:0.005. Then, the whole batch, zircon and anhydrous ethanol were mixed in a mass ratio of 1:2:0.6 and ball-milled for 15 hours. Then, the powder was dried, sieved and briquetteed in sequence, and then kept at 850℃ for 4 hours to obtain pre-calcined powder.

[0049] (2) After crushing the pre-fired powder obtained in step (1), mix the material, zircon and anhydrous ethanol in a mass ratio of 1:2:0.6 and then ball mill for 15 hours. After drying, grind and pass through a 120-mesh sieve. Add 8% polyvinyl alcohol aqueous solution (PVA) to granulate the powder. The mass concentration of PVA is 5%. After granulation, pass through 40-mesh and 80-mesh sieves to obtain uniform powder. After standing for 14 hours, press the uniform powder into shape under a pressure of 15 MPa. Place it in a muffle furnace and heat it to 600℃ at 5℃ / min and keep it at 600℃ for 1 hour to remove the binder and obtain a ceramic body for later use.

[0050] (3) The green body treated in step (2) was embedded in a 15 mL independent alumina crucible containing powder with the same composition as the green body, and sintered using a multi-stage sintering and annealing method: the first stage was to heat the furnace to 1050℃ at 5℃ / min, and then rapidly cool the furnace to 1000℃; the second stage was to hold the furnace at 1000℃ for 2 hours, and then allow it to cool naturally to room temperature; the third stage was to heat the furnace to 900℃ at 10℃ / min and hold it for 2 hours for annealing, and then allow it to cool naturally to room temperature; after sintering, Pb(Yb) was obtained. 0.5 Nb 0.5 High Curie temperature piezoelectric ceramic materials: O3–0.5PbTiO3–0.5mol%Sm2O3;

[0051] (4) The sintered ceramic sheet was polished with sandpaper of different grits to obtain a thin ceramic sheet with a bright and smooth surface. Silver electrode paste was uniformly coated on both sides of the sample, and the sample was fired at 500℃ for 10 min to obtain a ceramic element. The electrical properties of the obtained piezoelectric ceramic element were measured.

[0052] Example 2:

[0053] The chemical composition of piezoelectric ceramics is Pb(Yb) 0.5 Nb 0.5The preparation method of O3–0.5PbTiO3–1mol%Sm2O3 includes the following steps:

[0054] (1) PbO powder, TiO2 powder, YbNbO4 powder and Sm2O3 powder were weighed in a molar ratio of 1.05:0.5:0.5:0.01. Then, the whole batch, zircon and anhydrous ethanol were mixed in a mass ratio of 1:2:0.6 and ball-milled for 15 hours. Then, the powder was dried, sieved and briquetteed. Finally, it was kept at 850℃ for 4 hours to obtain pre-calcined powder.

[0055] (2) After crushing the pre-fired powder obtained in step (1), mix the material, zircon and anhydrous ethanol in a mass ratio of 1:2:0.6 and then ball mill for 15 hours. After drying, grind and pass through a 120-mesh sieve. Add 8% polyvinyl alcohol aqueous solution (PVA) to granulate the powder. The mass concentration of PVA is 5%. After granulation, pass through 40-mesh and 80-mesh sieves to obtain uniform powder. After standing for 14 hours, press the uniform powder into shape under a pressure of 15 MPa. Place it in a muffle furnace and heat it to 600℃ at 5℃ / min and keep it at 600℃ for 1 hour to remove the binder and obtain a ceramic body for later use.

[0056] (3) The green body treated in step (2) was embedded in a 15 mL independent alumina crucible containing powder with the same composition as the green body, and sintered using a multi-stage sintering and annealing method: the first stage was to heat the furnace to 1050℃ at 5℃ / min, and then rapidly cool the furnace to 1000℃; the second stage was to hold the furnace at 1000℃ for 2 hours, and then allow it to cool naturally to room temperature; the third stage was to heat the furnace to 900℃ at 10℃ / min and hold it for 2 hours for annealing, and then allow it to cool naturally to room temperature; after sintering, Pb(Yb) was obtained. 0.5 Nb 0.5 High Curie temperature piezoelectric ceramic material: O3–0.5PbTiO3–1mol%Sm2O3;

[0057] (4) The sintered ceramic sheet was polished with sandpaper of different grits to obtain a thin ceramic sheet with a bright and smooth surface. Silver electrode paste was uniformly coated on both sides of the sample, and the sample was fired at 500℃ for 10 min to obtain a ceramic element. The electrical properties of the obtained piezoelectric ceramic element were measured.

[0058] Example 3:

[0059] The chemical composition of piezoelectric ceramics is Pb(Yb) 0.5 Nb 0.5 The preparation method of O3–0.48PbTiO3–0.5mol%Sm2O3 includes the following steps:

[0060] (1) PbO powder, TiO2 powder, YbNbO4 powder and Sm2O3 powder were weighed in a molar ratio of 1.05:0.48:0.52:0.005. Then, the whole batch, zircon and anhydrous ethanol were mixed in a mass ratio of 1:2:0.6 and ball-milled for 15 hours. Then, the powder was dried, sieved and briquetteed. Finally, it was kept at 850℃ for 4 hours to obtain pre-calcined powder.

[0061] (2) After crushing the pre-fired powder obtained in step (1), mix the material, zircon and anhydrous ethanol in a mass ratio of 1:2:0.6 and then ball mill for 15 hours. After drying, grind and pass through a 120-mesh sieve. Add 8% polyvinyl alcohol aqueous solution (PVA) to granulate the powder. The mass concentration of PVA is 5%. After granulation, pass through 40-mesh and 80-mesh sieves to obtain uniform powder. After standing for 14 hours, press the uniform powder into shape under a pressure of 15 MPa. Place it in a muffle furnace and heat it to 600℃ at 5℃ / min and keep it at 600℃ for 1 hour to remove the binder and obtain a ceramic body for later use.

[0062] (3) The green body treated in step (2) was embedded in a 15 mL independent alumina crucible containing powder with the same composition as the green body, and sintered using a multi-stage sintering and annealing method: the first stage was to heat the furnace to 1050℃ at 5℃ / min, and then rapidly cool the furnace to 1000℃; the second stage was to hold the furnace at 1000℃ for 2 hours, and then allow it to cool naturally to room temperature; the third stage was to heat the furnace to 900℃ at 10℃ / min and hold it for 2 hours for annealing, and then allow it to cool naturally to room temperature; after sintering, Pb(Yb) was obtained. 0.5 Nb 0.5 High Curie temperature piezoelectric ceramic materials: O3–0.48PbTiO3–0.5mol%Sm2O3;

[0063] (4) The sintered ceramic sheet was polished with sandpaper of different grits to obtain a thin ceramic sheet with a bright and smooth surface. Silver electrode paste was uniformly coated on both sides of the sample, and the sample was fired at 500℃ for 10 min to obtain a ceramic element. The electrical properties of the obtained piezoelectric ceramic element were measured.

[0064] Example 4:

[0065] The chemical composition of piezoelectric ceramics is Pb(Yb) 0.5 Nb 0.5 The preparation method of O3–0.52PbTiO3–0.5mol%Sm2O3 includes the following steps:

[0066] (1) PbO powder, TiO2 powder, YbNbO4 powder and Sm2O3 powder were weighed in a molar ratio of 1.05:0.52:0.48:0.005. Then, the whole batch, zircon and anhydrous ethanol were mixed in a mass ratio of 1:2:0.6 and ball-milled for 15 hours. Then, the powder was dried, sieved and briquetteed in sequence, and then kept at 850℃ for 4 hours to obtain pre-calcined powder.

[0067] (2) After crushing the pre-fired powder obtained in step (1), mix the material, zircon and anhydrous ethanol in a mass ratio of 1:2:0.6 and then ball mill for 15 hours. After drying, grind and pass through a 120-mesh sieve. Add 8% polyvinyl alcohol aqueous solution (PVA) to granulate the powder. The mass concentration of PVA is 5%. After granulation, pass through 40-mesh and 80-mesh sieves to obtain uniform powder. After standing for 14 hours, press the uniform powder into shape under a pressure of 15 MPa. Place it in a muffle furnace and heat it to 600℃ at 5℃ / min and keep it at 600℃ for 1 hour to remove the binder and obtain a ceramic body for later use.

[0068] (3) The green body treated in step (2) was embedded in a 15 mL independent alumina crucible containing powder with the same composition as the green body, and sintered using a multi-stage sintering and annealing method: the first stage was to heat the furnace to 1050℃ at 5℃ / min, and then rapidly cool the furnace to 1000℃; the second stage was to hold the furnace at 1000℃ for 2 hours, and then allow it to cool naturally to room temperature; the third stage was to heat the furnace to 900℃ at 10℃ / min and hold it for 2 hours for annealing, and then allow it to cool naturally to room temperature; after sintering, Pb(Yb) was obtained. 0.5 Nb 0.5 High Curie temperature piezoelectric ceramic materials: O3–0.52PbTiO3–0.5mol%Sm2O3;

[0069] (4) The sintered ceramic sheet was polished with sandpaper of different grits to obtain a thin ceramic sheet with a bright and smooth surface. Silver electrode paste was uniformly coated on both sides of the sample, and the sample was fired at 500℃ for 10 min to obtain a ceramic element. The electrical properties of the obtained piezoelectric ceramic element were measured.

[0070] Comparative example:

[0071] The chemical composition of piezoelectric ceramics is Pb(Yb) 0.5 Nb 0.5 The process of obtaining O3-0.5PbTiO3 includes the following steps:

[0072] (1) PbO powder, TiO2 powder and YbNbO4 powder were weighed in a molar ratio of 1.05:0.5:0.5. Then, the whole batch, zircon and anhydrous ethanol were mixed in a mass ratio of 1:2:0.6 and ball-milled for 15 hours. Then, the mixture was dried, sieved and briquetteed. Finally, it was kept at 850℃ for 4 hours to obtain pre-calcined powder.

[0073] (2) After crushing the pre-fired powder obtained in step (1), mix the material, zircon and anhydrous ethanol in a mass ratio of 1:2:0.6 and then ball mill for 15 hours. After drying, grind and pass through a 120-mesh sieve. Add 8% polyvinyl alcohol aqueous solution (PVA) to granulate the powder. The mass concentration of PVA is 5%. After granulation, pass through 40-mesh and 80-mesh sieves to obtain uniform powder. After standing for 14 hours, press the uniform powder into shape under a pressure of 15 MPa. Place it in a muffle furnace and heat it to 600℃ at 5℃ / min and keep it at 600℃ for 1 hour to remove the binder and obtain a ceramic body for later use.

[0074] (3) Cover the ceramic blank treated in step (2) with powder of the same composition, place it in a 15mL independent alumina crucible, heat it to 1000℃ at 5℃ / min and hold it for 2h, then let it cool naturally to room temperature in the furnace; after sintering, Pb(Yb) is obtained. 0.5 Nb 0.5 O3-0.5PbTiO3 high Curie temperature piezoelectric ceramic material;

[0075] (4) The sintered ceramic sheet was polished with sandpaper of different grits to obtain a thin ceramic sheet with a bright and smooth surface. Silver electrode paste was uniformly coated on both sides of the sample, and the sample was fired at 500℃ for 10 min to obtain a ceramic element. The electrical properties of the obtained piezoelectric ceramic element were measured.

[0076] Figure 1 This is the X-ray diffraction (XRD) pattern of the samarium oxide-doped PYN-PT-based high-temperature piezoelectric ceramic of this invention. From... Figure 1 As can be seen, the piezoelectric ceramics prepared by the multi-stage sintering and annealing process all exhibit a single perovskite structure without a distinct second phase. For y mol% Sm₂O₃-doped (1-x)Pb(Yb) 0.5 Nb 0.5O3-xPbTiO3 (x = 0.45–0.52, y = 0.05–2) ceramics exhibit a high-temperature piezoelectric ceramic system that, with the same Sm content, transforms from a trigonal perovskite phase structure to a tetragonal perovskite phase structure with increasing PT content. When the PT content is 0.45 and 0.48, the system tends to transform from a trigonal to a tetragonal perovskite phase structure with increasing Sm content. When the PT content is 0.50 and 0.52, the system tends to transform from a tetragonal to a trigonal perovskite phase structure with increasing Sm content. When x = 0.48–0.52 and y = 0.05–2, the ceramic sample exhibits a perovskite structure with coexisting trigonal and tetragonal phases, displaying quasi-isomorphic phase boundary (MPB) characteristics. This MPB phase structure indicates its excellent piezoelectric properties.

[0077] Figure 2 These are scanning electron microscope (SEM) images of samarium oxide-doped PYN-PT-based high-temperature piezoelectric ceramics prepared in Examples 1-4 of this invention. Figure 2 It can be seen that the ceramic surface has almost no pores, clear grain boundaries, and uniform and dense grains. With the doping of samarium oxide, the ceramic grain size gradually decreases. Taking PYN-50PT as an example, after Sm2O3 doping, the average grain size decreased from 5.3 μm (0% Sm2O3) to 2.1 μm (1% Sm2O3); however, with the change of PT content, the grain size did not show a significant trend. This high-temperature piezoelectric ceramic system was prepared by a multi-stage sintering and annealing method. First, the grains were rapidly activated at a higher temperature; then, sintering was carried out at a lower temperature to avoid excessive grain growth, promote ceramic density, and avoid severe volatilization; annealing can further remove excess PbO and eliminate its adverse effects on the electrical properties of the ceramic. Therefore, the use of Sm2O3 doping and multi-stage sintering and annealing method effectively reduces the grain size and improves the density, which is beneficial to the further improvement of the piezoelectric properties of the ceramic material.

[0078] Figure 3 This is the hysteresis loop of the samarium oxide-doped PYN-PT-based high-temperature piezoelectric ceramic of this invention at 1 Hz under room temperature conditions. For y mol% Sm₂O₃-doped (1-x)Pb(Yb) 0.5 Nb 0.5 In SmO3-xPbTiO3 (x = 0.45–0.52, y = 0.05–2) ceramics, when the Sm content is the same, the coercive electric field of the high-temperature piezoelectric ceramic system increases and the remanent polarization decreases with the increase of PT content. When the PT content is constant, compared with the undoped PYN-PT ceramic, the coercive electric field of the Sm-doped ceramic increases slightly and the remanent polarization is greatly improved, which also indicates to some extent that Sm doping helps to improve the piezoelectric properties of the ceramic.

[0079] Figure 4 This is a Curie temperature variation graph for different components of the samarium oxide-doped PYN-PT-based high-temperature piezoelectric ceramic of the present invention. For y mol% Sm₂O₃-doped (1-x)Pb(Yb)₂… 0.5 Nb 0.5 For O3-xPbTiO3 (x = 0.45~0.52, y = 0.25~2) ceramics, when the Sm content is the same, the Curie temperature of this high-temperature piezoelectric ceramic system gradually increases with the increase of PT content; when the PT content is constant, the Curie temperature of this high-temperature piezoelectric ceramic system tends to gradually decrease with the increase of Sm content, but it still remains at a relatively high level compared with other perovskite piezoelectric ceramic materials.

[0080] Figure 5 This is a graph showing the temperature-dependent piezoelectric coefficient of the samarium oxide-doped PYN-PT-based high-temperature piezoelectric ceramic of this invention. Figure 5 It can be seen that the piezoelectric coefficient curves of Example 1 and the comparative example are similar in shape to those of the temperature variation curves. The piezoelectric coefficient gradually decreases with increasing temperature, and rapidly drops to 0 above 358℃. The piezoelectric coefficient of Example 2 first increases slowly with increasing temperature and then gradually decreases, exhibiting good temperature stability within 150℃, with a depolarization temperature of approximately 345℃. The piezoelectric coefficient of Example 3 fluctuates significantly with temperature, but it can reach over 700 pC / N near 160℃, with a depolarization temperature of approximately 350℃. The piezoelectric coefficient of Example 4 fluctuates very little with temperature, indicating strong temperature stability, with a depolarization temperature of approximately 380℃. At 200℃, the piezoelectric coefficient of the comparative example is 286 pC / N, and the piezoelectric coefficients of Examples 1-4 are 320–578 pC / N. At 300℃, the piezoelectric coefficient of the comparative example is 242 pC / N, and the piezoelectric coefficients of Examples 1-4 are 320–457 pC / N. Therefore, it can be seen that the depolarization temperature of the high-temperature piezoelectric ceramics of this invention is not lower than 345℃, and they maintain excellent piezoelectric performance at high temperatures. This is of great significance for the high-temperature application of high-sensitivity piezoelectric sensors.

[0081] Figure 6 The figures show the piezoelectric coefficient and planar electromechanical coupling coefficient of the samarium oxide-doped PYN-PT-based high-temperature piezoelectric ceramic prepared in Example 1 of this invention, as a function of annealing temperature. Figure 6 It can be seen that the piezoelectric coefficient and electromechanical coupling coefficient of the ceramic sample gradually decrease with increasing annealing temperature, and decrease rapidly when the annealing temperature exceeds 350℃. Notably, the ceramic sample maintains a high piezoelectric coefficient and electromechanical coupling coefficient even below 200℃ and 300℃, which is beneficial for the application of this piezoelectric ceramic system in higher temperature environments.

[0082] The main performance parameters of the high-temperature piezoelectric ceramic samples prepared in comparative examples and Examples 1-4 at room temperature are shown in Table 1.

[0083] Table 1. Main properties of the high-temperature piezoelectric ceramic samples prepared in comparative examples and Examples 1-4 at room temperature.

[0084]

[0085] The main performance parameters of the high-temperature piezoelectric ceramic samples prepared in comparative examples and Examples 1-4 at high temperatures are shown in Table 2.

[0086] Table 2 shows the main properties of the high-temperature piezoelectric ceramic samples prepared in comparative examples and Examples 1-4 at high temperatures.

[0087]

[0088]

[0089] The piezoelectric coefficients of the high-temperature piezoelectric ceramic samples prepared in comparative examples and Examples 1-4 at different temperatures are shown in Table 3.

[0090] Table 3 shows the piezoelectric coefficients of the high-temperature piezoelectric ceramic samples prepared in comparative examples and Examples 1-4 at different temperatures.

[0091]

[0092] As shown in Table 1 above, the Curie temperature of the high-temperature piezoelectric ceramic material samples prepared in this invention is 343–380℃, the piezoelectric coefficient at room temperature can reach 328–584 pC / N, the inverse piezoelectric coefficient can reach 394–613 pC / V, the dielectric loss is 0.017–0.025, and the planar electromechanical coupling coefficient k... p The relative permittivity can reach 0.33–0.60, the relative permittivity can reach 949–2113, the strain can reach 0.20%–0.25%, and the mechanical quality factor Q m The values ​​range from 39 to 56, and the depolarization temperature ranges from 345 to 380℃.

[0093] As shown in Table 2 above, the high-temperature piezoelectric ceramic material prepared in this invention has a piezoelectric coefficient of 320-578 pC / N at 200℃, a piezoelectric coefficient of 320-457 pC / N at 300℃, an inverse piezoelectric coefficient of 394-757 pm / V at 200℃, and a strain coefficient of 0.24%-0.30% at 200℃.

[0094] As shown in Table 3 above, the high-temperature piezoelectric ceramic material prepared in this invention maintains a high piezoelectric coefficient across all temperature ranges below 300℃. Specifically, below 100℃, the piezoelectric coefficient of Example 1 exceeds 560 pC / N; within the temperature range of 100℃ to 300℃, the piezoelectric coefficient of Example 2 exceeds 457 pC / N, reaching a maximum of 661 pC / N at 150℃; and across the entire temperature range, the piezoelectric coefficient variation of Example 4 is within 5%, exhibiting strong temperature stability. Therefore, the high-temperature piezoelectric ceramic system prepared in this invention demonstrates strong application potential in various temperature environments.

[0095] The embodiments given above are merely preferred embodiments of the present invention, which can provide a clearer understanding of the content and specific methods of the present invention. However, they are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the principles of the present invention should be included within the protection scope of the present invention.

[0096] Industrial applicability: The high-temperature piezoelectric ceramic material prepared by this invention can be used to prepare devices such as high-temperature piezoelectric sensors and high-temperature piezoelectric transducers, and has good application prospects.

[0097] This invention belongs to the field of high-temperature piezoelectric ceramic materials, specifically relating to a high-performance high-temperature piezoelectric ceramic material with an operating temperature exceeding 300℃. The general chemical formula of this piezoelectric ceramic material is (1-x)Pb(Yb). 0.5 Nb 0.5 The ceramic material is prepared by solid-state sintering using a multi-stage sintering-annealing method. X-ray powder diffraction confirmed that the system has a single perovskite structure. While maintaining a high Curie temperature, the piezoelectric ceramic material exhibits excellent piezoelectric properties, with a maximum piezoelectric coefficient of 584 pC / N at room temperature, 578 pC / N at 200℃, and 457 pC / N at 300℃. This meets the requirements for piezoelectric functional materials in high-temperature piezoelectric devices. The preparation process is simple, low-cost, and suitable for large-scale industrial production, showing broad application prospects in high-temperature piezoelectric sensors and transducers.

[0098] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing a high-temperature piezoelectric ceramic material, characterized in that, Includes the following steps: (1) According to (1-x)Pb(Yb) 0.5 Nb 0.5 The stoichiometric ratio of YbNbO4, PbO, TiO2, and Sm2O3 was determined by weighing YbNbO4, PbO, TiO2, and Sm2O3, mixing the raw materials, and then ball-milling them once. After drying, a mixed powder was obtained. The values ​​of x and y were 0.45–0.52, and the amount of PbO added was 2%–6% excess of its own stoichiometric ratio. (2) The mixed powder is pre-fired at 800-900℃ for more than 2 hours. After pre-firing, it is cooled to room temperature to obtain ceramic powder. Then, it is subjected to secondary ball milling, drying, grinding, granulation and sieving to obtain powder with uniform particles. (3) The uniformly sized powder is pressed into a green body; the green body is then placed in a crucible containing the ceramic powder and kept at 500-600℃ to remove organic matter; subsequently, a multi-stage sintering annealing method is used for sintering. The temperature is raised from room temperature to 1050-1100℃ at a rate of 3-5℃ / min, then cooled in the furnace to 900-1000℃, held at 900-1000℃ for 2-4 hours, and then allowed to cool naturally to room temperature. The temperature is increased to 800~900℃ at a heating rate of 8-10℃ / min, and annealed by holding at 800~900℃ for 1~2 hours. The material is then naturally cooled to room temperature in the furnace to obtain a high-temperature piezoelectric ceramic material. The process of silver polarization is as follows: polish the high-temperature piezoelectric ceramic material, coat the surface with silver paste, sinter the silver paste and then cool it naturally to room temperature; then place the silver paste-coated ceramic in silicone oil and apply a DC electric field to polarize it. The piezoelectric coefficient of high-voltage ceramics is 238~584 pC / N at room temperature, 320~578 pC / N at 200℃, and 320~457 pC / N at 300℃. 33 *=305~613pm / V@25℃, Curie temperature is 316~380℃, strain is 0.18~0.27%, remanent polarization is 27.5~39.6μC / cm 2 The depolarization temperature is 345~380℃.

2. A high-temperature piezoelectric ceramic material prepared by the method described in claim 1, characterized in that: The general chemical formula is (1-x)Pb(Yb) 0.5 Nb 0.5 O3-xPbTiO3–ymol%Sm2O3 belongs to the perovskite type structure, where 0.45≤x≤0.52 and 0.05≤y≤2.

3. The high-temperature piezoelectric ceramic material according to claim 2, characterized in that, When x = 0.48~0.52 and y = 0.05~2, it has a quasi-isomorphic phase boundary.

4. The high-temperature piezoelectric ceramic material according to claim 2, characterized in that, Small signal piezoelectric coefficient d 33 =238~584pC / N@25℃, d 33 =320~578pC / N@200℃、d 33 =320~457pC / N@300℃; Large-signal piezoelectric coefficient d 33 *=305~613pm / V@25℃, d 33 *=394~757pm / V@200℃; Curie temperature is T c =316~380℃; Electrostriction S = 0.18~0.27%@25℃, S = 0.24~0.30%@200℃.

5. The application of the high-temperature piezoelectric ceramic material according to claim 2, 3 or 4, characterized in that, The applicable temperature range for piezoelectric devices is room temperature to 300℃.

Images