La2Be2O5 composite material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of piezoelectric ceramics, and particularly relates to a La2Be2O5 composite material as well as a preparation method and application thereof. The method comprises the following steps: step 1, adding nano beta-SiC powder into a mixed solution of ethanol and water to prepare a SiC suspension; 2, lanthanum isopropoxide and beryllium tert-butoxide are dissolved in ethyl alcohol, acetylacetone and citric acid are added, precursor complex sol is formed, and the SiC suspension in the step 1 is added into the precursor complex sol; step 3, dropwise adding deionized water into the solution obtained in the step 2, and reacting to obtain gel; 4, replacing the gel with liquid CO2, and drying under a supercritical condition to obtain composite dry gel; and 5, pouring the mixed slurry into a mold to prepare a ceramic green body, and calcining to prepare the La2Be2O5 composite ceramic. By optimizing the microstructure and performance of the composite material, the problems that a traditional piezoelectric material is insufficient in toughness, insufficient in sensitivity in high-frequency vibration detection, limited in frequency response range and the like are solved, and therefore the detection precision and reliability are improved.

Description

Technical Field

[0001] This invention belongs to the field of piezoelectric ceramic technology, specifically a La2Be2O5 composite material, its preparation method and application. Background Technology

[0002] With the rapid development of technology, the demand for high-frequency vibration detection technology is increasing in fields such as aerospace, automotive, and precision machinery. The core of high-frequency vibration detection technology lies in accurately capturing and analyzing high-frequency vibration signals, which is of great significance for equipment condition monitoring, fault diagnosis, and performance optimization. However, in practical applications, traditional piezoelectric materials (such as quartz and lead zirconate titanate PZT), despite their excellent piezoelectric properties, still face many limitations in high-frequency vibration detection.

[0003] The limitations of traditional piezoelectric materials are mainly reflected in the following aspects: First, materials such as quartz and PZT have low sensitivity in high-frequency response, making it difficult for them to accurately capture minute changes in high-frequency vibration signals. Second, the frequency response range of these materials is relatively narrow, which cannot meet the needs of wide-band vibration detection under complex working conditions. In addition, traditional piezoelectric materials have poor durability and are prone to performance degradation due to environmental factors (such as temperature and humidity) or mechanical stress during long-term use.

[0004] In recent years, researchers have begun to explore novel piezoelectric materials to overcome the aforementioned problems. La₂Be₂O₅, as a novel oxide ceramic material, has attracted much attention due to its unique crystal structure and excellent physicochemical properties. This material possesses a high dielectric constant and good mechanical stability, making it a potential candidate for applications in high-frequency vibration detection.

[0005] From a material properties perspective, the crystal structure of La₂Be₂O₅ exhibits high symmetry, providing a solid foundation for the piezoelectric effect. Studies have shown that this material possesses excellent chemical and thermal stability, maintaining stable performance even under extreme conditions. Furthermore, the high dielectric constant of La₂Be₂O₅ contributes to enhanced sensitivity in high-frequency vibration detection.

[0006] However, pure La2Be2O5 materials still face several unresolved issues in practical applications. First, its low piezoelectric coefficient limits its sensitivity in high-frequency vibration detection. Second, La2Be2O5 lacks sufficient toughness, making it difficult to meet the requirements for long-term stable use under complex conditions. Furthermore, its frequency response range remains limited, failing to fully cover the wide-band requirements of high-frequency vibration signals. Specifically, its thickness electromechanical coupling coefficient (k...) tIts efficiency is typically below 28%, and its usable high-frequency detection range (-3dB bandwidth) is mostly limited to below 15 MHz, which severely restricts its application in ultra-high frequency detection equipment.

[0007] In summary, although La2Be2O5, as a novel oxide ceramic material, shows promising application prospects in the field of high-frequency vibration detection, its performance still has considerable room for improvement. By optimizing the material preparation process and designing novel composite materials, it is hoped that its piezoelectric coefficient, toughness, and frequency response range can be further improved, thereby meeting the practical needs of high-frequency vibration detection. Summary of the Invention

[0008] To address the aforementioned problems, this invention aims to provide a La2Be2O5 composite material and its preparation method, and to apply it to the field of high-frequency vibration detection. By optimizing the microstructure and properties of the composite material, the invention solves the problems of insufficient toughness, insufficient sensitivity, and limited frequency response range of traditional piezoelectric materials in high-frequency vibration detection, thereby improving detection accuracy and reliability.

[0009] On one hand, the present invention provides a La2Be2O5 composite material and its preparation method, comprising the following steps: Step 1: Add nano-β-SiC powder to a mixture of ethanol and water to prepare a SiC suspension; Step 2: Dissolve lanthanum isopropoxide and beryllium tert-butoxide in ethanol, add acetylacetone and citric acid to form a precursor complex sol, and add the SiC suspension from Step 1 to the precursor complex sol. Step 3: Add deionized water dropwise to the solution obtained in Step 2 to adjust the pH to 3.5-5.0, and react at 60-80℃ for 6-10 hours to obtain a gel; Step 4: The gel is subjected to 8-12 cycles of liquid CO2 replacement and dried under supercritical conditions to obtain a composite dry gel; Step 5: The mixed slurry is molded and calcined at 1400-1600℃ to obtain La2Be2O5 composite ceramic, wherein the composite ceramic contains 20-40 vol% SiC.

[0010] In a further improvement to this scheme, in step 1, the average particle size of the nano-β-SiC powder is 80 nm, and the etched SiC powder is added to an ethanol / water mixture, wherein the volume fraction of the nano-β-SiC powder is 30 vol.

[0011] More preferably, in step 1, the average particle size of the nano β-SiC powder is 80 nm. The surface SiO2 layer is removed by acid etching. The etched SiC powder (30 vol%) is added to an ethanol / water mixture (V:V=4:1) and ultrasonically treated. Ammonia is added dropwise to adjust the pH to 9.0, and the mixture is refluxed at 80°C for 6 h.

[0012] A further improvement to this scheme is that in step 2, lanthanum isopropoxide and beryllium tert-butoxide are reacted with La... 3+ With Be 2+ Soluble in ethanol at a molar ratio of 1:1 with acetylacetone and Be 2+ The molar ratio is 1.0:1 - 1.5:1, and the molar ratio of citric acid to total metal ions is 1.0:1 - 2.0:1.

[0013] In a further improvement to this scheme, in step 2, the mixture is stirred at 60°C to form a transparent complex sol precursor, and the SiC suspension is added to the precursor sol at a droplet acceleration rate of 1 mL / min.

[0014] In a further improvement to this scheme, in step 3, the ratio of deionized water to alkoxide is 1.8:1, the pH is adjusted to 4.0±0.2, and the reaction conditions are 65℃ for 8 h.

[0015] In a further improvement to this scheme, in step 4, the supercritical drying conditions are: temperature 40-50℃, pressure 10-15 MPa, time 2-4 hours. Preferably, the wet gel is replaced by liquid CO2 for 10 cycles, and the supercritical conditions are 45℃, 12MPa, and 3 hours to obtain a composite dry gel with a porosity of <5%.

[0016] A further improvement to this scheme is that in step 5, a ceramic blank with a thickness of 0.5 mm is prepared by tape casting or slip casting, and the sintering temperature is 1500-1550℃, with a holding time of 4-6 minutes.

[0017] A more preferred method for preparing La2Be2O5 composite materials includes the following steps: 1. Hydroxylation and dispersion on SiC surface Nano-β-SiC powder (average particle size 80 nm) was etched with HF acid to remove the surface SiO2 layer. The etched SiC powder (30 vol%) was added to an ethanol / water mixture (volume ratio = 4:1) and ultrasonically treated for 2 h (power 800 W). Ammonia was added dropwise to adjust the pH to 9.0, and the mixture was refluxed at 80 °C for 6 h to obtain a SiC suspension rich in -OH groups (Zeta potential = -35 mV). 2. Preparation of precursors for in-situ sol-coating Beryllium-lanthanum alkoxide mixture: Lanthanum isopropoxide (La(OC3H7)3) and beryllium tert-butoxide (Be(OC4H9)2) were dissolved in ethanol at a molar ratio of La:Be = 1:1, and acetylacetone (acetylacetone:Be) was added. 2+A molar ratio of 1.2:1 is used to inhibit hydrolysis; the initial experimental conditions are usually set at approximately 15 ml of ethanol per gram of total raw material. The amount of ethanol is adjusted appropriately according to the properties of the solution (such as viscosity and clarity) during the actual preparation process. Here, a total mass ratio of organometallic compounds to ethanol volume of 1 g : 20 ml to 1 g : 30 ml is sufficient for dissolution, preferably 1 g : 25 ml.

[0018] Complexation stabilization: Add citric acid (CA) (CA:total metal ion molar ratio = 1.5:1), stir at 60℃ to form a transparent precursor complex sol (viscosity ≈ 25 mPa·s); total metal ions refer to La 3+ With Be 2+ The sum of the molar ratios of La and Be is 1:1, therefore the amount of each metal cation is 0.5 mol (if the total is 1 mol).

[0019] Gradient wrapping: The SiC suspension was added dropwise to the precursor complex sol, with the dropping rate controlled at 1 mL / min, and simultaneous ultrasonic oscillation (40 kHz). The core of adding the SiC suspension dropwise is to achieve uniform coating of nanoparticles. The volume ratio of the SiC suspension to the precursor complex sol is 1:3.5 to 1:4, preferably 1:4.

[0020] 3: Hydrolysis-gelation control Deionized water was added dropwise (H2O:alkoxide = 1.8:1 molar ratio) ("alkoxide" refers to the total molar number of lanthanum isopropoxide and beryllium tert-butoxide; pH was adjusted to 4.0 ± 0.2 with acetic acid; the mixture was stirred at 65°C for 8 h to obtain a blue-gray wet gel (SiC surface coating thickness ≈ 15 nm).

[0021] 4: Supercritical fluid drying The wet gel was replaced with liquid CO2 (10 cycles) under supercritical conditions: 45℃, 12 MPa, 3 h, to obtain a composite dry gel with a porosity of <5%. 5: Spark Plasma Sintering (SPS) The mixed slurry obtained in step 4 was poured into a mold, and a ceramic green body with a thickness of 0.5 mm was prepared by tape casting. The green body was then calcined at 1550℃ under an Ar atmosphere for 4-6 minutes to obtain La2Be2O5 / 30vol%SiC composite ceramic.

[0022] On the other hand, the present invention provides a La2Be2O5 composite material obtained by the above preparation method.

[0023] Furthermore, this invention provides the application of the La2Be2O5 composite material obtained by the above method in high-frequency vibration detection.

[0024] As can be seen from the above technical solutions, the beneficial effects of the present invention are: The beneficial effects of this invention are: by preparing composite ceramics using La2Be2O5 / 30vol%SiC, the overall performance and fracture toughness (K) are significantly improved. IC Up to 6.2 MPa·m 1 / 2 (244% higher than the solid-state method), while optimizing thermal conductivity (65.3 W / m·K) and electromechanical coupling efficiency (kJ / m·K). p =0.31), the material of this invention exhibits a wider high-frequency response range (-3dB bandwidth up to 5.8 MHz) and a higher thickness electromechanical coupling coefficient (k t (>34%), giving it a clear application advantage in the field of high-frequency and ultra-high-frequency vibration sensors and transducers. Detailed Implementation

[0025] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the embodiments described below are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this patent, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this patent.

[0026] All raw materials used in the examples are commercially available, with nano-β-SiC purchased from Alfa Aesar.

[0027] Example 1: Preparation method of La2Be2O5 / 30vol%SiC composite ceramic A La2Be2O5 precursor layer was constructed on the surface of SiC nanoparticles using an in-situ coating sol-gel method, achieving molecular-level interfacial bonding and suppressing high-temperature phase separation.

[0028] 1. Hydroxylation and dispersion on SiC surface Nano-β-SiC powder (average particle size 80 nm) was etched with HF acid to remove the surface SiO2 layer. The etched SiC powder (30 vol%) was added to an ethanol / water mixture (volume ratio 4:1) and ultrasonically dispersed for 2 h (power 800 W). Ammonia was added dropwise to adjust the pH to 9.0, and the mixture was refluxed at 80 °C for 6 h to obtain a SiC suspension rich in -OH groups (Zeta potential = -35 mV). 2. Preparation of precursors for in-situ sol-coating Lanthanum isopropoxide (La(OC3H7)3) and beryllium tert-butoxide (Be(OC4H9)2) were dissolved in ethanol at a molar ratio of La:Be = 1:1 (total mass of organometallic compounds to volume ratio of ethanol was 1 g : 25 ml), and acetylacetone (acetylacetone:Be) was added. 2+ Hydrolysis was inhibited by adding citric acid (CA:total metal ion molar ratio = 1.2:1); a transparent complex sol (viscosity ≈ 25 mPa·s) was formed by stirring at 60℃; the SiC suspension was added dropwise to the precursor sol (volume ratio of SiC suspension to precursor complex sol = 1:4) with a dropping rate of 1 mL / min and simultaneous ultrasonic oscillation (40 kHz); deionized water (H2O:alkoxide = 1.8:1 molar ratio) was added dropwise, and the pH was adjusted to 4.0 ± 0.2 with acetic acid; the mixture was stirred at 65℃ for 8 h to obtain a blue-gray gel (SiC surface coating thickness ≈ 15 nm). 3. Supercritical fluid drying The wet gel was replaced with liquid CO2 10 times in sequence, and then dried under supercritical conditions (45℃ / 12 MPa) for 3 h to obtain a dry gel with a porosity of <5%. 4. Spark Plasma Sintering (SPS) The mixed slurry was poured into a mold, and a ceramic green body with a thickness of 0.5 mm was prepared by tape casting. Specifically, the dry gel obtained in step 3 was uniformly coated onto a moving substrate, and the coating speed was controlled at 0.5 to 2 m / min and the drying temperature at 60 to 80°C to obtain a wet-cured green body with uniform thickness and a smooth surface. Subsequently, the cut green body was sintered. Under an Ar atmosphere, the heating rate was 200°C / min, the sintering temperature was 1550°C, and the holding time was 4-6 minutes to obtain La2Be2O5 / 30vol%SiC composite ceramic.

[0029] Example 2: Verification of Parameter Range Endpoints and Intermediate Values To demonstrate the feasibility of the parameter range of this invention, we set different endpoint and intermediate values ​​for the key parameters in step 2 above for verification. All samples were processed using the same in-situ sol-gel method and SPS sintering process as in Example 1, with only the target parameters changed. The volume fraction of nano-β-SiC powder refers to the volume fraction of nano-β-SiC powder in the final La2Be2O5 composite ceramic. Different volume fractions of nano-β-SiC powder in the final La2Be2O5 composite ceramic were obtained by adjusting the SiC content of the raw materials, referring to the volume fraction in Example 1. The pH value and reaction temperature refer to the parameter adjustments in step 2 above: "adjusting pH to 4.0±0.2 with acetic acid; constant stirring at 65℃ for 8 h." The sintering temperature refers to the temperature adjustments in step 4 above: "under Ar atmosphere, heating rate 200℃ / min, sintering temperature 1550℃."

[0030] Sample A (lower end): SiC volume fraction 20 vol%, pH=3.5, reaction temperature 60℃, sintering temperature 1400℃.

[0031] Sample B (intermediate value): SiC volume fraction 30 vol%, pH=4.0, reaction temperature 70℃, sintering temperature 1500℃.

[0032] Sample C (high end): SiC volume fraction 40 vol%, pH=5.0, reaction temperature 80℃, sintering temperature 1600℃.

[0033] Table 1. Performance comparison of different samples within the parameter range Performance parameters Sample A (lower end) Sample B (intermediate value / Example 1) Sample C (high-end) relative density 98.5% >99.3% 98.8% <![CDATA[Piezoelectric coefficient d 33 (pC / N)]]> 38±2 42±3 40±2 Fracture toughness K~IC~ (MPa·m^1 / 2^) 5.5±0.3 6.2±0.4 5.8±0.3 Conclusion: As shown in Table 1, the samples prepared within the parameter range claimed in claim 1 all maintained a high level of overall performance, demonstrating the feasibility and rationality of this parameter range. Among them, the parameters near the middle value (sample B) exhibited the best overall performance.

[0034] Example 3: Comparative Experiment of Key Parameter - SiC Volume Fraction The volume fraction of SiC is a key parameter affecting the properties of composite materials. To demonstrate that 20-40 vol% is the preferred range, we kept other process conditions constant (same as in Example 1), changed only the volume fraction of SiC, and tested its properties.

[0035] Table 2 Performance Comparison of Different SiC Volume Fractions SiC volume fraction (vol%) Relative density (%) <![CDATA[Piezoelectric coefficient d 33 (pC / N)]]> <![CDATA[Fracture toughness K~IC (MPa·m 1 / 2 )]]> Remark 10 (outside the scope) 99.1 35±2 4.1±0.3 The toughening effect was not significant. 20 (within the range) 98.9 39±2 5.6±0.3 Significant performance improvement 30 (within the range) >99.3 42±3 6.2±0.4 Optimal performance 40 (within the range) 98.8 40±2 5.9±0.3 Performance remains excellent 45 (outside the scope) 97.5 36±3 5.2±0.4 Decreased density and performance degradation Table 2 shows that when the SiC volume fraction is in the range of 20-40 vol%, the composite material exhibits high density, excellent piezoelectric properties, and significant improvement in toughness. When the content is below 20 vol%, the toughening effect is insufficient; when the content is above 40 vol%, density and performance decrease due to powder agglomeration and interface problems. This set of comparative experiments strongly demonstrates that this parameter range is optimized and not arbitrarily set.

[0036] Example 4: Comparative Experiment of Key Parameter - Sintering Temperature Sintering temperature directly affects the densification and grain growth of ceramics and is a key process parameter. To prove that 1400-1600℃ is an effective range and 1500-1550℃ is a preferred range, we kept other conditions fixed (same as in Example 1, SiC 30 vol%) and only changed the SPS sintering temperature.

[0037] Table 3. Performance Comparison at Different Sintering Temperatures Sintering temperature (°C) Relative density (%) <![CDATA[Piezoelectric coefficient d 33 (pC / N)]]> Fracture toughness K~IC~ (MPa·m^1 / 2^) Remark 1350 (outside the range) 95.2 28±4 3.8±0.3 Insufficient sintering results in low density. 1400 (within the range) 98.5 38±2 5.5±0.3 Good performance Within 1500 (range) >99.3 42±3 6.2±0.4 Optimal performance 1550 (within the range) 99.0 41±2 6.0±0.3 Excellent performance 1600 (within the range) 98.7 39±3 5.7±0.4 Good performance 1650 (outside the scope) 97.0 33±3 4.9±0.4 Excessive grain growth leads to performance degradation. The data in Table 3 show that high density and performance can be achieved when sintering within the range of 1400-1600℃. Too low a temperature results in incomplete densification, while too high a temperature may lead to abnormal grain growth or second-phase reactions, impairing performance. Optimal performance occurs within a narrow range of 1500-1550℃. This experiment provides sufficient support for defining the preferred sintering temperature range in the dependent claims.

[0038] Comparative Example 1: Preparation of La2Be2O5 / 30 vol% SiC composite ceramics (solid-phase mechanical mixing method) This comparative example uses the traditional solid-phase mechanical mixing method, but adds the same proportion (30 vol%) of SiC as in Example 1 to evaluate the effect of SiC composite under the traditional method.

[0039] Powder mixing Weigh out high-purity lanthanum oxide (La2O3, 99.9%), beryllium oxide (BeO, 99.9%), and nano-β-SiC powder (30 vol%). Add the raw materials and anhydrous ethanol together into a planetary ball mill and ball mill for 6 hours (350 rpm) to ensure uniform mixing.

[0040] Drying and calcination The ball-milled slurry was dried at 80°C for 12 hours. The mixed powder was then calcined at 1400°C for 4 hours (air atmosphere, heating rate 5°C / min).

[0041] Forming and sintering Polyvinyl alcohol solution was added to the calcined powder as a binder, and the powder was pressed into a green body of the desired shape. Finally, it was sintered at 1500℃ under normal pressure for 4 hours to obtain La2Be2O5 / 30vol%SiC mixed ceramic.

[0042] Comparative Example 2: Preparation of pure-phase La2Be2O5 ceramics (in-situ sol-gel method, without SiC addition) This example uses the same in-situ sol-gel method and sintering process as Example 1, but without adding SiC nanoparticles to prepare pure-phase La2Be2O5 ceramics for comparative evaluation of the contribution of SiC composites to material properties.

[0043] 1. Preparation of precursor sol Lanthanum isopropoxide (La(OC3H7)3) and beryllium tert-butoxide (Be(OC4H9)2) were dissolved in ethanol at a molar ratio of La:Be = 1:1, and acetylacetone (acetylacetone:Be) was added. 2+ =1.2:1) to inhibit hydrolysis; add citric acid (CA:total metal ions=1.5:1), stir at 60℃ to form a transparent complex sol (viscosity≈18 mPa·s).

[0044] 2. Hydrolysis-gelation Deionized water (H2O:alkoxide = 1.8:1) was added dropwise directly to the above precursor sol, and the pH was adjusted to 4.0 ± 0.2 with acetic acid; the mixture was stirred at 65℃ for 8 h to obtain a colorless and transparent wet gel.

[0045] 3. Supercritical fluid drying The wet gel was replaced with liquid CO2 10 times in sequence, and then dried under supercritical conditions (45℃ / 12 MPa) for 3 h to obtain a pure phase La2Be2O5 dry gel with a porosity of <3%.

[0046] 4. Spark Plasma Sintering (SPS) After grinding the dry gel powder, a ceramic green body with a thickness of 0.5 mm was prepared by tape casting. SPS sintering was then performed at 1550℃ (heating rate 200℃ / min, holding time 5 minutes, Ar atmosphere) to obtain dense, pure-phase La2Be2O5 ceramic.

[0047] Comparative Example 3: Preparation of La2Be2O5 ceramic materials by solid-phase mechanical mixing Weigh out high-purity lanthanum oxide (La2O3, 99.9%) and beryllium oxide (BeO, 99.9%), and mix them according to the stoichiometric ratio La:Be = 2:2.

[0048] The raw materials were added to anhydrous ethanol and ball-milled in a planetary ball mill for 4 hours at 300 rpm. They were then dried at 80°C for 12 hours to obtain a uniform powder.

[0049] The powder was placed in an alumina crucible and calcined in a box furnace at a heating rate of 5℃ / min, a calcination temperature of 1400℃, and a holding time of 4 hours. After cooling to room temperature, La2Be2O5 ceramic powder was obtained.

[0050] The powder was mixed with an appropriate amount of polyvinyl alcohol solution as a binder, and then pressed into a disc with a diameter of 10 mm and a thickness of 2 mm. Subsequently, the binder was removed and a second sintering was carried out at 1300℃ for 4 hours.

[0051] Comparative Example 4: Preparation of La2Be2O5 ceramic materials (metal alkoxide precursor) High-purity nanoparticles are formed by molecular-level hydrolysis-condensation using lanthanum isopropoxide (La(OC3H7)3) and beryllium tert-butoxide (Be(OC4H9)2) as raw materials.

[0052] Specific implementation steps: Precursor formulation In an argon-protected glove box (O2 < 0.1 ppm), La(OC3H7)3 and Be(OC4H9)2 were dissolved in anhydrous ethanol at a molar ratio of La:Be = 1:1, and acetylacetone (metal ion:acetylacetone = 1:1.5 molar ratio) was added. The mixture was stirred at 40°C for 1 hour to form a homogeneous solution.

[0053] Hydrolysis control Add deionized water (water / alkoxide molar ratio R=2:1), adjust pH to 4.5 with acetic acid, and stir at 60℃ for 4 hours until a transparent sol is formed (viscosity ≈25 mPa·s).

[0054] Gelization and drying The sol was transferred to a polytetrafluoroethylene mold and aged at 40°C and 60%RH for 48 hours to obtain an elastic wet gel; it was then vacuum dried at 80°C for 12 hours and ground to obtain La2Be2O5 nanoparticles (particle size 80±20 nm, specific surface area 35 m²). 2 / g).

[0055] Sintering process Spark plasma sintering (SPS): The powder is placed in a graphite mold and held at 1420℃ and 40 MPa pressure for 5 minutes (Ar atmosphere) with a heating rate of 100℃ / min to obtain a ceramic body with a density >98% (grain size 0.8 μm).

[0056] Example 5: Piezoelectric Performance Test After polishing, a 200 nm thick Au electrode is sputtered onto the surface of the ceramic sample, using a quasi-static d-electrode. 33The piezoelectric coefficient was measured using a tester (ZJ-6A, Chinese Academy of Sciences) under a sinusoidal force of 0.25 N (frequency 0.5 Hz). The electromechanical coupling coefficient k was also measured. p The resonant / anti-resonant frequencies (fo) were obtained in the frequency range of 10 kHz–1 MHz using an impedance analyzer (Agilent 4294A). r / f a ), and calculate according to the IEEE standard formula: The following are the piezoelectric coefficients (di) for three different preparation methods (organic salt sol-gel method, solid-phase mechanical mixing method, and La2Be2O5 / 30 vol% SiC composite ceramic benchmark group). 33 ) and longitudinal electromechanical coupling coefficient (k 33 Test results.

[0057] Table 4. Comparison of piezoelectric properties of different preparation methods and components Performance parameters Solid-phase mechanical mixing method (pure phase) (Comparative Example 3) Solid-phase mechanical mixing method + 30 vol% SiC (Comparative Example 1) In-situ sol-gel method (pure phase) (Comparative Example 2) Organic salt sol-gel method (pure phase) (Comparative Example 4) <![CDATA[La2Be2O5 / 30 vol% SiC composite ceramic (Example 1)]]> relative density 95.2±1.8% 93.5±2.1% 98.1±0.6% 98.7±0.5% >99.3% <![CDATA[Piezoelectric coefficient d 33 (pC / N)]]> 28±5 25±4 36±3 35±2 42±3 <![CDATA[Planar electromechanical coupling coefficient k p > 0.18±0.03 0.17±0.03 0.26±0.02 0.25±0.02 0.31±0.02 <![CDATA[Dielectric loss tanδ (10⁻ 4 )]]> 12.0 (10 GHz) 14.5 (10 GHz) 6.8 (10 GHz) 7.2 (10 GHz) 4.5 (10 GHz) Thermal conductivity (W / m·K, RT) 38.7 41.2 53.5 52.1 65.3 By comparison and referring to Table 4, it can be found that the product obtained by this method in the La2Be2O5 / 30vol%SiC Example 1 benchmark group has better properties than the solid-phase mechanical mixing method and the organic salt sol-gel method. The piezoelectric coefficient d 33 The pC / N ratio is as high as 42±3. Furthermore, the product obtained by the method of this invention in the La2Be2O5 / 30vol%SiC benchmark group exhibits better performance than that obtained by the in-situ sol-gel method (pure phase) in Comparative Example 2, indicating that the performance of La2Be2O5 ceramics is improved through the composite of nano-β-SiC powder.

[0058] Example 6: Toughness Test The ceramic sample was cut into pieces measuring 3×6×30 mm. A universal testing machine (Instron 5569) was used with a loading rate of 0.5 mm / min. The load-displacement curve was recorded, and K was calculated. IC = (P max ·Y) / (B·W 1 / 2 ), where Y is the geometric factor, B and W are the sample thickness and width, and the average value of 5 samples is taken for each group of data, with a standard deviation of <5%.

[0059] Table 5 Comparison of toughness data for different preparation methods and components Preparation method <![CDATA[K IC (MPa·m 1 / 2 )]]> Solid-phase mechanical mixing method (pure phase) (Comparative Example 3) 1.8 ± 0.2 Solid-phase mechanical mixing method + 30 vol% SiC (Comparative Example 1) 1.6 ± 0.3 Organic salt sol-gel method (pure phase) (Comparative Example 4) 3.5 ± 0.2 In-situ sol-gel method (pure phase) (Comparative Example 2) 3.8 ± 0.3 30 vol% SiC composite (Example 1) 6.2 ± 0.4 The toughness test results in Table 5 further verified the above conclusions: (1) The in-situ sol-gel method described in this invention has much higher toughness than the solid-state method even without the addition of SiC, which is due to the uniform fine-grained structure formed by this method. (2) The introduction of SiC (Example 1) has achieved a leap in toughness based on the optimized method, K IC (MPa·m 1 / 2 Reaching 6.2 MPa·m 1 / 2 This is the result of the synergistic effect of the preparation method and the composite material components. (3) Comparative Example 1 shows that without improving the interfacial bonding, simply mixing SiC cannot achieve a toughening effect.

[0060] Example 7: Performance Evaluation of High-Frequency Vibration Detection To directly verify the advantages of the La2Be2O5 / 30vol%SiC composite ceramic prepared in this invention in high-frequency vibration detection, this embodiment uses the standard test method for high-frequency performance of piezoelectric ceramics to quantitatively characterize its frequency response range and detection sensitivity.

[0061] 1. Sample preparation for testing: Sample A: La2Be2O5 / 30vol%SiC composite ceramic prepared in this invention (obtained in Example 1).

[0062] Sample B: Pure-phase La2Be2O5 ceramic prepared by the organic salt sol-gel method described in Comparative Example 2.

[0063] Sample C: Pure-phase La2Be2O5 ceramic prepared by the solid-phase mechanical mixing method described in Comparative Example 1.

[0064] All samples were processed into circular discs with a diameter of 10 mm and a thickness of 1 mm, coated with silver electrodes on both sides, and polarized at 150°C (polarization electric field of 3 kV / mm, heat treatment for 30 minutes).

[0065] 2. Testing Method: Impedance Characteristic Testing: Using a precision impedance analyzer (Agilent 4294A), the impedance amplitude (|Z|) and phase (θ) spectrum of the sample were measured in the frequency range of 1 MHz to 50 MHz. The impedance was then measured at the resonant frequency (f...). r ) and anti-resonant frequency (f a ) Calculate its thickness electromechanical coupling coefficient (k) t ), k t The higher the value, the higher the material's efficiency in converting electrical energy to mechanical energy at high frequencies. The formula is: High-frequency vibration sensitivity test: The sample was used as a sensor and mounted on a standard high-frequency vibration stage (TIRA TV51110). The vibration stage generated a high-frequency vibration signal with constant acceleration (10 g), with the frequency swept from 100 kHz to 5 MHz. The voltage signal output by the sample was recorded using an oscilloscope, and its voltage sensitivity (unit: mV / g) was calculated.

[0066] 3. Test Results and Analysis: Table 6 Comparison of High-Frequency Vibration Detection Performance Performance parameters Sample C (Solid-phase mixing method) Sample B (sol-gel pure phase) Sample A (Composite material of this invention) <![CDATA[Thickness resonance frequency f r (MHz)]]> 8.5 12.1 15.8 <![CDATA[Thickness electromechanical coupling coefficient k t (%)]]> 18.5 26.3 34.7 -3dB bandwidth (MHz) 2.1 3.5 5.8 Voltage sensitivity (mV / g) @ 1MHz 0.85 1.35 2.20 Available frequency range (MHz) * 1 - 10.5 1 - 15.5 1 - 21.5 The usable frequency range is defined as the frequency interval where the voltage sensitivity is not less than 10% of the peak value.

[0067] The results in Table 6 show that the present invention has the following advantages: 1. Wider frequency response: The -3dB bandwidth and usable frequency range of the composite material of this invention (sample A) are significantly higher than those of the two comparative examples. This directly proves that it can effectively respond to high-frequency vibration signals with a wider frequency band, successfully solving the problem of "limited frequency response range" mentioned in the background art.

[0068] 2. Higher detection sensitivity: At a high frequency of 1 MHz, the voltage sensitivity of sample A is 2.6 times that of comparative example C and 1.6 times that of comparative example B. This indicates that under the same intensity of vibration input, the material of this invention can generate a stronger electrical signal, greatly improving the detection signal-to-noise ratio and the ability to capture weak signals.

[0069] 3. Excellent high-frequency energy conversion efficiency: Sample A has a thickness electromechanical coupling coefficient (k) as high as 34.7%. t The superior high-frequency performance is fundamentally due to the introduction of SiC and the dense, uniform, and firmly bonded microstructure formed by the in-situ sol-gel process in this invention, which effectively promotes the transmission and conversion of high-frequency stress / strain.

[0070] Direct high-frequency vibration testing experiments have confirmed that, compared with traditional La2Be2O5 ceramics, the La2Be2O5 / 30vol%SiC composite material provided by this invention has a wider frequency response range, higher detection sensitivity, and better high-frequency energy conversion efficiency, making it particularly suitable for demanding high-frequency vibration testing scenarios.

[0071] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing La2Be2O5 composite materials, characterized in that, Includes the following steps: Step 1: Add nano-β-SiC powder to a mixture of ethanol and water to prepare a SiC suspension; Step 2: Dissolve lanthanum isopropoxide and beryllium tert-butoxide in ethanol, add acetylacetone and citric acid to form a precursor complex sol, and add the SiC suspension from Step 1 to the precursor complex sol. Step 3: Add deionized water dropwise to the solution obtained in Step 2 to adjust the pH to 3.5-5.0, and react at 60-80℃ for 6-10 hours to obtain a gel; Step 4: The gel is subjected to 8-12 cycles of liquid CO2 replacement and dried under supercritical conditions to obtain a composite dry gel; Step 5: Pour the mixed slurry into a mold to prepare a ceramic green body, and calcine it at 1400-1600℃ to obtain La2Be2O5 composite ceramic, wherein the composite ceramic contains 20-40 vol% SiC.

2. The method for preparing La2Be2O5 composite material according to claim 1, characterized in that: In step 1, the average particle size of the nano-β-SiC powder is 80 nm. The etched SiC powder is added to an ethanol / water mixture.

3. The method for preparing La2Be2O5 composite material according to claim 1, characterized in that: In step 2, lanthanum isopropoxide and beryllium tert-butoxide are in the form of La 3+ With Be 2+ Soluble in ethanol at a molar ratio of 1:1 with acetylacetone and Be 2+ The molar ratio is 1.0:1 - 1.5:1, and the molar ratio of citric acid to total metal ions is 1.0:1 - 2.0:

1.

4. The method for preparing La2Be2O5 composite material according to claim 1, characterized in that: In step 2, the mixture is stirred at 60°C to form a transparent complex sol precursor. The SiC suspension is added to the precursor sol at a droplet acceleration rate of 1 mL / min.

5. The method for preparing La2Be2O5 composite material according to claim 1, characterized in that: In step 3, the ratio of deionized water to alkoxide is 1.8:1, the pH is adjusted to 4.0±0.2, and the reaction conditions are 65℃ for 8 h.

6. The method for preparing La2Be2O5 composite material according to claim 1, characterized in that: In step 4, the conditions for supercritical drying are: temperature 40-50℃, pressure 10-15 MPa, and time 2-4 hours.

7. The method for preparing La2Be2O5 composite material according to claim 1, characterized in that: In step 5, a ceramic blank with a thickness of 0.5 mm is prepared by tape casting or slip casting, and the sintering temperature is 1500-1550℃, and the temperature is held for 4-6 minutes to obtain the La2Be2O5 and SiC composite ceramic.

8. The La2Be2O5 composite material obtained by the method according to any one of claims 1-7.

9. The application of the La2Be2O5 composite material obtained by the method according to claim 8 in high-frequency vibration detection.

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