High-temperature-resistant piezoelectric ceramic sheet for buzzer and preparation method thereof

Abstract

The application belongs to the technical field of piezoelectric functional ceramic materials, and particularly relates to a high-temperature-resistant piezoelectric ceramic sheet for a buzzer sheet and a preparation method thereof. The preparation method of the high-temperature-resistant piezoelectric ceramic sheet comprises the following steps: S1, mixing niobium pentoxide, sodium carbonate, potassium carbonate, antimony trioxide, rare earth oxides and lithium carbonate, and then performing ball milling treatment to obtain a ball milling material; S2, performing pre-burning treatment on the ball milling material in step S1 to obtain a pre-burning material; S3, mixing and grinding the pre-burning material in step S2 with a binder, sieving, and pressing into a sheet to obtain a green porcelain body; S4, performing glue removal treatment and sintering treatment on the green porcelain body in step S3 to obtain a ceramic sheet; and S5, performing silver coating treatment and polarization treatment on the ceramic sheet in step S4 to obtain the high-temperature-resistant piezoelectric ceramic sheet for the buzzer sheet. On the basis of not using lead elements, the application not only ensures a high density, but also effectively improves the high-temperature resistance of the material, so that the application is better applied to the buzzer sheet field.

Description

Technical Field

[0001] This invention belongs to the field of piezoelectric functional ceramic materials technology, specifically relating to a high-temperature resistant piezoelectric ceramic sheet for buzzer chips and its preparation method. Background Technology

[0002] When an external force is applied to a piezoelectric material and it is deformed, the positive and negative charge centers inside its crystal lattice undergo relative displacement, resulting in the formation of equal but opposite bound charges on the material surface. This asymmetry in charge distribution induces the generation of polarized charges. If the external force is removed, the material returns to its original state, the surface charges disappear, and the charge distribution returns to equilibrium. This process of interconversion between mechanical and electrical energy is called the piezoelectric effect. Piezoelectric ceramics are hard and brittle ceramic materials formed through high-temperature sintering that can interconvert mechanical and electrical energy. Due to their superior electromechanical coupling effect, they hold an irreplaceable technological position in high-end technology fields such as buzzers, ultrasonic transducers, precision sensors, and acoustic transducers.

[0003] The main performance parameters of piezoelectric ceramic materials include: (1) dielectric properties, where the relative permittivity characterizes the ability of the dielectric material to store charge, and its value reflects the polarization characteristics of the material. Dielectric loss refers to the power loss caused by energy dissipation of the dielectric material under the action of alternating electric field; (2) piezoelectric properties, which characterize the coupling efficiency of the material in the process of mutual conversion between mechanical energy and electrical energy, specifically manifested as the linear response relationship between mechanical parameters and electrical parameters; (3) Curie temperature, the characteristics of ferroelectric crystals are only maintained in a specific temperature range. Once the ambient temperature exceeds the critical threshold, its spontaneous polarization phenomenon will disappear, and the material will then transform into the paraelectric state. This transformation process from ferroelectric phase to paraelectric phase is defined as ferroelectric phase transition, and the corresponding critical temperature is called Curie temperature.

[0004] Chinese patent (publication number CN115536392A) discloses a piezoelectric ceramic sheet for a high-temperature multilayer piezoelectric actuator and its preparation method. This invention, through trace element doping, adjustment of the lead-zirconium-titanium ratio, and the addition of appropriate sintering aids, enables the ceramic to generate a liquid phase during sintering, promoting grain growth. Therefore, the prepared piezoelectric ceramic sheet possesses excellent piezoelectric properties while reducing the sintering temperature, and exhibits large deformation displacement and good stability. However, the piezoelectric ceramic sheet prepared by this patented technology requires the use of toxic lead, and the Curie temperature and density of the material need further improvement.

[0005] Therefore, there is an urgent need for a piezoelectric ceramic sheet that, without using lead, uses niobium pentoxide as the main raw material, combined with rare earth oxides and other components, to ensure that the piezoelectric ceramic sheet has good high-temperature resistance and improve the material density, so that it can be better applied in the field of buzzer sheets. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a high-temperature resistant piezoelectric ceramic sheet for buzzers and its preparation method. The invention first mixes niobium pentoxide, sodium carbonate, potassium carbonate, antimony trioxide, rare earth oxides, and lithium carbonate, then ball-mills the mixture to obtain a ball milling material. This material is then pre-fired to obtain a pre-fired material, which is then mixed with a binder, ground, sieved, and pressed into a sheet to obtain a green ceramic blank. Finally, the blank undergoes debinding, sintering, silver coating, and polarization treatments to obtain the high-temperature resistant piezoelectric ceramic sheet for buzzers.

[0007] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: In a first aspect, this invention provides a method for preparing a high-temperature resistant piezoelectric ceramic sheet for a buzzer, comprising the following steps: S1. Niobium pentoxide, sodium carbonate, potassium carbonate, antimony trioxide, rare earth oxides, and lithium carbonate are mixed and then ball-milled to obtain ball milling material; S2. Pre-calcining the ball milling material described in step S1 to obtain pre-calcined material; S3. Mix and grind the pre-fired material described in step S2 with the binder, sieve, press into sheets, and obtain a green ceramic blank. S4. The raw ceramic blank described in step S3 is subjected to debinding and sintering treatment to obtain ceramic slabs; S5. The ceramic sheet described in step S4 is subjected to silver coating and polarization treatment to obtain a high-temperature resistant piezoelectric ceramic sheet for buzzer.

[0008] As a preferred technical solution of the present invention, the conditions for ball milling in step S1 are: ball milling at a speed of 360~400 r / min for 4~6 hours, and baking at 70~80℃ for 2~4 hours.

[0009] As a preferred technical solution of the present invention, the pre-sintering conditions in step S2 are as follows: the ball mill is transferred to a sintering furnace and heated to 840-860°C at a heating rate of 2-4°C / min and held at that temperature for 4-6 hours.

[0010] As a preferred technical solution of the present invention, the conditions for the glue removal process in step S4 are: glue removal temperature of 640~660℃ and glue removal time of 60~80min.

[0011] As a preferred technical solution of the present invention, the sintering conditions in step S4 are: sintering temperature of 1060~1080℃ and sintering time of 3~4h.

[0012] As a preferred technical solution of the present invention, the silver coating process in step S5 is as follows: after polishing the ceramic piece, silver paste is applied by screen printing and then fired at 780~800℃ for 30~40 minutes.

[0013] As a preferred technical solution of the present invention, the polarization treatment step S5 is as follows: treat in silicone oil at 120~130℃ with a polarization voltage of 4~8kV / mm for 20~30min, and let stand for 24~36h.

[0014] As a preferred technical solution of the present invention, the components in step S1 include, by weight: 300-330 parts of niobium pentoxide, 70-80 parts of sodium carbonate, 60-70 parts of potassium carbonate, 20-24 parts of antimony trioxide, 12-18 parts of rare earth oxides, and 2-4 parts of lithium carbonate.

[0015] As a preferred embodiment of the present invention, the weight parts of niobium pentoxide may be 300 parts, 310 parts, 320 parts or 330 parts, etc.

[0016] As a preferred embodiment of the present invention, the sodium carbonate may be in the following weight proportions: 70 parts, 72 parts, 74 parts, 76 parts, 78 parts, or 80 parts, etc.

[0017] As a preferred embodiment of the present invention, the potassium carbonate may be in the following weight proportions: 60 parts, 62 parts, 64 parts, 66 parts, 68 parts, or 70 parts, etc.

[0018] As a preferred embodiment of the present invention, the antimony trioxide may be present in the following weight proportions: 20 parts, 21 parts, 22 parts, 23 parts, or 24 parts, etc.

[0019] As a preferred embodiment of the present invention, the weight parts of the rare earth oxide can be 12, 13, 14, 15, 16, 17 or 18 parts, etc.

[0020] As a preferred embodiment of the present invention, the lithium carbonate may be in the form of 2 parts, 3 parts, or 4 parts by weight.

[0021] As a preferred embodiment of the present invention, the niobium pentoxide in step S1 is tetragonal niobium pentoxide or pseudohexagonal niobium pentoxide.

[0022] As a preferred embodiment of the present invention, the mass ratio of tetragonal niobium pentoxide to pseudohexagonal niobium pentoxide in the niobium pentoxide is (1~2):1.

[0023] As a preferred technical solution of the present invention, the preparation steps of the tetragonal niobium pentoxide are as follows: niobium powder is placed in a tube furnace under an argon atmosphere. First, the argon flow rate is controlled at 20~30 mL / min, and the temperature is raised to 900~920℃ at a heating rate of 10℃ / min and held for 50~60 min. Then, the oxygen valve is opened to introduce oxygen, and the oxygen flow rate is controlled at 20~30 mL / min for oxidation treatment for 60~80 min. Finally, the oxygen valve is closed, and the mixture is cooled to room temperature to obtain tetragonal niobium pentoxide.

[0024] As a preferred technical solution of the present invention, the preparation steps of the pseudo-hexagonal niobium pentoxide are as follows: niobium powder is placed in a tube furnace under an argon atmosphere. First, the argon flow rate is controlled at 20~30 mL / min, and the temperature is raised to 480~500℃ at a heating rate of 10℃ / min and held for 50~60 min. Then, the oxygen valve is opened to introduce oxygen, and the oxygen flow rate is controlled at 20~30 mL / min for oxidation treatment for 60~80 min. Finally, the oxygen valve is closed, and the mixture is cooled to room temperature to obtain pseudo-hexagonal niobium pentoxide.

[0025] This invention uses metallic niobium powder as raw material and employs a simple and controllable one-step thermal oxidation method to synthesize niobium pentoxide of different crystal systems. Tetragonal niobium pentoxide is prepared by controlling the temperature at 900~920℃, and pseudohexagonal niobium pentoxide is prepared by controlling the temperature at 480~500℃. By compounding niobium pentoxide of different crystal systems and controlling the mass ratio of the two, the overall performance of piezoelectric ceramic sheets is significantly improved.

[0026] As a preferred embodiment of the present invention, the rare earth oxide in step S1 is selected from one or more of erbium oxide, samarium oxide, dysprosium oxide, and europium oxide.

[0027] As a preferred embodiment of the present invention, the rare earth oxides are erbium oxide and samarium oxide.

[0028] As a preferred embodiment of the present invention, the mass ratio of erbium oxide to samarium oxide in the rare earth oxide is (2~3):1.

[0029] This invention incorporates rare earth oxides such as erbium oxide, samarium oxide, dysprosium oxide, and europium oxide into piezoelectric ceramic sheets. Rare earth elements can serve as effective modifiers, altering the internal crystal structure of the ceramic by adjusting the type and concentration of doping, and filling defects and impurities at grain boundaries, thereby significantly improving the overall performance of the material.

[0030] As a preferred embodiment of the present invention, the binder in step S3 is modified polyvinyl alcohol, which is prepared by heating and reacting polyvinyl alcohol powder and 2,3,5,6-tetrafluorobenzoyl chloride as raw materials.

[0031] As a preferred embodiment of the present invention, the heating reaction step is as follows: by weight, 90-100 parts of polyvinyl alcohol powder are added to 400-500 parts of dimethyl sulfoxide, heated to 80-90°C and stirred to dissolve for 50-60 minutes, then 10-20 parts of 2,3,5,6-tetrafluorobenzoyl chloride and 0.8-1.2 parts of triethylamine are added and heated to react at 60-70°C for 12-16 hours. After the reaction is completed, 400-500 parts of anhydrous ethanol are poured in to precipitate flocculent material, which is then centrifuged and dried to obtain modified polyvinyl alcohol.

[0032] This invention uses polyvinyl alcohol powder and 2,3,5,6-tetrafluorobenzoyl chloride as raw materials. Under heating conditions, the hydroxyl oxygen atom of polyvinyl alcohol acts as a nucleophile to attack the carbonyl carbon atom of tetrafluorobenzoyl chloride. Triethylamine acts as an acid-binding agent to neutralize acidic byproducts and promote the chemical equilibrium to shift towards the forward reaction. Tetrafluorobenzoyl ester side groups are grafted onto the polyvinyl alcohol molecular chain through acylation and esterification, thereby preparing modified polyvinyl alcohol containing benzene rings and fluorine elements.

[0033] As a preferred embodiment of the present invention, the amount of the binder is 5% of the mass fraction of the pre-fired material.

[0034] In a second aspect, the present invention provides a high-temperature resistant piezoelectric ceramic sheet for a buzzer prepared by the preparation method described in the first aspect.

[0035] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention uses tetragonal niobium pentoxide and pseudohexagonal niobium pentoxide to form a composite. The former has a dense structure and high packing density, small lattice distortion and strong intrinsic lattice stability. After being incorporated, it can effectively raise the Curie temperature. The latter has a hexagonal stacked structure and lattice vacancies between layers. During the sintering process, it fills the gaps between the green body particles through solid-phase diffusion, which makes up for the insufficient densification of the single tetragonal phase. Through the synergistic effect of the two different niobium pentoxide systems, the density and high temperature resistance of the piezoelectric ceramic sheet are effectively improved.

[0036] (2) The rare earth oxides of the present invention preferably use erbium oxide and samarium oxide. Erbium can effectively reduce the formation of oxygen vacancies inside the material and reduce the difference between lattice constants, thereby promoting the densification of ceramics. The introduction of samarium can increase the phase interface movement and domain wall movement energy, enabling piezoelectric ceramics to obtain higher Curie temperatures and effectively improve the high temperature resistance of piezoelectric ceramic sheets. By using erbium oxide and samarium oxide to be compounded, the two work together to improve the density and Curie temperature of piezoelectric ceramic sheets.

[0037] (3) The modified polyvinyl alcohol of the present invention introduces a large number of low surface energy carbon-fluorine bonds into the molecular chain, which enables the pre-sintered material to be better uniformly dispersed before molding, and significantly reduces the initial porosity in the green body; in addition, the benzene ring introduced by the modified polyvinyl alcohol helps to achieve more stable glue discharge, avoids violent gas expansion from damaging the grain boundaries and grain interior, thereby reducing micro-defects such as intracrystalline pores, and thus the final piezoelectric ceramic sheet obtains higher density. Attached Figure Description

[0038] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 The images show the XRD patterns of tetragonal niobium pentoxide and pseudohexagonal niobium pentoxide in Example 4 of this invention.

[0040] Figure 2 The images show the Raman spectra of tetragonal niobium pentoxide and pseudohexagonal niobium pentoxide in Example 4 of this invention.

[0041] Figure 3 The image shows the FTIR images of the modified polyvinyl alcohol and polyvinyl alcohol powder in Example 4 of this invention. Detailed Implementation

[0042] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0043] The sources of some components in the examples and comparative examples are as follows: Niobium powder, item number 4103001, was purchased from Forsmann Technology (Beijing) Co., Ltd. Sodium carbonate, CAS No. 497-19-8, purchased from Sinopharm Chemical Reagent Co., Ltd. Potassium carbonate, CAS No. 584-08-7, purchased from Sinopharm Chemical Reagent Co., Ltd. Antimony trioxide, CAS number 1309-64-4, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Erbium oxide, part number 6801001, was purchased from Forsmann Technology (Beijing) Co., Ltd. Samarium oxide, part number 6201001, was purchased from Forsmann Technology (Beijing) Co., Ltd. Dysprosium oxide, part number 6601003, was purchased from Forsmann Technology (Beijing) Co., Ltd. Lithium carbonate, CAS No. 554-13-2, purchased from Sinopharm Chemical Reagent Co., Ltd. Ordinary polyvinyl alcohol powder, product number P434372, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. 2,3,5,6-Tetrafluorobenzoyl chloride, CAS No. 107535-73-9, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Triethylamine, CAS No. 121-44-8, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Example

[0044] This embodiment provides a method for preparing a high-temperature resistant piezoelectric ceramic chip for a buzzer, including the following steps: S1. By weight, 330 parts of niobium pentoxide (220 parts of tetragonal niobium pentoxide and 110 parts of pseudohexagonal niobium pentoxide), 80 parts of sodium carbonate, 70 parts of potassium carbonate, 24 parts of antimony trioxide, 18 parts of erbium oxide, and 4 parts of lithium carbonate were mixed and ball-milled at 400 r / min for 4 h, and then baked at 80℃ for 2 h to obtain the ball milling material. S2. The ball milled material described in step S1 is transferred to a sintering furnace and heated to 860°C at a heating rate of 4°C / min and held at that temperature for 4 hours for pre-calcination treatment to obtain pre-calcined material. S3. Mix and grind the pre-fired material described in step S2 with binder-modified polyvinyl alcohol (5% of the mass fraction of the pre-fired material), sieve, and press into sheets to obtain a green ceramic blank. S4. The green ceramic blank described in step S3 is subjected to a debinding treatment (debinding temperature is 660℃, debinding time is 60min) and a sintering treatment (sintering temperature is 1080℃, sintering time is 3h) to obtain ceramic slabs. S5. After polishing the ceramic sheet described in step S4, silver paste is screen-printed onto it and fired at 800°C for 30 minutes. Then, it is treated in silicone oil at 130°C with a polarization voltage of 8kV / mm for 20 minutes and left to stand for 36 hours to obtain a high-temperature resistant piezoelectric ceramic sheet for buzzers.

[0045] The preparation of tetragonal niobium pentoxide is as follows: Niobium powder is placed in a tube furnace under an argon atmosphere. The argon flow rate is controlled at 30 mL / min, and the temperature is raised to 920℃ at a rate of 10℃ / min and held for 50 min. Then, the oxygen valve is opened to introduce oxygen, and the oxygen flow rate is controlled at 30 mL / min for oxidation treatment for 80 min. Finally, the oxygen valve is closed and the mixture is cooled to room temperature to obtain tetragonal niobium pentoxide.

[0046] The preparation of the pseudo-hexagonal niobium pentoxide is as follows: Niobium powder is placed in a tube furnace under an argon atmosphere. The argon flow rate is controlled at 30 mL / min, and the temperature is raised to 500℃ at a heating rate of 10℃ / min and held for 50 min. Then, the oxygen valve is opened to introduce oxygen, and the oxygen flow rate is controlled at 30 mL / min for oxidation treatment for 60 min. Finally, the oxygen valve is closed and the mixture is cooled to room temperature to obtain pseudo-hexagonal niobium pentoxide.

[0047] Preparation of the modified polyvinyl alcohol: 100 parts by weight of polyvinyl alcohol powder were added to 500 parts of dimethyl sulfoxide, heated to 90°C and stirred for 50 min to dissolve. Then, 20 parts of 2,3,5,6-tetrafluorobenzoyl chloride and 1.2 parts of triethylamine were added and heated at 70°C for 12 h. After the reaction was completed, 500 parts of anhydrous ethanol were poured in to precipitate flocculent material. The precipitate was centrifuged and dried to obtain modified polyvinyl alcohol. Example

[0048] This embodiment provides a method for preparing a high-temperature resistant piezoelectric ceramic chip for a buzzer, including the following steps: S1. By weight, 300 parts of niobium pentoxide (150 parts of tetragonal niobium pentoxide and 150 parts of pseudohexagonal niobium pentoxide), 70 parts of sodium carbonate, 60 parts of potassium carbonate, 20 parts of antimony trioxide, 12 parts of samarium oxide, and 2 parts of lithium carbonate are mixed and ball-milled at 360 r / min for 6 h, and then baked at 70 °C for 4 h to obtain the ball milling material. S2. The ball milled material described in step S1 is transferred to a sintering furnace and heated to 840°C at a heating rate of 2°C / min and held at that temperature for 6 hours for pre-calcination treatment to obtain pre-calcined material. S3. Mix and grind the pre-fired material described in step S2 with binder-modified polyvinyl alcohol (5% of the mass fraction of the pre-fired material), sieve, and press into sheets to obtain a green ceramic blank. S4. The green ceramic blank described in step S3 is subjected to a debinding treatment (debinding temperature is 640℃, debinding time is 80min) and a sintering treatment (sintering temperature is 1060℃, sintering time is 4h) to obtain ceramic slabs. S5. After polishing the ceramic sheet described in step S4, silver paste is screen-printed onto it and fired at 780°C for 40 minutes. Then, it is treated in silicone oil at 120°C with a polarization voltage of 8kV / mm for 30 minutes and left to stand for 24 hours to obtain a high-temperature resistant piezoelectric ceramic sheet for buzzers.

[0049] The preparation of tetragonal niobium pentoxide is as follows: Niobium powder is placed in a tube furnace under an argon atmosphere. The argon flow rate is controlled at 20 mL / min, and the temperature is raised to 900℃ at a rate of 10℃ / min and held for 60 min. Then, the oxygen valve is opened to introduce oxygen, and the oxygen flow rate is controlled at 20 mL / min for oxidation treatment for 60 min. Finally, the oxygen valve is closed and the mixture is cooled to room temperature to obtain tetragonal niobium pentoxide.

[0050] The preparation of the pseudo-hexagonal niobium pentoxide is as follows: Niobium powder is placed in a tube furnace under an argon atmosphere. The argon flow rate is controlled at 20 mL / min, and the temperature is raised to 480℃ at a heating rate of 10℃ / min and held for 60 min. Then, the oxygen valve is opened to introduce oxygen, and the oxygen flow rate is controlled at 20 mL / min for oxidation treatment for 60 min. Finally, the oxygen valve is closed and the mixture is cooled to room temperature to obtain pseudo-hexagonal niobium pentoxide.

[0051] Preparation of the modified polyvinyl alcohol: 90 parts by weight of polyvinyl alcohol powder were added to 400 parts of dimethyl sulfoxide, heated to 80°C and stirred for 60 min to dissolve. Then, 10 parts of 2,3,5,6-tetrafluorobenzoyl chloride and 0.8 parts of triethylamine were added and heated at 60°C for 16 h. After the reaction was completed, 400 parts of anhydrous ethanol were poured in to precipitate flocculent material. The precipitate was centrifuged and dried to obtain modified polyvinyl alcohol. Example

[0052] This embodiment provides a method for preparing a high-temperature resistant piezoelectric ceramic chip for a buzzer, including the following steps: S1. By weight, 310 parts of niobium pentoxide (200 parts of tetragonal niobium pentoxide and 110 parts of pseudohexagonal niobium pentoxide), 75 parts of sodium carbonate, 65 parts of potassium carbonate, 22 parts of antimony trioxide, 16 parts of dysprosium oxide, and 3 parts of lithium carbonate were mixed and ball-milled at 380 r / min for 5 h, and then baked at 75 °C for 3 h to obtain the ball milling material. S2. The ball milled material described in step S1 is transferred to a sintering furnace and heated to 850°C at a heating rate of 3°C / min and held at that temperature for 5 hours for pre-calcination treatment to obtain pre-calcined material. S3. Mix and grind the pre-fired material described in step S2 with binder-modified polyvinyl alcohol (5% of the mass fraction of the pre-fired material), sieve, and press into sheets to obtain a green ceramic blank. S4. The green ceramic blank described in step S3 is subjected to a debinding treatment (debinding temperature is 650℃, debinding time is 70min) and a sintering treatment (sintering temperature is 1070℃, sintering time is 3.5h) to obtain ceramic slabs. S5. After polishing the ceramic sheet described in step S4, silver paste is screen-printed onto it and fired at 790°C for 35 minutes. Then, it is treated in silicone oil at 125°C with a polarization voltage of 6kV / mm for 25 minutes and left to stand for 30 hours to obtain a high-temperature resistant piezoelectric ceramic sheet for buzzers.

[0053] The preparation of tetragonal niobium pentoxide is as follows: Niobium powder is placed in a tube furnace under an argon atmosphere. The argon flow rate is controlled at 25 mL / min, and the temperature is raised to 910℃ at a rate of 10℃ / min and held for 55 min. Then, the oxygen valve is opened to introduce oxygen, and the oxygen flow rate is controlled at 25 mL / min for oxidation treatment for 70 min. Finally, the oxygen valve is closed and the mixture is cooled to room temperature to obtain tetragonal niobium pentoxide.

[0054] The preparation of the pseudo-hexagonal niobium pentoxide is as follows: Niobium powder is placed in a tube furnace under an argon atmosphere. The argon flow rate is controlled at 25 mL / min, and the temperature is raised to 490℃ at a heating rate of 10℃ / min and held for 55 min. Then, the oxygen valve is opened to introduce oxygen, and the oxygen flow rate is controlled at 25 mL / min for oxidation treatment for 70 min. Finally, the oxygen valve is closed and the mixture is cooled to room temperature to obtain pseudo-hexagonal niobium pentoxide.

[0055] Preparation of the modified polyvinyl alcohol: 95 parts by weight of polyvinyl alcohol powder were added to 450 parts of dimethyl sulfoxide, heated to 85°C and stirred for 55 min to dissolve. Then, 15 parts of 2,3,5,6-tetrafluorobenzoyl chloride and 0.9 parts of triethylamine were added and heated at 65°C for 14 h. After the reaction was completed, 450 parts of anhydrous ethanol were poured in to precipitate flocculent material. The precipitate was centrifuged and dried to obtain modified polyvinyl alcohol. Example

[0056] The difference between this comparative example and Example 1 is that the rare earth oxides are replaced with 12 parts of erbium oxide and 6 parts of samarium oxide.

[0057] Comparative Example 1 The difference between this comparative example and Example 1 is that niobium pentoxide was replaced with 330 parts of tetragonal niobium pentoxide.

[0058] Comparative Example 2 The difference between this comparative example and Example 1 is that niobium pentoxide was replaced with 330 parts of pseudo-hexagonal niobium pentoxide.

[0059] Comparative Example 3 The difference between this comparative example and Example 1 is that ordinary polyvinyl alcohol powder (item number P434372) is used instead of modified polyvinyl alcohol as a binder.

[0060] The performance of the piezoelectric ceramic sheets provided in the above embodiments and comparative examples was tested using the following methods: (1) Density test: The test shall be conducted in accordance with the requirements of GB / T 25995-2010 Test method for density and apparent porosity of fine ceramics.

[0061] (2) Curie temperature test: The test shall be conducted in accordance with the requirements of GB / T 3389-2008 Test method for performance parameters of piezoelectric ceramic materials.

[0062] (3) Piezoelectric constant test: The test shall be conducted in accordance with the requirements of GB / T 3389-2008 Test method for performance parameters of piezoelectric ceramic materials.

[0063] The performance test data above are shown in Table 1.

[0064] Table 1 Performance Test Results Example 1 98.5 383 152 Example 2 98.2 379 149 Example 3 98.4 382 150 Example 4 99.1 390 155 Comparative Example 1 96.3 368 146 Comparative Example 2 97.1 357 145 Comparative Example 3 95.5 376 148 As can be seen from the above, the present invention first mixes niobium pentoxide, sodium carbonate, potassium carbonate, antimony trioxide, rare earth oxides and lithium carbonate and then ball-mills them to obtain ball milling material. Then, the ball milling material is pre-fired to obtain pre-fired material, which is then mixed and ground with a binder, sieved, pressed into sheets to obtain green ceramic blanks. Finally, the blanks are sequentially subjected to debinding treatment, sintering treatment, silver coating treatment and polarization treatment to obtain high-temperature resistant piezoelectric ceramic sheets for buzzer chips.

[0065] Compared with Example 1, the rare earth oxides were changed to 12 parts of erbium oxide and 6 parts of samarium oxide. Since the combination of erbium oxide and samarium oxide has a good synergistic effect, the density increased and the Curie temperature increased (Example 4).

[0066] Compared with Example 1, niobium pentoxide was replaced with 330 parts of tetragonal niobium pentoxide, which lacked the synergistic effect of pseudohexagonal niobium pentoxide, resulting in a decrease in density and a drop in Curie temperature (Comparative Example 1).

[0067] Compared with Example 1, niobium pentoxide was replaced with 330 parts of pseudohexagonal niobium pentoxide. The lack of the synergistic effect of tetragonal niobium pentoxide resulted in a decrease in density and a decrease in Curie temperature (Comparative Example 2).

[0068] Compared to Example 1, the use of ordinary polyvinyl alcohol powder (item number P434372) instead of modified polyvinyl alcohol as a binder resulted in a decrease in density due to the lack of the effect of modified polyvinyl alcohol (Comparative Example 3).

Claims

1. A method for preparing a high-temperature resistant piezoelectric ceramic sheet for a buzzer, characterized in that, Includes the following steps: S1. Niobium pentoxide, sodium carbonate, potassium carbonate, antimony trioxide, rare earth oxides, and lithium carbonate are mixed and then ball-milled to obtain ball milling material; S2. Pre-calcining the ball milling material described in step S1 to obtain pre-calcined material; S3. Mix and grind the pre-fired material described in step S2 with the binder, sieve, press into sheets, and obtain a green ceramic blank. S4. The raw ceramic blank described in step S3 is subjected to debinding and sintering treatment to obtain ceramic slabs; S5. The ceramic sheet described in step S4 is subjected to silver coating and polarization treatment to obtain a high-temperature resistant piezoelectric ceramic sheet for buzzer.

2. The method for preparing a high-temperature resistant piezoelectric ceramic sheet for a buzzer according to claim 1, characterized in that, The components in step S1, by weight, include: 300-330 parts niobium pentoxide, 70-80 parts sodium carbonate, 60-70 parts potassium carbonate, 20-24 parts antimony trioxide, 12-18 parts rare earth oxides, and 2-4 parts lithium carbonate.

3. The method for preparing a high-temperature resistant piezoelectric ceramic sheet for a buzzer according to claim 1, characterized in that, The niobium pentoxide mentioned in step S1 is tetragonal niobium pentoxide and pseudohexagonal niobium pentoxide; The mass ratio of tetragonal niobium pentoxide to pseudohexagonal niobium pentoxide in the niobium pentoxide is (1~2):

1.

4. The method for preparing a high-temperature resistant piezoelectric ceramic sheet for a buzzer according to claim 3, characterized in that, The preparation steps of the tetragonal niobium pentoxide are as follows: Niobium powder is placed in a tube furnace under an argon atmosphere. First, the argon flow rate is controlled at 20~30 mL / min, and the temperature is raised to 900~920℃ at a heating rate of 10℃ / min and held for 50~60 min. Then, the oxygen valve is opened to introduce oxygen, and the oxygen flow rate is controlled at 20~30 mL / min for oxidation treatment for 60~80 min. Finally, the oxygen valve is closed and the mixture is cooled to room temperature to obtain tetragonal niobium pentoxide.

5. The method for preparing a high-temperature resistant piezoelectric ceramic sheet for a buzzer according to claim 3, characterized in that, The preparation steps of the pseudo-hexagonal niobium pentoxide are as follows: Niobium powder is placed in a tube furnace under an argon atmosphere. First, the argon flow rate is controlled at 20~30 mL / min, and the temperature is raised to 480~500℃ at a heating rate of 10℃ / min and held for 50~60 min. Then, the oxygen valve is opened to introduce oxygen, and the oxygen flow rate is controlled at 20~30 mL / min for oxidation treatment for 60~80 min. Finally, the oxygen valve is closed and the mixture is cooled to room temperature to obtain pseudo-hexagonal niobium pentoxide.

6. The method for preparing a high-temperature resistant piezoelectric ceramic sheet for a buzzer according to claim 1, characterized in that, The rare earth oxide mentioned in step S1 is selected from one or more of erbium oxide, samarium oxide, dysprosium oxide, and europium oxide.

7. The method for preparing a high-temperature resistant piezoelectric ceramic sheet for a buzzer according to claim 6, characterized in that, The rare earth oxides are erbium oxide and samarium oxide; The mass ratio of erbium oxide to samarium oxide in the rare earth oxide is (2~3):

1.

8. The method for preparing a high-temperature resistant piezoelectric ceramic sheet for a buzzer according to claim 1, characterized in that, The adhesive in step S3 is modified polyvinyl alcohol, which is prepared by heating polyvinyl alcohol powder and 2,3,5,6-tetrafluorobenzoyl chloride as raw materials.

9. The method for preparing a high-temperature resistant piezoelectric ceramic sheet for a buzzer according to claim 8, characterized in that, The heating reaction steps are as follows: 90-100 parts by weight of polyvinyl alcohol powder are added to 400-500 parts of dimethyl sulfoxide, heated to 80-90℃ and stirred to dissolve for 50-60 minutes, then 10-20 parts of 2,3,5,6-tetrafluorobenzoyl chloride and 0.8-1.2 parts of triethylamine are added and heated to 60-70℃ for 12-16 hours. After the reaction is completed, 400-500 parts of anhydrous ethanol are poured in to precipitate flocculent material, which is then centrifuged and dried to obtain modified polyvinyl alcohol.

10. A high-temperature resistant piezoelectric ceramic sheet for a buzzer, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 9.

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