A multi-element doped potassium sodium niobate-based piezoelectric ceramic and its preparation method and application

Abstract

In order to solve the problems existing in the prior art, the present invention provides a multi-element doped potassium sodium niobate-based piezoelectric ceramic, the chemical formula of which is: (1-x)(K 0.48 Na 0.52 ) 0.965 Li 0.035 (Nb 0.97 Sb 0.03 )O3‑x(Bi 0.5 Ag 0.5 )ZrO3‑yM A O B , wherein 0.01≤x≤0.02, 0.1mol.%≤y≤0.2mol.%. The M A O B This is a composite of Fe2O3, ZnO, and SnO2. By multi-element doping and modification of potassium sodium niobate-based piezoelectric ceramics, the present invention produces a piezoelectric ceramic with a high piezoelectric constant, a high electromechanical coupling coefficient, and a low dielectric loss coefficient. The resulting electroacoustic device, particularly a buzzer, exhibits excellent performance.

Description

Technical Field

[0001] The present invention relates to the technical field of piezoelectric ceramic preparation, in particular to a multi-element doped potassium sodium niobate-based piezoelectric ceramic and a preparation method thereof. Background Art

[0002] Potassium sodium niobate ((K,Na)NbO3, KNN) lead-free piezoelectric ceramics are a piezoelectric material with a perovskite structure. They have high Curie temperature, excellent piezoelectric properties, and are environmentally friendly. They are currently one of the most likely systems to replace lead-based piezoelectric ceramics in device manufacturing applications. The piezoelectric constant d of pure potassium sodium niobate piezoelectric ceramics prepared by ordinary sintering process is 33 Chemical doping in potassium sodium niobate-based piezoelectric ceramics effectively improves the sintering characteristics of the ceramics, obtains high-density ceramic bodies, and significantly improves their piezoelectric properties.

[0003] Existing technology can improve the piezoelectric constant d of potassium sodium niobate-based piezoelectric ceramics by doping modification. 33 , but at the same time it will reduce the electromechanical coupling coefficient Kp of potassium sodium niobate-based piezoelectric ceramics. At present, the d 33 There are also reports on modified potassium sodium niobate-based piezoelectric ceramics with piezoelectric constants exceeding 350pC / N and even exceeding 400pC / N. However, the electromechanical coupling coefficient and dielectric loss coefficient of the modified potassium sodium niobate-based piezoelectric ceramics with high piezoelectric constants will deteriorate to varying degrees, thereby limiting the scope of use of the modified potassium sodium niobate-based piezoelectric ceramics, especially their use in electroacoustic components. Summary of the Invention

[0004] In view of the problems existing in the prior art, the present invention provides a multi-element doped potassium sodium niobate-based piezoelectric ceramic, the chemical formula of which is:

[0005] (1-x)(K 0.48 Na 0.52 ) 0.965 Li 0.035 (Nb 0.97 Sb 0.03 )O3-x(Bi 0.5 Ag 0.5 )ZrO3-yM A O B , wherein 0.01≤x≤0.02, 0.1mol.%≤y≤0.2mol.%. The M A O B It is a complex of Fe2O3, ZnO and SnO2.

[0006] The present invention exemplarily provides a multi-element doped potassium sodium niobate-based piezoelectric ceramic, the chemical formula of which is (1-x)(K 0.48Na 0.52 ) 0.965 Li 0.035 (Nb 0.97 Sb 0.03 )O3-x(Bi 0.5 Ag 0.5 )ZrO3-yM A O B wherein x=0.01, y=0.14 mol%. and M A O B It is a composite oxide of Fe2O3, ZnO and SnO2 in a molar ratio of Fe:Zn:Sn=7:1:2.

[0007] Furthermore, the preparation method of the multi-element doped potassium sodium niobate-based piezoelectric ceramic includes:

[0008] Step 1: Prepare K2CO3, Na2CO3, Li2CO3, Nb2O5, Sb2O3, Bi2O3, Ag2O, ZrO2, Fe2O3, ZnCO3, and SnO2 according to the chemical formula. K2CO3, Na2CO3, Li2CO3, Nb2O5, Sb2O3, Bi2O3, Ag2O, and ZrO2 are used as component A, and Fe2O3, ZnCO3, and SnO2 are used as component B.

[0009] Step 2: Component A and component B are ball-milled for the first time and dried.

[0010] Step 3: Component A is pre-fired at 800-900°C for 4-6 hours to obtain pre-fired component A. Component B is pre-fired at 700-750°C for 4-6 hours to obtain pre-fired component B.

[0011] Step 4: Ball mill the pre-calcined component A to a D50 of ≤1 μm and dry it to obtain a secondary ball milled component A. Ball mill the pre-calcined component B to a D50 of ≤0.8 μm and dry it to obtain a secondary ball milled component B.

[0012] Step 5: Place the secondary ball-milled component A and the secondary ball-milled component B into a closed mixing device for mixing, and obtain a mixed component C after the mixing is completed.

[0013] Step 6: After drying the mixed component C, add the adhesive, mix thoroughly, and prepare a tablet.

[0014] Step 7: Debinding the pressed sheet and then sintering it. The sintering temperature is 1050-1100° C. and the sintering time is 6-7 hours.

[0015] After the sintering treatment in step 8 is completed, the product is naturally cooled to room temperature to obtain the multi-element doped potassium sodium niobate-based piezoelectric ceramic.

[0016] Furthermore, the enclosed mixing device in step 5 includes: a power controller and a closed hollow mixing chamber, and the mixing chamber is rotatably mounted on a bracket and driven to rotate by a driving motor.

[0017] The mixing chamber is provided with a closable switch door, an ultrasonic generator is provided inside the mixing chamber, a tooth groove / tooth belt is provided on the outer wall of the mixing chamber, the driving motor drives the tooth disc to rotate, and the tooth disc is toothed with the tooth groove / tooth belt.

[0018] An external power source supplies power to the drive motor and ultrasonic generator via the power controller. The power controller includes an electronically controlled multi-way switch, a first microprocessor, and an ultrasonic power controller. The electronically controlled multi-way switch has an electrical input interface electrically connected to the external power source, a control terminal of the electronically controlled multi-way switch is signal-connected to the first microprocessor, one electrical output interface of the electronically controlled multi-way switch is electrically connected to the electrical input interface of the ultrasonic power controller, and another electrical output interface is electrically connected to the electrical input interface of the drive motor. The ultrasonic power controller controls the power supply to the ultrasonic generator.

[0019] Furthermore, the mixing method in step 5 includes:

[0020] S5.1 The first microprocessor controls the electronically controlled multi-way switch to connect the external power supply and the ultrasonic power controller, so that the ultrasonic generator is started and the mixture of the secondary ball-milled component A and the secondary ball-milled component B is covered with ultrasonic waves with a frequency of 28 kHz and an amplitude of 75-80 μm for a duration of 10-20 seconds for ultrasonic treatment.

[0021] S5.2 The first microprocessor controls the electronically controlled multi-way switch to connect the external power supply and the drive motor, so that the drive motor starts and drives the mixing chamber to roll back and forth for 60-80 seconds to perform tumbling processing.

[0022] S5.3 Repeat the ultrasonic treatment of step S5.1 and the tumbling treatment of step S5.2 10-15 times to complete the mixing treatment.

[0023] Furthermore, before the ultrasonic treatment in step S5.1 is performed, the mixing chamber is first controlled to rotate to a preset fixed position and locked by the driving motor, and then the ultrasonic generating device is controlled to start the ultrasonic treatment.

[0024] Furthermore, the ultrasonic power supply controller includes a rotating electrical connector. The fixed end of the rotating electrical connector is fixed to the bracket and is electrically connected to the external power supply. The rotating end of the rotating electrical connector rotates synchronously with the mixing chamber and is electrically connected to the ultrasonic generating device.

[0025] A shielding disc is fixed to the rotating end along the cross-sectional direction, and the shielding disc has a light-transmitting hole. A laser emitter and a laser sensor are respectively located on either side of the shielding disc at a preset position. The laser emitter is signal-connected to the first microprocessor, and the laser light emitted by the laser emitter passes through the light-transmitting hole and is received by the laser sensor, generating an electrical signal. The laser sensor is signal-connected to the third microprocessor. The third microprocessor is signal-connected to the first microprocessor, the drive motor, and an electronically controlled switch. The electronically controlled switch controls electrical communication between the external power supply and the fixed end.

[0026] Furthermore, the first microprocessor simultaneously sends an ultrasonic processing start instruction to the third microprocessor and the laser transmitter. After receiving the ultrasonic processing start instruction, the laser transmitter starts emitting laser light. After receiving the ultrasonic processing start instruction, the third microprocessor executes the following control steps:

[0027] A. Control the electronic control switch to be disconnected, and at the same time send control current to the drive motor, so that the drive motor drives the mixing chamber to rotate at a low speed.

[0028] B. After receiving the electrical signal from the laser sensor, the drive motor is controlled to lock and the electronic control switch is controlled to connect.

[0029] Furthermore, step S6 also includes step S6.1: subjecting the tablet to microwave treatment to obtain a microwave-treated tablet. In this case, step S7 becomes subjecting the microwave-treated tablet to binder removal treatment and then sintering treatment, and subsequent treatment.

[0030] The microwave treatment method in step S6.1 includes:

[0031] First, the pressed tablets are laid out in layers spaced apart from each other in a processing container.

[0032] Secondly, the tablets are covered with microwaves at a frequency of 5.4-5.6 GHz for a treatment time of 180-200 seconds to obtain the microwave-treated tablets.

[0033] The debinding process in step 7 includes:

[0034] First, the pellets were continuously microwaved with a frequency of 7.8-8.1 GHz and heated to the debinding temperature at a rate of 10°C / min in an air environment.

[0035] Then, turn off the microwave field and maintain the debinding temperature until the debinding is completed.

[0036] The present invention also provides a buzzer, in which the piezoelectric ceramic component is prepared by using the multi-element doped potassium sodium niobate-based piezoelectric ceramic.

[0037] The present invention has the beneficial effect of modifying potassium sodium niobate-based piezoelectric ceramics through multi-element doping to produce a piezoelectric ceramic with a high piezoelectric constant, a high electromechanical coupling coefficient, and a low dielectric loss coefficient. The resulting electroacoustic device, particularly a buzzer, exhibits excellent performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Shown is a schematic structural diagram of the closed mixing device of the present invention;

[0039] Figure 2 Shown is a schematic structural diagram of the power supply controller of the present invention;

[0040] Figure 3 Shown is a schematic structural diagram of the ultrasonic power supply controller of the present invention;

[0041] Figure 4 Shown is a schematic structural diagram of the shading disk of the present invention;

[0042] Figure 5 The figure shows the curve of the buzzer sound pressure versus frequency obtained in Example 6 of the present invention;

[0043] Figure 6 Shown is a scanning electron microscope photograph of the ceramic sheet obtained in Example 1 of the present invention;

[0044] Numbers in the figure: 1. Mixing chamber; 101. Switch door; 102. Tooth groove / tooth belt; 2. Bracket; 3. Driving motor; 301. Driving gear disc; 4. Ultrasonic generating device; 5. First microprocessor; 6. Electric-controlled multi-way switch; 7. Ultrasonic power controller; 701. Rotating electrical connector; 7011. Rotating electrical connector fixed end; 7012. Rotating electrical connector rotating end; 7013. Shielding disc; 7014. Light-transmitting hole; 702. Laser emitter; 703. Laser sensor; 704. Third microprocessor; 705. Electric-controlled switch. DETAILED DESCRIPTION

[0045] The present invention will now be described in further detail with reference to the accompanying drawings. It should be noted that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the present invention.

[0046] The present invention provides a multi-element doped potassium sodium niobate-based piezoelectric ceramic, the chemical formula of which is: (1-x)(K 0.48 Na 0.52 ) 0.965 Li 0.035 (Nb 0.97 Sb 0.03 )O3-x(Bi 0.5 Ag0.5 )ZrO3-yM A O B , wherein 0.01≤x≤0.02, 0.1mol.%≤y≤0.2mol.%. The M A O B It is a composite metal oxide. It should be noted that x in the chemical formula represents (Bi 0.5 Ag 0.5 )ZrO3 and (K 0.48 Na 0.52 ) 0.965 Li 0.035 (Nb 0.97 Sb 0.03 )O3, that is, (Bi 0.5 Ag 0.5 )ZrO3 content is 1-2%, (K 0.48 Na 0.52 ) 0.965 Li 0.035 (Nb 0.97 Sb 0.03 )O3 content is 98-99%, and the sum of the percentages of the two is 100%. y represents the molar concentration of the composite metal oxide, in mol.%.

[0047] It should be noted that within the numerical ranges of 0.01≤x≤0.02 and 0.1mol.%≤y≤0.2mol.% defined in the present invention, any combination can be used to obtain a specific multi-element doped potassium sodium niobate-based piezoelectric ceramic. The present invention does not list them one by one, but this does not mean that the present invention is limited to the combinations in the embodiments or comparative examples.

[0048] The present invention mainly studies the effect of composite metal oxides on the piezoelectric constant d of potassium sodium niobate-based piezoelectric ceramics. 33 , electromechanical coupling coefficient kp, dielectric loss coefficient tgδ, Curie temperature T C Since the raw material properties and preparation environment have a greater impact on potassium sodium niobate-based piezoelectric ceramics, the present invention uses self-made doped potassium sodium niobate-based piezoelectric ceramics as a comparative example.

[0049] The piezoelectric constant d of the present invention 33 The quasi-static tester was used to test the

[0050] The electromechanical coupling coefficient kp and dielectric loss coefficient tgδ of the present invention are obtained by testing using a TH2818 frequency sweeper.

[0051] The Curie temperature T of the present invention C Detected using the test method of GBT 3389.3-2001.

[0052] Example 1

[0053] A multi-element doped potassium sodium niobate-based piezoelectric ceramic, the chemical formula of which is (1-x)(K 0.48 Na 0.52 ) 0.965 Li 0.035 (Nb 0.97 Sb 0.03 )O3-x(Bi 0.5 Ag 0.5 )ZrO3-yM A O B , wherein x = 0.01, y = 0.14 mol.%. M A O B It is a composite oxide of Fe2O3, ZnO and SnO2 in a molar ratio of Fe:Zn:Sn=7:1:2.

[0054] The preparation method of the multi-element doped potassium sodium niobate-based piezoelectric ceramic comprises:

[0055] Step 1: Prepare K2CO3, Na2CO3, Li2CO3, Nb2O5, Sb2O3, Bi2O3, Ag2O, ZrO2, Fe2O3, ZnCO3, and SnO2 according to the chemical formula. K2CO3, Na2CO3, Li2CO3, Nb2O5, Sb2O3, Bi2O3, Ag2O, and ZrO2 are used as component A, and Fe2O3, ZnCO3, and SnO2 are used as component B.

[0056] Step 2: Component A and component B are ball-milled for the first time and dried.

[0057] Step 3: Component A is pre-fired at 850° C. for 5 h to obtain pre-fired component A. Component B is pre-fired at 720° C. for 5 h to obtain pre-fired component B.

[0058] Step 4: Ball mill the pre-calcined component A to a D50 of ≤1 μm and dry it to obtain a secondary ball milled component A. Ball mill the pre-calcined component B to a D50 of ≤0.8 μm and dry it to obtain a secondary ball milled component B.

[0059] Step 5: Place the secondary ball-milled component A and the secondary ball-milled component B into a closed mixing device for mixing, and obtain a mixed component C after the mixing is completed.

[0060] Step 6: After drying the mixed component C, add the adhesive, mix thoroughly, and prepare a tablet.

[0061] Step 7: Debinding the pressed sheet and then sintering it. The sintering temperature is 1080° C. and the sintering time is 7 hours.

[0062] After the sintering treatment in step 8 is completed, the product is naturally cooled to room temperature to obtain the multi-element doped potassium sodium niobate-based piezoelectric ceramic.

[0063] The multi-element doped potassium sodium niobate-based piezoelectric ceramic sheet was prepared by combining the preparation method of the multi-element doped potassium sodium niobate-based piezoelectric ceramic in Example 1 with the conventional ceramic sheet preparation process. The electron microscope scanning photo is shown as follows: Figure 6 As shown, it can be seen that the surface of the ceramic sheet is dense and has no holes, indicating that the ceramic structure has good density.

[0064] Example 2

[0065] The 0.99 (K 0.48 Na 0.52 ) 0.965 Li 0.035 (Nb 0.97 Sb 0.03 )O3-0.01(Bi 0.5 Ag 0.5 )ZrO3-0.1mol.%Fe2O3 piezoelectric ceramics.

[0066] The conventional method is:

[0067] Step 1. The raw materials are mixed, ball-milled into powder, and dried to obtain a mixture.

[0068] Step 2. Pre-calcining the mixture at 850° C. for 5 h to obtain a pre-calcined material.

[0069] Step 3: ball-mill the pre-sintered material for a second time until D50 is less than or equal to 1 micron and dry the pre-sintered material to obtain a second ball-milled material.

[0070] Step 4: Add a binder to the secondary ball mill material, mix thoroughly, and prepare a tablet.

[0071] Step 5: Debinding the pressed sheet and then sintering it at a temperature of 1080° C. for 7 hours.

[0072] After the sintering treatment in step 6 is completed, the product is naturally cooled to room temperature to obtain the multi-element doped potassium sodium niobate-based piezoelectric ceramic.

[0073] The performance test results of Examples 1-2 are shown in the following table:

[0074] Table 1. Test results of Examples 1-2

[0075]

[0076] Based on existing research, the applicant introduced new doping atoms: Li, Sb, and Ag, and obtained a multi-element doped potassium sodium niobate-based piezoelectric ceramic with a high piezoelectric constant, a high electromechanical coupling coefficient, and a low dielectric loss coefficient. Furthermore, the applicant introduced a composite metal oxide system and improved the preparation process, introducing a grouping treatment method (pre-sintering and secondary ball milling) during the preparation process, further improving the piezoelectric constant, electromechanical coupling coefficient, and dielectric loss coefficient of the multi-element doped potassium sodium niobate-based piezoelectric ceramic to a certain extent. Compared with traditional potassium sodium niobate-based piezoelectric ceramics, this multi-element doped potassium sodium niobate-based piezoelectric ceramic has better practical performance and meets the requirements of most usage environments.

[0077] Comparative Example 1

[0078] The remaining steps are the same as those in Example 1, except that in step 3, component A and component B are combined and pre-fired at 850° C. for 5 h.

[0079] Comparative Example 2

[0080] The remaining steps are the same as those in Example 1, except that in step 3, component A and component B are combined and pre-calcined at 720° C. for 5 h.

[0081] The performance test results of Example 1 and Comparative Examples 1-2 are shown in the following table:

[0082] Table 2. Test results of Example 1 and Comparative Examples 1-2

[0083]

[0084] It can be seen that after combining component A and component B and pre-firing them in an environment of 850°C, the performance of the final multi-element doped potassium sodium niobate-based piezoelectric ceramics will decrease, but the decrease is small. The possible reason is that component A begins to partially react during the high-temperature pre-firing stage, and the intervention of the composite oxide at this time will affect the reaction, resulting in an increase in electron vacancies and a decrease in ceramic density in the product obtained by later sintering, which is manifested as a decrease in performance.

[0085] After combining components A and B and pre-firing them at 720°C, the performance of the final multi-element doped potassium sodium niobate-based piezoelectric ceramics will decrease, but the decrease is small. The possible reason is that the pre-firing temperature of 720°C is not sufficient for pre-firing component A, resulting in a decrease and increase in electron vacancies and ceramic density in the product obtained by later sintering, which is manifested as a decrease in performance.

[0086] Comparative Example 3

[0087] The remaining steps are the same as those in Example 1, except that in step 4, component A and component B are combined and ball-milled until D50 ≤ 1 μm.

[0088] Comparative Example 4

[0089] The remaining steps are the same as those in Example 1, except that in step 4, component A and component B are combined and ball-milled to a D50 of ≤ 0.8 μm.

[0090] The performance test results of Example 1 and Comparative Examples 3-4 are shown in the following table:

[0091] Table 3. Test results of Example 1 and Comparative Examples 3-4

[0092]

[0093] It can be seen that the performance of the multi-element doped sodium potassium niobate-based piezoelectric ceramics obtained by simultaneously ball-milling component A and component B to D50≤0.8 micron and ball-milling component A to D50≤1 micron and component B to D50≤0.8 micron of the present invention is not much different from that of the step-by-step treatment. However, the amount of component A used far exceeds that of component B, so the equipment requirements for ball milling to D50≤0.8 micron are higher, the processing time is longer, and the production efficiency and production cost will inevitably increase. While simultaneously ball-milling component A and component B to D50≤1 micron will cause a certain degree of reduction in the performance of the multi-element doped sodium potassium niobate-based piezoelectric ceramics due to the increase in the particle size of component B. Therefore, the method of group ball milling of the present invention not only ensures product performance, but also balances production efficiency and production cost.

[0094] Example 3

[0095] Based on the preparation method of multi-element doped potassium sodium niobate-based piezoelectric ceramics in Example 1, the mixing treatment in step 5 is a mixing treatment method combining ultrasonic treatment and tumbling treatment using a closed mixing device with ultrasonic and tumbling functions. Figure 1 As shown, it includes: a power controller and a sealed hollow mixing chamber 1, wherein the mixing chamber 1 is rotatably mounted on a bracket 2 and is driven to rotate by a driving motor 3;

[0096] The mixing chamber 1 is provided with a closable switch door 101, and an ultrasonic generator 4 is provided inside the mixing chamber 1; a toothed groove / toothed belt 102 is provided on the outer wall of the mixing chamber 1, and the drive motor 3 drives the toothed disc 301 to rotate, and the toothed disc 301 is toothed in engagement with the toothed groove / toothed belt 102;

[0097] The external power supply supplies power to the driving motor 3 and the ultrasonic generating device 4 through the power controller; Figure 2As shown, the power controller includes: an electrically controlled multi-way switch 6, a first microprocessor 5, and an ultrasonic power controller 7; the electrical input interface of the electrically controlled multi-way switch 6 is electrically connected to the external power supply, the control end of the electrically controlled multi-way switch 6 is signal-connected to the first microprocessor 5, one electrical output interface of the electrically controlled multi-way switch 6 is electrically connected to the electrical input interface of the ultrasonic power controller 7, and the other electrical output interface is electrically connected to the electrical input interface of the drive motor 3; the ultrasonic power controller 7 controls the power supply of the ultrasonic generating device 4.

[0098] At this time, the mixing method described in step 5 includes:

[0099] S5.1 The first microprocessor 5 controls the electronically controlled multi-way switch 6 to connect the external power supply and the ultrasonic power controller 7, so that the ultrasonic generator 4 is activated and ultrasonic waves at a frequency of 28 kHz and an amplitude of 78 μm are applied to the mixture of the secondary ball-milled components A and B for a duration of 15 seconds to perform ultrasonic treatment.

[0100] S5.2 The first microprocessor 5 controls the electronically controlled multi-way switch 6 to connect the external power supply and the drive motor 3, so that the drive motor 3 starts and drives the mixing chamber 1 to roll back and forth for 70 seconds to perform the tumbling process; the reciprocating rolling for 70 seconds can be: based on Figure 1 As viewed from the left, mixing chamber 1 rotates clockwise for 30 seconds, brakes for 5 seconds, then rotates counterclockwise for 30 seconds, brakes for 5 seconds.

[0101] S5.3 Repeat the ultrasonic treatment of step S5.1 and the tumbling treatment of step S5.2 12 times to complete the mixing treatment.

[0102] The test results of Example 1 and Example 3 are shown in the following table:

[0103] Table 4. Test results of Example 1 and Example 3

[0104]

[0105] It can be seen that ultrasonic treatment can significantly improve the piezoelectric constant, electromechanical coupling coefficient, and dielectric loss properties of multi-element doped potassium sodium niobate-based piezoelectric ceramics. The possible reasons are: on the one hand, ultrasonic treatment makes the mixing of the components more uniform and sufficient, reducing the ceramic density instability and electrical performance degradation caused by discontinuous phases. On the other hand, the ultrasonic treatment oscillation process may reduce the electron vacancies formed during the pre-sintering process, resulting in a higher density of the treated material after pre-sintering.

[0106] Comparative Example 5

[0107] The remaining steps are the same as those in Example 3, except that 35 kHz ultrasonic waves are used.

[0108] Comparative Example 6

[0109] The remaining steps are the same as those in Example 3, except that 22 kHz ultrasound is used.

[0110] Comparative Example 7

[0111] The remaining steps are the same as those in Example 3, except that ultrasonic waves with an amplitude of 100 μm are used.

[0112] Comparative Example 8

[0113] The remaining steps are the same as those in Example 3, except that ultrasonic waves with an amplitude of 40 μm are used.

[0114] Comparative Example 9

[0115] The remaining steps are the same as those in Example 3, except that: the mixing treatment method described in step 5 includes: maintaining continuous reciprocating rolling while continuously performing ultrasonic treatment, and the treatment time is 1020s.

[0116] The test results of Example 3 and Comparative Examples 5-9 are shown in the following table:

[0117] Table 5. Test results of Example 3 and Comparative Examples 5-9

[0118]

[0119] As shown in Example 3 and Comparative Examples 5-9, the effectiveness of ultrasonic treatment is correlated with the frequency and amplitude of the ultrasonic wave, but the correlation is not linear. Within a specific ultrasonic frequency and amplitude range, the performance of the multi-element-doped potassium sodium niobate-based piezoelectric ceramics of the present invention is significantly improved. Higher ultrasonic frequencies and amplitudes do not significantly improve product performance, but do significantly increase the power consumption of the ultrasonic equipment. Lower ultrasonic frequencies and amplitudes can lead to varying degrees of degradation in product performance. Therefore, the ultrasonic frequencies and amplitudes specified in the present invention are preferred.

[0120] It can be seen from Example 3 and Comparative Example 9 that compared with the segmented treatment method adopted in Example 3, Comparative Example 9 adopts continuous tumbling treatment and ultrasonic treatment. Although the operational complexity is reduced, and the ultrasonic treatment time and tumbling treatment time are longer, the effect of the final product is reduced compared with Example 3. The possible reason is that when the ultrasonic device rolls with the mixing chamber 1, the sound waves generated are also continuously rolling rather than directional fluctuations, which leads to a relatively chaotic ultrasonic field in the mixing chamber 1. On the one hand, the mutual interference between the ultrasonic waves may weaken the effect of the ultrasonic treatment, resulting in a decline in the performance of the final product. On the other hand, energy consumption is significantly improved, and the powder materials to be processed of the present invention are all micron-sized powders close to the nanometer level. When the powder passes through the ultrasonic generating device, it may infiltrate the device in an unquantified manner, resulting in an uncertain missing change in the proportion of the components of the final product, resulting in varying degrees of change in the final performance of the final product (the changes currently observed are mainly manifested as degradation), and the ultrasonic generating device will be damaged.

[0121] Example 4

[0122] Based on the method for preparing multi-element doped potassium sodium niobate-based piezoelectric ceramics in Example 3, before performing the ultrasonic treatment in step S5.1, the mixing chamber 1 is first controlled to rotate to a preset fixed position and locked by the drive motor 3; then the ultrasonic generator 4 is controlled to start the ultrasonic treatment. The specific mechanism and method for implementing the above control include:

[0123] like Figure 3-4 As shown, the ultrasonic power supply controller 7 includes: a rotating electrical connector 701; a fixed end 7011 of the rotating electrical connector 701 is fixed to the bracket 2 and is electrically connected to the external power supply; a rotating end 7012 of the rotating electrical connector 701 rotates synchronously with the mixing chamber 1 and is electrically connected to the ultrasonic generating device 4;

[0124] A shading disc 7013 is fixed on the rotating end 7012 along the cross-sectional direction, and a light-transmitting hole 7014 is opened on the shading disc 7013; a laser emitter 702 and a laser sensor 703 are respectively provided on both sides of the shading disc 7013 at a preset position of the shading disc 7013, the laser emitter 702 is signal-connected to the first microprocessor 5, and the emitted laser can pass through the light-transmitting hole 7014 and be received by the laser sensor 703 to generate an electrical signal; the laser sensor 703 is signal-connected to the third microprocessor 704; the third microprocessor 704 is signal-connected to the first microprocessor 5, the drive motor 3, and the electric control switch 705 respectively; the electric control switch 705 controls the electrical connection between the external power supply and the fixed end 7011.

[0125] The first microprocessor 5 simultaneously sends an ultrasonic processing start instruction to the third microprocessor 704 and the laser emitter 702; after receiving the ultrasonic processing start instruction, the laser emitter 702 starts emitting laser light; after receiving the ultrasonic processing start instruction, the third microprocessor 704 executes the following control steps:

[0126] A. Control the electronic switch 705 to be turned off, and at the same time send a control current to the drive motor 3, so that the drive motor 3 drives the mixing chamber 1 to rotate at a low speed;

[0127] B. After receiving the electrical signal from the laser sensor 703, the drive motor 3 is controlled to be locked, and the electronically controlled switch 705 is controlled to be connected.

[0128] In this embodiment, when ultrasonic treatment is initiated, mixing chamber 1 is first controlled to rotate to a target position, i.e., a position where the laser light emitted by laser emitter 702 can pass through light-transmitting aperture 7014 and be received by laser sensor 703. Then, mixing chamber 1 is locked by driving motor 3 to prevent further rotation. Finally, ultrasonic generator 4 is activated. This ensures that the material to be treated is always within the preset position during each ultrasonic treatment, allowing for accurate, targeted ultrasonic treatment.

[0129] Example 5

[0130] Based on the preparation method of multi-element doped potassium sodium niobate-based piezoelectric ceramics in Example 3, step S6 also includes step S6.1: subjecting the pressed tablet to microwave treatment to obtain a microwave-treated pressed tablet. At this time, step S7 becomes subjecting the microwave-treated pressed tablet to debinding treatment and then sintering treatment, and subsequent treatment.

[0131] The microwave treatment method in step S6.1 includes:

[0132] First, the tablets are laid out in layers spaced apart from each other in a processing container;

[0133] Secondly, the tablets were covered with microwaves at a frequency of 5.5 GHz for 200 seconds to obtain the microwave-treated tablets;

[0134] The debinding process in step 7 includes:

[0135] First, the pellets were continuously microwaved with 8.0 GHz frequency and heated to the debinding temperature at a rate of 10°C / min in an air environment.

[0136] Then, turn off the microwave field and maintain the debinding temperature until the debinding is completed.

[0137] The test results of Example 3 and Example 5 are shown in the following table:

[0138] Table 6. Test results of Example 3 and Example 5

[0139]

[0140] Microwave treatment of the pressed tablets followed by binder removal and sintering significantly impacts the performance of the multi-element-doped sodium potassium niobate-based piezoelectric ceramics of the present invention. This is likely because the pressed tablets obtained through physical pressing contain crystal structure defects. Microwaves allow the non-metallic ions in the pressed tablets to absorb energy and undergo energy migration, promoting a more continuous crystal structure. This significantly reduces these defects, improves the ceramic's density and crystal continuity, and ultimately enhances the performance of the final product.

[0141] In the current development of technology in this field, it is very difficult to increase the electromechanical coupling coefficient kp of KNN piezoelectric ceramics after it exceeds 50%, especially after it reaches 55%. The present invention adds a microwave treatment process to reduce the piezoelectric constant d of multi-element doped potassium sodium niobate-based piezoelectric ceramics. 33 While the electromechanical coupling coefficient kp is significantly improved, it is still maintained at 56.8%, achieving the piezoelectric constant d 33 While the significant improvement is achieved, the electromechanical coupling coefficient kp does not decrease significantly, which is a relatively significant improvement in the technical field of the present invention.

[0142] In addition, the applicant also studied the effect of microwave frequency processing on the performance of multi-element doped potassium sodium niobate-based piezoelectric ceramic products and found that:

[0143] Increasing the microwave frequency will lead to a decrease in the performance of multi-element doped potassium sodium niobate-based piezoelectric ceramics. The reason may be that excessive microwave energy will cause excessive energy flow in the pressed tablet, thereby destroying the crystal structure of the pressed tablet, resulting in an increase in defects in the sintered product, and thus a decrease in the performance of the final product.

[0144] Lowering the microwave frequency will lead to a decrease in the performance of the multi-element doped potassium sodium niobate-based piezoelectric ceramics. The reason may be that the lower microwave energy cannot effectively eliminate the crystal structure defects, thereby failing to improve the performance of the multi-element doped potassium sodium niobate-based piezoelectric ceramics of the present invention to the optimal level.

[0145] At the same time, the present invention involves multiple metal oxides with complex crystal structures. If the doped metal ions cannot adapt to the ceramic crystals, not only will they fail to increase the density of the ceramic, but they will also form a large number of electron holes, crystal structure defects and even discontinuous phases, thereby seriously affecting the performance of multi-element doped potassium sodium niobate-based piezoelectric ceramics. During the debinding and heating process, the crystals in the pressed tablets begin to react with each other due to the heat. At this time, the loaded microwave field:

[0146] (1) This reaction process can be accelerated by providing additional energy.

[0147] (2) The heating process will cause the K, Na, and O ions in the crystal phase to overflow, thereby forming electron holes and crystal structure defects. The electron holes and crystal structure defects formed during the debinding process will cause the defective parts to loosen during the sintering process, forming electron holes and crystal structure defects on a larger scale. At the same time, the metal ions in the composite metal oxide cannot be incorporated into the crystal structure, which will lead to crystal discontinuity and seriously affect the performance of the finished multi-element doped potassium sodium niobate-based piezoelectric ceramics. Microwave treatment can provide energy and oscillation to promote the incorporation of metal ions in the composite metal oxide into the crystal structure and make the crystal continue to tend towards continuity, thereby continuously reducing electron holes and crystal structure defects, and then obtaining dense and crystal-continuous multi-element doped potassium sodium niobate-based piezoelectric ceramics, thereby improving the performance of the product.

[0148] Example 6

[0149] The ceramic diaphragm obtained in Example 5 was polarized, bonded to a copper substrate with an epoxy resin adhesive, and then cured to prepare a potassium sodium niobate-based lead-free piezoelectric buzzer.

[0150] Test the buzzer's sound pressure versus frequency curve, such as Figure 5 As shown, the driving voltage is 12Vp-p, the driving frequency is 4.0kHz, and the sound pressure is 95.5dB when the test distance is 10cm.

[0151] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A multi-element doped potassium sodium niobate-based piezoelectric ceramic, characterized in that: The chemical formula is: (1-x)(K 0.48 Na 0.52 ) 0.965 Li 0.035 (Nb 0.97 Sb 0.03 )O3-x(Bi 0.5 Ag 0.5 )ZrO3-yM A O B , wherein 0.01≤x≤0.02, 0.1mol.%≤y≤0.2mol.%; the M A O B It is a composite of Fe2O3, ZnO, and SnO2; The multi-element doped potassium sodium niobate-based piezoelectric ceramics are prepared by the following method: Step 1: Prepare K2CO3, Na2CO3, Li2CO3, Nb2O5, Sb2O3, Bi2O3, Ag2O, ZrO2, Fe2O3, ZnCO3, and SnO2 according to the chemical formula; and use K2CO3, Na2CO3, Li2CO3, Nb2O5, Sb2O3, Bi2O3, Ag2O, and ZrO2 as component A, and use Fe2O3, ZnCO3, and SnO2 as component B; Step 2: ball milling component A and component B for the first time and drying them; Step 3: Component A is pre-fired at 800-900°C for 4-6 hours to obtain pre-fired component A; component B is pre-fired at 700-750°C for 4-6 hours to obtain pre-fired component B; Step 4: ball-milling the pre-calcined component A to a D50 of ≤1 μm and drying to obtain a secondary ball-milled component A; ball-milling the pre-calcined component B to a D50 of ≤0.8 μm and drying to obtain a secondary ball-milled component B; Step 5: Place the secondary ball-milled component A and the secondary ball-milled component B into a closed mixing device for mixing, and obtain a mixed component C after the mixing is completed; Step 6: After drying the mixed component C, add the adhesive, mix thoroughly, and prepare a tablet; Step 7: Debinding the pressed sheet and then sintering it; the sintering temperature is 1050-1100° C., and the sintering time is 6-7 hours; After the sintering treatment is completed in step 8, the mixture is naturally cooled to room temperature to obtain the multi-element doped potassium sodium niobate-based piezoelectric ceramic; The enclosed mixing device in step 5 comprises: a power controller and an enclosed hollow mixing chamber (1), wherein the mixing chamber (1) is rotatably mounted on a bracket (2) and driven to rotate by a driving motor (3); The mixing chamber (1) is provided with a closable switch door (101), and an ultrasonic generating device (4) is provided inside the mixing chamber (1); a tooth groove / tooth belt (102) is provided on the outer wall of the mixing chamber (1), and the driving motor (3) drives the toothed disc (301) to rotate, and the toothed disc (301) is tooth-engaged with the tooth groove / tooth belt (102); The external power supply supplies power to the driving motor (3) and the ultrasonic generating device (4) through the power controller; the power controller comprises: an electrically controlled multi-way switch (6), a first microprocessor (5), and an ultrasonic power controller (7); an electrical input interface of the electrically controlled multi-way switch (6) is electrically connected to the external power supply, a control end of the electrically controlled multi-way switch (6) is signal-connected to the first microprocessor (5), an electrical output interface of the electrically controlled multi-way switch (6) is electrically connected to an electrical input interface of the ultrasonic power controller (7), and another electrical output interface is electrically connected to an electrical input interface of the driving motor (3); the ultrasonic power controller (7) controls the power supply to the ultrasonic generating device (4); The mixing method in step 5 includes: S5.1 The first microprocessor (5) controls the electric-controlled multi-way switch (6) to connect the external power supply and the ultrasonic power controller (7), so that the ultrasonic generator (4) is activated and the mixture of the secondary ball-milled component A and the secondary ball-milled component B is covered with ultrasonic waves with a frequency of 28 kHz and an amplitude of 75-80 μm for a duration of 10-20 seconds for ultrasonic treatment; S5.2 The first microprocessor (5) controls the electric control multi-way switch (6) to connect the external power supply and the drive motor (3), so that the drive motor (3) starts and drives the mixing chamber (1) to roll back and forth for 60-80 seconds to perform tumbling processing; S5.3 Repeat the ultrasonic treatment of step S5.1 and the tumbling treatment of step S5.2 10-15 times to complete the mixing treatment.

2. The multi-element doped potassium sodium niobate-based piezoelectric ceramic according to claim 1, characterized in that: x=0.01, y=0.14 mol.%; M A O B It is a composite of Fe2O3, ZnO and SnO2 in a molar ratio of Fe:Zn:Sn=7:1:

2.

3. The multi-element doped potassium sodium niobate-based piezoelectric ceramic according to claim 1, characterized in that: Before performing the ultrasonic treatment in step S5.1, the mixing chamber (1) is first controlled to rotate to a preset fixed position and locked by the driving motor (3); then the ultrasonic generating device (4) is controlled to start the ultrasonic treatment.

4. The multi-element doped potassium sodium niobate-based piezoelectric ceramic according to claim 3, characterized in that: The ultrasonic power supply controller (7) comprises: a rotating electrical connector (701); a fixed end (7011) of the rotating electrical connector (701) is fixed to the bracket (2) and is electrically connected to an external power supply; a rotating end (7012) of the rotating electrical connector (701) rotates synchronously with the mixing chamber (1) and is electrically connected to the ultrasonic generating device (4); A shading disc (7013) is fixed on the rotating end (7012) along the cross-sectional direction, and a light-transmitting hole (7014) is opened on the shading disc (7013); a laser emitter (702) and a laser sensor (703) are respectively provided on both sides of the shading disc (7013) at a preset position of the shading disc (7013); the laser emitter (702) is signal-connected to the first microprocessor (5), and the emitted laser can pass through the light-transmitting hole (7014) and be received by the laser sensor (703) to generate an electrical signal; the laser sensor (703) is signal-connected to the third microprocessor (704); the third microprocessor (704) is signal-connected to the first microprocessor (5), the drive motor (3), and the electric control switch (705); the electric control switch (705) controls the electrical connection between the external power supply and the fixed end (7011).

5. The multi-element doped potassium sodium niobate-based piezoelectric ceramic according to claim 4, characterized in that: The first microprocessor (5) simultaneously sends an ultrasonic processing start instruction to the third microprocessor (704) and the laser emitter (702); after receiving the ultrasonic processing start instruction, the laser emitter (702) starts emitting laser light; after receiving the ultrasonic processing start instruction, the third microprocessor (704) executes the following control steps: A. Control the electric control switch (705) to be disconnected, and at the same time send a control current to the drive motor (3), so that the drive motor (3) drives the mixing chamber (1) to rotate at a low speed; B. After receiving the electrical signal from the laser sensor (703), the drive motor (3) is controlled to lock and the electric control switch (705) is controlled to connect.

6. The multi-element doped potassium sodium niobate-based piezoelectric ceramic according to claim 1, characterized in that: Step S6 further includes step S6.1: subjecting the pressed tablet to microwave treatment to obtain a microwave-treated pressed tablet, at which point step S7 becomes subjecting the microwave-treated pressed tablet to binder removal treatment and then sintering treatment, and subsequent treatment; The microwave treatment method in step S6.1 includes: First, the tablets are laid out in layers spaced apart from each other in a processing container; Secondly, the tablet is covered with microwaves at a frequency of 5.4-5.6 GHz for a treatment time of 180-200 seconds to obtain the microwave-treated tablet; The debinding process in step 7 includes: First, the pellets were continuously microwaved with a frequency of 7.8-8.1 GHz and heated to the debinding temperature at a rate of 10°C / min in an air environment. Then, turn off the microwave field and maintain the debinding temperature until the debinding is completed.

7. A buzzer, characterized in that: The piezoelectric ceramic component is prepared by using the multi-element doped potassium sodium niobate-based piezoelectric ceramic as described in any one of claims 1 to 6.

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