Potassium sodium niobate-based lead-free piezoelectric ceramic, preparation method thereof and electronic device

Abstract

The application relates to a potassium-sodium niobate-based lead-free piezoelectric ceramic, the components of the potassium-sodium niobate-based lead-free piezoelectric ceramic are (1-x)K 0.48 Na 0.55 Bi a Nb 0.96 Zr b Sb c O3-a-b-c-CuOx; wherein 0.01<=a<=0.08, 0.02<=b<=0.08, 0.02<=c<=0.08, 0.001<=x<=0.2, x represents the molar fraction of CuO, the application can effectively improve the ceramic oxygen vacancy concentration and enhance the pinning effect of the ceramic ferroelectric domain wall by regulating the proportion of copper oxide, so that a potassium-sodium niobate-based lead-free piezoelectric ceramic with moderate d 33 And high mechanical quality factor Qm is obtained, which is expected to be applied in the field of lead-free medium-power piezoelectric devices. In addition, the process for preparing the potassium-sodium niobate-based lead-free piezoelectric ceramic is simple, the cost is low, and the application has the potential for industrial application.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of functional ceramic materials, in particular to a potassium sodium niobate-based lead-free piezoelectric ceramic, a preparation method thereof and an electronic device. BACKGROUND

[0002] Piezoelectric ceramics can realize the mutual conversion of mechanical energy and electrical energy through piezoelectric effect, and are an important functional material. Based on the unique electromechanical coupling characteristics, piezoelectric ceramic materials are widely used in biomedical, consumer electronics, energy and environment, etc. In the past few decades, lead-based piezoelectric materials represented by lead zirconate titanate (PZT) ceramics have always occupied the main market, but PZT-based ceramics contain a high amount of lead, which does not meet the requirements of green environmental protection and sustainable development. In order to adapt to the trend of lead-free piezoelectric ceramics in the future, it is particularly important to develop environmentally friendly lead-free piezoelectric ceramic materials.

[0003] According to different application fields, piezoelectric ceramics are generally divided into soft piezoelectric ceramics and hard piezoelectric ceramics. Soft piezoelectric materials usually have a high piezoelectric constant (d 33 ), and are widely used in multilayer ceramic actuators, ultrasonic atomization, medical imaging and other fields; hard piezoelectric ceramics have a high mechanical quality factor (Qm), and produce less heat during operation, and are widely used in ultrasonic motors, welding and other high-power electromechanical conversion systems.

[0004] As one of the important indicators for evaluating the piezoelectric properties of piezoelectric ceramic materials, the piezoelectric constant can achieve a high piezoelectric constant (d 33 ) according to the current research progress. For example, d 33 can reach more than 500 pC / N, and the piezoelectric performance can be comparable to that of commercial PZT-based ceramics, and is considered to be one of the most promising alternatives to lead-containing piezoelectric ceramics. However, its mechanical quality factor (Qm) is low, such as less than 40, which limits its application in high-power output devices. SUMMARY

[0005] Therefore, the present application develops a potassium sodium niobate-based lead-free piezoelectric ceramic with moderate piezoelectric constant d 33 and high mechanical quality factor Qm, which is expected to be applied in the field of lead-free medium and high power piezoelectric devices.

[0006] The technical scheme of the present application is as follows:

[0007] A potassium sodium niobate-based lead-free piezoelectric ceramic, the composition of the potassium sodium niobate-based lead-free piezoelectric ceramic comprises

[0008] (1-x)K 0.48 Na 0.55 Bi a Nb0.96 Zr b Sb c O3-xCuO;

[0009] wherein, 0.01≤a≤0.08, 0.02≤b≤0.08, 0.02≤c≤0.08, 0.001≤x≤0.2, x represents the molar fraction of CuO.

[0010] In some embodiments, 0.002≤x≤0.005.

[0011] In some embodiments, the piezoelectric constant of the potassium-sodium niobate-based lead-free piezoelectric ceramic is 300pC / N~360pC / N.

[0012] In some embodiments, the mechanical quality factor of the potassium-sodium niobate-based lead-free piezoelectric ceramic is 100~160.

[0013] The application also provides a preparation method of the potassium-sodium niobate-based lead-free piezoelectric ceramic, comprising the following steps:

[0014] According to (1-x)K 0.48 Na 0.55 Bi a Nb 0.96 Zr b Sb c O3-xCuO, a potassium source, a sodium source, a niobium source, an antimony source, a zirconium source, a bismuth source and copper oxide are prepared;

[0015] The potassium source, the sodium source, the niobium source, the antimony source, the zirconium source and the bismuth source are mixed to prepare a first mixture;

[0016] The first mixture is subjected to first ball milling treatment and pre-sintering treatment to prepare a precursor;

[0017] The precursor is subjected to second ball milling treatment, and the copper oxide is subjected to third ball milling treatment;

[0018] The second mixture is subjected to fourth ball milling treatment, granulation treatment, dry pressing treatment, degassing treatment and re-sintering treatment to prepare a ceramic product;

[0019] The ceramic product is subjected to silver printing and silver polarization treatment.

[0020] In some embodiments, the temperature of the pre-sintering treatment is 750℃~950℃, and the holding time is 3h~9h.

[0021] In some embodiments, the temperature of the re-sintering treatment is 1000℃~1300℃, and the holding time is 2h~6h.

[0022] In some embodiments, the temperature of the silver sintering process is 600-800℃, and the holding time is 20-50min.

[0023] In some embodiments, the temperature of the polarization process is 70-120℃, and the polarization time is 10-30min.

[0024] In some embodiments, the first ball milling process comprises the following steps: using zirconium beads with a diameter of 2-5mm as the ball milling beads to mix with the first mixture, using anhydrous ethanol as the ball milling medium; the mass ratio of the first mixture, the ball milling beads and the anhydrous ethanol is 1:2-5:0.5-2.5, and the first ball milling time is 2-10h.

[0025] In some embodiments, the second ball milling process comprises the following steps: using zirconium beads with a diameter of 2-5mm as the ball milling beads to mix with the precursor, using anhydrous ethanol as the ball milling medium; the mass ratio of the precursor, the ball milling beads and the anhydrous ethanol is 1:2-5:0.5-2.5, and the second ball milling time is 2-10h.

[0026] In some embodiments, the third ball milling process comprises the following steps: using zirconium beads with a diameter of 2-5mm as the ball milling beads to mix with the copper oxide, using anhydrous ethanol as the ball milling medium; the mass ratio of the copper oxide, the ball milling beads and the anhydrous ethanol is 1:2-5:0.5-2.5, and the third ball milling time is 2-10h.

[0027] In some embodiments, the fourth ball milling process comprises the following steps: using zirconium beads with a diameter of 2-5mm as the ball milling beads to mix with the second mixture, using anhydrous ethanol as the ball milling medium; the mass ratio of the second mixture, the ball milling beads and the anhydrous ethanol is 1:2-5:0.5-2.5, and the fourth ball milling time is 5-20h.

[0028] In some embodiments, after the first ball milling process, the second ball milling process, the third ball milling process and the fourth ball milling process, the wet powder slurry after the ball milling process is further subjected to a drying process.

[0029] In some embodiments, the temperature of the drying process is 100-150℃, and the time is 2-6h.

[0030] In some embodiments, the granulation process comprises the following steps:

[0031] The ceramic powder obtained after the fourth ball milling process and the drying process is mixed with a polyvinyl alcohol solution with a mass fraction of 3-10%, and the mass ratio of the ceramic powder and the polyvinyl alcohol solution is (5-20):100.

[0032] An electronic device comprising the potassium sodium niobate-based lead-free piezoelectric ceramic described in any of the above embodiments.

[0033] This invention increases the oxygen vacancy concentration in potassium sodium niobate-based ceramics by controlling the doping amount of the hard dopant copper oxide, thereby enhancing the domain wall pinning effect and inhibiting domain wall movement. This achieves hard control of the potassium sodium niobate-based ceramics and yields ceramics with a suitable piezoelectric constant d. 33 Potassium sodium niobate-based lead-free piezoelectric ceramics with high mechanical quality factor (Qm) are expected to find applications in the field of lead-free medium-power piezoelectric devices.

[0034] The preparation process of this invention is simple, without the use of special atmosphere sintering or hot pressing sintering, and the process is easy and low-cost, making it potential for industrial application. Attached Figure Description

[0035] Figure 1 X-ray diffraction pattern of the KNN-based ceramic prepared in Example 3;

[0036] Figure 2 The dielectric temperature spectrum of the KNN-based ceramic prepared in Example 3 from 25°C to 400°C. Detailed Implementation

[0037] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The terms “first” and “second” are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0039] The words "preferably," "more preferably," "most preferably," and the like, in the present invention, mean that in certain situations, embodiments of the invention can provide certain benefits. However, other embodiments can also be preferred under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude those other embodiments from the scope of the present invention. That is, in the present invention, "preferably," "more preferably," "most preferably," and the like, are merely used to describe a more preferred implementation or embodiment, but do not constitute a limitation as to the scope of the present invention. Similarly, in the present invention, "further," "even further," "especially," and the like, are used to describe a purpose and are not used to limit the scope of the present invention.

[0040] In the present invention, "at least one" means one or more, such as one, two, and more than two. "Plural" or "several" means at least two, such as two, three, or the like, and "multiple layers" means at least two layers, such as two, three, or the like, unless otherwise specifically indicated. In the description of the present invention, "several" means at least one, such as one, two, or the like, unless otherwise specifically indicated.

[0041] When a numerical range is disclosed herein, such range is inclusive of the minimum and maximum values, and of each discrete value or sub-range between the minimum and maximum values. Further, when a range is provided, it is understood that the range is inclusive of the minimum and maximum values, and of each discrete integer within the range. Also, when a plurality of ranges is provided, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein are to be understood to be inclusive of any and all sub-ranges subsumed therein.

[0042] Unless specifically indicated otherwise, all steps of the present invention can be performed in sequence or randomly. For example, the method comprising steps (a) and (b) means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method comprising step (c) means that step (c) can be added to the method in any sequence, for example, the method can comprise steps (a), (b), and (c), or steps (a), (c), and (b), or steps (c), (a), and (b), etc. Unless otherwise mentioned, the singular form of a term can include the plural form and should not be construed as having a quantity of one.

[0043] In the present invention, "comprise", "include", "contain", "have", "possess", or other variants thereof are intended to be open-ended transitional terms that do not exclude additional unrecited elements or steps. The term "comprising" means that the compositions and methods / processes of the present invention can include, consist essentially of and / or consist of the essential elements and limitations described herein, as well as any additional or optional ingredients, components, steps or limitations described herein.

[0044] In the present invention, the terms "efficacy", "performance", "effect", "efficiency" are not distinguished.

[0045] The weight of the related components mentioned in the embodiment description of the present invention can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of each component. Therefore, as long as the content of the related components in the embodiment description of the present invention is enlarged or reduced in proportion, it is within the scope disclosed in the embodiment description of the present invention. Specifically, the weight described in the embodiment description of the present invention can be μg, mg, g, kg, etc. mass units commonly known in the chemical industry.

[0046] "piezoelectric constant d 33 " is one of the most commonly used important parameters to characterize the performance of piezoelectric materials. Generally, the higher the piezoelectric constant of ceramic, the better the piezoelectric performance. The first number in the subscript indicates the direction of the electric field, and the second number indicates the direction of stress or strain. "33" means that the polarization direction is the same as the force direction when measuring.

[0047] "Mechanical quality factor Qm" is also an important parameter for measuring piezoelectric ceramics, which represents the degree of energy consumption inside the material during vibration conversion. The larger the mechanical quality factor, the smaller the energy loss, and the easier it is to work under large voltage, large current and high vibration speed.

[0048] Potassium sodium niobate-based (referred to as KNN-based) piezoelectric ceramics can achieve a high piezoelectric constant (d 33 ), such as d 33 above 500 pC / N, which is comparable to commercial PZT-based ceramics in terms of piezoelectric performance, and is considered one of the most promising alternatives to lead-containing piezoelectric ceramics. For example, researchers measured the d 33 of a potassium sodium niobate-based lead-free piezoelectric ceramic after doping modification to be more than 510 pC / N. However, the mechanical quality factor (Qm) of potassium sodium niobate-based lead-free piezoelectric ceramics is low, such as a potassium sodium niobate-based lead-free piezoelectric ceramic with a composition gradient prepared by tape casting has a d 33 as high as 340 pC / N, but Qm is only 39. The Qm and d 33The mutual restraint relationship makes it difficult to effectively improve the high-power output of KNN-based ceramics. Therefore, how to coordinately improve the mechanical quality factor Qm and the piezoelectric constant d 33 of lead-free piezoelectric ceramics is an important challenge for piezoelectric ceramics to face medium and high-power practical applications.

[0049] To solve the above problems, the application provides a potassium-sodium niobate-based lead-free piezoelectric ceramic, and components of the potassium-sodium niobate-based lead-free piezoelectric ceramic are (1-x)K 0.48 Na 0.55 Bi a Nb 0.96 Zr b Sb c O3-xCuO.

[0050] In the formula, 0.01<=a<=0.08, 0.02<=b<=0.08, 0.02<=c<=0.08, 0.001<=x<=0.2, and x represents the molar fraction of CuO.

[0051] The application improves the oxygen vacancy concentration of the potassium-sodium niobate-based ceramic by regulating the proportion of the hard dopant copper oxide, enhances the pinning effect of the domain wall, and prepares the hard potassium-sodium niobate-based lead-free piezoelectric ceramic which can be applied to medium-power piezoelectric devices such as atomizing sheets.

[0052] In some examples, 0.002<=x<=0.005.

[0053] In some examples, the piezoelectric constant of the potassium-sodium niobate-based lead-free piezoelectric ceramic is 300pC / N-360pC / N.

[0054] In some examples, the mechanical quality factor of the potassium-sodium niobate-based lead-free piezoelectric ceramic is 100-160.

[0055] The copper oxide in the application plays a role of hard doping, improves the oxygen vacancy concentration by doping of the copper oxide, enhances the pinning effect of the domain wall, suppresses the domain wall motion, realizes the hard regulation of the potassium-sodium niobate-based ceramic, and improves the mechanical quality factor Qm of the ceramic without greatly reducing the piezoelectric constant d 33 .

[0056] In addition, the copper oxide also has the effect of reducing the sintering temperature, assists the ceramic sintering in the form of liquid phase at high temperature, can effectively improve the sintering property of the ceramic, reduce the sintering temperature of the ceramic, improve the density of the ceramic, and enhance the piezoelectric performance of the ceramic.

[0057] The application further provides a preparation method of the potassium-sodium niobate-based lead-free piezoelectric ceramic, including the following steps:

[0058] According to (1-x)K 0.48 Na0.55 Bi a Nb 0.96 Zr b Sb c O3-xCuO is prepared from a potassium source, a sodium source, a niobium source, an antimony source, a zirconium source, a bismuth source and copper oxide;

[0059] mixing the potassium source, the sodium source, the niobium source, the antimony source, the zirconium source and the bismuth source to prepare a first mixture;

[0060] performing first ball milling and pre-sintering on the first mixture to prepare a precursor;

[0061] respectively performing second ball milling on the precursor and third ball milling on copper oxide;

[0062] mixing the products obtained by the second ball milling and the third ball milling to prepare a second mixture;

[0063] performing fourth ball milling, granulation, dry pressing, degassing and re-sintering on the second mixture to prepare a ceramic product;

[0064] performing silver printing and polarization on the ceramic product.

[0065] In some examples, the potassium source, the sodium source, the niobium source, the antimony source, the zirconium source and the bismuth source are at least one of oxides, carbonates and bicarbonates.

[0066] Preferably, the potassium source is potassium carbonate, the sodium source is sodium carbonate, the niobium source is niobium pentoxide, the antimony source is antimony trioxide, the zirconium source is zirconium oxide and the bismuth source is bismuth oxide.

[0067] In some examples, when the potassium source is potassium carbonate and the sodium source is sodium carbonate, the method further comprises a step of drying the potassium carbonate and the sodium carbonate before weighing the raw materials. Specifically, the raw materials are placed in an oven for drying at 150-200℃ for 2-5h.

[0068] In some examples, the first ball milling comprises the following steps: mixing the first mixture with zirconium beads with a diameter of 2-5mm as ball milling beads and anhydrous ethanol as ball milling medium; the mass ratio of the first mixture, the ball milling beads and the anhydrous ethanol is 1:2-5:0.5-2.5, and the first ball milling time is 2-10h.

[0069] Preferably, the mass ratio of the first mixture, the ball milling beads and the anhydrous ethanol is 1:3-4:1-2.

[0070] In some examples, the rotation speed of the first ball milling is 200-500rpm.

[0071] It can be understood that the rotation speed of the first ball milling treatment includes but is not limited to 200 rpm, 300 rpm, 400 rpm, 500 rpm. Preferably, the rotation speed of the first ball milling treatment is 300 rpm ~ 400 rpm.

[0072] In some examples, the first ball milling treatment further includes a first drying treatment.

[0073] In some examples, the temperature of the first drying treatment is 100℃ ~ 150℃, and the time is 2h ~ 6h.

[0074] It can be understood that the temperature of the first drying treatment includes but is not limited to 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, and the time includes but is not limited to 2h, 3h, 4h, 5h, 6h. Preferably, the temperature of the first drying treatment is 150℃, and the time is 4h.

[0075] In some examples, the temperature of the pre-sintering treatment is 750℃ ~ 950℃, and the holding time is 3h ~ 9h.

[0076] It can be understood that the temperature of the pre-sintering treatment includes but is not limited to 750℃, 780℃, 800℃, 820℃, 850℃, 860℃, 880℃, 900℃, 920℃, 950℃, and the holding time includes but is not limited to 3h, 4h, 5h, 6h, 7h, 8h, 9h; preferably, the temperature of the pre-sintering treatment is 900℃, and the holding time is 8h.

[0077] Specifically, the composition of the precursor obtained by the pre-sintering treatment of the present application is K 0.48 Na 0.55 Bi a Nb 0.96 Zr b Sb c O3.

[0078] In some examples, the second ball milling treatment includes the following steps: using anhydrous ethanol as a ball milling medium, and mixing the precursor with zirconium beads with a diameter of 2mm ~ 5mm as ball milling beads; the mass ratio of the precursor, the ball milling beads and the anhydrous ethanol is 1:2 ~ 5:0.5 ~ 2.5, and the second ball milling time is 2h ~ 10h.

[0079] Preferably, the mass ratio of the precursor, the ball milling beads and the anhydrous ethanol is 1:3 ~ 4:1 ~ 2.

[0080] In some examples, the rotation speed of the second ball milling treatment is 200rpm ~ 500rpm.

[0081] It can be understood that the rotation speed of the second ball milling treatment includes but is not limited to 200 rpm, 300 rpm, 400 rpm, 500 rpm. Preferably, the rotation speed of the second ball milling treatment is 300 rpm ~ 400 rpm.

[0082] In some examples, the second ball milling treatment is further followed by a second drying treatment.

[0083] In some examples, the temperature of the second drying treatment is 100℃ ~ 150℃, and the time is 2h ~ 6h.

[0084] In some examples, the third ball milling treatment comprises the following steps: using anhydrous ethanol as a ball milling medium, using zirconium beads with a diameter of 2mm ~ 5mm as ball milling beads mixed with copper oxide; the mass ratio of the copper oxide, the ball milling beads and the anhydrous ethanol is 1:2 ~ 5:0.5 ~ 2.5, and the third ball milling time is 2h ~ 10h.

[0085] Preferably, the mass ratio of the copper oxide, the ball milling beads and the anhydrous ethanol is 1:3 ~ 4:1 ~ 2.

[0086] In some examples, the rotation speed of the third ball milling treatment is 200rpm ~ 500rpm.

[0087] It can be understood that the rotation speed of the third ball milling treatment includes but is not limited to 200 rpm, 300 rpm, 400 rpm, 500 rpm. Preferably, the rotation speed of the third ball milling treatment is 300 rpm ~ 400 rpm.

[0088] In some examples, the third ball milling treatment is further followed by a third drying treatment.

[0089] In some examples, the temperature of the third drying treatment is 100℃ ~ 150℃, and the time is 2h ~ 6h.

[0090] In some examples, the fourth ball milling treatment comprises the following steps: using anhydrous ethanol as a ball milling medium, using zirconium beads with a diameter of 2mm ~ 5mm as ball milling beads mixed with the second mixture; the mass ratio of the second mixture, the ball milling beads and the anhydrous ethanol is 1:2 ~ 5:0.5 ~ 2.5, and the fourth ball milling time is 5h ~ 20h.

[0091] Preferably, the mass ratio of the second mixture, the ball milling beads and the anhydrous ethanol is 1:3 ~ 4:1 ~ 2.

[0092] In some examples, the rotation speed of the fourth ball milling treatment is 200rpm ~ 500rpm.

[0093] It can be understood that the rotation speed of the fourth ball milling treatment includes but is not limited to 200 rpm, 300 rpm, 400 rpm, 500 rpm. Preferably, the rotation speed of the fourth ball milling treatment is 300 rpm ~ 400 rpm.

[0094] In some examples, the fourth ball milling treatment is further followed by a fourth drying treatment.

[0095] In some examples, the temperature of the fourth drying treatment is 100℃ ~ 150℃, and the time is 2h ~ 6h.

[0096] In some examples, the average particle size of the wet powder slurry obtained by the fourth ball milling treatment is 0.6μm ~ 1.0μm.

[0097] It can be understood that the average particle size of the wet powder slurry includes but is not limited to 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1.0μm; preferably, the average particle size of the wet powder slurry is 0.6μm ~ 0.8μm.

[0098] In some examples, the ball milling treatment of the present application adopts a planetary ball mill.

[0099] It can be understood that in other embodiments, other ball mills can also be used for ball milling.

[0100] In some examples, the granulation treatment includes the following steps:

[0101] The ceramic powder obtained after the fourth ball milling treatment and drying treatment is mixed with a polyvinyl alcohol solution with a mass fraction of 3% ~ 10%, and the mass ratio of the ceramic powder to the polyvinyl alcohol solution is (5 ~ 20): 100.

[0102] In some examples, the mold specification of the dry pressing treatment is Φ10mm, the dry pressing pressure is 150MPa, and the pressure holding time is 25s ~ 35s.

[0103] In some examples, the temperature of the glue removal treatment is 600℃ ~ 700℃, and the holding time is 1.5h ~ 3h.

[0104] Preferably, the temperature of the glue removal treatment is 600℃, and the holding time is 2h.

[0105] In some examples, the step of glue removal treatment is carried out in a tube furnace.

[0106] It can be understood that in other embodiments, other heat processing devices can also be used for glue removal.

[0107] In some examples, the temperature of the re-sintering treatment is 1000℃ ~ 1300℃, and the holding time is 2h ~ 6h.

[0108] It can be understood that the re-sintering temperature includes but is not limited to 1000℃, 1050℃, 1100℃, 1180℃, 1200℃, 1250℃, 1300℃; preferably, the re-sintering temperature is 1180℃. The holding time includes but is not limited to 2h, 3h, 4h, 5h, 6h; preferably, the holding time is 5h.

[0109] In some examples, the sintering step of the present application is carried out in a muffle furnace; it can be understood that in other embodiments, other heat processing devices can also be used for sintering.

[0110] In some examples, the temperature of the silver burning treatment is 600℃~800℃, and the holding time is 20min~50min.

[0111] It can be understood that the temperature of the silver burning treatment includes but is not limited to 600℃, 650℃, 700℃, 750℃, 800℃; preferably, the temperature of the silver burning treatment is 700℃~800℃, and the holding time includes but is not limited to 20min, 25min, 30min, 35min, 40min, 50min; preferably, the holding time is 30min~40min.

[0112] In some examples, the temperature of the polarization treatment is 70℃~120℃, and the polarization time is 10min~30min.

[0113] It can be understood that the temperature of the polarization treatment includes but is not limited to 70℃, 75℃, 80℃, 90℃, 100℃, 110℃, 120℃; preferably, the temperature of the polarization treatment is 90℃~120℃. The polarization time includes but is not limited to 10min, 15min, 20min, 25min, 30min; preferably, the polarization time is 20min.

[0114] The industrial raw materials used in the above-mentioned method for preparing the potassium-sodium niobate-based piezoelectric ceramic are non-toxic, harmless and environmentally friendly; and the preparation method is simple, without using special atmosphere sintering or hot-pressing sintering, etc., has small process difficulty, low cost and potential for industrial application.

[0115] The present application also provides an electronic device comprising the potassium-sodium niobate-based piezoelectric ceramic according to any one of the above-mentioned embodiments.

[0116] The electronic device according to the present application comprises the above-mentioned potassium-sodium niobate-based piezoelectric ceramic, which has a moderate piezoelectric constant d 33And high mechanical quality factor Qm, can be applied in the middle power piezoelectric device such as piezoelectric buzzer, high frequency ceramic resonator, high frequency filter, has great significance for the future piezoelectric ceramic in the process of replacing lead-based hard piezoelectric ceramic. Specific embodiments

[0117] The following detailed description is made in conjunction with specific embodiments. The following embodiments, unless specifically stated otherwise, do not include other components in addition to unavoidable impurities. In the embodiments, reagents and instruments are used as commonly selected in the art unless specifically stated. The experimental methods not specified in the embodiments are carried out according to the conventional conditions, such as the conditions described in the literature, books or the methods recommended by the manufacturer.

[0118] In the following examples of the present application, the raw materials used include potassium carbonate, sodium carbonate, niobium pentoxide, antimony trioxide, zirconium oxide, bismuth oxide, and copper oxide, all of which are analytical pure.

[0119] Polyvinyl alcohol: purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd., analytical pure.

[0120] Other organic reagents are all conventional analytical pure reagents.

[0121] Example 1

[0122] A potassium sodium niobate-based lead-free piezoelectric ceramic is prepared, and the components of the piezoelectric ceramic are (1-x) K 0.48 Na 0.55 Bi a Nb 0.96 Zr b Sb c O3-xCuO, a=0.022, b=0.038, c=0.041, x=0.002.

[0123] (1) batching: potassium carbonate and sodium carbonate are placed in an oven at 150°C and dried for 4h to remove water, and the components are weighed according to the chemical formula K 0.48 Na 0.55 Bi 0.022 Nb 0.96 Zr 0.038 Sb 0.041 O3, potassium carbonate, sodium carbonate, niobium pentoxide, antimony trioxide, zirconium oxide, and bismuth oxide are weighed according to the chemical formula.

[0124] (2) first ball milling: the weighed raw materials are placed in a ball milling tank, anhydrous ethanol is used as the ball milling medium, and zirconium beads with a diameter of 5mm are used as the ball milling beads, under the conditions of a mass ratio of raw materials, ball milling beads and anhydrous ethanol of 1:3.5:1.5, a planetary ball mill is used for first ball milling at a speed of 350rpm for 5h, a first wet powder slurry is obtained, and the first wet powder slurry is dried to obtain a dry powder mixture, the drying conditions are: temperature of 150°C, time of 4h.

[0125] (3) Pre-sintering: the dry powder mixture obtained in step (2) is loaded into a crucible and compacted, the crucible cover is covered, and the pre-sintering is sent to a muffle furnace, the pre-sintering temperature is 900℃, the holding time is 8h, and the pre-synthesized powder K is prepared 0.48 Na 0.55 Bi a Nb 0.96 Zr b Sb c O3, abbreviated as KNBNZrSb.

[0126] (4) Second ball milling: the pre-synthesized powder obtained in step (3) is ball milled, the ball milling conditions are: anhydrous ethanol is used as the ball milling medium, zirconium beads with a diameter of 2mm are used as the ball milling beads, the mass ratio of raw materials, ball milling beads and anhydrous ethanol is 1:3.5:1.5, the planetary ball mill is used for second ball milling at a speed of 350 rpm for 5h, and drying is performed, the drying conditions are: temperature is 150℃, time is 4h.

[0127] (5) Third ball milling: copper oxide is third ball milled, the ball milling conditions are consistent with step (4), and drying is performed after ball milling, the drying conditions are: temperature is 150℃, time is 4h.

[0128] (6) Fourth ball milling: the pre-synthesized powder ball milled and dried in step (4) and the copper oxide ball milled and dried in step (5) are weighed and mixed according to the stoichiometric ratio, and fourth ball milling is performed, the ball milling conditions are consistent with step (4). The average particle size of the fourth wet powder slurry obtained after the fourth ball milling is 0.6μm.

[0129] (7) Granulation and dry pressing: the fourth wet powder slurry is dried at 150℃, 8% PVA solution is added, and the powder is ground to form granules, obtaining a powder with uniform particles, and a Φ10mm mold is used for dry pressing into a ceramic green body under a dry pressing pressure of 150Mpa.

[0130] (8) Glue removal and sintering: the ceramic green body of step (7) is subjected to glue removal, the glue removal treatment temperature is 600℃, the holding time is 2h, and after the glue is removed, it is sent to a muffle furnace for sintering, the sintering temperature is 1180℃, and the holding time is 5h, and the ceramic product is prepared.

[0131] (9) Silver printing and polarization: the sintered ceramic is ground, then silver is printed and burned, the silver burning temperature is 780℃, and the holding time is 35min. Finally, the ceramic sheet is subjected to polarization treatment, the polarization electric field is 3kV / mm, the polarization temperature is 120℃, and the polarization time is 20min.

[0132] (10) Test: the polarized ceramic sheet is placed for one day, and the electrical properties of the ceramic sheet are tested.

[0133] Example 2

[0134] A lead-free piezoelectric ceramic based on potassium sodium niobate was prepared, the composition of which was (1-x) K 0.48 Na 0.55 Bi a Nb 0.96 Zr b Sb c O3-xCuO, a = 0.022, b = 0.038, c = 0.041, x = 0.003, under substantially the same conditions as in Example 1, except that in this example x = 0.003.

[0135] Example 3

[0136] A lead-free piezoelectric ceramic based on potassium sodium niobate was prepared, the composition of which was (1-x) K 0.48 Na 0.55 Bi a Nb 0.96 Zr b Sb c O3-xCuO, a = 0.022, b = 0.038, c = 0.041, x = 0.005, under substantially the same conditions as in Example 1, except that in this example x = 0.005.

[0137] Example 4

[0138] A lead-free piezoelectric ceramic based on potassium sodium niobate was prepared, the composition of which was (1-x) K 0.48 Na 0.55 Bi a Nb 0.96 Zr b Sb c O3-xCuO, a = 0.022, b = 0.038, c = 0.041, x = 0.01, under substantially the same conditions as in Example 1, except that in this example x = 0.01.

[0139] Comparative Example 1

[0140] A lead-free piezoelectric ceramic based on potassium sodium niobate was prepared, the composition of which was (1-x) K 0.48 Na 0.55 Bi a Nb 0.96 Zr b Sb c O3-xCuO, a = 0.022, b = 0.038, c = 0.041, x = 0, under substantially the same conditions as in Example 1, except that in this example x = 0.

[0141] Comparative Example 2

[0142] A potassium sodium niobate based lead-free piezoelectric ceramic was prepared with the composition of 0.995K 0.48 Na 0.55 Bi a Nb 0.96 Zr b O3-0.005CuO, a = 0.022, b = 0.038, c = 0.041, with the same preparation conditions as Example 3 except that the first ball milling step was performed with copper oxide mixed with the raw materials of potassium carbonate, sodium carbonate, niobium pentoxide, antimony trioxide, zirconium oxide, and bismuth oxide.

[0143] Comparative Example 3

[0144] A potassium sodium niobate based lead-free piezoelectric ceramic was prepared with the composition of 0.995K 0.48 Na 0.55 Nb 0.96 Zr b Sb c O3-0.005CuO, b = 0.038, c = 0.041, with the same preparation conditions as Example 3 except that the first ball milling step was performed with copper oxide mixed with the raw materials of potassium carbonate, sodium carbonate, niobium pentoxide, antimony trioxide, zirconium oxide, and bismuth oxide.

[0145] Comparative Example 4

[0146] A potassium sodium niobate based lead-free piezoelectric ceramic was prepared with the composition of 0.995K 0.48 Na 0.55 Bi a Nb 0.96 Zr b Sb c O3-0.005CuO, a = 0.022, b = 0.038, c = 0.041, with the same preparation conditions as Example 3 except that the first ball milling step was performed with copper oxide mixed with the raw materials of potassium carbonate, sodium carbonate, niobium pentoxide, antimony trioxide, zirconium oxide, and bismuth oxide.

[0147] Comparative Example 5

[0148] A potassium sodium niobate based lead-free piezoelectric ceramic was prepared with the composition of 0.995K 0.48 Na 0.55 Bi a Nb 0.96 Zr b Sb c O3-0.005CuO, a = 0.022, b = 0.038, c = 0.041, with the same preparation conditions as Example 3 except that the first ball milling step was performed with copper oxide mixed with the raw materials of potassium carbonate, sodium carbonate, niobium pentoxide, antimony trioxide, zirconium oxide, and bismuth oxide.

[0149] Test:

[0150] The structure and performance of the ceramic products prepared in the above examples were tested, and the results are shown in Table 1 and Figures 1-2 Table 1.

[0151] Figure 1 The 0.995K 0.48 Na 0.55 Bi a Nb 0.96 Zr b Sb c O3-0.005CuO ceramic prepared in Example 3 was subjected to XRD characterization, and the spectrum is shown in Figure 1 It can be found that the ceramic is of pure ABO3 structure, and no second impurity phase exists, and the surface copper oxide is uniformly doped into the KNN-based crystal lattice.

[0152] Figure 2 The dielectric temperature spectrum of the 0.995K 0.48 Na 0.55 Bi a Nb 0.96 Zr b Sb c O3-0.005CuO ceramic prepared in Example 3 is shown, from which it can be confirmed that the Curie temperature Tc of the ceramic is about 244℃.

[0153] Since the sodium element is easy to volatilize to produce defects and vacancies during the high-temperature sintering process of the KNN-based ceramic, the composition design deviates, and the performance of the ceramic is reduced. The present application avoids this problem by introducing a slight excess of sodium source, which can fully develop the performance potential of the formula, so that the piezoelectric ceramic of the present application has a high Curie temperature.

[0154] Table 1 is the piezoelectric constant d 33 and mechanical quality factor Qm of the ceramic product wafer prepared in each example and the comparative example.

[0155] The test method of the piezoelectric constant d 33 of the present application refers to GB / T 3389.2-1982.

[0156] The test method of the mechanical quality factor Qm of the present application refers to GB / T 2414.1-1998.

[0157] Table 1

[0158]

[0159] From Table 1, it can be seen that when 0.002≤x≤0.005, as the content of doped copper oxide increases, the piezoelectric constant d 33The mechanical quality factor Qm gradually increases, but if the doping amount of copper oxide is continuously increased, the mechanical quality factor Qm does not continuously increase when x=0.01, but decreases, because excessive copper oxide does not completely dope into the ceramic crystal lattice, and part of the copper oxide is precipitated in the form of a second phase at the grain boundary to form defects, which affects the flipping of the ceramic electric dipole, and further affects the performance of the ceramic. At the same time, excessive copper oxide also affects the microstructure of the ceramic, causing the density of the ceramic to decrease.

[0160] In the present application, preferably x=0.005 is the optimal stoichiometric ratio of the chemical formula of the system, and the potassium sodium niobate-based lead-free piezoelectric ceramic with moderate piezoelectric constant d 33 and high mechanical quality factor Qm can be obtained.

[0161] It can be seen from the comparison of Example 3 and Comparative Examples 2 and 3 that the lack of Sb and Bi in the components greatly affects the piezoelectric performance. It can be seen from the comparison of Example 3 and Comparative Examples 4 and 5 that a suitable preparation process is also a key to the excellent performance of the present application. The process of mixing copper oxide with potassium carbonate, sodium carbonate and other raw materials together for ball milling in Comparative Example 4 and the process of directly mixing the pre-synthesized powder KNBNZrSb and CuO for ball milling in Comparative Example 5 will affect the performance of the piezoelectric ceramic.

[0162] The present application can effectively reduce the uneven distribution of components caused by the adsorption of large particles to form clusters by preferentially pre-synthesizing K 0.48 Na 0.55 Bi a Nb 0.96 Zr b Sb c O3 powder, then respectively ball milling the pre-synthesized powder and copper oxide to reduce the fineness, mixing the ball-milled pre-synthesized powder and copper oxide, and then ball milling again.

[0163] The technical features of the above-described embodiments can be combined in any manner, and to make the description concise, all possible combinations of the technical features in the above-described embodiments are not described, but as long as the combinations of the technical features do not exist contradictions, they should be considered as the scope of the present application.

[0164] The above embodiments only express several implementation manners of the present application, the description is more specific and detailed, but cannot be understood as the limitation of the patent scope of the present application. It should be pointed out that for ordinary skilled in the art, several modifications and improvements can be made without departing from the concept of the present application, which are all within the protection scope of the present application. It should be understood that the technical solutions obtained by logical analysis, reasoning or limited experiments on the basis of the technical solutions provided by the present application are all within the protection scope of the appended claims of the present application. Therefore, the protection scope of the present application patent should be subject to the appended claims, and the description and drawings can be used to explain the content of the claims.

Claims

1. A potassium sodium niobate-based lead-free piezoelectric ceramic, characterized by, The composition of the potassium sodium niobate-based lead-free piezoelectric ceramic is (1-x)K 0.48 Na 0.55 Bi a Nb 0.96 Zr b Sb c O3-xCuO; Wherein, 0.01≤a≤0.08, 0.02≤b≤0.08, 0.02≤c≤0.08, 0.002≤x≤0.005, x represents the mole fraction of CuO; The preparation method of the potassium-sodium niobate-based lead-free piezoelectric ceramic comprises the following steps: According to (1-x)K 0.48 Na 0.55 Bi a Nb 0.96 Zr b Sb c O3-xCuO is used as a potassium source, a sodium source, a niobium source, an antimony source, a zirconium source, a bismuth source, and copper oxide. Mixing the potassium source, the sodium source, the niobium source, the antimony source, the zirconium source and the bismuth source to prepare a first mixture; Performing first ball milling treatment and pre-sintering treatment on the first mixture to prepare a precursor; Respectively performing second ball milling treatment on the precursor and third ball milling treatment on copper oxide; Mixing the products obtained through the second ball milling treatment and the third ball milling treatment to prepare a second mixture; Performing fourth ball milling treatment, granulation treatment, dry pressing treatment, degassing treatment and re-sintering treatment on the second mixture to prepare a ceramic product; Performing silver printing and silver burning treatment and polarization treatment on the ceramic product.

2. The potassium sodium niobate-based lead-free piezoelectric ceramic according to claim 1, characterized by, Satisfy one or more of the following (1)-(2): (1) the piezoelectric constant of the potassium-sodium niobate-based lead-free piezoelectric ceramic is 300 pC / N-360 pC / N; (2) the mechanical quality factor of the potassium-sodium niobate-based lead-free piezoelectric ceramic is 100-160.

3. A method for producing the potassium sodium niobate-based lead-free piezoelectric ceramic according to any one of claims 1 to 2, characterized by, Comprise the following steps: According to (1-x)K 0.48 Na 0.55 Bi a Nb 0.96 Zr b Sb c O3-xCuO sources, potassium, sodium, niobium, antimony, zirconium, bismuth and copper oxide; Mixing the potassium source, the sodium source, the niobium source, the antimony source, the zirconium source and the bismuth source to prepare a first mixture; Performing first ball milling treatment and pre-sintering treatment on the first mixture to prepare a precursor; Respectively performing second ball milling treatment on the precursor and third ball milling treatment on copper oxide; Mixing the products obtained through the second ball milling treatment and the third ball milling treatment to prepare a second mixture; Performing fourth ball milling treatment, granulation treatment, dry pressing treatment, degassing treatment and re-sintering treatment on the second mixture to prepare a ceramic product; Performing silver printing and silver burning treatment and polarization treatment on the ceramic product.

4. The method for producing a potassium sodium niobate-based lead-free piezoelectric ceramic according to claim 3, characterized by, Satisfy one or more of the following (1)-(4) conditions: (1) the temperature of the pre-sintering treatment is 750 DEG C-950 DEG C, and the holding time is 3h-9h; (2) the temperature of the re-sintering treatment is 1000 DEG C-1300 DEG C, and the holding time is 2h-6h; (3) the temperature of the silver burning treatment is 600 DEG C-800 DEG C, and the holding time is 20min-50min; (4) the temperature of the polarization treatment is 70 DEG C-120 DEG C, and the polarization time is 10min-30min.

5. The method for preparing potassium sodium niobate-based lead-free piezoelectric ceramics according to claim 3, characterized in that, Satisfy one or more of the following (1)-(4): (1) the first ball milling treatment comprises the following steps: using anhydrous ethanol as a ball milling medium, and mixing the first mixture with zirconium beads with a diameter of 2mm-5mm as ball milling beads; the mass ratio of the first mixture, the ball milling beads and the anhydrous ethanol is 1:2-5:0.5-2.5, and the first ball milling time is 2h-10h; (2) the second ball milling treatment comprises the following steps: using anhydrous ethanol as a ball milling medium, and mixing the precursor with zirconium beads with a diameter of 2mm-5mm as ball milling beads; the mass ratio of the precursor, the ball milling beads and the anhydrous ethanol is 1:2-5:0.5-2.5, and the second ball milling time is 2h-10h; (3) the third ball milling treatment comprises the following steps: using zirconium beads with a diameter of 2mm-5mm as ball milling beads and mixing with copper oxide as ball milling medium; the mass ratio of the copper oxide, the ball milling beads and the anhydrous ethanol is 1:2-5:0.5-2.5, and the third ball milling time is 2h-10h; (4) the fourth ball milling treatment comprises the following steps: using zirconium beads with a diameter of 2mm-5mm as ball milling beads and mixing with the second mixture as ball milling medium; the mass ratio of the second mixture, the ball milling beads and the anhydrous ethanol is 1:2-5:0.5-2.5, and the fourth ball milling time is 5h-20h.

6. The method of producing a potassium sodium niobate-based lead-free piezoelectric ceramic according to any one of claims 3 to 5, characterized by, After the first ball milling treatment, the second ball milling treatment, the third ball milling treatment and the fourth ball milling treatment, a step of drying the wet powder slurry after the ball milling treatment is further included.

7. The method of producing a potassium sodium niobate-based lead-free piezoelectric ceramic according to claim 6, characterized by, The drying treatment temperature is 100℃-150℃, and the time is 2h-6h.

8. The method of producing a potassium sodium niobate-based lead-free piezoelectric ceramic according to any one of claims 3 to 5, characterized by, The granulation treatment comprises the following steps: a polyvinyl alcohol solution with a mass fraction of 3%-10% is used to mix with the ceramic powder after the fourth ball milling treatment and the drying treatment, and the mass ratio of the ceramic powder and the polyvinyl alcohol solution is (5-20):

100.

9. An electronic device, comprising: The potassium sodium niobate-based lead-free piezoelectric ceramic according to any one of claims 1-2.

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