Lead-free textured piezoelectric ceramic with high electromechanical transduction and high Curie temperature as well as preparation method and application of lead-free textured piezoelectric ceramic

Abstract

The invention discloses a lead-free textured piezoelectric ceramic with high electromechanical transduction and high Curie temperature as well as a preparation method and application thereof, and relates to a lead-free textured piezoelectric ceramic as well as a preparation method and application thereof. The problems that in the prior art, improvement of the electromechanical transduction coefficient is limited, and the material use temperature zone is narrowed are solved. The chemical formula is (KxNa1-x-yAy) (Nb1-zBz) O3-w vol.% M + u mol% N, the piezoelectric coefficient is 350 pC / N or more, the piezoelectric voltage coefficient is 70 * 10 <-3 > Vm / N or more, the electromechanical transduction coefficient is 25 * 10 <-12 > m < 2 > / N or more, the orthogonal-tetragonal phase transition temperature is 85 DEG C or more, and the Curie temperature is 370 DEG C or more. The method comprises the following steps: 1, weighing; 2, preparing matrix powder; 3, preparation of tape casting slurry; and 4, preparing the textured ceramic. The piezoelectric material is applied to high-performance, wide-temperature-range and environment-friendly piezoelectric devices.

Description

TECHNICAL FIELD

[0001] The present application relates to a lead-free textured piezoelectric ceramic and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of Internet of Things, wearable devices, wireless sensor networks and embedded systems, the global demand for miniaturized self-powered devices is growing. Traditional power supply methods (such as batteries) are difficult to meet the needs of device miniaturization and integration development, periodic charging and replacement increase the maintenance cost, and traditional wiring power supply limits the application range of the device, in addition, a large number of waste batteries will cause environmental pollution and other series of problems. Piezoelectric energy harvesting technology based on the positive piezoelectric effect of piezoelectric materials can convert the ubiquitous mechanical energy (such as human motion, structural vibration, sound wave, air flow, etc.) in the environment into electrical energy, and has extremely broad application potential in the field of miniaturized self-powered devices. As a sustainable, passive, highly compatible with modern electronic devices and green energy supply method, it has become a hot research and application.

[0003] The electromechanical conversion performance (especially the electromechanical conversion coefficient d 33 ×g 33 ) of piezoelectric materials directly affects the energy output performance and conversion efficiency of energy harvesting devices, and its phase transition temperature directly affects the use temperature range of energy harvesting devices. Potassium sodium niobate (K, Na) NbO3(KNN) based ceramics have outstanding electrical properties and high Curie temperature T c , and are considered as one of the systems that are expected to be applied in high-performance energy harvesting devices. In recent years, researchers have constructed a polymorphic phase boundary (PPT) by introducing new components, ion substitution and doping modification, adjusted the triclinic-orthorhombic phase transition temperature T R-O and / or the orthorhombic-tetragonal phase transition temperature T O-T to near room temperature, so that the free energy-polarization curve of KNN-based ceramics becomes flat, thereby reducing the energy barrier required for polarization rotation, and combining traditional solid-phase preparation methods to greatly improve the piezoelectric coefficient d 33 of such ceramics. However, due to the existence of thermodynamic limitations, the significant improvement of d 33 is always accompanied by a significant increase in dielectric constant ε r , which greatly limits the improvement of piezoelectric voltage coefficient g 33 (g=d / ε). Therefore, the electromechanical conversion coefficient d 33 ×g 33 value of the reported ceramics is often lower than 18×10 -12 m 2 / N limits the further improvement of the material's energy harvesting ability. In addition, due to the polymorphic phase transition temperature of this type of ceramic being near room temperature, the temperature stability of the electromechanical properties near room temperature deteriorates. Moreover, a significant increase in d 33 is often accompanied by a sharp drop in the Curie temperature T c , usually dropping below 300 °C. The existence of these problems severely restricts the operating temperature range of the ceramic. In summary, developing lead-free textured piezoelectric ceramics with both high electromechanical transduction coefficient d 33 ×g 33 and a wide application temperature range is of great significance for promoting the high-performance application process of this type of material and its devices. SUMMARY OF THE INVENTION

[0004] The present invention aims to solve the problems in the prior art that due to thermodynamics limitations, the improvement of the electromechanical transduction coefficient d 33 ×g 33 is restricted, and the operating temperature range of the material is narrowed. Furthermore, a lead-free textured piezoelectric ceramic with both high electromechanical transduction and high Curie temperature, its preparation method, and application are provided.

[0005] A lead-free textured piezoelectric ceramic with both high electromechanical transduction and high Curie temperature has a chemical general formula of (K x Na 1-x-y A y )(Nb 1-z B z )O3 - w vol.%M + u mol%N; where 0.40 < x < 0.52, 0.01 < y < 0.10, 0.02 < z < 0.20, 1 < w < 10, 0 ≤ u < 3; where A is one or a combination of two of Li and Ag, B is one or a combination of two of Ta and Sb, M is one or a combination of two of NaNbO3, KNbO3, and (K,Na)NbO3, and N is one or a combination of several of CuO, ZnO, Bi2O3, B2O3, and MnO2;

[0006] The above-mentioned lead-free textured piezoelectric ceramic with both high electromechanical transduction and high Curie temperature is composed of grains with a preferred orientation degree F c of more than 98% along

[001] 001 , and the element distribution in the oriented grains is uniform, without a core-shell structure. The main crystal phase of the oriented grains is the orthorhombic phase (O), and the mass ratio of the orthorhombic phase (O) is more than 65%;

[0007] The piezoelectric coefficient d 33 of the above-mentioned lead-free textured piezoelectric ceramic with both high electromechanical transduction and high Curie temperature is above 350 pC / N, and the piezoelectric voltage coefficient g 33 is 70×10 -3Vm / N or more, electromechanical conversion coefficient d 33 ×g 33 25×10 -12 m 2 / N or more, orthorhombic-tetragonal phase transition temperature is 85℃ or more, and Curie temperature is 370℃ or more.

[0008] A preparation method of a lead-free textured piezoelectric ceramic with high electromechanical conversion and high Curie temperature, which is completed according to the following steps:

[0009] I. Weighing:

[0010] According to the chemical formula (K x Na 1-x-y A y )(Nb 1-z B z )O3-w vol.%M+u mol%N stoichiometric ratio of K2CO3 powder, Na2CO3 powder, A source powder, Nb2O5 powder, B source powder, M sheet-like microcrystalline template and N source powder is weighed;

[0011] 0.40 < x < 0.52, 0.01 < y < 0.10, 0.02 < z < 0.20, 1 < w < 10, 0 ≤ u < 3; the A source powder is one or a combination of two of Li2CO3 and Ag2O; the B source powder is one or a combination of two of Ta2O5 and Sb2O3; the M sheet-like microcrystalline template is one or a combination of two of NaNbO3, KNbO3 and (K, Na)NbO3, and the M sheet-like microcrystalline template is a sheet-like microcrystalline oriented along

[001] c preferentially oriented and the aspect ratio is ≥10:1; the N source powder is one or a combination of several of CuO, ZnO, Bi2O3, B2O3 and MnO2; the particle size of the Nb2O5 powder and the B source powder is 150nm or less;

[0012] II. Preparation of base powder:

[0013] K2CO3 powder, Na2CO3 powder, A source powder, Nb2O5 powder and B source powder are mixed by wet ball milling for 24h-72h to obtain a mixture, the mixture is dried, then pre-sintered at a temperature of 680℃-820℃ for 1h-4h to obtain a pre-sintered powder, the pre-sintered powder is again wet ball milled, and finally dried to obtain the base powder;

[0014] The average particle size of the pre-sintered powder is 300nm or less;

[0015] III. Preparation of casting slurry:

[0016] The matrix powder, N source powder, solvent, dispersant, binder and plasticizer are ball-milled for 16h to 48h to obtain a base slurry. The M-shaped microcrystalline template is dispersed and added to the base slurry, and the ball milling is continued for 10min to 40min to obtain a mixed slurry. Finally, the mixed slurry is vacuum degassed to obtain a casting slurry.

[0017] IV. Preparation of Textured Ceramics:

[0018] The casting slurry is cast at a speed of 1 cm / s to 10 cm / s and then dried to obtain a cast film. The cast film is laser-cut and then stacked, followed by hot water isostatic pressing. The temperature is then increased to 550℃ to 700℃ at a rate of 0.1℃ / min to 0.6℃ / min, and the binder is removed at 550℃ to 700℃ for 1h to 4h. After the binder is removed, the ceramic green body is cold isostatically pressed at a pressure of 180MPa to 250MPa for 1min to 5min to obtain a ceramic green body. The ceramic green body is covered and buried with the matrix powder prepared in step two, and then the crucible is sealed. The ceramic green body is then sintered at a temperature of 1080℃ to 1160℃ for 1h to 12h to obtain a potassium sodium niobate-based textured piezoelectric ceramic with both high electromechanical conversion energy and high Curie temperature.

[0019] An application of a lead-free textured piezoelectric ceramic that simultaneously possesses high electromechanical transduction and high Curie temperature is described, which is used in high-performance, wide-temperature-range, and environmentally friendly piezoelectric devices; the high-performance, wide-temperature-range, and environmentally friendly piezoelectric devices are miniature energy harvesters, piezoelectric sensors, or precision actuators.

[0020] When a cantilever beam energy harvester is fabricated using lead-free textured piezoelectric ceramics that simultaneously possess high electromechanical conversion efficiency and high Curie temperature, the power density is 4.0 μW / mm² at an acceleration of 1g. 3 The Curie temperature is above 370°C.

[0021] Principle: This invention employs a synergistic strategy of crystal orientation texture and crystal phase structure regulation to enhance the overall energy harvesting performance of potassium sodium niobate-based ceramics. This invention selects ceramics with a high Curie temperature Ti. c (K) x Na 1-x-y A y (Nb) 1-z B z The O3-wvol.%M+umol%N system uses sheet-like M microcrystals as templates. Unlike traditional texture concepts, in this invention, the M sheet-like microcrystals guide the directional growth of the matrix to form along

[001] cThe highly oriented KNN-based textured ceramic also needs to be able to dissolve into the textured grains to form a solid solution (i.e. uniform element distribution, no core-shell structure) so as to regulate the crystal phase structure composition. By regulating the composition content of (K x Na 1-x-y A y )(Nb 1-z B z )O3, M and N, and the preparation technology and parameters, it is ensured that the grain texture degree F 001 is greater than 98%, and the ceramic main crystal phase is orthorhombic phase (O). The purpose of the above design of the present application is that, on the one hand, the crystal direction highly textured effectively plays the advantage of piezoelectric performance anisotropy, and at the same time, the 4O engineering domain formation can promote the polarization flip, significantly improves the piezoelectric coefficient d c under the premise of maintaining high Curie temperature T 33 . On the other hand, unlike the regulation of KNN-based ceramic in the past reports to coexist at room temperature, the present application regulates the main crystal phase to be orthorhombic phase at room temperature, which can effectively reduce the dielectric constant ε r of the ceramic, thereby significantly improving the piezoelectric voltage coefficient g 33 , and can also make the triclinic-orthorhombic and orthorhombic-tetragonal phase transition temperature far away from room temperature, thereby improving the temperature stability of the optimized electromechanical performance near room temperature. Under the synergistic effect of the above two aspects, the electromechanical conversion coefficient d 33 ×g 33 of the potassium sodium niobate-based textured ceramic prepared by the present application is greater than 25×10 -12 m 2 / N, the orthorhombic-tetragonal phase transition temperature is greater than 85℃, and the Curie temperature is greater than 370℃, that is, high electromechanical conversion and wide application temperature range are obtained at the same time.

[0022] The present application has the following beneficial effects:

[0023] The present application solves the problem that the improvement of the electromechanical conversion coefficient d 33 ×g 33 of the potassium sodium niobate-based ceramic is limited and the material use temperature range is narrowed due to the thermodynamic limitation in the prior art. The present application proposes a new strategy of synergistic effect of crystal direction texture and crystal phase structure regulation, and develops a lead-free piezoelectric textured ceramic which has high conversion coefficient d 33 ×g 33 and high Curie temperature T c , and the polycrystalline phase transition temperature T O-T is far away from room temperature. The (K x Na 1-x-y A y )(Nb 1-z B z )O3 ceramic prepared by the present application has the electromechanical conversion coefficient dO3-w vol.%M+umol%N ceramics are produced along

[001] c The grains are characterized by preferred orientation and uniform elemental distribution (no core-shell structure), with orthorhombic phase (O) as the main crystalline phase; the degree of orientation F of the lead-free textured piezoelectric ceramic possessing both high electromechanical transducer capacity and high Curie temperature is [not specified]. 001 The piezoelectric coefficient is over 98%, and the piezoelectric coefficient d 33 With a piezoelectric voltage coefficient of over 350 pC / N, g 33 70×10 -3 Above Vm / N, the electromechanical transduction coefficient d 33 ×g 33 25×10 -12 m 2 The orthorhombic-tetragonal phase transition temperature is above 85℃, and the Curie temperature is above 370℃. The overall energy harvesting performance obtained is significantly better than that of most lead-free piezoelectric ceramics reported to date. The potassium sodium niobate-based textured ceramic developed in this invention exhibits excellent energy harvesting capabilities in cantilever beam energy harvesters. This invention provides a design and fabrication approach for developing environmentally friendly piezoelectric ceramic materials with high energy harvesting capabilities and wide application temperature ranges, provides a high-performance lead-free new material for micro energy harvesters, and can also be applied to piezoelectric sensors and precision actuators, promoting the high performance, wide application temperature range, and environmental friendliness of electronic devices. Attached Figure Description

[0024] Figure 1 XRD pattern of potassium sodium niobate-based textured piezoelectric ceramic with high electromechanical transduction energy and high Curie temperature prepared in Example 1;

[0025] Figure 2 SEM image of the potassium sodium niobate-based textured piezoelectric ceramic with both high electromechanical transduction energy and high Curie temperature prepared in Example 1;

[0026] Figure 3 The dielectric temperature spectrum of the potassium sodium niobate-based textured piezoelectric ceramic with both high electromechanical transduction energy and high Curie temperature prepared in Example 1 at 1 kHz.

[0027] Figure 4 The variations of (a) piezoelectric coefficient and relative permittivity, and (b) piezoelectric voltage coefficient and electromechanical transduction coefficient of the potassium sodium niobate-based textured piezoelectric ceramic with high electromechanical transduction and high Curie temperature prepared in Example 1 and the untextured piezoelectric ceramic prepared in the comparative experiment;

[0028] Figure 5 The output power density of the energy harvester prepared by the potassium sodium niobate-based textured piezoelectric ceramic with high electromechanical conversion energy and high Curie temperature in Example 1 and the untextured piezoelectric ceramic in the comparative experiment varies with acceleration. Specific Embodiments

[0029] The technical solution of the present invention is not limited to the specific embodiments listed below, and also includes any combination between the specific embodiments.

[0030] Specific Embodiment 1: In this embodiment, a lead-free textured piezoelectric ceramic with both high electromechanical energy conversion and high Curie temperature has a chemical general formula of (K x Na 1-x-y A y )(Nb 1-z B z )O3 - w vol.% M + u mol% N; where 0.40 < x < 0.52, 0.01 < y < 0.10, 0.02 < z < 0.20, 1 < w < 10, 0 ≤ u < 3; where A is one or a combination of two of Li and Ag, B is one or a combination of two of Ta and Sb, M is one or a combination of two of NaNbO3, KNbO3, and (K,Na)NbO3, and N is one or a combination of several of CuO, ZnO, Bi2O3, B2O3, and MnO₂;

[0031] The lead-free textured piezoelectric ceramic with both high electromechanical energy conversion and high Curie temperature is composed of grains with a preferred orientation degree F c of more than 98%, and the element distribution in the oriented grains is uniform, without a core-shell structure. The main crystal phase of the oriented grains is the orthorhombic phase (O), and the mass ratio of the orthorhombic phase (O) is more than 65%; 001 The lead-free textured piezoelectric ceramic with both high electromechanical energy conversion and high Curie temperature has a piezoelectric coefficient d

[0032] of 350 pC / N or more, a piezoelectric voltage coefficient g 33 of 70×10<00?00090>Vm / N or more, an electromechanical energy conversion coefficient d -3 [[ID=?2]] 33 33 ×g -12 of more than 2 33 m 33 / N, the orthorhombic-tetragonal phase transition temperature is 85 °C or more, and the Curie temperature is 370 °C or more.

[0033] Beneficial effects of this specific embodiment:

[0034] This specific embodiment solves the problems of the limited improvement of the electromechanical energy conversion coefficient d 33 ×g 33 of sodium potassium niobate-based ceramics due to thermodynamics limitations in the prior art and the narrowing of the material use temperature range. This specific embodiment proposes a new strategy of synergistically regulating crystal orientation texture and crystal phase structure, and develops a material with a high energy conversion coefficient d 33×g 33 and high Curie temperature T c and high Curie temperature T O-T Lead-free piezoelectric textured ceramics far from room temperature. The (K x Na 1-x-y A y )(Nb 1-z B z )O3-w vol.%M+u mol%N ceramics consist of grains with preferred orientation along

[001] c and uniform element distribution (without core-shell structure), the main crystal phase is orthorhombic (O); the degree of orientation F 001 of the lead-free textured piezoelectric ceramics with high electromechanical transduction and high Curie temperature is more than 98%, the piezoelectric coefficient d 33 is more than 350 pC / N, the piezoelectric voltage coefficient g 33 is more than 70×10 -3 Vm / N, the electromechanical transduction coefficient d 33 ×g 33 is more than 25×10 -12 m 2 / N, the orthorhombic-tetragonal phase transition temperature is more than 85℃, and the Curie temperature is more than 370℃. The comprehensive energy harvesting performance obtained is significantly better than most of the lead-free piezoelectric ceramics reported so far. The potassium sodium niobate-based textured ceramics developed in this embodiment exhibit excellent energy harvesting capability in a cantilever beam energy harvester. This embodiment can provide a design and preparation idea for developing environmentally friendly piezoelectric ceramic materials with high energy harvesting capability and wide application temperature range, provide a high-performance lead-free new material for micro energy harvesters, and can also be applied to piezoelectric sensors and precision drivers, promoting the high performance, wide application temperature range and environmental friendliness of electronic devices.

[0035] Embodiment two: this embodiment is different from embodiment one in that the N is one or a combination of the two of CuO and Bi2O3. The others are the same as embodiment one.

[0036] Embodiment three: this embodiment is different from one or two of embodiment one or two in that 0.40 < x < 0.50, 0.01 < y < 0.08, 0.05 < z < 0.18, 1 < w < 6, and 0 ≤ u < 2. The others are the same as embodiment one or two.

[0037] Embodiment four: a preparation method of a lead-free textured piezoelectric ceramic with high electromechanical transduction and high Curie temperature, which is completed according to the following steps:

[0038] I. Weighing:

[0039] According to the chemical general formula as (K x Na 1-x-y A y )(Nb 1-z B z )O3-w vol.%M+u mol%N stoichiometric ratio of K2CO3 powder, Na2CO3 powder, A source powder, Nb2O5 powder, B source powder, M sheet-like microcrystalline template and N source powder are weighed;

[0040] The 0.40 < x < 0.52, 0.01 < y < 0.10, 0.02 < z < 0.20, 1 < w < 10, 0 ≤ u < 3; the A source powder is one or a combination of two of Li2CO3 and Ag2O; the B source powder is one or a combination of two of Ta2O5 and Sb2O3; the M sheet-like microcrystalline template is one or a combination of two of NaNbO3, KNbO3 and (K, Na)NbO3, and the M sheet-like microcrystalline template is a sheet-like microcrystalline along

[001] c preferentially oriented and a diameter-thickness ratio ≥ 10:1; the N source powder is one or a combination of several of CuO, ZnO, Bi2O3, B2O3 and MnO2; the particle size of the Nb2O5 powder and the B source powder is 150 nm or less;

[0041] II. Preparation of the matrix powder:

[0042] The K2CO3 powder, Na2CO3 powder, A source powder, Nb2O5 powder and B source powder are mixed by wet ball milling for 24h-72h to obtain a mixture, the mixture is dried, then pre-sintered at a temperature of 680℃-820℃ for 1h-4h to obtain a pre-sintered powder, the pre-sintered powder is again wet ball milled, and finally dried to obtain the matrix powder;

[0043] The average particle size of the pre-sintered powder is 300nm or less;

[0044] III. Preparation of the casting slurry:

[0045] The matrix powder, N source powder, solvent, dispersant, binder and plasticizer are ball milled for 16h-48h to obtain a basic slurry, the M sheet-like microcrystalline template is dispersed into the basic slurry, and the ball milling is continued for 10min-40min to obtain a mixed slurry, and finally the mixed slurry is vacuum degassed to obtain the casting slurry;

[0046] IV. Preparation of the textured ceramic:

[0047] The cast slurry is cast at a speed of 1 cm / s to 10 cm / s, then dried to obtain a cast film, the cast film is laser cut, then laminated, then subjected to hot water isostatic pressing, then heated at a heating rate of 0.1 ℃ / min to 0.6 ℃ / min to 550 ℃ to 700 ℃, and under the condition of a temperature of 550 ℃ to 700 ℃, the glue is discharged for 1 h to 4 h, after the glue is discharged, cold isostatic pressing is performed under the condition of a pressure of 180 MPa to 250 MPa for 1 min to 5 min to obtain a ceramic green body, the ceramic green body is covered and buried with the base body powder prepared in step two, then the crucible is sealed, and the ceramic green body is sintered at a temperature of 1080 ℃ to 1160 ℃ for 1 h to 12 h to obtain a potassium sodium niobate-based textured piezoelectric ceramic with high electromechanical transduction and high Curie temperature.

[0048] Specific embodiment five: different from the specific embodiment four, the purity of the K2CO3 powder, the Na2CO3 powder, the A source powder, the Nb2O5 powder, the B source powder and the N source powder in step one is not less than 99.5%. The others are the same as the specific embodiment four.

[0049] Specific embodiment six: different from the specific embodiment four or five, the wet ball milling in step two is specifically using ZrO2 balls with a diameter of 3 mm to 15 mm as the grinding balls, and adding anhydrous ethanol, and the ball milling is performed at a speed of 240 r / min to 380 r / min; the pre-sintering in step two is performed at a temperature of 700 ℃ to 760 ℃ for 2 h; the average particle size of the pre-sintered powder in step two is 200 nm to 260 nm. The others are the same as the specific embodiment four or five.

[0050] Specific embodiment seven: different from the specific embodiment four to six, the solvent in step three is a mixture of dimethylbenzene and ethanol; the dispersant in step three is KD-1; the binder in step three is polyvinyl butyral; and the plasticizer in step three is a mixture of polyalkylene glycol and butyl benzyl phthalate. The others are the same as the specific embodiment four to six.

[0051] Specific embodiment eight: different from the specific embodiment four to seven, the thickness of the cast film in step four is 15 μm to 80 μm; and the lamination in step four is specifically performed at a temperature of 40 ℃ to 120 ℃ and a pressure of 5 MPa to 60 MPa. The others are the same as the specific embodiment four to seven.

[0052] Specific embodiment nine: the difference between this embodiment and one of specific embodiments four to eight is that the hot isostatic pressing treatment in step four is specifically carried out under the condition of a temperature of 50-95℃ and a pressure of 20-60MPa; in step four, the ceramic green body is heated to 600℃ at a heating rate of 0.2℃ / min, and the glue is discharged under the condition of a temperature of 600℃; in step four, the cold isostatic pressing is carried out under the condition of a pressure of 200MPa; in step four, the ceramic green body is heated to 1080-1160℃ at a heating rate of 3-6℃ / min. The others are the same as specific embodiments four to eight.

[0053] Specific embodiment ten: the application of the lead-free textured piezoelectric ceramic with high electromechanical transduction and high Curie temperature simultaneously, which is applied to high-performance, wide-temperature-range and environment-friendly piezoelectric devices; the high-performance, wide-temperature-range and environment-friendly piezoelectric devices are micro energy harvesters, piezoelectric sensors or precision drivers.

[0054] When the lead-free textured piezoelectric ceramic with high electromechanical transduction and high Curie temperature simultaneously is used to prepare a cantilever energy harvester, the power density is 4.0μW / mm 3 The Curie temperature is above 370℃.

[0055] The beneficial effects of the present application are verified by the following examples:

[0056] Example one:

[0057] A preparation method of a lead-free textured piezoelectric ceramic with high electromechanical transduction and high Curie temperature simultaneously, which is completed according to the following steps:

[0058] I. Weighing:

[0059] According to the chemical formula (K 0.44 Na 0.52 Li 0.04 )(Nb 0.85 Ta 0.15 )O3-5 vol.%NaNbO3 stoichiometric ratio of K2CO3 powder, Na2CO3 powder, A source powder, Nb2O5 powder, B source powder and M flaky microcrystalline template;

[0060] The A source powder is Li2CO3; the B source powder is Ta2O5; the M flaky microcrystalline template is NaNbO3, and the M flaky microcrystalline template is a flaky microcrystalline along

[001] c preferentially oriented and with a diameter-thickness ratio of ≥10:1; the particle size of the Nb2O5 powder and the B source powder is ≤150nm;

[0061] II. Preparation of base powder:

[0062] The K2CO3 powder, Na2CO3 powder, A source powder, Nb2O5 powder and B source powder are mixed by wet ball milling for 48h to obtain a mixture, the mixture is dried, and then pre-sintered at a temperature of 750 DEG C for 2h to obtain a pre-sintered powder, the pre-sintered powder is again wet ball milled, and finally dried to obtain the matrix powder;

[0063] The average particle size of the pre-sintered powder is 200nm.

[0064] III. Preparation of the casting slurry:

[0065] The matrix powder, solvent, dispersant, binder and plasticizer are ball milled for 48h to obtain a basic slurry, the M sheet-like microcrystalline template is dispersed into the basic slurry, and the ball milling is continued for 25min to obtain a mixed slurry, and finally the mixed slurry is vacuum degassed to obtain the casting slurry.

[0066] IV. Preparation of the textured ceramic:

[0067] The casting slurry is cast at a speed of 1cm / s, and then dried to obtain a casting film, the casting film is laser cut, and then 25 layers are laminated, followed by hot water isostatic pressing treatment, and then heated to 600 DEG C at a heating rate of 0.2 DEG C / min, and degassed at a temperature of 600 DEG C for 2h, and after the degassing is completed, cold isostatic pressing is performed at a pressure of 200MPa for 3min to obtain a ceramic green body, the ceramic green body is covered and buried with the matrix powder prepared in step two, and then the crucible is sealed, and then the ceramic green body is sintered at a temperature of 1135 DEG C for 4h to obtain a potassium sodium niobate-based textured piezoelectric ceramic with high electromechanical transduction and high Curie temperature.

[0068] The chemical formula of the potassium sodium niobate-based textured piezoelectric ceramic with high electromechanical transduction and high Curie temperature is (K 0.44 Na 0.52 Li 0.04 )(Nb 0.85 Ta 0.15 )O3-5 vol.%NaNbO3.

[0069] The purity of the K2CO3 powder, Na2CO3 powder, A source powder, Nb2O5 powder and B source powder in step one is not less than 99.5%.

[0070] The wet ball milling in step two is specifically performed by using ZrO2 balls as grinding balls, and adding anhydrous ethanol, and the ball milling is performed at a rotation speed of 320r / min; the ZrO2 balls are ZrO2 balls with diameters of 3mm, 5mm and 10mm mixed in a number ratio of 120:60:20.

[0071] The solvent in step three is a mixture of xylene and ethanol, and the mass ratio of xylene to ethanol is 1:1; the dispersant in step three is KD-1; the binder in step three is polyvinyl butyral; the plasticizer in step three is a mixture of polyalkylene glycol and butyl benzyl phthalate; the concentration of the base slurry is 17.4 vol.%, the concentration of KD-1 is 2.4 vol.%, the concentration of polyvinyl butyral is 4.9 vol.%, the concentration of polyalkylene glycol is 2.3 vol.%, and the concentration of butyl benzyl phthalate is 2.2 vol.%;

[0072] The thickness of the cast film in step four is 40 μm; the lamination in step four is specifically carried out at a temperature of 75 ℃ and a pressure of 20 MPa;

[0073] The hot water isostatic pressing treatment in step four is specifically carried out at a temperature of 75 ℃ and a pressure of 45 MPa; and the ceramic green body is heated to 1135 ℃ at a heating rate of 5 ℃ / min.

[0074] The M sheet-like microcrystalline template in step one is prepared according to the following document: Chang Y, Yang Z, Chao X, et al. Synthesis and morphology of anisotropic NaNbO3 seed crystals [J]. Materials Chemistry and physics, 2008, 111(2-3): 195-200.

[0075] The comparative experiment is different from example one in that: the M sheet-like microcrystalline template is not added in step two; the ceramic green body is sintered at a temperature of 1110 ℃ for 4 h in step four; and the non-textured piezoelectric ceramic is obtained in step four; the chemical formula of the non-textured piezoelectric ceramic is (K 0.44 Na 0.52 Li 0.04 )(Nb 0.85 Ta 0.15 )O3. Other aspects are the same as example one.

[0076] Figure 1 The XRD pattern of the potassium sodium niobate-based textured piezoelectric ceramic with high electromechanical transduction and high Curie temperature prepared in example one; as shown in the figure, the ceramic has a pure perovskite phase structure, and the diffraction peak intensity of (001) / (100) and (002) / (200) crystal planes is dominant, while the peak of {001} orientation is very weak, indicating that the sample is highly oriented along

[001] c . The Lotgering factor (F 00lThe ceramic has a texture degree of about 99% along the

[001] direction, and has a high texture degree. According to the Rietveld refinement result of the XRD spectrum, the main crystal phase of the material is orthorhombic O phase, and the mass ratio of the orthorhombic phase (O) is 90%. c The ceramic has a texture degree of about 99% along the

[001] direction, and has a high texture degree. According to the Rietveld refinement result of the XRD spectrum, the main crystal phase of the material is orthorhombic O phase, and the mass ratio of the orthorhombic phase (O) is 90%.

[0077] Figure 2 The SEM spectrum of the potassium sodium niobate-based textured piezoelectric ceramic with high electromechanical conversion and high Curie temperature prepared in Example 1; it can be seen from the figure that the grain boundaries of the textured ceramic are clear, the grain arrangement presents a brick wall structure, the grain size is uniform, and the texture quality is high. According to the EDS, the element distribution of the grain composition is uniform, a solid solution is formed, and there is no core-shell structure.

[0078] Figure 3 The dielectric temperature spectrum of the potassium sodium niobate-based textured piezoelectric ceramic with high electromechanical conversion and high Curie temperature prepared in Example 1 at 1 kHz; it can be seen from the figure that the orthorhombic-tetragonal phase transition temperature T O-T of the textured ceramic is about 90℃, far away from room temperature, and the Curie temperature T c is about 375℃.

[0079] Figure 4 The changes of (a) the piezoelectric coefficient and the relative dielectric constant and (b) the piezoelectric voltage coefficient and the electromechanical conversion coefficient of the potassium sodium niobate-based textured piezoelectric ceramic with high electromechanical conversion and high Curie temperature prepared in Example 1 and the non-textured piezoelectric ceramic prepared in the comparative experiment; it can be seen from the figure that the piezoelectric coefficient d 33 of the textured ceramic is significantly improved compared with the non-textured ceramic, and the dielectric constant ε r is obviously reduced. Specifically, the piezoelectric coefficient d 33 of the textured ceramic is 368 pC / N, about 1.5 times of the non-textured ceramic, and the dielectric constant is only 55% of the non-textured ceramic. Due to the increase of the piezoelectric constant and the reduction of the dielectric constant, the piezoelectric voltage coefficient g 33 and the electromechanical conversion coefficient d 33 × g 33 of the textured ceramic are greatly improved. Specifically, the g 33 of the textured ceramic reaches 76.3 × 10 -3 Vm / N, which is 2.8 times of the non-textured ceramic, and the d 33 × g 33 is as high as 28.0 × 10 -12 m 2 / N, which is 4.3 times of the non-textured ceramic, confirming the advantages of the present application.

[0080] Based on the method for testing cantilever piezoelectric energy harvesters described in the literature Yan X, Zheng M, Gao X, et al. Ultrahigh energy harvesting performance in lead-free piezocomposites with intragranular structure[J]. Acta Materials, 2022, 222:117450, cantilever piezoelectric energy harvesters were fabricated using the potassium sodium niobate-based textured piezoelectric ceramic prepared in Example 1, which has both high electromechanical conversion energy and high Curie temperature, and the untextured piezoelectric ceramic prepared in the comparative experiment. The changes in energy harvesting performance were then evaluated. Figure 5 The figure shows the output power density as a function of acceleration for energy harvesters prepared from textured piezoelectric ceramics based on potassium sodium niobate, which possess both high electromechanical transduction capacity and high Curie temperature, and untextured piezoelectric ceramics used in the comparative experiment. As can be seen from the figure, the power density output of the textured sample is significantly higher than that of the untextured ceramic; for example, at an acceleration of 1g, the output power density reaches as high as 4.5 μW / mm². 3 .

[0081] Example 2: This example differs from Example 1 in that: in step 1, the chemical formula (K) is used... 0.432 Na 0.529 Li 0.039 (Nb) 0.854 Ta 0.146 Weigh out K2CO3 powder, Na2CO3 powder, source A powder, Nb2O5 powder, source B powder, and M-shaped microcrystalline template in a stoichiometric ratio of 3 vol.% NaNbO3; in step four, sinter the ceramic green body at 1130℃ for 4 hours. Other steps are the same as in Example 1.

[0082] Example 2 describes the preparation of a lead-free textured piezoelectric ceramic with both high electromechanical transduction energy and high Curie temperature, constructed along

[001] . c Preferred orientation degree F 001 It consists of 99% grains, and the elements in the oriented grains are evenly distributed and do not have a core-shell structure. The main crystalline phase of the oriented grains is the orthorhombic phase (O), and the mass percentage of the orthorhombic phase (O) is ~92%.

[0083] The aforementioned lead-free textured piezoelectric ceramic, which simultaneously possesses high electromechanical conversion energy and high Curie temperature, has a piezoelectric coefficient d. 33 It is 354pC / N, and the piezoelectric voltage coefficient is g. 33 It is 71.4×10 -3 Vm / N, electromechanical transduction coefficient d 33 ×g 33 25.3×10 -12 m 2 / N, the orthorhombic-tetragonal phase transition temperature is 94℃, and the Curie temperature is 376℃.

[0084] Example 3: This example differs from Example 1 in that: in step 1, the chemical formula (K) is used... 0.44 Na 0.52 Li 0.04 (Nb) 0.85 Ta 0.15 The stoichiometric ratio of K2CO3 powder, Na2CO3 powder, source A powder, Nb2O5 powder, source B powder, M-lamellar microcrystalline template, and N-source powder were weighed out. The N-source powder mentioned in step one was CuO. The purity of the N-source powder mentioned in step one was not less than 99.5%. In step three, the matrix powder, N-source powder, solvent, dispersant, binder, and plasticizer were ball-milled for 48 hours to obtain a basic slurry. The total concentration of matrix powder and N-source powder in the basic slurry mentioned in step three was 17.4 vol.%. In step four, the ceramic green body was sintered at 1115℃ for 4 hours. Other steps were the same as in Example 1.

[0085] Example 3 describes the preparation of a lead-free textured piezoelectric ceramic with both high electromechanical transduction energy and high Curie temperature, constructed along

[001] . c Preferred orientation degree F 001 It consists of 99% grains, and the elements in the oriented grains are evenly distributed and do not have a core-shell structure. The main crystalline phase of the oriented grains is the orthorhombic phase (O), and the mass percentage of the orthorhombic phase (O) is ~86%.

[0086] The aforementioned lead-free textured piezoelectric ceramic, which simultaneously possesses high electromechanical conversion energy and high Curie temperature, has a piezoelectric coefficient d. 33 It is 376 pC / N, and the piezoelectric voltage coefficient is g. 33 79.5×10 -3 Vm / N, electromechanical transduction coefficient d 33 ×g 33 30.0×10 -12 m 2 / N, the orthogonal-tetragonal phase transition temperature is 86℃, and the Curie temperature is 371℃.

Claims

1. A lead-free textured piezoelectric ceramic that simultaneously possesses high electromechanical transduction energy and high Curie temperature, characterized in that... Its chemical general formula is (K x Na 1-x-y A y )(Nb 1-z B z )O3 - w vol.%M + u mol%N; where 0.40 < x < 0.52, 0.01 < y < 0.10, 0.02 < z < 0.20, 1 < w < 10, 0 ≤ u < 3; where A is one or a combination of two of Li and Ag, B is one or a combination of two of Ta and Sb, M is one or a combination of two of NaNbO3, KNbO3, and (K,Na)NbO3, and N is one or a combination of several of CuO, ZnO, Bi2O3, B2O3, and MnO2; The lead-free textured piezoelectric ceramic, which simultaneously possesses high electromechanical conversion energy and high Curie temperature, is formed along [001]. c Preferred orientation degree F 001 It consists of more than 98% grains, and the elements in the oriented grains are evenly distributed and do not have a core-shell structure. The main crystalline phase of the oriented grains is the orthorhombic phase (O), and the mass percentage of the orthorhombic phase (O) is more than 65%. The aforementioned lead-free textured piezoelectric ceramic, which simultaneously possesses high electromechanical conversion energy and high Curie temperature, has a piezoelectric coefficient d. 33 With a piezoelectric voltage coefficient of over 350 pC / N, g 33 70×10 -3 Above Vm / N, the electromechanical transduction coefficient d 33 ×g 33 25×10 -12 m 2 / N or higher, orthogonal-tetragonal phase transition temperature above 85℃, Curie temperature above 370℃.

2. The lead-free textured piezoelectric ceramic with both high electromechanical transduction capacity and high Curie temperature according to claim 1, characterized in that... The N mentioned is one or a combination of CuO and Bi2O3.

3. A lead-free textured piezoelectric ceramic with both high electromechanical transduction capacity and high Curie temperature according to claim 1, characterized in that... The 0.40 mentioned <x<0.50,0.01<y<0.08,0.05<z<0.18,1<w<6,0≤u<2。 4. The method for preparing a lead-free textured piezoelectric ceramic with both high electromechanical transduction energy and high Curie temperature as described in claim 1, characterized in that... It is done in the following steps: I. Weighing: According to the general chemical formula (K x Na 1-x-y A y (Nb) 1-z B z Weigh out K2CO3 powder, Na2CO3 powder, A source powder, Nb2O5 powder, B source powder, M-shaped microcrystalline template and N source powder according to the stoichiometric ratio of O3-w vol.%M+u mol%N; where 0.40 < x < 0.52, 0.01 < y < 0.10, 0.02 < z < 0.20, 1 < w < 10, 0 ≤ u < 3; the A-source powder is one or a combination of two of Li2CO3 and Ag2O; the B-source powder is one or a combination of two of Ta2O5 and Sb2O3; the M flaky microcrystalline template is one or a combination of two of NaNbO3, KNbO3, and (K,Na)NbO3, and the M flaky microcrystalline template is a flaky microcrystal with a preferred orientation along [001] c and an aspect ratio ≥ 10:1; the N-source powder is one or a combination of several of CuO, ZnO, Bi2O3, B2O3, and MnO2; the particle sizes of both the Nb2O5 powder and the B-source powder are below 150 nm; II. Preparation of matrix powder: K2CO3 powder, Na2CO3 powder, A source powder, Nb2O5 powder and B source powder are wet ball-milled and mixed for 24h to 72h to obtain a mixture. The mixture is dried and then pre-calcined at a temperature of 680℃ to 820℃ for 1h to 4h to obtain pre-calcined powder. The pre-calcined powder is wet ball-milled again and finally dried to obtain matrix powder. The average particle size of the pre-calcined powder is below 300 nm; III. Preparation of Casting Slurry: The matrix powder, N source powder, solvent, dispersant, binder and plasticizer are ball-milled for 16h to 48h to obtain a base slurry. The M-shaped microcrystalline template is dispersed and added to the base slurry, and the ball milling is continued for 10min to 40min to obtain a mixed slurry. Finally, the mixed slurry is vacuum degassed to obtain a casting slurry. IV. Preparation of Textured Ceramics: The casting slurry is cast at a speed of 1 cm / s to 10 cm / s and then dried to obtain a cast film. The cast film is laser-cut and then stacked, followed by hot water isostatic pressing. The temperature is then increased to 550℃ to 700℃ at a rate of 0.1℃ / min to 0.6℃ / min, and the binder is removed at 550℃ to 700℃ for 1h to 4h. After the binder is removed, the ceramic green body is cold isostatically pressed at a pressure of 180MPa to 250MPa for 1min to 5min to obtain a ceramic green body. The ceramic green body is covered and buried with the matrix powder prepared in step two, and then the crucible is sealed. The ceramic green body is then sintered at a temperature of 1080℃ to 1160℃ for 1h to 12h to obtain a potassium sodium niobate-based textured piezoelectric ceramic with both high electromechanical conversion energy and high Curie temperature.

5. The method for preparing a lead-free textured piezoelectric ceramic with both high electromechanical transduction energy and high Curie temperature according to claim 4, characterized in that... The purity of the K2CO3 powder, Na2CO3 powder, A source powder, Nb2O5 powder, B source powder and N source powder mentioned in step one shall not be less than 99.5%.

6. The method for preparing a lead-free textured piezoelectric ceramic with both high electromechanical transduction energy and high Curie temperature according to claim 4, characterized in that... The wet ball milling described in step two specifically involves using ZrO2 balls with a diameter of 3 mm to 15 mm as milling balls, adding anhydrous ethanol, and milling at a speed of 240 r / min to 380 r / min. In step two, the powder is pre-calcined at a temperature of 700℃ to 760℃ for 2 hours. The average particle size of the pre-calcined powder described in step two is 200 nm to 260 nm.

7. The method for preparing a lead-free textured piezoelectric ceramic with both high electromechanical transduction energy and high Curie temperature according to claim 4, characterized in that... The solvent mentioned in step three is a mixture of xylene and ethanol; the dispersant mentioned in step three is KD-1; the binder mentioned in step three is polyvinyl butyral; and the plasticizer mentioned in step three is a mixture of polyalkylene glycol and butyl benzyl phthalate.

8. The method for preparing a lead-free textured piezoelectric ceramic with both high electromechanical transduction energy and high Curie temperature according to claim 4, characterized in that... The thickness of the cast film mentioned in step four is 15μm to 80μm; the lamination mentioned in step four is specifically carried out under the conditions of temperature of 40℃ to 120℃ and pressure of 5MPa to 60MPa.

9. The method for preparing a lead-free textured piezoelectric ceramic with both high electromechanical transduction energy and high Curie temperature according to claim 4, characterized in that... The hot water isostatic pressing treatment described in step four is carried out under the conditions of a temperature of 50℃~95℃ and a pressure of 20MPa~60MPa; in step four, the temperature is raised to 600℃ at a heating rate of 0.2℃ / min, and the binder is removed at a temperature of 600℃; in step four, cold isostatic pressing is carried out under a pressure of 200MPa; in step four, the ceramic green body is heated to 1080℃~1160℃ at a heating rate of 3℃ / min~6℃ / min.

10. The application of a lead-free textured piezoelectric ceramic with both high electromechanical transduction capacity and high Curie temperature as described in claim 1, characterized in that... It is used in high-performance, wide-temperature-range and environmentally friendly piezoelectric devices; the high-performance, wide-temperature-range and environmentally friendly piezoelectric devices are miniature energy harvesters, piezoelectric sensors or precision actuators; When a cantilever beam energy harvester is fabricated using lead-free textured piezoelectric ceramics that simultaneously possess high electromechanical conversion efficiency and high Curie temperature, the power density is 4.0 μW / mm² at an acceleration of 1g. 3 The Curie temperature is above 370°C.

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