Potassium sodium niobate-based textured piezoelectric ceramic with high piezoelectric response and temperature stability and a preparation method thereof

Abstract

This invention relates to a potassium sodium niobate-based textured piezoelectric ceramic with high voltage response and temperature stability, and its preparation method. The general chemical formula of the textured piezoelectric ceramic is (0.98-x)((K 0.49 Na 0.49 Li 0.02 (Nb) 0.96 Sb 0.04 )O3)-0.02((Bi 0.5 Na 0.5 (Zr) 0.8 Ti 0.2 The formula is: ⇌ (CaZrO3)−x(CaZrO3)+4wt.%NaNbO3, 0.01≤x≤0.04; This method includes solid-state synthesis, a two-step molten salt method combined with separation, template grain growth, tape casting, hot pressing, debinding, a two-step sintering process, silver firing, and polarization. Compared with existing technologies, this invention, through solid-state synthesis, template grain growth combined with tape casting, and a two-step sintering process, can obtain KNN-based lead-free textured piezoelectric ceramics with high voltage response. More importantly, by constructing polycrystalline phase boundaries and regulating domain structures, the piezoelectric coefficient and inverse piezoelectric coefficient can exhibit small rates of change over a wide temperature range, resulting in excellent temperature stability.

Description

Technical Field

[0001] This invention belongs to the field of functional ceramics and relates to a potassium sodium niobate-based textured piezoelectric ceramic with high voltage response and temperature stability, and its preparation method. Background Technology

[0002] Piezoelectric ceramics are a type of information-functional ceramic material that can convert mechanical energy into electrical energy. They are the core material for manufacturing electronic components with electromechanical conversion functions and have been widely used in medical imaging, acoustic sensors, acoustic transducers, ultrasonic motors, and other fields.

[0003] Currently, lead titanate and lead zirconate titanate-based piezoelectric ceramics have maintained a major share of the piezoelectric materials market due to their high piezoelectric response and excellent temperature stability. However, their raw materials contain high levels of lead, which is highly toxic and poses significant risks to personnel, the environment, and safety hazards during production and recycling. Therefore, developing high-performance, high-stability lead-free piezoelectric materials comparable to traditional PZT-based piezoelectric ceramics for application in electronic components has significant strategic and economic value.

[0004] Potassium sodium niobate ((K,Na)NbO3, KNN) ceramics are considered one of the most promising candidates for lead-free piezoelectric ceramics due to their relatively good overall properties. While pure potassium sodium niobate lead-free piezoelectric ceramics have a high Curie temperature (~430 °C), their ferroelectric and piezoelectric properties are poor. The piezoelectric coefficient of unmodified (K,Na)NbO3 ceramics obtained by traditional solid-state sintering methods is relatively low. d 33 The piezoelectric properties are typically 80-120 pC / N, which is still far from the piezoelectric properties of lead-based ceramics. Current research on potassium sodium niobate-based lead-free piezoelectric ceramics mainly focuses on improving electrical properties and temperature stability. This is primarily achieved by controlling the chemical composition to construct polymorphic phase boundaries at room temperature and by preparing textured ceramics to control crystal orientation, both of which have yielded significant progress.

[0005] Patent CN116639974A discloses a piezoelectric ceramic material with high voltage response and its preparation method, wherein the stoichiometry conforms to the general chemical formula 0.95(K). 0.55 Na 0.45 NbO3-0.05LiTaO3- x mol. %Sm2O3; where 0.2≤ x With a value of ≤0.6, this patent achieves better piezoelectric properties through rare earth doping modification, but it has not been optimized in terms of Curie temperature and temperature stability, which limits its application in medium and high temperature environments.

[0006] Patent CN117125981A discloses a temperature-stable potassium sodium niobate multilayer composite textured ceramic. By constructing multilayer composite ceramics with different components, the piezoelectric coefficient is achieved in the range of room temperature to 180°C. d 33 and d 33 * The change rates are less than 5% and 2% respectively, and this ceramic material has high application value in fields such as high-temperature piezoelectric sensors and energy harvesters.

[0007] Existing patents on small-signal piezoelectric coefficient d 33 Significant breakthroughs have been made in improving piezoelectricity, achieving very high piezoelectric responses; however, from the perspective of piezoelectric material applications, the quality factor of the material is the small-signal piezoelectric coefficient. d 33 And operating temperature range, while potassium sodium niobate-based piezoelectric ceramics have always struggled to break through the piezoelectric coefficient. d 33 The problem is poor temperature stability; while obtaining the high voltage response, its temperature stability was not taken into account. Generally, the higher the piezoelectric performance, the lower the Curie temperature, which cannot guarantee reliable and stable sensing output over a wide operating temperature range. Summary of the Invention

[0008] The purpose of this invention is to overcome at least one of the defects in the prior art and provide a potassium sodium niobate-based textured piezoelectric ceramic with high voltage response and temperature stability, as well as its preparation method. This invention uses a solid-state synthesis method, a template grain growth method combined with tape casting and a two-step sintering process to obtain lead-free textured piezoelectric ceramics that simultaneously possess high voltage response. More importantly, by constructing room-temperature polycrystalline phase boundaries and large-scale domain structures, the piezoelectric coefficient and inverse piezoelectric coefficient exhibit small rates of change over a wide temperature range, resulting in excellent temperature stability.

[0009] The objective of this invention can be achieved through the following technical solutions:

[0010] One of the technical solutions of this invention is to provide a potassium sodium niobate-based textured piezoelectric ceramic with high voltage response and temperature stability, wherein the general chemical formula of the textured piezoelectric ceramic is (0.98-x)((K 0.49 Na 0.49 Li 0.02 (Nb) 0.96 Sb 0.04 )O3)- 0.02((Bi 0.5 Na 0.5 (Zr) 0.8 Ti 0.2 )O3)-(CaZrO3) x +4 wt. % (relative to the total mass of the powder) NaNbO3, 0 ≤ x ≤0.04.

[0011] As a preferred technical solution, the aforementioned x The values ​​are 0, 0.01, 0.02, 0.03, or 0.04.

[0012] As a preferred technical solution, the aforementioned x It is 0.03 or 0.04.

[0013] As a preferred technical solution, the aforementioned x It is 0.03.

[0014] As a preferred technical solution, the grain orientation of the textured piezoelectric ceramic is in <001> C >95.0%.

[0015] Furthermore, when x When it is 0.03, at <001> C The direction exhibits high texture (f=98.2%>95.0%), demonstrating... OT Phase coexistence. The grain size is approximately 20-50 μm, and the dielectric constant remains stable from room temperature to the Curie temperature range, exhibiting good piezoelectric properties. Its piezoelectric coefficient... d 33 The piezoelectric coefficient is 520 pC / N, and the inverse piezoelectric coefficient is 525 pm / V under an electric field of 40 kV / cm. The piezoelectric coefficient remains stable and then increases slightly with increasing temperature. Its piezoelectric coefficient changes by 3.8% in the temperature range of 25-200 ℃, showing excellent temperature stability. The unipolar strain remains stable and then increases slightly with increasing temperature. Correspondingly, the inverse piezoelectric coefficient can be calculated to change by 4.2% in the temperature range of 25-200 ℃, showing excellent temperature stability.

[0016] One of the technical solutions of the present invention is to provide a method for preparing potassium sodium niobate-based textured piezoelectric ceramics with high voltage response and temperature stability, the method comprising the following steps:

[0017] (1) Solid-phase synthesis method: Select sodium carbonate (Na2CO3), potassium carbonate (K2CO3), niobium oxide (Nb2O5), bismuth oxide (Bi2O3), zirconium oxide (ZrO2), lithium carbonate (Li2CO3), calcium carbonate (CaCO3), antimony oxide (Sb2O3), and titanium oxide (TiO2), weigh them according to their chemical composition, add ball milling media to ball mill and mix them completely, discharge and dry them to obtain powder base material;

[0018] (2) Two-step molten salt method combined with separation method: In the first step, bismuth oxide, potassium carbonate, niobium oxide and molten salt are used for synthesis, followed by separation and filtration to obtain the plate-like precursor (Bi). 2.5 Na 3.5 Nb5O 18 The second step involves synthesizing a sheet-like precursor with potassium carbonate and molten salt, separating and filtering to obtain a high-quality, pure sodium niobate (NaNbO3) sheet-like template.

[0019] (3) Template grain growth method: The powder base material obtained in step (1) and the sheet template obtained in step (2) are respectively added to the mixed solvent, dispersant, plasticizer and binder, and mixed by roller mill to obtain casting slurry;

[0020] (4) Casting process: The cast slurry obtained in step (3) is cast using a convenient and small coating machine, and then dried to form a dry thick film with certain toughness and plasticity;

[0021] (5) Hot pressing process: The dried thick film obtained in step (4) is cut into the required shape and stacked in layers of 16 to 18, and finally hot pressed to form a ceramic green body;

[0022] (6) Debinding process: The ceramic green body obtained in step (5) is placed in a muffle furnace for debinding to obtain the ceramic green body;

[0023] (7) Two-step sintering process: The ceramic blank obtained in step (6) is sintered in two steps. After naturally cooling to room temperature, it is polished with sandpaper to obtain ceramic sheets.

[0024] (8) Silver firing process: The ceramic sheet obtained in step (7) is coated with silver paste and placed in a muffle furnace for silver firing to obtain a ceramic with silver electrodes, and then electrical tests are performed.

[0025] (9) Polarization process: The ceramic coated with silver electrodes obtained in step (8) is placed in a silicone oil bath for polarization to obtain a potassium sodium niobate-based textured piezoelectric ceramic with temperature stability.

[0026] As a preferred technical solution, the first half of the chemical formula (0.98-x)((K) 0.49 Na 0.49 Li 0.02 (Nb) 0.96 Sb 0.04 )O3)-0.02((Bi 0.5 Na 0.5 (Zr) 0.8 Ti 0.2 )O3)-(CaZrO3) x +4 wt.% NaNbO3 was prepared by solid-state synthesis, the latter half (4 wt. The % NaNbO3 was prepared by a sheet template through a two-step molten salt method combined with a separation method.

[0027] Furthermore, in step (1), ethanol is used as the milling medium, and the time is 12-24 h.

[0028] Furthermore, in step (2), sodium chloride (NaCl) is used as the molten salt. The total mass ratio of the raw materials in the first and second steps (the raw materials refer to the base materials other than sodium chloride in the preparation process of the first and second steps, that is, the raw materials in the first step refer to bismuth oxide, potassium carbonate, and niobium oxide, and the raw materials in the second step refer to the flake precursor and potassium carbonate) to the molten salt in the corresponding steps is 1:1.1 (that is, the total mass ratio of bismuth oxide, potassium carbonate, and niobium oxide in the first step to the molten salt in the first step is 1:1.1, and the total mass ratio of the flake precursor and potassium carbonate in the second step to the molten salt in the second step is 1:1.1). The holding time is 2 h. The molar ratio of bismuth oxide, potassium carbonate, and niobium oxide in the first step is 6.5:7:10, and the melting temperature is 1050-1100 ℃. The molar ratio of the flake precursor and potassium carbonate in the second step is 1:1.75, and the melting temperature is 970-1000 ℃.

[0029] In step (2), sodium tripolyphosphate was used as the separation reagent, and the amount of separation reagent added was 8-10% of the total mass of the molten salt mixture in the corresponding first or second step. wt The stirring speed is 600-800 rpm for 5-10 minutes. Specifically, the amount of the separation reagent added in the first step is 8-10% of the total mass of the bismuth oxide, potassium carbonate, niobium oxide, and molten salt mixture from the first step. wt The amount of the separation reagent added in the second step is 8-10% of the total mass of the flake precursor, potassium carbonate, and molten salt mixture from the second step. wt .%.

[0030] As a preferred technical solution, the aspect ratio of the sheet template in step (2) is (10-15):1.

[0031] Further, in step (3), the mixed solvent is methyl ethyl ketone and ethanol, the dispersant is triolein, the plasticizer is polyethylene glycol and dibutyl phthalate, the binder is polyvinyl butyral (PVB), and the mass ratio of the powder base, the sheet template and each reagent (methyl ethyl ketone, ethanol, triolein, polyethylene glycol, dibutyl phthalate and polyvinyl butyral) is (8.4-9):(0.3-0.4):(8-10):(4-6):(0.3-0.35):(0.4-0.5):(0.35-0.5):(1.1-1.2), the mixing speed is 16-18 r / min, and the time is 6-8 h.

[0032] Furthermore, in step (4), a casting knife is used for casting, and the moving speed of the casting knife is 28-30 cm / min.

[0033] As a preferred technical solution, the thickness of the dried thick film in step (4) is 10-15 μm.

[0034] As a preferred technical solution, in step (5), the hot pressing temperature is 45-55 ℃, the pressure is 8-12 MPa, and the time is 0.3-0.5 h. Among them, stacking refers to stacking 16 to 18 layers.

[0035] Furthermore, in step (6), the glue discharge temperature is 550-600 ℃ and the heat preservation time is 10-12 h.

[0036] Furthermore, the two-step sintering in step (7) includes a first step and a second step. The heating rate of the first step is 2-5℃ / min, the heating temperature is 1160-1200℃, and no holding time is required. The cooling rate of the second step is 10-15℃ / min, the cooling temperature is 1060-1100℃, and the holding time is 8-12 h.

[0037] As a preferred technical solution, in step (7), the sandpaper grit size is 400-2000 mesh and the sanding thickness is 0.3-0.6 mm.

[0038] Furthermore, in step (8), the diameter of the silver paste is 4-6 mm, the silver firing temperature is 550-600 ℃, and the holding time is 20-30 min.

[0039] Furthermore, in step (9), the polarization electric field is 2-4 kV / mm and the time is 20-30 min.

[0040] To obtain KNN-based piezoelectric ceramic materials with high voltage response and excellent temperature stability, a multiphase coexistence over a wide temperature range was constructed using chemical doping. CaZrO3, which regulates the phase boundary temperature, was doped into (0.98-x)((K 0.49 Na 0.49 Li 0.02 (Nb) 0.96 Sb 0.04 )O3)-0.02((Bi 0.5 Na 0.5 (Zr) 0.8 Ti 0.2 In an O3 matrix, the ferroelectric phase transition temperature was successfully controlled. T O-TThe mixture was adjusted to room temperature. This basic system was chosen because, firstly, the doping of multiple ions synergistically optimizes the sodium potassium niobate matrix, resulting in a high piezoelectric response. Secondly, systems similar to this basic system all exhibit piezoelectric properties above 400 pC / N, providing a foundation for this work to achieve a high piezoelectric response. Simultaneously, templated grain growth (TGG) was used to obtain… <001> C Oriented piezoelectric ceramics allow improvements in piezoelectric performance to depend more on the contribution of piezoelectric anisotropy, thereby reducing the impact of temperature-induced phase transitions on temperature stability. Therefore, this invention can improve piezoelectric performance while simultaneously enhancing temperature stability. This invention provides a sound design approach for developing practical advanced functional materials and represents a significant breakthrough for the future application of KNN-based piezoelectric ceramics in medium- and high-temperature environments.

[0041] Compared with existing related inventions, the present invention has the following advantages:

[0042] (1) This invention utilizes a combination of solid-state synthesis, template grain growth, tape casting, and two-step sintering to obtain lead-free textured piezoelectric ceramics with high piezoelectric properties (520 pC / N). More importantly, its piezoelectric coefficient changes by 3.8% within a temperature range of 25-200℃, and its large-signal inverse piezoelectric coefficient changes by 4.2% within the same temperature range. This is of great significance for the development of high-temperature, high-voltage, lead-free piezoelectric materials and has high application value in low- and medium-temperature transducers, sensors, actuators, and electric actuators.

[0043] (2) The preparation method of the present invention is simple, economical and practical, and it is a lead-free material. It will not pollute the environment during preparation, application and disposal. It is an environmentally friendly high-performance piezoelectric material. Attached Figure Description

[0044] Figure 1 The X-ray diffraction (XRD) patterns of the piezoelectric ceramics in Comparative Example 1 and Examples 2 to 5 of the present invention are shown.

[0045] Figure 2 This is a scanning electron microscope (SEM) image of the potassium sodium niobate-based textured piezoelectric ceramic with high Curie temperature and temperature stability in Example 4 of the present invention.

[0046] Figure 3 Hysteresis loop diagrams of the piezoelectric ceramics in Comparative Example 1 and Examples 2 to 5 of the present invention;

[0047] Figure 4 The unipolar strain diagrams of the potassium sodium niobate-based textured piezoelectric ceramic with high voltage response and temperature stability in Example 4 of the present invention were obtained at different temperatures.

[0048] Figure 5 The diagram shows the in-situ temperature-dependent inverse piezoelectric coefficients of the piezoelectric ceramics in Comparative Example 1 and Examples 2 to 5 of this invention.

[0049] Figure 6 This is a statistical graph showing the piezoelectric coefficient and Curie temperature of the piezoelectric ceramics in Comparative Example 1 and Examples 2 to 5 of the present invention. Detailed Implementation

[0050] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. It should be understood that the drawings and the following embodiments are for illustrative purposes only and are not intended to limit the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These modifications and improvements all fall within the scope of protection of the present invention.

[0051] This invention relates to a potassium sodium niobate-based textured piezoelectric ceramic with high voltage response and temperature stability, and its preparation method. The general chemical formula of the textured piezoelectric ceramic is (0.98-x)((K 0.49 Na 0.49 Li 0.02 (Nb) 0.96 Sb 0.04 )O3)- 0.02((Bi 0.5 Na 0.5 (Zr) 0.8 Ti 0.2 )O3)- x (CaZrO3)+4 wt. % NaNbO3, 0.01≤ x ≤0.04; This method includes solid-state synthesis, a two-step molten salt method combined with separation, template grain growth, tape casting, hot pressing, debinding, a two-step sintering process, silver firing, and polarization. Compared with existing technologies, this invention can obtain KNN-based lead-free textured piezoelectric ceramics with high voltage response through solid-state synthesis, template grain growth combined with tape casting, and a two-step sintering process. More importantly, by constructing polycrystalline phase boundaries and regulating domain structures, the piezoelectric coefficient and inverse piezoelectric coefficient can exhibit small rates of change over a wide temperature range, resulting in excellent temperature stability.

[0052] Any preparation methods, materials, structures, or composition ratios not explicitly described in this technical solution are considered common technical features disclosed in the prior art.

[0053] The present invention will now be described in detail with reference to specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0054] Unless otherwise specified, the equipment used in the following embodiments is conventional equipment in the art; unless otherwise specified, the reagents used are commercially available products or prepared by conventional methods in the art. In the following embodiments, unless otherwise described in detail, conventional experimental methods in the art can be used.

[0055] Sodium carbonate (Na₂CO₃), potassium carbonate (K₂CO₃), niobium oxide (Nb₂O₅), bismuth oxide (Bi₂O₃), zirconium oxide (ZrO₂), lithium carbonate (Li₂CO₃), calcium carbonate (CaCO₃), antimony oxide (Sb₂O₃), and titanium oxide (TiO₂) have a purity greater than 99%, and all reagents are sourced from Aladdin Chemical Reagent Co., Ltd. and Sinopharm Reagent Co., Ltd. Butanone, ethanol, trioleic acid ester, polyethylene glycol, dibutyl phthalate, and polyvinyl butyral, except for polyvinyl butyral which is sourced from Aladdin Chemical Reagent Co., Ltd. (molecular weight 90,000-120,000), are all sourced from Sinopharm Chemical Reagent Co., Ltd., and all are chemically pure.

[0056] Comparative Example 1:

[0057] This comparative example provides a potassium sodium niobate-based textured piezoelectric ceramic with high voltage response and temperature stability, and a chemical composition of 0.98 (K). 0.49 Na 0.49 Li 0.02 (Nb) 0.96 Sb 0.04 )O3)-0.02((Bi 0.5 Na 0.5 (Zr) 0.8 Ti 0.2 )O3)+4 wt. The specific steps for preparing % NaNbO3 are as follows:

[0058] (1) 4.4764g Na2CO3, 5.7180g K2CO3, 21.5458g Nb2O5, 0.4015g Bi2O3, 0.3397g ZrO2, 0.1248g Li2CO3, 0.9846g Sb2O3, and 0.0551g TiO2 were selected as raw materials for textured piezoelectric ceramic materials. The materials were weighed according to their chemical composition, ethanol was added and ball-milled for 24 h, the materials were discharged, dried, and powder base material was obtained.

[0059] (2) Using the traditional two-step molten salt method combined with a separation method, the first step involves synthesizing 10 g Bi2O3, 3.1942 g K2CO3, 8.7762 g Nb2O5, and 24.1674 g NaCl. The mixture is melted and held at 1100 °C for 3 h, and then 10 g Bi2O3, 3.1942 g K2CO3, 8.7762 g Nb2O5, and 24.1674 g NaCl are added at 600 rpm. wt% sodium tripolyphosphate (4.6138 g) was separated for 8 min, filtered, and the sheet-like precursor Bi was obtained. 2.5 Na 3.5 Nb5O 18 The second step involves synthesis using 8 g of sheet-like precursor, 1.3705 g of K2CO3, and 10.3076 g of NaCl. The mixture is melt-treated at 970 °C for 2 h, and then 10 g of NaCl is added at 600 rpm. wt % sodium tripolyphosphate (1.9678g) was separated for 8 min, filtered, and high-quality pure sodium niobate (NaNbO3) sheet template with an aspect ratio of 15:1 was obtained;

[0060] (3) Add 10 g of butanone and 5 g of ethanol as a mixed solvent, 0.35 g of trioleic acid glyceride as a dispersant, 0.4 g of polyethylene glycol and 0.35 g of dibutyl phthalate as plasticizers, and 1.2 g of polyvinyl butyral (PVB) as a binder to the 9.6 g of powder base material obtained in step (1) and the 0.4 g of sheet template obtained in step (2). After obtaining the mixture, mix it in a roller mill at 16 r / min for 7 h to obtain the cast slurry.

[0061] (4) The casting slurry obtained in step (3) is cast using a convenient and small coating machine with a doctor blade moving at a speed of 30 cm / min. Then it is dried to form a dry thick film with a certain toughness and plasticity, with a thickness of 12.5 μm.

[0062] (5) The dried thick film obtained in step (4) is cut into the required shape and stacked layer by layer, and finally hot-pressed at 55 °C and 10 MPa for 0.3 h to form a ceramic green body;

[0063] (6) The ceramic green body obtained in step (5) is placed in a muffle furnace for debinding and kept at 600 °C for 10 h to obtain the ceramic green body;

[0064] (7) The ceramic blank obtained in step (6) is sintered in two steps: the temperature is increased to 1160 ℃ at 3 ℃ / min without holding, and then decreased to 1060 ℃ at 10 ℃ / min for 10 h. After naturally cooling to room temperature, it is polished to a thickness of 0.6 mm using 800 grit sandpaper to obtain ceramic sheet.

[0065] (8) Silver firing process: The ceramic sheet obtained in step (7) is coated with silver paste with a diameter of 4 mm and placed in a muffle furnace for silver firing. It is kept at 550 °C for 30 min to obtain ceramic coated with silver electrodes, and then electrical tests are performed.

[0066] (9) Polarization process: The ceramic coated with silver electrodes obtained in step (8) is placed in a silicone oil bath and polarized for 30 min under an electric field of 4 kV / mm to obtain a potassium sodium niobate-based lead-free textured piezoelectric ceramic with excellent temperature stability.

[0067] Example 2:

[0068] This embodiment provides a potassium sodium niobate-based textured piezoelectric ceramic with high voltage response and temperature stability, and a chemical composition of (0.98-x)((K) 0.49 Na 0.49 Li 0.02 (Nb) 0.96 Sb 0.04 )O3)-0.02((Bi 0.5 Na 0.5 (Zr) 0.8 Ti 0.2 )O3)-(CaZrO3) x +4 wt. % NaNbO3, 0≤ x ≤0.04, where x =0.01, the preparation method is basically the same as that of Comparative Example 1, the difference is that in step (1) 4.4299g Na2CO3, 5.6575g K2CO3, 21.3178g Nb2O5, 0.4013g Bi2O3, 0.5519g ZrO2, 0.1235g Li2CO3, 0.1724g CaCO3, 0.9742g Sb2O3, and 0.0550g TiO2 are selected as raw materials for textured piezoelectric ceramic materials.

[0069] Example 3:

[0070] This embodiment provides a potassium sodium niobate-based textured piezoelectric ceramic with high voltage response and temperature stability, and a chemical composition of (0.98-x)((K) 0.49 Na 0.49 Li 0.02 (Nb) 0.96 Sb 0.04 )O3)-0.02((Bi 0.5 Na 0.5 (Zr) 0.8 Ti 0.2 )O3)-(CaZrO3) x +4 wt. % NaNbO3, 0≤ x ≤0.04, where x=0.02, the preparation method is basically the same as that of Comparative Example 1, the difference is that in step (1) 4.3835g Na2CO3, 5.5970g K2CO3, 21.0899g Nb2O5, 0.4012g Bi2O3, 0.7638g ZrO2, 0.1221g Li2CO3, 0.3447g CaCO3, 0.9637g Sb2O3, and 0.0550g TiO2 are selected as raw materials for textured piezoelectric ceramic materials. The difference in step (7) is that the temperature is raised to 1180℃ at 3℃ / min without holding, and then lowered to 1080℃ at 10℃ / min and held for 10h.

[0071] Example 4:

[0072] This embodiment provides a potassium sodium niobate-based textured piezoelectric ceramic with high voltage response and temperature stability, and a chemical composition of (0.98-x)((K) 0.49 Na 0.49 Li 0.02 (Nb) 0.96 Sb 0.04 )O3)-0.02((Bi 0.5 Na 0.5 (Zr) 0.8 Ti 0.2 )O3)-(CaZrO3) x +4 wt. % NaNbO3, 0≤ x ≤0.04, where x =0.03, the preparation method is basically the same as that of Comparative Example 1, the difference is that in step (1) 4.3372g Na2CO3, 5.5366g K2CO3, 20.8623g Nb2O5, 0.4010g Bi2O3, 0.9756g ZrO2, 0.1208g Li2CO3, 0.5168g CaCO3, 0.9533g Sb2O3, and 0.0550g TiO2 are selected as raw materials for textured piezoelectric ceramic materials. The difference in step (7) is that the temperature is raised to 1180℃ at 3℃ / min without holding, and then lowered to 1080℃ at 10℃ / min and held for 10h.

[0073] Example 5

[0074] This embodiment provides a potassium sodium niobate-based textured piezoelectric ceramic with high voltage response and temperature stability, and a chemical composition of (0.98-x)((K) 0.49 Na 0.49 Li 0.02 (Nb) 0.96 Sb 0.04 )O3)-0.02((Bi0.5 Na 0.5 (Zr) 0.8 Ti 0.2 )O3)-(CaZrO3) x +4 wt. % NaNbO3, 0≤ x ≤0.04, where x =0.04, the preparation method is basically the same as that of Comparative Example 1, the difference is that in step (1) 4.2908g Na2CO3, 5.4762g K2CO3, 20.6348g Nb2O5, 0.4009g Bi2O3, 1.1872g ZrO2, 0.1195g Li2CO3, 0.6888g CaCO3, 0.9429g Sb2O3, and 0.0550g TiO2 are selected as raw materials for textured piezoelectric ceramic materials. The difference in step (7) is that the temperature is increased to 1200℃ at 3℃ / min without holding, and then decreased to 1100℃ at 10℃ / min and held for 10h. Each component has a corresponding optimal sintering temperature, and the spectral data are all based on the optimal sintered sample of each component.

[0075] like Figure 1 As shown, using the Lotgering factor f The texture of the potassium sodium niobate-based textured piezoelectric ceramics with high voltage response and temperature stability in Examples 2 to 5 was calculated. The texture of the potassium sodium niobate-based textured piezoelectric ceramic in Comparative Example 1 with high voltage response and temperature stability was also calculated. <001> C The direction exhibits a high degree of texture (f=92.8%). Example 2's potassium sodium niobate-based textured piezoelectric ceramic, with its high voltage response and temperature stability, demonstrates this. <001> C The direction exhibits a high degree of texture (f=95.7%). Example 3, a potassium sodium niobate-based textured piezoelectric ceramic with high voltage response and temperature stability, demonstrates this. <001> C The direction exhibits a high degree of texture (f=94.2%). Example 4, a potassium sodium niobate-based textured piezoelectric ceramic with high voltage response and temperature stability, demonstrates this. <001> C The direction exhibits a high degree of texture (f=98.2%). Example 5, a potassium sodium niobate-based textured piezoelectric ceramic with high voltage response and temperature stability, demonstrates this. <001> C The direction exhibits a high degree of texture (f=94.1%). Furthermore, based on the ratio of peak heights of (002) and (200), the phase structure of the ceramic can be determined. Figure 1 It can be concluded that Comparative Example 1, Examples 2, 3, 4, and 5 all involve the coexistence of orthogonal tetragonal phases.

[0076] like Figure 2As shown, observation of the free surface of the ceramic in Example 4 reveals that after the addition of the sheet template, the grains grow in an oriented manner, with a grain size of approximately 20-50 μm.

[0077] Example 4 shows that the potassium sodium niobate-based textured piezoelectric ceramic maintains a stable dielectric constant from room temperature to the Curie temperature range, which explains its excellent temperature stability. Furthermore, Example 4 exhibits a highly saturated hysteresis loop and significant remanent and saturable polarization, thus demonstrating excellent ferroelectric / piezoelectric properties, with a piezoelectric coefficient... d 33 It is 520 pC / N.

[0078] The piezoelectric coefficient of Example 4 initially remained stable and then decreased with increasing temperature, exhibiting excellent temperature stability with a change rate of 3.8% within the temperature range of 25-200 °C. In contrast, the piezoelectric coefficient of Comparative Example 1 changed by 10.8% within the same temperature range, Example 2 by 5.3%, Example 3 by 5.8%, and Example 5 by 6.7%.

[0079] Given the stability of the piezoelectric coefficient mentioned above, a curve showing the inverse piezoelectric coefficient versus temperature in Example 4 has been added, as shown below. Figure 4 As shown in Figure 5, the unipolar strain of Example 4 first remains stable and then decreases with increasing temperature. Correspondingly, the inverse piezoelectric coefficient can be calculated to be 525 pm / V at room temperature, and the rate of change is 4.2% in the temperature range of 25-200 ℃, showing excellent temperature stability.

[0080] like Figure 6 The figure shown is a statistical graph of the piezoelectric coefficient and Curie temperature of the piezoelectric ceramics in Comparative Example 1 and Examples 2 to 5 of the present invention.

[0081] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A potassium sodium niobate-based textured piezoelectric ceramic with high voltage response and temperature stability, characterized in that, The general chemical formula of the textured piezoelectric ceramic is (0.98-x)((K)). 0.49 Na 0.49 Li 0.02 (Nb) 0.96 Sb 0.04 )O3)- 0.02((Bi 0.5 Na 0.5 (Zr) 0.8 Ti 0.2 )O3)- x CaZrO3+4 wt. % NaNbO3, 0.02≤ x ≤0.04; The preparation method of the textured piezoelectric ceramic includes the following steps: (1) Solid-phase synthesis method: Sodium carbonate, potassium carbonate, niobium oxide, lithium carbonate, calcium carbonate, zirconium oxide, antimony oxide, titanium oxide and bismuth oxide are selected, weighed according to their chemical composition, ball-milled to obtain powder base material; (2) Two-step molten salt method combined with separation method: First, bismuth oxide, potassium carbonate, niobium oxide and molten salt are used for synthesis, separation and filtration are performed to obtain a sheet-like precursor. Second, the sheet-like precursor, potassium carbonate and molten salt are used for synthesis, separation and filtration are performed to obtain a sodium niobate sheet template. (3) Template grain growth method: The powder base material obtained in step (1) and the sheet template obtained in step (2) are respectively added to the mixed solvent, dispersant, plasticizer and binder and mixed to obtain the casting slurry; (4) Casting process: The cast slurry obtained in step (3) is cast and then dried to form a thick film; (5) Hot pressing process: The thick film obtained in step (4) is stacked layer by layer and finally hot pressed to form a ceramic green body; (6) Debinding process: Debinding the ceramic green body obtained in step (5) to obtain the ceramic body; (7) Two-step sintering process: The ceramic blank obtained in step (6) is sintered in two steps. After cooling to room temperature in the furnace, it is polished with sandpaper of different grits until a certain thickness is obtained to obtain ceramic sheets. (8) Silver firing process: The ceramic sheet obtained in step (7) is coated with silver paste and fired to obtain a ceramic with silver electrode; (9) Polarization process: The ceramic coated with silver electrodes obtained in step (8) is polarized to obtain potassium sodium niobate-based textured piezoelectric ceramic with high voltage response and temperature stability. Step (7) involves a two-step sintering process, which includes a first step and a second step. The first step involves a heating rate of 2-5 ℃ / min and a heating temperature of 1160-1200 ℃, without holding the temperature. The second step involves a cooling rate of 10-15 ℃ / min and a cooling temperature of 1060-1100 ℃, with a holding time of 8-12 h.

2. The method for preparing a potassium sodium niobate-based textured piezoelectric ceramic with high voltage response and temperature stability as described in claim 1, characterized in that, The method includes the following steps: (1) Solid-phase synthesis method: Sodium carbonate, potassium carbonate, niobium oxide, lithium carbonate, calcium carbonate, zirconium oxide, antimony oxide, titanium oxide and bismuth oxide are selected, weighed according to their chemical composition, ball-milled to obtain powder base material; (2) Two-step molten salt method combined with separation method: First, bismuth oxide, potassium carbonate, niobium oxide and molten salt are used for synthesis, separation and filtration are performed to obtain a sheet-like precursor. Second, the sheet-like precursor, potassium carbonate and molten salt are used for synthesis, separation and filtration are performed to obtain a sodium niobate sheet template. (3) Template grain growth method: The powder base material obtained in step (1) and the sheet template obtained in step (2) are respectively added to the mixed solvent, dispersant, plasticizer and binder and mixed to obtain the casting slurry; (4) Casting process: The cast slurry obtained in step (3) is cast and then dried to form a thick film; (5) Hot pressing process: The thick film obtained in step (4) is stacked layer by layer and finally hot pressed to form a ceramic green body; (6) Debinding process: Debinding the ceramic green body obtained in step (5) to obtain the ceramic body; (7) Two-step sintering process: The ceramic blank obtained in step (6) is sintered in two steps. After cooling to room temperature in the furnace, it is polished with sandpaper of different grits until a certain thickness is obtained to obtain ceramic sheets. (8) Silver firing process: The ceramic sheet obtained in step (7) is coated with silver paste and fired to obtain a ceramic with silver electrode; (9) Polarization process: The ceramic coated with silver electrodes obtained in step (8) is polarized to obtain potassium sodium niobate-based textured piezoelectric ceramic with high voltage response and temperature stability.

3. The method for preparing a potassium sodium niobate-based textured piezoelectric ceramic with high voltage response and temperature stability according to claim 2, characterized in that, In step (1), ethanol is used as the ball milling medium, and the ball milling time is 12-24 h.

4. The method for preparing a potassium sodium niobate-based textured piezoelectric ceramic with high voltage response and temperature stability according to claim 2, characterized in that, In step (2), sodium chloride is used as the molten salt, the mass ratio of raw materials to molten salt is 1:1.1, the holding time is 2 h, the molar ratio of bismuth oxide, potassium carbonate and niobium oxide in the first step is 6.5:7:10, the melting temperature is 1050-1100 ℃, and the molar ratio of the sheet precursor and potassium carbonate in the second step is 1:1.75, the melting temperature is 970-990 ℃; In step (2), a separation reagent is used for separation. The separation reagent is sodium tripolyphosphate, and the amount of separation reagent added is 8-10% of the total mass of the molten salt mixture in the corresponding first or second step. wt. The stirring speed was 600-800 rpm and the stirring time was 5-10 min.

5. The method for preparing a potassium sodium niobate-based textured piezoelectric ceramic with high voltage response and temperature stability according to claim 2, characterized in that, In step (3), the mixed solvent is methyl ethyl ketone and ethanol, the dispersant is trioleic acid glyceride, the plasticizer is polyethylene glycol and dibutyl phthalate, and the binder is polyvinyl butyral. The mass ratio of powder base material, sheet template and mixed solvent, dispersant, plasticizer and binder is (8.4-9.6):(0.3-0.4):(12-16):(0.3-0.35):(0.75-1.0):(1.1-1.2). The mixing speed is 16-18 r / min and the time is 6-8 h.

6. The method for preparing a potassium sodium niobate-based textured piezoelectric ceramic with high voltage response and temperature stability according to claim 2, characterized in that, In step (4), a casting knife is used for casting, and the casting knife moving speed is 28-30 cm / min.

7. The method for preparing a potassium sodium niobate-based textured piezoelectric ceramic with high voltage response and temperature stability according to claim 2, characterized in that, In step (6), the glue discharge temperature is 550-600 ℃ and the heat preservation time is 10-12 h.

8. The method for preparing a potassium sodium niobate-based textured piezoelectric ceramic with high voltage response and temperature stability according to claim 2, characterized in that, In step (8), the diameter of the silver paste is 4-6 mm, the firing temperature is 550-600 ℃, and the holding time is 20-30 min.

9. The method for preparing a potassium sodium niobate-based textured piezoelectric ceramic with high voltage response and temperature stability according to claim 2, characterized in that, In step (9), the polarization electric field is 2-4 kV / mm and the time is 20-30 min.

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