CN113979748B - Potassium-sodium niobate-based leadless piezoelectric ceramic and preparation method thereof - Google Patents
Potassium-sodium niobate-based leadless piezoelectric ceramic and preparation method thereof Download PDFInfo
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Abstract
The invention discloses potassium sodium niobate based leadless piezoelectric ceramics and a preparation method thereof, wherein the chemical formula of the potassium sodium niobate based piezoelectric ceramics is (1-x) (K)0.5Na0.5)NbO3‑xBi(Li0.5Sb0.5)O3Wherein x is more than or equal to 0.01 and less than or equal to 0.20. According to the stoichiometric ratio (1-x) (K)0.5Na0.5)NbO3‑xBi(Li0.5Sb0.5)O3Weighing the dried raw materials, mixing, ball-milling and drying to obtain a mixed material; pre-burning the mixed material obtained in the step 1 at a high temperature to obtain pre-burned powder, and then performing secondary ball milling and drying to obtain secondary ball-milled powder; adding an adhesive into the secondary ball-milled powder for granulation, sieving, and performing compression molding to obtain a ceramic biscuit; removing the organic adhesive, and sintering at high temperature to obtain sintered ceramic; and (3) silver is coated on the surfaces of the two sides of the sintered ceramic and high-pressure polarization is carried out to prepare the potassium-sodium niobate based lead-free piezoelectric ceramic. The sintering characteristic of the potassium sodium niobate-based ceramic is effectively improved through component design and process optimization, volatilization of sodium and potassium elements is inhibited, porosity is reduced, the density of the ceramic is improved, the dielectric constant is further improved, the loss is reduced, and the comprehensive performance of the KNN-based ceramic is improved.
Description
Technical Field
The invention belongs to the technical field of piezoelectric ceramic devices. In particular to potassium sodium niobate based leadless piezoelectric ceramics and a preparation method thereof.
Background
With the rapid development of electronic information technology, people have higher and higher requirements on the performance, appearance and convenience of products of electronic products such as mobile phones, personal computers and the like, and high-performance capacitors are important electronic original devices for realizing market demands. For this reason, development of a novel ceramic capacitor having a high dielectric constant, a low loss and a wide temperature range is urgently required.
At present, lead-based electronic ceramic materials represented by lead zirconate titanate (PZT for short) occupy most of the application markets and are widely used for piezoelectric devices such as capacitors, sensors, actuators, transformers, ultrasonic transducers and the like. However, the lead content of the lead-based ceramic exceeding 50% causes great harm and pollution to human health and natural environment during the preparation, processing and use processes. Meanwhile, the limited lead resource reserves in China also become a restriction factor for limiting the future development of lead-based materials. Therefore, from the needs of human health and social sustainable development, the lead-free piezoelectric ceramics is a very important way to solve the problem. The research of lead-free piezoelectric ceramics has become one of the hot spots in the field of materials in the 21 st century.
Potassium sodium niobate (K)0.5Na0.5)NbO3KNN) has the same ABO as PZT3The perovskite-type piezoelectric ceramic has a high dielectric constant, a high piezoelectric constant, a high electromechanical coupling coefficient, low dielectric loss, a high Curie temperature (Tc), environmental friendliness and other excellent properties, and is one of the lead-free piezoelectric systems with the best comprehensive properties expected to replace lead-containing ceramic at present. Although the performance of the KNN ceramic is excellent, the KNN ceramic is difficult to prepare, and the ceramic sample prepared by the conventional sintering method has high porosity and low density; in addition, K, Na is seriously volatilized at high temperature, so that the sintered ceramic components are seriously deviated from the designed stoichiometric ratio, and high-voltage and electromechanical properties are difficult to obtain. The application of the KNN ceramic in the development of piezoelectric devices is greatly limited by the problems of the KNN ceramic, and the problems and difficulties to be solved are urgent at present.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides the high-performance potassium-sodium niobate-based lead-free piezoelectric ceramic and the preparation method thereof.
In order to achieve the purpose, the invention adopts the technical scheme that: a potassium sodium niobate based leadless piezoelectric ceramic with chemical formula of (1-x) (K)0.5Na0.5)NbO3-xBi(Li0.5Sb0.5)O3X represents a mole fraction, and x is more than or equal to 0.01 and less than or equal to 0.20; piezoelectric constant d33280 to 312pC/N, electromechanical coupling coefficient kpIs 0.493 to 0.556.
The preparation method of the potassium sodium niobate based leadless piezoelectric ceramic comprises the following steps:
step 1, according to the stoichiometric ratio (1-x) (K)0.5Na0.5)NbO3-xBi(Li0.5Sb0.5)O3Weighing dry sodium carbonate, potassium carbonate, niobium pentoxide, bismuth oxide, lithium carbonate and antimony trioxide, mixing, ball-milling and drying to obtain a mixed material;
step 2, pre-burning the mixed material obtained in the step 1 at a high temperature to obtain pre-burned powder;
step 3, performing secondary ball milling on the pre-sintered powder in the step 2 and drying to obtain secondary ball-milled powder;
step 4, adding an adhesive into the secondary ball-milling powder obtained in the step 3 for granulation, sieving, and then performing compression molding to obtain a ceramic biscuit blank;
step 5, removing the glue of the ceramic biscuit obtained in the step 4 in a muffle furnace, removing the organic binder, and sintering at high temperature to obtain sintered ceramic;
and 6, polishing the sintered ceramic obtained in the step 5, and then subjecting the surfaces on two sides of the sintered ceramic to silver and high-pressure polarization to prepare the potassium-sodium niobate-based lead-free piezoelectric ceramic.
In the step 2, the pre-sintering temperature of the mixed material is 700-900 ℃, and the temperature is kept for 1-6h at the pre-sintering temperature.
In the step 5, the temperature of high-temperature sintering is 950-.
The ceramic sintering process is carried out by adopting a burning-in method, and burning-in powder is selected from pre-sintering powder with the same composition as the ceramic.
In the step 1 and the step 3, a ball milling medium is absolute ethyl alcohol, and a grinding ball is made of zirconia; the mass ratio of the raw materials to the ball milling medium is 1:1.5-5, and the mass ratio of the raw materials to the ball milling medium is 1: 0.5-2; the ball milling time is 12-72 h.
The drying condition is that the temperature is 80-150 ℃ and the time is 2-24 h.
The organic adhesive is any one of PVA, PVB and Rhoplex solution, and the addition amount of the adhesive is 3-10% of the mass of the powder.
In the step 5, the conditions for degumming the blank embryo are as follows: the temperature is 550-.
High-voltage polarization conditions of the two side surfaces of the ceramic: the polarization temperature is 80-150 ℃, the polarization voltage is 1-10kV/mm, the polarization time is 10-60min, and the polarization process is carried out in silicone oil.
Compared with the prior art, the invention has at least the following beneficial effects:
the invention relates to a high-performance potassium sodium niobate based leadless piezoelectric ceramic with a chemical formula of (1-x) (K)0.5Na0.5)NbO3-xBi(Li0.5Sb0.5)O3X represents a mole fraction, and x is more than or equal to 0.01 and less than or equal to 0.20. At (1-x) (K)0.5Na0.5)NbO3-xBi(Li0.5Sb0.5)O3Bi at A site in the structure of solid solution3+Can enter into lattice to replace K+、Na+Li in the B-position+、Sb5+Into lattice to substitute Nb5+，Bi3+Low melting point, low sintering temperature, fine crystal grains and Li+、Sb5+The doping of the KNN piezoelectric ceramic can adjust the phase structure of the KNN piezoelectric ceramic, reduce the coercive field and improve the piezoelectric constant; the comprehensive performance of the KNN piezoelectric ceramic is improved in a donor doping mode.
In addition, the high-performance potassium sodium niobate-based lead-free piezoelectric ceramic provided by the invention does not use any lead-containing substance in the preparation process, so that the damage to the human health and the social environment caused by lead volatilization in the processing and using processes is removed; the invention effectively improves the sintering characteristic of the ceramic and inhibits sodium in the sintering process by carrying out component design and process improvement on the KNN ceramicAnd volatilizing potassium element. While the crystal grains are refined, the porosity of the ceramic is reduced, and the density is improved; further improve the comprehensive performance and piezoelectric constant d of the KNN-based ceramic33280 to 312pC/N, electromechanical coupling coefficient kpThe ceramic preparation process can reach 0.493-0.556, is carried out based on a traditional solid-phase sintering method, is simple in process, uniform in ceramic components, and is suitable for large-scale industrial production.
Drawings
FIG. 1 is an X-ray diffraction pattern of the present invention
FIG. 2 is a scanning electron microscope image of the present invention
Detailed Description
The technical solution of the present invention is explained in detail below.
The high-performance potassium sodium niobate-based lead-free piezoelectric ceramic has a chemical formula of (1-x) (K)0.5Na0.5)NbO3-xBi(Li0.5Sb0.5)O3X represents a mole fraction, and x is more than or equal to 0.01 and less than or equal to 0.20. At (1-x) (K)0.5Na0.5)NbO3-xBi(Li0.5Sb0.5)O3Bi at A site in the structure of solid solution3+Can enter into lattice to replace K+、Na+Li in the B-position+、Sb5+Into lattice to substitute Nb5+，Bi3+Low melting point, low sintering temperature, fine crystal grains and Li+、Sb5+The doping of the KNN piezoelectric ceramic can adjust the phase structure of the KNN piezoelectric ceramic, reduce the coercive field and improve the piezoelectric constant; the comprehensive performance of the KNN piezoelectric ceramic is improved by means of donor doping, and refer to fig. 1 and fig. 2.
The invention relates to a high-performance potassium sodium niobate based leadless piezoelectric ceramic with a chemical formula of (1-x) (K)0.5Na0.5)NbO3-xBi(Li0.5Sb0.5)O3X represents a mole fraction, and x is more than or equal to 0.01 and less than or equal to 0.20. The preparation method comprises the following steps:
step 1, pre-drying raw materials of sodium carbonate, potassium carbonate, niobium pentoxide, bismuth oxide, lithium carbonate and antimony trioxide which are analytically pure;
step 2, according to (1-x) (K)0.5Na0.5)NbO3-xBi(Li0.5Sb0.5)O3Weighing the drying raw materials according to a stoichiometric ratio, mixing, ball-milling and drying to obtain a mixed material A;
step 3, pre-burning the mixed material A to obtain pre-burned powder B;
step 4, performing secondary ball milling and drying on the powder synthesized after the pre-sintering to obtain secondary ball-milled powder C;
step 5, adding an adhesive into the secondary ball-milling powder C, granulating, and then pressing and forming to obtain a ceramic biscuit D;
step 6, placing the biscuit in a muffle furnace for degumming to remove the organic adhesive, and obtaining a peptized biscuit E;
step 7, placing the discharged gel element blank E in a high-temperature furnace for high-temperature sintering to obtain sintered ceramic F;
and 7, polishing the surfaces of two sides of the sintered ceramic sample, and polarizing by silver and high pressure to prepare the potassium-sodium niobate based lead-free piezoelectric ceramic.
Preferably, in the above steps, the ball milling medium is absolute ethyl alcohol, and the mass ratio of the raw material to the absolute ethyl alcohol is 1: 0.5-2; the grinding ball is a zirconia ball, and the mass ratio of the raw materials to the grinding ball is 1: 1.5-5; the ball milling time is 12-72 h;
preferably, in the above step, the material drying conditions are as follows: the temperature is 80-150 ℃, the time is 24-48h, and the drying equipment is a vacuum drying oven;
preferably, in the step, the pre-sintering temperature of the mixed material A is 700-;
preferably, the organic binder is any one of PVA, PVB and Rhoplex solution, and the amount of the binder is 3-10% of the mass of the ceramic powder;
preferably, the ceramic biscuit D rubber discharge conditions in the step 6 are as follows: the temperature is 550-.
Preferably, the sintering temperature of the ceramic biscuit E is 950-1200 ℃, and the heat preservation time is 2-10 h.
In the process, the ceramic sintering process is carried out by adopting a buried burning method, and the buried burning powder is pre-burning powder with the same components.
Preferably, the polarization conditions of the sintered ceramic sample are: the polarization temperature is 80-150 ℃, the polarization voltage is 1-10kV/mm, the polarization time is 10-60min, and the polarization process is finished in silicone oil.
Preferably, the piezoelectric constant d of the ceramic33280 to 312pC/N, electromechanical coupling coefficient kpCan reach 0.493-0.556.
The invention will now be described in detail by way of specific examples, which are given for illustrative purposes only and are not intended to limit the invention.
Example 1
Step 1, drying raw materials such as sodium carbonate, potassium carbonate, niobium pentoxide, bismuth oxide, lithium carbonate, antimony trioxide and the like in an oven at 120 ℃ for 24 hours in advance.
Step 2, the material obtained in the step 1 is treated according to the chemical formula 0.96 (K)0.5Na0.5)NbO3-0.04Bi(Li0.5Sb0.5)O3And weighing, mixing and ball-milling according to the stoichiometric ratio, and drying after the ball-milling is finished to obtain a mixed material A. Wherein the mass ratio of the raw materials to the grinding balls is 1: 1.5; the mass ratio of the raw materials to the absolute ethyl alcohol is 1:1.0, the ball milling time is 36h, and the drying temperature is 120 ℃.
And 3, placing the dried mixed material A into a crucible, and placing the crucible in a muffle furnace for pre-burning to obtain pre-burned powder B. Presintering temperature is 800 ℃, and heat preservation time is 4 h.
And 4, performing secondary ball milling on the pre-sintered material for 48 hours, adding 6% of adhesive PVA (polyvinyl alcohol) in mass ratio for granulation, sieving by using 80-mesh and 120-mesh sample sieves, and pressing powder with the particle size in the middle of the area into a thin wafer blank D by using single-shaft pressurization under 6 Mpa.
And 5, putting the biscuit sample D into a muffle furnace, heating to 600 ℃ at the heating rate of 0.5 ℃/min, preserving heat for 8h, naturally cooling, and removing organic matters and water in the biscuit to obtain the biscuit E after degumming.
Step 6, completely embedding the biscuit E by using pre-sintering material powder with the same components, then covering a crucible and placing the crucible on a zirconium plate; heating to 1000 ℃ at the heating rate of 10 ℃/min and preserving heat for 4h to prepare a sintered ceramic sample E;
and 7, grinding and polishing the surfaces of two sides of the ceramic sample E by 3000-mesh sand paper, ultrasonically cleaning, drying, coating silver, and placing in silicone oil at 80 ℃ for polarization with a polarization electric field of 1kV/mm for 30min to obtain the potassium-sodium niobate-based lead-free piezoelectric ceramic.
The piezoelectric constant d of the ceramic33At 312pC/N, an electromechanical coupling coefficient kpIs 0.570.
Example 2
Step 1, drying raw materials such as sodium carbonate, potassium carbonate, niobium pentoxide, bismuth oxide, lithium carbonate, antimony trioxide and the like in an oven at 100 ℃ for 5 hours in advance.
Step 2, the material obtained in the step 1 is treated according to the chemical formula 0.99 (K)0.5Na0.5)NbO3-0.01Bi(Li0.5Sb0.5)O3And weighing, mixing and ball-milling according to the stoichiometric ratio, and drying after the ball-milling is finished to obtain a mixed material A. Wherein the mass ratio of the raw materials to the grinding balls is 1: 2.0; the mass ratio of the raw materials to the absolute ethyl alcohol is 1:0.5, the ball milling time is 24h, and the drying temperature is 100 ℃.
And 3, placing the dried mixed material A into a crucible, and placing the crucible in a muffle furnace for presintering to obtain presintering powder B. Presintering temperature is 850 ℃, and heat preservation time is 3 h.
And 4, performing secondary ball milling on the pre-sintered material for 36 hours, adding a binder PVA (polyvinyl alcohol) with the mass ratio of 5% for granulation, sieving with 80-mesh and 120-mesh sample sieves, and pressing powder with the particle size in the middle of the area into a thin wafer blank D by uniaxial pressing at 6 MPa.
And 5, putting the biscuit sample D into a muffle furnace, heating to 550 ℃ at the heating rate of 1.0 ℃/min, preserving heat for 4h, naturally cooling, and removing organic matters and water in the biscuit to obtain the biscuit E after degumming.
Step 6, completely embedding the blank E by using pre-sintered material powder with the same components, then covering a crucible and placing the crucible on a zirconium plate; heating to 1100 ℃ at the heating rate of 5 ℃/min and preserving heat for 2h to prepare a sintered ceramic sample E;
and 7, grinding and polishing the surfaces of two sides of the ceramic sample E by using 3000-mesh abrasive paper, ultrasonically cleaning and drying, then coating silver on the surface, placing the ceramic sample E in silicone oil at 120 ℃ for polarization, and preparing the potassium-sodium niobate-based lead-free piezoelectric ceramic, wherein the polarization electric field is 5kV/mm, and the polarization time is 15 min.
The piezoelectric constant d of the ceramic33At 306pC/N, an electromechanical coupling coefficient kpIs 0.575.
Example 3
Step 1, drying raw materials such as sodium carbonate, potassium carbonate, niobium pentoxide, bismuth oxide, lithium carbonate, antimony trioxide and the like in an oven at 150 ℃ for 12 hours in advance.
Step 2, the material obtained in the step 1 is treated according to the chemical formula of 0.85 (K)0.5Na0.5)NbO3-0.15Bi(Li0.5Sb0.5)O3And weighing, mixing and ball-milling according to the stoichiometric ratio, and drying after the ball-milling is finished to obtain a mixed material A. Wherein the mass ratio of the raw materials to the grinding balls is 1: 3.0; the mass ratio of the raw materials to the absolute ethyl alcohol is 1:1.5, the ball milling time is 24 hours, and the drying temperature is 100 ℃.
And 3, placing the dried mixed material A into a crucible, and placing the crucible in a muffle furnace for pre-burning to obtain pre-burned powder B. The presintering temperature is 875 ℃, and the heat preservation time is 2 hours.
And 4, performing secondary ball milling on the pre-sintered material for 48 hours, adding a binder PVA (polyvinyl alcohol) with the mass ratio of 5% for granulation, sieving with 80-mesh and 120-mesh sample sieves, and pressing powder with the particle size in the middle of the area into a thin wafer blank D by uniaxial pressing at 6 MPa.
And 5, putting the element blank sample D into a muffle furnace, heating to 650 ℃ at the heating rate of 3 ℃/min, preserving heat for 4h, naturally cooling, and removing organic matters and water in the element blank to obtain the element blank E after the rubber is removed.
Step 6, completely embedding the blank E by using pre-sintered material powder with the same components, then covering a crucible and placing the crucible on a zirconium plate; heating to 1200 ℃ at the heating rate of 3 ℃/min and preserving heat for 5 hours to prepare a sintered ceramic sample E;
and 7, grinding and polishing the surfaces of two sides of the ceramic sample E by using 3000-mesh abrasive paper, ultrasonically cleaning and drying, then coating silver on the surface, placing the ceramic sample E in silicone oil at 100 ℃ for polarization, and preparing the potassium-sodium niobate-based lead-free piezoelectric ceramic, wherein the polarization electric field is 5kV/mm, and the polarization time is 30 min.
The piezoelectric constant d of the ceramic33280pC/N, electromechanical coupling coefficient kpIs 0.493.
Example 4
Step 1, drying raw materials such as sodium carbonate, potassium carbonate, niobium pentoxide, bismuth oxide, lithium carbonate, antimony trioxide and the like in an oven at 80 ℃ for 2 hours in advance.
Step 2, the material obtained in the step 1 is treated according to the chemical formula of 0.92 (K)0.5Na0.5)NbO3-0.08Bi(Li0.5Sb0.5)O3And weighing, mixing and ball-milling according to the stoichiometric ratio, and drying after the ball-milling is finished to obtain a mixed material A. Wherein the mass ratio of the raw materials to the grinding balls is 1: 1.5; the mass ratio of the raw materials to the absolute ethyl alcohol is 1:0.5, the ball milling time is 12h, and the drying temperature is 80 ℃.
Step 3, placing the dried mixed material A into a crucible, and placing the crucible in a muffle furnace for pre-burning to obtain pre-burned powder B; the presintering temperature is 700 ℃, and the heat preservation time is 1.5 h.
And 4, performing secondary ball milling on the pre-sintered material for 12 hours, adding 3% of adhesive PVA (polyvinyl alcohol) for granulation, sieving by using 80-mesh and 120-mesh sample sieves, and pressing powder with the particle size in the middle of the area into a thin wafer blank D by using a single shaft under the pressure of 6 MPa.
And 5, putting the biscuit sample D into a muffle furnace, heating to 600 ℃ at the heating rate of 2.5 ℃/min, preserving heat for 12h, then naturally cooling, and removing organic matters and water in the biscuit to obtain the biscuit E after degumming.
Step 6, completely embedding the biscuit E by using pre-sintering material powder with the same components, then covering a crucible and placing the crucible on a zirconium plate; heating to 1050 ℃ at the heating rate of 3 ℃/min and preserving heat for 4h to prepare a sintered ceramic sample E;
and 7, grinding and polishing the surfaces of two sides of the ceramic sample E by using 3000-mesh abrasive paper, ultrasonically cleaning and drying, then coating silver on the surface, placing the ceramic sample E in silicone oil at 80 ℃ for polarization, and preparing the potassium-sodium niobate-based lead-free piezoelectric ceramic, wherein the polarization electric field is 3kV/mm, and the polarization time is 60 min.
The piezoelectric constant d of the ceramic33287pC/N, electromechanical coupling coefficient kpAnd was 0.536.
Example 5
Step 1, drying raw materials such as sodium carbonate, potassium carbonate, niobium pentoxide, bismuth oxide, lithium carbonate, antimony trioxide and the like in an oven at 110 ℃ for 20 hours in advance.
Step 2, the material obtained in the step 1 is treated according to the chemical formula of 0.89 (K)0.5Na0.5)NbO3-0.11Bi(Li0.5Sb0.5)O3And weighing, mixing and ball-milling according to the stoichiometric ratio, and drying after the ball-milling is finished to obtain a mixed material A. Wherein the mass ratio of the raw materials to the grinding balls is 1: 5.0; the mass ratio of the raw materials to the absolute ethyl alcohol is 1:0.8, the ball milling time is 48h, and the drying temperature is 120 ℃.
Step 3, placing the dried mixed material A into a crucible, and placing the crucible in a muffle furnace for pre-burning to obtain pre-burned powder B; presintering temperature is 900 ℃, and heat preservation time is 4.5 h.
And 4, performing secondary ball milling on the pre-sintered material for 36 hours, adding 10% of adhesive PVA (polyvinyl alcohol) for granulation, sieving by using 80-mesh and 120-mesh sample sieves, and pressing powder with the particle size in the middle of the area into a thin wafer blank D by using a single shaft under the pressure of 6 MPa.
And 5, putting the element blank sample D into a muffle furnace, heating to 650 ℃ at the heating rate of 5 ℃/min, preserving heat for 5h, naturally cooling, and removing organic matters and water in the element blank to obtain the element blank E after the rubber is removed.
Step 6, completely embedding the biscuit E by using pre-sintering material powder with the same components, then covering a crucible and placing the crucible on a zirconium plate; heating to 950 ℃ at the heating rate of 5 ℃/min and preserving heat for 10 hours to prepare a sintered ceramic sample E;
and 7, grinding and polishing the surfaces of two sides of the ceramic sample E by using 3000-mesh abrasive paper, ultrasonically cleaning and drying, then coating silver on the surface, placing the ceramic sample E in silicone oil at 100 ℃ for polarization, and preparing the potassium-sodium niobate-based lead-free piezoelectric ceramic, wherein the polarization electric field is 10kV/mm, and the polarization time is 45 min.
The piezoelectric constant d of the ceramic33At 312pC/N, an electromechanical coupling coefficient kpIs 0.509.
Example 6
Step 1, drying raw materials such as sodium carbonate, potassium carbonate, niobium pentoxide, bismuth oxide, lithium carbonate, antimony trioxide and the like in an oven at 100 ℃ for 15 hours in advance.
Step 2, the material obtained in the step 1 is treated according to the chemical formula of 0.80 (K)0.5Na0.5)NbO3-0.20Bi(Li0.5Sb0.5)O3And weighing, mixing and ball-milling according to the stoichiometric ratio, and drying after the ball-milling is finished to obtain a mixed material A. Wherein the raw materials are as followsThe mass ratio of the grinding balls is 1: 2.0; the mass ratio of the raw materials to the absolute ethyl alcohol is 1:2.0, the ball milling time is 72 hours, and the drying temperature is 150 ℃.
Step 3, placing the dried mixed material A into a crucible, and placing the crucible in a muffle furnace for pre-burning to obtain pre-burned powder B; the presintering temperature is 750 ℃, and the heat preservation time is 6 h.
And 4, performing secondary ball milling on the pre-sintered material for 72 hours, adding 8% of adhesive PVA (polyvinyl alcohol) in mass ratio for granulation, screening by 80-mesh and 120-mesh sample sieves, and pressing powder with the particle size in the middle of the area into a thin wafer blank D by uniaxial pressurization at 6 Mpa.
And 5, putting the biscuit sample D into a muffle furnace, heating to 580 ℃ at the heating rate of 0.2 ℃/min, preserving heat for 24 hours, then naturally cooling, and removing organic matters and water in the biscuit to obtain the biscuit E after rubber removal.
Step 6, completely embedding the biscuit E by using pre-sintering material powder with the same components, then covering a crucible and placing the crucible on a zirconium plate; heating to 1150 ℃ at the heating rate of 10 ℃/min and preserving heat for 8 hours to prepare a sintered ceramic sample E;
and 7, grinding and polishing the surfaces of two sides of the ceramic sample E by using 3000-mesh abrasive paper, ultrasonically cleaning and drying, then coating silver on the surface, placing the surface in silicon oil at 110 ℃ for polarization, and preparing the potassium-sodium niobate-based lead-free piezoelectric ceramic, wherein the polarization electric field is 6kV/mm, and the polarization time is 20 min.
The piezoelectric constant d of the ceramic33292pC/N, electromechanical coupling coefficient kpIs 0.570.
Claims (10)
1. The potassium-sodium niobate-based leadless piezoelectric ceramic is characterized in that the chemical formula is (1-x) (K)0.5Na0.5)NbO3-xBi(Li0.5Sb0.5)O3X represents a mole fraction, and x is more than or equal to 0.01 and less than or equal to 0.20; piezoelectric constant d33280 to 312pC/N, electromechanical coupling coefficient kp0.493 to 0.556; is in solid solution structure.
2. The method for producing a potassium sodium niobate-based lead-free piezoelectric ceramic as claimed in claim 1, comprising the steps of:
step 1, according to the stoichiometric ratio (1-x) (K)0.5Na0.5)NbO3-xBi(Li0.5Sb0.5)O3Weighing dried sodium carbonate, potassium carbonate, niobium pentoxide, bismuth oxide, lithium carbonate and antimony trioxide, mixing, ball-milling and drying to obtain a mixed material;
step 2, pre-burning the mixed material obtained in the step 1 at a high temperature to obtain pre-burned powder;
step 3, performing secondary ball milling on the pre-sintered powder in the step 2 and drying to obtain secondary ball-milled powder;
step 4, adding an adhesive into the secondary ball-milling powder obtained in the step 3 for granulation, sieving, and then performing compression molding to obtain a ceramic biscuit blank;
step 5, removing the organic adhesive from the ceramic biscuit obtained in the step 4, and then sintering at high temperature to obtain sintered ceramic;
and 6, polishing the sintered ceramic obtained in the step 5, and then subjecting the surfaces on two sides of the sintered ceramic to silver and high-pressure polarization to prepare the potassium-sodium niobate-based lead-free piezoelectric ceramic.
3. The preparation method as claimed in claim 2, wherein in step 2, the pre-sintering temperature of the mixed material is 700-900 ℃, and the temperature is maintained for 1-6h at the pre-sintering temperature.
4. The method as claimed in claim 2, wherein the temperature of the high-temperature sintering in step 5 is 950-1200 ℃, and the holding time at the sintering temperature is 2-10 h.
5. The method of claim 2, wherein the ceramic sintering process is performed by a buried burning method, and the buried burning powder is selected from a pre-burning powder material having the same composition as the ceramic.
6. The preparation method according to claim 2, wherein in step 1 and step 3, the ball milling medium is absolute ethyl alcohol, and the material of the grinding balls is zirconia; the mass ratio of the raw materials to the ball milling medium is 1:1.5-5, and the mass ratio of the raw materials to the ball milling medium is 1: 0.5-2; the ball milling time is 12-72 h.
7. The method according to claim 2, wherein the drying is carried out at a temperature of 80-150 ℃ for 2-24 hours.
8. The method according to claim 2, wherein the organic binder is any one of PVA, PVB and Rhoplex solution, and the amount of the binder added is 3-10% by mass of the powder.
9. The method according to claim 2, wherein in step 5, the conditions for the degumming of the germ are as follows: the temperature is 550-.
10. The method of claim 2, wherein the high-voltage polarization conditions of the both side surfaces of the ceramic are: the polarization temperature is 80-150 ℃, the polarization voltage is 1-10kV/mm, the polarization time is 10-60min, and the polarization process is carried out in silicone oil.
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