Potassium sodium bismuth niobate high-temperature piezoelectric ceramic material as well as preparation method and application thereof

Abstract

The invention provides a bismuth sodium potassium niobate high-temperature piezoelectric ceramic material and a preparation method and application thereof, the chemical formula of the material is Na < 0.25 > K < 0.25 > Bi < 2.5 + x > Nb < 2 > O < 9 + 3x / 2 >, x is more than or equal to-0.10 and less than 0, and x is molar percentage. Compared with the prior art, lattice distortion is generated on a perovskite-like layer of the sodium-potassium bismuth niobate high-temperature piezoelectric ceramic in a bismuth deficiency manner, the oxygen vacancy defect is reduced, the piezoelectric property of the sodium-potassium bismuth niobate is further improved, and the lead-free high-temperature piezoelectric ceramic with a large piezoelectric coefficient and excellent stability is obtained. According to the high-temperature piezoelectric ceramic material for the high-temperature piezoelectric vibration sensor, the high Curie temperature of the bismuth sodium potassium niobate high-temperature piezoelectric ceramic material is kept, and meanwhile, the piezoelectricity and the stability of the high-temperature piezoelectric ceramic material are synergistically improved. The application of the potassium sodium bismuth niobate high-temperature piezoelectric ceramic material in the high-temperature field is promoted.

Description

Technical Field

[0001] The present invention belongs to the technical field of piezoelectric ceramic materials, and in particular relates to a sodium potassium bismuth niobate high-temperature piezoelectric ceramic material and a preparation method and application thereof. Background Art

[0002] Piezoelectric ceramic materials are extremely important functional materials for realizing mechanical-electrical energy conversion and coupling. They are widely used in aerospace, electronic information, energy, advanced manufacturing, medical systems, weapons and equipment. In recent years, my country has developed rapidly in aerospace, energy, medical and space technology, and has put forward increasingly stringent requirements for key functional components. A common feature of piezoelectric devices used in some important fields, such as sonic logging instruments, ultrasonic motors, and high-temperature piezoelectric vibration sensors, is that the working environment temperature is high, which requires piezoelectric ceramic materials to work stably and reliably at high temperatures.

[0003] Piezoelectric ceramic materials are the core components of high-temperature vibration sensors. Bismuth layered structure sodium potassium bismuth niobate high-temperature piezoelectric ceramic materials are the preferred technical solution for 500℃ high-temperature piezoelectric vibration sensors due to their high Curie temperature (>650℃) and low dielectric loss. However, due to their small piezoelectric coefficient, poor stability, and large leakage current, they directly lead to the failure of related piezoelectric devices, which seriously restricts the practical application of sodium potassium bismuth niobate high-temperature piezoelectric ceramic materials in high-temperature environments. It is also one of the bottlenecks that have not yet been broken through in the development of 500℃ high-temperature piezoelectric vibration sensors in my country.

[0004] At present, the piezoelectricity of sodium potassium bismuth niobate high-temperature piezoelectric ceramic materials is usually improved by ion doping to optimize composition design and texturing process to control microstructure. 0.25 K 0.25 Bi 2.5 Piezoelectric coefficient d of Nb2O9 piezoelectric ceramics 33 It is increased to 28pC / N, but this method will greatly reduce the Curie temperature, which is only 580℃ (Journal of Alloys and Compounds, 2018, 765, 848-853); 3+ Doping substitution can increase the piezoelectric coefficient d of bismuth sodium potassium niobate high temperature piezoelectric ceramics. 33 The piezoelectric coefficient of bismuth layered high temperature piezoelectric ceramics can be increased to 21.8pC / N (Journal of the Chinese Ceramic Society, 2020, 48(7), 1090-1096). 33However, texturing processes such as hot pressing, hot forging, rapid plasma sintering, etc. are relatively complex and have poor repeatability.

[0005] Therefore, how to improve the piezoelectricity and stability of high-temperature potassium sodium bismuth niobate piezoelectric ceramic materials while ensuring their high Curie temperature is the research focus and key problem in the application field of high-temperature piezoelectric ceramics. Summary of the invention

[0006] The purpose of the present invention is to provide a bismuth sodium potassium niobate high-temperature piezoelectric ceramic material and a preparation method thereof. The present invention uses bismuth deficiency to produce lattice distortion in the perovskite-like layer of the bismuth sodium potassium niobate high-temperature piezoelectric ceramic, reduce oxygen vacancy defects, and thus improve the piezoelectric performance and stability of the bismuth sodium potassium niobate. The present invention adds a certain amount of sintering aid during the preparation to reduce the sintering temperature and improve the density of the ceramic. The bismuth sodium potassium niobate high-temperature piezoelectric ceramic with bismuth deficiency is prepared using a traditional solid phase reaction process, and its Curie temperature is above 650°C, with high piezoelectric performance and stability.

[0007] Another object of the present invention is to provide an application of sodium potassium bismuth niobate high-temperature piezoelectric ceramic material for high-temperature piezoelectric vibration sensors.

[0008] The specific technical solutions of the present invention are as follows:

[0009] The present invention provides a bismuth sodium potassium niobate high temperature piezoelectric ceramic material, the chemical formula of the bismuth sodium potassium niobate high temperature piezoelectric ceramic material is Na 0.25 K 0.25 Bi 2.5+x Nb2O 9+3x / 2 , wherein -0.10≤x<0, and x is the molar percentage.

[0010] Preferably, x=-0.05;

[0011] The piezoelectric coefficient d 33 The value is (15-20) pC / N, and the Curie temperature is above 650°C. The lattice distortion is formed by the bismuth deficiency, and the oxygen vacancy defects are reduced to optimize the electrical properties of the sodium potassium bismuth niobate high temperature piezoelectric ceramics.

[0012] Preferably, x=-0.05, which has the maximum piezoelectric coefficient.

[0013] The bismuth-deficient sodium potassium bismuth niobate high-temperature piezoelectric ceramic material of the present invention has excellent performance and a high Curie temperature, and is expected to be applied to high-temperature fields with temperatures above 500°C.

[0014] The invention provides a method for preparing a sodium potassium bismuth niobate high-temperature piezoelectric ceramic material, which comprises mixing, synthesis, molding, plastic removal and sintering.

[0015] The synthesis temperature is 700-900°C and the time is 1-3 hours;

[0016] The sintering temperature is 1000-1100° C. and the time is 1-3 hours;

[0017] Preferably, the preparation method comprises the following steps:

[0018] 1) mixing Na2CO3, K2CO3, Bi2O3 and Nb2O5 according to a stoichiometric ratio; the obtained mixture is subjected to a ball milling, synthesis and grinding to obtain a ceramic powder;

[0019] 2) ball-milling the ceramic powder obtained in step 1) for a second time, adding a binder to granulate after drying, pressing and molding after aging, and then heating and expelling the plastic to obtain a ceramic embryo;

[0020] 3) placing the ceramic blank obtained in step 2) into a high-temperature furnace, covering the ceramic blank with ceramic powder having the same composition as that in step 1), and then sintering to obtain a ceramic sheet;

[0021] 4) Processing the sintered ceramic sheet into a desired size, ultrasonically cleaning, screen printing silver, drying, and calcining the silver to obtain a sodium potassium bismuth acid high-temperature piezoelectric ceramic material.

[0022] In step 1), the first ball milling is performed by wet ball milling, and the mixture is ball milled for 3 to 8 hours according to a mass ratio of mixed material: ball milling medium: alcohol = 1: (1.8 to 2.2): (0.6 to 1.0), wherein the ball milling medium is agate balls.

[0023] In step 1), the synthesis conditions are: heating to 700-900°C at a heating rate not higher than 2°C / min, keeping the temperature for 1-3 hours, and cooling to room temperature in the furnace.

[0024] Furthermore, before the synthesis, the material after the first ball milling is dried, passed through a 40-mesh sieve, pressed into blocks at 5 MPa, and then synthesized.

[0025] In step 1), the grinding refers to passing through a 40-mesh sieve after grinding.

[0026] In step 2), the secondary ball milling adopts wet ball milling method for fine grinding, and the mass ratio of ceramic powder: ball milling medium: alcohol = 1: (1.8-2.2): (0.4-0.8) is finely ground for 3-8 hours, and the obtained ceramic powder has a small particle size and a narrow distribution, wherein the ball milling medium is agate ball.

[0027] In step 2), the binder is polyvinyl alcohol (PVA), and the amount of the binder added is 5-7wt.% of the weight of the ceramic powder;

[0028] In step 2), the aging refers to aging at room temperature for 24 hours.

[0029] In step 2), the heating and plastic removal conditions are: heating to 500-600° C. at a heating rate not higher than 2° C. / min, and keeping the temperature for 1-3 hours.

[0030] In step 3), the sintering conditions are to increase the temperature to 1000-1100° C. at a heating rate not higher than 2° C. / min, keep the temperature for 1-3 hours, and cool to room temperature in the furnace.

[0031] In step 4), the silver calcination condition is 700-800° C. and the temperature is kept at 5-40 minutes.

[0032] The invention provides an application of a bismuth sodium potassium niobate high-temperature piezoelectric ceramic material for a high-temperature piezoelectric vibration sensor.

[0033] The alcohol used in the present invention refers to anhydrous ethanol.

[0034] The present invention provides a method of using bismuth deficiency to produce lattice distortion in a perovskite-like layer of a bismuth sodium potassium niobate high-temperature piezoelectric ceramic, reduce oxygen vacancy defects, and thereby improve the piezoelectric properties of the bismuth sodium potassium niobate, thereby obtaining a lead-free high-temperature piezoelectric ceramic with a large piezoelectric coefficient and excellent stability to meet the requirements of high-temperature piezoelectric ceramic materials for high-temperature piezoelectric vibration sensors. The present invention synergistically improves the piezoelectricity and stability of the bismuth sodium potassium niobate high-temperature piezoelectric ceramic material while maintaining its high Curie temperature, thereby promoting the application of the bismuth sodium potassium niobate high-temperature piezoelectric ceramic material in high-temperature fields.

[0035] Current research focuses on improving the performance of piezoelectric ceramics by adding excess bismuth and Na 0.25 K 0.25 Bi 2.5 Nb2O9 ceramics have the same structure as CaBi2Nb2O9 ceramics. It is found that the piezoelectric properties of the ceramics can be greatly improved by adding bismuth. The optimal component CaBi 2.04 Piezoelectric coefficient d of Nb2O9 ceramics 33 can be increased to 15.1pC / N, while the d 33 Only 4.8 pC / N (Journal of the European Ceramic Society 42 (2022) 2772–2780). However, the effects and functions of bismuth deficiency have not been studied.

[0036] Compared with the existing technology, the piezoelectric properties and stability of sodium potassium bismuth niobate high-temperature piezoelectric ceramics can be effectively improved by regulating the microstructure through bismuth deficiency. At the same time, the Curie temperature is maintained above 650°C, providing a new way to prepare sodium potassium bismuth niobate-based high-temperature piezoelectric ceramics that meet the requirements of high-temperature piezoelectric vibration sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is the oxygen vacancy concentration test of ceramics with no bismuth deficiency and bismuth deficiency of -0.05;

[0038] Figure 2 Na prepared in the embodiment of the present invention 0.25 K 0.25 Bi 2.5+x Nb2O 9+3x / 2 Electrical properties of ceramics. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

[0041] If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the art or according to the product instructions.

[0042] Example 1

[0043] A method for preparing a bismuth sodium potassium niobate high-temperature piezoelectric ceramic material comprises the following steps:

[0044] 1) The bismuth-deficient Na 0.25 K 0.25 Bi 2.5+x Nb2O 9+3x / 2High temperature piezoelectric ceramics, wherein the molar ratio of the bismuth deficiency x is 0, -0.01, -0.03, -0.05, -0.07, -0.10, respectively, with Na2CO3, K2CO3, Bi2O3, Nb2O5 as raw materials, prepared according to the stoichiometric ratio, mixed by wet ball milling, mixed for 4 hours according to the mass ratio of mixed material: ball milling medium: alcohol = 1:2.0:0.75, so that the components are mixed evenly. After drying, pass through a 40-mesh sieve, press into large blocks at 5MPa, heat up to 800°C at a heating rate of 2°C / min, keep warm for 2 hours, grind, pass through a 40-mesh sieve, and obtain ceramic powder.

[0045] 2) The ceramic powders of step 1) are mixed by wet ball milling, and finely ground for 4 hours according to the mass ratio of ceramic powder: ball: alcohol = 1:2:0.65, and the finely ground ceramic powder is dried. Then, 6wt.% of PVA binder is added to the ceramic powder, granulated, pressed into blocks, aged at room temperature for 24 hours, passed through a 20-mesh sieve, pressed into blocks under a pressure of 2.0MPa, and then heated to 550°C at 2°C / min and kept for 2 hours to obtain a ceramic embryo.

[0046] 3) The ceramic blank is placed in an alumina crucible, and the temperature is raised to 1100°C at a heating rate of 2°C / min, and kept at this temperature for 2 hours. The ceramic sheet is obtained by cooling the ceramic blank in the furnace.

[0047] 4) The sintered ceramic sheet prepared in Example 1 was ground to a thickness of 0.5 mm, ultrasonically cleaned, dried, screen-printed with silver paste, and dried again. The temperature was raised to 750° C. at a heating rate of 2° C. / min, and the silver was sintered for 30 minutes to obtain the sodium potassium bismuth niobate high-temperature piezoelectric ceramic material.

[0048] The XRD data of the piezoelectric ceramic materials with different bismuth deficiencies prepared above are shown in Table 1.

[0049] Table 1Na 0.25 K 0.25 Bi 2.5+x Nb2O 9+3x / 2 Ceramic structure data

[0050]

[0051]

[0052] Through XRD testing, the results are shown in Table 1. It is found that the ratio of a / b (a and b represent unit cell parameters) indicating the degree of structural distortion increases due to bismuth deficiency, indicating that bismuth deficiency causes an increase in the degree of structural distortion. Through XPS testing, it is found that for the components with no bismuth deficiency and -0.05 bismuth deficiency, the oxygen vacancy concentrations are 0.30 and 0.25, respectively, indicating that bismuth deficiency does achieve the purpose of reducing oxygen vacancy defects.

[0053] The ceramic prepared in Example 1 was polarized at 180°C, 5-10 kV / mm, and polarized for 20 min. The electrical properties of the prepared ceramic were tested, and the results are shown in Figure 2 .

[0054] Figure 2 a in the figure is the radar chart of no deficiency and bismuth deficiency of -0.05, mainly from T c d 33 , ρ@600℃, tanδ@600℃, and oxygen vacancy concentration. The larger the area surrounded by the five elements, the better the comprehensive performance. It can be seen that the bismuth deficiency can greatly improve the Na 0.25 K 0.25 Bi 2.5 Comprehensive properties of Nb2O9 ceramics.

[0055] Thermal stability is an important factor to be considered in practical applications of piezoelectric ceramics. 0.25 K 0.25 Bi 2.5 The thermal stability of Nb2O9 under bismuth deficiency conditions, all samples were annealed, such as Figure 2 As shown in b. The results show that bismuth deficiency can not only improve d 33 , and can improve its thermal stability, especially the component with bismuth deficiency of -0.05. When the annealing temperature reaches 600℃, d 33 Slightly decreased, d 33 Remains at 97% of the initial value.

[0056] Comparative Example 1

[0057] The preparation method of sodium potassium bismuth niobate high temperature piezoelectric ceramic material of Example 1 was followed, except that the molar ratio of the excess bismuth x was 0.01 and 0.03 respectively. The room temperature d 33 The values ​​are only 15.8 pC / N and 15.7 pC / N respectively, which are lower than the pure component with a molar ratio of x of 0 and also lower than the bismuth-deficient ceramic material of the present invention.

[0058] The description of the above embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and 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 present invention should be within the protection scope of the present invention.

Claims

1. A sodium potassium bismuth niobate high temperature piezoelectric ceramic material, characterized in that: The chemical formula of the sodium potassium bismuth niobate high temperature piezoelectric ceramic material is Na 0.25 K 0.25 Bi 2.5+x Nb2O 9+3x / 2 , wherein -0.10≤x<0, and x is the molar percentage.

2. The sodium potassium bismuth niobate high temperature piezoelectric ceramic material according to claim 1, characterized in that: x＝-0.05。 3. The sodium potassium bismuth niobate high temperature piezoelectric ceramic material according to claim 1, characterized in that: The piezoelectric coefficient d 33 It is (15~20)pC / N, and the Curie temperature is above 650℃.

4. A method for preparing the sodium potassium bismuth niobate high temperature piezoelectric ceramic material according to any one of claims 1 to 3, characterized in that: The preparation method includes mixing, synthesis, molding, plasticizing and sintering.

5. The preparation method according to claim 4, characterized in that: The synthesis temperature is 700-900° C. and the time is 1-3 hours.

6. The preparation method according to claim 4, characterized in that: The sintering is carried out at a temperature of 1000-1100° C. and for a time of 1-3 hours.

7. The preparation method according to any one of claims 4 to 5, characterized in that: The preparation method comprises the following steps: 1) mixing Na2CO3, K2CO3, Bi2O3 and Nb2O5 according to a stoichiometric ratio; the obtained mixture is subjected to a ball milling, synthesis and grinding to obtain a ceramic powder; 2) ball-milling the ceramic powder obtained in step 1) for a second time, adding a binder to granulate after drying, pressing and molding after aging, and then heating and expelling the plastic to obtain a ceramic embryo; 3) placing the ceramic blank obtained in step 2) into a high-temperature furnace, covering the ceramic blank with ceramic powder having the same composition as in step 1), and then sintering to obtain a ceramic sheet; 4) Processing the sintered ceramic sheet into a desired size, ultrasonically cleaning, screen printing silver, drying, and calcining the silver to obtain a sodium potassium bismuth acid high-temperature piezoelectric ceramic material.

8. The preparation method according to claim 7, characterized in that: In step 2), the amount of the binder added is 5-7 wt.% of the weight of the ceramic powder.

9. The preparation method according to claim 7, characterized in that: In step 2), the heating and plastic removal conditions are: heating to 500-600° C. at a heating rate not higher than 2° C. / min, and keeping the temperature for 1-3 hours.

10. An application of the sodium potassium bismuth niobate high temperature piezoelectric ceramic material according to any one of claims 1 to 3, characterized in that: For use in high temperature piezoelectric vibration sensors.

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