CN114409401A - Potassium-sodium niobate piezoelectric ceramic, preparation method thereof and electronic equipment - Google Patents

Abstract

The invention relates to a potassium-sodium niobate-based piezoelectric ceramic. The potassium-sodium niobate-based piezoelectric ceramic has the following general formula: (0.96‑x)(K _0.48 Na _0.52 )Nb _0.96 Sb _0.04 O _3‑0.04 (Bi _0.5 Na _0.5 ) ZrO ₃ ‑xCaZrO ₃ ‑0.4%Fe ₂ O ₃ , wherein x is the mole fraction of CaZrO ₃ , 0<x≤0.02. The above-mentioned potassium-sodium niobate-based piezoelectric ceramics introduced CaZrO ₃ as a new system source in the ion-doped ternary component potassium-sodium niobate-based lead-free piezoelectric ceramics, which can maintain good piezoelectric properties while maintaining good piezoelectric properties. The T _0-T phase transition point can be stably lowered to room temperature, the difference between the orthorhombic and tetragonal phases can be reduced, the smooth transition of the polymorphic phase transition can be realized, and it has excellent temperature stability. In addition, the preparation process of the potassium sodium niobate series piezoelectric ceramics is simple, the raw materials are non-toxic and harmless, and it is suitable for industrialized large-scale production.

Description

Potassium and sodium niobate piezoelectric ceramics, preparation method thereof, and electronic equipment

technical field

The invention relates to the field of functional ceramic materials, in particular to a potassium-sodium niobate series piezoelectric ceramic, a preparation method and electronic equipment thereof.

Background technique

Piezoelectric ceramics are functional ceramics that can realize the mutual conversion of mechanical energy and electrical energy. They have the advantages of facilitating the manufacture of various functional components with low loss, high reliability and miniaturization. They are widely used in various fields of daily production and life. Very wide range of applications such as transducers, sensors, drives, etc. At present, the mainstream material of piezoelectric ceramic devices on the market is lead-based lead zirconate titanate (PZT) material. The heavy metal element lead contained in this lead-based material is extremely harmful to organisms and the environment. Therefore, developing a lead-free piezoelectric ceramic material that can replace lead zirconate titanate (PZT) has become an extremely important task for researchers.

Three lead-free piezoelectric ceramic materials of perovskite type (including potassium sodium niobate series, sodium bismuth titanate series and barium titanate series) are currently expected to replace lead-based piezoelectric ceramics because they do not contain harmful elements such as lead. The potassium and sodium niobate ceramics have become the hot research materials of researchers because of their good piezoelectric properties and high Curie temperature. The research results show that the piezoelectric properties of pure potassium and sodium niobate ceramics are still far behind that of practical PZT ceramics. Drawing on the research ideas of PZT ceramics, through ion doping and the construction of binary and ternary systems The piezoelectric properties of potassium sodium niobate piezoelectric ceramics can be significantly improved, which can be comparable to the piezoelectric properties of practical PZT ceramics. Generally speaking, the essence of the binary system is to move the rhombic-orthogonal phase transition point of the potassium sodium niobate system up to room temperature or the orthogonal-tetragonal phase transition point down to room temperature; while the design of the ternary system can The high-temperature orthorhombic-tetragonal phase transition point and the low-temperature rhombic-orthogonal phase transition point are simultaneously moved to room temperature to construct a rhombic-tetragonal phase transition. At present, the ternary systems are mainly: K _1-X Na _X Nb _1-Y Sb _Y O ₃ -zBiFeO ₃ -wBi _0.5 Na _0.5 ZrO ₃ (KNNS-zBF-wBNZ) and K _1-X Na _X Nb _1-Y Sb _Y O ₃ -zBaZrO ₃ -wBi _0.5 K _0.5 HfO ₃ (KNNS-zBZ-wBKH), etc., according to the reported results, its piezoelectric performance is greatly improved compared with the unit and binary systems, but it is not difficult for us It was found that with the increase of the piezoelectric constant of the composite potassium sodium niobate material, its Curie temperature will become lower, and the application temperature range will become narrower, which greatly limits the application range.

In order to improve the temperature stability of the piezoelectric properties of potassium sodium niobate-based ceramics, researchers have made many attempts. One is to adjust the polymorphic phase transition temperature below room temperature by doping, because the fundamental reason for the poor temperature stability of potassium sodium niobate-based ceramics is the existence of polymorphic phase transitions near room temperature; the other is to prepare woven fabrics. Structured ceramics. However, the former inevitably reduces the piezoelectric properties of ceramics due to avoiding the polymorphic phase transition effect; the latter requires a very complicated preparation process and does not utilize large-scale industrial production.

SUMMARY OF THE INVENTION

Based on this, it is necessary to provide a potassium-sodium niobate-based piezoelectric ceramic with good piezoelectric performance, good temperature stability and simple preparation process.

In addition, a preparation method of potassium sodium niobate series piezoelectric ceramics is also provided.

A potassium-sodium niobate-based piezoelectric ceramic, the potassium-sodium niobate-based piezoelectric ceramic has the following general formula: (0.96-x)(K _0.48 Na _0.52 )Nb _0.96 Sb _0.04 O ₃ -0.04(Bi _0.5 Na _0.5 ) ZrO ₃ -xCaZrO ₃ -0.4%Fe ₂ O ₃ , wherein x is the mole fraction of CaZrO ₃ , 0<x≦0.02.

The above potassium-sodium niobate series piezoelectric ceramics, CaZrO ₃ is introduced as a new system source in the ion-doped ternary component potassium-sodium niobate series lead-free piezoelectric ceramics, which improves the density of the piezoelectric ceramics, and can While maintaining good piezoelectric properties, the T _0-T phase transition point can be stably lowered to room temperature, reducing the difference between the orthogonal and tetragonal phases, and realizing the smooth transition of the polymorphic phase transition, making it excellent temperature stability. sex. In addition, the preparation process of the potassium sodium niobate series piezoelectric ceramics is simple, the raw materials are non-toxic and harmless, and it is suitable for industrialized large-scale production.

In one of the embodiments, 0<x≤0.016.

In one of the embodiments, the value of x is 0.004, 0.008 or 0.012.

In one of the embodiments, the piezoelectric constant d ₃₃ of the potassium-sodium niobate-based piezoelectric ceramic ranges from 400pC/N to 450pC/N.

In one of the embodiments, the electromechanical coupling coefficient Kp of the potassium sodium niobate based piezoelectric ceramics ranges from 0.35 to 0.40.

A preparation method of potassium sodium niobate piezoelectric ceramics, comprising the following steps:

Using K ₂ CO ₃ , Na ₂ CO ₃ , Nb ₂ O ₅ , Sb ₂ O ₃ , ZrO ₂ , Bi ₂ O ₃ , CaZrO ₃ and Fe ₂ O ₃ as raw materials, niobic acid was prepared by solid-phase method according to the above general formula Potassium-sodium piezoelectric ceramics.

In one embodiment, the above-mentioned step of preparing potassium sodium niobate piezoelectric ceramics by solid-phase method includes:

The raw material mixture weighed according to the above-mentioned general formula is ball-milled to obtain the first wet slurry;

After drying the first wet-process slurry, sintering at 830°C～870°C for 5h～7h for the first time, and ball-milling to obtain the second wet-process slurry;

The second wet slurry is dried and ground to obtain ceramic powder;

adding 3% (w/w) to 4% (w/w) polyvinyl alcohol solution to the above-mentioned ceramic powder, and drying;

The dried ceramic powder is ground and pressed into a ceramic embryo;

sintering the above-mentioned ceramic ligand at 1090°C～1100°C for 3h～5h again to obtain a ceramic product; and

The above-mentioned ceramic product is treated with silver, and immersed in silicone oil for polarization to obtain a ceramic product.

In one of the embodiments, before the raw material mixture weighed according to the general formula is ball-milled to obtain the first wet-process slurry, the step of synthesizing CaZrO ₃ is also included, and the step of synthesizing CaZrO ₃ includes:

The CaCO ₃ and ZrO ₂ are mixed according to the molar amount (0.8-1.2): 1, and ball-milled to obtain the first mixture; and

After drying the first mixture, the temperature is kept at 1480°C to 1520°C for 3h to 5h, ball-milled, and dried to obtain CaZrO ₃ powder.

In one embodiment, in the step of adding a 3% (w/w) to 4% (w/w) polyvinyl alcohol solution to the ceramic powder, the mass ratio of the ceramic powder to the polyvinyl alcohol solution It is (8～12):3.

An electronic device includes the potassium-sodium niobate-based piezoelectric ceramic according to any one of the above embodiments.

The potassium and sodium niobate ceramics with ternary components provided by the invention have excellent piezoelectric properties, high Curie temperature and good temperature stability, can be applied in drivers and sensors, and can replace lead-based piezoelectrics in the future. Ceramics are of great significance.

Description of drawings

Fig. 1 is the X-ray diffraction pattern of the finished ceramic wafer prepared in each embodiment;

Fig. 2 is the dielectric thermogram of the finished ceramic wafer prepared in each embodiment;

Fig. 3 is the hysteresis loop of the ceramic finished wafer prepared in each embodiment tested at 1kHz;

FIG. 4 is the dielectric loss curve of the finished ceramic wafer prepared in each example.

Detailed ways

In order to make the above objects, features and advantages of the present invention more clearly understood, the specific embodiments of the present invention will be described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terms used herein in the description of the present invention are for the purpose of describing specific embodiments only, and are not intended to limit the present invention. The terms "first" and "second" herein are only used for descriptive purposes, and should not be construed as indicating or implying relative importance or implicitly indicating the number of indicated technical features.

"piezoelectric constant d ₃₃ " is one of the most commonly used and important parameters to characterize the performance of piezoelectric materials. Generally, the higher the piezoelectric constant of ceramics, the better the piezoelectric performance. The first number in the subscript refers to the direction of the electric field , the second number refers to the direction of stress or strain, "33" means that the polarization direction is the same as the direction of force applied during measurement.

"Electromechanical coupling coefficient": During the vibration process of the piezoelectric vibrator, the mechanical energy is converted into electrical energy, or the electrical energy is converted into mechanical energy. This parameter expressing the degree of mutual transformation between mechanical energy and electrical energy in the piezoelectric body is called electromechanical coupling. Coefficient, which is a comprehensive physical quantity to measure the quality of piezoelectric conversion performance. The plane electromechanical coupling coefficient Kp reflects the polarization and electrical excitation of the thin wafer along the thickness direction, and is a parameter for the electromechanical coupling effect during radial stretching vibration.

An embodiment of the present application provides a potassium-sodium niobate-based piezoelectric ceramic, and the potassium-sodium niobate-based piezoelectric ceramic has the following general formula: (0.96-x)(K _0.48 Na _0.52 )Nb _0.96 Sb _0.04 O ₃ - 0.04(Bi _0.5 Na _0.5 )ZrO ₃ -xCaZrO ₃ -0.4%Fe ₂ O ₃ , wherein x is the mole fraction of CaZrO ₃ , 0<x≤0.02.

The above potassium-sodium niobate series piezoelectric ceramics, CaZrO ₃ is introduced as a new system source in the ion-doped ternary component potassium-sodium niobate series lead-free piezoelectric ceramics, which improves the density of the piezoelectric ceramics, and can While maintaining good piezoelectric properties, the T _0-T phase transition point can be stably lowered to room temperature, reducing the difference between the orthogonal and tetragonal phases, and realizing the smooth transition of the polymorphic phase transition, making it excellent temperature stability. sex. In addition, the preparation process of the potassium sodium niobate series piezoelectric ceramics is simple, the raw materials are non-toxic and harmless, and it is suitable for industrialized large-scale production.

In one of the embodiments, 0<x≤0.016. Further, 0.004≤x≤0.012.

Specifically, when 0<x≤0.016, the piezoelectric constant d ₃₃ of the above potassium sodium niobate piezoelectric ceramics ranges from 400pC/N to 450pC/N, and the electromechanical coupling coefficient Kp ranges from 0.35 to 0.40. There is a higher piezoelectric constant d ₃₃ and a higher electromechanical coupling coefficient Kp.

In one of the embodiments, the value of x is 0.004, 0.008 or 0.012.

In some embodiments, the maximum electric polarization strength of the potassium sodium niobate-based piezoelectric ceramics can reach 19 μC/cm ² -22 μC/cm ² , and the remanent polarization (Pr) can reach 14 μC/cm ² -16 μC/cm ² . Specifically, the higher the remanent polarization, the more sufficient the polarization and the better the performance.

Specifically, the present invention adjusts the ratio of CaZrO ₃ and (K _0.48 Na _0.52 )Nb _0.96 Sb _0.04 O ₃ by adjusting x to adjust the ratio of T and O to improve piezoelectric performance.

An embodiment of the present application also provides a method for preparing potassium sodium niobate piezoelectric ceramics, the preparation method comprising the following steps:

Using K ₂ CO ₃ , Na ₂ CO ₃ , Nb ₂ O ₅ , Sb ₂ O ₃ , ZrO ₂ , Bi ₂ O ₃ , CaZrO ₃ and Fe ₂ O ₃ as raw materials, niobic acid was prepared by solid-phase method according to the above general formula Potassium-sodium piezoelectric ceramics.

Specifically, using the above compounds as raw materials can effectively synthesize potassium sodium niobate piezoelectric ceramics. It can be understood that, in other embodiments, other carbonate and oxide raw materials containing the above-mentioned compound elements can be used for the preparation of potassium and sodium niobate piezoelectric ceramics, but the efficiency thereof may be reduced.

In some embodiments, the above-mentioned steps of preparing potassium sodium niobate-based piezoelectric ceramics by solid-phase method include step S11 , step S12 , step S13 , step S14 , step S15 , step S16 and step S17 . specifically:

Step S11: Ball milling the raw material mixture weighed according to the above general formula to obtain a first wet slurry.

In some embodiments, a step of synthesizing CaZrO ₃ is further included before step S11, and the step of synthesizing CaZrO ₃ includes step S01 and step S02.

Step S01 : mixing CaCO ₃ and ZrO ₂ according to the molar amount (0.8-1.2): 1, and ball-milling to obtain a first mixture.

Further, in some embodiments, CaCO ₃ and ZrO ₂ are mixed in a molar amount of 1:1, and ball-milled to obtain a first mixture.

Step S02: After drying the first mixture, keep the temperature at 1480°C to 1520°C for 3h to 5h, ball mill and dry to obtain CaZrO ₃ powder. In an optional specific example, the first mixture is dried and kept at 1500° C. for 4 hours, and then ball-milled again, and dried to obtain CaZrO ₃ powder. Specifically, the temperature at which the first mixture is dried is 60°C to 90°C.

In one embodiment, before weighing the raw materials, the step of drying K ₂ CO ₃ and Na ₂ CO ₃ is further included. Specifically, K ₂ CO ₃ and Na ₂ CO ₃ are put into an oven and dried at 200° C.˜250° C. for 2h˜5h.

Step S12 : drying the first wet-process slurry, sintering at 830° C. to 870° C. for 5 h to 7 hours for the first time, and performing secondary ball milling to obtain the second wet-process slurry. In an optional specific example, the first wet-process slurry is dried and initially sintered at 850° C. for 6 hours, and then ball-milled for a second time to obtain the second wet-process slurry. Specifically, the temperature for drying the first wet slurry is 60°C to 90°C.

Step S13: The second wet slurry is dried and ground to obtain ceramic powder.

In some embodiments, after the second wet-process slurry is dried and ground, the step of sieving is further included. The temperature for drying the second wet slurry is 60°C to 90°C.

Step S14: adding 3% (w/w) to 4% (w/w) polyvinyl alcohol solution to the ceramic powder, and drying.

In one embodiment, the mass ratio of the ceramic powder to the polyvinyl alcohol solution is 10:3.

In some embodiments, the drying temperature ranges from 60°C to 90°C.

Step S15: Grind the dried ceramic powder and press it into a ceramic embryo.

In an optional specific example, the dried ceramic powder is pressed into a ceramic green body with a diameter of 11 mm-13 mm and a thickness of 0.8 mm-1.2 mm by using a mold. Further, in some embodiments, the dried ceramic powder is pressed into a ceramic green body with a diameter of 12 mm and a thickness of 1 mm with a mold. It can be understood that, in other embodiments, the ceramic body can be of other specifications.

In one embodiment, after the dried ceramic powder is ground and pressed into a ceramic green body, the step of degumming the ceramic green body at a temperature of 600°C to 700°C for 1 hour to 2 hours is further included.

Step S16 : sintering the above-mentioned ceramic ligand at 1090° C.˜1100° C. for 3 h˜5 h again to obtain a ceramic product.

Step S17 : the above-mentioned ceramic product is treated with silver, and immersed in silicone oil for polarization to obtain a ceramic product.

Specifically, the step of being treated with silver includes: keeping the temperature at 750° C.˜780° C. for 20 min˜30 min. The polarizing step includes: polarizing the ceramic covered with silver electrodes in silicone oil immersion for 30min at room temperature (25°C±5°C), and the polarizing electric field is 3kV/mm.

In some embodiments, the above-mentioned ball milling step uses a planetary ball mill. It can be understood that, in other embodiments, other ball mills can be used for ball milling, so as to be suitable for mass production.

In some embodiments, in the above ball milling step, absolute ethanol is used as the ball milling medium, and the balls are mixed under the condition that the mass ratio of the 5mm diameter zirconia balls and the 2mm zirconia balls is 1:2, so that the quality of the raw materials is : The mass of the mixed balls: the mass of anhydrous ethanol is 1:8:5, and the ball mill is milled at 400RPM for 8h~15h. Specifically, using a mixture of zirconia beads with a diameter of 5mm and zirconia beads with a diameter of 2mm as the ball milling balls has the best effect. The ceramics prepared by this method are very dense among the grains and have no pores.

In some embodiments, the step of sintering above is performed in a muffle furnace. Specifically, the muffle furnace is heated at a rate of 3°C/min to 5°C/min. It is understood that in other embodiments, other thermal processing devices may be used for sintering.

In some embodiments, the step of debinding described above is performed in a tube furnace. Specifically, the tube furnace is heated at a rate of 3°C/min to 5°C/min. It can be understood that, in other embodiments, other thermal processing devices may be used for debinding.

The above-mentioned preparation method of potassium sodium niobate series piezoelectric ceramics utilizes industrial raw materials, is non-toxic and harmless, adopts a solid-phase sintering method, has a low sintering temperature, is easy to realize, and has a simple process, and can be used for industrial large-scale production.

An embodiment of the present application also provides an electronic device, including the potassium-sodium niobate-based piezoelectric ceramic described in any of the above embodiments.

The above-mentioned electronic equipment includes the above-mentioned potassium-sodium niobate series piezoelectric ceramics. The potassium-sodium niobate series ceramics have excellent piezoelectric properties, high Curie temperature and good temperature stability, and can be used in drivers or sensors. It is of great significance in the process of replacing lead-based piezoelectric ceramics.

In some embodiments, the electronic device is an ultrasonic transducer, an underwater acoustic transducer, an electroacoustic transducer, a ceramic filter, a ceramic transformer, a ceramic frequency discriminator, a high voltage generator, an infrared detector, a surface acoustic wave device , electro-optical devices, ignition and detonation devices or piezoelectric gyroscopes, etc. It can be understood that the electronic device is not limited to the above, and may also be other devices including the above-mentioned potassium sodium niobate piezoelectric ceramics.

specific embodiment

The following describes in detail with reference to specific embodiments. The following examples do not include other components except inevitable impurities unless otherwise specified. Unless otherwise specified, the reagents and instruments used in the examples are routinely selected in the art. The experimental methods for which specific conditions are not indicated in the examples are realized according to conventional conditions, such as conditions described in literatures, books or methods recommended by manufacturers.

Example 1

A lead-free piezoelectric ceramic material of potassium sodium niobate series with ion-doped ternary components is prepared.

(1) Synthesis of CaZrO ₃ : Weigh CaCO ₃ and ZrO ₂ according to the molar ratio of 1:1, put them into a ball milling jar, use absolute ethanol as the ball milling medium, and use zirconia with a diameter of 5 mm with a mass ratio of 1:2 The beads were mixed with 2 mm diameter zirconia beads as ball milling beads. Under the condition that the mass ratio of raw materials, ball milling beads and absolute ethanol is 1:8:4, the initial ball milling is carried out in a planetary ball mill at 400RPM for 15h to obtain a wet slurry, and the ball-milled wet slurry is placed. Put it into the oven to bake at 80°C for 30min, take out the dried powder and pass it through a 75 mesh sieve, put it in a crucible, send it to a box muffle furnace at 1500°C, and keep the temperature at 5°C/min for 4h, take it out and ball-mill it again, and dry it. , passed through a 75-mesh sieve to obtain CaZrO ₃ powder.

(2) Calculate the quality of raw materials: take K ₂ CO ₃ , Na ₂ CO ₃ , Nb ₂ O ₅ , Sb ₂ O ₃ , ZrO ₂ , Bi ₂ O ₃ , CaZrO ₃ , Fe ₂ O ₃ as raw materials, according to the chemical formula (0.96 -x) (K _0.48 Na _0.52 )Nb _0.96 Sb _0.04 O ₃ -0.04(Bi _0.5 Na _0.5 )ZrO ₃ -xCaZrO ₃ -0.4% Fe ₂ O ₃ x=0.004 The mass of each raw material required for calculation.

(3) Ingredients: put K ₂ CO ₃ and Na ₂ CO ₃ in an oven at 220° C. for 2 hours to dry to remove moisture, then weigh according to the calculated mass of raw materials, put the weighed raw materials into a ball mill, and use anhydrous ethanol As the ball milling medium, zirconia beads with a diameter of 5 mm and zirconia beads with a diameter of 2 mm were mixed with a mass ratio of 1:2, and the mass ratio of raw materials, ball milling beads and absolute ethanol was 1:8:4. Then, in a planetary ball mill at 400RPM rotating speed for 15h primary ball milling, to obtain wet slurry.

(4) Primary sintering: put the obtained slurry in an oven at 80°C for 6-8 hours to dry to obtain dry powder, then put it into a crucible and compress it tightly, cover the crucible cover, and send it into a box muffle furnace 850℃, the heating rate is 5℃/min, and the pre-burning is 6h.

(5) Secondary ball milling: pulverize the pre-sintered block, and transfer the obtained powder into a ball milling tank, use absolute ethanol as the ball milling medium, and use zirconia beads with a diameter of 5 mm and a diameter of 2 mm with a mass ratio of 1:2. The zirconia beads were mixed for the second ball milling. Under the condition that the mass ratio of raw materials, ball milling beads and absolute ethanol was 1:8:4, ball milling was carried out at a speed of 400RPM in a planetary ball mill for 15h.

(6) Drying and sieving: put the slurry obtained by ball milling into an oven for drying at 80°C, grind the dried powder, and pass it through a 75-mesh sieve to obtain a powder with fine particle size and uniform particle size.

(7) Granulation: Add a polyvinyl alcohol solution with a mass fraction of 3% (w/w) to 4% (w/w) to the powder obtained by grinding and sieving, and the mass ratio of the powder and the polyvinyl alcohol solution is Mix the powder with the polyvinyl alcohol solution at a ratio of 10:3, put it in an oven at 80°C for 10 minutes to dry the water, grind it, and pass it through a 75-mesh sieve.

(8) Press molding: the powder obtained after the sieving treatment is pressed and molded by a mold to obtain a disc-shaped ceramic green embryo, the diameter of the ceramic green embryo is 12 mm and the thickness is 1 mm.

(9) Ordinary sintering: put the obtained ceramic green embryos into a tube furnace at 650°C, a heating rate of 3°C/min, and sinter for 2 hours for debinding treatment. The ceramic green embryos obtained after debinding are placed in the tube furnace. Ceramic products were obtained by holding the temperature at 1100 °C for 4 h.

(10) Porcelain polarization: the obtained ceramic products were treated with silver, kept at 780°C for 30 minutes, and the ceramic products with silver electrodes were immersed in silicone oil for 30 minutes at room temperature, and the polarization electric field was 3kV/mm. After being polarized and placed for 24 hours, the finished ceramic product is obtained.

Example 2

The steps of preparing the ion-doped ternary-based potassium-sodium niobate-based lead-free piezoelectric ceramic material in this example are roughly the same as those in Example 1. The difference is that in step (2) of this example, the chemical formula where x=0.008.

Example 3

The steps of preparing the ion-doped ternary-based potassium-sodium niobate-based lead-free piezoelectric ceramic material in this example are roughly the same as those in Example 1. The difference is that in step (2) of this example, the chemical formula where x=0.012.

Example 4

The steps of preparing the ion-doped ternary-based potassium-sodium niobate-based lead-free piezoelectric ceramic material in this example are roughly the same as those in Example 1. The difference is that in step (2) of this example, the chemical formula where x=0.016.

Example 5

The steps of preparing the ion-doped ternary-based potassium-sodium niobate-based lead-free piezoelectric ceramic material in this example are roughly the same as those in Example 1. The difference is that in step (2) of this example, the chemical formula where x=0.

test

The structures and properties of the ceramic products prepared in the above examples were tested, and the results are shown in Figures 1 to 4 and Table 1.

Fig. 1 is the X-ray diffraction pattern of the finished ceramic wafers prepared in each example. It can be seen from the left image in Fig. 1 that all the samples in the examples are of perovskite structure without any impurity phase. As shown in the right image in Figure 1, the left image is enlarged and analyzed at 2θ=45.5°, and the double peaks coexist, indicating that the orthorhombic phase and the tetragonal phase coexist at room temperature. As x increases, the diffraction peak gradually moves to a lower angle Offset, indicating that the unit cell expands and the peak intensity difference becomes larger and larger, the difference between the two phases of crystallinity becomes larger, and the piezoelectric effect becomes worse. Therefore, x should not be too large, that is, the addition amount of calcium zirconate needs to be within an appropriate range.

FIG. 2 is a dielectric thermogram of the finished ceramic wafers prepared in each example. It can be seen from Figure 2 that as x increases, the Curie temperature of the piezoelectric ceramic material gradually decreases, but remains above 200 °C. When x=0.016, the piezoelectric constant corresponding to the Curie temperature point is too low, so the performance is poor.

FIG. 3 shows the hysteresis loops of the finished ceramic wafers prepared in each example at 1 kHz. It can be seen from Figure 3 that under the electric field of 4000V/mm, the larger the piezoelectric constant is, the larger the remanent polarization is, and the value can reach 15.7μC/cm ² , which is higher than that of pure potassium sodium niobate (that is, x=0 ), the curve is saturated and approximately rectangular. It shows that proper doping of calcium zirconate in the process of preparing the above piezoelectric ceramics is beneficial to improve the polarization strength of the piezoelectric ceramics.

FIG. 4 is the dielectric loss curve of the finished ceramic wafer prepared in each example. It can be seen from Figure 4 that with the increase of x, the loss also increases gradually, indicating that the crystal defects are also increasing, but the overall percentage is still at a low level, which has little effect on the piezoelectric performance of the ceramic.

Table 1 shows the piezoelectric constant d ₃₃ , the electromechanical coupling coefficient Kp, the mechanical quality factor Qm, the relative permittivity, the dielectric loss value and the density statistics of the ceramic finished wafers prepared in each example.

Table 1

By comparison, it is found that when x=0.008, the piezoelectric constant d ₃₃ =430pC/N is the largest, and Kp=0.39 is the largest. In the case of little difference in other properties, x=0.008 is the optimal value for the stoichiometric ratio of the system.

The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity, all possible combinations of the technical features in the above-described embodiments are not described. However, as long as there is no contradiction between the combinations of these technical features, All should be regarded as the scope described in this specification.

The above-mentioned embodiments only represent several embodiments of the present invention, and the descriptions thereof are specific and detailed, but should not be construed as a limitation on the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can also be made, which all belong to the protection scope of the present invention. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the technical solutions provided by the present invention are all within the protection scope of the appended claims of the present invention. Therefore, the protection scope of the patent of the present invention should be based on the appended claims, and the description and drawings can be used to explain the content of the claims.

Claims (10)

1. A potassium-sodium niobate-based piezoelectric ceramic characterized by having the following general formula: (0.96-x) (K)_0.48Na_0.52)Nb_0.96Sb_0.04O₃-0.04(Bi_0.5Na_0.5)ZrO₃-xCaZrO₃-0.4％Fe₂O₃Wherein x is CaZrO₃X is more than 0 and less than or equal to 0.02.

2. The potassium-sodium niobate-based piezoelectric ceramic according to claim 1, wherein 0 < x.ltoreq.0.016.

3. The potassium-sodium niobate-based piezoelectric ceramic according to claim 1, wherein x has a value of 0.004, 0.008, or 0.012.

4. The potassium-sodium niobate-based piezoelectric ceramic according to claim 1, wherein the potassium-sodium niobate-based piezoelectric ceramic has a piezoelectric constant d₃₃The numerical range of (a) is 400pC/N to 450 pC/N.

5. The potassium-sodium niobate-based piezoelectric ceramic according to any one of claims 1 to 4, wherein an electromechanical coupling coefficient Kp of the potassium-sodium niobate-based piezoelectric ceramic has a value in a range of 0.35 to 0.40.

6. A preparation method of potassium-sodium niobate piezoelectric ceramics is characterized by comprising the following steps:

with K₂CO₃、Na₂CO₃、Nb₂O₅、Sb₂O₃、ZrO₂、Bi₂O₃、CaZrO₃And Fe₂O₃The potassium-sodium niobate-based piezoelectric ceramic is prepared by a solid phase method according to the general formula in claim 1 as a raw material.

7. The method according to claim 6, wherein the step of preparing the potassium-sodium niobate-based piezoelectric ceramic by a solid phase method comprises:

ball-milling the raw material mixture weighed according to the general formula to obtain first wet-process slurry;

drying the first wet-process slurry, primarily sintering at 830-870 ℃ for 5-7 h, and performing ball milling to obtain second wet-process slurry;

drying the second wet-process slurry and grinding to obtain ceramic powder;

adding 3% (w/w) -4% (w/w) of polyvinyl alcohol solution into the ceramic powder, and drying;

grinding the dried ceramic powder and pressing into a ceramic blank;

sintering the ceramic ligand for 3-5 h at 1090-1100 ℃ again to obtain a ceramic product; and

and (3) carrying out silver treatment on the ceramic product, and soaking the ceramic product in silicone oil for polarization to obtain a ceramic finished product.

8. The preparation method according to claim 7, further comprising synthesizing CaZrO before ball milling the raw material mixture weighed according to the general formula to obtain the first wet slurry₃The step of synthesizing CaZrO₃Comprises the following steps:

mixing CaCO₃And ZrO₂According to the molar weight (0.8-1.2): 1, mixing and ball-milling to obtain a first mixed material; and

drying the first mixed material, preserving the heat for 3 to 5 hours at 1480 to 1520 ℃, ball-milling and drying to obtain CaZrO₃And (3) powder.

9. The method according to any one of claims 7 to 8, wherein in the step of adding a polyvinyl alcohol solution in an amount of 3% (w/w) to 4% (w/w) to the ceramic powder, the mass ratio of the ceramic powder to the polyvinyl alcohol solution is (8 to 12): 3.

10. an electronic device comprising the potassium-sodium niobate-based piezoelectric ceramic according to any one of claims 1 to 5.

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