Doped and modified potassium sodium niobate lead-free piezoelectric ceramic material based on microwave synthesis and preparation method of doped and modified potassium sodium niobate lead-free piezoelectric ceramic material

Abstract

The invention belongs to the technical field of ceramic powder synthesis, and discloses a microwave synthesis-based doped modified potassium sodium niobate lead-free piezoelectric ceramic material and a preparation method thereof. According to the invention, a microwave heating method is adopted for synthesis, and a 0.94 (K < 0.48 > Na < 0.48 > Li < 0.04 >) (Nb < 0.95 > Sb < 0.05 >) O < 3 >-0.06 Bi < 0.5 > (Na < 0.7 > K < 0.3 >) < 0.5 > ZrO < 3 > piezoelectric material system is constructed. A direct microwave heating synthesis method is adopted, the advantages of microwave synthesis are effectively exerted, low-temperature and rapid synthesis of the doped modified potassium sodium niobate lead-free piezoelectric ceramic powder material is achieved, the ceramic powder good in crystallization and large in surface activity is obtained, energy consumption is low, environment friendliness is achieved, and later ceramic sintering and performance optimization are facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of ceramic powder synthesis, and in particular to a doped and modified potassium sodium niobate lead-free piezoelectric ceramic material based on microwave synthesis and a preparation method thereof. Background Art

[0002] Piezoelectric ceramics are a type of functional material that can realize the mutual conversion between mechanical energy and electrical energy. They are widely used in electronic industries such as medical imaging, acoustic sensors, and ultrasonic motors. At present, most industrialized piezoelectric ceramics are lead zirconate titanate Pb(Zr,Ti)O3 with a Pb content of more than 60wt%. However, during its preparation, use, and disposal, Pb will cause harm to human life and the natural environment. Therefore, lead-free has gradually become the main direction of piezoelectric ceramic research.

[0003] Potassium sodium niobate (K,Na)NbO3-based lead-free piezoelectric ceramics (abbreviated as KNN) are solid solutions of antiferroelectric phase NaNbO3 and ferroelectric phase KNbO3. This type of ceramic has a high Curie temperature (Tc=420℃) and good piezoelectric properties. In recent years, many researchers have tried to further improve the piezoelectricity and dielectric properties of KNN-based piezoelectric ceramics by doping various ions, adjusting the ratio between potassium and sodium elements, and adding various sintering aids. Potassium sodium niobate ceramics are generally sintered after synthesizing ceramic powders from raw materials. The quality of the powder obtained by calcination plays a decisive role in the microstructure and macroscopic properties of the ceramic material. However, the piezoelectric constant d of potassium sodium niobate piezoelectric ceramics prepared from potassium sodium niobate powders obtained by traditional solid phase method, hydrothermal method, molten salt method, etc. is 33 The piezoelectric performance of KNN ceramics is about 120pC / N, which is not very good. In addition, the alkali metal potassium and sodium ions in KNN ceramics are easy to volatilize at higher temperatures (about 900°C), causing the actual composition of the ceramics to deviate from the stoichiometric formula and reduce its piezoelectricity. The existence of the above problems limits the promotion and application of potassium sodium niobate-based piezoelectric ceramics. Summary of the invention

[0004] The object of the present invention is to provide a doped modified potassium sodium niobate lead-free piezoelectric ceramic material based on microwave synthesis and a preparation method thereof, so as to solve the problem of low piezoelectric performance of potassium sodium niobate piezoelectric material.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a doped modified potassium sodium niobate lead-free piezoelectric ceramic material based on microwave synthesis, wherein the chemical formula of the doped modified potassium sodium niobate lead-free piezoelectric ceramic material is: 0.94 (K 0.48 Na 0.48 Li 0.04 )(Nb 0.95 Sb 0.05)O3-0.06Bi 0.5 (Na 0.7 K 0.3 ) 0.5 ZrO3.

[0007] The present invention also provides a method for preparing a doped and modified potassium sodium niobate lead-free piezoelectric ceramic material based on microwave synthesis, comprising the following steps:

[0008] Mixing a K source, a Na source, a Li source, a Nb source, a Sb source, a Bi source and a Zr source according to a stoichiometric ratio in a chemical formula to obtain a mixture;

[0009] Under microwave-assisted conditions, the mixed material is subjected to a first heating and a second heating in sequence, and then sintered to obtain a doped and modified potassium sodium niobate lead-free piezoelectric ceramic material.

[0010] Preferably, in the preparation method, the K source includes K2CO3 or KOH, the Na source includes Na2CO3 or NaOH, the Li source includes Li2CO3, LiOH or LiF, the Nb source includes Nb2O5, the Sb source includes Sb2O3, Sb2S3 or Sb2O5, the Bi source includes Bi2O3, Bi2S3 or Bi(NO3)3, and the Zr source includes ZrO2, ZrCl4, BaZrO3 or ZrSiO4.

[0011] Preferably, in the preparation method, the K source, Na source, Li source, Nb source, Sb source, Bi source and Zr source are mixed according to the stoichiometric ratio in the chemical formula, and specifically include the following steps:

[0012] The K source, Na source, Li source, Nb source, Sb source, Bi source and Zr source are respectively subjected to the first drying, and the K source, Na source, Li source, Nb source, Sb source, Bi source and Zr source are mixed according to the stoichiometric ratio in the chemical formula, and the obtained mixed raw materials are sequentially ball-milled and second dried.

[0013] Preferably, in the preparation method, the temperature of the first drying is 100 to 150° C., and the time of the first drying is 1 to 3 hours;

[0014] The second drying temperature is 100 to 140° C., and the second drying time is 12 to 48 hours.

[0015] Preferably, in the preparation method, the rotation speed of the ball mill is 300-600 r / min, the ball milling time is 10-24 h, the ball milling medium is ethanol or acetone medium, and the mass ratio of the mixed raw material, the ball milling balls and the ball milling medium is 1:4-10:1.5-5.

[0016] Preferably, in the preparation method, the microwave frequency of the microwave-assisted condition is 2 to 3 GHz.

[0017] Preferably, in the preparation method, the first heating operation process comprises the following steps: adjusting the input power of the microwave, and performing the first heating of the mixture until the reflected power reaches stability;

[0018] The first heating rate is 10-15°C / min.

[0019] Preferably, in the preparation method, the second temperature-raising operation process comprises the following steps: subjecting the mixed material to a second temperature-raising after the first temperature-raising, and adjusting the input power of the microwave under the condition of monitoring the reflected power;

[0020] The second heating rate is 5-10°C / min.

[0021] Preferably, in the preparation method, the sintering temperature is 600-800° C., and the sintering time is 10-30 min.

[0022] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The present invention is based on (K 0.48 Na 0.48 Li 0.04 )(Nb 0.95 Sb 0.05 )O3 ceramics as the basic system, based on composite perovskite Bi 0.5 (Na 0.7 K 0.3 ) 0.5 ZrO3 was used as the second phase doping and synthesized by microwave heating to construct a 0.94 (K 0.48 Na 0.48 Li 0.04 )(Nb 0.95 Sb 0.05 )O3-0.06Bi 0.5 (Na 0.7 K 0.3 ) 0.5 ZrO3 piezoelectric material system. Since microwaves have different heating effects on different media, the larger the loss tangent of the medium, the stronger its ability to absorb microwaves, resulting in microwave selective heating. The schematic diagram of microwave selective heating is shown in Figure 1As shown. By utilizing this characteristic of microwave selective heating, special microwave heating can be achieved by adding different dielectric materials and controlling the distribution of the dielectric. Some "sensitizers" (Bi source and Zr source, ZrO2 and Bi2O3 are used as examples to illustrate) that absorb microwaves can be added to induce chemical reactions. The "sensitizers" and microwaves undergo local resonance coupling energy transfer to form "microwave hot spots". ZrO2 and Bi2O3 respond quickly to microwaves in the microwave field, form color centers during microwave synthesis, and microwave-induced catalytic reactions occur. The temperature field uniformity during heating is good, and the synthesized powder grains grow perfectly to form a clear-cut cubic block morphology. In addition, due to the low-temperature and rapid heating characteristics of microwaves, the volatilization of alkali metal elements in the raw materials during the synthesis process is reduced, the possibility of the synthesized powder deviating from the stoichiometric ratio of the raw materials is reduced, and the purity of the synthesized powder is guaranteed. At the same time, the present invention constructs a phase structure state with two or more phases coexisting by doping ZrO2, Bi2O3, Li2CO3, Sb2O3 and other substances, thereby improving the piezoelectricity of potassium sodium niobate ceramics. Combined with the different influences on the microwave coupled thermal effect, plasma effect and microwave heating rate during the microwave synthesis process, the phenomenon of microwave induced catalytic reaction occurred (this phenomenon was proposed for the first time), and highly active powders with uniform and fine particles were obtained, which improved the piezoelectric properties of ceramics prepared in the later stage of the powder, and is expected to successfully replace lead-based piezoelectric ceramic materials.

[0024] (2) The present invention utilizes the intrinsic microwave absorption effect of the raw materials, and does not require the addition of auxiliary heating devices (such as the addition of SiC rods for auxiliary heating), and the method and device are simple. In addition, the microwave heating synthesis method of the present invention has a low reaction temperature (600-800°C) and a short synthesis time (10-30 minutes); the prepared piezoelectric ceramic powder is uniform and fine (300-500nm), has good dispersibility, and has high reaction activity, which is conducive to the sintering of the ceramics in the later stage. It is a preparation method with simple process, high efficiency, and environmental friendliness. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below.

[0026] Figure 1 Schematic diagram of the temperature field of microwave selective heating and conventional heating;

[0027] Figure 2 Schematic diagram of microwave synthesis of doped and modified potassium sodium niobate lead-free piezoelectric ceramic materials;

[0028] Figure 3 This is the XRD pattern of the modified potassium sodium niobate lead-free piezoelectric ceramic powder obtained in Example 1;

[0029] Figure 4This is a SEM image of the modified potassium sodium niobate lead-free piezoelectric ceramic powder obtained in Example 1;

[0030] Figure 5 This is a curve chart showing the changes of incident power, reflected power and temperature over time when preparing doped modified potassium sodium niobate powder in Example 1. DETAILED DESCRIPTION

[0031] The present invention provides a doped modified potassium sodium niobate lead-free piezoelectric ceramic material based on microwave synthesis, wherein the chemical formula of the doped modified potassium sodium niobate lead-free piezoelectric ceramic material is: 0.94 (K 0.48 Na 0.48 Li 0.04 )(Nb 0.95 Sb 0.05 )O3-0.06Bi 0.5 (Na 0.7 K 0.3 ) 0.5 ZrO3.

[0032] The present invention also provides a method for preparing a doped and modified potassium sodium niobate lead-free piezoelectric ceramic material based on microwave synthesis, comprising the following steps:

[0033] Mixing a K source, a Na source, a Li source, a Nb source, a Sb source, a Bi source and a Zr source according to a stoichiometric ratio in a chemical formula to obtain a mixture;

[0034] Under microwave-assisted conditions, the mixed material is subjected to a first heating and a second heating in sequence, and then sintered to obtain a doped and modified potassium sodium niobate lead-free piezoelectric ceramic material.

[0035] In the present invention, the K source preferably includes K2CO3 or KOH, and more preferably K2CO3.

[0036] In the present invention, the Na source preferably includes Na2CO3 or NaOH, and more preferably Na2CO3.

[0037] In the present invention, the Li source preferably includes Li2CO3, LiOH or LiF, further preferably includes Li2CO3 or LiOH, and more preferably is Li2CO3.

[0038] In the present invention, the Nb source preferably includes Nb2O5.

[0039] In the present invention, the Sb source preferably includes Sb2O3, Sb2S3 or Sb2O5, further preferably includes Sb2O3 or Sb2O5, and more preferably is Sb2O3.

[0040] In the present invention, the Bi source preferably includes Bi2O3, Bi2S3 or Bi(NO3)3 (Bi(NO3)3·5H2O), further preferably includes Bi2O3 or Bi(NO3)3, and more preferably is Bi2O3.

[0041] In the present invention, the Zr source preferably includes ZrO2, ZrCl4, BaZrO3 or ZrSiO4, further preferably includes ZrO2 or ZrCl4, and more preferably is ZrO2.

[0042] In the present invention, the K source, Na source, Li source, Nb source, Sb source, Bi source and Zr source are mixed according to the stoichiometric ratio in the chemical formula, preferably including the following steps:

[0043] The K source, Na source, Li source, Nb source, Sb source, Bi source and Zr source are respectively subjected to the first drying, and the K source, Na source, Li source, Nb source, Sb source, Bi source and Zr source are mixed according to the stoichiometric ratio in the chemical formula, and the obtained mixed raw materials are sequentially ball-milled and second dried.

[0044] In the present invention, the first drying temperature is preferably 100-150° C., more preferably 110-140° C., and more preferably 120° C.; the first drying time is preferably 1-3 h, more preferably 1.5-2.5 h, and more preferably 2 h.

[0045] In the present invention, the ball milling device is preferably a planetary ball mill. Specifically in the embodiment of the present invention, the model of the planetary ball mill is QM-3SP2.

[0046] In the present invention, the medium for ball milling is preferably ethanol or acetone, and more preferably ethanol.

[0047] In the present invention, the material of the grinding balls of the ball mill is preferably ZrO2.

[0048] In the present invention, the mass ratio of the mixed raw material, the balls of the ball mill and the medium of the ball mill is preferably 1:4-10:1.5-5, more preferably 1:4-8:1.5-3, and even more preferably 1:4:1.5.

[0049] In the present invention, the rotation speed of the ball mill is preferably 300-600 r / min, more preferably 320-450 r / min, and more preferably 325 r / min; the time of the ball mill is preferably 10-24 h, more preferably 10-18 h, and more preferably 12 h.

[0050] In the present invention, the temperature of the second drying is preferably 100-140°C, more preferably 110-130°C, and more preferably 110°C; the time of the second drying is preferably 12-48h, more preferably 18-36h, and more preferably 24h.

[0051] In the present invention, the device used in the microwave-assisted condition is preferably a multi-mode resonant cavity microwave oven.

[0052] In the present invention, the maximum input power of the multi-mode resonant cavity microwave oven is preferably 10 kW.

[0053] In the present invention, the microwave resonant cavity used in the microwave-assisted condition is preferably a microwave cavity of TE666 resonance mode.

[0054] In the present invention, the microwave frequency of the microwave-assisted condition is preferably 2 to 3 GHz, more preferably 2.2 to 2.6 GHz, and even more preferably 2.45 GHz.

[0055] In the present invention, the first heating operation process preferably includes the following steps: adjusting the input power of microwaves, and performing the first heating of the mixture until the reflected power reaches stability.

[0056] In the present invention, the first heating rate is preferably 10 to 15° C. / min, more preferably 11 to 14° C. / min, and more preferably 12° C. / min.

[0057] In the present invention, the second heating operation process preferably includes the following steps: subjecting the mixed material to a second heating after the first heating, and adjusting the input power of the microwaves under the condition of monitoring the reflected power.

[0058] In the present invention, the heating rate of the second heating is preferably 5 to 10° C. / min, more preferably 6 to 9° C. / min, and more preferably 8° C. / min.

[0059] In the present invention, the sintering temperature is preferably 600-800°C, more preferably 625-675°C, and more preferably 650°C; the sintering time is preferably 10-30 min, more preferably 15-25 min, and more preferably 20 min.

[0060] In the present invention, after the sintering, the method preferably further includes: naturally cooling to room temperature.

[0061] In the present invention, microwave synthesis relies on the dielectric loss of the material itself to complete the material heating, which belongs to the body heating inside the material. Compared with other traditional heating methods, it has incomparable advantages: the microwave synthesis energy comes from the inside of the reactant, the sample heats up quickly during heating, and the reactant can be heated comprehensively, quickly and evenly to increase the chemical reaction rate; it can synthesize high-purity, fine-particle, and uniformly distributed powder materials in a short time and at low temperature, and ensure the uniformity of its microstructure. In addition to the above-mentioned advantages of low-temperature rapid and overall heating, when using microwave heating to synthesize materials, for multi-phase mixed materials, microwaves also have the unique characteristic of "selective heating". Different materials have different dielectric losses, different responses to microwave heat, and different microwave thermal effects. Microwave-induced doping and catalysis phenomena will occur during the heating process, which is a unique feature of microwave heat sources. Based on this, the present invention utilizes the microwave selective heating effect and the microwave intrinsic microwave absorption effect to prepare a variety of doped raw materials in a heating method different from the traditional one, which can improve the sintering performance and piezoelectric properties of doped modified potassium sodium niobate piezoelectric ceramics.

[0062] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. 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.

[0063] Example 1

[0064] This embodiment provides a method for preparing a doped modified potassium sodium niobate lead-free piezoelectric ceramic material based on microwave synthesis, as shown in the schematic diagram Figure 2 As shown, the following steps are included:

[0065] Analytical pure chemical reagents K2CO3, Na2CO3, Li2CO3, Nb2O5, Sb2O3, Bi2O3, and ZrO2 were used as raw materials. Before mixing, the above raw materials were dried at 120°C for 2 hours to remove the adsorbed moisture, and then cooled and heated at 0.94 (K 0.48 Na 0.48 Li 0.04 )(Nb 0.95 Sb 0.05 )O3-0.06Bi 0.5 (Na 0.7 K 0.3 ) 0.5The stoichiometric ratio of ZrO3 is 0.2 mol of the modified potassium sodium niobate material, and the amount of each raw material is accurately weighed with an electronic scale; ZrO2 balls and anhydrous ethanol are added in a mass ratio of mixed raw materials: ZrO2 balls: anhydrous ethanol = 1:4:1.5, poured into a nylon ball mill, and mixed and ground for 12 hours using a planetary ball mill (model QM-3SP2) at a speed of 325 r / min; the ball-milled slurry is placed in an alumina crucible and dried at 110°C for 24 hours to obtain a mixture;

[0066] The dried mixture is placed in an alumina crucible, the crucible is placed in a heat preservation device without additive auxiliary heating, and the crucible and the device are placed in a multi-mode resonant cavity microwave oven with a frequency of 2.45 GHz, and heated in a microwave cavity of TE666 resonance mode; the microwave source is turned on, and the input power of the microwave is adjusted, so that the mixture is first heated at a rate of 12.5°C / min until the reflected power is stable; then the mixture is heated to 650°C at a rate of 7.5°C / min, while monitoring the reflected power, adjusting the input power of the microwave, and controlling the heat preservation time to 20 minutes, and then naturally cooling to room temperature to obtain a white doped modified potassium sodium niobate lead-free piezoelectric ceramic material.

[0067] The phase composition structure of the modified potassium sodium niobate lead-free piezoelectric ceramic powder obtained in Example 1 was tested by X-ray diffraction. The XRD pattern is shown in Figure 3 As shown. Figure 3 It can be seen that under the process conditions of microwave synthesis parameters of 650℃ for 20min, a perovskite structure was formed without the existence of secondary phase, indicating that Bi 0.5 (Na 0.7 K 0.3 ) 0.5 ZrO3 is completely dissolved into (K 0.48 Na 0.48 Li 0.04 )(Nb 0.95 Sb 0.05 )O3 lattice to form a solid solution and synthesize modified potassium sodium niobate powder with a pure perovskite structure.

[0068] The morphology of the modified potassium sodium niobate lead-free piezoelectric ceramic powder obtained in Example 1 was characterized by scanning electron microscopy. Figure 4 As shown. Figure 4 It can be seen that the product of Example 1 forms a potassium sodium niobate cubic structure, which is a characteristic of potassium sodium niobate piezoelectric material.

[0069] The particle size of the modified potassium sodium niobate lead-free piezoelectric ceramic powder obtained in Example 1 was measured by a laser particle size analyzer, and the result was 300-500 nm. This shows that the microwave heating synthesis method provided by the present invention not only saves energy, but also obtains a powder with a more regular morphology, and is a new and effective synthesis method.

[0070] In the microwave heating synthesis process of Example 1, the incident power, reflected power and temperature of the doped modified potassium sodium niobate powder are plotted as follows: Figure 5 As shown. Microwave heating is the conversion of microwave energy into thermal energy through microwave radiation. In addition to the advantages of low-temperature, fast and overall heating, microwave heating also has the unique characteristic of "selective heating". Different materials have different dielectric losses, different responses to microwave heat, and different microwave thermal effects. The reason for the above phenomenon is that non-thermal effects such as microwave coupling heat, microwave plasma thermal effect and microwave electric field enhancement effect have changed during microwave heating, thereby causing changes in high-temperature physical and chemical reactions. Under the action of microwave heat, Example 1 synthesized cubic powder with a particle size of about 500nm. Based on the above analysis, the present invention proposes "microwave induced catalytic reaction" for the first time, which provides a reference for future research on microwave synthesis of piezoelectric materials.

[0071] Example 2

[0072] This embodiment provides a method for preparing a doped modified potassium sodium niobate lead-free piezoelectric ceramic material based on microwave synthesis, comprising the following steps:

[0073] Analytical pure chemical reagents KOH, NaOH, LiOH, Nb2O5, Sb2O5, Bi2S3, ZrCl4 were used as raw materials. Before mixing, the above raw materials were dried at 100℃ for 3h to remove the adsorbed moisture. After cooling, they were heated to 0.94 (K 0.48 Na 0.48 Li 0.04 )(Nb 0.95 Sb 0.05 )O3-0.06Bi 0.5 (Na 0.7 K 0.3 ) 0.5 The stoichiometric ratio of ZrO3 is 0.2 mol of the modified potassium sodium niobate material, and the amount of each raw material is accurately weighed with an electronic scale; ZrO2 balls and anhydrous ethanol are added in a mass ratio of mixed raw materials: ZrO2 balls: anhydrous ethanol = 1:5:1.8, poured into a nylon ball mill, and mixed and ground for 10 hours using a planetary ball mill (model QM-3SP2) at a speed of 450 r / min; the ball-milled slurry is placed in an alumina crucible and dried at 100°C for 36 hours to obtain a mixture;

[0074] The dried mixture is placed in an alumina crucible, the crucible is placed in a heat preservation device without additive auxiliary heating, and the crucible and the device are placed in a multi-mode resonant cavity microwave oven with a frequency of 2.6 GHz, and heated in a microwave cavity of TE666 resonance mode; the microwave source is turned on, and the input power of the microwave is adjusted, so that the mixture is first heated at a rate of 10°C / min until the reflected power is stable; then the mixture is heated to 675°C at a rate of 5°C / min, while monitoring the reflected power, adjusting the input power of the microwave, and controlling the heat preservation time to 15 minutes, and then naturally cooled to room temperature to obtain a white doped modified potassium sodium niobate lead-free piezoelectric ceramic material.

[0075] Example 3

[0076] This embodiment provides a method for preparing a doped modified potassium sodium niobate lead-free piezoelectric ceramic material based on microwave synthesis, comprising the following steps:

[0077] Analytical pure chemical reagents K2CO3, Na2CO3, Li2CO3, Nb2O5, Sb2O3, Bi2O3, and ZrO2 were used as raw materials. Before mixing, the raw materials were dried at 140°C for 1 hour to remove the adsorbed moisture. After cooling, the raw materials were heated to 0.94 (K 0.48 Na 0.48 Li 0.04 )(Nb 0.95 Sb 0.05 )O3-0.06Bi 0.5 (Na 0.7 K 0.3 ) 0.5 The stoichiometric ratio of ZrO3 is 0.2 mol of the modified potassium sodium niobate material, and the amount of each raw material is accurately weighed with an electronic scale; ZrO2 balls and anhydrous ethanol are added in a mass ratio of mixed raw materials: ZrO2 balls: anhydrous ethanol = 1:6:2, poured into a nylon ball mill, and mixed and ground for 10 hours using a planetary ball mill (model QM-3SP2) at a speed of 600 r / min; the ball-milled slurry is placed in an alumina crucible and dried at 140°C for 18 hours to obtain a mixed material;

[0078] The dried mixture is placed in an alumina crucible, the crucible is placed in a heat preservation device without additive auxiliary heating, and the crucible and the device are placed in a multi-mode resonant cavity microwave oven with a frequency of 3 GHz, and heated in a microwave cavity of TE666 resonance mode; the microwave source is turned on, and the input power of the microwave is adjusted to heat the mixture at a rate of 15°C / min until the reflected power is stable; then the mixture is heated to 625°C at a rate of 10°C / min, while monitoring the reflected power, adjusting the input power of the microwave, and controlling the heat preservation time to 25 minutes, and then naturally cooling to room temperature to obtain a white doped modified potassium sodium niobate lead-free piezoelectric ceramic material.

[0079] In summary, the present invention utilizes the wave absorption effect of the raw material powder itself, adopts a direct microwave heating synthesis method, effectively exerts the advantages of microwave synthesis, and realizes the low-temperature and rapid synthesis of doped modified potassium sodium niobate lead-free piezoelectric ceramic powder materials, thereby obtaining a ceramic powder with good crystallization and high surface activity, and has low energy consumption, is environmentally friendly, and is conducive to the subsequent sintering of ceramics and optimization of performance.

[0080] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A doped and modified potassium sodium niobate lead-free piezoelectric ceramic material based on microwave synthesis, characterized in that: The chemical formula of the doped modified potassium sodium niobate lead-free piezoelectric ceramic material is: 0.94 (K 0.48 Na 0.48 Li 0.04 )(Nb 0.95 Sb 0.05 )O3-0.06Bi 0.5 (Na 0.7 K 0.3 ) 0.5 ZrO3.

2. The method for preparing a doped and modified potassium sodium niobate lead-free piezoelectric ceramic material based on microwave synthesis according to claim 1, characterized in that: The following steps are involved: Mixing a K source, a Na source, a Li source, a Nb source, a Sb source, a Bi source and a Zr source according to a stoichiometric ratio in a chemical formula to obtain a mixture; Under microwave-assisted conditions, the mixed material is subjected to a first heating and a second heating in sequence, and then sintered to obtain a doped and modified potassium sodium niobate lead-free piezoelectric ceramic material.

3. The preparation method according to claim 2, characterized in that: The K source includes K2CO3 or KOH, the Na source includes Na2CO3 or NaOH, the Li source includes Li2CO3, LiOH or LiF, the Nb source includes Nb2O5, the Sb source includes Sb2O3, Sb2S3 or Sb2O5, the Bi source includes Bi2O3, Bi2S3 or Bi(NO3)3, and the Zr source includes ZrO2, ZrCl4, BaZrO3 or ZrSiO4.

4. The preparation method according to claim 2, characterized in that: The mixing of the K source, the Na source, the Li source, the Nb source, the Sb source, the Bi source and the Zr source according to the stoichiometric ratio in the chemical formula specifically comprises the following steps: The K source, Na source, Li source, Nb source, Sb source, Bi source and Zr source are respectively subjected to the first drying, and the K source, Na source, Li source, Nb source, Sb source, Bi source and Zr source are mixed according to the stoichiometric ratio in the chemical formula, and the obtained mixed raw materials are sequentially ball-milled and second dried.

5. The preparation method according to claim 4, characterized in that: The first drying temperature is 100-150° C., and the first drying time is 1-3 hours; The second drying temperature is 100 to 140° C., and the second drying time is 12 to 48 hours.

6. The preparation method according to claim 4 or 5, characterized in that: The rotation speed of the ball mill is 300-600 r / min, the time of the ball mill is 10-24 h, the medium of the ball mill is ethanol or acetone, and the mass ratio of the mixed raw material, the grinding balls of the ball mill and the medium of the ball mill is 1:4-10:1.5-5.

7. The preparation method according to claim 2, characterized in that: The microwave frequency of the microwave-assisted condition is 2-3 GHz.

8. The preparation method according to claim 2 or 7, characterized in that: The first heating operation process comprises the following steps: adjusting the input power of the microwave, and performing the first heating of the mixed material until the reflected power reaches a stable state; The first heating rate is 10-15°C / min.

9. The preparation method according to claim 8, characterized in that: The second heating operation process comprises the following steps: heating the mixed material after the first heating for a second time, and adjusting the input power of the microwave under the condition of monitoring the reflected power; The second heating rate is 5-10°C / min.

10. The preparation method according to claim 7 or 9, characterized in that: The sintering temperature is 600-800° C., and the sintering time is 10-30 minutes.

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