阅读说明：本技术 一种铌酸钾钠粉体的合成方法及应用 (Synthesis method and application of potassium-sodium niobate powder ) 是由 张树君 夏方诠 于 2020-07-23 设计创作，主要内容包括：本发明提供了一种铌酸钾钠粉体的合成方法及应用。该技术方案以KOH和NaOH构建熔盐热体系,以远低于二者熔点的温度形成液态碱液,而后控制温度与Nb<Sub>2</Sub>O<Sub>5</Sub>粉体反应,收集反应得到的固体沉淀,经洗涤、真空干燥得到产物；该方法以较低温度实现熔盐法制备铌酸钾钠粉体,降低了设备要求及工艺难度；同时,得益于熔盐法的自身优势,可通过调节熔盐组分的用量、反应温度以及反应时间来控制粉体的成分组成、形貌和粒径大小。在此基础上,本发明采用无胶制胚工艺,将铌酸钾钠前驱体装模后加二次蒸馏水,再在特定温度、压力下热压成型；该制坯工艺不需要排胶过程,制备的铌酸钾钠胚体密度高,利于进一步合成高性能的铌酸钾钠压电陶瓷。(The invention provides a synthesis method and application of potassium-sodium niobate powder. The technical scheme is that a molten salt thermal system is constructed by KOH and NaOH, liquid alkali liquor is formed at a temperature far lower than the melting points of the KOH and the NaOH, and then the temperature and Nb are controlled 2 O 5 Reacting powder, collecting solid precipitate obtained by the reaction, washing and drying in vacuum to obtain a product; the method realizes the preparation of the potassium-sodium niobate powder by the molten salt method at a lower temperature, and reduces the equipment requirement and the process difficulty; meanwhile, the advantages of the molten salt method are benefited, and the powder composition can be controlled by adjusting the dosage of the molten salt components, the reaction temperature and the reaction timeThe composition, the appearance and the particle size. On the basis, the invention adopts a glue-free blank making process, the potassium-sodium niobate precursor is filled into a mould, secondary distilled water is added, and then hot-press forming is carried out at specific temperature and pressure; the blank making process does not need a glue discharging process, and the prepared potassium-sodium niobate blank has high density and is beneficial to further synthesizing high-performance potassium-sodium niobate piezoelectric ceramics.)

1. A method for synthesizing potassium-sodium niobate powder is characterized by comprising the following steps: mixing KOH and NaOH, heating to 180-240 ℃, and keeping the temperature until liquid alkali liquor is formed; adding Nb thereto₂O₅Uniformly mixing, and reacting at 180-240 ℃ for 8-12 h; and then carrying out solid-liquid separation, washing a solid phase to be neutral, and drying in vacuum to obtain the potassium-sodium niobate powder.

2. The method for synthesizing potassium-sodium niobate powder according to claim 1, wherein the holding time is 30 min.

3. The method for synthesizing potassium-sodium niobate powder according to claim 1, wherein the solid-liquid separation is manual liquid pouring or centrifugal separation.

4. The method for synthesizing potassium-sodium niobate powder according to claim 1, wherein the washing to neutrality is carried out using dilute hydrochloric acid and distilled water.

5. The method for synthesizing potassium-sodium niobate powder according to claim 4, wherein the washing to neutrality comprises the following steps: cooling the solid phase to room temperature, adding distilled water to dissolve the residual KOH and NaOH, and centrifugally washing and precipitating once; adding 6mol/L HCl solution into the precipitate, adjusting the pH value of the solution to be neutral, and neutralizing the residual KOH and NaOH; and (4) carrying out suction filtration, and sequentially carrying out centrifugal washing on the precipitate by using secondary redistilled water and ethanol.

6. The method for synthesizing potassium-sodium niobate powder according to claim 1, wherein the temperature of the vacuum drying is 100 ℃ and the time of the vacuum drying is 4 hours.

7. The method for preparing the potassium-sodium niobate precursor body by applying the potassium-sodium niobate powder of any one of claims 1 to 6, characterized by comprising the following steps: adding the potassium-sodium niobate powder into a mould, and adding secondary distilled water; and (3) applying pressure of 10Mpa to a hot press, heating to 150 ℃, keeping the temperature and the pressure for 8 hours, and naturally cooling to room temperature to obtain the potassium-sodium niobate precursor body.

8. The method of claim 7 wherein the potassium sodium niobate powder is added in an amount of 0.5g, the mold is a0.5 inch diameter stainless steel mold, and the redistilled water is added in an amount of 100 μ L.

9. The method for preparing potassium-sodium niobate piezoelectric ceramics by using the potassium-sodium niobate precursor body of claim 8, characterized by comprising the steps of: and sintering the potassium-sodium niobate precursor blank at 1100 ℃ for 8h, and naturally cooling to room temperature.

10. The method of claim 9, further comprising the steps of: and naturally cooling to room temperature, and then cutting and polishing the mixture.

Technical Field

The invention relates to the technical field of piezoelectric ceramics, in particular to a synthesis method and application of potassium-sodium niobate powder.

Background

The piezoelectric material is a functional material with interconversion between electric energy and mechanical energy. Piezoelectric ceramics have both positive piezoelectric effect (i.e., piezoelectric ceramics can generate charges on the surface when subjected to external force) and inverse piezoelectric effect (i.e., piezoelectric ceramics can generate deformation under the action of external electric field), and thus are widely applied to electronic devices such as transducers, sensors, drivers, energy collectors, and the like. The piezoelectric ceramics not only have wide application in industrial and civil products, but also have a large number of applications in military affairs. In the past decades, lead-based piezoelectric materials have occupied a major share of the market due to their excellent piezoelectric properties, however, in order to protect the environment and satisfy the sustainable development concept of human beings, the search for lead-free piezoelectric materials with high performance has been a problem to be solved urgently in this field.

However, the NKN ceramic powder synthesized by the traditional solid phase method has the defects of low purity, uneven particle distribution, low activity, difficult sintering and the like, so that the high-performance NKN ceramic is difficult to prepare. It is reported that Na prepared by the conventional solid phase method_0.5K_0.5NbO₃Ceramic, piezoelectric constant d₃₃Only 80 pC/N.

In order to synthesize ceramic powder with uniform particle size and high sintering activity, chemical preparation methods such as sol-gel method, molten salt method, hydrothermal method and the like are used to synthesize NKN ceramic powder. The molten salt method is a simple and effective method for synthesizing high-activity and high-purity powder in a short time at a low reaction temperature, and has the advantage that the shape and size of the powder can be controlled by adjusting the amount of molten salt, the synthesis temperature and the heat preservation time. The Yangjianfeng and the like are successfully synthesized at 700 ℃ by adopting a molten salt growth method (K)_0.5Bi_0.5)TiO₃The research result of the ceramic powder shows that the shape of the nano rod-shaped powder is beneficial to improving the sintering activity, and the relative density reaches 98 percent. Kudzuvine petrel and the like research the molten salt content and temperature pair KNbO₃The influence of the powder structure and the morphology analyzes the mechanism of synthesizing the powder by the molten salt method, so that KNbO₃Compared with the traditional method, the synthesis temperature of the powder is reduced by 200 ℃. Lilishong and the like successfully synthesize 0.96Na0.52K0.48Nb0.9Ta0.1O3-0.04LiSbO3 powder by adopting a molten salt growth method at a lower temperature, and the high-performance piezoelectric ceramic is prepared by using the powder. Li Yueming professor and the like adopts a molten salt method to synthesize Na at 800 DEG C_0.5K_0.5NbO₃Ceramic powder sintered into ceramic sample at 1060 deg.C and piezoelectric constant d₃₃Reaching 124 pC/N. However, the synthesis temperature for preparing the powder by using the molten salt heat is higher, and the requirements on vessels and equipment are relatively higher, so that the technology for synthesizing the potassium-sodium niobate powder at a lower temperature is of great significance for reducing energy consumption and simplifying the process.

In addition, the general process of forming potassium sodium niobate powder into embryo needs to add glue into the powder, form the powder through mould pressure, and then form a stable embryo body through a high-temperature glue removing process. The process control in the glue discharging process has great influence on the density and the mechanical strength of the ceramic formed after the blank body is sintered.

Disclosure of Invention

The invention aims to overcome the technical defects of the prior art, and provides a method for synthesizing potassium-sodium niobate powder and application thereof, so as to solve the technical problem of overhigh synthesis temperature in the process of synthesizing a potassium-sodium niobate precursor by a conventional molten salt growth method.

The invention also aims to solve the technical problem that the conventional method for preparing the blank by using the potassium-sodium niobate precursor needs to add glue, and has great influence on the density and the mechanical strength of the ceramic formed by sintering the blank body.

In order to achieve the technical purpose, the invention adopts the following technical scheme:

a method for synthesizing potassium-sodium niobate powder comprises the following steps: mixing KOH and NaOH, heating to 180-240 ℃, and keeping the temperature until liquid alkali liquor is formed; adding Nb thereto₂O₅Uniformly mixing, and reacting at 180-240 ℃ for 8-12 h; and then carrying out solid-liquid separation, washing a solid phase to be neutral, and drying in vacuum to obtain the potassium-sodium niobate powder.

Preferably, the holding time is 30 min.

Preferably, the solid-liquid separation is manually pouring the liquid or centrifugal separation.

Preferably, the washing to neutrality is achieved using dilute hydrochloric acid and distilled water.

Preferably, the washing to neutrality comprises the following steps: cooling the solid phase to room temperature, adding distilled water to dissolve the residual KOH and NaOH, and centrifugally washing and precipitating once; adding 6mol/L HCl solution into the precipitate, adjusting the pH value of the solution to be neutral, and neutralizing the residual KOH and NaOH; and (4) carrying out suction filtration, and sequentially carrying out centrifugal washing on the precipitate by using secondary redistilled water and ethanol.

Preferably, the temperature of the vacuum drying is 100 ℃, and the time period of the vacuum drying is 4 hours.

On the basis of the technical scheme, the invention further provides a method for preparing a potassium-sodium niobate precursor body by applying the potassium-sodium niobate powder, which comprises the following steps: adding the potassium-sodium niobate powder into a mould, and adding secondary distilled water; and (3) applying pressure of 10Mpa to a hot press, heating to 150 ℃, keeping the temperature and the pressure for 8 hours, and naturally cooling to room temperature to obtain the potassium-sodium niobate precursor body.

Preferably, the amount of potassium-sodium niobate powder added is 0.5g, the mold is a0.5 inch diameter stainless steel mold, and the amount of redistilled water added is 100. mu.L.

On the basis of the technical scheme, the invention further provides a method for preparing the potassium-sodium niobate piezoelectric ceramic by applying the potassium-sodium niobate precursor blank, which comprises the following steps: and sintering the potassium-sodium niobate precursor blank at 1100 ℃ for 8h, and naturally cooling to room temperature.

Preferably, the method further comprises the following steps: and naturally cooling to room temperature, and then cutting and polishing the mixture.

In the above technical scheme, the mixture of sodium hydroxide and potassium hydroxide can form a molten salt thermal system, and the system can be converted from a solid state to a liquid state at 165 ℃ and is far lower than the melting point of the sodium hydroxide or the potassium hydroxide alone. After the temperature of the reaction molten salt thermal system is controlled to be higher than 180-220 ℃, a proper amount of niobium pentoxide powder is added, and the niobium pentoxide can fully react with high-concentration high alkali liquor in the molten salt thermal system. And after 8-12 hours of reaction, carrying out centrifugal separation on the precipitate, washing the precipitate to be neutral by using diluted hydrochloric acid and distilled water, and carrying out vacuum drying at 100 ℃ to obtain the product, namely the potassium-sodium niobate precursor KxNa (1-x) NbOx. By adjusting the ratio of sodium hydroxide/potassium hydroxide in the molten salt system, the ratio of potassium ions and sodium ions in the precursor can be properly adjusted, and the potassium-sodium niobate piezoelectric ceramics with different ratios of sodium ions and potassium ions can be obtained after calcination.

The process for preparing the potassium-sodium niobate precursor based on the molten salt growth method has the advantages of simple and convenient material synthesis, simple and convenient preparation and low material price; and the glue-free blank forming technology is combined, the glue discharging process of the traditional process is not needed, and the prepared potassium-sodium niobate blank has high density and is beneficial to synthesizing high-performance potassium-sodium niobate piezoelectric ceramics.

The invention provides a synthesis method and application of potassium-sodium niobate powder. The technical scheme is that a molten salt thermal system is constructed by KOH and NaOH, liquid alkali liquor is formed at a temperature far lower than the melting points of the KOH and the NaOH, and then the temperature and Nb are controlled₂O₅Reacting powder, collecting solid precipitate obtained by the reaction, washing and drying in vacuum to obtain a product; the method realizes the preparation of the potassium-sodium niobate powder by the molten salt method at a lower temperature, and reduces the equipment requirement and the process difficulty; meanwhile, thanks to the advantages of the molten salt method, the composition, morphology and particle size of the powder can be controlled by adjusting the dosage, reaction temperature and reaction time of the molten salt components. On the basis, the invention adopts a glue-free blank making process, the potassium-sodium niobate precursor is filled into a mould, secondary distilled water is added, and then hot-press forming is carried out at specific temperature and pressure; the blank making process does not need a glue discharging process, and the prepared potassium-sodium niobate blank has high density and is beneficial to further synthesizing high-performance potassium-sodium niobate piezoelectric ceramics.

Drawings

FIG. 1 is a flow chart of the synthesis process of potassium-sodium niobate ceramic in the present invention.

FIG. 2 is a scanning electron microscope image of the potassium-sodium niobate precursor powder in the present invention.

FIG. 3 is an XRD pattern of the potassium-sodium niobate piezoelectric ceramic of the present invention.

FIG. 4 is a photograph of a real object of the potassium-sodium niobate piezoelectric ceramic of the present invention.

Detailed Description

Hereinafter, specific embodiments of the present invention will be described in detail. Well-known structures or functions may not be described in detail in the following embodiments in order to avoid unnecessarily obscuring the details. Approximating language, as used herein in the following examples, may be applied to identify quantitative representations that could permissibly vary in number without resulting in a change in the basic function. Unless defined otherwise, technical and scientific terms used in the following examples have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.