Fine solid-phase sintering method of potassium niobate ceramic powder for inhibiting potassium volatilization

Abstract

A fine solid-phase sintering method of potassium niobate ceramic powder capable of inhibiting potassium volatilization comprises the following steps: firstly, weighing powder raw materials KHCO3 and Nb2O5 required for preparing potassium niobate with different masses according to a molar ratio of KHCO3 to Nb2O5 of (2-2.02): 1, carrying out multi-gradient sintering on the weighed powder raw materials, and according to a quantitative relationship between the mass of the powder raw materials subjected to multi-gradient sintering and sintering time, carrying out fine solid-phase sintering on the powder raw materials subjected to multi-gradient sintering and the sintering time of the powder raw materials subjected to multi-gradient sintering to obtain the potassium niobate ceramic powder capable of inhibiting potassium volatilization. Preliminarily preparing potassium niobate powder; and then, carrying out secondary sintering on the preliminarily prepared potassium niobate powder to obtain the final active potassium niobate powder, according to the invention, potassium bicarbonate insensitive to air is used as a raw material to replace potassium carbonate which is extremely easy to absorb moisture in the air, so that the volatilization of K element can be better controlled, and the problems that the potassium carbonate absorbs moisture and the prepared potassium niobate ceramic powder is easy to deviate from the ratio are solved; and by controlling the temperature and time when the K element volatilizes, the problem that the component deviation of the potassium niobate is aggravated due to the non-quantitative pre-sintering heat preservation time is avoided, and the powder process for accurately preparing potassium-containing oxide materials such as the potassium niobate is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of potassium niobate powder, and in particular relates to a fine solid-phase sintering method of potassium niobate ceramic powder capable of inhibiting potassium volatilization. Background Art

[0002] Potassium niobate (KNbO3) is a typical perovskite structure material, K+ ions occupy the top corners of the cube, Nb 5+ Occupies the body center position, O 2- Occupies the face-centered position. Potassium niobate undergoes multiple phase transitions from high temperature to low temperature, including cubic phase to tetragonal phase (435°C), orthorhombic phase (225°C) to trigonal phase (-10°C). Potassium niobate has unique physical properties such as piezoelectricity, thermoelectricity, and nonlinear optics and has been widely studied. Its devices made through various processes are widely used in technical fields such as optical transmission, frequency amplifiers, and information storage. As a kind of functional material, the composition and purity of potassium niobate powder directly determine the actual application performance of potassium niobate material. At present, the preparation of potassium niobate powder mainly includes solid phase method, sol-gel method, hydrothermal synthesis method, etc.

[0003] The solid phase method mainly uses potassium carbonate and niobium oxide as raw materials, and prepares powders through ball milling and pre-sintering. This method is simple and efficient, but the prepared powders have composition deviations, and the potassium carbonate raw material is very easy to absorb moisture, which increases the difficulty of preparing purer powders. The sol-gel method is a method that can prepare high-purity powders, but it also has composition deviations, and the cost of alcohol salts in the sol-gel method is relatively high, which limits its application. The hydrothermal method is mainly limited by the high pressure and high temperature of the equipment, and has a certain risk factor. The potassium hydroxide and niobium oxide generally used in the hydrothermal method often cannot react completely, and the phases produced cannot be finely controlled. It is also difficult to synthesize high-purity powders.

[0004] The presence of potassium carbonate in the raw materials, which is extremely sensitive to air, greatly affects the preparation process of potassium niobate powder. Potassium carbonate is highly hygroscopic. Generally speaking, the higher the temperature, the greater the humidity, and the larger the surface area in the air, the stronger the hygroscopicity. Potassium carbonate will form hydrates after absorbing moisture. If it is continuously exposed to air with high humidity, it will absorb carbon dioxide and turn into potassium bicarbonate, which directly affects the preparation of potassium niobate powder.

[0005] At present, the laboratory's preparation of potassium niobate oxide materials containing potassium (K) elements is mainly concentrated on solid phase method, hydrothermal method, sol-gel method and other processes. Each process has its own advantages and disadvantages. The hydrothermal method is usually carried out in a high temperature and high pressure water environment, and can prepare high-purity, good crystallinity nanomaterials. The prepared powder has good dispersibility and particle size. However, the hydrothermal method requires special high-pressure equipment, has high operating costs, and is not applicable to some water-sensitive materials. The sol-gel method can prepare potassium niobate powder with uniformly mixed components at the molecular level, and has a lower synthesis temperature. However, the cost of raw materials used in the sol-gel method is usually expensive, and some organic raw materials may be harmful to health, and the preparation cycle of powder is long, and the time cost is also high. As a traditional way to prepare ceramic powders, the solid phase method can realize the synthesis of powders in large quantities, and has the advantages of low cost, simple synthesis, and no need for special synthesis equipment.

[0006] The above synthesis methods will all have a certain degree of composition deviation due to the presence of K element. Hydrothermal and sol-gel methods, including potassium niobate powder prepared by solid-phase method, all have composition deviation. The composition deviation caused by hydrothermal method and sol-gel method is not easy to completely solve the composition deviation problem of potassium niobate material due to the limitations of their synthesis process.

[0007] The literature [Choi J, Ryu SY, Balcerski W, et al. Photocatalytic production of hydrogen on Ni / NiO / KNbO3 / CdS nanocomposites using visible light [J]. Journal of Materials Chemistry, 2008, 18. DOI: 10.1039 / b718535a.] uses a solid phase method to prepare potassium niobate materials, and the molar ratio of the raw materials is K2CO3: Nb2O5

[0008] =1:1 to obtain KNbO3 phase. The main method adopted is sintering after pressing, which is also an effective means to inhibit volatilization, but this method will greatly affect the sintering activity of the powder, and additionally introduce the influence of pressure, which in turn limits the final performance after sintering. The most important thing is that the K element begins to volatilize at 800℃, and the raw material K2CO3 has strong water absorption. It is extremely important to consider the error of water absorption when weighing, which further limits the powder phase purity of potassium niobate.

[0009] The literature [Zhao Deming, Mou Qingping, Luan Bo. Synthesis, characterization and performance study of potassium niobate [J]. Chemical Technology and Development 2012, 41 (3): 5. DOI: 10.3969 / j.issn.1671-9905.2012.03.008.] mentions a variety of different methods for preparing potassium niobate, among which the hydrothermal method and the sol-gel method can also prepare relatively good potassium niobate powder materials. The hydrothermal method has harsh reaction conditions, long reaction time, and cumbersome operation, especially for the proportion control requirements of raw materials. The main limiting factors of the sol-gel method are the high cost of alkoxide raw materials and the harsh preparation environment requirements, such as dry environment, nitrogen environment, etc. Summary of the invention

[0010] In order to overcome the problems existing in the above-mentioned prior art, the purpose of the present invention is to propose a fine solid-phase sintering method for potassium niobate ceramic powder that inhibits potassium volatilization, and potassium bicarbonate, which is insensitive to air, is used instead of potassium carbonate to complete the powder preparation process of potassium niobate; at the same time, considering the composition deviation caused by K volatilization during the preparation of potassium niobate powder, the sintering of potassium niobate powder is completed by combining multi-gradient sintering with a second sintering; the present invention finely controls the process of preparing potassium niobate by a solid-phase method, provides a quantitative relationship between powder mass and time, solves the problem of composition deviation caused by the volatilization of K element in potassium niobate, has the advantages of being simple and efficient, and is conducive to the preparation of potassium oxide powder in laboratories and industrial applications.

[0011] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0012] A fine solid phase sintering method for potassium niobate ceramic powder for inhibiting potassium volatilization, the specific steps are as follows:

[0013] Step 1, according to the molar ratio of KHCO3:Nb2O5=2-2.02:1, weigh the powder raw materials KHCO3 and Nb2O5 required to prepare potassium niobate of different masses, and perform multi-gradient sintering on the symmetrically taken powder raw materials to preliminarily prepare potassium niobate powder;

[0014] Step 2: sintering the potassium niobate powder prepared in step 1 for a second time to obtain the final active potassium niobate powder.

[0015] The quantitative relationship between the mass of the powder raw material and the sintering time for multi-gradient sintering in step 1 is as follows:

[0016] T=75.72-64.12*A+19.32*A 2 -1.98*A 3 (2.35≤A≤3.54, m≥20)

[0017] Wherein, A is the specific surface area, which is calculated as follows: A=m / S, m is the ratio mass g, S is the surface area of ​​the raw material powder after mixing, and T is the sintering time h.

[0018] The multi-gradient sintering method is specifically as follows:

[0019] First, the weighed powder raw material is heated between 270℃-300℃ and kept warm for 1h-1.75h to remove excess moisture and promote the decomposition of KHCO3; then, the temperature is raised to between 500℃-530℃ and kept warm for 1h-1.75h to completely decompose KHCO3 and maximize the activation of the pre-sintering activity of the powder; finally, the temperature is raised to 840℃-860℃ and sintered for 3h-6h to make potassium niobate powder.

[0020] The specific method of the second sintering is:

[0021] After the multi-gradient sintering is completed, the obtained potassium niobate powder is ball-milled for 4h-6h at 300-400rpm; then dried, and then heated to 680℃-700℃ and sintered for 3h-6h to obtain the final potassium niobate powder.

[0022] A potassium niobate ceramic powder capable of inhibiting potassium volatilization is obtained by the above-mentioned fine solid-phase sintering method.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] (1) The present invention utilizes potassium bicarbonate instead of potassium carbonate to carry out solid phase synthesis reaction. Potassium bicarbonate, which is insensitive to air, is used as a raw material to replace potassium carbonate, which is very easy to absorb moisture in the air. This can better control the volatilization of the K element and solve the problem that the prepared potassium niobate powder is easy to deviate from the proportion due to the moisture absorption characteristic of potassium carbonate. The present invention increases the accuracy of preparation.

[0025] (2) The present invention uses multi-gradient sintering to complete the drainage and potassium bicarbonate conversion process in the low temperature zone (270-300°C); complete the powder activation process in the medium temperature zone (500-530°C) to provide the most active powder for the next synthesis reaction; and quickly sinter in the high temperature zone (840-860°C); through the second sintering: first ball milling and drying the powder, and then performing a secondary sintering at 680°C-700°C on the powder, the activity and phase formation of the potassium niobate powder are further improved. The method is simple and efficient.

[0026] (3) The present invention controls the temperature and time of K element volatilization by selecting between the holding time of the pre-fired powder and the preparation amount of the powder, thereby avoiding the situation that the indefinite pre-fired holding time will also aggravate the deviation of the composition of potassium niobate, thereby achieving a powder process for accurately preparing potassium niobate and other potassium oxide materials.

[0027] In summary, compared with the currently more commonly used methods such as hydrothermal, microwave sintering, and electric field assisted sintering, the present invention can optimize the component accuracy and preparation cost and time to the greatest extent by controlling the raw materials, temperature, quality, and time in the solid phase preparation process of potassium niobate materials, which is beneficial to improving the accuracy and efficiency of the solid phase method for preparing potassium oxide-containing powder materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a quantitative diagram of the ratio of the present invention.

[0029] Figure 2 This is the multi-gradient sintering diagram of the present invention.

[0030] Figure 3 This is the second sintering diagram of the present invention.

[0031] Figure 4 This is the XRD spectrum of 20g potassium niobate material.

[0032] Figure 5 This is the XRD spectrum of 30g potassium niobate material.

[0033] Figure 6 This is the XRD spectrum of 40g potassium niobate material.

[0034] Figure 7 This is the XRD spectrum of 50g potassium niobate material.

[0035] Figure 8 Semi-quantitative analysis diagram of potassium niobate powder XRD, where: Figure 8 (a) is a phase structure analysis diagram of Example 1; Figure 8 (b) is a phase structure analysis diagram of Example 2; Figure 8 (c) is a phase structure analysis diagram of Example 3; Figure 8 (d) is the phase structure analysis diagram of Example 4. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0037] A fine solid phase sintering method for potassium niobate ceramic powder for inhibiting potassium volatilization, the specific steps are as follows:

[0038] Step 1. Weigh the powder raw materials KHCO3 and Nb2O5 required for preparing potassium niobate of different preparation masses according to the molar ratio of K:Nb=2-2.02:1, and perform multi-gradient sintering on the symmetrically taken powder raw materials to prepare potassium niobate powder: first, heat the weighed powder raw materials m grams at 270℃-300℃, keep warm for 1h-1.75h to remove excess moisture and promote the decomposition of KHCO3; then, heat to 500℃-530℃, keep warm for 1h-1.75h to completely decompose KHCO3 and maximize the activation of the pre-sintering activity of the powder; finally, heat to 840℃-860℃, sinter for 3h-6h to prepare potassium niobate powder; see Figure 1 , Figure 2 .

[0039] Step 2: Sinter the potassium niobate powder prepared in step 1 for the second time to obtain the final potassium niobate powder. Figure 3 .

[0040] After the multi-gradient sintering is completed, the obtained potassium niobate powder is ball-milled for 4h-6h at 300-400rpm to refine the powder particles and enhance the powder activity, and then dried and heated to 680℃-700℃ for sintering for 3h-6h to obtain the final potassium niobate powder.

[0041] The quantitative relationship between the mass of the powder raw material and the sintering time for multi-gradient sintering in step 1 is as follows:

[0042] T=75.72-64.12*A+19.32*A 2 -1.98*A 3 (2.35≤A≤3.54, m≥20)

[0043] Wherein, A is the specific surface area, which is calculated as follows: A=m / S, m is the mass of the powder raw material g, S is the surface area of ​​the raw material powder after mixing, and T is the sintering time h.

[0044] Example 1

[0045] A fine solid phase sintering method for potassium niobate ceramic powder for inhibiting potassium volatilization, the specific steps are as follows:

[0046] Step 1, weigh and prepare 20g of potassium niobate powder raw materials KHCO3 and Nb2O5 according to the molar ratio of KHCO3:Nb2O5=2:1, and perform multi-gradient sintering on the symmetrically taken powder raw materials to prepare potassium niobate powder: first, heat the weighed 20g powder raw materials at 270°C and keep them warm for 1h to remove excess moisture and promote the decomposition of KHCO3; then, heat to 500°C and keep them warm for 1h to completely decompose KHCO3 and maximize the activation of the pre-sintering activity of the powder; finally, heat to 840°C and sinter for 3h to prepare potassium niobate powder;

[0047] Step 2: Sinter the potassium niobate powder prepared in step 1 for a second time to obtain the final potassium niobate powder:

[0048] After the multi-gradient sintering is completed, the obtained potassium niobate powder is ball-milled for 6 hours at 400 rpm, and then dried, and then heated to 700° C. and sintered for 3 hours to obtain the final potassium niobate powder.

[0049] Example 2

[0050] A fine solid phase sintering method for potassium niobate ceramic powder for inhibiting potassium volatilization, the specific steps are as follows:

[0051] Step 1. Prepare 30g of potassium niobate powder raw materials KHCO3 and Nb2O5 by weighing according to the molar ratio of KHCO3:Nb2O5=2:1, and symmetrically take 30g of the powder raw materials for multi-gradient sintering to make potassium niobate powder: first, heat the weighed 30g of the powder raw materials at 280°C and keep it warm for 1.25h to remove excess moisture and promote the decomposition of KHCO3; then, heat it to 510°C and keep it warm for 1.25h to completely decompose KHCO3 and maximize the activation of the pre-sintering activity of the powder; finally, heat it to 850°C and sinter it for 4h to make potassium niobate powder;

[0052] Step 2: Sinter the potassium niobate powder prepared in step 1 for a second time to obtain the final potassium niobate powder:

[0053] After the multi-gradient sintering is completed, the obtained potassium niobate powder is ball-milled for 5.5 hours at 380 rpm, and then dried, and then heated to 690° C. and sintered for 4 hours to obtain the final potassium niobate powder.

[0054] Example 3

[0055] A fine solid phase sintering method for potassium niobate ceramic powder for inhibiting potassium volatilization, the specific steps are as follows:

[0056] Step 1. Prepare 40g of potassium niobate powder raw materials KHCO3 and Nb2O5 by weighing according to the molar ratio of KHCO3:Nb2O5=2:1, and symmetrically take 40g of the powder raw materials for multi-gradient sintering to make potassium niobate powder: first, heat the weighed 40g of the powder raw materials at 290°C and keep it warm for 1.5h to remove excess moisture and promote the decomposition of KHCO3; then, heat it to 520°C and keep it warm for 1.5h to completely decompose KHCO3 and maximize the activation of the pre-sintering activity of the powder; finally, heat it to 850°C and sinter it for 5h to make potassium niobate powder;

[0057] Step 2: Sinter the potassium niobate powder prepared in step 1 for a second time to obtain the final potassium niobate powder:

[0058] After the multi-gradient sintering is completed, the obtained potassium niobate powder is ball-milled for 5 hours at 350 rpm, and then dried, and then heated to 690° C. and sintered for 5 hours to obtain the final potassium niobate powder.

[0059] Example 4

[0060] A fine solid phase sintering method for potassium niobate ceramic powder for inhibiting potassium volatilization, the specific steps are as follows:

[0061] Step 1

[0062] According to the molar ratio of KHCO3:Nb2O5=2:1, 50g of potassium niobate powder raw materials KHCO3 and Nb2O5 were weighed and prepared, and 50g of the powder raw materials were symmetrically taken for multi-gradient sintering to make potassium niobate powder: first, the weighed 50g of powder raw materials were heated at 300℃ and kept warm for 1.75h to remove excess moisture and promote the decomposition of KHCO3; then, the temperature was raised to 530℃ and kept warm for 1.75h to completely decompose KHCO3 and maximize the activation of the pre-sintering activity of the powder; finally, the temperature was raised to 860℃ and sintered for 6h to make potassium niobate powder;

[0063] Step 2: Sinter the potassium niobate powder prepared in step 1 for a second time to obtain the final potassium niobate powder:

[0064] After the multi-gradient sintering is completed, the obtained potassium niobate powder is ball-milled for 4.5 hours at 300 rpm, and then dried, and then heated to 680° C. and sintered for 6 hours to obtain the final potassium niobate powder.

[0065] analyze:

[0066] First, we will refine the relevant processes of the preparation process. Figure 1 The relationship between potassium niobate with different configuration qualities and sintering time is given. Figure 2 The specific process of multi-gradient sintering separation is given. Figure 2 In the figure, stage (a) represents the low-temperature decomposition and transformation stage, at which the decomposition and transformation of potassium bicarbonate and the drainage of raw materials are completed. Stage (b) represents the medium-temperature decomposition and activation stage, at which the activation process of the powder is mainly completed. Stage (c) represents the high-temperature rapid synthesis stage, at which the phase formation process of potassium niobate powder is mainly completed. Stage (d) represents the natural cooling stage after the synthesis is completed. Figure 3 The main process of secondary sintering is shown. The prepared potassium niobate powder is ball-milled and dried, and then the powder is sintered for the second time to further improve the activity and phase formation of the potassium niobate powder. This is because for ceramic powder, the activation degree is higher when the pre-sintering temperature is lower.

[0067] Figures 4 to 7The XRD phase structure spectra of potassium niobate with a configuration of 20g, 30g, 40g and 50g are shown respectively. It is not difficult to conclude that the potassium niobate materials with all configuration qualities prepared by the refined process of the present invention have good phase formation effects, are all pure potassium niobate phases, and do not have impure phases (potassium-deficient phases, etc.). This is mainly manifested in that no other impure peaks appear in the figure, and the PDF card of potassium niobate has a high degree of consistency.

[0068] Figure 8 This is a further semi-quantitative phase structure analysis of the XRD spectrum of potassium niobate material. The figure proves that the powder materials obtained by the above-mentioned refined preparation process are all standard potassium niobate orthorhombic phase structures. Figure 8 a is the phase structure of 20g potassium niobate. It can be seen that the prepared powder contains three potassium niobate phases, namely Cm2m (green, PDF#32-0822), Bmm2 (cyan, PDF#71-2171), and Amm2 (red, PDF#71-0946). These three phases are all orthorhombic phase structures, and the only difference is the position orientation of the shortest axis of the unit cell, but they are all phase structures of pure potassium niobate. The contents of the three phase structures are 99.9% (Cm2m), 0.1% (Amm2), and 0.0% (Bmm2), respectively. This proves that the main phase of the powder synthesized by the preparation method of the present invention is a potassium niobate material with a Cm2m orthorhombic phase structure, containing a very small amount of Amm2 orthorhombic phase, and the Bmm2 orthorhombic phase structure basically does not exist and can be ignored. This also further illustrates that the potassium niobate synthesized by this method does not have the existence of impurity phases (potassium-deficient phases, etc.), and can be relatively simple to achieve the preparation of pure orthorhombic potassium niobate ceramic powder. Figure 8 b, c, and d are phase structures of 30g, 40g, and 50g potassium niobate, respectively. The powder structures prepared are similar to Figure 8 The conclusions in a are consistent, that is, the potassium niobate powder obtained is mainly potassium niobate with Cm2m orthorhombic phase structure, and the content is above 99.9%, while the content of potassium niobate with Amm2 and Bmm2 orthorhombic phase structure is less than 0.1%, which can be considered as high-purity potassium niobate phase in terms of chemical composition. (It should be noted that Figure 8 The E value represents the target value of the refined fitting, and the R value represents the actual value. During the analysis process, the closer the R value is to the E value, the higher the credibility. It is generally believed that the R value error is within 10% and the result is credible. Figure 8 All the error values ​​are less than 10%, and the results are reliable.

[0069] In summary, the refined solid-phase sintering process used in the present invention is effective in inhibiting potassium volatilization, and can simply and efficiently prepare potassium niobate materials with a higher purity phase. It makes up for the defects of existing solid-phase sintering technical means, avoids the inherent shortcomings of synthesis technologies such as hydrothermal method and sol-gel method, and can achieve low-cost, fast and efficient synthesis of ceramic powder materials, greatly improves the experimental technical process, and optimizes the existing solid-phase sintering technical means. The present invention is a reliable and feasible method for preparing potassium niobate ceramic powder.

Claims

1. A fine solid phase sintering method for potassium niobate ceramic powder to inhibit potassium volatilization, characterized in that: The specific steps are as follows: Step 1, according to the molar ratio of KHCO3:Nb2O5=2-2.02:1, weigh the powder raw materials KHCO3 and Nb2O5 required to prepare potassium niobate of different masses, and perform multi-gradient sintering on the symmetrically taken powder raw materials to preliminarily prepare potassium niobate powder; Step 2: sintering the potassium niobate powder prepared in step 1 for a second time to obtain the final active potassium niobate powder.

2. The fine solid phase sintering method of potassium niobate ceramic powder for inhibiting potassium volatilization according to claim 1 is characterized in that: The quantitative relationship between the mass of the powder raw material and the sintering time for multi-gradient sintering in step 1 is as follows: T=75.72-64.12*A+19.32*A 2 -1.98*A 3 (2.35≤A≤3.54,m≥20) Wherein, A is the specific surface area, which is calculated as follows: A=m / S, m is the mass of the powder raw material g, S is the surface area of ​​the raw material powder after mixing, and T is the sintering time h.

3. The fine solid phase sintering method of potassium niobate ceramic powder for inhibiting potassium volatilization according to claim 1 or 2, characterized in that: The multi-gradient sintering method is specifically as follows: First, the weighed powder raw material is heated between 270℃-300℃ and kept warm for 1h-1.75h to remove excess moisture and promote the decomposition of KHCO3; then, the temperature is raised to between 500℃-530℃ and kept warm for 1h-1.75h to completely decompose KHCO3 and maximize the activation of the pre-sintering activity of the powder; finally, the temperature is raised to 840℃-860℃ and sintered for 3h-6h to make potassium niobate powder.

4. The fine solid phase sintering method of potassium niobate ceramic powder for suppressing potassium volatilization according to claim 1 is characterized in that: The specific method of the second sintering is: After the multi-gradient sintering is completed, the obtained potassium niobate powder is ball-milled for 4h-6h at 300-400rpm; then dried, and then heated to 680℃-700℃ and sintered for 3h-6h to obtain the final potassium niobate powder.

5. The fine solid phase sintering method of potassium niobate ceramic powder for inhibiting potassium volatilization according to claim 1, characterized in that: The specific steps are as follows: Step 1, weigh and prepare 20g of potassium niobate powder raw materials KHCO3 and Nb2O5 according to the molar ratio of KHCO3:Nb2O5=2:1, and perform multi-gradient sintering on the symmetrically taken powder raw materials to prepare potassium niobate powder: first, heat the weighed 20g powder raw materials at 270°C and keep them warm for 1h to remove excess moisture and promote the decomposition of KHCO3; then, heat to 500°C and keep them warm for 1h to completely decompose KHCO3 and maximize the activation of the pre-sintering activity of the powder; finally, heat to 840°C and sinter for 3h to prepare potassium niobate powder; Step 2: Sinter the potassium niobate powder prepared in step 1 for a second time to obtain the final potassium niobate powder: After the multi-gradient sintering is completed, the obtained potassium niobate powder is ball-milled for 6 hours at 400 rpm, and then dried, and then heated to 700° C. and sintered for 3 hours to obtain the final potassium niobate powder.

6. The fine solid phase sintering method of potassium niobate ceramic powder for suppressing potassium volatilization according to claim 1, characterized in that: The specific steps are as follows: Step 1. Prepare 30g of potassium niobate powder raw materials KHCO3 and Nb2O5 by weighing according to the molar ratio of KHCO3:Nb2O5=2:1, and symmetrically take 30g of the powder raw materials for multi-gradient sintering to make potassium niobate powder: first, heat the weighed 30g of the powder raw materials at 280°C and keep it warm for 1.25h to remove excess moisture and promote the decomposition of KHCO3; then, heat it to 510°C and keep it warm for 1.25h to completely decompose KHCO3 and maximize the activation of the pre-sintering activity of the powder; finally, heat it to 850°C and sinter it for 4h to make potassium niobate powder; Step 2: Sinter the potassium niobate powder prepared in step 1 for a second time to obtain the final potassium niobate powder: After the multi-gradient sintering is completed, the obtained potassium niobate powder is ball-milled for 5.5 hours at 380 rpm, and then dried, and then heated to 690° C. and sintered for 4 hours to obtain the final potassium niobate powder.

7. The fine solid phase sintering method of potassium niobate ceramic powder for suppressing potassium volatilization according to claim 1 is characterized in that: The specific steps are as follows: Step 1. Prepare 40g of potassium niobate powder raw materials KHCO3 and Nb2O5 by weighing according to the molar ratio of KHCO3:Nb2O5=2:1, and symmetrically take 40g of the powder raw materials for multi-gradient sintering to make potassium niobate powder: first, heat the weighed 40g of the powder raw materials at 290°C and keep it warm for 1.5h to remove excess moisture and promote the decomposition of KHCO3; then, heat it to 520°C and keep it warm for 1.5h to completely decompose KHCO3 and maximize the activation of the pre-sintering activity of the powder; finally, heat it to 850°C and sinter it for 5h to make potassium niobate powder; Step 2: Sinter the potassium niobate powder prepared in step 1 for a second time to obtain the final potassium niobate powder: After the multi-gradient sintering is completed, the obtained potassium niobate powder is ball-milled for 5 hours at 350 rpm, and then dried, and then heated to 690° C. and sintered for 5 hours to obtain the final potassium niobate powder.

8. The fine solid phase sintering method of potassium niobate ceramic powder for suppressing potassium volatilization according to claim 1, characterized in that: The specific steps are as follows: Step 1. Prepare 50g of potassium niobate powder raw materials KHCO3 and Nb2O5 by weighing according to the molar ratio of KHCO3:Nb2O5=2:1, and symmetrically take 50g of the powder raw materials for multi-gradient sintering to make potassium niobate powder: first, heat the weighed 50g of the powder raw materials at 300°C and keep it warm for 1.75h to remove excess moisture and promote the decomposition of KHCO3; then, heat it to 530°C and keep it warm for 1.75h to completely decompose KHCO3 and maximize the activation of the pre-sintering activity of the powder; finally, heat it to 860°C and sinter it for 6h to make potassium niobate powder; Step 2: Sinter the potassium niobate powder prepared in step 1 for a second time to obtain the final potassium niobate powder: After the multi-gradient sintering is completed, the obtained potassium niobate powder is ball-milled for 4.5 hours at 300 rpm, and then dried, and then heated to 680° C. and sintered for 6 hours to obtain the final potassium niobate powder.

9. A potassium niobate ceramic powder with suppressed potassium volatilization, obtained by any one of the fine solid phase sintering methods of claims 1 to 8 above.

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