A fine solid phase sintering method for inhibiting potassium volatilization of potassium niobate ceramic powder

Abstract

The application discloses a fine solid-phase sintering method for inhibiting potassium volatilization of potassium niobate ceramic powder, and first, according to the molar ratio of KHCO3:Nb2O5=2-2.02:1, the powder raw materials KHCO3 and Nb2O5 required for preparing different mass of potassium niobate are weighed, and the weighed powder raw materials are subjected to multi-gradient sintering, and according to the quantitative relationship between the mass of the multi-gradient sintered powder raw materials and the sintering time, the potassium niobate powder is preliminarily prepared; then, the preliminarily prepared potassium niobate powder is subjected to second sintering, and the final active potassium niobate powder is obtained; the potassium bicarbonate which is not sensitive to air is used as the raw material to replace the potassium carbonate which is easy to absorb moisture in the air, the volatilization of the K element can be better controlled, the characteristics of the potassium carbonate absorbing moisture and the problem that the prepared potassium niobate ceramic powder deviates from the proportioning are solved; and through controlling the temperature and time when the K element volatilizes, the composition deviation of the potassium niobate caused by the indefinite pre-sintering holding time is avoided, and the powder process for accurately preparing the potassium niobate and other potassium-containing oxide materials is achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of preparation of potassium niobate powder, and particularly relates to a fine solid-phase sintering method for potassium niobate ceramic powder. BACKGROUND

[0002] Potassium niobate (KNbO3) is a typical material with perovskite structure, K+ions occupy the cubic corner position, Nb 5+ occupies the body center position, and O 2- occupies the face center position. Potassium niobate undergoes multiple phase transition processes from high temperature to low temperature, including cubic phase to tetragonal phase (435℃), orthorhombic phase (225℃) to rhombohedral phase (-10℃). Potassium niobate has unique physical properties such as piezoelectricity, thermoelectricity, and nonlinear optics, and is widely studied. Devices made by various processes are widely used in optical transmission, frequency amplifiers, information storage and other technical fields. As a functional material, the composition and purity of the potassium niobate powder directly determine the actual application performance of the potassium niobate material. At present, the preparation of potassium niobate powder mainly includes solid-phase method, sol-gel method, and hydrothermal synthesis method.

[0003] The solid-phase method mainly uses potassium carbonate and niobium oxide as raw materials, and then prepares the powder through ball milling and pre-sintering. This method is simple and efficient, but the prepared powder has composition deviation, and the potassium carbonate raw material is extremely hygroscopic, which increases the difficulty of preparing pure powder. The sol-gel method is a method that can prepare high-purity powder, but it also has composition deviation, and the cost of alcoholates in the sol-gel method is relatively high, which limits its application. The hydrothermal method is mainly limited by the high pressure and high heat of the equipment, which has a certain risk coefficient, and the potassium hydroxide and niobium oxide used in the hydrothermal method often cannot completely react, and the generated phase cannot be precisely controlled, so it is also difficult to synthesize high-purity powder.

[0004] Because of the existence of potassium carbonate which is extremely sensitive to air in the raw materials, it greatly affects the preparation process of potassium niobate powder. Potassium carbonate has strong hygroscopicity. Generally speaking, the higher the temperature in the air, the greater the humidity, and the larger the surface area, the stronger the hygroscopicity. After the absorption of water, potassium carbonate will form a hydrate, and if it is exposed to air with high humidity all the time, it will absorb carbon dioxide and change into potassium bicarbonate, which directly affects the preparation of potassium niobate powder.

[0005] Currently, the preparation of potassium-containing (K) oxide potassium niobate materials in the laboratory is mainly focused 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, well-crystallized nanomaterials with good dispersibility and particle size. However, the hydrothermal method requires special high-pressure equipment, has high operating cost, and is not suitable for some water-sensitive materials. The sol-gel method can prepare potassium niobate powders with uniform component mixing at the molecular level, and has a relatively low synthesis temperature. However, the raw materials used in the sol-gel method are usually expensive, some organic raw materials may be harmful to health, and the preparation of powders requires a long period of time and high time cost. As a traditional method for preparing ceramic powders, the solid phase method can realize the synthesis of powders in large quantities, has low cost, simple synthesis, and does not require special synthesis equipment.

[0006] Due to the presence of K element, the above synthesis methods will have a certain degree of composition deviation. The potassium niobate powders prepared by hydrothermal and sol-gel methods, including solid phase method, all have composition deviation. The composition deviation caused by hydrothermal and sol-gel methods cannot completely solve the composition deviation problem of potassium niobate materials due to the limitations of the synthesis process.

[0007] In the literature [Choi J, Ryu S Y, 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.], potassium niobate materials were prepared by solid phase method, and the molar ratio of raw materials 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. However, this method greatly affects the sintering activity of the powder, and additionally introduces the influence factor of pressure, thereby limiting the performance after final sintering. Most importantly, K element starts to volatilize at 800℃, and the raw material K2CO3 has strong water absorption. It is extremely important to consider the water absorption error when weighing, which further limits the phase purity of potassium niobate powder.

[0009] The document [Zhao, Miao Qingping, Lan Bo. Potassium niobate synthesis, characterization and performance research [J]. Chemical technology and development, 2012, 41(3): 5. DOI: 10.3969 / j.issn.1671-9905.2012.03.008.] mentioned a variety of different ways to prepare potassium niobate, among which the hydrothermal method and the sol-gel method can also prepare relatively good potassium niobate powder materials. The reaction conditions of the hydrothermal method are harsh, the reaction time is long, the operation is complicated, especially the control of the proportion of the raw materials is particularly demanding. The main limiting factor of the sol-gel method is the high cost of alkoxide raw materials, and the harsh preparation environment requirements, such as dry environment, nitrogen environment, etc. SUMMARY

[0010] In order to overcome the problems existing in the prior art, the purpose of the present application is to provide a fine solid phase sintering method of potassium niobate ceramic powder for inhibiting potassium volatilization, which uses potassium bicarbonate which is not sensitive to air to replace potassium carbonate to complete the preparation process of potassium niobate powder; at the same time, considering the composition deviation caused by K volatilization during the preparation of potassium niobate powder, the combination of multi-gradient sintering and second sintering is used to complete the sintering of potassium niobate powder; the present application finely regulates and controls the process of preparing potassium niobate by solid phase method, gives the quantitative relationship between powder quality and time, solves the composition deviation problem caused by K element volatilization in potassium niobate, has the advantages of simplicity and efficiency, and is beneficial to the preparation of potassium-containing oxide powder in laboratory and industrial applications.

[0011] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

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

[0013] Step 1, according to the molar ratio KHCO3:Nb2O5=2-2.02:1, weigh the powder raw materials KHCO3 and Nb2O5 required for preparing different quality of potassium niobate, and multi-gradient sinter the weighed powder raw materials to preliminarily prepare potassium niobate powder;

[0014] Step 2, the potassium niobate powder prepared in step 1 is subjected to second sintering to obtain the final active potassium niobate powder.

[0015] The quantitative relationship between the mass of the powder raw materials subjected to multi-gradient sintering in step 1 and the sintering time 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 specific surface area, the calculation method is: A = m / S, m is the ratio of mass g, S is the surface area after the raw material powder is mixed, T is sintering time h.

[0018] The method of the multi-gradient sintering is specifically:

[0019] First, the weighed powder raw material is heated between 270 DEG C-300 DEG C, and kept warm for 1h-1.75h to remove excess moisture and promote the decomposition of KHCO3; then, the temperature is raised to 500 DEG C-530 DEG C, and kept warm for 1h-1.75h to completely decompose KHCO3 and maximize the activation of the powder pre-sintering activity; finally, the temperature is raised to 840 DEG C-860 DEG C, and sintered for 3h-6h to produce 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 sintered at 680 DEG C-700 DEG C for 3h-6h to obtain the final potassium niobate powder.

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

[0023] Compared with the prior art, the present application has the following advantages:

[0024] (1) The present application uses potassium bicarbonate instead of potassium carbonate for solid phase synthesis reaction. Potassium bicarbonate, which is not sensitive to air, is used as raw material to replace potassium carbonate which is easily hygroscopic in air, so that the volatilization of K element can be better controlled, the problem of deviation of the prepared potassium niobate powder from the ratio caused by the hygroscopic property of potassium carbonate can be solved, and the accuracy of preparation is improved.

[0025] (2) The present application completes the drainage and potassium bicarbonate conversion process in the low temperature zone (270-300 DEG C) through multi-gradient sintering; completes the activation process of the powder in the medium temperature zone (500-530 DEG C) to provide the most active powder for the next synthesis reaction; and rapidly sinters in the high temperature zone (840-860 DEG C); through the second sintering: the powder is first ball milled and dried, and then sintered at 680 DEG C-700 DEG C for the second time to further improve the activity and phase formation of the potassium niobate powder, which is simple and efficient.

[0026] (3) The present application controls the temperature and time of K element volatilization by selecting the holding time of the pre-sintered powder and the preparation amount of the powder, so as to avoid the deviation of the composition of potassium niobate caused by the indefinite pre-sintering holding time, and to achieve the powder process for accurately preparing potassium-containing oxide materials such as potassium niobate.

[0027] Compared with the current commonly used methods such as hydrothermal treatment, microwave sintering and electric field assisted sintering, the present application can optimize the composition 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 material, and is beneficial to improve the accuracy and efficiency of the solid phase method for preparing potassium-containing oxide powder material. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is the present application ratio quantitative chart.

[0029] Figure 2 is the present application multi-gradient sintering chart.

[0030] Figure 3 is the second sintering chart of the present application.

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

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

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

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

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

[0036] The present application will be further described in detail below in combination with the drawings and examples.

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

[0038] Step 1, the powder raw materials KHCO3, Nb2O5 required for preparing different quality of potassium niobate are weighed according to the molar ratio K: Nb = 2-2.02:1, the powder raw materials are taken symmetrically and subjected to multi-gradient sintering to prepare potassium niobate powder: first, the weighed powder raw materials m grams are heated at 270-300°C for 1-1.75h to remove excess moisture and promote the decomposition of KHCO3; then, the temperature is raised to 500-530°C for 1-1.75h to allow the complete decomposition of KHCO3 and maximize the activation of the powder pre-sintering activity; finally, the temperature is raised to 840-860°C for 3-6h to prepare potassium niobate powder; see Figure 1 、 Figure 2 .

[0039] Step 2, the potassium niobate powder prepared in Step 1 is subjected to secondary sintering to obtain the final potassium niobate powder: see Figure 3 .

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

[0041] The quantitative relationship between the mass of the powder raw materials and the sintering time 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 A = m / S, m is the mass of the powder raw materials g, S is the surface area of the mixed raw materials powder, 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, the powder raw materials KHCO3 and Nb2O5 for preparing 20g of potassium niobate are weighed according to the molar ratio KHCO3:Nb2O5 = 2:1, the powder raw materials are taken symmetrically and subjected to multi-gradient sintering to prepare potassium niobate powder: first, the weighed powder raw materials 20 grams are heated at 270°C for 1h to remove excess moisture and promote the decomposition of KHCO3; then, the temperature is raised to 500°C for 1h to allow the complete decomposition of KHCO3 and maximize the activation of the powder pre-sintering activity; finally, the temperature is raised to 840°C for 3h to prepare potassium niobate powder;

[0047] Step 2, the potassium niobate powder prepared in step 1 is subjected to second sintering to obtain final potassium niobate powder:

[0048] After the multi-gradient sintering is completed, the obtained potassium niobate powder is ball milled for 6 h at 400 rpm, then dried, and then sintered at 700℃ for 3 h to obtain 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, the potassium niobate powder prepared in step 1 is subjected to second sintering to obtain final potassium niobate powder:

[0052] Step 2, the potassium niobate powder prepared in step 1 is subjected to second sintering to obtain final potassium niobate powder:

[0053] After the multi-gradient sintering is completed, the obtained potassium niobate powder is ball milled for 6 h at 400 rpm, then dried, and then sintered at 700℃ for 3 h to obtain 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, the potassium niobate powder prepared in step 1 is subjected to second sintering to obtain final potassium niobate powder:

[0057] Step 2, the potassium niobate powder prepared in step 1 is subjected to second sintering to obtain final potassium niobate powder:

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

[0059] Example 4

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

[0061] Step 1,

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

[0063] Step 2, the potassium niobate powder prepared in step 1 is subjected to second sintering 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 h at 300 rpm, then dried, and then sintered at 680 ℃ for 6 h to obtain the final potassium niobate powder.

[0065] Analysis:

[0066] First, the specific fine preparation process, Figure 1 The relationship between the sintering time and the mass of the prepared potassium niobate is given. Figure 2 The specific process of multi-gradient sintering is given, Figure 2 In the process, (a) stage represents the low-temperature decomposition and conversion stage, at which the potassium bicarbonate decomposition and conversion and the drainage of the raw materials are completed. (b) stage represents the medium-temperature decomposition and activation stage, at which the activation process of the powder is mainly completed. (c) stage represents the high-temperature rapid synthesis stage, at which the phase formation process of the potassium niobate powder is mainly completed. (d) stage represents the natural cooling stage after the synthesis is completed. Figure 3 The main process of the second sintering is shown. After the prepared potassium niobate powder is ball milled and dried, the powder is subjected to second sintering to further improve the activity and phase formation of the potassium niobate powder. This is because for ceramic powder, the lower the pre-sintering temperature, the higher the activation degree.

[0067] Figures 4-7XRD phase structure patterns of 20g, 30g, 40g, 50g of potassium niobate respectively, it is not difficult to obtain that the potassium niobate materials of all configuration quality prepared by the fine process of the application have good phase formation effect, and are pure potassium niobate phase without appearing impurity phase (potassium deficiency phase, etc.). The main performance is that no other impurity peak appears in the figure, and the coincidence degree with the PDF card of potassium niobate is high.

[0068] Figure 8 For further semi-quantitative phase structure analysis of the XRD pattern of potassium niobate material, the figure proves that the powder material obtained by the above fine preparation process is a standard orthorhombic phase structure of potassium niobate. Figure 8 a is the phase structure of 20g of potassium niobate, it can be seen that the prepared powder contains three kinds of potassium niobate phases, respectively Cm2m (green, PDF #32-0822), Bmm2 (blue, PDF #71-2171), Amm2 (red, PDF #71-0946), the three phases are all orthorhombic phase structures, the difference is only the position orientation of the shortest axis of the unit cell, but they are all pure phase structures of potassium niobate. The content of the three phase structures is 99.9% (Cm2m), 0.1% (Amm2), and 0.0% (Bmm2), respectively, which proves that the powder synthesized by the preparation method of the application is mainly Cm2m orthorhombic phase structure of potassium niobate material, containing a trace amount of Amm2 orthorhombic phase, and Bmm2 orthorhombic phase structure basically does not exist and can be ignored. This further illustrates that the potassium niobate synthesized by this method does not exist impurity phase (potassium deficiency phase, etc.), and the preparation of pure orthorhombic phase potassium niobate ceramic powder can be relatively simple. Figure 8 b, c, d are the phase structures of 30g, 40g, 50g of potassium niobate respectively, and the powder structure prepared by them is consistent with Figure 8 the conclusion in a, that is, the obtained potassium niobate powder is mainly Cm2m orthorhombic phase structure of potassium niobate, and the content is more than 99.9%, while the content of Amm2 and Bmm2 orthorhombic phase structure of potassium niobate is less than 0.1%, which can be considered as high-purity potassium niobate phase in chemical composition. (It should be noted that Figure 8 The E value in the figure represents the target value of the fine fitting, and the R value represents the actual value. In the analysis process, the closer the R value is to the E value, the higher the reliability is. Generally, the result is reliable when the error of the R value is within 10%. Figure 8 All error values in the figure are less than 10%, and the result is reliable.

[0069] In summary, the fine solid phase sintering process adopted in the application effectively inhibits the volatilization of potassium, and can simply and efficiently prepare the potassium niobate material with high purity phase. The application makes up for the defects of the existing solid phase sintering technology, avoids the inherent defects of the synthesis technology such as the hydrothermal method and the sol-gel method, can realize the low-cost, rapid and efficient synthesis of ceramic powder material, greatly improves the experimental technical process, and optimizes the existing solid phase sintering technology. The application is a reliable and feasible preparation method of the potassium niobate ceramic powder.

Claims

1. A fine solid phase sintering method of a potassium niobate ceramic powder for suppressing potassium volatilization, characterized by, The specific steps are as follows: Step 1, according to the molar ratio KHCO3:Nb2O5=2-2.02:1, the mass of the prepared different mass of potassium niobate powder required by the powder raw material KHCO3 and Nb2O5 is weighed, and the powder raw material is subjected to multi-gradient sintering to preliminarily prepare the potassium niobate powder; The method of multi-gradient sintering is specifically as follows: First, the weighed powder raw material is heated between 270-300 DEG C, and kept for 1-1.75 h to remove excess moisture and promote the decomposition of KHCO3; then, the temperature is raised to 500-530 DEG C, and kept for 1-1.75 h to completely decompose KHCO3 and maximize the activation of the powder pre-sintering activity; finally, the temperature is raised to 840-860 DEG C, and sintered for 3-6 h to prepare the potassium niobate powder; Step 2, the potassium niobate powder prepared in step 1 is subjected to second sintering to obtain the final active potassium niobate powder; The specific method of the second sintering is as follows: After multi-gradient sintering, the obtained potassium niobate powder is ball milled for 4-6 h at 300-400 rpm; then dried, and then sintered at 680-700 DEG C for 3-6 h to obtain the final potassium niobate powder.

2. The fine solid phase sintering method of the potassium niobate ceramic powder for suppressing the volatilization of potassium according to claim 1, characterized by, The quantitative relationship between the mass of the powder raw material and the sintering time in step 1 of multi-gradient sintering 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 mixed raw material powder, and T is the sintering time h.

3. The fine solid phase sintering method of the potassium niobate ceramic powder for suppressing the volatilization of potassium according to claim 1, characterized by, The specific steps are as follows: Step 1, according to the molar ratio KHCO3:Nb2O5=2:1, the mass of the prepared different mass of potassium niobate powder required by the powder raw material KHCO3 and Nb2O5 is weighed, and the powder raw material is subjected to multi-gradient sintering to preliminarily prepare the potassium niobate powder: First, the weighed powder raw material 20 g is heated at 270 DEG C, and kept for 1 h to remove excess moisture and promote the decomposition of KHCO3; then, the temperature is raised to 500 DEG C, and kept for 1 h to completely decompose KHCO3 and maximize the activation of the powder pre-sintering activity; finally, the temperature is raised to 840 DEG C, and sintered for 3 h to prepare the potassium niobate powder; Step 2, the potassium niobate powder prepared in step 1 is subjected to second sintering to obtain the final active potassium niobate powder:

4. The fine solid phase sintering method of the potassium niobate ceramic powder for suppressing the evaporation of potassium according to claim 1, characterized by, After multi-gradient sintering, the obtained potassium niobate powder is ball milled for 6 h at 400 rpm; then dried, and then sintered at 700 DEG C for 3 h to obtain the final potassium niobate powder. The specific steps are as follows: Step 1, according to the molar ratio KHCO3:Nb2O5=2:1, the mass of the prepared different mass of potassium niobate powder required by the powder raw material KHCO3 and Nb2O5 is weighed, and the powder raw material is subjected to multi-gradient sintering to preliminarily prepare the potassium niobate powder: First, the weighed powder raw material 30 g is heated at 280 DEG C, and kept for 1.25 h to remove excess moisture and promote the decomposition of KHCO3; then, the temperature is raised to 510 DEG C, and kept for 1.25 h to completely decompose KHCO3 and maximize the activation of the powder pre-sintering activity; finally, the temperature is raised to 850 DEG C, and sintered for 4 h to prepare the potassium niobate powder; Step 2, the potassium niobate powder prepared in step 1 is subjected to second sintering to obtain final potassium niobate powder: After the multi-gradient sintering is completed, the obtained potassium niobate powder is ball milled for 5.5 h at 380 rpm, then dried, and then sintered at 690 ℃ for 4 h to obtain final potassium niobate powder.

5. The fine solid phase sintering method of the potassium niobate ceramic powder for suppressing the evaporation of potassium according to claim 1, characterized by, The specific steps are as follows: Step 1, 40 g of potassium niobate powder raw materials KHCO3 and Nb2O5 are prepared by weighing according to the molar ratio KHCO3:Nb2O5=2:1, and 40 g of the weighed powder raw materials is subjected to multi-gradient sintering to prepare potassium niobate powder: first, the weighed 40 g of powder raw materials is heated at 290 ℃ for 1.5 h to remove excess moisture and promote the decomposition of KHCO3; then, the temperature is raised to 520 ℃ for 1.5 h to completely decompose KHCO3 and maximize the activation of the powder pre-sintering activity; finally, the temperature is raised to 850 ℃ for sintering for 5 h to prepare potassium niobate powder; Step 2, the potassium niobate powder prepared in step 1 is subjected to second sintering to obtain final potassium niobate powder: After the multi-gradient sintering is completed, the obtained potassium niobate powder is ball milled for 5 h at 350 rpm, then dried, and then sintered at 690 ℃ for 5 h to obtain final potassium niobate powder.

6. The fine solid phase sintering method of the potassium niobate ceramic powder for suppressing the evaporation of potassium according to claim 1, characterized by, The specific steps are as follows: Step 1, 40 g of potassium niobate powder raw materials KHCO3 and Nb2O5 are prepared by weighing according to the molar ratio KHCO3:Nb2O5=2:1, and 40 g of the weighed powder raw materials is subjected to multi-gradient sintering to prepare potassium niobate powder: first, the weighed 40 g of powder raw materials is heated at 290 ℃ for 1.5 h to remove excess moisture and promote the decomposition of KHCO3; then, the temperature is raised to 520 ℃ for 1.5 h to completely decompose KHCO3 and maximize the activation of the powder pre-sintering activity; finally, the temperature is raised to 850 ℃ for sintering for 5 h to prepare potassium niobate powder; Step 2, the potassium niobate powder prepared in step 1 is subjected to second sintering to obtain final potassium niobate powder: After the multi-gradient sintering is completed, the obtained potassium niobate powder is ball milled for 5.5 h at 380 rpm, then dried, and then sintered at 690 ℃ for 4 h to obtain final potassium niobate powder. The specific steps are as follows: Step 1, 40 g of potassium niobate powder raw materials KHCO3 and Nb2O5 are prepared by weighing according to the molar ratio KHCO3:Nb2O5=2:1, and 40 g of the weighed powder raw materials is subjected to multi-gradient sintering to prepare potassium niobate powder: first, the weighed 40 g of powder raw materials is heated at 290 ℃ for 1.5 h to remove excess moisture and promote the decomposition of KHCO3; then, the temperature is raised to 520 ℃ for 1.5 h to completely decompose KHCO3 and maximize the activation of the powder pre-sintering activity; finally, the temperature is raised to 850 ℃ for sintering for 5 h to prepare potassium niobate powder;

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