Method for preparing tantalum nitride by calcium-assisted urea molten salt method

Abstract

The invention belongs to the technical field of preparation of inorganic functional materials, and particularly relates to a method for preparing tantalum nitride through a calcium-assisted urea molten salt method. The preparation method comprises the following steps: mixing a tantalum source, urea and soluble calcium salt to obtain a precursor mixture; grinding and mixing the precursor mixture and fused salt to obtain a mixed material; and carrying out heat treatment on the mixed material in an inert gas atmosphere to obtain tantalum nitride. According to the method provided by the invention, the tantalum nitride material with high crystallinity and regular morphology can be effectively prepared by assisting urea with calcium and combining a molten salt method. The problems of low efficiency and harsh reaction conditions of a traditional ammonia gas nitriding method are solved; meanwhile, the possible problems of impure phase, difficulty in accurate regulation and control of morphology and easiness in sintering of particles at high temperature in a solid nitrogen source nitriding method are solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of inorganic functional material preparation, and particularly relates to a method for preparing tantalum nitride by calcium-assisted urea molten salt method. BACKGROUND

[0002] Tantalum nitride (Ta3N5) is a typical n-type semiconductor photocatalytic material, which has a band gap width of about 2.1 eV and can effectively absorb visible light. It is considered to be one of the most potential materials for realizing high-efficiency solar photocatalytic decomposition of water to produce hydrogen. In addition, Ta3N5 has a wide application prospect in the fields of photoelectrochemical cells, environmental pollutant degradation, and functional coating in electronic devices due to its excellent chemical stability and suitable energy band position.

[0003] At present, the common preparation method of Ta3N5 is ammonia nitriding method, that is, using ammonia gas to nitride tantalum oxide (Ta2O5) at high temperature for a long time. However, this classical method has the following disadvantages: a) slow reaction kinetics, long single nitriding time (> 10 h) and incomplete nitriding, resulting in unreacted oxides or intermediate phases (such as TaON) in the product; b) harsh reaction conditions, which require strict control of a series of process conditions such as gas flow rate, nitriding temperature and holding time; c) low phase purity of the product, which is prone to produce various impurities (such as TaON, Ta2N, TaN, etc.), seriously affecting the purity and performance of the product.

[0004] In order to overcome the defects of the traditional ammonia nitriding method, many researchers have developed new processes using solid nitrogen sources (such as ammonium chloride, urea, melamine, ammonium bicarbonate and ammonium sulfate) to replace ammonia gas. For example, a method for preparing tantalum oxynitride (TaON) and / or tantalum nitride (Ta3N5) nano-photocatalyst is developed in the prior art, which uses a solid nitrogen source to replace ammonia gas, reduces the temperature of traditional ammonia nitriding and shortens the nitriding time, and has mild experimental conditions and simple operation. However, the solid nitrogen source nitriding method has limited ability to control the phase and morphology of the product, and has the problems of impure phase and difficult accurate control of morphology; and it is still difficult to completely avoid local sintering and agglomeration of particles at high temperature. x N y SUMMARY

[0005] The purpose of the present application is to provide a method for preparing tantalum nitride by calcium-assisted urea molten salt method, which can controllably, safely and efficiently prepare Ta3N5 material with high purity and controllable morphology (i.e. fineness).

[0006] In order to achieve the above purpose, the present application provides the following technical scheme: The present application provides a method for preparing tantalum nitride by calcium-assisted urea molten salt method, comprising the following steps: ​(1) mixing a tantalum source, urea and a soluble calcium salt to obtain a precursor mixture, wherein the tantalum source comprises one or more of tantalum oxide, tantalum hydroxide and a tantalum salt; (2) grinding and mixing the precursor mixture and a molten salt to obtain a mixture; (3) performing heat treatment on the mixture in an inert gas atmosphere to obtain the tantalum nitride.

[0007] Preferably, the tantalum salt comprises tantalum chloride and / or tantalum ethoxide; the purity of the tantalum source is ≥ 99.9%; the soluble calcium salt comprises one or more of calcium chloride, calcium nitrate and calcium acetate; the molar ratio of the tantalum source to urea is 1: (5-30); and the molar ratio of urea to the soluble calcium salt is (5-30): (1-10).

[0008] Preferably, in step (1), when the tantalum source comprises tantalum hydroxide and / or a tantalum salt, the mixing comprises the following steps: dissolving the tantalum source, urea and a soluble calcium salt in a solvent to obtain a mixed solution, wherein the solvent comprises water and / or an alcohol solvent; and removing the solvent from the mixed solution to obtain the precursor mixture; and the temperature for removing the solvent is 80-120°C.

[0009] Preferably, in step (1), when the tantalum source is tantalum oxide, the mixing comprises the following steps: dissolving the urea and a soluble calcium salt in a solvent to obtain a mixed solution, wherein the solvent comprises water and / or an alcohol solvent; removing the solvent from the mixed solution to obtain a urea-calcium gel precursor, wherein the temperature for removing the solvent is 80-120°C; and grinding and mixing the urea-calcium gel precursor and the tantalum source to obtain the precursor mixture.

[0010] Preferably, the molten salt comprises one or more of LiCl, NaCl, KCl, NaF, KF, Na2SO4, K2SO4, NaNO3 and KNO3; and the mass ratio of the molten salt to the tantalum source is (5-20): 1.

[0011] Preferably, the heat treatment comprises sequentially performing first-stage calcination and second-stage calcination; the holding temperature for the first-stage calcination is 300-500°C, the holding time is 1-2 h, the heating rate from room temperature to the holding temperature for the first-stage calcination is 1-8°C / min; the holding temperature for the second-stage calcination is 500-900°C, the holding time is 1-10 h, and the heating rate from the holding temperature for the first-stage calcination to the holding temperature for the second-stage calcination is 1-8°C / min; the inert gas comprises argon and / or nitrogen; and the flow rate of the inert gas is 50-200 mL / min.

[0012] Preferably, the heat treatment is followed by cooling, and the reaction product is directly obtained after the cooling; the reaction product is sequentially subjected to acid pickling, water washing and drying to obtain the tantalum nitride.

[0013] Preferably, the acid pickling uses a dilute acid solution with a molar concentration of 0.1-3 mol / L; the drying is vacuum drying, and the temperature of the vacuum drying is 70-150℃.

[0014] Preferably, the purity of the tantalum nitride is ≥99.9%.

[0015] Preferably, the Fisher particle size of the tantalum nitride is ≤1.0 μm.

[0016] The present application provides a method for preparing tantalum nitride by calcium-assisted urea molten salt method, comprising the following steps: (1) mixing a tantalum source, urea and a soluble calcium salt to obtain a precursor mixture, wherein the tantalum source comprises one or more of a tantalum oxide, a tantalum hydroxide and a tantalum salt; (2) grinding and mixing the precursor mixture and a molten salt to obtain a mixture; and (3) performing heat treatment on the mixture in an inert gas atmosphere to obtain tantalum nitride. The method provided by the present application delays the rapid decomposition of urea at low temperature by introducing a soluble calcium salt to complex with urea, so that the nitriding process during heat treatment is more controllable, and the generation of impurities such as TaON, Ta2N and TaN is effectively inhibited, and the purity of the tantalum nitride product is significantly improved. At the same time, the present application introduces a molten salt to provide a liquid phase environment, accelerates mass transfer, reduces the reaction temperature during heat treatment, and shortens the reaction time; the molten salt medium effectively prevents the contact and sintering of particles at high temperature, and can prepare Ta3N5 crystals with uniform size and regular morphology. In summary, the method provided by the present application can effectively prepare tantalum nitride materials with high crystallinity and regular morphology by calcium-assisted urea combined with a molten salt method. The problems of low efficiency and harsh reaction conditions of the traditional ammonia nitriding method are overcome; and the problems of impure phase, difficult to accurately control the morphology and easy to sinter particles at high temperature in the solid nitrogen source nitriding method are solved. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 FIG. 1 is an X-ray diffraction (XRD) pattern of the tantalum nitride material prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0018] The present application provides a method for preparing tantalum nitride by calcium-assisted urea molten salt method, comprising the following steps: (1) mixing a tantalum source, urea and a soluble calcium salt to obtain a precursor mixture, wherein the tantalum source comprises one or more of a tantalum oxide, a tantalum hydroxide and a tantalum salt; (2) grinding and mixing the precursor mixture and a molten salt to obtain a mixture; (3) heat treating the mixture in an inert gas atmosphere to obtain the tantalum nitride.

[0019] In the present application, all the raw materials / components are commercially available products well known to those skilled in the art, unless otherwise specified.

[0020] In the present application, the tantalum source includes one or more of tantalum oxide, tantalum hydroxide and tantalum salt.

[0021] In the present application, the tantalum salt preferably includes tantalum chloride and / or tantalum ethoxide. The purity of the tantalum source is preferably ≥ 99.9%. The soluble calcium salt is a calcium salt that can be dissolved in water or an organic solvent, preferably an alcohol solvent, specifically ethanol. The soluble calcium salt preferably includes one or more of calcium chloride, calcium nitrate and calcium acetate.

[0022] In the present application, the molar ratio of the tantalum source to urea is preferably 1:(5-30), more preferably 1:(8-26), and in the embodiments can be 1:10, 1:20 or 1:24. The molar ratio of the urea to the soluble calcium salt is preferably (5-30):(1-10), more preferably (5-25):(2-9), and in the embodiments can be 5:3, 10:4, 20:7 or 24:9.

[0023] In the present application, when the tantalum source includes tantalum hydroxide and / or tantalum salt, the mixing of the tantalum source, urea and soluble calcium salt preferably includes the following steps: dissolving the tantalum source, urea and soluble calcium salt in a solvent to obtain a mixed solution. The solvent preferably includes water and / or an alcohol solvent. The water can be deionized water. The alcohol solvent can be ethanol. The mixed solution is desolvated to obtain the precursor mixture. The desolvation method is preferably heating evaporation. The desolvation temperature is preferably 80-120°C. The precursor mixture is a dry, molecularly uniformly mixed “tantalum-urea-calcium” gel precursor mixture.

[0024] In the present application, when the tantalum source is tantalum oxide, the mixing of the tantalum source, urea and soluble calcium salt includes the following steps: dissolving the urea and soluble calcium salt in a solvent to obtain a mixed solution, the solvent including water and / or an alcohol solvent. The water can be deionized water. The alcohol solvent can be ethanol. The mixed solution is desolvated to obtain a urea-calcium gel precursor. The desolvation method is preferably heating evaporation. The desolvation temperature is preferably 80-120°C. The urea-calcium gel precursor is a dry, molecularly uniformly mixed “urea-calcium” gel precursor. The urea-calcium gel precursor and the tantalum source are ground and mixed to obtain the precursor mixture. The present application does not have special requirements for the specific implementation of the grinding and mixing.

[0025] After obtaining the precursor mixture, the present application grinds and mixes the precursor mixture and the molten salt to obtain a mixture.

[0026] In the present application, the molten salt preferably comprises one or more of LiCl, NaCl, KCl, NaF, KF, Na2SO4, K2SO4, NaNO3, and KNO3, and in embodiments can be one or two of LiCl, NaCl, KCl, NaF, KF, Na2SO4, K2SO4, NaNO3, and KNO3, and in particular can be KCl, NaCl, KNO3, and KCl, Na2SO4, and KF. When the molten salt is two of the above substances, the mass ratio of any molten salt is preferably (1-3):(1-3), and in embodiments can be 1:1 or 2:3. In the present application, the mass ratio of the molten salt to the tantalum source is preferably (5-20):1, and more preferably (5-15):1, and in embodiments can be 6:1, 8:1, 10:1.

[0027] After obtaining the mixture, the present application performs heat treatment on the mixture in an inert gas atmosphere to obtain tantalum nitride.

[0028] In the present application, the heat treatment is preferably performed in a tube furnace. The inert gas preferably comprises argon and / or nitrogen. The flow rate of the inert gas is preferably 50-200 mL / min, and more preferably 50-180 mL / min, and in embodiments can be 90 mL / min, 50 mL / min, 80 mL / min, or 150 mL / min.

[0029] In the present application, the heat treatment preferably comprises sequentially performing first-stage calcination and second-stage calcination. The holding temperature of the first-stage calcination is preferably 300-500°C, and in embodiments can be 380°C, 400°C, 300°C, or 450°C. The holding time of the first-stage calcination is 1-2 h, and in embodiments can be 1 h or 1.5 h. The heating rate from room temperature to the holding temperature of the first-stage calcination is 1-8°C / min, and in embodiments can be 3°C / min, 5°C / min, 4°C / min, or 7°C / min. The holding temperature of the second-stage calcination is preferably 500-900°C, and in embodiments can be 780°C, 800°C, 750°C, or 850°C. The holding time of the second-stage calcination is preferably 1-10 h, and in embodiments can be 7 h, 8 h, 6 h, or 5 h. The heating rate from the holding temperature of the first-stage calcination to the holding temperature of the second-stage calcination is preferably 1-8°C / min, and in embodiments can be 5°C / min, 6°C / min, or 3°C / min.

[0030] In the present application, the heat treatment is followed by cooling, and the reaction product is obtained directly after the cooling. The present application preferably further comprises sequentially subjecting the reaction product to acid pickling, water washing, and drying to obtain the tantalum nitride. In the present application, the acid pickling preferably uses a dilute acid solution. The dilute acid solution can be nitric acid or hydrochloric acid. The molar concentration of the dilute acid solution is preferably 0.1-3 mol / L, and in the embodiments can be 0.6 mol / L, 0.2 mol / L, 1.2 mol / L, or 1.5 mol / L. The present application preferably removes molten salt and soluble calcium salt in the reaction product by the acid pickling. The water washing preferably uses deionized water. The water washing is to neutral. The drying is preferably vacuum drying, and the temperature of the vacuum drying is preferably 70-150°C, and in the embodiments can be 110°C, 100°C, 105°C, or 90°C.

[0031] In the present application, the purity of the tantalum nitride is ≥99.9%, and in the embodiments can be 99.92%, 99.96%, 99.95%, or 99.90%.

[0032] In the present application, the Fisher particle size of the tantalum nitride is ≤1.0 μm, and in the embodiments can be 0.92 μm, 1.0 μm, or 0.94 μm.

[0033] In order to further illustrate the present application, the technical solutions provided by the present application are described in detail below in conjunction with the embodiments, but they should not be understood as limiting the scope of protection of the present application.

[0034] Embodiment 1 (1) In deionized water, urea and calcium chloride with a molar ratio of 5:3 are added, and stirred to form a uniform and clear solution.

[0035] (2) The solution obtained in step (1) is heated and evaporated at 90°C to remove the solvent, and a dry, molecularly uniform mixed “urea-calcium” gel precursor is formed.

[0036] (3) The “urea-calcium” gel precursor obtained in step (2) is ground and mixed with tantalum oxide to obtain a precursor mixture. The molar ratio of tantalum oxide to urea is 1:10.

[0037] (4) The precursor mixture obtained in step (3) is thoroughly ground and mixed with KCl to obtain a mixture. The mass ratio of KCl to tantalum oxide is 6:1.

[0038] (5) The mixture obtained in step (4) is placed in a tube furnace, and subjected to staged calcination under an argon atmosphere. The argon flow rate is 90 mL / min, the temperature is programmed to rise from room temperature to 380°C at a rate of 3°C / min, and then held for 1 h, and then programmed to rise to 780°C at a rate of 5°C / min, and held for 7 h to complete the nitriding reaction and crystal growth.

[0039] (6) After the heat treatment is completed, the reaction product obtained in step (5) is naturally cooled to room temperature, the reaction product is first washed with 0.6 mol / L nitric acid to remove the fused salt and calcium salt, then washed with deionized water until neutral, and finally dried in a vacuum drying oven at 110°C to obtain a high-purity Ta3N5 powder.

[0040] The phase of the Ta3N5 powder obtained in the embodiment is single Ta3N5, Figure 1 The X-ray diffraction (XRD) diagram of the prepared Ta3N5 powder of Example 1 is shown in Figure 1. Figure 1 It can be seen that the Ta3N5 powder prepared in the embodiment has no impurity phase; the purity of Ta3N5 is 99.92%, and the Fisher particle size is 0.92 μm.

[0041] Example 2 (1) In deionized water, add molar ratio of 1:10:4 of tantalum chloride, urea and calcium chloride, and stir to form a uniform and clear solution.

[0042] (2) The solution obtained in step (1) is heated and evaporated at 90°C to remove the solvent, and a dry, molecularly uniform "tantalum-urea-calcium" gel precursor is formed.

[0043] (3) The "tantalum-urea-calcium" gel precursor obtained in step (2) is thoroughly ground and mixed with NaCl to obtain a mixture. The mass ratio of NaCl to tantalum chloride is 8:1.

[0044] (4) The mixture obtained in step (3) is placed in a tube furnace and subjected to staged calcination under an argon atmosphere. The argon flow rate is 50 mL / min, the temperature is programmed to rise to 400°C at a rate of 5°C / min, and the temperature is maintained for 1 h. Then the temperature is programmed to rise to 800°C at a rate of 5°C / min, and the temperature is maintained for 8 h to complete the nitriding reaction and crystal growth.

[0045] (5) After the heat treatment is completed, the reaction product obtained in step (4) is naturally cooled to room temperature, the reaction product is first washed with 0.2 mol / L hydrochloric acid to remove the fused salt and calcium salt, then washed with deionized water until neutral, and finally dried in a vacuum drying oven at 100°C to obtain a high-purity Ta3N5 powder.

[0046] The phase of the Ta3N5 powder obtained in the embodiment is single Ta3N5, and there is no impurity phase; the purity of Ta3N5 is 99.96%, and the Fisher particle size is 1.0 μm.

[0047] Example 3 (1) In deionized water, add molar ratio of 1:20:7 of tantalum ethoxide, urea and calcium nitrate, and stir to form a uniform and clear solution.

[0048] (2) The solution obtained in step (1) is heated and evaporated at 110°C to remove the solvent, forming a dry, molecularly uniformly mixed "tantalum-urea-calcium" gel precursor.

[0049] (3) The "tantalum-urea-calcium" gel precursor obtained in step (2) is thoroughly ground and mixed with KNO3 and KCl to obtain a mixture. The mass ratio of KNO3, KCl to tantalum ethoxide is 3:3:1.

[0050] (4) The mixture obtained in step (3) is placed in a tube furnace and subjected to staged calcination under a nitrogen atmosphere. The nitrogen flow is 80 mL / min, and the temperature is programmed to rise to 300°C at a rate of 4°C / min, and then held for 1.5 h. Subsequently, the temperature is programmed to rise to 750°C at a rate of 6°C / min, and held for 6 h to complete the nitridation reaction and crystal growth.

[0051] (5) After the heat treatment is completed, the reaction product obtained in step (4) is naturally cooled to room temperature. The reaction product is first washed with 1.2 mol / L nitric acid to remove the molten salt and calcium salt, and then washed with deionized water until neutral. Finally, it is dried in a vacuum drying oven at 105°C to obtain a high-purity Ta3N5 powder.

[0052] The phase of the Ta3N5 powder obtained in this example is single Ta3N5 without impurities. The purity of Ta3N5 is 99.95%, and the Fisher particle size is 0.94 μm.

[0053] Example 4 (1) In ethanol, tantalum hydroxide, urea and calcium acetate are added in a molar ratio of 1:24:9, and stirred to form a uniform clear solution.

[0054] (2) The solution obtained in step (1) is heated and evaporated at 90°C to remove the solvent, forming a dry, molecularly uniformly mixed "tantalum-urea-calcium" gel precursor.

[0055] (3) The "tantalum-urea-calcium" gel precursor obtained in step (2) is thoroughly ground and mixed with Na2SO4 and KF to obtain a mixture. The mass ratio of Na2SO4, KF to tantalum hydroxide is 4:6:1.

[0056] (4) The mixture obtained in step (3) is placed in a tube furnace and subjected to staged calcination under a nitrogen atmosphere. The nitrogen flow is 150 mL / min, and the temperature is programmed to rise to 450°C at a rate of 7°C / min, and then held for 1 h. Subsequently, the temperature is programmed to rise to 850°C at a rate of 3°C / min, and held for 5 h to complete the nitridation reaction and crystal growth.

[0057] (5) After the heat treatment, the reaction product obtained in step (4) is naturally cooled to room temperature, and the reaction product is first washed with 1.5 mol / L nitric acid to remove the molten salt and calcium salt, then washed with deionized water until neutral, and finally dried in a vacuum drying oven at 90°C to obtain a high-purity Ta3N5 powder.

[0058] The phase of the Ta3N5 powder obtained in this example is single Ta3N5 without impurity phase; the purity of Ta3N5 is 99.90%, and the Fisher particle size is 0.92 μm.

[0059] Comparative Example 1 (1) In deionized water, urea and calcium chloride with a molar ratio of 5:3 are added to form a uniform and clear solution.

[0060] (2) The solution obtained in step (1) is heated and evaporated at 90°C to remove the solvent and form a dry, molecularly uniform mixed "urea-calcium" gel precursor.

[0061] (3) The "urea-calcium" gel precursor obtained in step (2) is ground and mixed with tantalum oxide to obtain a precursor mixture. The molar ratio of tantalum oxide to urea is 1:10.

[0062] (4) The precursor mixture obtained in step (3) is placed in a tube furnace and subjected to staged calcination under an argon atmosphere. The argon flow rate is 90 mL / min, and the temperature is programmed to rise to 380°C at a rate of 3°C / min, and then to 780°C at a rate of 5°C / min, and the nitrogenization reaction and crystal growth are completed after 1 h and 7 h of holding, respectively.

[0063] (5) After the heat treatment, the reaction product obtained in step (4) is naturally cooled to room temperature, and the reaction product is first washed with 0.6 mol / L nitric acid to remove the calcium salt, then washed with deionized water until neutral, and finally dried in a vacuum drying oven at 110°C to obtain a powder product.

[0064] Compared with Example 1, the precursor mixture obtained in Comparative Example 1 is not added with molten salt for grinding and uniform heat treatment. The product obtained in this comparative example is a mixture of Ta3N5 and TaON, and the Fisher particle size is 1.36 μm. The reason is that without the addition of molten salt, the tantalum oxide cannot be completely nitrided to form Ta3N5 at the heat treatment temperature and holding time.

[0065] Comparative Example 2 (1) In deionized water, tantalum chloride and urea with a molar ratio of 1:10 are added to form a uniform and clear solution.

[0066] (2) The solution obtained in step (1) is heated and evaporated at 90°C to remove the solvent and form a dry, molecularly uniform mixed "tantalum-urea" gel precursor.

[0067] (3) The "tantalum-urea" gel precursor obtained in step (2) is thoroughly ground and mixed with NaCl to obtain a mixture. The mass ratio of NaCl to tantalum chloride is 8:1.

[0068] (4) The mixture obtained in step (3) is placed in a tube furnace and subjected to staged calcination under an argon atmosphere. The argon flow rate is 50 mL / min. The temperature is programmed to rise to 400°C at a rate of 5°C / min, and the temperature is kept constant for 1 h. Then the temperature is programmed to rise to 800°C at a rate of 5°C / min, and the temperature is kept constant for 8 h to complete the nitriding reaction and crystal growth.

[0069] (5) After the heat treatment is completed, the reaction product obtained in step (4) is naturally cooled to room temperature. The reaction product is first washed with 0.2 mol / L hydrochloric acid to remove the molten salt, then washed with deionized water until neutral, and finally dried in a vacuum drying oven at 100°C to obtain a powder product.

[0070] Compared with Example 2, Comparative Example 2 does not add calcium salt in the preparation process of the precursor solution. The product obtained in this comparative example is a mixture of Ta3N5 and TaCl5, and the Fisher particle size is 1.16 μm.

[0071] From the above examples, it can be seen that the method provided by the present application delays the rapid decomposition of urea at low temperature by introducing calcium salt and urea complex, so that the nitriding process is more controllable, and the generation of TaON, Ta2N, TaN and other impurities is effectively inhibited. The product purity is significantly higher than that of the traditional method; by introducing molten salt to provide a liquid phase environment, mass transfer is accelerated, the reaction temperature is reduced, and the reaction time is shortened; the molten salt medium effectively blocks the contact and sintering of particles at high temperature, and can prepare Ta3N5 crystals with uniform size and regular morphology.

[0072] Although the above examples have made a detailed description of the present application, it is only a part of the embodiments of the present application, not all the embodiments, and other embodiments can be obtained under the premise of no creativity according to the present embodiments, which all belong to the protection scope of the present application.

Claims

1. A method for the calcium-assisted production of tantalum nitride by the urea molten salt method, characterized in that, The method comprises the following steps: (1) mixing a tantalum source, urea and a soluble calcium salt to obtain a precursor mixture, wherein the tantalum source comprises one or more of tantalum oxide, tantalum hydroxide and a tantalum salt; (2) grinding and mixing the precursor mixture and a molten salt to obtain a mixture; (3) performing heat treatment on the mixture in an inert gas atmosphere to obtain the tantalum nitride.

2. The method of claim 1, wherein, The tantalum salt comprises tantalum chloride and / or tantalum ethoxide; the purity of the tantalum source is greater than or equal to 99.9%; the soluble calcium salt comprises one or more of calcium chloride, calcium nitrate and calcium acetate; the molar ratio of the tantalum source to urea is 1:(5-30); and the molar ratio of urea to the soluble calcium salt is (5-30):(1-10).

3. The method according to claim 1 or 2, characterized in that, In step (1), when the tantalum source comprises tantalum hydroxide and / or a tantalum salt, the mixing comprises the following steps: dissolving the tantalum source, urea and a soluble calcium salt in a solvent to obtain a mixed solution, wherein the solvent comprises water and / or an alcohol solvent; and removing the solvent from the mixed solution to obtain the precursor mixture; and the temperature for removing the solvent is 80-120 DEG C.

4. The method according to claim 1 or 2, characterized in that, In step (1), when the tantalum source is tantalum oxide, the mixing comprises the following steps: dissolving the urea and a soluble calcium salt in a solvent to obtain a mixed solution, wherein the solvent comprises water and / or an alcohol solvent; removing the solvent from the mixed solution to obtain a urea-calcium gel precursor, wherein the temperature for removing the solvent is 80-120 DEG C; and grinding and mixing the urea-calcium gel precursor and the tantalum source to obtain the precursor mixture.

5. The method of claim 1, wherein, The molten salt comprises one or more of LiCl, NaCl, KCl, NaF, KF, Na2SO4, K2SO4, NaNO3 and KNO3; and the mass ratio of the molten salt to the tantalum source is (5-20):

1.

6. The method of claim 1, wherein, The heat treatment comprises sequentially performing first-stage calcination and second-stage calcination; the holding temperature of the first-stage calcination is 300-500 DEG C, the holding time is 1-2 h, the temperature rising rate from room temperature to the holding temperature of the first-stage calcination is 1-8 DEG C / min, the holding temperature of the second-stage calcination is 500-900 DEG C, the holding time is 1-10 h, and the temperature rising rate from the holding temperature of the first-stage calcination to the holding temperature of the second-stage calcination is 1-8 DEG C / min; the inert gas comprises argon and / or nitrogen; and the flow rate of the inert gas is 50-200 mL / min.

7. The method of claim 1, wherein, The heat treatment is followed by cooling, and the reaction product is directly obtained after the cooling; the reaction product is sequentially subjected to acid pickling, water washing and drying to obtain the tantalum nitride.

8. The method of claim 7, wherein, The acid pickling uses a dilute acid solution, the molar concentration of the dilute acid solution is 0.1-3 mol / L, and the drying is vacuum drying, and the temperature of the vacuum drying is 70-150 DEG C.

9. The method according to claim 7 or 8, characterized in that, The purity of the tantalum nitride is greater than or equal to 99.9%.

10. The method according to claim 7 or 8, characterized in that, The Fisher particle size of the tantalum nitride is less than or equal to 1.0 μm.

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