Reductive-coprecipitation preparation method and application of (NH4)2MnF6

Abstract

The present invention belongs to the technical field of fluorescent materials, and discloses a reduction-coprecipitation preparation method and application of (NH4)2MnF6. KMnO4 and NH4HF2 / NH4F are added to hydrofluoric acid to obtain system A; the H2O2 solution is added to system A in the following manner (i) or (ii) to obtain system B; manner (i): the H2O2 solution is added every 3 minutes, and 20-30 μL is added each time; manner (ii): the H2O2 solution is added every 1 minute first, and 0.2-0.5 mL is added each time, and the total addition amount is 1-1.5 mL; after stirring for 20-30 minutes, the addition of the H2O2 solution is changed to every 3 minutes, and 20-30 μL is added each time; after the system B is subjected to solid-liquid separation, the precipitate obtained from the solid-liquid separation is collected, washed and dried to obtain the target product. The present invention adopts the reduction-coprecipitation method, which has low requirements for equipment and synthesis conditions and a relatively simple process; using (NH4)2MnF6 as a manganese source for Mn 4+ When synthesizing the activated fluoride fluorescent crystal, the amount of hydrofluoric acid required to dissolve it is greatly reduced, which is beneficial to improving the yield of the fluorescent crystal.

Description

Technical Field

[0001] The present invention belongs to the technical field of fluorescent materials, and particularly relates to a reduction-coprecipitation preparation method and application of (NH4)2MnF6. Background Art

[0002] Mn 4+ Mn-doped fluoride red fluorescent phosphors have the characteristics of broadband absorption in the blue region, narrowband emission in the red region, high color purity, and relatively simple synthesis process, and have important applications in the field of white light emitting diodes (WLEDs) for liquid crystal display backlights. Since K2SiF6:Mn 4+ has been commercially applied, the research on Mn 4+ -doped red fluorescent materials has received extensive attention and research in the industry. Selecting an appropriate preparation method and manganese-containing compound as the manganese source is the key to preparing highly efficient Mn 4+ -doped fluorescent materials. Manganese-containing compounds such as K2MnF6, KMnO4, Mn(HPO4)2, MnCO3, MnO2, MnO, Mn(NO3)2, or Mn(CH3COO)2 have all been reported to be used as the manganese source for preparing Mn 4+ -doped fluorescent materials with different matrices (Wang Zhaowu, Qu Qiao, Ji Haipeng, Hao Xiaofei, Li Jinsheng. Mn 4+ -activated phosphors available manganese sources and preparation methods. Chinese Journal of Luminescence, 2022, 43(5): 662-675.). Specifically, for Mn 4+ -doped fluoride-based fluorescent materials, K2MnF6 and KMnO4 are the most commonly used manganese sources; in the early stage, KMnO4 was mainly used as the manganese source, but Mn 7+ is prone to appear Mn 4+ and Mn 3+ equivalent states during the process of being reduced to the required Mn 2+ valence state ions. In later research reports, K2MnF6 is generally first synthesized and then used as the manganese source to prepare Mn 4+ -doped fluoride fluorescent materials.

[0003] Mn 4+ -activated fluoride phosphors have the advantages of emitting short-wave red light and generally relatively high quantum efficiency, but their moisture resistance is relatively poor, and the fluorescence performance is prone to deterioration in a humid and hot environment. Related research in recent years has shown that Mn 4+ -doped fluoride bulk fluorescent crystal materials show significantly improved moisture resistance compared to the traditional micron polycrystalline powder materials of the same composition due to their smaller specific surface area and lower surface defect concentration; at the same time, the quantum efficiency is further improved, and full inorganic encapsulation can be achieved.

[0004] Growth Mn 4+ Fluoride-doped fluorescent crystals and preparation of Mn 4+ Fluoride-doped phosphors require different chemical processes. In order to grow high-quality Mn 4+ To prepare fluorescent crystals doped with fluoride, the matrix compound and manganese source are generally dissolved in a hydrofluoric acid solution to prepare a corresponding saturated or nearly saturated solution. Then, evaporation crystallization, cooling crystallization, etc. are used to make the solute supersaturated and precipitate crystal nuclei and gradually grow. 4+ The manganese source K2MnF6 commonly used in doping fluoride phosphor materials has a relatively low solubility in hydrofluoric acid solution. When preparing the initial saturated or nearly saturated solution, a large amount of hydrofluoric acid solution is required to dissolve K2MnF6, resulting in a relatively small yield of the target fluorescent crystal obtained after a certain crystallization process, and the introduction of potassium ions is often unavoidable in the process of growing fluorescent crystals of fluoride components without potassium ions. (NH4)2MnF6 can also be used to prepare Mn 4+ Doping fluorescent materials provides tetravalent manganese ions, and as an ammonium salt, it has relatively large solubility and is relatively difficult to introduce impurity ions such as ammonium radicals during the growth of fluorescent crystals, which is expected to solve the above-mentioned problems when using K2MnF6 as a manganese source.

[0005] There are very few literature reports on the synthesis and preparation of (NH4)2MnF6 at present. Only one literature on the preparation by electrolytic oxidation has been retrieved (S. Kaskel, J. Strähle. ZUR STRUKTUR UND REAKTIVITAT DES DIAMMONIUMHEXAFLUOROMANGANATS(IV). Zeitschrift für anorganische und allgemeine Chemie, 1997, 623: 1259-1263.). The specific preparation process is as follows: Add 1 g of MnCO3 and 20 mL of HF acid (40 wt%) solution into a platinum bowl. The platinum shell is used as the anode, and a platinum sheet immersed in the suspension from above is used as the cathode. After electrolysis for 10 minutes (2 V / 0.5 A), a dark red MnF3 solution is formed; then 7.5 g of NH4HF2 is added to the above solution, and electrolysis is continued (2 V / 0.5 A) for several hours until the solution becomes clear; at this time, N2 is introduced to accelerate drying, and yellow particles are obtained after about 24 h; the residual moisture and excess NH4HF2 in the above particles are removed by washing with ethanol and ether, and then dried in vacuo to finally obtain (NH4)2MnF6. The disadvantages of this synthesis method are that the reaction requires an electrolytic oxidation device with noble metal electrodes and the electrolytic oxidation process has a long cycle, which is not suitable for large-scale industrial production and small-scale laboratory use. Therefore, it is necessary to develop a new, efficient and relatively suitable preparation method for (NH4)2MnF6. Summary of the Invention

[0006] In order to solve the problems of high restrictions on electrolysis equipment and synthesis conditions, relatively complex and lengthy process operation flow when preparing (NH4)2MnF6 by the existing electrolytic oxidation method, one of the purposes of the present invention is to provide a reduction-coprecipitation preparation method for (NH4)2MnF6, and the second purpose is to provide an application of (NH4)2MnF6 as a manganese source for preparing Mn 4+ activated fluorescent materials, and solve the problems of the need for a large amount of hydrofluoric acid for dissolution and the introduction of impurity potassium ions when using K2MnF6 as the manganese source traditionally.

[0007] To achieve the above purposes, the technical solutions adopted by the present invention are as follows:

[0008] A reduction-coprecipitation preparation method for (NH4)2MnF6, the steps are as follows:

[0009] (1). Add KMnO4 and NH4HF2 / NH4F into hydrofluoric acid to obtain system A; wherein, the raw material dosage ratio is KMnO4∶NH4HF2 / NH4F∶hydrofluoric acid = 0.006 mol∶(0.35 - 0.45) mol∶(30 - 40) mL;

[0010] (2) Add the H₂O₂ solution to system A in the following manner (i) or (ii). The total addition amount of the H₂O₂ solution throughout the process is 2.5 - 3.0 mL to obtain system B.

[0011] Method (i): Add the H₂O₂ solution every 3 minutes, with each addition of 20 - 30 μL.

[0012] Method (ii): First, add the H₂O₂ solution every 1 minute, with each addition of 0.2 - 0.5 mL, and the total addition amount is 1 - 1.5 mL. After stirring for 20 - 30 minutes, change to adding the H₂O₂ solution every 3 minutes, with each addition of 20 - 30 μL until the remaining H₂O₂ solution is added completely.

[0013] (3) After the first solid-liquid separation of system B, collect the precipitate from the first solid-liquid separation, wash and dry it to obtain the target product.

[0014] The entire process of steps (1) - (2) is carried out under the conditions of an ice-water bath and stirring.

[0015] Further, in order to improve the purity of the target product and selectively remove one type of impurity, the following operation is preferably carried out: In step (3), collect the precipitate from the first solid-liquid separation, add acetic acid / hydrofluoric acid to this precipitate, carry out the second solid-liquid separation, collect the precipitate from the second solid-liquid separation, wash and dry it to obtain the target product. Acetic acid is mainly used to remove NH₄HF₂ / NH₄F or trace amounts of KHF₂ that may exist in the product, and hydrofluoric acid is mainly used to remove a small amount of (NH₄)₂MnF₅ that may exist in the product.

[0016] In the above preferred technical solution, it is further preferred that in step (3), 1 - 2 mL of acetic acid / hydrofluoric acid is added to every 0.5 g of the precipitate after the first solid-liquid separation.

[0017] Better still, the method of adding hydrofluoric acid and acetic acid step by step can also be used to remove multiple impurities in the target product simultaneously. The following operation is preferably carried out: In step (3), collect the precipitate after the first solid-liquid separation, first add hydrofluoric acid to this precipitate, carry out the second solid-liquid separation, collect the precipitate from the second solid-liquid separation, then add acetic acid to this precipitate, carry out the third solid-liquid separation, collect the precipitate from the third solid-liquid separation, wash and dry it to obtain the target product.

[0018] In the above preferred technical solution, it is further preferred that in step (3), 1 - 2 mL of hydrofluoric acid is added to every 0.5 g of the precipitate after the first solid-liquid separation, and 2 - 4 mL of acetic acid is added to every 0.5 g of the precipitate after the second solid-liquid separation.

[0019] Further, during washing, the detergent used is acetone, methanol or ethanol.

[0020] Further, during drying, vacuum drying or air drying is adopted. After drying, the obtained target product is stored in a desiccator or a vacuum environment.

[0021] Further, the concentration of all hydrofluoric acid involved is 10 - 48 wt%.

[0022] Further, all solid-liquid separations involved are centrifugal separations, with a centrifugal speed of 5000 - 10000 rpm and a centrifugal time of 2 - 5 min.

[0023] Further, the concentration of the H2O2 solution is 20 - 40 wt%.

[0024] An application of (NH4)2MnF6, used as a manganese source for preparing Mn 4+ activated fluorescent materials.

[0025] In the present invention, in a hydrofluoric acid solution containing KMnO4 and NH4HF2 or NH4F, an H2O2 solution is added to carry out a reduction reaction and a coprecipitation reaction to precipitate (NH4)2MnF6, and it is successfully used as a manganese source for Mn 4+ activated growth of fluoride fluorescent crystals. Among them, the reduction reaction refers to the formation of [MnF6] by the reduction of permanganate in a hydrofluoric acid solution by H2O2 2- groups, and the coprecipitation reaction refers to the bonding of the formed [MnF6] 2- groups with ammonium ion groups contained in the solution to form (NH4)2MnF6 precipitate.

[0026] Beneficial effects: The present invention prepares (NH4)2MnF6 by a reduction-coprecipitation reaction method, which has low requirements for equipment and synthesis conditions and a relatively simple operation process; (NH4)2MnF6 has high solubility. When (NH4)2MnF6 is used as a manganese source for Mn 4+ activated synthesis of fluoride fluorescent crystals, compared with the crystal synthesis using K2MnF6 as a manganese source, the amount of hydrofluoric acid required to dissolve (NH4)2MnF6 is greatly reduced, which is beneficial to improving the yield of fluorescent crystals and will not introduce impurity K + ions into the product crystals; the present invention successfully prepares the target product and avoids the precipitation of impurity phases in the product by optimizing the ratio of NH4HF2 / NH4F to KMnO4 in the raw materials, the usage amount of the hydrofluoric acid solvent, the addition method and addition amount of the reducing agent (H2O2), and the treatment method of the later precipitate. Description of the Drawings

[0027] Figure 1 X-ray diffraction pattern of the product prepared in Example 1 of the present invention.

[0028] Figure 2 Physical photograph of the product prepared in Example 2 of the present invention.

[0029] Figure 3 X-ray diffraction pattern of the product prepared in Example 2 of the present invention.

[0030] Figure 4 X-ray diffraction pattern of the sample obtained in Comparative Example 1 of the present invention.

[0031] Figure 5 Optical microscope picture of the fluorescent crystal material prepared in the Application Example of the present invention.

[0032] Figure 6 Photoluminescence spectrum of the fluorescent crystal material prepared in the Application Example of the present invention under 460 nm blue light excitation. Detailed implementation manners

[0033] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described below in conjunction with specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those skilled in the art based on the described embodiments without creative efforts fall within the protection scope of the present invention.

[0034] In the following examples, comparative examples, solubility experiments and application examples, the concentration of the HF solution is 40 wt%, and the concentration of the H2O2 solution is 30 wt%.

[0035] Example 1

[0036] Weigh 1 g of KMnO4 and 20 g of NH4HF2. Under an ice-water bath and with magnetic stirring, add them to a transparent centrifuge tube containing 30 mL of HF solution. After stirring for 30 min, let it stand, and a solid precipitate can be seen at the bottom. Continue magnetic stirring, and use a pipette with a range of 200 µL to add H2O2 solution every 3 min, adding 20 µL each time. The total addition amount of H2O2 solution throughout the process is 3 mL. After the last addition of H2O2 solution, wait for another 3 min and then stop stirring. Perform the first centrifugal solid-liquid separation at a centrifugal rate of 10,000 rpm, collect the yellow precipitate after the first centrifugal solid-liquid separation. Then, add 2 mL of acetic acid solution to every 0.5 g of the precipitate, and perform the second centrifugal solid-liquid separation at a centrifugal rate of 10,000 rpm. Use a pipette to suck out the supernatant (mainly to remove the undissolved NH4HF2 and the trace amount of KHF2 that may be produced during the reaction), collect the yellow precipitate after the second centrifugal solid-liquid separation and wash it three times with acetone. Finally, dry it in a vacuum drying oven at 70 °C for 24 h to obtain the product, and store it in a closed desiccator at room temperature.

[0037] The X-ray diffraction pattern of the product was tested using an X-ray diffractometer (Dandong Haoyuan Instrument Co., Ltd., Liaoning, China, model DX-2700BH), and the test results are as Figure 1 shown. Analysis shows that the main phase in the product is (NH4)2MnF6, but it also contains a small amount of (NH4)2MnF5; (NH4)2MnF6 is the expected phase, while (NH4)2MnF5 is an impurity phase containing Mn 3+ ions. The reason for the formation of a small amount of (NH4)2MnF5 may be that H2O2 reacts with (NH4)2MnF6, and Mn 4+ is reduced to Mn 3+ .

[0038] Example 2

[0039] Weigh 1 g of KMnO4 and 20 g of NH4HF2. Under an ice-water bath and magnetic stirring, add them to a transparent centrifuge tube containing 30 mL of HF solution. After stirring for 30 min, let it stand, and solid precipitation can be seen at the bottom. Continue magnetic stirring, and use a dropper with a volume of 2 mL to add H2O2 solution every 1 min, 0.5 mL each time, with a total addition amount of 1 mL. After stirring for 30 min, change to a pipette gun with a range of 200 µL, add H2O2 solution every 3 min, 20 µL each time, and the total addition amount of H2O2 solution throughout the process is 2.5 mL. After the last addition of H2O2 solution, wait for another 3 min and stop stirring. Perform the first centrifugal solid-liquid separation at a centrifugal rate of 10,000 rpm, collect the yellow precipitate after the first centrifugal solid-liquid separation, then add 2 mL of HF solution to every 0.5 g of the precipitate, and perform the second centrifugal solid-liquid separation at a centrifugal rate of 10,000 rpm. Use a pipette to suck off the supernatant (mainly to remove a small amount of (NH4)2MnF5 that may be generated), collect the yellow precipitate after the second centrifugal solid-liquid separation, then add 2 mL of acetic acid solution to every 0.5 g of the precipitate, and perform the third centrifugal solid-liquid separation at a centrifugal rate of 10,000 rpm. Use a pipette to suck off the supernatant (mainly to remove the undissolved NH4HF2 and trace amounts of KHF2 that may be generated during the reaction), collect the yellow precipitate after the third centrifugal solid-liquid separation and wash it three times with acetone. Finally, dry it in a vacuum drying oven at 70 °C for 24 h to obtain the product (the physical photo is as shown in Figure 2 ), and store it in a closed desiccator at room temperature.

[0040] Use an X-ray diffractometer to test the X-ray diffraction pattern of the product. The test results are as shown in Figure 3 . The analysis shows that the product is a single phase, namely (NH4)2MnF6. Comparing with Example 1, it can be seen that on the one hand, the impurity phase of (NH4)2MnF5 in the product is effectively removed, and on the other hand, by using the method of adding H2O2 quickly first and then slowly, the total synthesis time is greatly reduced.

[0041] Control Example 1

[0042] Weigh 1 g of KMnO4 and 20 g of NH4HF2, and add them to a transparent centrifuge tube containing 60 mL of HF solution in an ice-water bath under magnetic stirring. After stirring for 30 min, let it stand, and no undissolved solid substances are seen at the bottom. Continue stirring magnetically, and use a pipette with a range of 200 µL to add H2O2 solution every 3 min, adding 20 µL each time. The total addition amount of H2O2 solution throughout the process is 3 mL. After the last addition of H2O2 solution, wait for another 3 min and then stop stirring. However, at this time, no precipitate is formed in the solution, and the expected product is not obtained. Add 10 mL of acetone to this solution, and immediately a light pink flocculent substance precipitates. After standing, the supernatant is colorless and transparent. Centrifuge for solid-liquid separation at a centrifugation rate of 10000 rpm, collect the precipitate, dry it in a vacuum oven at 70 °C for 24 h, and then store it in a closed desiccator at room temperature.

[0043] The target product (NH4)2MnF6 was not obtained in this comparative example. This may be because the solubility of (NH4)2MnF6 in hydrofluoric acid solution is quite large. Therefore, when dissolving KMnO4 and NH4HF2 in a relatively large amount of hydrofluoric acid solution, the excess hydrofluoric acid will prevent the precipitation of the target product. The flocculent precipitate produced after adding acetone to the final solution obtained was tested for its X-ray diffraction pattern using an X-ray diffractometer, and the results are as Figure 4 shown. Analysis shows that the precipitate product is (NH4)2MnF5.

[0044] Comparative Example 2

[0045] Weigh 1 g of KMnO4 and 4 g of NH4HF2, and add them to a transparent centrifuge tube containing 30 mL of HF solution in an ice-water bath under magnetic stirring. After stirring for 30 min, let it stand, and the raw materials are completely dissolved, and no undissolved solid substances are seen at the bottom. Continue stirring magnetically, and use a pipette with a range of 200 µL to add H2O2 solution every 3 min, adding 20 µL each time. The total addition amount of H2O2 solution throughout the process is 3 mL. After the last addition of H2O2 solution, wait for another 3 min and then stop stirring. However, at this time, no precipitate is formed in the solution, and the solution finally remains transparent, and the expected (NH4)2MnF6 product is not generated.

[0046] Comparative Example 3

[0047] Weigh 1 g of KMnO4 and 20 g of NH4HF2, and add them into a transparent centrifuge tube containing 30 mL of HF solution in an ice-water bath under magnetic stirring. After stirring for 30 min, let it stand, and solid precipitation can be seen at the bottom. Then, continue stirring under magnetic force, and use a dropper with a volume of 2 mL to add H2O2 solution every 1 min, 0.5 mL each time. The total amount of H2O2 solution added throughout the process is 2.5 mL. After stirring for 30 min, the solution becomes brown and transparent, and no solid precipitation appears. Stop stirring, and the expected product (NH4)2MnF6 is not formed.

[0048] Solubility experiment

[0049] Weigh 0.1 g of K2MnF6 or (NH4)2MnF6 prepared in Example 2, and add them into separate polytetrafluoroethylene test tubes with a volume of 50 mL. Slowly add hydrofluoric acid solution drop by drop, and record the amount of hydrofluoric acid solution required to completely dissolve the two manganese-containing compounds at room temperature. It is found that 3.5 mL of HF solution is needed to dissolve 0.1 g of K2MnF6, while only 1.5 mL of HF solution is needed to dissolve 0.1 g of (NH4)2MnF6.

[0050] This experiment proves that the synthesized (NH4)2MnF6 of the present invention has a higher solubility compared to K2MnF6 and is a manganese source with high solubility. Its advantages are as follows: when used as a manganese source to prepare Mn 4+ When activating fluorescent materials, the amount of toxic hydrofluoric acid solution can be greatly reduced; in addition, when using the cooling crystallization method to grow Mn 4+ When activating fluoride fluorescent crystals, since the amount of hydrofluoric acid solvent is reduced when preparing a saturated solution, it is beneficial to improve the yield of the target fluorescent crystal in a certain cooling temperature range.

[0051] Application example

[0052] Take a 50 mL centrifuge tube, first add 10 mL of HF solution, then weigh 0.6502 g (3.65 mmol) of (NH4)2SiF6 and add it to the centrifuge tube. After stirring for 10 min, it is completely dissolved. Then weigh 0.1870 g (0.9125 mmol) of (NH4)2MnF6 prepared in Example 2 and add it to the above centrifuge tube. After stirring for 10 min, a transparent yellow saturated solution is formed. Then transfer the centrifuge tube to a low-temperature constant-temperature reaction bath device. Starting from 20 °C, slowly cool it at a rate of 1 °C every 30 min until it reaches -60 °C. After the cooling is completed, a large amount of yellow crystals can be seen at the bottom of the centrifuge tube. After sucking off the supernatant with a pipette, wash the crystal product three times with absolute ethanol and dry it in an oven at 70 °C for 2 h to obtain (NH4)2SiF6:Mn 4+Fluorescent crystal product.

[0053] Figure 5 Optical microscope image of the fluorescent crystal material prepared in this application example. Figure 5 The shown crystal exhibits the characteristics corresponding to the yellow body color of the Mn 4+ activated fluorescent material absorbing blue light.

[0054] Figure 6 Photoluminescence spectrum of the fluorescent crystal material prepared in this application example under the excitation of blue light at 460 nm. It can be seen from Figure 6 that the prepared fluorescent material exhibits narrow-band red light emission at 600 - 650 nm under the excitation of blue light at 460 nm. The six sharp emission peaks presented in the range of 600 - 650 nm belong to the fingerprint fluorescence characteristics of tetravalent manganese, indicating that tetravalent manganese has been successfully doped into the fluoride matrix as the luminescence center.

[0055] This application example proves the feasibility of preparing Mn 4+ activated fluoride fluorescent crystals using (NH4)2MnF6 as the manganese source.

Claims

1. A reduction-coprecipitation preparation method of (NH4)2MnF6, characterized in that, The steps are as follows: (1) Add KMnO4 and NH4HF2 / NH4F into hydrofluoric acid to obtain system A; wherein, the dosage ratio of raw materials is KMnO4∶NH4HF2 / NH4F∶hydrofluoric acid = 0.006 mol∶(0.35 - 0.45) mol∶(30 - 40) mL; (2) Add H2O2 solution to system A in the following manner (i) or (ii), and the total addition amount of H2O2 solution throughout the process is 2.5 - 3.0 mL to obtain system B; Manner (i): Add H2O2 solution every 3 minutes, and add 20 - 30 μL each time; Manner (ii): First, add H2O2 solution every 1 minute, and add 0.2 - 0.5 mL each time, with a total addition amount of 1 - 1.5 mL; after stirring for 20 - 30 minutes, change to add H2O2 solution every 3 minutes, and add 20 - 30 μL each time until the remaining H2O2 solution is added; (3) After the first solid-liquid separation of system B, collect the precipitate of the first solid-liquid separation, wash and dry it to obtain the target product; The whole process of steps (1) - (2) is operated under ice-water bath and stirring conditions.

2. The reduction-coprecipitation preparation method of (NH4)2MnF6 according to claim 1, characterized in that: In step (3), collect the precipitate of the first solid-liquid separation, add acetic acid / hydrofluoric acid to this precipitate, perform the second solid-liquid separation, collect the precipitate of the second solid-liquid separation, wash and dry it to obtain the target product.

3. The reduction-coprecipitation preparation method of (NH4)2MnF6 according to claim 2, characterized in that: In step (3), add 1 - 2 mL of acetic acid / hydrofluoric acid to every 0.5 g of the precipitate after the first solid-liquid separation.

4. The reduction-coprecipitation preparation method of (NH4)2MnF6 according to claim 1, characterized in that: In step (3), collect the precipitate after the first solid-liquid separation, first add hydrofluoric acid to this precipitate, perform the second solid-liquid separation, collect the precipitate of the second solid-liquid separation, then add acetic acid to this precipitate, perform the third solid-liquid separation, collect the precipitate of the third solid-liquid separation, wash and dry it to obtain the target product.

5. The reduction-coprecipitation preparation method of (NH4)2MnF6 according to claim 4, characterized in that: In step (3), add 1 - 2 mL of hydrofluoric acid to every 0.5 g of the precipitate after the first solid-liquid separation, and add 2 - 4 mL of acetic acid to every 0.5 g of the precipitate after the second solid-liquid separation.

6. The reduction-coprecipitation preparation method of (NH4)2MnF6 according to any one of claims 1 to 5, characterized in that: When washing, the detergent used is acetone, methanol or ethanol; when drying, vacuum drying or air-blowing drying is used, and after drying, place the obtained target product in a desiccator or vacuum environment for storage.

7. The reduction-coprecipitation preparation method of (NH4)2MnF6 according to any one of claims 1 to 5, characterized in that: The concentration of all hydrofluoric acid involved is 10 - 48 wt%.

8. The reduction-coprecipitation preparation method of (NH4)2MnF6 according to any one of claims 1 to 5, characterized in that: All solid-liquid separations involved are centrifugal separations, with a centrifugal speed of 5000 - 10000 rpm and a centrifugal time of 2 - 5 minutes.

9. The reduction-coprecipitation preparation method of (NH4)2MnF6 as claimed in claim 1, characterized in that: The concentration of the H2O2 solution is 20 - 40 wt%.

10. Application of (NH4)2MnF6, characterized in that: As a manganese source for preparing Mn 4+ activated fluorescent crystal materials.

Images