Lanthanum oxyfluoride compound as well as preparation method and application thereof
Lanthanum oxyfluoride was prepared by adjusting the pH value and reflux calcination, which solved the problems of complicated preparation process and uncontrollable particle morphology in the existing technology. Fine and uniform lanthanum oxyfluoride powder was obtained, which is suitable for fluorescent display, information storage and laser fields.
Patent Information
- Application Number
- CN202511250675.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-03
- Publication Date
- 2025-11-04
AI Technical Summary
Existing methods for preparing lanthanum oxyfluoride have problems such as complicated processes, easy introduction of impurity phases, large particle size and uncontrollable morphology, making it difficult to obtain fine, uniformly distributed, and well-crystallized lanthanum oxyfluoride powder.
Lanthanum fluoride compounds were prepared by adding ammonia water dropwise to a rare earth nitrate solution to adjust the pH to 9-10, aging it at a constant temperature, refluxing it with a sodium fluoride solution, and finally calcining it.
This method enables the preparation of fine, uniformly distributed, and well-crystallized lanthanum oxyfluoride powders of different crystal forms under mild conditions, simplifying the operation steps and reducing equipment requirements.
Smart Images
Figure CN120887449A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of inorganic non-metallic materials technology, specifically relating to a lanthanum fluoride compound, its preparation method, and its application. Background Technology
[0002] Oxyfluorides possess the advantages of both oxides and fluorides, exhibiting remarkable properties such as low phonon energy, high optical band gap, weak multiphonon interactions, excellent mechanical strength, and thermochemical stability. Among these, lanthanum oxyfluoride, due to its La... 3+ Lanthanum oxyfluoride ions have a larger ionic radius than other lanthanide elements, which is beneficial for constructing stable crystal structures and reducing the non-radiative quenching of excited states by the lattice, thereby achieving higher luminescence efficiency. Due to its excellent optical properties and structural stability, lanthanum oxyfluoride materials have been widely used in various fields such as fluorescent probes, anti-counterfeiting labels, information encryption, and optoelectronic devices. Currently, commonly used preparation methods for lanthanum oxyfluoride include coprecipitation, hydrothermal methods, solid-state methods, and sol-gel methods. Among these, the coprecipitation method is simple but easily introduces impurity phases; the hydrothermal method can obtain highly crystalline nanoparticles but requires high-pressure equipment and has a long reaction cycle; the solid-state method produces good crystallinity but results in large particle sizes and uncontrollable morphology; and the sol-gel method has the problem of cumbersome processes. Summary of the Invention
[0003] In view of this, the present invention provides a lanthanum fluoride compound, its preparation method and application. The preparation method provided by the present invention is simple, and lanthanum fluoride compounds with different crystal phases can be prepared according to the preparation method provided by the present invention. Moreover, the prepared lanthanum fluoride compounds have fine particles, uniform distribution and good crystallinity.
[0004] To address the aforementioned technical problems, this invention provides a method for preparing lanthanum fluoride compounds, comprising the following steps:
[0005] Ammonia water was added dropwise to a rare earth nitrate solution to adjust the pH to 9-10, and the solution was kept at a certain temperature for aging to obtain precipitate A; the rare earth nitrate in the rare earth nitrate solution included lanthanum nitrate.
[0006] The precipitate A was mixed with sodium fluoride solution and then refluxed to obtain precipitate B;
[0007] The precipitate B was calcined to obtain lanthanum fluoride compounds.
[0008] Preferably, the rare earth nitrate further includes one or more of praseodymium nitrate, neodymium nitrate, samarium nitrate, europium nitrate, gadolinium nitrate, terbium nitrate, dysprosium nitrate, erbium nitrate, ytterbium nitrate, lutetium nitrate, and holmium nitrate; the lanthanum nitrate accounts for more than 80% of the total molar percentage of the rare earth nitrate.
[0009] The molar concentration of all rare earth ions in the rare earth nitrate solution is 0.01-1 mol / L.
[0010] The molar concentration of the ammonia water is 0.5-3 mol / L.
[0011] Preferably, the dropping rate is 2-3 s per drop.
[0012] The temperature of the heat preservation aging is 5-80 DEG C, and the time is 0.5-2 h.
[0013] Preferably, the heat preservation aging further comprises:
[0014] The system after the heat preservation aging is subjected to a first solid-liquid separation, and the solid obtained by the first solid-liquid separation is subjected to a first water washing and a first ethanol washing in sequence to obtain the precipitate A.
[0015] Preferably, the first solid-liquid separation comprises a first centrifugation, and the rotation speed of the first centrifugation is 5000-7000 r / min, and the time is 4-6 min.
[0016] Preferably, the molar ratio of the rare earth element in the rare earth nitrate to the fluorine element in the sodium fluoride solution is 1:1-20.
[0017] The temperature of the refluxing is 40-100 DEG C, and the time is 2-24 h; the refluxing process is accompanied by stirring.
[0018] The system after the refluxing further comprises a second solid-liquid separation, and the solid obtained by the second solid-liquid separation is subjected to a second water washing, a second ethanol washing and drying in sequence to obtain the precipitate B.
[0019] Preferably, the second solid-liquid separation comprises a second centrifugation, and the rotation speed of the second centrifugation is 5000-7000 r / min, and the time is 4-6 min.
[0020] The temperature of the drying is 60-80 DEG C, and the time is 10-20 h.
[0021] Preferably, the temperature of the calcining is 300-1200 DEG C, and the time is 2-5 h.
[0022] The application further provides a lanthanum oxyfluoride compound prepared by the preparation method, including lanthanum oxyfluoride or doped lanthanum oxyfluoride.
[0023] The application further provides an application of the lanthanum oxyfluoride compound in the fields of fluorescent display, information storage, anti-fake encryption or laser.
[0024] This invention provides a method for preparing lanthanum oxyfluoride compounds, comprising the following steps: adding ammonia water dropwise to a rare earth nitrate solution to adjust the pH to 9-10, and aging at a constant temperature to obtain precipitate A; the rare earth nitrate solution includes lanthanum nitrate; mixing precipitate A with a sodium fluoride solution and refluxing to obtain precipitate B; calcining precipitate B to obtain lanthanum oxyfluoride compounds. This invention first prepares a rare earth layered hydroxide by adjusting the pH by adding ammonia water dropwise, then substitutes it with sodium fluoride to obtain sodium pentafluorofluorofluoride, and finally calcines it to obtain lanthanum oxyfluoride powders of different crystal forms. The entire process has mild reaction conditions and simple operation steps. Using synthesized sodium pentafluorofluorofluoride powder as a precursor, this invention prepares lanthanum oxyfluoride particles of different crystal forms that are fine, uniformly distributed, and have good crystallinity. Attached Figure Description
[0025] Figure 1 The XRD pattern of the Na2LaF5 powder prepared in Example 1 is shown below.
[0026] Figure 2 Here is a SEM image of the Na2LaF5 powder prepared in Example 1;
[0027] Figure 3 EDS image of Na2LaF5 powder prepared in Example 1;
[0028] Figure 4 The XRD pattern of the cubic LaOF powder prepared in Example 1;
[0029] Figure 5 The image shows the SEM image of the cubic LaOF powder prepared in Example 1.
[0030] Figure 6 The XRD pattern of the tetragonal LaOF powder prepared in Example 2 is shown below.
[0031] Figure 7 The image shows the SEM image of the tetragonal LaOF powder prepared in Example 2.
[0032] Figure 8 The XRD pattern of the hexagonal phase-doped LaOF powder prepared in Example 3 is shown below.
[0033] Figure 9 The image shows the SEM pattern of the hexagonal phase-doped LaOF powder prepared in Example 3. Detailed Implementation
[0034] This invention provides a method for preparing lanthanum fluoride compounds, comprising the following steps:
[0035] The ammonia water is added dropwise into the rare earth nitrate solution to adjust the pH value to 9-10, and then the precipitation A is obtained by incubation and aging.
[0036] The precipitation A is mixed with the sodium fluoride solution and then refluxed to obtain the precipitation B.
[0037] The precipitation B is calcined to obtain the lanthanum oxyfluoride compound.
[0038] In the present application, the ammonia water is added dropwise into the rare earth nitrate solution to adjust the pH value to 9-10, and then the precipitation A is obtained by incubation and aging. In one embodiment of the present application, the rare earth nitrate solution can be prepared by dissolving the rare earth nitrate in water. In one embodiment of the present application, the rare earth nitrate in the rare earth nitrate solution includes lanthanum nitrate, and can also include one or more of praseodymium nitrate, neodymium nitrate, samarium nitrate, europium nitrate, gadolinium nitrate, terbium nitrate, dysprosium nitrate, erbium nitrate, ytterbium nitrate, lutetium nitrate and holmium nitrate. The total molar percentage of the lanthanum nitrate in the rare earth nitrate can be more than 80%, and can also be 95-100%, and can be specifically 98% or 100%. In the embodiments of the present application, the rare earth nitrate is a mixture of lanthanum nitrate and europium nitrate with a molar ratio of 98:2, or is lanthanum nitrate. The lanthanum nitrate can be lanthanum nitrate hexahydrate, and the europium nitrate can be europium nitrate hexahydrate. The dissolution has no special limitation in the present application, as long as it can be completely dissolved.
[0039] In one embodiment of the present application, the molar concentration of all rare earth ions in the rare earth nitrate solution can be 0.01-1 mol / L, and can be specifically 0.05 mol / L, 0.1 mol / L, 0.5 mol / L or 1 mol / L.
[0040] In one embodiment of the present application, the molar concentration of the ammonia water can be 0.5-3 mol / L, and can be specifically 0.5 mol / L, 0.8 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L or 3 mol / L. The dropping rate can be 2-3 s per drop, and can be specifically 2 s per drop or 3 s per drop. The dropping process can be accompanied by stirring.
[0041] In one embodiment of the present application, the pH value of the system after mixing the ammonia water and the rare earth nitrate solution can be 9-10, and can be specifically 9, 9.5 or 10. The present application has no special requirement for the amount of ammonia water, as long as the desired pH value can be achieved.
[0042] As a specific embodiment of the present application, the temperature of the incubation aging can be 5-80℃, can also be 10-25℃, can further be 15-23℃, and can specifically be 10℃, 13℃, 15℃, 20℃, 23℃, 30℃, 40℃, 50℃, 60℃, 70℃ or 75℃; the time of the incubation aging can be 0.5-2h, and can specifically be 0.5h, 1h, 1.5h or 2h.
[0043] In the present application, taking the rare earth nitrate salt, lanthanum nitrate hexahydrate, as an example, the reaction occurring in the incubation aging process is shown in formula a:
[0044] La(NO3)3·6H2O + 2NH3·H2O → La(OH)2NO3·2H2O↓ + 2NH4NO3 + 4H2O Formula a.
[0045] As a specific embodiment of the present application, the incubation aging further comprises: performing first solid-liquid separation on the incubation aging system, and sequentially performing first water washing and first ethanol washing on the solid obtained by the first solid-liquid separation to obtain the precipitate A.
[0046] As a specific embodiment of the present application, the first solid-liquid separation comprises first centrifugation, the speed of which can be 5000-7000r / min, and can specifically be 5500r / min, 6000r / min, 6500r / min or 7000r / min; the time of the first centrifugation can be 4-6min, and can specifically be 4min, 5min or 6min; the water used for the first water washing can be deionized water, and the number of times of the first water washing can be 2-4 times, and can specifically be 3 times; the solvent used for the first ethanol washing can be anhydrous ethanol, and the number of times of the first ethanol washing can be 1-3 times, and can specifically be 2 times.
[0047] In the present application, the precipitate A is a 121-type layered hydroxide;
[0048] After obtaining the precipitate A, the present application refluxes the precipitate A and a sodium fluoride solution to obtain a precipitate B. As a specific embodiment of the present application, the molar concentration of the sodium fluoride solution can be 0.1-0.5mol / L, and can specifically be 0.2mol / L, 0.3mol / L, 0.4mol / L or 0.5mol / L; the molar ratio of the rare earth element in the rare earth nitrate salt to the fluorine element in the sodium fluoride solution can be 1:1-20, and can specifically be 1:5, 1:8, 1:10 or 1:15.
[0049] As a specific embodiment of the present application, the temperature of the refluxing can be 40-100℃, and can be specifically 50℃, 60℃, 80℃ or 90℃; the time of the refluxing can be 2-24h, and can be specifically 5h, 8h, 13h, 18h or 20h. In the present application, the refluxing can be accompanied by stirring; the present application has no special requirements for the rotating speed of the stirring, as long as the system is uniform.
[0050] In the present application, taking the rare earth nitrate salt, lanthanum nitrate hexahydrate, as an example, a double decomposition reaction and crystallization occur in the refluxing process, and the reaction equation is shown in formula b:
[0051] La(OH)2NO3·2H2O + 5NaF → Na2LaF5↓ + NaNO3 + 2NaOH + 2H2O Formula b.
[0052] As a specific embodiment of the present application, the refluxing can further comprise: performing a second solid-liquid separation on the system after the refluxing, and sequentially performing a second water washing, a second ethanol washing and a drying on the solid obtained by the second solid-liquid separation, to obtain the precipitate B.
[0053] As a specific embodiment of the present application, the second solid-liquid separation comprises a second centrifugation, the rotating speed of the second centrifugation can be 5000-7000r / min, and can be specifically 5000r / min, 5500r / min, 6000r / min or 6500r / min; the time of the second centrifugation can be 4-6min, and can be specifically 4min, 5min or 6min; the water for the second water washing can be deionized water, the number of times of the second water washing can be 2-4 times, and can be specifically 3 times; the solvent for the second ethanol washing can be anhydrous ethanol, the number of times of the second ethanol washing can be 1-3 times, and can be specifically 2 times; the temperature of the drying can be 60-80℃, and can be specifically 65℃, 70℃ or 75℃; the time of the drying can be 10-20h, and can be specifically 10h, 13h, 16h, 18h or 20h.
[0054] After obtaining the precipitate B, the present application calcines the precipitate B to obtain a lanthanum oxyfluoride compound. As a specific embodiment of the present application, the temperature of the calcining can be 300-1200℃, and can be specifically 350℃, 500℃, 650℃, 800℃, 900℃ or 1000℃; the time of the calcining can be 2-5h, and can be specifically 2.5h, 3h, 3.5h, 4h or 4.5h.
[0055] The lanthanum oxyfluoride compound of different crystal forms can be obtained by calcining at different temperatures. When the calcining temperature is 300-400℃, the lanthanum oxyfluoride compound is cubic phase; when the calcining temperature is 600-700℃, the lanthanum oxyfluoride compound is tetragonal phase; when the calcining temperature is 950-1100℃, the lanthanum oxyfluoride compound is hexagonal phase. The product formed at the calcining temperature outside the above temperature range is a mixture of cubic phase, tetragonal phase and hexagonal phase, for example, the product obtained by calcining at a temperature greater than 400℃ and less than 600℃ is a mixture of cubic phase and tetragonal phase; the product obtained by calcining at a temperature greater than 700℃ and less than 950℃ is a mixture of tetragonal phase and hexagonal phase.
[0056] In the present application, taking the rare earth nitrate, lanthanum nitrate hexahydrate, as an example, a high-stable phase reaction occurs in the calcining process, and the reaction equation is shown in formula c:
[0057] Na2LaF5+1 / 2O2→LaOF+2NaF+F2↑Formula c.
[0058] The present application also provides a lanthanum oxyfluoride compound prepared by the preparation method described in the above technical solution, including lanthanum oxyfluoride or doped lanthanum oxyfluoride. The crystal phase of the lanthanum oxyfluoride compound includes cubic phase, tetragonal phase or hexagonal phase. The lanthanum oxyfluoride is cubic phase LaOF, tetragonal phase LaOF or hexagonal phase LaOF, and the doped lanthanum oxyfluoride can include Eu-doped LaOF. In the present application, the average particle size of the lanthanum oxyfluoride compound can be 0.05-20μm.
[0059] The present application adopts a low-temperature process, is simple to operate, has low requirements on equipment, and can effectively inhibit particle agglomeration and generation of impurities under mild conditions. The present application takes sodium lanthanum fluoride as a precursor, and can obtain lanthanum oxyfluoride powder of cubic phase, tetragonal phase and hexagonal phase by adjusting the calcining temperature.
[0060] The present application also provides application of the lanthanum oxyfluoride compound described in the above technical solution in the fields of fluorescent display, information storage, anti-counterfeiting encryption or laser.
[0061] In order to further illustrate the present application, the technical solutions provided by the present application are described in detail below in combination with examples, but they should not be understood as limiting the scope of protection of the present application.
[0062] Example 1
[0063] (1) Dissolve lanthanum nitrate hexahydrate (La(N03)3-6H20) in 100 mL of deionized water to obtain a lanthanum nitrate solution with a molar concentration of 0.2 mol / L; specifically, place the lanthanum nitrate hexahydrate and deionized water in a beaker with a magnetic stirrer, cover with plastic wrap, and place on a constant-temperature heating magnetic stirrer to stir for 0.5 h;
[0064] (2) Insert a pH meter into the lanthanum nitrate solution to monitor the pH value of the solution. When the pH value is stable at about 6, adjust the pH value of the system to 9.5 by adding ammonia water with a molar concentration of 2 mol / L at a rate of 2 s per drop. Stir the solution during the addition process, and the solution gradually becomes turbid. After stopping the addition, incubate at 23°C for 0.5 h;
[0065] (3) After incubation, the system appears to be layered. Discard the supernatant, and transfer the lower layer of the precipitate to a centrifuge tube and centrifuge at 6000 r / min for 5 min. Wash the obtained solid with deionized water 3 times and with anhydrous ethanol 2 times, respectively, to obtain white precipitate A;
[0066] (4) Mix the white precipitate A with a sodium fluoride (NaF) solution with a molar concentration of 0.5 mol / L, and reflux (with stirring) at 80°C for 10 h, wherein the molar ratio of sodium fluoride to lanthanum nitrate hexahydrate is 5:1;
[0067] (5) After the reflux reaction is completed, a layered suspension is obtained. Discard the supernatant, and transfer the lower layer of the precipitate to a centrifuge tube and centrifuge at 6000 r / min for 5 min. Wash the obtained solid with deionized water 3 times and with anhydrous ethanol 2 times, respectively, and finally dry at 70°C for 10 h to obtain white Na2LaF5 powder;
[0068] (6) Calcine the Na2LaF5 powder at 350°C for 4 h to obtain cubic phase LaOF powder.
[0069] Example 2
[0070] Prepare the LaOF powder according to the method of Example 1, except that the calcination temperature is 650°C, and the obtained LaOF powder is tetragonal phase LaOF powder.
[0071] Example 3
[0072] (1) Dissolve lanthanum nitrate hexahydrate (La(NO3)3·6H2O) and europium nitrate hexahydrate (Eu(NO3)3·6H2O) in 100 mL of deionized water to obtain a mixed solution of lanthanum nitrate and europium nitrate, wherein the molar concentration of lanthanum nitrate is 0.196 mol / L and the molar concentration of europium nitrate is 0.04 mol / L; specifically, place lanthanum nitrate hexahydrate, europium nitrate hexahydrate and deionized water in a beaker equipped with a magnetic stir bar, cover with plastic wrap, and place on a constant temperature heating magnetic stirrer and stir for 0.5 h;
[0073] (2) Insert a pH meter into the mixed solution of lanthanum nitrate and europium nitrate to monitor the pH value of the solution. When the pH value stabilizes at about 6, add ammonia water with a molar concentration of 2 mol / L at a rate of 2 drops per second to adjust the pH value of the system to 9.5. Keep stirring during the addition process, and the solution gradually becomes turbid. After stopping the addition, keep it at 23°C for 0.5 h.
[0074] (3) After the heat preservation and aging process is completed, the system will be divided into upper and lower layers; discard the upper clear liquid, transfer the lower precipitate to a centrifuge tube and centrifuge at 6000 r / min for 5 min. Wash the solid obtained by centrifugation with deionized water 3 times and anhydrous ethanol 2 times to obtain white precipitate A.
[0075] (4) Mix white precipitate A with a sodium fluoride (NaF) solution with a molar concentration of 0.5 mol / L and reflux at 80°C (with stirring) for 10 h, wherein the molar ratio of sodium fluoride to lanthanum nitrate hexahydrate is 5:1;
[0076] (5) After the reflux reaction is complete, a layered suspension is obtained. The supernatant is discarded, and the lower precipitate is transferred to a centrifuge tube and centrifuged at 6000 r / min for 5 min. The solid obtained by centrifugation is washed three times with deionized water and twice with anhydrous ethanol. Finally, it is dried at 70℃ for 10 h to obtain white La. 0.98 Eu 0.02 F5 powder;
[0077] (6) La 0.98 Eu 0.02 F5 powder was calcined at 1000℃ for 4 hours to obtain hexagonal doped LaOF powder, denoted as LaOF:0.02Eu. 3+ powder.
[0078] X-ray diffraction was performed on the Na2LaF5 powder prepared in Example 1, and the XRD pattern was obtained, as shown below. Figure 1 As shown. From Figure 1 It can be seen that the XRD pattern of Na2LaF5 is highly consistent with the characteristic peaks of K2PrF5 in the standard card (PDF#40-0824), indicating that the white powder prepared in the example has a crystal structure similar to K2PrF5.
[0079] The Na2LaF5 powder prepared in Example 1 was subjected to scanning electron microscopy (SEM) analysis, and SEM and EDS images were obtained, as shown below. Figures 2-3 As shown. Among them Figure 2 This is a SEM image of the Na2LaF5 powder prepared in Example 1. Figure 3 The image shows the EDS spectrum of the Na₂LaF₅ powder prepared in Example 1. Figure 2 It can be seen that the powder microstructure consists of a large number of plate-like or rod-like structures, indicating that the Na2LaF5 powder prepared by this invention has fine and uniform particles and high crystal regularity. Figure 3 This indicates that the present invention successfully prepared Na2LaF5 powder.
[0080] X-ray diffraction was performed on the LaOF powder prepared in Example 1 to obtain the XRD pattern, as shown below. Figure 4 As shown, from Figure 4 It can be seen that the XRD pattern of the cubic LaOF powder is the same as that of the standard card in PDF#77-0204, indicating that the cubic LaOF powder was successfully prepared by this invention.
[0081] The LaOF powder prepared in Example 1 was subjected to scanning electron microscopy (SEM) to obtain SEM images, as shown below. Figure 5 As shown, from Figure 5 It can be seen that the powder has a regular plate-like or plate-like structure with clear crystal faces and distinct boundaries, indicating that the cubic LaOF powder particles prepared by this invention have a high degree of crystallinity.
[0082] X-ray diffraction was performed on the LaOF powder prepared in Example 2 to obtain the XRD pattern, as shown below. Figure 6 As shown, from Figure 6 It can be seen that the XRD pattern of the tetragonal LaOF powder is the same as that of the standard card in PDF#44-0121, indicating that the tetragonal LaOF powder was successfully prepared in this invention.
[0083] The LaOF powder prepared in Example 2 was subjected to scanning electron microscopy (SEM) to obtain SEM images, as shown below. Figure 7 As shown, from Figure 7 It can be seen that the powder has a spherical or near-spherical microstructure, indicating that the tetragonal LaOF powder prepared by this invention has a high degree of crystallinity, and that heat treatment promotes the spheroidization and recrystallization of the crystals.
[0084] The LaOF:0.02Eu prepared in Example 3 3+ The powder was subjected to X-ray diffraction analysis to obtain the XRD pattern, as shown below. Figure 8 As shown, from Figure 8It can be seen that the XRD pattern of the hexagonal phase-doped LaOF powder is the same as that of the standard card in PDF#06-0281, indicating that the present invention has successfully prepared hexagonal phase LaOF powder.
[0085] The LaOF:0.02Eu prepared in Example 3 3+ The powder was examined using a scanning electron microscope (SEM) to obtain SEM images, such as... Figure 9 As shown, from Figure 9 It can be seen that the powder has a granular structure, indicating that the hexagonal LaOF powder particles prepared in this invention have high crystallinity.
[0086] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.
Claims
1. A method for preparing lanthanum fluoride compounds, characterized in that, Includes the following steps: Ammonia water was added dropwise to a rare earth nitrate solution to adjust the pH to 9-10, and the solution was kept at a warm temperature for aging to obtain precipitate A. The rare earth nitrate solution contains lanthanum nitrate. The precipitate A was mixed with sodium fluoride solution and then refluxed to obtain precipitate B; The precipitate B was calcined to obtain lanthanum fluoride compounds.
2. The preparation method according to claim 1, characterized in that, The rare earth nitrates also include one or more of the following: praseodymium nitrate, neodymium nitrate, samarium nitrate, europium nitrate, gadolinium nitrate, terbium nitrate, dysprosium nitrate, erbium nitrate, ytterbium nitrate, lutetium nitrate, and holmium nitrate; The molar concentration of all rare earth ions in the rare earth nitrate solution is 0.01–1 mol / L; the molar percentage of lanthanum nitrate in the total rare earth nitrate is more than 80%. The molar concentration of the ammonia water is 0.5–3 mol / L.
3. The preparation method according to claim 1 or 2, characterized in that, The dripping rate is 2-3 seconds per drop; The temperature for heat preservation and aging is 5–80℃, and the time is 0.5–2 hours.
4. The preparation method according to claim 3, characterized in that, The heat preservation and aging process also includes: The system after heat preservation and aging is subjected to a first solid-liquid separation. The solid obtained from the first solid-liquid separation is then washed with water and ethanol to obtain precipitate A.
5. The preparation method according to claim 4, characterized in that, The first solid-liquid separation includes a first centrifugation, wherein the centrifugation speed is 5000-7000 r / min and the time is 4-6 min.
6. The preparation method according to claim 1, characterized in that, The molar ratio of rare earth elements in the rare earth nitrate to fluorine in the sodium fluoride solution is 1:1 to 20. The reflux temperature is 40–100°C, and the time is 2–24 hours; The reflux process is accompanied by stirring; The process after reflux further includes: performing a second solid-liquid separation on the refluxed system, and sequentially subjecting the solid obtained from the second solid-liquid separation to a second water wash, a second ethanol wash, and drying to obtain the precipitate B.
7. The preparation method according to claim 6, characterized in that, The second solid-liquid separation includes a second centrifugation, wherein the centrifugation speed is 5000-7000 r / min and the time is 4-6 min; The drying temperature is 60–80°C, and the time is 10–20 hours.
8. The preparation method according to claim 1, characterized in that, The calcination temperature is 300–1200℃, and the time is 2–5 hours.
9. A lanthanum fluoride compound prepared according to any one of claims 1 to 8, characterized in that, It includes lanthanum oxyfluoride or doped lanthanum oxyfluoride; the crystal phase of the lanthanum oxyfluoride compound includes cubic, tetragonal or hexagonal phase.
10. The application of the lanthanum fluoride compound of claim 9 in the fields of fluorescent display, information storage, anti-counterfeiting encryption, or laser.