A method for preparing rare earth-doped green phosphor

Abstract

The invention discloses a rare earth doped green phosphor Na 1‑x BaB9O 15 :xEu 2+ The preparation method provided by the present invention utilizes a step-by-step acid-base neutralization reaction to obtain a precursor mixture, thereby reducing the potential energy barrier in the subsequent solid-phase synthesis reaction and making the Eu in the rare earth-doped green phosphor 2+ Ions only dope into the Na site in the matrix, not into the matrix NaBaB9O 15 The Ba lattice sites or lattice gaps in the lattice are removed, thereby improving the conversion efficiency of excitation light energy to green light emission energy. The method of the present invention is simple to operate, has a low synthesis temperature, a short synthesis time, and strong repeatability. The raw materials used are simple and readily available, and are not highly environmentally polluting, making it suitable for large-scale production. The resulting luminescent material can absorb energy from near-ultraviolet to blue light bands and emit green light with a main peak stably located at 515nm. It has high luminous efficiency and can serve as a supplement to the green fluorescent materials currently used in white light LED devices based on near-ultraviolet-blue light chips, and is applicable to devices in related fields such as lighting and display.

Description

Technical Field

[0001] The present invention relates to the field of luminescent materials, and in particular to a method for preparing rare earth-doped green phosphor. Background Art

[0002] Currently, phosphor-converted white light-emitting diodes (LEDs), comprised of semiconductor LED chips and phosphor packages, occupy a significant market share in lighting and display backlighting applications. These devices require fluorescent materials that absorb blue and near-ultraviolet light to effectively integrate with the LED chip. The development of fluorescent materials for the three primary colors (red, green, and blue) has long been a key research priority, as they can directly produce varying qualities of white light by adjusting the mixing ratio.

[0003] Currently, the most widely commercialized green fluorescent materials for LEDs, such as β-SiAlON:Eu, require high-purity raw materials and high-temperature and high-pressure synthesis conditions, so the production cost is relatively high. It is necessary to find a high-efficiency and low-cost alternative green fluorescent material for LEDs. 15 It is a readily available matrix material. When the rare earth ion Eu 2+ When doped into the Na lattice, it can absorb the energy of the near ultraviolet-blue light band and emit green light. 2+ Napier + Closer to Eu 2+ ionic charge, so in general Eu 2+ It tends to enter the Ba grid and obtains NaBaB9O with blue light emission or blue-green mixed emission. 15 :Eu 2+ Controllable Eu 2+ The research on doping into Na sites has important application value.

[0004] Patent CN 202080058748.0 introduces a method for obtaining green doped phosphor A 1-x Eu x Ba 1-y Sr y B9O 15 :Eu 2+ (A is an alkali metal) preparation method, the preparation method first mixes the raw materials and then places them for several weeks, then sintering them in air, and then reducing them under reducing gas for dozens of hours. Although this preparation method can produce Eu 2+ Doping into NaBaB9O 15 The phosphor with Na lattice is produced by a very complicated experimental procedure and uncertain experimental conditions. It needs to undergo several weeks of aging process and multi-stage calcination treatment in an air environment with unspecified temperature or humidity, and the calcination time is up to 30 hours. Summary of the Invention

[0005] In order to solve the above defects in the prior art, a method is provided to 2+ Controllable doping into NaBaB9O 15 The primary purpose of the present invention is to provide a method for preparing rare earth doped green phosphor.

[0006] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0007] The present invention provides a method for preparing a rare earth-doped green phosphor, comprising the following steps:

[0008] S1. Barium hydroxide, boric acid, europium trioxide and water are mixed to form a first mixture;

[0009] S2. mixing a sodium source solution with the first mixture to form a second mixture, wherein the amount of sodium in the sodium source solution is (0.95 to 1.05) times the difference between the amount of barium in the barium hydroxide and the amount of europium in the europium trioxide;

[0010] S3. The second mixture is calcined in a reducing atmosphere, the calcination temperature is 750 to 800 ℃, the calcination time is 240 to 480min, and the green phosphor is obtained after cooling;

[0011] When the sodium source is sodium hydroxide, the molar ratio of the elements barium, boron and europium in the barium hydroxide, boric acid and europium trioxide is Ba:B:Eu=1-1.05:9-9.5:0.005-0.1;

[0012] or:

[0013] When the sodium source is sodium borate, the molar ratio of the elements barium, boron and europium in the barium hydroxide, boric acid and europium trioxide is Ba:B:Eu=1-1.05:7-7.5:0.005-0.1.

[0014] The present invention utilizes a step-by-step acid-base neutralization reaction to obtain a precursor mixture, thereby reducing the potential energy barrier in the subsequent solid-phase synthesis reaction and making Eu in the rare earth-doped green phosphor 2+ Ions only dope into the Na lattice in the matrix, not into the matrix NaBaB9O 15 The Ba lattice sites or lattice gaps in the green light can be increased, thereby improving the conversion efficiency of the excitation light energy to the green light emission energy.

[0015] In step S1, the mixed powder of barium hydroxide, boric acid and europium trioxide is mixed with water to provide a liquid phase environment for the acid-base neutralization reaction, so that the barium hydroxide and the boric acid can react completely to form a precursor - a barium borate salt, and the europium trioxide particles can be evenly distributed in the precursor.

[0016] In step S2, when the sodium source is sodium hydroxide, the sodium hydroxide reacts completely with the boric acid remaining after S1 to generate sodium borate salts, which then react with the precursor barium borate salts during the subsequent high-temperature sintering process to generate the matrix NaBaB9O 15 The purpose of mixing sodium hydroxide with the first mixture in the form of a solution is to provide a liquid phase environment for the acid-base neutralization reaction.

[0017] In step S2, sodium borate can also be selected as the sodium source. Sodium borate can directly react with the precursor barium borate under high temperature calcination to generate the matrix NaBaB9O 15 .

[0018] Preferably, when the sodium source is sodium hydroxide, the molar ratio of the elements barium, boron, and europium in the barium hydroxide, boric acid, and europium trioxide is Ba:B:Eu=1-1.05:9-9.5:0.01-0.05. More preferably, when the sodium source is sodium hydroxide, the molar ratio of the elements barium, boron, and europium in the barium hydroxide, boric acid, and europium trioxide is Ba:B:Eu=1-1.05:9-9.5:0.01-0.03.

[0019] Preferably, when the sodium source is sodium borate, the molar ratio of the elements barium, boron, and europium in the barium hydroxide, boric acid, and europium trioxide is Ba:B:Eu=1-1.05:7-7.5:0.01-0.05. More preferably, when the sodium source is sodium borate, the molar ratio of the elements barium, boron, and europium in the barium hydroxide, boric acid, and europium trioxide is Ba:B:Eu=1-1.05:7-7.5:0.01-0.03.

[0020] Preferably, the molar concentration of sodium in the sodium source solution is 0.4 to 0.6 mmol / mL. More preferably, the molar concentration of sodium in the sodium source solution is 0.48 to 0.55 mmol / mL.

[0021] Preferably, the solvent of the sodium source solution is water.

[0022] Preferably, the barium hydroxide is selected from hydrated barium hydroxide or anhydrous barium hydroxide. More preferably, the barium hydroxide is octahydrated barium hydroxide.

[0023] More preferably, the sodium hydroxide is selected from one of hydrated sodium hydroxide and anhydrous sodium hydroxide. More preferably, the sodium hydroxide is anhydrous sodium hydroxide.

[0024] Preferably, the sodium borate is selected from hydrated sodium tetraborate or anhydrous sodium tetraborate. More preferably, the sodium borate is anhydrous sodium tetraborate.

[0025] Preferably, the mass of water in S1 is (2 to 3) times the total mass of barium hydroxide, boric acid and europium trioxide.

[0026] Preferably, in S1, a mixed powder of barium hydroxide, boric acid and europium trioxide is mixed with water.

[0027] More preferably, the barium hydroxide, boric acid and europium trioxide are ground to obtain a mixed powder of the barium hydroxide, boric acid and europium trioxide. The grinding is to reduce the particle size of the raw materials, thereby increasing the contact surface between different raw materials and improving the reactivity of the raw materials.

[0028] More preferably, the mixed powder is transferred into a crucible after the grinding.

[0029] Preferably, the mixing in S1 is performed in a crucible.

[0030] More preferably, the crucible is a boron nitride crucible or a graphite crucible.

[0031] After grinding, the mixed powder is transferred to a crucible and mixed with water for subsequent reaction in order to reduce material loss. The crucible does not react with acidic and alkaline substances.

[0032] Preferably, the mixing means in S1 is stirring.

[0033] Preferably, the mixing time in S1 is 1 to 60 minutes.

[0034] Preferably, the mixing means in S2 is stirring.

[0035] Preferably, the mixing time in S2 is 1 to 60 minutes.

[0036] The mixing time in steps S1 and S2 can be long or short, as long as the materials can be mixed evenly.

[0037] Preferably, in S1, barium hydroxide, boric acid, europium trioxide and water are mixed, and free water is removed to form a first mixture.

[0038] Preferably, in S2, after the sodium source solution is mixed with the first mixture, free water is removed to form a second mixture.

[0039] More preferably, the means for removing free moisture is drying.

[0040] Preferably, the mass of free water in the first mixture is (0-2) times the total mass of barium hydroxide, boric acid and europium trioxide.

[0041] Preferably, the mass of free water in the second mixture is (0-2) times the total mass of barium hydroxide, boric acid, europium trioxide and sodium hydroxide.

[0042] The purpose of removing free water is to concentrate the mixture and increase the rate of subsequent reactions.

[0043] Preferably, in S3, the second mixture is pulverized before calcining. The pulverization is performed to increase the contact surface between the mixture and the reducing atmosphere, thereby facilitating the reduction of europium (III) in the mixture. More preferably, the pulverization is performed in a crucible.

[0044] Preferably, the calcination is carried out in a crucible.

[0045] More preferably, the crucible is a boron nitride crucible or a graphite crucible.

[0046] Preferably, the reducing atmosphere is a mixture of H2 and N2. More preferably, the reducing atmosphere is a mixture of H2 / N2 at a ratio of (5-10%): (95-90%).

[0047] Preferably, the heating rate of the calcination is 5 to 10° C. / min.

[0048] Preferably, the cooling rate is 1-3°C / min.

[0049] Preferably, the calcination conditions include: heating from room temperature to 750-800° C. at a heating rate of 5-10° C. / min, keeping the temperature for 240-480 min, and cooling to room temperature at a cooling rate of 1-3° C. / min.

[0050] Preferably, the chemical formula of the rare earth doped green phosphor is: Na 1-x BaB9O 15 :xEu 2+ , where 0.005≤x≤0.1.

[0051] More preferably, 0.01≤x≤0.05. More preferably, 0.01≤x≤0.03. More preferably, x is selected from 0.01 or 0.03.

[0052] Preferably, the rare earth-doped green phosphor has an emission peak of 515 nm at an excitation wavelength of 300 to 450 nm.

[0053] More preferably, the rare earth-doped green phosphor has an emission peak of only 515 nm at an excitation wavelength of 300-450 nm.

[0054] More preferably, the rare earth-doped green phosphor has an emission peak of only 515 nm at an excitation wavelength of 390 nm.

[0055] More preferably, the rare earth-doped green phosphor has an emission peak of only 515 nm at an excitation wavelength of 365 nm.

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] (1) The raw materials used in the preparation method provided by the present invention are simple and easy to obtain, and do not require long-term aging, pre-sintering treatment or long-term calcination. The operation is simple, the synthesis time is short, the repeatability is strong, no pollutants are generated in the production process, the calcination temperature is below 900°C, and the equipment requirements are low.

[0058] (2) The preparation method provided by the present invention is different from the traditional "one-pot" solid-phase synthesis method with uncertain conditions. The present invention first obtains the precursors in sequence through step-by-step acid-base neutralization reactions and then performs subsequent sintering to change the solid-phase reaction energy barrier and avoid Eu 2+ Doping into the matrix NaBaB9O 15 Ba lattice sites or lattice gaps in the lattice, stably and quickly obtain thermodynamically stable green phosphor Na 1-x BaB9O 15 :xEu 2+ This product only emits efficient green light with a main peak at 515nm under the excitation of 300-450nm near-ultraviolet-blue light. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 This is the X-ray diffraction spectrum of the rare earth-doped green phosphor in Example 1.

[0060] Figure 2 This is the room temperature excitation-emission spectrum of the rare earth-doped green phosphor in Example 1 and the actual image under irradiation of 365nm ultraviolet light.

[0061] Figure 3 The room temperature emission spectra of the rare earth-doped green phosphors in Examples 1 and 8 are compared with those in Comparative Examples 1 and 3.

[0062] Figure 4 This is the emission spectrum and luminescent color coordinate diagram of a white light device obtained by mixing the rare earth-doped green phosphor in Example 1 with commercially available blue and red phosphors and encapsulating a 365nm LED chip under 50mA driving current. DETAILED DESCRIPTION

[0063] The present invention will be further described below in conjunction with specific embodiments, but the examples do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the examples of the present invention are conventionally purchased raw materials and reagents.

[0064] Example 1

[0065] A rare earth doped green phosphor, the chemical formula of the fluorescent component is Na 0.97 BaB9O 15 :0.03Eu 2+ .

[0066] The rare earth doped green phosphor can be prepared by the following preparation method:

[0067] S1. Weigh 0.1577 g (0.500 mmol) of barium hydroxide octahydrate (Ba(OH)2·8H2O), 0.2921 g (4.70 mmol) of boric acid (H3BO3), and 0.0026 g (0.00739 mmol) of europium oxide (Eu2O3), mix them, and grind them uniformly in an agate mortar. Transfer them to a boron nitride crucible. Add 1 g of deionized water (H2O) to the mixture and stir for 5 minutes until a uniform, slurry-like mixture is formed. Place the crucible in a 70°C oven and dry the mixture for 30 minutes to obtain approximately 1.1 g of mixture A.

[0068] S2. Weigh 0.0194 g (0.485 mmol) of sodium hydroxide (NaOH) and dissolve it in 1 g of H₂O to obtain a clear NaOH solution. Add this solution dropwise to Mixture A in the crucible and stir for 5 minutes until a uniform wet mixture is obtained. Place the crucible in a 70°C oven and dry the wet mixture for 1 hour to obtain approximately 0.80 g of Mixture B.

[0069] S3. After stirring and crushing mixture B in a crucible, the crucible is placed in a tubular heating furnace and introduced with a reducing nitrogen-hydrogen mixture (5% H2 / 95% N2). The temperature is raised from room temperature to 800°C at a rate of 7°C / min. After holding in the reducing atmosphere for 360 minutes, the temperature is then lowered to room temperature at a rate of 3°C / min under the reducing atmosphere. The sample is removed and ground into a powder to obtain a white to light yellow powder, which is the rare earth-doped green phosphor.

[0070] Example 2

[0071] A rare earth doped green phosphor, the chemical formula of the fluorescent component is Na 0.97 BaB9O 15 :0.03Eu 2+The preparation method includes the same steps as those in Example 1, except that 0.1625 g (0.515 mmol) of Ba(OH)2·8H2O is weighed in S1, and the rest are the same as those in Example 1.

[0072] Example 3

[0073] A rare earth doped green phosphor, the chemical formula of the fluorescent component is Na 0.97 BaB9O 15 :0.03Eu 2+ The preparation method includes the same steps as those in Example 1, except that 0.2782 g (4.50 mmol) of H3BO3 is weighed in S1, and the rest are the same as those in Example 1.

[0074] Example 4

[0075] A rare earth doped green phosphor, the chemical formula of the fluorescent component is Na 0.99 BaB9O 15 :0.01Eu 2+ The preparation method includes the same steps as those in Example 1, except that 0.0009 g (0.00256 mmol) of Eu2O3 is weighed in S1, 0.0198 g (0.494 mmol) of NaOH is weighed in S2, and the rest are the same as those in Example 1.

[0076] Example 5

[0077] A rare earth doped green phosphor, the chemical formula of the fluorescent component is Na 0.97 BaB9O 15 :0.03Eu 2+ The preparation method includes the same steps as those in Example 1, except that the temperature in S3 is raised to 750° C. at a heating rate of 7° C. / min. Other steps are the same as those in Example 1.

[0078] Example 6

[0079] A rare earth doped green phosphor, the chemical formula of the fluorescent component is Na 0.97 BaB9O 15 :0.03Eu 2+ The preparation method includes the same steps as those in Example 1, except that S3 is kept in a reducing atmosphere for 480 minutes. Other steps are the same as those in Example 1.

[0080] Example 7

[0081] A rare earth doped green phosphor, the chemical formula of the fluorescent component is Na 0.97 BaB9O 15 :0.03Eu 2+The preparation method includes the same steps as those in Example 1, except that the wet material is not dried in S2. Other steps are the same as those in Example 1.

[0082] Example 8

[0083] A rare earth doped green phosphor, the chemical formula of the fluorescent component is Na 0.97 BaB9O 15 :0.03Eu 2+ The preparation method includes the same steps as those in Example 1, except that the amount of H3BO3 in S1 is changed to 0.2183 g (3.53 mmol), and the NaOH in S2 is replaced with an equivalent amount of anhydrous Na2B4O7 0.0488 g (0.2425 mmol). Other steps are the same as those in Example 1.

[0084] Comparative Example 1

[0085] A rare earth doped phosphor, the preparation method of which is as follows:

[0086] Weigh 0.3947 g (2 mmol) of barium carbonate BaCO3, 0.1028 g (0.97 mmol) of sodium carbonate Na2CO3, 1.1129 g (18 mmol) of boric acid H3BO3, and 0.0106 g (0.030 mmol) of europium oxide Eu2O3, mix them, grind them evenly in an agate mortar, and then transfer them to a corundum crucible.

[0087] The corundum crucible was placed in a box furnace for pre-sintering, and the temperature was raised from room temperature to 600°C at a heating rate of 5°C / min. After being kept in an air atmosphere for 6 hours, it was naturally cooled to room temperature, and the pre-sintered product was ground twice.

[0088] The secondary ground product was transferred to a corundum crucible, which was placed in a tubular furnace. A reducing nitrogen-hydrogen mixture (5% H₂ / 95% N₂) was introduced, and the temperature was raised from room temperature to 725°C at a rate of 3°C / min. After holding in the reducing atmosphere for 30 hours, the temperature was then lowered to room temperature at a rate of 3°C / min under the reducing atmosphere. The sample was removed and ground into a powder, yielding Comparative Example 1.

[0089] Comparative Example 2

[0090] A rare earth doped phosphor, the preparation method of which is as follows:

[0091] Weigh 0.1577g of Ba(OH)2·8H2O, 0.0194g of NaOH, 0.0026g of Eu2O3, 0.0026g of Eu2O3 and 1g of H2O, mix them, and grind them evenly in an agate mortar. Continue to add 0.2921g of H3BO3 and grind them a second time until they are evenly distributed. After the mixture is completely dried in a 70°C oven, transfer it to a boron nitride crucible. Place the crucible in a tubular heating furnace, introduce a reducing nitrogen and hydrogen mixture of 5% H2 / 95% N2, and heat it from room temperature to 750°C at a rate of 3°C / min. After keeping it warm in a reducing atmosphere for 360 minutes, cool it down to room temperature at a rate of 3°C / min under the protection of a reducing atmosphere. After taking out the sample, grind it into powder to obtain comparative example sample 2.

[0092] Comparative Example 3

[0093] A rare earth-doped phosphor, the preparation method of which comprises the same steps as those in Example 1, except that in S2, NaOH is replaced with 0.0407 g of sodium bicarbonate NaHCO3 of an equivalent amount. Other steps are the same as those in Example 1.

[0094] Performance Testing

[0095] 1. Luminescence properties

[0096] The X-ray diffraction pattern of the phosphor obtained in Example 1 is shown in the attached figure. Figure 1 As shown, the standard card JCPDS 51-1611 (NaBaB9O 15 ) In contrast, except for a small amount of barium borate peak, the X-ray diffraction pattern of the green phosphor is basically consistent with the standard card. Combined with the luminescence performance test and comparison with existing reports, it is shown that the rare earth doped green phosphor is Na 0.97 BaB9O 15 :0.03Eu 2+ , impurities have no obvious effect on luminescence.

[0097] The room temperature excitation spectrum (fixed monitoring wavelength 515nm) and emission spectrum (excitation wavelength 390nm) of the phosphor obtained in Example 1 are as follows: Figure 2 shown. Figure 2 The inset is a real picture under 365nm ultraviolet light irradiation, and bright green light emission is visible to the naked eye. This rare earth doped green phosphor can be effectively excited by 300-450nm near-ultraviolet-blue light, with the strongest excitation position located at around 390nm; under 390nm light excitation, the sample's emission is mainly green light emission at around 515nm, with luminescence color coordinates of (0.215, 0.625) and luminescence internal quantum efficiency of 61.67% (the calculation method of luminescence color coordinates and luminescence internal quantum efficiency can adopt conventional methods in this field). Sample data shows that the Eu in the sample of this embodiment2+ Only NaBaB9O was incorporated 15 The Na lattice sites are suitable for use as green phosphors for white light LEDs based on InGaN near-ultraviolet-blue light chips. The luminescent properties of the phosphors obtained in Examples 2 to 7 are comparable to those of the phosphor obtained in Example 1.

[0098] The room temperature emission spectrum (excitation wavelength is 365 nm) of the phosphor obtained in Example 8 is as follows: Figure 3 The luminescent properties of the phosphor obtained in Example 8 are similar to those in Example 1. Under 365nm light excitation, the emission spectrum only contains the green emission peak with the maximum peak at 515nm. This result further illustrates that according to the preparation method of the present invention, Eu 2+ Enter NaBaB9O only 15 The Na lattice site is suitable for preparing green phosphors for white light LEDs based on InGaN near-ultraviolet-blue light chips.

[0099] Comparative Example 1 made some adjustments to the traditional "one-pot" preparation method and did not undergo a long aging process. The resulting phosphor had two emission peaks in the emission spectrum under 365nm light excitation, with the maximum peaks located at 407nm (blue-violet) and 515nm (green), respectively. The blue-violet peak was stronger, as shown in Figure 1. Figure 3 The results show that the Eu in the sample of Comparative Example 1 2+ NaBaB9O was also incorporated 15 The eight grid positions and the eight grid positions, and the main ones to enter are the eight grid positions.

[0100] Compared with the embodiment, the comparative example 2 does not undergo precursor synthesis according to the order of S1 and S2. Under 365nm light excitation, the comparative example sample has no emission visible to the naked eye.

[0101] Comparative Example 3, under 365nm light excitation, has two emission peaks in the emission spectrum, with the maximum peaks located at 405nm (blue-violet) and 515nm (green), of which the green peak is stronger. Figure 3 This result shows that the Eu in the sample of Comparative Example 3 2+ NaBaB9O was also incorporated 15 The eight grid positions and the eight grid positions.

[0102] 2.LED luminous performance

[0103] Commercially available blue phosphor BaMgAl 10 O 17 :Eu 2+ , commercial red phosphor K2SiF6:Mn 4+After adjusting the appropriate ratio and mixing with the green phosphor prepared in Example 1, the mixture was packaged with an InGaN near-ultraviolet chip (365nm) to prepare a warm white light LED. The emission spectrum of the packaged device at a driving current of 50mA is shown in FIG. Figure 4 The prepared white light LED has an average color coordinate of (0.389, 0.417), a correlated color temperature of 4045K, and a color rendering index of 93.55. These optical performance parameters indicate that the white light LED prepared by the present invention has a high color rendering index and relatively suitable color coordinates and correlated color temperature.

[0104] The above embodiments are preferred experimental methods of the present invention, but the implementation methods of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing rare earth-doped green phosphor, characterized in that: The following steps are involved: S1. Barium hydroxide, boric acid, europium trioxide and water are mixed to form a first mixture; S2. mixing a sodium source solution with the first mixture to form a second mixture, wherein the amount of sodium element in the sodium source solution is 0.95 to 1.05 times the difference between the amount of barium element in the barium hydroxide and the amount of europium element in the europium trioxide; the sodium source is sodium hydroxide or sodium borate; the sodium borate is selected from one of hydrated sodium tetraborate and anhydrous sodium tetraborate; S3. The second mixture is calcined in a reducing atmosphere, the calcination temperature is 750~800 ℃, the calcination time is 240~480 min, and the phosphor is obtained after cooling; in: When the sodium source is sodium hydroxide, the molar ratio of the elements barium, boron and europium in the barium hydroxide, boric acid and europium trioxide is Ba:B:Eu=1-1.05:9-9.5:0.005-0.1; or: When the sodium source is sodium borate, the molar ratio of the elements barium, boron and europium in the barium hydroxide, boric acid and europium trioxide is Ba:B:Eu=1-1.05:7-7.5:0.005-0.1; The chemical formula of the rare earth doped green phosphor is: Na 1-x BaB9O 15 :xEu 2+ , where 0.005≤x≤0.

1.

2. The preparation method according to claim 1, characterized in that When the sodium source is sodium hydroxide, the molar ratio of the elements barium, boron and europium in the barium hydroxide, boric acid and europium trioxide is Ba:B:Eu=1-1.05:9-9.5:0.01-0.

05.

3. The preparation method according to claim 1, characterized in that When the sodium source is sodium borate, the molar ratio of the elements barium, boron and europium in the barium hydroxide, boric acid and europium trioxide is Ba:B:Eu=1-1.05:7-7.5:0.01-0.

05.

4. The preparation method according to claim 1, characterized in that The barium hydroxide is selected from hydrated barium hydroxide or anhydrous barium hydroxide.

5. The preparation method according to claim 1, characterized in that The sodium hydroxide is selected from one of hydrated sodium hydroxide and anhydrous sodium hydroxide.

6. The preparation method according to claim 1, characterized in that The mass of the water in S1 is 2 to 3 times the total mass of the barium hydroxide, boric acid and europium trioxide.

7. The preparation method according to claim 1, characterized in that The mass of free water in the second mixture is 0 to 2 times the total mass of barium hydroxide, boric acid, europium trioxide and sodium hydroxide.

8. The preparation method according to claim 1, characterized in that The reducing atmosphere is a mixture of H2 and N2.

9. The preparation method according to claim 1, characterized in that The heating rate of the calcination is 5-10°C / min.

10. The preparation method according to claim 1, characterized in that The cooling rate is 1-3°C / min.

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