CN107312538B

CN107312538B - Synthetic method of high-nitrogen-content high-brightness nitrogen oxide fluorescent powder

Info

Publication number: CN107312538B
Application number: CN201710576444.3A
Authority: CN
Inventors: 张琳; 李万元; 鲁路
Original assignee: Beijing Nakamura Yuji Science And Technology Co ltd; Xi'an Hongyu Photoelectric Technology Co ltd; Beijing Yuji Science and Technology Co Ltd
Current assignee: Beijing Nakamura Yuji Science And Technology Co ltd; Xi'an Hongyu Photoelectric Technology Co ltd; Beijing Yuji Science and Technology Co Ltd
Priority date: 2017-07-14
Filing date: 2017-07-14
Publication date: 2020-05-22
Anticipated expiration: 2037-07-14
Also published as: CN107312538A

Abstract

The invention discloses a high-nitrogen-content high-brightness nitrogen oxide fluorescent powder Eu_xM_aSi_bAl_cO_dN_eBelonging to the technical field of luminescent materials. The high-brightness nitrogen oxide fluorescent powder with high nitrogen content can be obtained by adding a europium element raw material in a mode of preparing an alloy from metal europium and silicon powder, simultaneously carrying out a silicon element nitriding step, and combining an annealing treatment or acid pickling treatment process after high-temperature sintering. The invention can obtain high brightness Eu without ultra-high pressure treatment process²⁺The doped nitrogen oxide fluorescent powder with high nitrogen content reduces the installation and maintenance cost of equipment; the powder with larger crystal grains can be obtained, the brightness of the powder is improved, the synthesis period of the powder with the large crystal grains is shortened, and the production cost is reduced; through the surface optimization of the powder, the annealing treatment and the acid washing impurity removal process for reducing the internal defects of the crystal and releasing the internal stress of the crystal, the high-brightness and high-purity nitrogen oxide fluorescent powder is obtained, and the quality of the powder is improved.

Description

Synthetic method of high-nitrogen-content high-brightness nitrogen oxide fluorescent powder

Technical Field

The invention relates to the technical field of luminescent materials, in particular to a synthesis method of high-nitrogen-content high-brightness nitrogen oxide fluorescent powder.

Background

White light LEDs based on the solid state light principle have many advantages of high efficiency, high brightness, long service life, small size, safety, no pollution and the like, and have gradually replaced the traditional illumination tools such as incandescent lamps, fluorescent lamps and the like in life. The light source is widely applied to illumination, backlight sources, traffic signals, decorations, instruments, automobiles and the like.

With the rapid development of the white light LED and fluorescent powder field in recent years, the mainstream application of the white light LED light source is generally developed towards two main directions: firstly, high brightness in the illumination directionThe white light LED with color rendering index, the white light LED with high brightness and wide color gamut in the display backlight direction and the white light LED with high color rendering index are obtained by combining a blue light chip and red and green fluorescent powder or combining an ultraviolet chip and red, green and blue fluorescent powder, and the method for realizing the white light LED with wide color gamut also comprises two methods, namely, the blue light chip is packaged by green powder and red powder with high color purity, and the white light is obtained by exciting the red, green and blue fluorescent powder with high color purity by using the ultraviolet chip²⁺Green powder and KSF Mn⁴⁺The NSTC range of the red powder can reach more than 95 percent.

The green fluorescent powder of the LED applied at present comprises silicate, aluminate, sulfide and oxynitride. Silicate (BaSr)₂SiO₄:Eu²⁺And Ca₃Sc₂Si₃O₁₂:Ce³⁺The fluorescence spectrum of (2) is wide, and the fluorescent color purity of the powder is not high. Aluminate SrAl₂O₄:Eu²⁺The emission spectrum is also wide, the half-peak width is about 80nm, and in addition, the fluorescent powder has long afterglow characteristic and is not suitable for the field of backlight display. Sulfide SrGa₂S₄:Eu²⁺And ZnS: Cu²⁺:Al³⁺The color purity of the fluorescent powder is high, but the stability is poor, the fluorescent powder is easy to decompose when meeting water, and the application and popularization of the fluorescent powder are greatly limited. Nitrogen oxide green fluorescent powder Si_3-zAl_zO_zN_4-z:Eu²⁺(β-sialon:Eu²⁺) The fluorescence peak position of the fluorescent powder is adjustable within the range of 520-560 nm, the half-peak width of the fluorescence spectrum changes along with the change of a z value and is between 45-80 nm, the color separation purity of a low z value group is high, and the fluorescent powder has excellent chemical stability and high thermal quenching temperature, so that the fluorescent powder is widely concerned and is increasingly applied to backlight display devices. Eu (Eu)²⁺Doped N-oxides of the M-sialon series M_xSi_3-x-y-zAl_y+zO_zN_4-2x/3-y/3-zThe (M is alkaline earth metal cation) has excellent chemical stability and good fluorescence property, and has good application prospect in illumination and display. Such as Eu²⁺Doped Sr₃Si₁₃Al₃O₂N₂₁(M ═ Sr, x ═ 9/19, y ═ 3/19, z ═ 6/19) and Eu²⁺Doped Sr₁₄Si₆₁Al₁₃O₇N₉₉(M is Sr, x is 21/44, y is 9/44, z is 21/88) is adjustable in blue-green fluorescent light color, Eu is adjustable in green-green fluorescent light color²⁺Doped Sr₂Si₇Al₃ON₁₃The color of the orange-red fluorescent light is adjustable (M is Sr, x is 1/2, y is 1/2, and z is 1/4), and the red fluorescent light has good application prospect in improving the display index of a white light LED excited by ultraviolet or blue light. And Eu²⁺Doped SrSi₉Al₁₉ON₃₁Under the excitation of ultraviolet light, (M) is 3/29, y is 54/29, and z is 3/29), the emission peak is a wide fluorescence peak in the blue light region.

The β -sialon and M-sialon series nitrogen oxides have high nitrogen content, silicon source and nitrogen source need to be introduced into the preparation process by silicon nitride, which is stable and has low reaction activity, and can form phase at high temperature, and needs nitrogen atmosphere protection, and when the nitrogen partial pressure is low, the main phase is easy to decompose at high temperature, so that the high-temperature high-pressure solid phase method is generally adopted to prepare the fluorescent powder_3-zAl_zO_zN_4-z:Eu²⁺Luminescence center Eu²⁺In the octahedral channel center of Si-Al-O-N solid solution, the doping mode is different from the lattice occupation of most luminescent centers of fluorescent powder, and most of the fluorescent powder has luminescent centers substituting for metal ions in the host lattice β -sialon²⁺This unique lattice occupation of the mid-luminescence center makes the luminescence center Eu²⁺Is low, thereby leading to the fluorescence brightness of the fluorescent powderIn addition, Eu is generally adopted for introducing a luminescence center Eu³⁺At high temperature N₂Under an atmosphere, Eu³⁺Eu not completely converted into green light²⁺This also weakens β -sialon Eu²⁺The β -sialon Eu synthesized by the high-temperature high-pressure method²⁺The brightness can be improved only by a series of complicated subsequent treatment processes, for example, a synthesis method for synthesizing beta-sialon is introduced in patent CN102596852A, and ultrahigh pressure HIP treatment of 70-150 Mpa is adopted, so that the installation and maintenance costs of equipment are greatly increased by the processes.

Therefore, a simple, effective and low-equipment-requirement synthesis method is needed for the nitrogen oxides with high nitrogen content and high temperature and high pressure required in the preparation process.

Disclosure of Invention

In order to overcome the defects of the prior art and technology, the invention discloses a synthesis method of high-nitrogen-content high-brightness nitrogen oxide fluorescent powder. Aims to provide a synthesis method which is easy to control so as to obtain the nitrogen oxide fluorescent powder with high fluorescence intensity.

The invention relates to a method for synthesizing high-nitrogen-content high-brightness nitrogen oxide fluorescent powder, which is to mix Eu²⁺Is dissolved in the crystal phase of nitrogen oxide with high nitrogen content. In the process of introducing the luminescence center, the europium source exists in the form of low-valence rare earth europium all the time, so that the europium source (such as Eu) with high valence is avoided₂O₃) Eu introduced into luminescence center²⁺Resulting in Eu²⁺The amount of solid solution is not high. The method is to use metal europium and active silicon powder to prepare silicon-europium alloy which is easy to break and stable, and use the silicon-europium alloy as a europium source and perform high-temperature and high-pressure N₂In the silicon-europium alloy, silicon introduced forms a nitrogen oxide network tetrahedron (Si, Al) (O, N)₄And europium is oxidized to form Eu²⁺Thereby increasing the effective luminescence center Eu²⁺The solid solution amount further improves the fluorescence intensity of the fluorescent powder. On the other hand, by adjusting the host crystalSelection of grid materials and adjustment of the synthesis process can promote growth of fluorescent crystal grains toward a grain morphology favorable for fluorescence, for example, β -sialon Eu, which is easily formed into long columnar or needle shape during firing²⁺The powder with larger grain size and smaller length-diameter ratio can be obtained, so that the absorption of the powder to exciting light is increased, and the brightness of the powder is increased. Thirdly, through a post-treatment process, including but not limited to one treatment way of annealing treatment and acid washing treatment, the internal stress of the crystal is released, the crystal defects are reduced, and the purity of the fluorescent crystal phase is improved, so that the fluorescent intensity of the powder is greatly improved.

The specific adoption scheme of the invention is as follows:

rare earth Eu²⁺A synthetic method of high-brightness nitrogen oxide fluorescent powder doped with high nitrogen content, and Eu²⁺The chemical composition general formula of the high-brightness nitrogen oxide doped with high nitrogen content is Eu_δM_aSi_bAl_cO_dN_eWherein M is an alkaline earth metal cation, and a is not less than 0; b, c, d, e is more than 0, and e/(d + e) is more than or equal to 0.5; when a is 0, 0.0001 < delta.is less than or equal to 0.05, when a is>When 0, delta/(delta + a) is more than 0.001 and less than or equal to 0.15, and the synthesis method comprises the following steps:

(1) silicon europium alloy EuSi_mThe preparation process comprises the following steps: processing europium metal and metal silicon powder at the high temperature of 800-1400 ℃ under a protective atmosphere to obtain EuSi_mCrushing the alloy block into powder, wherein m is more than or equal to 0.3 and less than or equal to 1.5;

(2) a raw material nitriding process: according to the chemical composition of the nitrogen oxide, carrying out nitridation treatment on a certain amount of silicon powder, or the silicon powder and an aluminum-containing oxide or nitride at 1200-1700 ℃ under a pressurized nitrogen atmosphere to obtain a silicon nitride block or an aluminum-containing silicon nitride block, and crushing the block into powder;

(3) a high-temperature firing process; according to Eu²⁺Doping the chemical composition of the nitrogen oxide, and mixing the silicon nitride powder obtained in the step (2) or the silicon nitride powder containing aluminum with aluminum nitride or aluminum oxide, and EuSi obtained in the step (1)_mThe alloy powder and the necessary alkaline earth metal M compound are evenly mixed, and then the mixed raw materials are heated to 1700 to 2300 DEG CFiring at a high temperature of 0.3-9.8 MPa in a nitrogen atmosphere, and crushing the fired blocks into powder to obtain Eu²⁺Doping nitrogen oxide fluorescent powder;

(4) and a post-treatment process: annealing and/or pickling treatment of the fluorescent powder; the annealing treatment refers to a step of heating and calcining the powder obtained in the step (3) at a temperature lower than the firing temperature, and the pickling treatment refers to a step of pickling the annealed powder in an acid solution.

The time of the high-temperature treatment in the step (1) is more than 20 minutes, and the protective atmosphere comprises one or more mixed gases of nitrogen atmosphere, rare gas atmosphere and hydrogen atmosphere.

The temperature of the high-temperature treatment in the step (1) is 1000-1200 ℃; the high-temperature treatment time is more than 2 hours; the protective atmosphere is an argon atmosphere.

The nitrogen pressure in the step (2) is 0.1-10 Mpa, the nitriding treatment time is not less than 1h, and the temperature rise rate is not higher than 10 ℃/min at the temperature of over 1000 ℃ in the temperature rise process.

The raw materials of the nitriding process in the step (2) are silicon powder and aluminum-containing oxide, and the nitrogen pressure is 0.8-1.0 Mpa; in the temperature rise process, the temperature rise rate is not higher than 1-2 ℃/min above 1000 ℃; the particle size of the broken powder particles is not more than 300 microns.

The high-temperature sintering treatment time in the step (3) is not less than 30 minutes; the pressure of the pressurized nitrogen is not lower than 0.3 Mpa.

The pressure of the pressurized nitrogen in the step (3) is 0.8-1.0 Mpa, and the medium particle size of the crushed powder after high-temperature sintering is not more than 150 microns.

The alkaline earth metal M compound is M oxide, M nitride, M carbonate or M nitrate.

The annealing treatment temperature in the step (4) is at least 200 ℃ lower than the firing temperature, and the annealing treatment time is not less than 4 hours; the acid washing treatment time in the step (4) is not less than 10 minutes.

The Eu being²⁺The high-brightness nitrogen oxide doped with high nitrogen content is M-sialon Eu²⁺Chemical composition is (EuM)_xSi_3-x-y-zAl_y+zO_zN_4-2x/3-y/3-zM is an alkaline earth metal ion, and the ratio of the composition (Si, Al)/(O, N) is 0.70 to 0.95.

The nitrogen oxides (EuM)_xSi_3-x-y-zAl_y+zO_zN_4-2x/3-y/3-zThe post-treatment process comprises acid washing, washing the powder with clear water to remove acid solution, and drying to obtain M-sialon Eu²⁺A fluorescent powder; wherein the acid solution comprises hydrofluoric acid, nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid or their mixture.

The acid solution is hydrochloric acid, the concentration of the hydrochloric acid is 0.5-20 wt%, and the acid washing time is not less than 10 minutes.

The Eu being²⁺The high-brightness nitrogen oxide doped with high nitrogen content is β -sialon Eu²⁺The chemical composition is as follows: eu (Eu)_sSi_3-mAl_mO_mN_4-mWherein m is more than 0 and less than or equal to 2, and the ratio of the components (Si, Al)/(O, N) is 0.70-0.78.

The nitrogen oxide is β -sialon Eu²⁺The post-treatment process of the powder comprises annealing treatment and acid washing treatment, wherein the annealing treatment refers to the annealing treatment of the powder obtained in the step (3) at the temperature of 1000-1600 ℃ under vacuum or protective atmosphere, the time of the high-temperature annealing treatment is not less than 2 hours, the protective atmosphere comprises inert atmosphere, nitrogen, hydrogen, hydrocarbon gas or mixed gas of the inert atmosphere, the acid washed powder is washed by clear water to remove acid liquor, and the powder is dried to obtain β -sialon, Eu²⁺A fluorescent powder; wherein the acid solution comprises hydrofluoric acid, nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid or their mixture.

The acid solution is mixed acid of 40 wt% of hydrofluoric acid and 68 wt% of nitric acid, the volume ratio of the mixed acid to the nitric acid is 2:1, and the acid washing time is not less than 10 minutes.

The protective atmosphere in the annealing is a mixed atmosphere consisting of 10% of hydrogen and 90% of argon.

Eu is generally adopted for introducing the luminescent center Eu of the fluorescent powder₂O₃Eu under nitrogen atmosphere³⁺Difficult to completely reduce to useful Eu²⁺，Eu³⁺Not only the existence of Eu is reduced²⁺And a reduced europium concentrationAnd quenching the europium content. The invention adopts an alloying method, uses a reduced luminescence center Eu, and prevents Eu from moving to Eu under an inert atmosphere³⁺Convert and increase Eu²⁺The solid solution amount of (3) and the brightness of the powder are improved. On the other hand, silicon powder and partial aluminum-containing compound are used in the raw materials, so that the raw material nitriding process is increased, the silicon nitride powder is not directly used as a synthetic raw material, the grain growth of the synthesized powder is larger, the crystal length-diameter ratio is small, and the brightness of the powder is further increased. Thirdly, through the post-treatment process such as annealing or acid washing, the internal stress of the crystal can be released, the crystal defects can be reduced, and the purity of the fluorescent crystal phase can be improved, so that the fluorescent intensity of the powder can be greatly improved.

The specific preparation method of the fluorescent powder comprises the following steps:

(1) the preparation process of the silicon-europium alloy comprises the following steps: processing metal europium and metal silicon powder at the temperature of 800-1400 ℃ in a protective atmosphere to obtain a product with a nominal composition of EuSi_mAnd (3) alloy blocks. Mixing EuSi_mThe alloy blocks are crushed into powder. Wherein m is more than or equal to 0.3 and less than or equal to 1.5; the temperature of the high-temperature treatment is preferably 1150 ℃; the treatment time is not less than 20 minutes, preferably 2 hours; the protective atmosphere includes a nitrogen atmosphere, an argon atmosphere or other rare gas atmosphere, a hydrogen atmosphere, and a mixed gas of the above gases, preferably an argon atmosphere.

(2) A raw material nitriding step; according to the chemical composition of the nitrogen oxide, a certain amount of silicon powder, or the silicon powder and aluminum-containing oxide or nitride are subjected to nitriding treatment at 1200-1700 ℃ in a pressurized nitrogen atmosphere to obtain a silicon nitride block or aluminum-containing silicon nitride block, and the block is crushed into powder. The nitrogen pressure is 0.1-10 Mpa, preferably 0.9 Mpa; in the temperature rise process, the temperature rise rate is not higher than 10 ℃/min when the temperature rises to more than 1000 ℃; the treatment time is not less than 1 h; the particle size of the broken powder particles is not more than 300 microns. The silicon powder is used for direct nitridation, if the temperature is not high, the silicon powder is slowly nitrided and has long nitridation time, if the temperature is increased, the silicon powder is easy to sinter, the nitrided part of the surface layer in a non-flowing nitrogen atmosphere hinders the internal nitridation, the sintering is required to be crushed and nitrided for multiple times, the process complexity is increased, and the sintering period is prolonged. If a certain amount of aluminum-containing oxide or nitride is added into the nitrided silicon powder, the aluminum oxide or nitride is a high-melting-point compound, the serious agglomeration of silicon nitride can be prevented, and the nitriding rate can be improved. However, when an excessive amount of aluminum-containing nitride is added, AlN polytype is likely to be produced in the presence of aluminum-containing oxide, which is disadvantageous in the subsequent synthesis of powder. Therefore, the process preferably adds only the aluminum-containing oxide.

(3) A high-temperature firing process; mixing the obtained silicon nitride powder or silicon nitride powder containing aluminum with aluminum nitride or oxide, EuSi, according to the chemical composition of nitrogen oxide_mThe alloy powder and other necessary alkaline earth metal compounds are uniformly mixed. Then, the mixed raw materials are sintered at high temperature under the pressurized nitrogen atmosphere at the temperature of 1700-2300 ℃, and the sintered blocks are crushed into powder to obtain Eu_δM_aSi_bAl_cO_dN_eNitrogen oxide fluorescent powder. Wherein M is an alkaline earth metal cation, and a is not less than 0; b, c, d, e is more than 0, and e/(d + e) is more than or equal to 0.5. When a is 0, 0.0001 < delta.is less than or equal to 0.05, when a is>0 is 0.001 < delta/(delta + a) is less than or equal to 0.15, particularly β -sialon is Eu²⁺The chemical composition of (A) is as follows: eu (Eu)_sSi_3-mAl_mO_mN_4-mWherein m is more than 0 and less than or equal to 2, and the ratio of the components (Si, Al)/(O, N) is 0.70-0.78. In particular, for M-sialon Eu²⁺Chemical composition is (EuM)_xSi_3-x-y-zAl_y+zO_zN_4-2x/3-y/3-z(M is an alkaline earth metal ion) in a ratio of (Si, Al)/(O, N) of 0.70 to 0.95. The high-temperature sintering treatment time is not less than 30 minutes; the pressure of the pressurized nitrogen is not less than 0.3MPa, and the requirement on equipment is strict in consideration of the increase of the pressure of the pressurized nitrogen, and the pressure is preferably 0.9 MPa. The crushed powder has a median particle size of not more than 150 μm.

(4) And a post-treatment process: including but not limited to one of annealing and pickling. The annealing treatment refers to a step of heating and calcining the powder obtained in the step (3) at a temperature of at least 200 ℃ lower than the firing temperature, and the pickling treatment refers to a step of immersing and pickling the annealed powder in an acid solution. Some small amount of impurities are generated in the high-temperature sintering process in the step (3) difficultly, and meanwhile, defects are generated on the surface and inside of the crystal in the crushing process, so that the internal stress of the crystal is increased, and the integrity of the small amount of crystal is damaged. The influence of the adverse factors can be reduced by annealing treatment or acid washing treatment, and the brightness of the powder is improved.

For β -sialon Eu²⁺The post-treatment process of the powder comprises annealing treatment and acid pickling treatment, wherein the annealing treatment is β -sialon Eu²⁺Annealing the powder at 1200-1600 ℃ in vacuum or protective atmosphere, wherein the time of high-temperature annealing is not less than 2 hours, the protective atmosphere comprises argon or other inert atmosphere, nitrogen, hydrogen, hydrocarbon gas or the mixture of the nitrogen, the hydrogen and the argon, preferably the mixed atmosphere containing the hydrogen and the argon, the powder is optimized after annealing, the brightness of the powder is greatly improved, acid washing is to soak the powder after annealing in acid liquor for a period of time, then clean water is used for removing the acid liquor, and drying is carried out to obtain β -sialon, Eu²⁺A fluorescent powder; wherein the acid solution comprises hydrofluoric acid, nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid or their mixture. The acid solution is preferably a mixed acid of 40 wt% hydrofluoric acid and 68 wt% nitric acid in a volume ratio of 2:1, and the acid washing time is preferably not less than 10 minutes.

For Eu²⁺Doped N-oxides of the M-sialon series M_xSi_3-x-y-zAl_y+zO_zN_4-2x/3-y/3-zThe post-treatment process of (M is alkaline earth metal cation) powder is acid pickling treatment, and the powder obtained by high-temperature sintering process is soaked in acid liquor for a period of time, then cleaned with clear water to remove acid liquor, and dried to obtain M-sialon²⁺(M is an alkaline earth metal cation) fluorescent powder. Wherein the acid solution comprises hydrofluoric acid, nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid or their mixture. Preferably, the acid solution is hydrochloric acid, the concentration is preferably 0.5-20 wt%, and the acid washing time is preferably not less than 10 minutes.

Compared with the prior art, the invention has the following specific benefits:

firstly, the invention synthesizes silicon-europium alloy powder stable in air, and introduces low-valence europium source into luminescence center Eu²⁺Can be obtained without ultra-high pressure treatment processObtaining the high brightness Eu²⁺The doped nitrogen oxide fluorescent powder with high nitrogen content reduces the installation and maintenance cost of the equipment.

Secondly, the aluminum-containing silicon nitride raw material is obtained through a nitriding process, so that powder with larger crystal grains can be obtained, the brightness of the powder is improved, the synthesis period of the powder with the large crystal grains is shortened, and the production cost is reduced.

Thirdly, annealing treatment and acid washing impurity removal processes for reducing internal defects of crystals and releasing internal stress of the crystals are performed by optimizing the surface of the powder, so that the nitrogen oxide fluorescent powder with high brightness and high powder purity is obtained, and the quality of the powder is improved.

Drawings

FIG. 1 shows the synthesis of Eu in example 1²⁺Doped β -sialon (Eu)_sSi_3-mAl_mO_mN_4-m) Excitation and emission spectra of green phosphor. Where s is 0.01 and m is 0.05, 0.1, 0.2, 0.5, 0.8, 1.5, respectively.

FIG. 2 shows β -sialon (Eu) obtained by high-temperature baking and crushing in example 2_sSi_3-mAl_mO_mN_4-mAnd m is 0.1) a scanning electron microscope display of the powder.

FIG. 3 shows β -sialon (Eu) obtained at different process steps in example 2_sSi_3-mAl_mO_mN_4-mM is 0.1) fluorescence spectrum of the powder under 460nm excitation light, wherein curve 1 is the fluorescence spectrum of the powder obtained after high-temperature firing, curve 2 is the fluorescence spectrum of the powder subjected to annealing treatment, and curve 3 is the fluorescence spectrum of the powder subjected to acid cleaning treatment.

FIG. 4 shows β -sialon (Eu) obtained by high-temperature baking and crushing in example 3_sSi_3-mAl_mO_mN_4-mAnd m is 0.1) a scanning electron microscope display of the powder.

FIG. 5 shows examples 2, 3 and

the fluorescence spectrum of the powder obtained in reference example 1, wherein Curve 1 is β -sialon (Eu) after acid washing treatment in example 2_sSi_3-mAl_mO_mN_4-mM is 0.1) powderCurve 2 shows β -sialon (Eu) after acid washing treatment in example 3_sSi_3-mAl_mO_mN_4-mM is 0.1) the fluorescence spectrum of the powder, curve 3 is

Reference example 1 β -sialon (Eu) after acid washing treatment_sSi_3-mAl_mO_mN_4-mM 0.1) fluorescence spectrum of the powder

FIG. 6 shows the Eu synthesis in example 4²⁺Doped nitrogen oxide Eu_xSr_3-xSi₁₃Al₃O₂N₂₁Emission spectrum of green phosphor. Wherein x is 0.01, 0.02, 0.05, 0.08, 0.10, 0.15 and 0.20 respectively.

FIG. 7 shows fluorescence spectra of powders obtained in examples 5 and 6 and reference example 2, wherein Curve 1 shows Eu after high temperature baking in example 5_0.08Sr_2.92Si₁₃Al₃O₂N₂₁Fluorescence spectrum of the powder, wherein Curve 2 is Eu after acid cleaning treatment in example 5_0.08Sr_2.92Si₁₃Al₃O₂N₂₁Fluorescence spectrum of the powder, curve 3 is Eu after acid cleaning treatment in example 6_0.08Sr_2.92Si₁₃Al₃O₂N₂₁Fluorescent spectrum of powder, curve 4 being Eu after acid washing treatment in reference example 2_0.08Sr_2.92Si₁₃Al₃O₂N₂₁Fluorescence spectrum of powder

Detailed Description

The present invention will be described in further detail with reference to examples.

Example 1

① preparation of silicon-europium alloy, burying 10g metal europium block in excessive silicon powder, processing at 1150 deg.C for 4h in argon atmosphere in alumina crucible to obtain 11.2250g silicon-europium alloy block, crushing and sieving with 300m nylon sieve, according to the mass change before and after firing, determining that the nominal chemical composition of silicon-europium alloy is Eu₃Si₂。

② nitridation of raw material, 200g silicon powder is put into a cylinder boron nitride crucible (phi 90mm is multiplied by 110mm), and nitridation treatment is carried out for 8h at 1500 ℃ under the nitrogen pressure atmosphere of 0.9Mpa, the heating speed is controlled as follows, the temperature is increased from room temperature to 1000 ℃ at 10 ℃/min, the temperature is increased from 1000 ℃ to 1200 ℃ at 2 ℃/min, the temperature is increased from 1200 ℃ to 1350 ℃ at 1 ℃/min, the temperature is kept at 1350 ℃ for 4h, the temperature is increased from 1350 ℃ to 1500 ℃ at 1 ℃/min, the obtained product is a silicon nitride block with certain strength, and the silicon nitride block is ground and crushed and is sieved by a 150-mesh nylon sieve.

③ high-temperature sintering, namely uniformly mixing the obtained silicon nitride powder with aluminum nitride of 92.52 percent and 1.41 percent, alumina of 4.90 percent and silicon-europium alloy powder of 1.17 percent in mass ratio, and according to β -sialon, Eu²⁺Chemical composition Eu_sSi_3-mAl_mO_mN_4-mIn the formula, s is 0.01, m is 0.2, the sieved mixed raw material is filled into a cylindrical boron nitride crucible (phi 90mm multiplied by 110mm), the mixture is sintered for 8h at 1900 ℃ under the nitrogen pressure atmosphere of 0.9Mpa, the obtained block is ground and crushed, and is sieved and classified by a 120-mesh nylon sieve, hard particles which are difficult to crush are removed, and powder under the sieve is collected, so that β -sialon, Eu, is obtained²⁺A fluorescent powder.

④ post-treatment

Annealing treatment, namely, carrying out annealing treatment on the obtained β -sialon Eu²⁺The phosphor was charged into an alumina ark (40 mm. times.40 mm. times.200 mm) and treated at 1350 ℃ for 8 hours in a tube furnace in an atmosphere of a 10% hydrogen-argon mixture. After the argon-hydrogen reduction atmosphere treatment, the surface of the crystal damaged by the breakage is optimized, the internal stress of the crystal is released, and the defects are reduced, so that the fluorescence intensity of the powder is greatly improved.

Acid cleaning treatment, namely β -sialon Eu subjected to high-temperature and high-pressure sintering and annealing²⁺The powder still contains a certain amount of impurities, mainly including silicon powder which is not completely nitrided and reacted, AlN polytypes generated during the firing process, and the impurities need to be removed by annealing β -sialon Eu²⁺100g of powder is put into 300ml of hydrofluoric acid (40 wt%) and 150ml of nitric acid (68 wt%), stirred for 2 hours, washed by distilled water to remove acid liquor, and dried to obtain β -sialon Eu with further improved brightness²⁺And (3) fluorescent powder.

Adjusting the mixingThe raw materials are mixed according to the proportion, the high-temperature and high-pressure sintering temperature is correspondingly adjusted, β -sialon Eu with different z values can be obtained²⁺And (3) powder. The different z values are different from each other in the color of the phosphor. As shown in Table 1, the raw material ratios and firing temperatures of different z values, and the fluorescence peak wavelength and full half peak width of the obtained powder under 460nm excitation light. FIG. 1 shows excitation and emission spectra for different values of z.

TABLE 1 different values of z β -sialon Eu²⁺Raw material mass ratio, firing temperature and fluorescence parameters

Example 2

① preparation of silicon europium alloy Synthesis of Eu as the europium source according to the Process for preparing a silicon europium alloy in example 1₃Si₂And (3) powder.

② nitridation of raw material, 200g silicon powder and 8.71g alumina are mixed uniformly, in a cylinder boron nitride crucible (phi 90mm x 110mm), in the atmosphere of 0.9Mpa nitrogen pressure, nitridation treatment is carried out at 1500 ℃ for 8h, the heating speed is controlled as follows, the temperature is raised from room temperature to 1000 ℃ at 10 ℃/min, from 1000 ℃ to 1200 ℃ at 2 ℃/min, from 1200 ℃ to 1350 ℃ at 1 ℃/min, from 1350 ℃ to 1500 ℃ at 1 ℃/min, the product is silicon nitride block containing alumina, which is ground and crushed, and sieved by a 150 mesh nylon sieve.

③ high-temperature sintering, namely uniformly mixing 98.36 mass percent of silicon nitride powder containing alumina, 0.47 mass percent of aluminum nitride and 1.17 mass percent of silicon-europium alloy powder according to the proportion of β -sialon to Eu²⁺Chemical composition Eu_sSi_3-mAl_mO_mN_4-mIn the formula, s is 0.01, and m is 0.1. The sieved mixed raw materials were charged into a cylindrical boron nitride crucible (phi 90 mm. times.110 mm), and were fired at 1920 ℃ for 8 hours under a nitrogen pressure atmosphere of 0.9 MPa. The obtained block was ground and crushed, and sieved through a 120 mesh nylon sieve to remove hard particles which were difficult to crush. The crystal obtained by the method has larger size and smaller length-diameter ratio, and the shape is powder fluorescenceEnhanced advantageous morphology. In the nitriding process, the generated silicon nitride is wrapped by partial alumina, and under the conditions of high temperature and high pressure, the silicon nitride is dissolved inwards by the firstly melted alumina, so that the crystal orientation growth is slowed down, and the crystal length and diameter are smaller. Fig. 2 is a scanning electron micrograph of the obtained powder. FIG. 3, Curve 1 shows the fluorescence spectrum of the powder under 460nm blue light excitation.

④ post-treatment

Annealing treatment: the powder was annealed as in example 1, and the fluorescence intensity of the powder was greatly enhanced after annealing. The fluorescence spectrum of the powder after this step under the excitation of 460nm blue light is shown as curve 2 in FIG. 3.

Acid pickling treatment: the powder was acid-washed as in example 1, and after acid-washing, the fluorescence intensity of the powder was further improved, as shown by the fluorescence spectrum of the powder after the procedure represented by curve 3 in FIG. 3 under the excitation of 460nm blue light.

Table 2 shows the absorption rate, internal quantum efficiency and external quantum efficiency of the powder under the excitation of 460nm blue light obtained from the powder through different process treatment stages. Wherein, the data is obtained by a Hitachi F7000 fluorescence spectrometer and a quantum efficiency test system thereof.

TABLE 2 Eu-sialon-different Process procedures β²⁺Absorption rate, internal quantum efficiency, external quantum efficiency and relative fluorescence intensity of powder

Example 3

① preparation of silicon europium alloy Eu as the europium source was prepared according to the silicon europium alloy preparation Process in example 1₃Si₂And (3) powder.

② nitridation of raw material silicon nitride powder obtained by nitriding silicon powder was obtained according to the raw material nitriding process in example 1.

③ high-temperature sintering, namely uniformly mixing the obtained silicon nitride powder with 95.79 percent and 0.47 percent of aluminum nitride, 2.57 percent of aluminum oxide and 1.17 percent of silicon-europium alloy powder according to the mass ratio of β -sialon to Eu chemical composition_sSi_3-mAl_mO_mN_4-mIn the formula, s is 0.01, and m is 0.1. The sieved mixed raw materials were charged into a cylindrical boron nitride crucible (phi 90 mm. times.110 mm), and were fired at 1920 ℃ for 8 hours under a nitrogen pressure atmosphere of 0.9 MPa. The resulting mass was ground and crushed and sieved through a 120 mesh nylon sieve to remove hard particles that were difficult to crush. Fig. 4 is a scanning electron micrograph of the powder. Comparing the morphology of the powder in fig. 2, it can be seen that the powder obtained by the process of example 2 is relatively dispersed, the crystal size is large, and the microscopic morphology of the powder is good.

④ post-treatment

Annealing treatment: the powder was annealed as in example 1.

Acid pickling treatment: the phosphor obtained by acid washing with annealing treatment as in example 1 had a fluorescence spectrum of the powder as shown by curve 2 in FIG. 5. Comparing the fluorescence spectrum curve 1 of the powder subjected to the acid washing treatment in example 2, it can be seen that the fluorescence intensity of the powder obtained by the process of example 2 is higher.

Reference example 1

① nitridation of raw material, 200g silicon powder and 7.51g alumina are mixed uniformly, in a cylinder boron nitride crucible (phi 90mm x 110mm), in the atmosphere of 0.9Mpa nitrogen pressure, nitridation treatment is carried out at 1500 ℃ for 8h, the heating speed is controlled as follows, the temperature is raised to 1000 ℃ at 10 ℃/min, 1000 ℃ to 1200 ℃ at 2 ℃/min, 1200 ℃ to 1350 ℃ at 1 ℃/min, the temperature is kept at 1350 ℃ for 4h, 1350 ℃ to 1500 ℃ at 1 ℃/min, the obtained product is a silicon nitride block containing alumina, which is ground and crushed, and sieved by a 150-mesh nylon sieve.

② high-temperature sintering, namely uniformly mixing 97.51 mass percent of silicon nitride powder containing aluminum oxide, 0.75 mass percent of aluminum nitride and 1.75 mass percent of europium oxide powder, and sieving the mixture by a 120-mesh nylon sieve for controlling the granularity, wherein Eu is calculated according to β -sialon²⁺General chemical formula, Eu_sSi_3-mAl_mO_mN_4-mIn the formula, s is 0.01, and m is 0.1. The sieved mixed raw material was charged into a cylindrical boron nitride crucible (phi 90 mm. times.110 mm), and fired at 1920 ℃ under a nitrogen pressure atmosphere of 0.9MPaThe treatment time is 8 h. The resulting mass was ground and crushed and sieved through a 120 mesh nylon sieve to remove hard particles that were difficult to crush.

③ post-treatment

Annealing treatment: the powder was annealed as in example 1

Acid pickling treatment: the phosphor obtained by acid washing with annealing treatment as in example 1 showed a fluorescence spectrum of the phosphor as shown by curve 3 in FIG. 5. Comparing the spectra can result in comparison with the use of Eu₂O₃As the europium source, a silicon-europium alloy Eu is used₃Si₂The powder effect is better, β -sialon (Eu) obtained by different processes in the third table 3_sSi_3-mAl_mO_mN_4-mM ═ 0.1) absorptivity, internal quantum efficiency, and external quantum efficiency of the powder, EuSi_mEu as europium source effect ratio₂O₃Good results are obtained.

Table 3, example 2 and its comparative reference samples show the absorptance, internal quantum efficiency, external quantum efficiency and relative fluorescence intensity

Example 4

① preparation of silicon europium alloy Eu as the europium source was prepared according to the procedure for preparing a silicon europium alloy of example 1₃Si₂And (3) powder.

② nitridation of raw material silicon nitride powder with a particle size of less than 100 microns is obtained from silicon powder nitrided according to the raw material nitridation process of example 1.

③ high-temperature sintering, namely uniformly mixing the obtained silicon nitride powder with 58.68 percent and 6.60 percent of aluminum nitride, 6.56 percent of aluminum oxide, 0.16 percent of silicon-europium alloy powder and 28.00 percent of strontium nitride powder according to the mass ratio, and according to the nitrogen oxide Eu_xSr_3- _xSi₁₃Al₃O₂N₂₁The Eu content x in the formula is 0.08. The sieved mixed raw materials were charged into a cylindrical boron nitride crucible (phi 90 mm. times.110 mm), and calcined at 1800 ℃ for 8 hours under a nitrogen pressure atmosphere of 0.9 MPa.The obtained block was ground and crushed, and sieved through a 120 mesh nylon sieve to remove hard particles which were difficult to crush. Collecting the undersize powder to obtain Eu²⁺Doped oxynitride Sr₃Si₁₃Al₃O₂N₂₁And (4) green fluorescent powder.

④ post-treatment, i.e. pickling treatment, of nitrogen oxides Sr obtained by high-temperature firing₃Si₁₃Al₃O₂N₂₁100g of phosphor powder was put into 300ml of a hydrochloric acid solution containing 8% by mass of hydrogen chloride, and stirred for 2 hours. Then washed with distilled water to remove the acid solution. After drying, the nitrogen oxide Sr with further improved brightness can be obtained₃Si₁₃Al₃O₂N₂₁And (3) fluorescent powder.

Adjusting the luminescence center Eu of the mixed raw materials²⁺The composition proportion can obtain Sr with different fluorescent light colors₃Si₁₃Al₃O₂N₂₁And (3) fluorescent powder. Eu for different values of Eu content x as in Table 4_xSr_3-xSi₁₃Al₃O₂N₂₁The raw materials are proportioned, and the obtained powder is processed at 1800 ℃ for 8h and ground to obtain the fluorescence peak wavelength and full half-peak width of the powder under 460nm excitation light. FIG. 6 shows Sr with different Eu contents₃Si₁₃Al₃O₂N₂₁Fluorescence spectrum of the phosphor.

TABLE 4 Nitrogen oxides Eu for different values of x_xSr_3-xSi₁₃Al₃O₂N₂₁Raw material mass ratio and fluorescence parameter of

Example 5

② nitridation of raw material, 200g silicon powder and 16.65g alumina are mixed uniformly, in a cylinder boron nitride crucible (phi 90mm x 110mm), in the atmosphere of 0.9Mpa nitrogen pressure, nitridation treatment is carried out at 1500 ℃ for 8h, the heating speed is controlled as follows, the temperature is raised to 1000 ℃ at 10 ℃/min, 1000 ℃ to 1200 ℃ at 2 ℃/min, 1200 ℃ to 1350 ℃ at 1 ℃/min, the temperature is kept at 1350 ℃ for 4h, 1350 ℃ to 1500 ℃ at 1 ℃/min, the obtained product is a silicon nitride block containing alumina, which is ground and crushed, and sieved by a 150-mesh nylon sieve.

③ high-temperature sintering, namely uniformly mixing the obtained silicon nitride powder containing the alumina with 61.99 percent and 6.46 percent of aluminum nitride, 3.48 percent of alumina, 1.29 percent of silicon-europium alloy powder and 26.78 percent of strontium nitride powder according to the mass ratio, Eu is a nitrogen oxide_xSr_3-xSi₁₃Al₃O₂N₂₁The Eu content x in the formula is 0.08. The sieved mixed raw materials were charged into a cylindrical boron nitride crucible (phi 90 mm. times.110 mm), and were fired at 1800 ℃ for 8 hours under a nitrogen pressure atmosphere of 0.9 MPa. The obtained block was ground and crushed, and sieved through a 120 mesh nylon sieve to remove hard particles which were difficult to crush. Collecting the undersize powder to obtain Eu²⁺Doped oxynitride Sr₃Si₁₃Al₃O₂N₂₁And (4) green fluorescent powder.

④ Curve 1 shows the fluorescence spectrum of the powder under 460nm blue light excitation.

After-treatment, the powder was acid-washed as in example 4, and after acid-washing, the fluorescence intensity of the powder was further improved, e.g.

And the middle curve 2 is the fluorescence spectrum of the powder after the post-treatment under the excitation of 460nm blue light.

Table 2 shows the absorption rate, internal quantum efficiency and external quantum efficiency of the powder under the excitation of 460nm blue light obtained from the powder through different process treatment stages.

TABLE 5 different process stages Sr_2.92Eu_0.08Si₁₃Al₃O₂N₂₁Absorption, internal and external quantum efficiency and relative fluorescence intensity of fluorescent powder

Example 6

③ high-temperature sintering, namely uniformly mixing the obtained silicon nitride powder with 59.20 percent and 6.47 percent of aluminum nitride, 6.44 percent of aluminum oxide, 0.81 percent of silicon-europium alloy powder and 27.09 percent of strontium nitride powder according to the mass ratio, and Eu is a nitrogen oxide_xSr_3- _xSi₁₃Al₃O₂N₂₁The Eu content x in the formula is 0.08. The sieved mixed raw materials were charged into a cylindrical boron nitride crucible (phi 90 mm. times.110 mm), and were fired at 1800 ℃ for 8 hours under a nitrogen pressure atmosphere of 0.9 MPa. The resulting mass was ground and crushed and sieved through a 120 mesh nylon sieve to remove hard particles that were difficult to crush. Collecting the undersize powder to obtain Eu²⁺Doped oxynitride Sr₃Si₁₃Al₃O₂N₂₁And (4) green fluorescent powder.

④ post-treatment, the powder was acid-washed as in example 4, and the fluorescence intensity of the powder was further improved after acid-washing, as shown by curve 3 in FIG. 7, which is the fluorescence spectrum of the post-treated powder under the excitation of 460nm blue light.

Reference example 2

① nitridation of raw material aluminum-containing silicon nitride powder with a particle size of less than 100 microns, obtained by nitridation of silicon powder and aluminum oxide, was obtained according to the raw material nitridation process of example 5.

② high-temperature sintering, namely uniformly mixing the obtained silicon nitride powder containing the alumina with 62.24 percent and 6.65 percent of the aluminum nitride, 3.22 percent of the alumina, 0.83 percent of europium oxide powder and 27.05 percent of strontium nitride powder according to the mass ratio, Eu is a nitrogen oxide_xSr_3-xSi₁₃Al₃O₂N₂₁The Eu content x in the formula is 0.08. The sieved mixed raw materials are put into a cylindrical boron nitride crucible (phi 90mm multiplied by 110mm),the mixture is sintered for 8 hours at 1800 ℃ under the nitrogen pressure atmosphere of 0.9 Mpa. The resulting mass was ground and crushed and sieved through a 120 mesh nylon sieve to remove hard particles that were difficult to crush. Collecting the undersize powder to obtain Eu²⁺Doped oxynitride Sr₃Si₁₃Al₃O₂N₂₁And (4) green fluorescent powder.

③ post-treatment, the powder is acid-washed as in example 4, the fluorescence intensity of the powder is further improved after acid-washing, as shown in FIG. 7, curve 4 is the fluorescence spectrum of the powder after post-treatment under the excitation of 460nm blue light, Table 6 is Eu obtained by different process steps of example 5, example 6 and reference example 2_0.08Sr_2.92Si₁₃Al₃O₂N₂₁The absorption rate, internal quantum efficiency, external quantum efficiency and relative fluorescence intensity of the phosphor.

Table 6, example 4 and its comparative reference samples had absorptance, internal quantum, external quantum efficiency and relative fluorescence intensity

Claims

1. Rare earth Eu²⁺A synthetic method of high-brightness nitrogen oxide fluorescent powder doped with high nitrogen content, and Eu²⁺The chemical composition general formula of the high-brightness nitrogen oxide doped with high nitrogen content is Eu_δM_aSi_bAl_cO_dN_eWherein M is an alkaline earth metal cation, and a is not less than 0; b, c, d, e is more than 0, and e/(d + e) is more than or equal to 0.5; when a is 0, 0.0001 < delta.is less than or equal to 0.05, when a is>When 0, delta/(delta + a) is more than 0.001 and less than or equal to 0.15, and the synthesis method comprises the following steps:

(3) a high-temperature firing process; according to Eu²⁺Doping the chemical composition of the nitrogen oxide, and mixing the silicon nitride powder obtained in the step (2) or the silicon nitride powder containing aluminum with aluminum nitride or aluminum oxide, and EuSi obtained in the step (1)_mUniformly mixing alloy powder and necessary alkaline earth metal M compound, then sintering the mixed raw materials at 1700-2300 ℃ and 0.3-9.8 MPa nitrogen atmosphere at high temperature, and crushing the sintered blocks into powder to obtain Eu²⁺Doping nitrogen oxide fluorescent powder;

2. The synthesis method according to claim 1, wherein the time of the high-temperature treatment in the step (1) is more than 20 minutes, and the protective atmosphere comprises one or more mixed gases of a nitrogen atmosphere, a rare gas atmosphere and a hydrogen atmosphere.

3. The synthesis method according to claim 2, wherein the temperature of the high-temperature treatment in the step (1) is 1000-1200 ℃; the high-temperature treatment time is more than 2 hours; the protective atmosphere is an argon atmosphere.

4. The synthesis method according to claim 1, wherein the nitrogen pressure in the step (2) is 0.1-10 Mpa, the nitriding treatment time is not less than 1h, and the temperature rise rate is not higher than 10 ℃/min at a temperature rise rate of more than 1000 ℃.

5. The synthesis method according to claim 4, wherein the raw materials of the nitriding step in the step (2) are silicon powder and aluminum-containing oxide, and the nitrogen pressure is 0.8-1.0 MPa; in the temperature rise process, the temperature rise rate is not higher than 1-2 ℃/min above 1000 ℃; the particle size of the broken powder particles is not more than 300 microns.

6. The synthesis method according to claim 1, wherein the high-temperature sintering treatment time in the step (3) is not less than 30 minutes; the pressure of the pressurized nitrogen is not lower than 0.3 Mpa.

7. The synthesis method according to claim 6, wherein the pressure of the pressurized nitrogen in the step (3) is 0.8-1.0 MPa, and the medium particle size of the crushed powder after high-temperature sintering is not more than 150 microns.

8. The synthesis method according to claim 1, wherein the alkaline earth metal M compound is M oxide, M nitride, M carbonate or M nitrate.

9. The synthesis method according to claim 1, wherein in the step (4), the annealing temperature is at least 200 ℃ lower than the firing temperature, and the annealing time is not less than 4 hours; the acid washing treatment time in the step (4) is not less than 10 minutes.

10. The method of claim 1, wherein the Eu is selected from the group consisting of²⁺The high-brightness nitrogen oxide doped with high nitrogen content is M-sialon Eu²⁺Chemical composition is (EuM)_xSi_3-x-y-zAl_y+zO_zN_4-2x/3-y/3-zM is an alkaline earth metal ion, and the ratio of the composition (Si, Al)/(O, N) is 0.70 to 0.95.

11. The method of synthesizing of claim 10, said nitrogen oxide (EuM)_xSi_3-x-y-zAl_y+zO_zN_4-2x/3-y/3-zThe post-treatment process comprises acid washing, washing the powder with clear water to remove acid solution, and drying to obtain M-sialon Eu²⁺A fluorescent powder; wherein the acid solution comprises hydrofluoric acid, nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid or their mixture.

12. The synthesis method according to claim 11, wherein the acid solution is hydrochloric acid, the concentration of the hydrochloric acid is 0.5-20 wt%, and the acid washing time is not less than 10 minutes.

13. The method of claim 1, wherein the Eu is selected from the group consisting of²⁺The high-brightness nitrogen oxide doped with high nitrogen content is β -sialon Eu²⁺The chemical composition is as follows: eu (Eu)_sSi_3-mAl_mO_mN_4-mWherein m is more than 0 and less than or equal to 2, and the ratio of the components (Si, Al)/(O, N) is 0.70-0.78.

14. The method of claim 13, wherein the nitrogen oxide is β -sialon Eu²⁺The post-treatment process of the powder comprises annealing treatment and acid washing treatment, wherein the annealing treatment refers to the annealing treatment of the powder obtained in the step (3) at the temperature of 1000-1600 ℃ under vacuum or protective atmosphere, the time of the high-temperature annealing treatment is not less than 2 hours, the protective atmosphere comprises inert atmosphere, nitrogen, hydrogen, hydrocarbon gas or mixed gas of the inert atmosphere, the acid washed powder is washed by clear water to remove acid liquor, and the powder is dried to obtain β -sialon, Eu²⁺A fluorescent powder; wherein the acid solution comprises hydrofluoric acid, nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid or their mixture.

15. The synthesis method of claim 14, wherein the acid solution is a mixed acid of 40 wt% hydrofluoric acid and 68 wt% nitric acid in a volume ratio of 2:1, and the acid washing time is not less than 10 minutes.

16. The method of claim 15, wherein the protective atmosphere in the annealing is a mixed atmosphere comprising 10% hydrogen and 90% argon.