A kind of halogenonitride yellow phosphor and preparation method thereof

Abstract

The present invention provides a halogenonitride yellow phosphor, wherein the halogenonitride yellow phosphor has the structural formula La a M b Si c N d D e :xCe 3+ , where M is one or more of Ca, Sr, Ba, and Mg, D is one or more of F, Cl, and Br, and 1.5≤a≤3.5, 0.001≤b≤1.5, 4.5≤c≤6.5, 10≤d≤12, 0.001≤e≤3, and 0.001≤x≤0.2. The present invention improves the luminous efficiency and thermal quenching of nitride yellow phosphors by combining element substitutions, increasing the luminous efficiency by more than 5% and improving the thermal quenching of the phosphor at 200°C by more than 6%.

Description

Technical Field

[0001] The present invention belongs to the technical field of luminescent material preparation, and in particular relates to a halogenonitride yellow phosphor and a preparation method thereof. Background Art

[0002] Nitride phosphors are important components for achieving white light LEDs. For example, the nitride red phosphor CaAlSiN3:Eu is an essential luminescent material for achieving high color rendering white light LEDs. β-SiAlON:Eu green phosphor is currently the only optional narrow-band emission green phosphor for high color gamut LCD backlight sources.

[0003] In recent years, a large number of nitrides composed of elements with ternary or higher elements have been reported, especially silicon nitride-based multi-element nitride and nitrogen oxide phosphors. These phosphors emit light ranging from blue-green to red when excited by blue LEDs or near-ultraviolet LEDs. By combining blue LEDs or near-ultraviolet LEDs with these phosphors, light-emitting devices emitting white light can be constructed, which can be used in lighting or displays.

[0004] Patent document CN103254900B describes a nitride yellow phosphor with a structure of RSi6(N,O)11:Ce, where R = rare earth elements such as La, Gd, Lu, and Y. This yellow phosphor produces white light by mixing blue light from an LED with yellow light from the phosphor. This phosphor can be used for display applications. However, the luminous efficiency of this yellow phosphor is still insufficient, and it exhibits significant thermal quenching at 200°C. Summary of the Invention

[0005] The present invention aims to solve the deficiencies of the prior art and provides a halogenonitride yellow phosphor. The luminous efficiency and thermal quenching problem of the halogenonitride yellow phosphor are improved by combining element substitution.

[0006] The halogenonitride yellow phosphor of the present invention is prepared by reacting a divalent alkaline earth metal and a halogen element with the existing yellow phosphor La3Si6N 11 :Ce is transformed to improve the luminous efficiency of yellow phosphor by more than 5%.

[0007] The activator ions Ce and halogen ions in the halogenonitride yellow phosphor of the present invention have a stronger binding force, which makes the crystal field around the activator ions have a stronger binding force on the activator ions, thereby increasing the rigidity of the phosphor crystal and improving the luminescence performance. At the same time, the luminescence stability of the phosphor at high temperatures is significantly enhanced. The introduction of alkaline earth metals is to balance the charge imbalance caused by the replacement of nitrogen by halogen elements. Alkaline earth metal elements are generally optically inert and do not affect the luminescence behavior of the activator ions after introduction.

[0008] The present invention also provides a method for preparing the halonitride yellow phosphor. By combining an improved synthesis technology with the above-mentioned structural modification, the thermal quenching of the phosphor at 200° C. is improved by more than 6%.

[0009] The halogenonitride yellow phosphor of the present invention has the structural formula La a M b Si c N d D e :xCe 3+ ,

[0010] Wherein, M is one or more of Ca, Sr, Ba, and Mg, D is one or more of F, Cl, and Br, 1.5≤a≤3.5, 0.001≤b≤1.5, 4.5≤c≤6.5, 10≤d≤12, 0.001≤e≤3, and 0.001≤x≤0.2.

[0011] The halogenonitride phosphor is excited by a blue LED or a near-ultraviolet LED to emit yellow light with a wavelength of 550nm-560nm.

[0012] Furthermore, the molar amount of M is not less than 5‰ compared to La, and the molar amount of D is not less than 25‰ compared to N.

[0013] The two work synergistically, and the ratio of M and D ranges from M:D=(2±0.25):1.

[0014] Preparation method of the halogenonitride yellow phosphor of the present invention:

[0015] Step (1): LaN, M3N2, Si3N4, CeN and NH4D (or MD2) are weighed according to the stoichiometric ratio.

[0016] Step (2): Mix the above raw materials evenly, put them into a BN crucible, and cover it.

[0017] Step (3): Place the crucible in a carbon tube furnace and keep it at 1750-1900°C for 2-20 hours in a nitrogen atmosphere with a holding pressure of 0.5-10 MPa.

[0018] Step (4): crush the powder obtained in step (3) and pass it through a 200-300 mesh sieve, then put it into a BN crucible again, and keep it at 1800-2000℃ for 2-20h in a nitrogen-hydrogen mixed gas atmosphere with a holding pressure of 0.5-10MPa.

[0019] Step (5): Cooling to 1200°C at a cooling rate of less than 3°C / min.

[0020] Step (6): Crush the powder obtained in step 4, wash it with 5-20% nitric acid at a temperature of 70-85°C for 0.5-10 hours, dry it, and sieve it to obtain the target phosphor.

[0021] The nitrogen-hydrogen mixed atmosphere in step (4) has a hydrogen content of less than 10% to prevent excessive H content from causing a low nitrogen partial pressure in the mixed gas, thereby causing nitrogen removal from the raw materials during the synthesis process.

[0022] The halogenonitride yellow phosphor of the present invention improves the luminous efficiency of the yellow phosphor by more than 5%, and improves the thermal quenching of the phosphor at 200° C. by more than 6%. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Example 1 Excitation and emission spectra of halogenonitride yellow phosphor.

[0024] Figure 2 SEM morphology photograph of the halogenonitride yellow phosphor of Example 2. DETAILED DESCRIPTION Example 1

[0025] Weigh 44.34g LaN, 0.25g Ca3N2, 28.08g Si3N4, 0.77g CeN and 0.13g NH4Cl.

[0026] The raw materials were mixed evenly using a pot ball mill. The mixture was then placed in a BN crucible with an inner diameter of 50 mm and a height of 60 mm. The crucible was covered and placed in a carbon tube furnace. The crucible was then heated at 1850°C for 8 hours in a nitrogen atmosphere at a nitrogen pressure of 1 MPa. The resulting powder was then crushed and passed through a 200-mesh sieve. The crucible was then placed back into the BN crucible and heated at 1950°C for 10 hours in a nitrogen-hydrogen mixture (2% hydrogen) at a nitrogen pressure of 1.5 MPa. After the temperature was reduced to 1200°C at a rate of 2°C / min. The resulting powder was crushed, ball-milled, and then washed with 10% nitric acid for 2 hours at 80°C. The powder was then dried and sieved to yield the yellow phosphor.

[0027] The structural formula of the yellow phosphor obtained is La 2.9 Ca 0.05 Si6N 10.975 Cl 0.025 : 0.05Ce. The phosphor has a peak emission wavelength of 551nm and a quantum efficiency of 98.7%. Brightness maintenance at 200°C is 94.3%. Example 2

[0028] Weigh 42.81g LaN, 28.08g Si3N4, 1.23g CeN, 0.87g Sr3N2, and 0.38g SrF2

[0029] The raw materials were mixed uniformly using a pot ball mill. The mixture was then placed in a BN crucible with an inner diameter of 50 mm and a height of 60 mm. The crucible was covered and placed in a carbon tube furnace. The crucible was heated at 1800°C for 10 hours in a nitrogen atmosphere at a nitrogen pressure of 0.8 MPa. The resulting powder was then pulverized and passed through a 300-mesh sieve. The crucible was then placed back into the BN crucible and heated at 1920°C for 15 hours in a nitrogen-hydrogen mixture (5% hydrogen) at a nitrogen pressure of 1 MPa. After the temperature was lowered to 1200°C at a rate of 2.5°C / min. The resulting powder was pulverized, ball-milled, and then washed with 20% nitric acid for 1 hour at 70°C. The powder was then dried and sieved to obtain the yellow phosphor.

[0030] The structural formula of the yellow phosphor obtained is La 2.8 Sr 0.12 Si6N 10.94 F 0.06 : 0.08Ce. The phosphor has a peak emission wavelength of 555nm and a quantum efficiency of 98.5%. Brightness maintenance at 200°C is 95.1%. Example 3

[0031] Weigh 42.81g LaN, 28.08g Si3N4, 1.54g CeN, 0.25g Ca3N2, 0.48g Sr3N2, 0.13g NH4Cl, and 0.09g NH4F.

[0032] The raw materials were mixed uniformly using a pot ball mill. The mixture was then placed in a BN crucible with an inner diameter of 50 mm and a height of 60 mm. The crucible was covered and placed in a carbon tube furnace. The crucible was heated at 1860°C for 6 hours in a nitrogen atmosphere at a nitrogen pressure of 1.2 MPa. The resulting powder was then pulverized and passed through a 300-mesh sieve. The crucible was then placed back into the BN crucible and heated at 1930°C for 12 hours in a nitrogen-hydrogen mixture (5% hydrogen) at a nitrogen pressure of 1.5 MPa. After the temperature was reduced to 1200°C at a rate of 2.5°C / min. The resulting powder was pulverized, ball-milled, and then washed with 20% nitric acid for 1 hour at 70°C. The powder was then dried and sieved to obtain the yellow phosphor.

[0033] The structural formula of the yellow phosphor obtained is La 2.8 Sr 0.05 Ca 0.05 Si6N 10.95 F 0.025 Cl 0.025 : 0.1Ce. The phosphor has a peak emission wavelength of 558nm and a quantum efficiency of 98.8%. Brightness maintenance at 200°C is 95.4%. Comparative Example 1

[0034] Weigh 45.1g of LaN, 28.08g of Si3N4, and 0.77g of CeN and mix them thoroughly using a pot ball mill. The mixture is then placed into a 50mm inner diameter, 60mm high BN crucible, covered, and placed in a carbon tube furnace. Heat the crucible at 1950°C for 10 hours under a nitrogen atmosphere at a pressure of 1.5MPa. The resulting powder is pulverized and ball-milled, then washed with 10% nitric acid for 2 hours at 80°C. The mixture is then dried and sieved to yield a yellow phosphor.

[0035] The structural formula of the yellow phosphor obtained in Comparative Example 1 is La 2.95 Si6N 11 : 0.05Ce. The phosphor has a peak emission wavelength of 550nm and a quantum efficiency of 93.2%. Brightness maintenance at 200°C is 88.2%.

[0036] Performance test example

[0037] The spectrum and brightness were measured using a Farfair HASS-2000 spectrometer, the thermal quenching test was performed using a Farfair EX-1000 thermal quenching analyzer, and the aging test was performed using a Dongguan Weihuang Laboratory Equipment WHTH-800 LED aging analyzer.

[0038] Emission peak wavelength nm Quantum efficiency % Relative brightness% 200℃ brightness maintenance rate% Brightness maintenance rate after 1000h aging (current 60mA, temperature 85℃, humidity 85%) Example 1 551 98.7 100 94.3 98.8 Example 2 555 98.5 99.8 95.1 98.6 Example 3 558 98.8 100.5 95.4 98.5 Comparative Example 1 550 93.2 94.4 88.2 96.2

Claims

1. A halogenonitride yellow phosphor, characterized in that: Its structural formula is La a M b Si c N d D e :xCe 3+ , Wherein M is one or more of Ca, Sr, and Mg, D is one or more of F, Cl, and Br, 1.5≤a≤3.5, 0.001≤b≤1.5, 4.5≤c≤6.5, 10≤d<12, 0.001≤e<3, 0.001≤x≤0.2; The amount of M is not less than 5‰ of La in molar amount. The ratio range of M and D is M:D=(2±0.25):

1.

2. The halogenonitride yellow phosphor according to claim 1, characterized in that: The halogenonitride yellow phosphor is excited by a blue LED or a near-ultraviolet LED to emit yellow light with a wavelength of 550nm-560nm.

3. The method for preparing the halogenonitride yellow phosphor according to claim 1, wherein: The obtained material is obtained by uniformly mixing NH4D and / or MD2 with LaN, M3N2, Si3N4 and CeN and then sintering.

4. The method according to claim 3, characterized in that During sintering, a nitrogen-hydrogen mixed atmosphere is provided to provide a protective atmosphere and a reducing environment.

5. The method according to claim 4, characterized in that: The nitrogen-hydrogen mixed atmosphere has a hydrogen content of less than 10%.

6. The method according to claim 3 or 4, characterized in that: The specific steps are as follows: Step (1): weigh the raw materials according to the stoichiometric ratio; Step (2): Mix the above raw materials evenly and put them into a BN crucible, and cover it; Step (3): Place the crucible in a carbon tube furnace, and keep it at 1750-1900°C for 2-20 hours in a nitrogen atmosphere with a holding pressure of 0.5-10 MPa; Step (4): crush the powder obtained in step (3) and pass it through a 200-300 mesh sieve, then put it into a BN crucible again, and keep it at 1800-2000°C for 2-20 hours in a nitrogen-hydrogen mixed gas atmosphere with a holding pressure of 0.5-10 MPa; Step (5): cooling to 1200°C at a cooling rate of less than 3°C / min; Step (6): crush the powder obtained in step (5), wash it with 5-20% nitric acid at a temperature of 70-85°C for 0.5-10 hours, dry it and sieve it to obtain the target phosphor.

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