RU2553868C2 - Method for producing luminescent material for generating resulting white light in light emitting diodes - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention refers to methods for producing photoluminescent phosphors and can be used in producing white light emitting diodes. Mixture components are mixed, milled in a planetary mill at an acceleration of 20 G for at least 25 min. The prepared powder is annealed and ultrasonicated by shock cooling in an ultrasonic bath followed by washing and precision sieving at a particle size of 15-20 mcm. The produced luminescent material has a mean particle size of no more than 4 mcm, maximum luminescence band at λ=545-565 nm.

EFFECT: reducing the luminescent material process time and increasing the fluorescent brilliance.

4 ex

Description

A method of obtaining a luminescent material to create the resulting white light in LEDs.

FIELD OF THE INVENTION

The invention relates to methods for producing photoluminophors used to convert blue LED radiation into the yellow, yellow-green region of the spectrum to obtain the resulting white light, in particular, to a method for producing cerium-doped phosphor based on yttrium-aluminum garnet, which is used in two-component LED light sources .

State of the art

Known phosphor for light sources containing aluminum, yttrium, cerium, lutetium and oxygen in the following ratio: (Y _1-x Ce _x ) ₃ Al ₅ O ₁₂ and 5-60 wt. % in excess of 100% (Lu _1-y Ce _y ) ₂ O ₃ , where x = 0.005-0.1; y = 0.01-0.1 ("Phosphor for light sources", RF patent for the invention No. 2396302, publ. 08/10/2010). Known phosphor is obtained by colloid-chemical method. The invention provides the creation of a finely dispersed phosphor with the position of the maximum luminescence band at λ = 590 nm with a decrease in temperature and the duration of its synthesis. However, one of the obvious disadvantages of this invention is the high cost of lutetium oxide, the difficulty of obtaining colloidal rare earth oxide while maintaining high purity.

Known phosphor for light sources of the composition (CHINA GLAZE CO., LTD, Patent application number: US 2011254435, publ. 20.10.2011), designed to convert the radiation of blue LEDs in the yellow-orange region of the spectrum in order to obtain the resulting white light. A phosphor having the formula: (Rel-yBay) 3-x (Rg) 5O12: Ceh, where: Re is Y, Tb, Lu, Sc, La, Gd, Sm, or combinations thereof; Rg is Al, Ga, B, or combinations thereof; 0 <x <3, 0 <y <1.

This phosphor is prepared by a solid phase reaction using reagents containing Ba, such as BaSO ₄ , carbonates, such as BaCO ₃ , or halides, such as BaF ₂ . Reagents containing Y, Tb, Lu, Sc, La, Gd, Sm can be oxides, such as Y ₂ O ₃ , or nitrates, such as Tb (NO ₃ ). Reagents containing Al, Ga, or In may be oxides such as γ-Al ₂ O _3, Ga ₂ O ₃ or B ₂ O _3. Reagents containing Ce may be oxides, such as CeO ₂ . The described equivalent equivalent reagents are uniformly mixed and ground in a ball mill. The mixture is then heated in a high temperature oven. After sintering at a temperature of 1300 ° C to 1500 ° C for 8-16 hours in a reducing atmosphere (5% H ₂ and 95% N ₂ ), a phosphor is obtained.

A significant drawback of this phosphor is that the average particle size exceeds 10 microns, in addition, the use of ball mills for grinding requires about 6-20 hours for grinding and mixing the reagents.

Closest to the claimed method of obtaining a luminescent material for creating the resulting white light in LEDs is the method described in application EP N1710292 (CL 09K 11/64, 2006, see abstract, description, paragraphs 0003, 0004, 0028, 0029, 0109, 0117-0119, 0137-0141). A method of manufacturing a powdery fluorescent material comprises the steps of: 1) sintering an initial powder; 2) chemical treatment of the sintered powder with a solution of a mixture of acids, including hydrofluoric acid, sulfuric acid and water, 3) the stage of granulation of the wet powder, which is placed in a sieve of 40-200 μm in size, is subjected to vibration or shock to obtain aggregate complexes of small and large particles; 4) sintering after granulation, 5) suspension of the obtained powder in order to classify and remove fine particles. The essence of the suspension is to distribute the powder in the liquid and allow it to settle, as a result, small particles suspended in the liquid after 2 minutes after the liquid is stirred or subjected to vibration will not settle on the bottom of the glass, and this part can be decanted. The main essence of the patent is to classify the powder in a simple way by removing small particles that are less efficient.

From a comparative analysis of the claimed method with the known it follows that the common features for them are the following: mixing the components of the mixture, grinding it in a planetary mill, calcining the resulting powder and ultrasonic treatment.

The main disadvantage of this method is that particles of 30-40 microns are obtained, which leads to lower efficiency of the phosphor in LEDs, since at the same brightness of the phosphor, a luminescent composition with a smaller grain size gives a generally higher increase in intensity in LED .

Disclosure of invention

The objective of the invention is the creation of a finely dispersed phosphor with an average particle size of 4-5 microns, an increase in crystallinity and printed density, as well as an increase in the luminescence brightness compared to a finely crystalline analog, ground in ball mills using grinding balls.

The technical result is a decrease in the duration of the process of obtaining a luminescent material, an increase in crystallinity and printed density of the resulting phosphor and, as a result, an increase in the brightness of luminescence compared to a fine crystalline analog, crushed in ball mills using grinding balls.

The specified technical result is achieved in that the method for producing a luminescent material for creating the resulting white light in LEDs includes mixing the components of the mixture, grinding it in a planetary mill, calcining the obtained powder and ultrasonic treatment, and according to the invention, grinding in a planetary mill is carried out with an acceleration of 20 G for not less than 25 min, ultrasonic treatment is carried out after calcination by quenching in an ultrasonic bath followed by (washing), etc. do precision sieving through a sieve with a mesh size of 15-20 microns.

The proposed phosphor is prepared as follows.

Example 1

Oxides of yttrium, cerium in a molar ratio of 2.6-2.80: 0.005-0.2 are dissolved in nitric acid until completely dissolved with constant stirring. Next, aluminum nitrate is added to the resulting solution (molar ratio of yttrium oxide to aluminum 2.8: 5.0-5.1). To the resulting solution, 25% aqueous ammonia was added dropwise with constant stirring to pH-10. The reaction results in the formation of metal hydroxides of yttrium, cerium and aluminum and there is some excess of ammonia and ammonium nitrate as a by-product. The resulting hydroxide mixture is washed with deionized water to a pH of 8-9, then filtered on a Buchner funnel, placed in a porcelain bowl (crucible) and annealed at a temperature of 600-800 ° C for 3-4 hours. Then the powder is placed in an alundum crucible and calcined in air at a temperature of 1500-1570 ° C for 4-8 hours. The resulting intermediate is sieved using multi-frequency analyzers through a 15 micron sieve, compacted using a planetary mill with an acceleration of 20G for 5 minutes without using grinding balls and sieved through a 15 micron sieve, poured into an alundum crucible, then calcined in formgas medium for 4-8 hours at a temperature of 1500-1600 ° C. The finished phosphor is discharged from the elevator furnace at a temperature of 1400 ° C, the bead is thrown into a glass of water for 2-3 seconds after being removed from the crucible, which is located in an ultrasonic water bath at a water temperature of 25 ° C and an ultrasound frequency of 10 to 25 kHz. Suddenly cooled to room temperature, the phosphor is washed with deionized water and sieved through a 20 micron sieve. The average particle size of the phosphor is 12 microns. The brightness of the luminescence (at λexc = 450-460 nm) is 98% relative to the brightness of the luminescence of the coarse-grained analog.

Example 2

Oxides of yttrium, cerium, gallium and gadolinium in a molar ratio of 2.85-2.95: 0.0032-0.13: 0.001-0.01: 0.0011-0.011 are dissolved in nitric acid until completely dissolved with constant stirring. Gallium oxides are dissolved in nitric acid in a microwave at high pressure. Next, aluminum nitrate (molar ratio of yttrium oxide to aluminum 2.9: 5.0-5.1) is added to the resulting solution, which is pre-filtered. To the resulting solution, 25% aqueous ammonia was added dropwise with constant stirring to pH-9-10. The reaction results in the formation of metal hydroxides of yttrium, cerium, gadolinium, gallium and aluminum. The resulting intermediate has some excess ammonia and ammonium nitrate as a by-product. The resulting hydroxide mixture is washed with deionized water to a pH of 8-9, then filtered on a Buchner funnel, placed in a porcelain bowl (crucible) and annealed at a temperature of 600-800 ° C for 3-4 hours. Then the powder is placed in an alundum crucible and calcined in air at a temperature of 1500-1570 ° C for 4-8 hours. The resulting intermediate is sieved using multi-frequency analyzers through a 15 micron sieve, compacted using a planetary mill with an acceleration of 20G for 15 minutes without using grinding balls and sieved through a 15 micron sieve, poured into an alundum crucible, then calcined in formargaz medium for 4-6 hours at a temperature of 1500-1600 ° C. The phosphor is discharged from the elevator furnace at a temperature of 1400 ° C, then the beetle is thrown into a glass of water for 2-3 seconds after being removed from the crucible, which is located in an ultrasonic water bath at a water temperature of 25 ° C and an ultrasound frequency of 10 to 25 kHz. Suddenly cooled to room temperature, the phosphor is washed with deionized water and sieved through a 20 micron sieve. The average particle size of the phosphor is 9 microns. The brightness of the glow (at λexc = 450-460 nm) is 99-100% relative to the brightness of the glow of a coarse-grained analog.

Example 3

Oxides of yttrium, cerium in a molar ratio of 2.6-2.80: 0.005-0.2 are dissolved in nitric acid until completely dissolved with constant stirring. Next, aluminum nitrate is added to the resulting solution (molar ratio of yttrium oxide to aluminum 2.8: 5.0-5.1). To the resulting solution, 25% aqueous ammonia was added dropwise with constant stirring to pH-10. The reaction results in the formation of metal hydroxides of yttrium, cerium and aluminum and there is some excess of ammonia and ammonium nitrate as a by-product. The resulting hydroxide mixture is washed with deionized water to a pH of 8-9, then filtered on a Buchner funnel, placed in a porcelain bowl (crucible) and annealed at a temperature of 600-800 ° C for 3-4 hours. Then the powder is placed in an alundum crucible and calcined in air at a temperature of 1500-1570 ° C for 4-8 hours. The resulting intermediate is sieved using multi-frequency analyzers through a 15 micron sieve, compacted using a planetary mill with an acceleration of 20G for 25 minutes without using grinding balls, and sifted through a 15 micron sieve, poured into an alundum crucible, then calcined in formgas medium for 4- 8 hours at a temperature of 1500-1600 ° C. The finished phosphor is discharged from the elevator furnace at a temperature of 1400 ° C, the bead is thrown into a glass of water for 2-3 seconds after being removed from the crucible, which is located in an ultrasonic water bath at a water temperature of 25 ° C and an ultrasound frequency of 10 to 25 kHz. Suddenly cooled to room temperature, the phosphor is washed with deionized water and sieved through a 20 micron sieve. The average particle size of the phosphor is 4-5 microns. The brightness of the luminescence (at λexc = 450-460 nm) is 98% relative to the brightness of the luminescence of the coarse-grained analog.

Example 4

Oxides of yttrium, cerium in a molar ratio of 2.6-2.80: 0.005-0.2 are dissolved in nitric acid until completely dissolved with constant stirring. Next, aluminum nitrate is added to the resulting solution (molar ratio of yttrium oxide to aluminum 2.8: 5.0-5.1). To the resulting solution, 25% aqueous ammonia was added dropwise with constant stirring to pH-10. The reaction results in the formation of metal hydroxides of yttrium, cerium and aluminum and there is some excess of ammonia and ammonium nitrate as a by-product. The resulting hydroxide mixture is washed with deionized water to a pH of 8-9, then filtered on a Buchner funnel, placed in a porcelain bowl (crucible) and annealed at a temperature of 600-800 ° C for 3-4 hours. Then the powder is placed in an alundum crucible and calcined in air at a temperature of 1500-1570 ° C for 4-8 hours. The resulting intermediate is sieved using multi-frequency analyzers through a 15 micron sieve, compacted using a planetary mill with an acceleration of 20G for 35 minutes without using grinding balls and sifted through a 15 micron sieve, poured into an alundum crucible, then calcined in formargaz medium for 4-8 hours at a temperature of 1500-1600 ° C. The finished phosphor is discharged from the elevator furnace at a temperature of 1400 ° C, the bead is thrown into a glass of water for 2-3 seconds after being removed from the crucible, which is located in an ultrasonic water bath at a water temperature of 25 ° C and an ultrasound frequency of 10 to 25 kHz. Suddenly cooled to room temperature, the phosphor is washed with deionized water and sieved through a 20 micron sieve. The average particle size of the phosphor is 1-2 microns. The brightness of the glow (at λexc = 450-460 nm) is 70% relative to the brightness of the glow of the coarse-grained analog.

Therefore, the use of centrifugal acceleration 20G for at least 25 minutes contributes to the production of a yellow phosphor with a luminosity of 98% relative to the brightness of a coarse-crystalline analog with an average particle size of 4-5 microns, which is optimal in terms of the ratio of high brightness and the minimum average particle size of the phosphor for Applications in modern LEDs.

Claims (1)

A method of obtaining a luminescent material to create the resulting white light in LEDs, including mixing the components of the mixture, grinding it in a planetary mill, calcining the obtained powder and ultrasonic treatment, characterized in that grinding in a planetary mill is carried out with an acceleration of 20 G for at least 25 minutes, the ultrasonic treatment is carried out after calcination by quenching in an ultrasonic bath, followed by washing and precision sifting through a sieve with a mesh size of 15-20 microns.