CN100339460C - Preparation method of silicate luminous body for converting blue light to white light - Google Patents

Abstract

The present invention provides an aerosol preparation method for silicate fluophors converting and synthesizing blue light into white light, which belongs to the technical field of photoelectric materials. The method is characterized in that silicon dioxide particles in a nanometer dimension are used as pre-bury crystal seed, and the silicon dioxide particles are peptized by using weak acid and added with a small amount of polyvinyl alcohol; the silicon dioxide particles and a compound of strontium and europium are prepared into uniform solution according to a metering proportion and then atomized to evaporate water in liquid drops in the process of flight, and thus, the spherical dried gel particles with uniformly distributed components are formed; reduction thermal decomposition is carried out on the gel particles, and then high-purity spherical strontium silicate fluophors adulterated with europium with uniformly distributed components can be obtained. The method combines the advantages of a liquid phase method, a sol-gel method and a spraying thermal decomposition method; the fluophors are solid spheres of which the size is a plurality of microns to scores of nanometers, ball milling of the fluophors is not needed, and the method is suitable for mass production; the fluophors convert blue light into orange light and then synthesize the orange light into white light.

Description

Preparation method of silicate phosphor for blue light conversion and synthesis of white light

【Technical field】

The invention belongs to the technical field of optoelectronic materials, and in particular provides a method for preparing an aerosol of a silicate phosphor doped with europium to convert blue light into white light.

【Background technique】

The white light diode (LED) in the existing solid-state lighting technology is formed by mixing the yellow fluorescence of the cerium-doped yttrium aluminum garnet (YAG, Y ₃ Al ₅ O ₁₂ :Ce ³⁺ ) phosphor with the blue light of the LED to form white light. The color changes with the change of the driving voltage and the thickness of the phosphor coating, the color reproduction is poor, and the color rendering index is low. YAG is excited by blue light (~465nm) to produce orange light (~560nm) to synthesize white light. Eu ²⁺ , Tb ³⁺ and Mn ²⁺ doped alkaline earth metal silicate matrix phosphor is an important technical alternative.

Solid phase synthesis is still the traditional method for preparing luminescent materials. For example, mix BaCO ₃ , SrCO ₃ , CaCO ₃ , MgO, SiO ₂ and Eu ₂ O ₃ , add flux NH ₄ Cl, and ball mill in isopropanol environment After 48 hours, volatilize the isopropanol in the air, carry out granulation, and pre-fire in a muffle furnace at 600°C for 4 hours, then transfer to a tube furnace and burn for several hours in a reducing atmosphere at 1200-1400°C. After washing with water to remove the solvent, re-fire at 1300°C for 3 hours (Control of spectral properties of strontium-alkaline earth-silicate-europium phosphors for LEDapplications, J of the Electrochem.Soc., 152(5)G382-G385, 2005) . This method has a series of limitations such as uneven composition, high firing temperature, and impurities in the product.

The spray-pyrolysis technology using soluble salt (usually the nitrate of each component in the phosphor) solution has been developed in the luminescent material preparation technology. The main disadvantage is that when the water evaporates quickly, the atomized droplets and the subsequent burning When finished, the luminescent particles are easily damaged and difficult to form a spherical shape.

【Content of invention】

The object of the present invention is to provide an aerosol preparation method of a silicate phosphor that converts blue light into white light. The invention adopts an airgel technology pre-embedded with nano-scale silicon dioxide particles, which can not only mix the raw material components evenly, but also make the phase purity, size and shape of the final phosphor easily controlled.

The invention discloses an aerosol preparation method of a silicate phosphor that converts blue light into white light, and is characterized in that silicon dioxide particles are used as a phosphor matrix, peptized with a weak acid, and a dispersant is added to combine with strontium and europium. The soluble salts of these compounds are formulated into a uniform solution and then atomized to form spherical xerogel particles; the particles are subjected to reduction thermal decomposition reaction to obtain strontium silicate phosphor doped with europium.

The method of the present invention is first formulated into a silica gel solution, then atomized into xerogel particles, and finally fired once to obtain a high-purity spherical europium-doped strontium silicate phosphor with uniform component distribution, which has several advantages compared with the prior art. Features: 1) Cheap nano-silica is used not only as the silicon source of the product, but also as the center of xerogel and particle crystallization to prevent or reduce the generation of empty shell phosphors; 2) The raw material components are at the nano, atomic, and molecular scale levels 3) The firing temperature of the phosphor is lowered; 4) The size of the phosphor particles is submicron or tens of nanometers, and the previous ball milling process is no longer needed; 5) The thermal and chemical stability of the prepared phosphor is better than that of the existing YAG is high, and the cost is lower, which is suitable for large-scale production. The phosphor converts blue light into orange-yellow light, and finally synthesizes white light.

【Detailed ways】

The method for preparing the aerosol of the silicate phosphor that converts blue light into white light according to the present invention uses nanoscale silicon dioxide particles as pre-embedded crystal seeds, peptizes with weak acid, and adds a small amount of dispersant, which can be combined with strontium and europium. The dissolved salt is formulated into a uniform solution according to the metering ratio and then atomized, so that the water in the droplet evaporates during the flight to form spherical xerogel particles with uniform distribution of components. Reductive thermal decomposition reaction is carried out on the particles to obtain strontium silicate phosphor doped with europium. in:

The composition of the phosphor matrix is Sr ₂ SiO ₄ . The silicon source of the fluorescent body is nanoscale silicon dioxide with a purity of 99.9-99.99% (weight percent) and a size of 5-40 nanometers. Prepare solution with distilled water, control silicon dioxide: water = 1: 20-40, pH = 2-4 according to weight ratio, and make peptization. The strontium in the phosphor component adopts water-soluble nitrate or acetate, the purity of the salt is ≥99.99% (percentage weight), and is added to the silica sol according to the stoichiometric ratio. Add the compound of europium and strontium to the silica sol, the compound of europium and strontium adopts water-soluble nitrate or acetate, the purity is more than 99.99% (percent weight), and the quantity is strontium: europium=1: 0.01 ~0.05 (atomic moles). The dispersant added to the silica sol is solid polyvinyl alcohol or solid alkyl trimethyl, and the amount is 0.1-5% of the total weight of the sol. Then use the sol air atomization method to atomize the doped silica colloid at a compressed air temperature of 110°C-250°C, a dry air volume of 100-300m ³ /h, and a material flow of 1-2L/h to obtain a xerogel particles. Finally, the obtained xerogel particles are fired at a high temperature in a weak reducing atmosphere at a temperature of 1000°C to 1400°C for 2-4 hours. The reducing atmosphere of firing can be reduced by N ₂ +H ₂ , activated carbon reduction, or ammonia decomposition. One of gas or gas.

The following examples are to further illustrate the process characteristics of the present invention without limiting the present invention.

Example 1

According to silicon dioxide: water (weight ratio) = 1:20, add _SiO2 with a size of 10 nanometers into distilled water, adjust pH=2 with a small amount of nitric acid, and then add theoretical amount of _SiO2 according to the formula of _Sr2SiO4 Strontium nitrate, add europium nitrate by strontium: europium (atomic moles)=1: 0.01, then add polyvinyl alcohol in the sol, the polyvinyl alcohol that adds is 0.1% of sol gross weight, carries out mechanical stirring to become sol, sol static Leave it for 1 hour; set the air atomization parameters as follows: inlet temperature 110°C, dry air volume 100m ³ /h, material flow 2L/h, to obtain xerogel particles; N ₂ +5% H ₂ (volume ratio) mixed gas was fired at 1000° C. for 2 hours to obtain a phosphor with a particle size of 6 microns and a spherical shape.

Example 2

According to silicon dioxide: water (weight ratio) = 1: 30, add SiO ₂ with a size of 20 nanometers into distilled water, adjust pH=3 with a small amount of nitric acid, and then add theoretical amount of SiO according to the formula of Sr ₂ SiO ₄ Strontium nitrate, add europium nitrate by strontium: europium (atomic moles)=1: 0.03, then add polyvinyl alcohol in sol, the polyvinyl alcohol of adding is 0.5% of sol gross weight, carries out mechanical stirring and becomes sol, The sol was left to stand for 2 hours; the air atomization parameters were set as follows: inlet temperature 150°C, dry air volume 200m ³ /h, material flow 2L/h, to obtain xerogel particles; reduction with activated carbon, in a high-temperature lifting furnace at 1200°C After firing for 3 hours, the fluorescent body was obtained, the particle size of which was 3 microns, and it was spherical.

Example 3

According to silicon dioxide: water (weight ratio) = 1: 40, add SiO ₂ with a size of 40 nanometers into distilled water, adjust pH=2.5 with a small amount of nitric acid, and then add theoretical amount of SiO according to the formula of Sr ₂ SiO ₄ Strontium nitrate, add europium nitrate by strontium: europium (atomic moles)=1: 0.04, then add polyvinyl alcohol in the sol, the polyvinyl alcohol that adds is 0.8% of sol gross weight, carry out mechanical stirring and become sol, sol static Leave it for 3 hours; set the air atomization parameters as follows: inlet temperature 200°C, dry air volume 300m ³ /h, material flow 2L/h, to obtain xerogel particles; N ₂ +5% H ₂ (volume ratio) mixed gas was fired at 1300° C. for 2 hours to obtain a phosphor with a spherical particle size of 1 micron.

Claims (11)

1. A preparation method of a silicate phosphor that converts blue light into white light, is characterized in that silicon dioxide particles are used as the phosphor substrate, peptized with nitric acid, pH=2 to 4 is controlled, and a dispersant is added, and Soluble salts of strontium and europium are formulated into a homogeneous solution and then atomized to form spherical xerogel particles; the particles are subjected to reduction thermal decomposition reaction to obtain strontium silicate phosphor doped with europium. 2. The preparation method according to claim 1, characterized in that said phosphor matrix is composed of Sr ₂ SiO ₄ . 3. According to the preparation method of aerosol according to claim 2, it is characterized in that said phosphor matrix adopts nano silicon dioxide, the purity is 99.9-99.99% by weight percent, and the particle size is 5-40 nanometers. 4. according to the preparation method of claim 3, it is characterized in that said peptization is dosing with distilled water, controls silica by weight: water=1: 20～40. 5. according to the preparation method of claim 1 or 4, it is characterized in that strontium and europium in the said phosphor composition adopt water-soluble nitrate or acetate, and the purity of salt is percentage weight >=99.9%, According to the stoichiometric ratio and the number of atomic moles of strontium: europium = 1:0.01-0.05, it is added to the silica sol together. 6. According to the preparation method of claim 5, it is characterized in that said dispersant is solid polyvinyl alcohol or solid alkyl trimethyl, and the amount is 0.1-5% of the total weight of the sol. 7. The preparation method according to claim 1 or 6, characterized in that said atomization of the solution is performed at a compressed air temperature of 110°C to 250°C, a dry air volume of 100 to 300m ³ /h, and a material flow of 1 to 2L/h The doped silica colloid is atomized to obtain xerogel particles. 8. The preparation method according to claim 1 or 6, characterized in that said particles are fired at a high temperature in a reducing atmosphere at a temperature of 1000° C. to 1400° C. for 2-4 hours. 9. The preparation method according to claim 7, characterized in that said particles are fired at a high temperature in a reducing atmosphere at a temperature of 1000° C. to 1400° C. for 2-4 hours. 10. The preparation method according to claim 8, characterized in that the reducing atmosphere for firing can be one of N ₂ +H ₂ , active carbon reduction, ammonia decomposition gas or coal gas. 11. The preparation method according to claim 9, characterized in that the reducing atmosphere for firing can be one of N ₂ +H ₂ , activated carbon reduction, ammonia decomposition gas or coal gas.