KR100501742B1 - Yellow phosphor particles with nano-size and method for fabricating thereof - Google Patents

Abstract

The present invention intends to study the morphology and luminescence properties of yellow phosphor powders by applying a flux to produce phosphor powders having nanoparticle size in the production of YAG: Ce phosphor powder by spray pyrolysis. That is, the phosphor powders produced by spray pyrolysis have spherical shapes and irregular shapes during high temperature heat treatment. In the present invention, a YAG: Ce phosphor, that is, a plurality of crystal phases prepared by adding a flux to a phosphor particle prepared by a spray pyrolysis process or by adding a flux and adjusting heat treatment conditions without simply adding a flux, is collected. Unlike the yellow phosphor powders, even at lower temperatures, the spherical particles may be separated into single crystal phases, and the reaction may proceed to form nanoparticle-sized phosphor powder. The phosphor powder thus prepared shows excellent luminescence properties. As a result, the present invention can be prepared by spray pyrolysis to optimize the type and amount of flux, and to adjust the heat treatment conditions to produce a nanoparticle size phosphor powder excellent in luminescence properties.

Description

Yellow phosphor particles with nano-particle size and method for manufacturing the same

The present invention relates to a yellow phosphor, and more particularly, by adding a flux to a spray solution or adding a flux to a spherical particle produced by a spray pyrolysis process to prepare a yellow phosphor having a nano-sized particle. A method for producing a YAG: Ce phosphor, and a yellow phosphor having a nanoparticle size.

Since the phosphor mainly emits light on the surface of the powder, the smaller the particle size is, the more the surface area of the particle increases, and thus the emission intensity increases. However, according to the literature, “Once scattered light is absorbed and disappeared between particles, the optimum particle size for the best luminescence properties is smaller than that of the submicron phosphor powder. It is reported that the intensity of luminescence is at its peak when maintaining the shape of.

Accordingly, the present invention is to study the morphology and luminescence properties of the yellow phosphor powders by applying a flux to prepare the phosphor powder having a nanoparticle size in the production of YAG: Ce phosphor powder by spray pyrolysis. That is, the present invention provides a method for producing a yellow phosphor having a nanoparticle size having excellent luminescence properties and a result thereof by separating a plurality of micro-sized phosphor particles composed of several crystal phases and forming spherical particles due to fluxing. There is this.

In the present invention, a spray solution added with a flux is used to separate nanocrystals of phosphor powder even at a lower temperature than a general spray pyrolysis process, thereby preparing a nanoparticle-sized phosphor powder. The phosphor powder thus prepared shows excellent luminescence properties.

As a result, the main object of the present invention is to use the spray pyrolysis method to optimize the type and amount of the flux, and to control the heat treatment conditions, the yellow light emitting diode represented by the formula (1) of the nanoparticle size having excellent luminescence properties. It relates to the production of phosphors.

`` Formula 1 ''

(Y _1-a Gd _a ) ₃ Al ₅ O ₁₂ : Ce _b

It is 0 <= a <= 1 and 0.001 <= b <= 0.5 in said "Formula 1".

The yellow phosphor having nano-sized particles prepared in the present invention has excellent luminescence properties and has a spherical shape and a good particle size distribution, thereby improving dispersion properties, fluidity, and coating properties in the liquid molding process in manufacturing a white light emitting diode. You can. That is, it is related with the manufacturing method of the yellow fluorescent substance represented by "Formula 1".

`` Formula 1 ''

(Y _1-a Gd _a ) ₃ Al ₅ O ₁₂ : Ce _b

It is 0 <= a <= 1 and 0.001 <= b <= 0.5 in said "Formula 1".

Spray pyrolysis process has been studied in various fields as a process capable of mass synthesis of spherical phosphor powder. Spray pyrolysis is a method of preparing particles by spraying droplets from a precursor solution and drying and pyrolysing them at high temperatures. Phosphors must have spherical small particles to have good properties. In the spray pyrolysis method, multicomponent particles are prepared from droplets made from a homogeneous mixed solution, so that particles of pure composition can be produced. In this case, the particles are dried, thermally decomposed, and crystallized to produce a single particle. Powder manufacturing technology has been developed.

The nanoparticle sized yellow phosphor manufacturing method of the present invention comprises the steps of: 1) sufficiently mixing the precursor material constituting the phosphor matrix, the activator precursor material doping the parent; 2) mixing and adding a flux to the mixture prepared in step 1); 3) dissolving the mixture prepared in step 2) with distilled water or alcohol to prepare a phosphor particle precursor solution; 4) generating a droplet by injecting the phosphor particle precursor solution prepared in step 3) into a spray device; 5) drying and pyrolyzing the droplets generated in step 4) into a reactor at 200 ° C to 1500 ° C; And 6) heat treating the dry pyrolyzed product obtained in step 5) at 1200 ° C to 1700 ° C for 1 hour to 20 hours. "Formula 1" is as follows.

`` Formula 1 ''

(Y _1-a Gd _a ) ₃ Al ₅ O ₁₂ : Ce _b

In said "Formula 1", 0 <= a <= 1 and 0.001 <= b <= 0. 5

Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of the present invention.

Ammonium fluoride, a flux used in the present invention, is included in the precursor spray solution to be dropleted by a spray apparatus, and when the droplet enters a high temperature electric furnace, it has a spherical shape through drying and pyrolysis. By reducing the diffusion distance between the particles and the activation energy of the reaction to help crystal growth at low temperatures, even after a low heat treatment, the crystal phase of the phosphor particles represented by the formula (1) itself forms a phosphor particle. Eventually, the yellow phosphor of nanoparticle size is produced by the role of flux.

The method for preparing a yellow phosphor having a nanoparticle size according to the present invention will be described in more detail by dividing each process as follows.

1) Obtaining Phosphor Particle Precursor Solution

In order to obtain the phosphor represented by the above "Formula 1", the present invention is used by dissolving each precursor material constituting the parent of the phosphor powder and the activator doping the parent, in water, alcohol, acid or the like. As the precursor materials of yttrium, gadolinium, aluminum, and cerium, the metal materials constituting the matrix of the phosphor powder and the active agent doping the matrix are acetate and nitrate, which easily dissolve in a solvent such as water or alcohol. Salts, such as chloride, hydrate, and oxide, are used to derive the optimal composition combination by combining with each other.

In particular, the present invention is characterized in that the use of a flux ammonium fluoride is added by varying the amount from 0.0001M to 3M. Instead of ammonium fluoride used as flux, aluminum fluoride, barium fluoride, magnesium fluoride, ammonium chloride, sodium carbonate, potassium chloride, sodium chloride, lithium chloride, lithium carbonate, potassium carbonate, potassium bromide, etc. may be used alone or in combination. . Ammonium fluoride is melted to reduce the diffusion distance between particles and the activation energy of the reaction to help crystal growth at low temperatures, and even after low heat treatment, the crystalline phase of the phosphor particles represented by Formula 1 itself forms one phosphor particle.

In addition, since the size of the phosphor particles to be prepared is determined according to the concentration of the precursor solution, the concentration of the precursor solution should be appropriate in order to prepare particles of a desired size. The total concentration of the precursor solution is preferably in the range of 0.001M to 4M. The higher the better In this case, when the total concentration of the precursor solution is less than 0.001M, there is a problem that the productivity of the powder falls, while if it exceeds 4M, the spray solution cannot be obtained because of the solubility problem.

2) spraying of droplets

Next, a process of spraying the precursor solution of the phosphor particles into the droplets using a spray device is performed.

In this case, as the spraying apparatus, an ultrasonic spraying apparatus, an air nozzle spraying apparatus, an ultrasonic nozzle spraying apparatus, or the like may be used to spray the precursor into droplets. Here, in the case of the ultrasonic spray device, it is possible to manufacture a fine phosphor powder having a submicron size at a high concentration, and the air nozzle and the ultrasonic nozzle can produce a large amount of particles having a submicron size at a micron.

In particular, in order to control the shape of the powder obtained, a device for generating fine droplets of several microns in size is used. An ultrasonic droplet generator is more suitable for this. To this end, in the present invention, a large amount of droplets are generated by connecting four or more vibrators side by side to generate droplets, and by connecting the droplet generators in parallel to generate tens of liters of droplets per hour by spray pyrolysis. Commercial production of phosphor powders becomes possible. In addition, conventional ultrasonic droplet generators are in direct contact with the vibrator and the solution, in the present invention by using a polyacetyl film to prevent contact between the solution and the vibrator. In other words, a container in which the solution is placed is separately made of glass or acrylic, and a polyacetyl film is attached to the bottom of the container. Polyvinyl film is well sprayed droplets, it is very stable to the vibration of the ultrasonic wave can be used semi-permanently.

3) Production of micro-sized spherical powder

The droplets are converted into precursors of the phosphor particles in a hot tubular reactor. At this time, the temperature of the electric furnace is preferably 200 ℃ to 1,500 ℃ for drying the precursor materials. Although it is a short residence time in such a high temperature reactor, it is dried and pyrolyzed by heating to form a spherical shape. It is melted by ammonium fluoride to reduce the diffusion distance between particles and the activation energy of the reaction to help crystal growth at low temperatures. After the low heat treatment, the crystal phase of the phosphor particles represented by "Formula 1" itself forms one phosphor particle, thereby preparing a phosphor having a nanoparticle size.

4) Generation of nanosized pore powder

 YAG: Ce phosphor powders are obtained by reaction of several hours or more at a high temperature of more than 1,800 ° C when no flux is used in the general solid phase method, but in the present invention, diffusion distance between particles and activation energy of reaction are used by flux. It helps to grow the crystal at low temperature, but because the spray pyrolysis process has a residence time of several milliseconds or several seconds, precursor materials need heat treatment process for crystal growth. The temperature in the heat treatment step varies depending on the type of phosphor, and generally, sufficient crystal growth occurs at 1,200 ° C to 1,700 ° C. At this time, it is important to find a heat treatment condition that can obtain a phosphor powder having a high luminance while maintaining a spherical shape.

Hereinafter, the present invention will be described in more detail with reference to the following examples, which are only intended to explain the present invention more specifically, and the scope of the present invention according to the gist of the present invention to these examples. It will be apparent to one of ordinary skill in the art that the present invention is not limited thereto.

Example 1 Preparation of YAG: Ce Phosphor Powder

A precursor solution is prepared using the following ingredients. Among the starting materials, nitrates are used as precursor materials of gadolinium and yttrium, respectively. The total concentration of the solution was 1M and the composition of the precursor solution was adjusted so that the resulting phosphor powder had a composition of (Y _0.79 Gd _0.2 ) ₃ Al ₅ O ₁₂ : Ce _0.03 . A precursor solution is prepared by adding 10.23 g of yttrium nitrate, 3.39 g of gadolinium nitrate, 23.92 g of aluminum nitrate, 0.163 g of cerium nitrate, and 0.5 M per 100 ml of distilled water.

The precursor solutions thus prepared were generated as submicron-sized droplets using an ultrasonic atomizer and dried and pyrolyzed in a reactor to obtain a powder. At this time, the temperature of the reactor was maintained at 1,100 ℃ and the flow rate of the compressed air used as a carrier gas flows at 30ℓ / min. The ultrasonic nebulizer is a device capable of generating a large amount of droplets, and uses six oscillators connected in series with a frequency of 1.7 MHz. The device is a large capacity that sprays 3 liters of solution per hour and is the capacity available in the actual production process.

The spherical powders obtained by the spray pyrolysis process do not sufficiently crystallize because the reactor temperature is low and the residence time is short. However, the ammonium fluoride used in the present invention acted as a flux to lower the formation temperature of the phosphor crystal, which was then subjected to a heat treatment at 1,400 ° C. for 4 hours.

Example 2 Preparation of YAG: Ce Phosphor Powder

Using the same components as in Example 1, phosphors were prepared in the same manner, spherical particles were prepared by spray pyrolysis without using ammonium fluoride in the spray solution, and then 0.3M barium fluoride was added to the spherical particles. A phosphor powder is prepared by heat treatment at a constant temperature of 1,400 ° C. for 4 hours.

Comparative Example 1 Preparation of YAG: Ce Phosphor Powder Without Flux

Phosphor powders were prepared by the same ingredients and methods as in Example 1, except that no flux was added.

Test Example 1 Analysis of Morphology and Luminescence Characteristics of YAG: Ce Phosphor Powder

Powder form and luminescence properties of the phosphors obtained in Examples 1 and 2 and Comparative Example 1 were measured.

1 is an electron micrograph of phosphor powders corresponding to Comparative Example 1. FIG. In the case of Figure 1, the phosphor is not added to the flux consists of several micro-sized phosphor particles composed of a plurality of crystal phases gathered inside the sphere. In the case of Figure 2 when the flux is added to the spray solution is composed of nano-sized mold particles. Figure 3 is a case of adding a flux to the spherical particles after the spray pyrolysis process consists of nano-sized phosphor particles.

4 is a graph comparing light emission characteristics in the visible light region of the powder of the phosphors obtained in Examples 1 and 2 and Comparative Example 1. FIG.

As described above, since the phosphor mainly emits light on the surface of the powder, the smaller the particle size, the more the surface area of the particle increases and the emission intensity increases. However, when the particle size becomes smaller than a certain limit, the scattered light is absorbed and disappeared between the particles, so the optimum particle size for the best light emission characteristics is shown in the literature. Luminescence intensity is said to be at the peak when maintaining. On the other hand, it can be seen that the phosphor powders of the nanoparticle size obtained in Examples 1 and 2 exhibited superior luminescence properties in Comparative Example 1.

As described above, the present invention relates to a method for producing a yellow phosphor having nano-sized particles, that is, to a particle prepared by spraying pyrolysis or spraying droplets by adding a flux to prepare the yellow phosphor having the nano-sized particles. By adding a flux to prepare a phosphor, a flux is added to several micro-sized phosphor particles in which a plurality of crystal phases prepared by a conventional spray pyrolysis process are added to separate one of the crystal phases to produce nano-sized YAG: Ce phosphor particles. . As a result, an ultrasonic atomizer which improves dispersion characteristics, fluidity and coating characteristics in liquid phase molding process of white light emitting diodes by producing nanoparticle-sized phosphors having better luminous luminance than YAG: Ce phosphor powder under the same conditions, and generates a large amount of droplets. By using the device, it is possible to mass-produce YAG: Ce phosphor powders, which can be widely applied to displays and light emitting diodes.

1 is an electron micrograph of YAG: Ce phosphor powder obtained when Comparative Example 1 is not used,

2 is an electron micrograph of a YAG: Ce phosphor powder prepared according to Example 1 of the present invention,

3 is an electron micrograph of a YAG: Ce phosphor powder prepared according to Example 2 of the present invention;

Figure 4 is a graph comparing the emission intensity of the YAG: Ce phosphor powder prepared according to Comparative Example 1 and Examples 1 and 2.

Claims (10)

1) sufficiently mixing the precursor material constituting the phosphor matrix and the activator precursor material dope the parent; 2) mixing and adding a flux to the mixture prepared in step 1); 3) dissolving the mixture prepared in step 2) with distilled water or alcohol to prepare a phosphor particle precursor solution; 4) generating a droplet by injecting the phosphor particle precursor solution prepared in step 3) into a spray device; 5) drying and pyrolyzing the droplets generated in step 4) into a reactor at 200 ° C to 1500 ° C; And 6) is prepared through a step of heat-treating the dry pyrolyte obtained in step 5) at 1200 ° C to 1700 ° C for 1 to 20 hours; It is expressed by the next "Formula 1", `` Formula 1 '' (Y <sub>1-a</sub> Gd <sub>a</sub> ) <sub>3</sub> Al <sub>5</sub> O <sub>12</sub> : Ce <sub>b</sub> In said "Formula 1", 0 <= a <= 1 and 0.001 <= b <= 0. 5; The precursor material constituting the phosphor matrix in step 1) and the activator precursor material doping the matrix are selected from acetates, nitrates and chlorides of metals (yttrium, gadolinium, aluminum and cerium). Become; The flux material in step 2) is selected from one or two selected from ammonium fluoride, aluminum fluoride, barium fluoride, magnesium fluoride, ammonium chloride, sodium carbonate, potassium chloride, sodium chloride, lithium chloride, lithium carbonate, potassium carbonate and potassium bromide ; The amount of flux material is 0.001M-3M; The concentration of the phosphor particle precursor solution of step 3) is 0.001M to 4M; The diameter of the droplets generated by the spraying device of step 4) is 0.1 μm to 30 μm; The spray device of step 4) is one selected from an ultrasonic spray device, an air nozzle spray device and an ultrasonic nozzle spray device; The ultrasonic spraying device is connected to 4 to 1,000 vibrators side by side, the lower part of the spray solution container made of a polyvinyl film is separated between the solution and the vibrator nanoparticle size yellow phosphor manufacturing method. delete delete delete delete delete delete delete The method of claim 1, wherein in the step 5) to increase the dispersibility of the nano-powder, a nanoparticle size yellow phosphor manufacturing method, characterized in that for adding a milling process. Yellow phosphor of the nano-particle size represented by the following "Formula 1", characterized in that prepared by the method of claim 1. `` Formula 1 '' (Y _1-a Gd _a ) ₃ Al ₅ O ₁₂ : Ce _b In said "Formula 1", 0 <= a <= 1 and 0.001 <= b <= 0. 5