KR102464841B1 - METHOD FOR PREPARING LANTHANIDE DOPED SiAlON POWDER WITH DOWNSHIFTING LUMINESCENCE PROPERTY - Google Patents

Abstract

The present invention relates to (a) a first aqueous solution comprising a silicon (Si) precursor, an aluminum (Al) precursor and a nitrogen (N) precursor, and selected from Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb and Dy. mixing and stirring a second aqueous solution containing one or more lanthanum group element precursors to be used, and adjusting the pH of the mixed aqueous solution; (b) synthesizing the lanthanum-doped sialon by heating the mixed aqueous solution obtained in step (a) with a microwave and performing a hydrothermal reaction at a temperature of 150 to 250° C.; And (c) drying the lanthanum-doped sialon; as a method for producing a lanthanum-doped sialon powder having downshifting light-emitting properties comprising; according to the present invention, a raw material at a high temperature of 1500°C or higher Unlike the conventional technique of producing a bulk ceramic sintered compact by sintering it and pulverizing it to obtain a powdery phosphor, a hydrothermal synthesis method using microwaves as a heating means is used to quickly, inexpensively and environmentally friendly lanthanum compounds at low temperature (150 ~ 250℃). The SiAlON-based downshifting phosphor material doped with elements (Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, etc.) can be directly manufactured in powder form.

Description

Method for producing lanthanum-doped sialon powder having downshifting luminescent properties

The present invention relates to a method for producing a SiAlON-based downshifting phosphor material in powder form.

SiAlON phosphor has a wide composition range and is a material that has recently been spotlighted as a material that exhibits a wide emission wavelength from green to red by controlling the composition.

In general, a high-temperature process is required to synthesize a high-brightness sialon phosphor. In particular, since most nitrides have greater covalent bonding properties compared to oxides, diffusion is known to be kinetically disadvantageous as a mass transfer mechanism for phosphor synthesis even through a high-temperature process. Therefore, it is common to synthesize a phosphor by generating a eutectic phase by adding a small amount of a sintering aid and promoting material movement by a dissolution-reprecipitation mechanism. The phosphor particles synthesized by the grain boundary phase are obtained in the form of a block having strength by the sintering effect. Therefore, in order to prepare a phosphor powder having an appropriate size, a pulverization process is absolutely necessary as a post-treatment process.

However, it is pointed out as a problem that defects are generated on the surface of the phosphor particles in the process of pulverizing the fired phosphor to obtain an appropriate particle size, thereby lowering the luminance and adversely affecting the luminescence properties.

In order to solve the above problems, Japanese Patent No. 3914987 proposes a method of introducing a heat treatment process to heal surface defects after pulverization, and Japanese Patent Laid-Open No. 2005-255885 discloses pressure-free molding by natural drop filling and Although a method of manufacturing a phosphor without a pulverization process by applying an acid washing process after gas pressure sintering has been proposed, it still has a disadvantage that a sintering process performed at a high temperature of 1500° C. or higher is required.

Korean Patent Registration No. 10-1923273 (Registration Date: 2018.11.22.) Japanese Patent No. 3914987 (Registration Date: 2007.02.16.) Japanese Patent Laid-Open No. 2005-255885 (published on: September 22, 2005)

The present invention solves the problem of deterioration of phosphor luminescence properties due to the pulverization process after high-temperature sintering of the prior art, and has a relatively uniform particle size without a pulverization process through a low-temperature synthesis process in which the sialon synthesis temperature is significantly reduced compared to the prior art. An object of the present invention is to provide a method capable of producing a sialon phosphor powder exhibiting high luminance.

The present invention relates to (a) a first aqueous solution containing a silicon (Si) precursor, an aluminum (Al) precursor and a nitrogen (N) precursor, and from Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb and Dy. mixing and stirring a second aqueous solution containing one or more selected lanthanum group element precursors and adjusting the pH of the mixed aqueous solution; (b) synthesizing the lanthanum-doped sialon by heating the mixed aqueous solution obtained in step (a) with a microwave and performing a hydrothermal reaction at a temperature of 150 to 250° C.; and (c) drying the lanthanum-group-doped sialon.

At this time, the silicon (Si) precursor, the aluminum (Al) precursor, the nitrogen (N) precursor, and the lanthanum group element precursor each dissolved in each of the first aqueous solution and the second aqueous solution mixed in step (a) are mutually independent Nitrate based precursor, acetate based precursor, alkoxide based precursor, halide based precursor, oxyhalide based precursor, carbonate based precursor and sulfate based precursors.

And, the lanthanide-doped sialon synthesized through the microwave hydrothermal synthesis process in step (b) is characterized in that it is represented by the following formula.

[Formula]

M _x ^v+ Si _12-mn Al _m+n O _n N _16-n

(In the above formula,

x = m/v, and M is at least one selected from Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb and Dy)

On the other hand, in the method for producing a lanthanum-doped sialon powder having downshifting luminescence properties according to the present invention, the crystallinity and luminescence properties of the lanthanum-doped sialon powder obtained through the drying process in step (c) are improved. The method may further include heat-treating the lanthanum-doped sialon powder at a temperature of 950 to 1100°C.

Further, in another aspect of the present invention, there is provided a lanthanum-doped sialon powder having a downshifting luminescence property manufactured by the above manufacturing method.

According to the present invention, unlike the prior art in which raw materials are sintered at a high temperature of 1500° C. or higher to produce a bulk ceramic sintered body and pulverized to obtain a powder-type phosphor, the low temperature (150) ~ 250℃), it is a fast, inexpensive and environmentally friendly SiAlON-based downshifting phosphor material doped with lanthanide elements (Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, etc.) in powder form. can

1 is a conceptual diagram illustrating a process for producing a rare-earth-doped sialon powder having downshifting luminescence properties through microwave hydrothermal synthesis in an embodiment of the present application in each step.

In describing the present invention, if it is determined that a detailed description of a related well-known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

Since the embodiment according to the concept of the present invention can have various changes and can have various forms, specific embodiments are illustrated in the drawings and described in detail in the present specification or application. However, this is not intended to limit the embodiment according to the concept of the present invention with respect to a specific disclosed form, and should be understood to include all changes, equivalents or substitutes included in the spirit and scope of the present invention.

The terms used herein are used only to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present specification, terms such as “comprise” or “have” are intended to designate that the described feature, number, step, operation, component, part, or combination thereof exists, and includes one or more other features or numbers. , it is to be understood that it does not preclude the possibility of the presence or addition of steps, operations, components, parts, or combinations thereof.

Hereinafter, the present invention will be described in detail.

The present invention provides SiAlON-based downshifting doped with lanthanide elements such as Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, etc. through hydrothermal synthesis method using microwave as a heating means, fast, inexpensive and environmentally friendly. It relates to a method for producing a phosphor material in powder form.

There are various methods such as co-precipitation method, hydrothermal synthesis method, hydrothermal synthesis method, reverse-micelle method, sol-gel method, etc. to make nano-sized powder. Among them, the hydrothermal synthesis method is a simple process suitable for synthesizing other element-doped compounds. It is well known as an advantageous method for synthesizing nanopowders having crystallinity by controlling process parameters such as temperature, reaction time, pH, and the type of precursor.

As a heating method applied to the hydrothermal synthesis method, there is a method using a gas furnace, an electric heating furnace, a microwave, or the like. Among them, the synthesis method using microwaves transfers energy using vibrating polar molecules, and since the microwave energy is lower than the binding energy of the molecular structure, it has the advantage of promoting product particle formation without affecting the structure.

For reference, the principle of microwaves is that dipolar polarization and interfacial polarization occur in the microwave region, and the dipole changes with a time delay in the change of the microwave electric field. and the heating of polar liquids mainly follows this mechanism. Polar molecules rotate by the electric component of microwaves, and when these polar molecules collide with other neighboring molecules, they gain kinetic energy and the temperature rises.

Advantages of microwaves include reduction of time and energy costs, rapid manufacturing, selective crystalline material synthesis due to temperature control within a short time, uniform heating throughout and improved material properties. It is possible to synthesize improved nanomaterials through catalyst development and selective introduction of microwaves.

In the case of hydrothermal synthesis, which is a conventional catalyst manufacturing method, the reaction time is long and excessive amounts of organic template materials and the washing process after reaction cause excessive environmental pollutants. It also has the advantage of being environmentally friendly because it can reduce pollutants such as cleaning agents and organic mold materials used by selective heating.

Specifically, the method for producing a lanthanum-doped sialon powder having downshifting luminescence properties using a microwave hydrothermal synthesis method according to the present invention includes (a) a silicon (Si) precursor, an aluminum (Al) precursor, and a nitrogen (N) precursor. A first aqueous solution containing adjusting; (b) synthesizing the lanthanum-doped sialon by heating the mixed aqueous solution obtained in step (a) with a microwave and performing a hydrothermal reaction at a temperature of 150 to 250° C.; and (c) drying the lanthanide-doped sialon.

In the step (a), a first aqueous solution containing a silicon (Si) precursor, an aluminum (Al) precursor, and a nitrogen (N) precursor, and lanthanide elements (Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb and At least one selected from Dy) a second aqueous solution containing a precursor is prepared, respectively, and the first aqueous solution and the second aqueous solution are mixed and stirred to obtain a mixed aqueous solution, and then a basic substance is added thereto to adjust the pH to 7 to 11 .

In this case, the silicon (Si) precursor, the aluminum (Al) precursor, and the nitrogen (N) precursor included in the first aqueous solution are each independently a nitrate-based precursor, an acetate-based precursor, and an alkoxide-based precursor. An (alkoxide based) precursor, a halide based precursor, an oxyhalide based precursor, a carbonate based precursor, or a sulfate based precursor may be used without limitation.

In addition, the type of the lanthanum group element precursor included in the second aqueous solution is appropriately selected according to the lanthanum element (at least one of Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb and Dy) to be doped into the sialon. It can be selected, for example, a nitrate-based precursor, an acetate-based precursor, an alkoxide-based precursor, a halide-based precursor, containing a lanthanide ion to be doped, It may be an oxyhalide based precursor, a carbonate based precursor or a sulfate based precursor.

On the other hand, the type of the base added to adjust the pH of the mixed aqueous solution in step (a) is not particularly limited, for example, ammonium hydroxide (NH ₄ OH), potassium hydroxide (KOH), sodium hydroxide (NaOH), etc. can be used

Next, in step (b), the mixed aqueous solution containing the silicon (Si) precursor, the aluminum (Al) precursor, the nitrogen (N) precursor, and the lanthanum group element precursor obtained in the step (a) is heated with a microwave (microwave). A lanthanide-doped sialon is synthesized by hydrothermal reaction at a temperature of 150 to 250 °C.

When the reaction temperature of the hydrothermal synthesis performed in this step (b) is less than 150 ° C, there is a problem that the hydrothermal reaction does not occur smoothly, and when it exceeds 250 ° C, the hydrothermal reaction rate is rapidly increased due to excessive heat, and sialon synthesized There is a problem in that the stability of the particles is lowered.

In addition, the frequency of the microwave used for heating in the hydrothermal synthesis made in this step (b) may be in the range of 300 to 30000 MHz, and among them, four frequencies (915, 2450, 5800, 22125 MHz) are preferable, and more Preferably, a microwave having a frequency of 2450 MHz may be used. For reference, the energy output of a typical microwave system is 600 ~ 700 W, and about 43,000 cal of heat is applied to heating the reactant within 5 minutes.

Next, in step (c), if a process of drying the lanthanum-doped sialon synthesized in the previous step is performed, centrifugal separation of the synthesis reactant and a homemade process may be performed prior to drying. Through the drying process of this step, a lanthanide-doped sialon in powder form is obtained.

Furthermore, the method for producing a lanthanum-doped sialon powder having downshifting luminescence properties according to the present invention includes a process of heat-treating the powder obtained through the drying process in step (c) at a temperature of 950 to 1100° C. can do.

Crystal structure, crystallinity, particle size, concentration of an activator, etc. are important factors affecting the luminance of the phosphor. As the temperature increases, higher crystallinity is induced, resulting in an increase in luminance.

In the present invention, if necessary, heat treatment at a temperature of 950 to 1100° C. may be performed in order to control the crystallinity and particle size of the lanthanum-doped sialon powder prepared through microwave hydrothermal synthesis to improve luminescent properties.

According to the method for manufacturing the lanthanum-doped sialon powder having downshifting luminescence properties according to the present invention described above, raw materials are sintered at a high temperature of 1500° C. or higher to prepare a bulk ceramic sintered body and pulverized to obtain a powder-type phosphor Unlike the prior art of obtaining lanthanide elements (Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, etc.) doped SiAlON-based downshifting phosphor material can be directly produced in powder form.

Claims (5)

(a) a first aqueous solution containing a silicon (Si) precursor, an aluminum (Al) precursor, and a nitrogen (N) precursor, and one selected from Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb and Dy mixing and stirring a second aqueous solution containing the above lanthanum group element precursor and adjusting the pH of the mixed aqueous solution;
(b) heating the mixed aqueous solution obtained in step (a) with a microwave having a frequency of 2450 MHz and performing a hydrothermal reaction at a temperature of 150 to 250° C. to synthesize a lanthanum-doped sialon represented by the following formula ; and
(c) drying the lanthanum-doped sialon; a method for producing a lanthanum-doped sialon powder having downshifting luminescent properties comprising:
[Formula]
M _x ^v+ Si _12-mn Al _m+n O _n N _16-n
(In the above formula,
x = m/v, and M is at least one selected from Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb and Dy). According to claim 1,
Each of the silicon (Si) precursor, the aluminum (Al) precursor, the nitrogen (N) precursor, and the lanthanum group element precursor,
Nitrate based precursor, acetate based precursor, alkoxide based precursor, halide based precursor, oxyhalide based precursor, carbonate based precursor and characterized in that it is selected from sulfate based precursors,
A method for producing a lanthanide-doped sialon powder having downshifting luminescence properties. delete According to claim 1,
Preparation of lanthanum-doped sialon powder having downshifting light-emitting properties, characterized in that it further comprises the step of heat-treating the lanthanum-doped sialon powder obtained by drying in step (c) at a temperature of 950 to 1100 °C Way. delete

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