KR20020069934A - Manufacturing method of strontium aluminate phosphor by the sol-gel method - Google Patents

Abstract

PURPOSE: Provided is a process for producing a strontium aluminate phosphor by using sol-gel method capable of producing a phosphor which is excellent in luminance and long persistence and can be calcined at relatively low temperature. CONSTITUTION: The process comprises the steps of (i) mixing 200-220 mol of distilled water(H2O) and 4-5 mol of isopropanol(iso-C3H7OH) and 0.1-0.3 mol of HCl which is catalyst, into 1 mol of Al(O-nC3H7)3 and stirring the mixture until pH of the mixture is not changed at about 80 deg.C; (ii) sequentially adding 55-65 mol of distilled water, and 0.02-0.03 mol of Eu(NO3)3.6H2O and Dy(NO3)3.6H2O respectively, and 0.1-0.3 mol of HNO3(which is catalyst) into 0.95 mol of Sr(NO3)2 and stirring the mixture until pH of the mixture is not changed; (iii) mixing solutions formed in the steps (i) and (ii) and stirring the mixture until pH of the mixture is not changed, so as to obtain a sol, and drying the sol at 100 deg.C for 48 hours and pulverizing the dried sol; (iv) calcining the pulverized powder in atmosphere of 1200 deg.C or more for 4 hours and re-pulverizing the powder; and (v) heat-treating the repulverized powder under reducing atmosphere of mixed gas of nitrogen and hydrogen in 9:1 at 1300 deg.C for 3 hours.

Description

Manufacturing method of strontium aluminate phosphor by the sol-gel method

The present invention relates to a method for producing a strontium aluminate phosphor, and more particularly, SrAl ₂ O ₄ : Eu ²⁺ and Dy ³⁺ phosphors having excellent fluorescence characteristics such as luminescence and afterglow characteristics can be prepared by using a sol-gel method. It relates to a method for producing a strontium aluminate phosphor using the sol-gel method.

In general, a phosphor refers to a material that absorbs energy excited from ultraviolet rays or radiation and then emits energy as light even when the excitation light source is blocked. The phosphor has a photoluminescent type and a self-luminous type, and the self-luminous type phosphor has a radioactive material as an excitation source, and thus has a continuous and long emission time, but there is a problem in disposal after use. In addition, the phosphorescent phosphor refers to a phosphor that accumulates excitation energy such as sunlight or light, reduces the energy to visible light, and emits light for a long time, and is mainly used for luminous paints and the like.

As a representative long afterglow phosphor, ZnS: Cu green phosphors are known, and the ZnS: Cu green phosphors have been studied since the 1920's and are used in various applications such as luminous paints, luminous clocks, and disaster prevention displays. However, this phosphor has a short afterglow time, a large decrease in light emission, and the use of the phosphor is limited due to a disadvantage that the afterglow luminance is drastically reduced when the particle is made finer and used as a paint or ink.

Therefore, there is an urgent need for the development of a general-purpose new photoluminescent material, in particular an oxide-based afterglow photoluminescent material, which is chemically and environmentally stable as well as long afterglow property compared to the conventional photoluminescent material.

Therefore, one of the known photoluminescent materials is a strontium aluminate (SrO-Al ₂ O ₃ ) -based phosphor, and in particular, SrAl ₂ O ₄ : Eu ²⁺ and Dy ³⁺ photoluminescent phosphors are widely known. The SrO-Al ₂ O ₃ -based phosphor is not only chemically stable but also excellent in durability, and is one of phosphors that have been widely studied recently because of its excellent stability without having a radioactive material as an excitation source. In particular, afterglow luminance and afterlife life of the SrAl ₂ O ₄ : Eu ²⁺ and Dy ³⁺ phosphors are improved by about 10 times compared to those of ZnS: Cu phosphors, and have excellent light resistance and show excellent stability even when exposed to outdoor UV light for a long time. .

Floating zone method, hydrothermal synthesis method, solid phase reaction method and the like are known as methods for producing the SrAl ₂ O ₄ : Eu ²⁺ and Dy ³⁺ phosphors. However, since the floating zone method requires expensive equipment in manufacturing, there is a disadvantage in that the unit cost is increased. In addition, the hydrothermal synthesis method has the advantage that the starting material is inexpensive, and the particle size, stoichiometric ratio, etc. can be controlled relatively freely, but expensive equipment is required.

In addition, in the solid phase reaction method, raw materials such as SrCO ₃ , Eu ₂ O ₃ , Al ₂ O _3, and the like are mixed and powdered without a flux to prepare the SrAl ₂ O ₄ : Eu ²⁺ phosphor. It is difficult to control particle shape and size because it requires high firing temperature and long firing time because it is manufactured by heat treatment at.

Accordingly, the present invention uses a sol-gel method that can easily adjust the shape and size of particles to prepare SrAl ₂ O ₄ : EU ²⁺ , Dy ³⁺ phosphors having excellent fluorescence characteristics, and thus, can be fired at a relatively low temperature and emit light. And to provide a method for producing a strontium aluminate phosphor using a sol-gel method to enable the production of a phosphor having excellent afterglow characteristics.

1 is a view showing the results of X-ray diffraction analysis of the phosphor according to the change in calcination temperature.

FIG. 2 is a diagram showing emission spectra of phosphors according to changes in the addition amount of Eu (NO ₃ ) ₃ .6H ₂ O and Dy (NO ₃ ) ₃ .6H ₂ O.

3 is a view showing the afterglow characteristic of a phosphor according to the addition amount of Eu (NO ₃ ) ₃ .6H ₂ O and Dy (NO ₃ ) ₃ .6H ₂ O.

4 is a view showing a light emission spectrum according to the crushed particle size of the prepared phosphor.

5 is a view showing afterglow characteristics according to the pulverized particle size of the manufactured phosphor.

The present invention to achieve the above object

200 to 220 moles of distilled water (H ₂ O), 4 to 5 moles of isopropanol (iso-C ₃ H ₇ OH) and 0.1 hydrochloric acid (HCl) as catalyst per 1 mole of Al (O- n C ₃ H ₇ ) ₃ Molar to 0.3 mole and stirred at a temperature of about 80 ° C. until there is no change in pH. Separately, 0.95 mole of Sr (NO ₃ ) _{2 is} added to 55 mole to 65 moles of distilled water, followed by Eu (NO ₃ ) _3. 0.02 mol to 0.03 mol of 6H ₂ O and Dy (NO ₃ ) ₃ .6H ₂ O were added, and then 0.1 to 0.3 mol of HNO ₃ was added to the catalyst and stirred until there was no change in pH. After mixing the solution of and stirred at 80 ℃ until there is no change in pH, the obtained sol was dried at 100 ℃ for more than 48 hours and pulverized, and then the pulverized powder was calcined in an atmosphere of 1200 ℃ or more for 4 hours and then Pulverized and heat-treated at 1300 ° C. for 3 hours under a reducing atmosphere of a gas mixed with nitrogen and hydrogen at 9: 1. It can achieve by providing the manufacturing method of the strontium aluminate fluorescent substance using the sol-gel method.

Hereinafter, the present invention will be described in more detail.

In the present invention, first, the mixture of 200 mol to 220 mol of distilled water, 4 mol to 5 mol of isopropanol and 0.1 mol to 0.3 mol of hydrochloric acid with a catalyst is added to 1 mol of Al (O- n C ₃ H ₇ ) ₃ and stirred at a temperature of about 80 ° C. Hydrolysis is performed.

Al (O- n C ₃ H ₇ ) ₃ is used as a raw material of Al ₂ O ₃ of the elements constituting the SrAl ₂ O ₄ : EU ²⁺ , Dy ³⁺ phosphor to apply the sol-gel method The material is a raw material. This raw material is hydrolyzed in a solvent containing a catalyst and distilled water. At this time, the addition amount of the catalyst was added within the range of the conventional catalyst addition amount, and distilled water and isopropanol were used as a solvent.

At this time, when preparing ceramics using the sol-gel method, it is common to add an organic solvent such as alcohol as a peptizing agent for homogeneous mixing, and in particular, it is common to use an alcohol of the same kind as the alkoxy group of the metal alkoxide. Therefore, isopropanol was used in the present invention, and the amount of the isopropanol was added within the range of addition in the production of ceramics using a conventional sol-gel method.

When the mixture having the above mixing ratio is stirred at a temperature of about 80 ° C. for about 3 hours, the pH of the solution does not change any more and is kept constant. This is a point where the hydrolysis is completed. Terminate the reaction. Approximate pH is around 2.85

Separately, in the present invention, 50 mol to 70 mol of distilled water is added to 0.95 mol of Sr (NO ₃ ) _2, and then 0.02 mol of Eu (NO ₃ ) ₃ · 6H ₂ O and Dy (NO ₃ ) ₃ · 6H ₂ O, respectively. 0.03 mol is added, and then 0.1 mol to 0.3 mol of HNO ₃ is added to the catalyst and stirred.

Sr (NO ₃ ) ₂ , Eu (NO ₃ ) ₃ · 6H ₂ O, and Dy (NO ₃ ) ₃ · 6H ₂ O are each SrAl ₂ O ₄ : Eu ²⁺ and Dy ³⁺ phosphors. It is used as raw material for SrO and Eu ₂ O ₃ and Dy ₂ O ₃ . At this time, Sr (NO ₃ ) ₂ was added so as to be in a general range constituting the composition ratio in the phosphor, and this was added to distilled water and hydrolyzed using a catalyst.

In the _{Eu (NO 3) 3 · 6H} 2 O is intended to form the Eu ²⁺ in the phosphor typically Eu ²⁺ in the SrO-Al ₂ O ₃ based fluorescent material, by various light energy, including sunlight the outermost The electrons in the outer electron band are transferred to the valence band, and the electrons transferred to the valence band emit the excitation light in the process of being excited by the outermost electron band. At this time, when the addition amount of Eu (NO ₃ ) ₃ · 6H ₂ O exceeds 0.03 mol, the luminous intensity is high, but the amount of Dy ³⁺ is relatively reduced, resulting in a problem of deterioration in afterglow characteristics. Since the luminous intensity is lowered, it is preferable to add Eu (NO ₃ ) ₃ .6H ₂ O in an amount of 0.02 to 0.03 molar ratio.

In addition, Dy (NO ₃ ) ₃ .6H ₂ O is for forming Dy ³⁺ in the phosphor, and in general, Dy ³⁺ is related to the afterglow property. In other words, the electrons are transferred by the light energy of short wavelength to the level higher than the valence band of Eu ²⁺ , and thus the afterglow characteristics are exhibited because the rate of the electron transfer is slow. At this time, when the amount of Dy (NO ₃ ) ₃ · 6H ₂ O added exceeds 0.03 mole, there is an advantage that the afterglow property is excellent, but the amount of Eu ³⁺ is relatively reduced, the emission intensity is lowered, less than 0.02 mole Since there is a problem in that the afterglow property is lowered, it is preferable to add Dy (NO ₃ ) ₃ .6H ₂ O in an amount of 0.01 mol to 0.03 mol.

When the mixture having the above mixing ratio is stirred at a temperature of about 80 ° C. for 3 hours, the pH of the solution does not change any more and is kept constant. This is a point where the hydrolysis is completed. To exit. Approximate pH is around 0.85

Each of the solutions thus prepared is mixed and stirred at 80 ° C. to obtain a sol-like transparent mixed solution at a point where the pH is kept constant. The prepared sol is pulverized after drying for at least 48 hours at 100 ℃ or more.

The pulverized powder is calcined in an atmosphere of 1200 ° C. or higher for 4 hours and then regrind. In this process, the Sr0-Al ₂ O ₃ crystal to be obtained in the present invention can be obtained. That is, in the calcination process, the Sr ₃ Al ₂ O ₆ phase starts to appear at about 800 ° C., and at about 1000 ° C., the SrAl ₂ O ₄ phase is formed. The Sr ₃ Al ₂ O ₆ phase and the SrAl ₂ O ₄ crystal phase are mixed up to 1100 ° C., and the SrAl ₂ O ₄ crystal phase forms the main phase at 1200 ° C. Therefore, there is an advantage that can be obtained by heat treatment at a temperature lower than 1400 ℃ required by the conventional solid-phase reaction method.

At this time, the particle size of the regrind greatly affects the light emission and afterglow characteristics. If the particle size is less than 20 μm, the luminous intensity is weak and the afterglow time is shortened. Therefore, the particle size is preferably 20 μm or more.

After calcination at the above temperature, the pulverized powder is heat-treated again under a reducing atmosphere of a gas mixed with nitrogen and hydrogen at 9: 1 at 1300 ° C. for 3 hours to prepare a phosphor according to the present invention. .

Hereinafter, the present invention will be described in more detail with reference to the following examples, which are presented to aid the understanding of the present invention, but the present invention is not limited thereto.

<Example 1>

1 mole of Al (O- n C ₃ H ₇ ) ₃ (Jamssem Chimica, Belgium), 210 moles of distilled water (H ₂ O), 5 moles of isopropanol (iso-C ₃ H ₇ OH) and hydrochloric acid (HCl) as catalyst ) 0.2 mole was added and mixed, and stirred at a temperature of 80 ± 5 ° C. until there was no change in pH, and the reaction was terminated.

In a separate reaction vessel, 0.95 mol of Sr (NO ₃ ) ₂ (Wako chem. Co., Japan), 60 mol of distilled water, 0.02 mol of Eu (NO ₃ ) ₃ · 6H ₂ O (Wako chem. Co., Japan), and 0.03 mole of Dy (NO ₃ ) ₃ .6H ₂ O (Kanto Chem. Co., Japan) was added, followed by 0.2 mole addition of HNO ₃ as a catalyst, followed by stirring until there was no change in pH.

Each of the solutions prepared above was mixed and stirred at 80 ° C. until no change in pH was dried at 100 ° C. for 48 hours and then pulverized. After calcining for 4 hours in an atmosphere of 4 ° C., 900 ° C., 1000 ° C., 1100 ° C., and 1200 ° C., and then regrinding, the pulverized powder was regenerated under a reducing atmosphere of a gas containing nitrogen and hydrogen at 9: 1 Heat treatment for a time to prepare a phosphor. At this time, the particle size of the final pulverized product was 20㎛ to 45㎛.

In order to confirm the crystal of the prepared phosphor, an X-ray diffractometer (Philips. Co. Pw1720, Holland) was measured under CuKα, Ni filter, 30 kV, 20 mA, and the results are shown in FIG. 1.

As shown in FIG. 1, a peak of the Sr ₂ Al ₂ O ₆ phase was observed from a temperature of 800 ° C. or higher, and a peak of SrAl ₂ O ₄ began to be observed from 1000 ° C. FIG. It was found that the crystal phases of Sr ₃ Al ₂ O ₆ and SrAl ₂ O ₄ were mixed at 1000 ° C. to 1100 ° C., but crystals of SrAl ₂ O ₄ were formed as the main phase at a temperature of 1200 ° C. or higher. Therefore, in order to form a single-phase SrAl ₂ O ₄ from a mixed powder of SrCO ₃ , Eu ₂ O ₃ , Al ₂ O ₃ without adding a solvent in the conventional solid phase reaction method, the temperature of 1400 ° C. or higher was required. In the case of SrAl ₂ O ₄ has the advantage that the crystal formation temperature can be lowered during the preparation of the mother phase crystals.

Based on the results, the calcining temperature was set at 1200 ° C., and then the light emission characteristics and the afterglow characteristics according to the addition amount of Eu (NO ₃ ) ₃ · 6H ₂ O and Dy (NO ₃ ) ₃ · 6H ₂ O were determined. 2 was carried out.

<Example 2>

The calcining temperature was 1200 ° C., and 0.04 mol: 0.01 mol, 0.03 mol: 0.02 mol, 0.02 mol: 0.03 mol, 0.04 mol of Eu (NO ₃ ) ₃ · 6H ₂ O and Dy (NO ₃ ) ₃ · 6H ₂ O, respectively. A phosphor was prepared in the same manner as in Example 1 except for changing to 0.01 mole.

In order to investigate the emission spectrum using the prepared phosphor, a fluorescence spectrophotometer (Luminescence spectrometer, AMINCO · Bowman Series 2, USA) was used to investigate. 0.2mg of the fine powder was applied to the cell, excited with a halogen discharge lamp, and the excitation spectrum was measured from 270nm to 400nm at a scanning speed of 3nm / sec, and the emission spectrum was fixed at 360nm after the excitation spectrum was fixed at 360nm. The scanning speed was measured from 400 nm to 700 nm and the results are shown in FIG. 2.

In addition, in order to investigate the afterglow property using the prepared phosphor, a luminescence spectrometer (Luminescence spectrometer, AMINCO · Bowman Series 2, USA) was used to investigate. After irradiating with a halogen discharge lamp for 10 minutes, excitation was stopped and the afterglow time of 15 minutes was investigated. At this time, the excitation spectrum was measured at 360 nm and the emission spectrum was fixed at 520 nm, and the results are shown in FIG. 3.

As shown in FIG. 2, the emission spectrum measured by exciting a sample with a halogen lamp having a wavelength of 360 nm is 450 nm having a maximum emission wavelength of 520 nm, which is a yellowish green emission region that is almost similar to that of a conventional photoluminescent material, ZnS: Cu. It showed a broad emission spectrum of 650 nm, which is considered that the outermost electron of Eu ²⁺ added to the SrAl ₂ O ₄ crystal is light emission due to transition to the valence band. In particular, it can be seen that the intensity of luminescence increases as the content of Eu ²⁺ increases.

Also, as shown in FIG. 3, after 10 minutes of excitation with a halogen discharge lamp, the afterglow property according to the amount of Eu ²⁺ and Dy ³⁺ added tends to decrease exponentially with time regardless of the composition. . In particular, considering that the visually observable luminance is 0.32 mcd / m2, the luminance is greater than 1200 seconds, so that when the sample is viewed in the dark state after 1200 seconds, the sample can be distinguished by the naked eye. It shows long afterglow characteristics. As shown in the figure, it can be seen that afterglow characteristics are maintained for a long time as the amount of Dy ³⁺ is increased.

2 and ₃ , the addition amount of Eu (NO ₃ ) ₃ .6H ₂ O and Dy (NO ₃ ) ₃ .6H ₂ O is 0.02 mol to 0.03 mol, respectively.

Based on Examples 1 and 2, the calcination temperature was 1200 ° C, and the addition amount of Eu (NO ₃ ) ₃ .6H ₂ O and Dy (NO ₃ ) ₃ .6H ₂ O was 0.02 in consideration of the luminescence and long light characteristics. Mole: 0.03 mole and the following Example 3 was carried out.

<Example 3>

The calcining temperature was 1200 ° C., and Eu (NO ₃ ) ₃ · 6H ₂ O and Dy (NO ₃ ) ₃ · 6H ₂ O were 0.02 mol: 0.03 mol, and the particle size of the pulverized product was less than 20 µm and 20 µm to 45 µm. And a phosphor was prepared in the same manner as in Example 1 except that the classification was performed at 45 μm or more.

In order to investigate the emission spectrum using the prepared phosphor and the pulverized phosphor, a luminescence spectrometer (Luminescence spectrometer, AMINCO · Bowman Series 2, USA) was used. 0.2mg of the fine powder was applied to the cell, excited with a halogen discharge lamp, and the excitation spectrum was measured from 270nm to 400nm at a scanning speed of 3nm / sec, and the emission spectrum was fixed at 360nm after the excitation spectrum was fixed at 360nm. The scanning speed was measured from 400 nm to 700 nm and the results are shown in FIG. 4.

In addition, in order to investigate the afterglow property using the prepared phosphor and the pulverized phosphor, a fluorescence spectrophotometer (Luminescence spectrometer, AMINCO · Bowman Series 2, USA) was used. After irradiating with a halogen discharge lamp for 10 minutes, excitation was stopped and the afterglow time of 15 minutes was investigated. In this case, the excitation spectrum was measured at 360 nm and the emission spectrum was fixed at 520 nm, and the results are shown in FIG. 5.

As shown in FIG. 4, when the emission spectrum measured by pulverization was measured at less than 20 μm, 20 μm to 45 μm, and 45 μm or more, and excited by a halogen lamp having a wavelength of 360 nm, the light emission intensity after pulverization was pulverized at 45 μm or more. It can be seen that the reduction to about 80%, 63% at 20㎛ to 45㎛, and 50% at less than 20㎛.

In addition, as shown in FIG. 5, after classifying the phosphor to less than 20 μm, 20 μm to 45 μm, and 45 μm or more, the afterglow property is measured. As a result, the afterglow property is also decreased.

As described above, the present invention uses the sol-gel method, which is easy to control the shape and size of particles, to prepare SrAl ₂ O ₄ : EU ²⁺ and Dy ³⁺ phosphors having excellent fluorescence characteristics. It is a useful invention to provide a method for producing a phosphor using the sol-gel method that enables not only possible but also a phosphor having excellent light emission and afterglow characteristics.

Claims (2)

200 to 220 moles of distilled water (H ₂ O), 4 to 5 moles of isopropanol (iso-C ₃ H ₇ OH) and 0.1 hydrochloric acid (HCl) as catalyst per 1 mole of Al (O- n C ₃ H ₇ ) ₃ Molar to 0.3 mole and stirred at a temperature of about 80 ° C. until there is no change in pH. Separately, 0.95 mole of Sr (NO ₃ ) _{2 is} added to 55 mole to 65 moles of distilled water, followed by Eu (NO ₃ ) _3. 0.02 mol to 0.03 mol of 6H ₂ O and Dy (NO ₃ ) ₃ .6H ₂ O were added, and then 0.1 to 0.3 mol of HNO ₃ was added to the catalyst and stirred until there was no change in pH. After mixing the solution of and stirred at 80 ℃ until there is no change in pH, the obtained sol was dried at 100 ℃ for more than 48 hours and pulverized, and then the pulverized powder was calcined in an atmosphere of 1200 ℃ or more for 4 hours and then Pulverized and heat-treated at 1300 ° C. for 3 hours under a reducing atmosphere of a gas mixed with nitrogen and hydrogen at 9: 1. Method for producing a strontium aluminate phosphor using the sol-gel method. The method for producing a strontium aluminate phosphor using the sol-gel method according to claim 1, wherein the particle size of the pulverized product is 20 µm or more.