CN105199731A - A kind of NaLaMgWO6:xSm3+ red fluorescent powder for LED and preparation method thereof - Google Patents

Abstract

The invention discloses a NaLaMgWO ₆ :xSm ³⁺ red fluorescent powder for LEDs and a preparation method thereof, belonging to the technical field of luminescent material preparation. The present invention uses NaOH·H ₂ O, WO ₃ , La ₂ O ₃ , MgO and Sm ₂ O ₃ as raw materials to prepare NaLaMgWO ₆ :xSm ³⁺ red fluorescent powder for LED. The advantages of this method are that the raw materials are easy to obtain and the operation is simple , short preparation cycle, no pollution, suitable for large-scale industrial production. The red fluorescent powder prepared by the present invention is tested and analyzed by XRD, SEM and fluorescence spectrophotometer, and it can be known that the prepared NaLaMgWO ₆ : xSm ³⁺ (wherein x=0.01～0.05) fluorescent powder has high purity, good crystallization performance, and particle size. Uniform diameter and good dispersion, the average particle size is 1-5μm, the emission wavelength coverage range is 550-680nm, the red light color purity exceeds 92%, and the correlated color temperature reaches 1392K.

Description

A kind of NaLaMgWO6:xSm3+ red fluorescent powder for LED and preparation method thereof

technical field

The invention belongs to the technical field of luminescent material preparation, and relates to a red fluorescent powder and a preparation method thereof, in particular to a NaLaMgWO ₆ :xSm ³⁺ red fluorescent powder for LEDs and a preparation method thereof.

Background technique

In recent years, white LEDs have attracted extensive attention in lighting, display and other fields because of their advantages such as environmental protection, high efficiency, energy saving, and long life. At present, there are two main ways to obtain white light: one is to excite yellow phosphor powder by a blue light chip; the other is to excite three primary color phosphors from an ultraviolet-near ultraviolet chip to form white light. The former is limited by the lack of red light components in the spectrum, and its color rendering index-based color reproduction is reduced. The latter is currently restricted by the lack of phosphors that can produce efficient red light emission under the excitation of ultraviolet-near ultraviolet light. Therefore, it is of great significance to prepare a phosphor that can produce efficient and stable red light emission under the excitation of ultraviolet-near ultraviolet light. As an important luminescent activator, Sm ³⁺ has strong absorption in the range of ultraviolet-near ultraviolet-blue light, and can emit red light with high quantum efficiency ^[1] .

At present, the host compounds involved in Sm ³⁺ doped phosphor mainly include silicate, phosphate, borate, vanadate, aluminate, tungstate and so on. Among them, tungstate is a typical self-activated luminescent material. The luminescence spectrum is very stable. The intrinsic emission spectrum band is very wide, occupying most of the visible light region. The cations in tungstate strongly affect the position of the emission band. Tungstate can be activated by certain impurities. After these impurities are mixed into the tungstate lattice, it can make it have special properties of luminescence. Therefore, tungstate is a host material with excellent luminescent properties.

The preparation of tungstate by traditional solid phase method, due to high reaction temperature, long reaction time, uneven particle size distribution, it is difficult to obtain spherical particles with regular shape, and there are easy to exist impurity phases, which weakens the luminous efficiency of phosphors.

Contents of the invention

The object of the present invention is to provide a kind of NaLaMgWO ₆ :xSm ³⁺ red phosphor powder for LED and preparation method thereof, the method is easy to operate, green and environmentally friendly; the prepared NaLaMgWO ₆ :xSm ³⁺ red phosphor powder has high purity, uniform particle size, Good crystallization performance and excellent luminescence performance.

The present invention is realized through the following technical solutions:

The invention discloses a preparation method of NaLaMgWO ₆ :xSm ³⁺ red fluorescent powder for LED, which comprises the following steps:

1) According to the molar ratio of (1.1～1.2):1:0.5:1:(0.005～0.025), take NaOH·H ₂ O, WO ₃ , La ₂ O ₃ , MgO and Sm ₂ O ₃ as raw materials;

2) Take NaOH·H ₂ O, add deionized water and stir well, then add WO ₃ , reflux at 70-90°C for 5-10 hours, after cooling, dry and grind to obtain powder A;

3) Add Sm ₂ O ₃ into a polyvinyl alcohol solution with a concentration of 0.5% to 1.5%, ultrasonically treat it to disperse it evenly, add concentrated nitric acid to the dispersion to dissolve all the Sm ₂ O ₃ to obtain a transparent liquid B;

4) Mix La ₂ O ₃ , MgO and powder A and grind them evenly, then add transparent liquid B, continue grinding, let stand at room temperature for 5-10 hours, and dry to obtain mixed powder C;

5) Put the mixed powder in a box-type resistance furnace, keep it warm at 900-1100°C for 3-10 hours, take it out after cooling with the furnace, and grind it to prepare NaLaMgWO ₆ :xSm ³⁺ red phosphor, where x=0.01～ 0.05.

Step 2) The mass of deionized water added is 3-5 times the mass of NaOH·H ₂ O.

Step 2) is reflux treatment in a condensing reflux device under a silicone oil bath condition of 70°C to 90°C.

Step 4) is grinding in an agate mortar for 20-40 minutes.

Step 5) the sintering system in the box-type resistance furnace is as follows:

From room temperature, the temperature was raised to 150-200°C at a rate of 2°C/min, then to 200-600°C at a rate of 3°C/min, and then to 900-1100°C at a rate of 5°C/min, and kept for 3-10 hours.

The invention also discloses the red fluorescent powder for LED prepared by the above method. The chemical composition of the red fluorescent powder is: NaLaMgWO ₆ :xSm ³⁺ , where x=0.01-0.05.

The average particle size of the red phosphor powder is 1-5 μm, the emission wavelength coverage range is 550-680 nm, the red light color purity reaches 92%, and the correlated color temperature reaches 1392K.

Compared with the prior art, the present invention has the following beneficial technical effects:

The present invention takes NaOH·H ₂ O, WO ₃ , La ₂ O ₃ , MgO and Sm ₂ O ₃ as raw materials according to the molar ratio of (1.1～1.2):1:0.5:1:(0.005～0.025) to prepare LED NaLaMgWO ₆ : xSm ³⁺ red phosphor, the purpose of excessive NaOH·H ₂ O is to reduce the influence of Na ⁺ volatilization in the later calcination; this method belongs to the combination of liquid phase method and solid phase method, and introduces Na and W in the form of ions And Sm element, reduce the energy required for the later calcination reaction, can reduce the reaction temperature and shorten the reaction time. Adding polyvinyl alcohol forms a colloidal environment, so that these ions can be more evenly distributed, which is beneficial to the full reaction of raw materials and improves the purity of the product. The method has the advantages of simple and easy-to-obtain raw materials, simple operation, short preparation period, no pollution, and is suitable for large-scale industrial production.

The NaLaMgWO ₆ : xSm ³⁺ (where x=0.01～0.05) red phosphor powder prepared by the present invention is tested and analyzed by XRD, SEM and fluorescence spectrophotometer, and it can be seen that the prepared NaLaMgWO ₆ : xSm ³⁺ (where x= 0.01-0.05) phosphors have high purity, good crystallization performance, uniform particle size and good dispersion, with an average particle size of 1-5μm, emission wavelength coverage of 550-680nm, red light color purity over 92%, and correlated color temperature up to 1392K .

Description of drawings

Fig. 1 is the SEM picture of the NaLaMgWO ₆ : xSm ³⁺ red phosphor that embodiment 1 makes;

Fig. 2 is the emission spectrogram of the NaLaMgWO ₆ :xSm ³⁺ red fluorescent powder that embodiment 3 makes;

Fig. 3 is the CIE diagram of NaLaMgWO ₆ :xSm ³⁺ red phosphor prepared in Example 4.

Detailed ways

The present invention is described in further detail below in conjunction with accompanying drawing:

Example 1

1) According to the molar ratio of 1.14:1:0.5:1:0.025, respectively weigh NaOH·H ₂ O, WO ₃ , La ₂ O ₃ , MgO, Sm ₂ O ₃ as raw materials;

2) Add the weighed NaOH·H ₂ O into the beaker, add an appropriate amount of deionized water to it to fully dissolve it, add the NaOH solution and WO ₃ weighed in step 1 into the condensing reflux device, and Insulate in a silicone oil bath at 80°C for 6 hours, take it out after cooling down to room temperature with the device, dry and grind to obtain powder A;

3) Add the Sm ₂ O ₃ weighed in step 1 into 10ml of polyvinyl alcohol solution with a concentration of 1%, ultrasonically treat it to make it evenly dispersed, and add concentrated nitric acid drop by drop to the dispersion to make the Sm ₂ O ₃ completely Dissolve (concentrated nitric acid can be slightly excessive), to obtain transparent liquid B;

4) Put the La ₂ O ₃ , MgO weighed in step 1 and the powder A obtained in step 2 into an agate mortar and grind thoroughly to mix all components evenly, then add the mixed solution B obtained in step 3 and continue grinding 30min, dry at room temperature after aging for 10h, to obtain mixture powder C;

5) Put the mixture powder C obtained in step 4 in a box-type resistance furnace, keep it warm at 1100°C for 10 hours, take it out after cooling with the furnace, and grind it to obtain NaLaMgWO ₆ : xSm ³⁺ (where x=0.05) red phosphor ;

The temperature system of step 5 is to start from room temperature, raise the temperature to 150-200°C at a rate of 2°C/min, then raise the temperature to 200-600°C at a rate of 3°C/min, and then raise the temperature to 1100°C at a rate of 5°C/min , keep warm for 10h.

Referring to Fig. 1, it is the SEM picture of the NaLaMgWO ₆ :xSm ³⁺ fluorescent powder prepared in this example. It can be seen from the figure that the particle size of the sample prepared in Example 1 is 2.5um to 7.5um, and the morphology Regular, uniform particle size distribution.

Example 2

1) According to the molar ratio of 1.18:1:0.5:1:0.025, respectively weigh NaOH·H ₂ O, WO ₃ , La ₂ O ₃ , MgO, Sm ₂ O ₃ as raw materials;

2) Add the weighed NaOH·H ₂ O into the beaker, add an appropriate amount of deionized water to it to fully dissolve it, add the NaOH solution and WO ₃ weighed in step 1 into the condensing reflux device, and Insulate in a silicone oil bath at 75°C for 8 hours, take it out after cooling down to room temperature with the device, dry and grind to obtain powder A;

3) Add the Sm ₂ O ₃ weighed in step 1 into 10ml of polyvinyl alcohol solution with a concentration of 1.5%, ultrasonically treat it to make it uniformly dispersed, and add concentrated nitric acid drop by drop to the dispersion to make the Sm ₂ O ₃ completely Dissolve (concentrated nitric acid can be slightly excessive), to obtain transparent liquid B;

4) Put the La ₂ O ₃ , MgO weighed in step 1 and the powder A obtained in step 2 into an agate mortar and grind thoroughly to mix all components evenly, then add the mixed solution B obtained in step 3 and continue grinding 30min, dry at room temperature after aging for 8h to obtain mixture powder C;

5) Put the mixture powder C obtained in step 4 in a box-type resistance furnace, keep it warm at 1000°C for 3 hours, take it out after cooling with the furnace, and grind it to obtain NaLaMgWO ₆ : xSm ³⁺ (where x=0.05) red phosphor ;

The temperature system in step 5 is to start from room temperature, raise the temperature to 150-200°C at a rate of 2°C/min, then raise the temperature to 200-600°C at a rate of 3°C/min, and then raise the temperature to 1000°C at a rate of 5°C/min , keep warm for 3h.

Example 3

1) According to the molar ratio of 1.1:1:0.5:1:0.005, respectively weigh NaOH·H ₂ O, WO ₃ , La ₂ O ₃ , MgO, Sm ₂ O ₃ as raw materials;

2) Add the weighed NaOH·H ₂ O into the beaker, add an appropriate amount of deionized water to it to fully dissolve it, add the NaOH solution and WO ₃ weighed in step 1 into the condensing reflux device, and Insulate in a silicone oil bath at 70°C for 10 hours, take it out after cooling down to room temperature with the device, dry and grind to obtain powder A;

3) Add the Sm ₂ O ₃ weighed in step 1 into 10ml of polyvinyl alcohol solution with a concentration of 0.5%, ultrasonically treat it to make it uniformly dispersed, and add concentrated nitric acid drop by drop to the dispersion to make the Sm ₂ O ₃ completely Dissolve (concentrated nitric acid can be slightly excessive), to obtain transparent liquid B;

4) Put the La2O3 and MgO weighed in step 1 and the powder A obtained in step 2 into an agate mortar and grind thoroughly to mix all components evenly, then add the mixed solution B obtained in step 3, and continue grinding for 30 minutes at room temperature Put it aside for 5 hours and then dry it to obtain the mixture powder C;

5) Put the mixture powder C obtained in step 4 in a box-type resistance furnace, heat it at 1050°C for 8 hours, take it out after cooling with the furnace, and grind it to obtain NaLaMgWO ₆ : xSm ³⁺ (where x=0.01) red phosphor ;

The temperature system of step 5 is to start from room temperature, raise the temperature to 150-200°C at a rate of 2°C/min, then raise the temperature to 200-600°C at a rate of 3°C/min, and then raise the temperature to 1050°C at a rate of 5°C/min , keep warm for 8h.

Referring to Fig. 2, the emission spectrum diagram of the NaLaMgWO ₆ : xSm ³⁺ phosphor prepared in this example, it can be seen from the figure that the sample prepared in Example 3 is mainly The emission peak is located at 650nm, which corresponds to the characteristic transition of ⁴ G _5/2 → ⁶ H _9/2 of Sm ³⁺ . Although there are emission peaks at other positions, their relative intensities are relatively low. It shows that the prepared sample mainly emits red light with a wavelength of 650nm under the excitation of near-ultraviolet light with a wavelength of 380nm.

Example 4

1) According to the molar ratio of 1.2:1:0.5:1:0.01, respectively weigh NaOH·H ₂ O, WO ₃ , La ₂ O ₃ , MgO, Sm ₂ O ₃ as raw materials;

2) Add the weighed NaOH·H ₂ O into the beaker, add an appropriate amount of deionized water to it to fully dissolve it, add the NaOH solution and WO ₃ weighed in step 1 into the condensing reflux device, and Insulate in a silicone oil bath at 790°C for 5 hours, take it out after cooling down to room temperature with the device, dry and grind to obtain powder A;

3) Add the Sm ₂ O ₃ weighed in step 1 into 10ml of polyvinyl alcohol solution with a concentration of 1%, ultrasonically treat it to make it evenly dispersed, and add concentrated nitric acid drop by drop to the dispersion to make the Sm ₂ O ₃ completely Dissolve (concentrated nitric acid can be slightly excessive), to obtain transparent liquid B;

4) Put the La ₂ O ₃ , MgO weighed in step 1 and the powder A obtained in step 2 into an agate mortar and grind thoroughly to mix all components evenly, then add the mixed solution B obtained in step 3 and continue grinding 30min, dry at room temperature after aging for 6h, to obtain mixture powder C;

5) Put the mixture powder C obtained in step 4 in a box-type resistance furnace, keep it warm at 900°C for 5 hours, take it out after cooling with the furnace, and grind it to obtain NaLaMgWO ₆ : xSm ³⁺ (where x=0.02) red phosphor ;

The temperature system in step 5 is to start from room temperature, raise the temperature to 150-200°C at a rate of 2°C/min, then raise the temperature to 200-600°C at a rate of 3°C/min, and then raise the temperature to 900°C at a rate of 5°C/min , keep warm for 5h.

Referring to Figure 3, it is the CIE diagram of the NaLaMgWO ₆ : xSm ³⁺ phosphor prepared in this example. It can be seen from the figure that the sample prepared in Example 4 is excited by near-ultraviolet light with a wavelength of 380 nm. The color coordinates of red light are located at (0.6266, 0.3622), which is close to the standard red light point, and its color temperature reaches 1172k, indicating that the prepared sample can emit relatively pure warm red light under the excitation of near-ultraviolet light with a wavelength of 380nm, and can be used in White LEDs for enhanced color temperature.

Example 5

1) According to the molar ratio of 1.15:1:0.5:1:0.015, respectively weigh NaOH·H ₂ O, WO ₃ , La ₂ O ₃ , MgO, Sm ₂ O ₃ as raw materials;

2) Add the weighed NaOH·H ₂ O into the beaker, add an appropriate amount of deionized water to it to fully dissolve it, add the NaOH solution and WO ₃ weighed in step 1 into the condensing reflux device, and Insulate in a silicone oil bath at 85°C for 9 hours, take it out after cooling down to room temperature with the device, dry and grind to obtain powder A;

3) Add the Sm ₂ O ₃ weighed in step 1 into 10ml of polyvinyl alcohol solution with a concentration of 1.5%, ultrasonically treat it to make it uniformly dispersed, and add concentrated nitric acid drop by drop to the dispersion to make the Sm ₂ O ₃ completely Dissolve (concentrated nitric acid can be slightly excessive), to obtain transparent liquid B;

4) Put the La ₂ O ₃ , MgO weighed in step 1 and the powder A obtained in step 2 into an agate mortar and grind thoroughly to mix all components evenly, then add the mixed solution B obtained in step 3 and continue grinding 30min, dried at room temperature for 9h to obtain mixture powder C;

5) Put the mixture powder C obtained in step 4 in a box-type resistance furnace, keep it warm at 950°C for 9 hours, take it out after cooling with the furnace, and grind it to obtain NaLaMgWO ₆ : xSm ³⁺ (where x=0.03) red phosphor ; The temperature system of step 5 is to heat up to 150-200°C at a rate of 2°C/min from room temperature, then to 200-600°C at a rate of 3°C/min, and then to 950°C at a rate of 5°C/min ℃, keep warm for 9h.

Claims (7)

1. a LED NaLaMgWO ₆: xSm ³⁺the preparation method of red fluorescence powder, is characterized in that, comprises the following steps:

1) by (1.1 ~ 1.2): 1:0.5:1:(0.005 ~ 0.025) mol ratio, get NaOHH respectively ₂o, WO ₃, La ₂o ₃, MgO and Sm ₂o ₃as raw material;

2) NaOHH is got ₂o, adds deionized water and stirs, then add WO ₃, reflow treatment 5 ~ 10h at 70 ~ 90 DEG C, after cooling, dries, grinding, obtained powder A;

3) by Sm ₂o ₃adding concentration is in the polyvinyl alcohol solution of 0.5% ~ 1.5%, and supersound process makes it be uniformly dispersed, and adds concentrated nitric acid and make Sm in dispersion liquid ₂o ₃whole dissolving obtains transparent liquid B;

4) by La ₂o ₃, MgO and powder A mix after grinding evenly, then add transparent liquid B, continue grinding, after at room temperature leaving standstill 5 ~ 10h, dry, obtained mixed powder C;

5) mixed powder C is placed in chamber type electric resistance furnace, at 900 ~ 1100 DEG C, is incubated 3 ~ 10h, takes out after furnace cooling, grinding, obtained NaLaMgWO ₆: xSm ³⁺red fluorescence powder, wherein x=0.01 ~ 0.05.

2. a kind of LED NaLaMgWO according to claim 1 ₆: xSm ³⁺the preparation method of red fluorescence powder, is characterized in that, step 2) quality that adds deionized water is NaOHH ₂3 ~ 5 times of O quality.

3. a kind of LED NaLaMgWO according to claim 1 ₆: xSm ³⁺the preparation method of red fluorescence powder, is characterized in that, step 2) be in condensation reflux unit, and under the silicone oil bath condition of 70 DEG C ~ 90 DEG C reflow treatment.

4. a kind of LED NaLaMgWO according to claim 1 ₆: xSm ³⁺the preparation method of red fluorescence powder, is characterized in that, step 4) be grind 20 ~ 40min in agate mortar.

5. a kind of LED NaLaMgWO according to claim 1 ₆: xSm ³⁺the preparation method of red fluorescence powder, is characterized in that, step 5) sintering schedule in chamber type electric resistance furnace is as follows:

From room temperature, with 2 DEG C/min ramp to 150 ~ 200 DEG C, then with 3 DEG C/min ramp to 200 ~ 600 DEG C, then with 5 DEG C/min ramp to 900 ~ 1100 DEG C, insulation 3 ~ 10h.

6. adopt the LED red fluorescence powder that the method in Claims 1 to 5 described in any one is obtained, it is characterized in that, the chemical constitution of this red fluorescence powder is: NaLaMgWO ₆: xSm ³⁺, wherein, x=0.01 ~ 0.05.

7. LED red fluorescence powder according to claim 6, is characterized in that, the median size of the powder of described red fluorescence powder is 1 ~ 5 μm, and emission wavelength coverage is 550 ~ 680nm, and red light color purity reaches 92%, and correlated(color)temperature reaches 1392K.