CN111925795A - Green fluorescent powder and preparation method and application thereof - Google Patents

Abstract

The invention discloses green fluorescent powder and a preparation method and application thereof. The chemical general formula of the green phosphor is Sr_33‑xEu_xLu₆(PO₄)₂₈X is more than or equal to 0 and less than or equal to 1. The fluorescent powder can be effectively excited by near ultraviolet light and emits wider green light. The green fluorescent powder is packaged with the existing blue fluorescent powder and red fluorescent powder, so that a white light LED with the color rendering index exceeding 90 can be obtained, the white light LED has extremely small luminous color drift, and the luminous color is extremely stable.

Description

A kind of green phosphor and its preparation method and application

technical field

The invention relates to the technical field of luminescent materials, in particular to a green fluorescent powder and a preparation method and application thereof.

Background technique

White LED has the advantages of long life, high energy saving, environmental protection, etc. It is a new type of lighting and display light source developed after incandescent lamps, fluorescent lamps and high-pressure gas discharge lamps. In white LED lighting, the combination of blue LED chip + yellow phosphor + red phosphor is mainly used at present. Part of the blue light is absorbed by the phosphor, and the remaining blue light is mixed with the light emitted by the yellow-red phosphor to obtain white light. Although this method of obtaining white light is relatively inexpensive, the color of the obtained white light is relatively cold, and the color rendering index is low (less than 80). In order to further improve the color rendering effect of white LED lighting, some white LED lighting uses a combination of near-ultraviolet LED chips + blue, green and red phosphors. service life.

Green phosphors profoundly affect the color rendering index of white LEDs. In addition, the emission peaks of many high-efficiency green phosphors are relatively narrow, and the full width at half maximum is below 70 nanometers, such as β-Sialon. Such phosphors are conducive to expanding the color gamut and are suitable for display systems. However, the combination of narrow peak phosphors is difficult to simulate sunlight and is not suitable for lighting systems. Therefore, the development of broad-peak green phosphors is of great significance for the lighting field.

Phosphate phosphors have the advantages of low synthesis temperature, good thermal stability, stable charge and luminous efficiency, and have received more and more attention in the field of phosphors. Since the electron cloud diffusion effect of phosphate phosphors is weaker than that of borates, silicates and aluminates are currently doped with Eu ²⁺ to obtain phosphors with shorter emission wavelengths, such as blue and violet phosphors , a common example is ABPO ₄ :Eu ²⁺ blue phosphor (A is alkali metal, B is alkaline earth metal). Therefore, the development of new green phosphors with broad-peak emission of phosphate has breakthrough significance.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the deficiencies of the prior art and provide a green phosphor, a preparation method and application thereof, which can be effectively excited by near-ultraviolet light and emit broad green light.

To achieve the above object, the technical scheme adopted by the present invention is as follows:

A green phosphor, whose general chemical formula is Sr _33-x Eu _x Lu ₆ (PO ₄ ) ₂₈ , 0≤x≤1.

The structure of the green phosphor of the present invention has five metal lattice sites. After Eu ²⁺ enters the lattice, the phosphor has a relatively broad emission peak, and its half-height width reaches 84 nanometers. The phosphor powder of the present invention can be effectively excited by near-ultraviolet light, and is suitable for near-ultraviolet LED chips.

Further, the general chemical formula of the green phosphor is Sr _{33-x Eux} Lu ₆ (PO ₄ ) ₂₈ , 0.11≤x≤0.55, within this range, the luminous intensity of the phosphor is relatively high; further, all the The general chemical formula of the green phosphor is Sr _32.67 Eu _0.33 Lu ₆ (PO ₄ ) ₂₈ , and the phosphor has higher luminescence intensity and better luminescence thermal quenching performance.

The present invention also provides a method for preparing the green phosphor, comprising the following steps:

(1) Take the Sr-containing compound, the Eu compound, the Lu-containing compound and the P-containing compound as the raw material, weigh the raw material according to the stoichiometric ratio of the corresponding element in the general chemical formula, and mix the raw material uniformly;

(2) The mixed raw materials are calcined in a reducing atmosphere, the calcination temperature is 1200-1400°C, and the calcination time is 2-10h, then cooled to below 200°C, taken out, crushed, and ground to obtain the green phosphor.

The inventor's experiments found that the calcination temperature is 1200-1400°C, and the calcination time is 2-10h, which is beneficial to obtain Sr _33-x Eu _x Lu ₆ (PO ₄ ) ₂₈ green phosphor. When the calcination temperature is lower than 1200° C., the reaction Incomplete, and the product will melt when the calcination temperature exceeds 1400°C, and the most suitable calcination temperature is 1400°C; considering the effect and cost, the calcination time is preferably 4 hours.

Further, the Sr-containing compound includes at least one of SrCO ₃ , SrO, Sr(NO ₃ ) ₂ , and SrC ₂ O ₄ .

Further, the Eu-containing compound includes at least one of Eu ₂ O ₃ and Eu(NO ₃ ) ₃ ·nH ₂ O.

Further, the Lu-containing compound includes at least one of Lu ₂ O ₃ and Lu(NO ₃ ) ₃ ·nH ₂ O, 0≤n≤9.

Further, the P-containing compound includes at least one of NH ₄ H ₂ PO ₄ and (NH ₄ ) ₂ HPO ₄ .

In the present invention, the above-mentioned Sr-containing compounds, Eu-containing compounds, Lu-containing compounds and P-containing compounds are preferred, and green phosphors with broad peak emission can be prepared.

Further, the reducing atmosphere in the step (2) is H ₂ /N ₂ atmosphere, and the volume of H ₂ accounts for 2% to 20% of the volume of the reducing atmosphere.

The present invention also provides the application of the above-mentioned green phosphors in white light LEDs.

The present invention also provides a white light LED, the white light LED includes the above-mentioned green phosphor, blue phosphor and red phosphor.

The green phosphor of the present invention is packaged with the existing blue phosphor and red phosphor, and a white LED with a color rendering index exceeding 90 can be obtained. Under the condition of increasing the driving current, the luminous intensity of the white LED is enhanced; in addition, under the high current driving, the change of the color coordinate is very small, which is still in the white light region. Therefore, the white light LED of the present invention has extremely small emission color drift and extremely stable emission color, which can meet the requirements in the field of general lighting.

Compared with the prior art, the beneficial effects of the present invention are:

The phosphor powder of the present invention can be effectively excited by near-ultraviolet light, emit wide green light, and is suitable for near-ultraviolet LED chips. In addition, the green phosphor of the present invention is packaged with the existing blue phosphor and red phosphor to obtain a white LED with a color rendering index exceeding 90. The white LED emits very little color drift and extremely stable emission color.

Description of drawings

FIG. 1 is the XRD pattern (a) and theoretical diffraction pattern (b) of Sr _32.67 Eu _0.33 Lu ₆ (PO ₄ ) ₂₈ prepared in Example 1. FIG.

2 is the excitation spectrum (scanning at 510 nm) and emission spectrum (excitation at 380 nm) of the phosphor powder prepared in Example 1.

3 is a three-dimensional thermal quenching spectrum (a) and thermal quenching curve (b) of the phosphor prepared in Example 1.

Fig. 4 is the emission spectrum (a) of the phosphors prepared in Example 1, the blue phosphors and the red phosphors after being packaged into LEDs, the emission spectra under the driving of 3V (b) and 0.02-0.12mA (b) current, and Emission color coordinates (c) at 0.02 mA and 0.12 mA.

5 is the XRD pattern of Sr _32.89 Eu _0.11 Lu ₆ (PO ₄ ) ₂₈ prepared in Example 2.

FIG. 6 is the XRD pattern of Sr _32.45 Eu _0.55 Lu ₆ (PO ₄ ) ₂₈ prepared in Example 3. FIG.

FIG. 7 is the emission spectrum (excitation at 380 nm) of the phosphors prepared in Examples 1-3.

Detailed ways

In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below with reference to specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

In the examples, the experimental methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used can be obtained from commercial sources unless otherwise specified.

Example 1

The general chemical formula of the green phosphor of this embodiment is Sr _32.67 Eu _0.33 Lu ₆ (PO ₄ ) ₂₈ , and the preparation method thereof includes the following steps:

(1) Accurately weigh 2.3620g SrCO ₃ , 0.0291g Eu ₂ O ₃ , 0.5969g Lu ₂ O ₃ and 1.6103g NH ₄ H ₂ PO ₄ in proportion to the mixing tank, and stir well to mix;

(2) Transfer the mixed raw materials to a 40mL corundum crucible, put the crucible into an atmosphere furnace, calcinate at 1300°C for 4h, and pass into a H ₂ /N ₂ atmosphere, wherein the volume of H ₂ accounts for 8% of the total volume of the atmosphere. %, the volume of N ₂ accounts for 92% of the total volume of the atmosphere. After the temperature in the furnace is lowered to below 200 °C, the sample is taken out, ground, and pulverized to obtain green phosphors.

XRD analysis was performed on the green phosphor of Example 1, and its XRD pattern was shown in FIG. 1 . The results in FIG. 1 show that the phosphor powder with pure phase structure was prepared in Example 1.

The excitation and emission spectra of the phosphor prepared in Example 1 are shown in Figure 2. It can be seen from Figure 2 that the green phosphor is suitable for excitation by ultraviolet and near-ultraviolet chips and violet light (250-400 nm), and the emission peak is around 510 nm. broad peak green light.

The thermal quenching spectrum of the phosphor prepared in Example 1 is shown in Figure 3(a), and the variation of the integrated intensity with temperature is shown in Figure 3(b). The results show that the phosphor powder has better thermal quenching performance, and still maintains more than 80% of the intensity at 150°C (LED operating temperature).

Figure 4 shows the emission spectrum of the phosphor powder, blue phosphor powder and red phosphor powder prepared in Example 1 packaged into a white light LED. The white light LED has a relatively high color rendering index, reaching 92. Under the condition of increasing the driving current, the luminous intensity is enhanced (Fig. 4(b)). In addition, under high current driving, the change of the color coordinates of the light emission is very small, and it is still in the white light region. It can be seen that the light emission color of the white light LED has a very small drift and the light emission color is extremely stable.

Example 2

The general chemical formula of the green phosphor of this embodiment is Sr _32.89 Eu _0.11 Lu ₆ (PO ₄ ) ₂₈ , and the preparation method thereof includes the following steps:

(1) Accurately weigh 2.4278g SrCO ₃ , 0.0097g Eu ₂ O ₃ , 0.5969g Lu ₂ O ₃ and 1.6103g NH ₄ H ₂ PO ₄ in proportion to the mixing tank, fully stir to mix;

(2) Transfer the mixed raw materials to a 40mL corundum crucible, put the crucible into an atmosphere furnace, calcinate at 1400°C for 4h, and pass into a H ₂ /N ₂ atmosphere, wherein the volume of H ₂ accounts for 8% of the total volume of the atmosphere. %, the volume of N ₂ accounts for 92% of the total volume of the atmosphere. After the temperature in the furnace is lowered to below 200 °C, the sample is taken out, ground, and pulverized to obtain green phosphors.

XRD analysis was performed on the green phosphor of Example 2, and its XRD pattern was shown in FIG. 5 . The results in FIG. 5 show that the phosphor powder with pure phase structure was prepared in Example 2.

Example 3

The general chemical formula of the green phosphor in this embodiment is Sr _32.45 Eu _0.55 Lu ₆ (PO ₄ ) ₂₈ , and the preparation method thereof includes the following steps:

(1) Accurately weigh 2.3953g SrCO ₃ , 0.0484g Eu ₂ O ₃ , 0.5969g Lu ₂ O ₃ and 1.6103g NH ₄ H ₂ PO ₄ in proportion to the mixing tank, and stir well to mix;

(2) Transfer the mixed raw materials to a 40mL corundum crucible, put the crucible into an atmosphere furnace, calcinate at 1400°C for 4h, and pass into a H ₂ /N ₂ atmosphere, wherein the volume of H ₂ accounts for 8% of the total volume of the atmosphere. %, the volume of N ₂ accounts for 92% of the total volume of the atmosphere. After the temperature in the furnace is lowered to below 200 °C, the sample is taken out, ground, and pulverized to obtain green phosphors.

XRD analysis was performed on the green phosphor of Example 3, and its XRD pattern was shown in FIG. 6 . The results in FIG. 6 show that the phosphor powder with pure phase structure was prepared in Example 3.

The comparison of the emission spectra (excitation at 380 nm) of the phosphors of Examples 1 to 3 is shown in Figure 7, and it can be seen that 0.33 is the optimum concentration.

Claims (10)

1. A green phosphor is characterized in that the chemical general formula of the green phosphor is Sr_33-xEu_xLu₆(PO₄)₂₈，0≤x≤1。

2. The green phosphor according to claim 1, wherein the general chemical formula is Sr_33-xEu_xLu₆(PO₄)₂₈0.11. ltoreq. x.ltoreq.0.55, preferably, x is 0.33.

3. The method for preparing green phosphor according to claim 1 or 2, comprising the steps of:

(1) taking a Sr-containing compound, a Eu-containing compound, a Lu-containing compound and a P-containing compound as raw materials, weighing the raw materials according to the stoichiometric ratio of corresponding elements in a chemical general formula, and uniformly mixing the raw materials;

(2) and calcining the uniformly mixed raw materials in a reducing atmosphere at the temperature of 1200-1400 ℃ for 2-10 h, cooling to the temperature below 200 ℃, taking out, crushing and grinding to obtain the green fluorescent powder.

4. The method for producing a green phosphor according to claim 3, wherein the Sr-containing compound includes SrCO₃、SrO、Sr(NO₃)₂、SrC₂O₄At least one of (1).

5. The method of claim 3, wherein the Eu-containing compound includes Eu₂O₃、Eu(NO₃)₃·nH₂At least one of O.

6. The method for preparing green phosphor according to claim 3, wherein the Lu-containing compound comprises Lu₂O₃、Lu(NO₃)₃·nH₂N is more than or equal to 0 and less than or equal to 9.

7. The method of claim 3, wherein the P-containing compound comprises NH₄H₂PO₄、(NH₄)₂HPO₄At least one of (1).

8. The method for preparing green phosphor according to claim 3,characterized in that the reducing atmosphere in the step (2) is H₂/N₂Atmosphere, and H₂The volume of the reducing atmosphere accounts for 2 to 20 percent of the volume of the reducing atmosphere.

9. Use of the green phosphor of claim 1 or 2 in a white LED.

10. A white LED comprising the green phosphor, the blue phosphor and the red phosphor according to claim 1 or 2.

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