Full-spectrum red fluorescent powder and preparation method thereof, LED device and lighting device

Abstract

The invention discloses full-spectrum red fluorescent powder and a preparation method thereof. According to the red fluorescent powder, Sr2La3 (GeO4) 3F is used as a matrix material, two active ions of Eu < 3 + > and Mn < 4 + > are co-doped, 580-680 nm wide spectrum coverage is achieved, the doping concentration of Eu < 3 + > is 0.5-2 mol%, the doping concentration of Mn < 4 + > is 0.1-0.8 mol%, Li < + >-Nb < 5 + > is added as charge compensation, and unexpected valence transition of Eu < 3 + > is inhibited. According to the preparation method disclosed by the invention, a three-section gradient reduction method is combined with molten salt medium auxiliary lattice engineering, so that the quantum efficiency and the thermal stability are remarkably improved. The fluorescent powder is suitable for full-spectrum LED illumination, the color rendering index R9 can reach 58, the aging attenuation rate is lower than 7% (at) 1000 h, and the fluorescent powder has excellent comprehensive performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of luminescent materials, and relates to a red phosphor for full-spectrum, a preparation method thereof, an LED device, and a lighting device. Background Art

[0002] Red phosphors are an important type of luminescent materials. Existing red phosphors have the following technical defects: Nitride systems (such as CaAlSiN3:Eu 2+ ) need to be synthesized at a high temperature above 1600 °C, and the crystal phase is prone to segregation, resulting in a quantum efficiency decay of more than 40% at 100 °C; Fluoride systems (such as K2SiF6:Mn 4+ ) have good color rendering, but serious thermal quenching (the brightness drops by 25% at 85 °C), and contain toxic fluorides; Eu 3+ -doped oxides have a low color rendering index R9 (usually < 35) due to the red shift of the main peak (from 611 nm to 625 nm). The existing technology cannot simultaneously meet the requirements of a wide spectral band (FWHM > 90 nm), high quantum efficiency (> 85%), and excellent thermal stability. Summary of the Invention

[0003] Object of the Invention: The object of the present invention is to provide a red phosphor for full-spectrum and a preparation method thereof, to solve the problem that the existing technology cannot simultaneously meet the requirements of a wide spectral band, high quantum efficiency, and excellent thermal stability.

[0004] Technical Solution: A wide-spectrum red phosphor of the present invention, wherein the red phosphor uses Sr2La3(GeO4)3F as a matrix material, and is co-doped with two activating ions, Eu 3+ and Mn 4+ The doping concentration of Eu 3+ is 0.5 - 2 mol%, and the doping concentration of Mn 4+ is 0.1 - 0.8 mol%, and Li + -Nb 5+ is added as charge compensation. The doping amount of Li + is 10% - 30% of the molar concentration of Eu 3+ , and the doping amount of Nb 5+ is 15% - 40% of the molar concentration of Mn 4+ .

[0005] The surface of the red phosphor of the present invention is coated with a 5 - 10 nm fluorination protection layer, and the phonon energy ≤ 600 cm -1 .

[0006] The present invention provides a preparation method for the above-mentioned wide-spectrum red phosphor, comprising the following steps:

[0007] a) Weigh the raw materials SrCO3, La2O3, GeO2, and NH4F in stoichiometric ratios, and dope Eu into the raw materials 3+ and Mn 4+ and add Li + -Nb 5+ as charge compensation, and ball-mill and mix until the particle size D50 ≤ 2 μm;

[0008] b) Conduct three-stage gradient sintering under a H2 / N2 mixed atmosphere:

[0009] The first stage: Keep the temperature at 380 - 400 °C for 1 h, and the volume concentration ratio of H2 in the H2 / N2 mixed atmosphere is 5 - 8%;

[0010] The second stage: Heat up to 760 - 800 °C and keep the temperature for 2 h. The volume concentration ratio of H2 in the H2 / N2 mixed atmosphere is 12 - 15%, and add 3 - 8% of the total mass of the raw materials of BaCO3 molten salt medium;

[0011] The third stage: Keep the temperature at 1000 - 1100 °C for 4 h, and the volume concentration ratio of H2 in the H2 / N2 mixed atmosphere is 2 - 3%;

[0012] c) Immerse the above sintered product in a 0.3 - 0.7 mol / L NH4HF2 solution for 20 - 40 minutes to form a fluorinated protective layer;

[0013] d) Obtain the red phosphor after centrifugation and drying.

[0014] Furthermore, the heating rate in the second stage of step b) is 5 °C / min.

[0015] Furthermore, the pH value of the NH4HF2 solution in step c) is controlled at 3.5 - 4.5, and the treatment temperature is 50 - 70 °C.

[0016] An LED device of the present invention includes the above wide-spectrum red phosphor. The red phosphor is combined with a blue light chip (450 - 460 nm) and a green phosphor (YAG: Ce 3+ ) to form a full-spectrum white light source with a color rendering index Ra ≥ 95 and R9 ≥ 55.

[0017] Furthermore, the mass ratio of the red phosphor in the encapsulating colloid is 15% - 25%, and the particle size distribution D90 / D10 ≤ 3.5.

[0018] The present invention provides a lighting device that uses the above LED device. The color temperature of the lighting device is 2700 - 6500 K, the luminous efficacy ≥ 120 lm / W, and the luminous flux attenuation rate ≤ 8% after working at 100 °C for 1000 hours.

[0019] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages:

[0020] 1. Performance improvement: The quantum efficiency reaches 89% @ 25°C (a 14% increase compared to the nitride system); the thermal stability remains 85% at 100°C (a 30% increase compared to the fluoride system); the phosphor of the present invention is applicable to full-spectrum LED lighting, and the color rendering index R9 can reach 58, meeting the lighting requirements of museums.

[0021] 2. Process advantages: The sintering temperature is reduced to 1100°C (25% energy saving compared to the nitride process); the gradient reduction method is adopted: three-stage temperature control combined with an H2 concentration gradient (5% to 15% to 2%) to precisely control the valence states of Eu / Mn; the molten salt-assisted sintering is adopted: BaCO3 decomposes into BaO at 800°C to promote the diffusion of Ge 4 + and lattice ordering; through surface passivation treatment: NH4HF2 etching forms a fluorinated protective layer to block the erosion of water and oxygen, reducing the aging attenuation rate to 7% @ 1000h.

[0022] 3. Innovation in the material system matrix design: By using F - / O 2- mixed anions to reduce the phonon energy and reduce non-radiative transitions; through the co-doping of Eu 3 + and Mn 4 + to achieve continuous spectral coverage from 580 to 680 nm; the Li + -Nb 5 + ion pair inhibits the reduction of Eu 3 +→Eu 2+ and improves the luminescence stability. Description of the Drawings

[0023] Figure 1 Photoluminescence spectrum of the phosphor in Example 1;

[0024] Figure 2 Luminescence spectrum of the LED light source after encapsulating the phosphor in Example 1;

[0025] Figure 3 Photoluminescence spectrum of the phosphor in Example 2;

[0026] Figure 4 Luminescence spectrum of the LED light source after encapsulating the phosphor in Example 2;

[0027] Figure 5 Photoluminescence spectrum of the phosphor in Example 3;

[0028] Figure 6 Luminescence spectrum of the LED light source after encapsulating the phosphor in Example 3;

[0029] Figure 7 Photoluminescence spectrum of the phosphor prepared in Comparative Example 1;

[0030] Figure 8 Photoluminescence spectrum of the phosphor prepared in Comparative Example 2;

[0031] Figure 9 Photoluminescence spectrum of the phosphor prepared in Comparative Example 3. Detailed implementation manners

[0032] The technical solution of the present invention will be further described below in conjunction with specific implementation manners.

[0033] A broadband red phosphor of this embodiment uses Sr2La3(GeO4)3F as the matrix material and is codoped with Eu 3+ and Mn 4+ two kinds of activator ions, wherein the doping concentration of Eu 3+ is 0.5 - 2 mol%, and the doping concentration of Mn 4+ is 0.1 - 0.8 mol%, and Li + -Nb 5+ is added as charge compensation. The doping amount of Li + is 10 - 30% of the molar concentration of Eu 3+ , and the doping amount of Nb 5+ is 15 - 40% of the molar concentration of Mn 4+ .

[0034] Furthermore, the surface of the red phosphor is coated with a 5 - 10 nm fluorination protection layer, and the phonon energy ≤ 600 cm -1 .

[0035] This embodiment provides an LED device, which includes the above broadband red phosphor. The red phosphor is combined with a blue light chip (450 - 460 nm) and a green phosphor (YAG: Ce 3+ ) to form a full-spectrum white light source with a color rendering index Ra ≥ 95 and R9 ≥ 55. The mass ratio of the red phosphor in the encapsulation colloid is 15 - 25%, and the particle size distribution D90 / D10 ≤ 3.5.

[0036] This embodiment provides an illumination device made of the above LED device. The color temperature of the illumination device is 2700 - 6500 K, the luminous efficacy ≥ 120 lm / W, and the luminous flux attenuation rate ≤ 8% after working at 100 °C for 1000 hours.

[0037] Example 1:

[0038] A preparation method of a broadband red phosphor includes the following steps:

[0039] a) Weigh SrCO3, La2O3, GeO2, and NH4F raw materials according to the stoichiometric ratio, and dope Eu in the raw materials3+ and Mn 4+ and adding Li + -Nb 5+ As charge compensation, ball-mill and mix until the particle size D50 ≤ 2 μm;

[0040] b) Perform three-stage gradient sintering in a H2 / N2 mixed atmosphere:

[0041] The first stage: Keep the temperature at 400 °C for 1 h, and the volume concentration ratio of H2 in the H2 / N2 mixed atmosphere is 5%;

[0042] The second stage: Heat up to 800 °C at a heating rate of 5 °C / min and keep the temperature for 2 h. The volume concentration ratio of H2 in the H2 / N2 mixed atmosphere is 15%, and add 8% of the total mass of the raw materials of BaCO3 molten salt medium;

[0043] The third stage: Keep the temperature at 1100 °C for 4 h, and the volume concentration ratio of H2 in the H2 / N2 mixed atmosphere is 2%;

[0044] c) Immerse the above sintered product in a 0.7 mol / L NH4HF2 solution for 20 minutes to form a fluorinated protective layer; the pH value of the NH4HF2 solution is 3.5, and the treatment temperature is 70 °C;

[0045] d) Obtain the red phosphor after centrifugation and drying.

[0046] As Figure 1 shown, it is the photoluminescence spectrum of the phosphor prepared in this example: under 450 nm excitation, the emission peak covers 580 - 680 nm, FWHM = 92 nm;

[0047] Thermal stability: The luminous intensity at 100 °C is 87% of the initial value;

[0048] As Figure 2 shown, it is the luminous spectrum of the LED light source after encapsulation of the phosphor prepared in this example: combined with a blue light chip, the obtained full spectrum, Ra = 95, R9 = 58.

[0049] Example 2

[0050] A preparation method of a broadband red phosphor, comprising the following steps:

[0051] a) Weigh SrCO3, La2O3, GeO2, NH4F raw materials according to the stoichiometric ratio, dope Eu 3+ and Mn 4+ and adding Li + -Nb 5+ As charge compensation, ball-mill and mix until the particle size D50 ≤ 2 μm;

[0052] b) Perform three-stage gradient sintering under a H2 / N2 mixed atmosphere:

[0053] The first stage: Keep the temperature at 380 °C for 1.5 h, and the volume concentration ratio of H2 in the H2 / N2 mixed atmosphere is 8%;

[0054] The second stage: Heat up to 760 °C at a heating rate of 5 °C / min and keep the temperature for 2.5 h. The volume concentration ratio of H2 in the H2 / N2 mixed atmosphere is 12%, and add 5% of the total mass of the raw materials of BaCO3 molten salt medium;

[0055] The third stage: Keep the temperature at 1000 °C for 4.5 h, and the volume concentration ratio of H2 in the H2 / N2 mixed atmosphere is 3%;

[0056] c) Immerse the above sintered product in a 0.5 mol / L NH4HF2 solution and treat it for 30 minutes to form a fluorinated protective layer; the pH value of the NH4HF2 solution is 4, and the treatment temperature is 60 °C

[0057] d) Obtain the red phosphor after centrifugation and drying.

[0058] As Figure 3 shown is the photoluminescence spectrum of the phosphor prepared in this example: under 450 nm excitation, the emission peak covers 580 - 680 nm, FWHM = 97 nm;

[0059] Thermal stability: The luminescence intensity at 100 °C is 83% of the initial value;

[0060] As Figure 4 shown is the emission spectrum of the LED light source encapsulated with the phosphor prepared in this example: combined with a blue light chip, a full spectrum is obtained, Ra = 94, R9 = 56.

[0061] Example 3

[0062] A preparation method of a broadband red phosphor, comprising the following steps:

[0063] a) Weigh SrCO3, La2O3, GeO2, NH4F raw materials according to the stoichiometric ratio, dope Eu 3+ and Mn 4+ and add Li + -Nb 5+ as charge compensation, and ball mill and mix until the particle size D50 ≤ 2 μm;

[0064] b) Perform three-stage gradient sintering under a H2 / N2 mixed atmosphere:

[0065] The first stage: Keep the temperature at 390 °C for 1.2 h, and the volume concentration ratio of H2 in the H2 / N2 mixed atmosphere is 6%;

[0066] Second stage: Heat up to 780 °C at a heating rate of 5 °C / min and hold for 2.2 h. The volume concentration ratio of H2 in the H2 / N2 mixed atmosphere is 14%, and a BaCO3 molten salt medium accounting for 3% of the total mass of the raw materials is added;

[0067] Third stage: Hold at 1050 °C for 4.2 h. The volume concentration ratio of H2 in the H2 / N2 mixed atmosphere is 2%;

[0068] c) Immerse the above sintered product in a 0.3 mol / L NH4HF2 solution and treat for 40 minutes to form a fluorinated protective layer; the pH value of the NH4HF2 solution is 4.5, and the treatment temperature is 70 °C

[0069] d) Obtain the red phosphor after centrifugation and drying.

[0070] As Figure 5 shown is the photoluminescence spectrum of the phosphor prepared in this example: under 450 nm excitation, the emission peak covers 580 - 680 nm, FWHM = 90 nm;

[0071] Thermal stability: The luminescence intensity at 100 °C is 82% of the initial value;

[0072] As Figure 6 shown is the luminescence spectrum of the LED light source encapsulated with the phosphor prepared in this example: combined with a blue light chip, a full spectrum is obtained, Ra = 96, R9 = 55.

[0073] Comparative Example 1

[0074] The preparation method is the same as that of Example 1, except that Li + -Nb 5+ charge compensation was not added in step a) of the preparation process. As Figure 7 shown, the quantum efficiency of the prepared phosphor decreased to 70% @ 25 °C after analysis, and decayed to 40% at 100 °C; the color rendering index R9 was only 28.

[0075] Comparative Example 2

[0076] The preparation method is the same as that of Example 1, except that the three-stage temperature control combined with the H2 concentration gradient (5% to 15% to 2%) was not adopted in step b) of the preparation process. As Figure 8 shown, the luminescence intensity of the phosphor prepared without the three-stage temperature control combined with the H2 concentration gradient is only 60% of that of the phosphor prepared by the three-stage temperature control combined with the H2 concentration gradient method under the same conditions.

[0077] Comparative Example 3

[0078] The preparation method is the same as that of Example 1, except that no BaCO3 molten salt medium is added in the second stage of step b) in the preparation process for molten salt-assisted sintering. As Figure 9 shown, the luminescence intensity of the phosphor prepared without adding BaCO3 molten salt medium for molten salt-assisted sintering is only 80% of that of the phosphor prepared by adding BaCO3 molten salt medium for molten salt-assisted sintering under the same conditions.

Claims

1. A broad-spectrum red phosphor, characterized in that: The red phosphor is based on Sr2La3(GeO4)3F as the matrix material and co-doped with Eu 3+ and Mn 4+ Two active ions, the Eu 3+ The doping concentration is 0.5-2mol%, the Mn 4+ The doping concentration is 0.1-0.8 mol%, and Li + -Nb 5+ As charge compensation.

2. The broadband red phosphor according to claim 1, characterized in that: The Li + The doping amount is Eu 3+ The molar concentration of Nb is 10%-30%. 5+ The doping amount is Mn 4+ Molar concentration of 15%-40%.

3. The broadband red phosphor according to claim 1, characterized in that: The surface of the red phosphor is coated with a 5-10nm fluorinated protective layer, and the phonon energy is ≤600cm -1 .

4. A method for preparing the broadband red phosphor according to any one of claims 1 to 4, characterized in that: The following steps are involved: a) Weigh SrCO3, La2O3, GeO2, and NH4F raw materials according to the stoichiometric ratio, and dope Eu into the raw materials. 3+ and Mn 4+ And adding Li + -Nb 5+ As charge compensation, ball milling was performed to a particle size D50 ≤ 2 μm; b) Three-stage gradient sintering in H2 / N2 mixed atmosphere: The first stage: 380-400°C for 1-1.5h, the volume concentration of H2 in the H2 / N2 mixed atmosphere is 5-8%; The second stage: heating to 760-800°C and keeping warm for 2-2.5h, the volume concentration of H2 in the H2 / N2 mixed atmosphere is 12-15%, and BaCO3 molten salt medium is added at 3-8% of the total mass of the raw materials; The third stage: 1000-1100°C for 4-4.5h, wherein the volume concentration of H2 in the H2 / N2 mixed atmosphere is 2-3%; c) immersing the sintered product in a 0.3-0.7 mol / L NH4HF2 solution for 20-40 minutes to form a fluorinated protective layer; d) The final product is obtained after centrifugation and drying.

5. The preparation method according to claim 4, characterized in that: The heating rate in the second stage of step b) is 5°C / min.

6. The preparation method according to claim 4, characterized in that: In step c), the pH value of the NH4HF2 solution is controlled at 3.5-4.5, and the treatment temperature is 50-70°C.

7. An LED device, characterized in that: The invention comprises the broadband red phosphor as described in any one of claims 1 to 3, wherein the red phosphor is combined with a blue light chip and a green light phosphor to form a full-spectrum white light source with a color rendering index of Ra≥95 and R9≥55.

8. The LED device according to claim 7, characterized in that: The mass proportion of the red phosphor in the encapsulation colloid is 15%-25%, and the particle size distribution D90 / D10≤3.

5.

9. A lighting device, characterized in that: An LED device as claimed in any one of claims 7 to 8 is used.

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