Preparation and application of yellow luminous fluorescent powder for warm-color WLED (White Light Emitting Diode) illumination

Abstract

The invention discloses preparation and application of yellow luminescent fluorescent powder for warm-color WLED (White Light Emitting Diode) illumination, which comprises the following steps: adding rare earth oxide Tb4O7 into a heated HNO3 solution, and stirring to obtain a colorless transparent solution; acid discharge treatment: volatilizing the colorless and transparent solution, adding deionized water for dissolving, and repeating for multiple times to enable the pH value of the solution to be neutral; adding deionized water into the material volatilized for the last time to obtain a solution; adding aluminum nitrate, gadolinium nitrate, cerium nitrate and citric acid into the solution, stirring, and heating for reaction to obtain light yellow gel; drying and grinding the faint yellow gel to obtain precursor powder; and carrying out high-temperature sintering process on the precursor powder to obtain the yellow luminescent fluorescent powder for warm-color WLED (White Light Emitting Diode) illumination. The yellow luminescent fluorescent powder disclosed by the invention has relatively high luminescent intensity and internal quantum efficiency, so that high-brightness luminescence of a WLED (White Light Emitting Diode) device can be realized; and the excellent light-emitting thermal stability is beneficial to stable and high-brightness light emitting of the WLED device.

Description

Technical Field

[0001] The invention belongs to the field of phosphor preparation, and in particular relates to the preparation and application of yellow luminescent phosphor for warm color WLED lighting. Background Art

[0002] Solid-state lighting sources have the advantages of energy saving, environmental protection, long life and small size. They have been widely used in lighting, display, communication and other fields. It is expected to replace all traditional lighting sources by 2035. At present, white light emitting diodes (WLEDs) composed of light emitting diode (LED) chips and rare earth phosphors have been widely used in our lives as the fourth generation of solid-state light sources. Most of the WLED devices on the market are composed of blue LED chips and Y3Al5O 12 :Ce 3+ However, due to the lack of red light components in the phosphor, the light emitted by this WLED device is cold, with high color temperature and poor color reproduction, which not only affects the lighting quality but also damages the user's eyesight. Therefore, it is necessary to obtain a yellow phosphor with high red light components and luminous properties to improve the lighting quality of warm color WLED.

[0003] In garnet structure phosphors, Ce 3+ The emission spectrum of the terbium aluminum garnet phosphor doped with Tb has more red components, which is due to the fact that Tb 3+ A stronger crystal field environment is formed in the lattice. In the garnet structure, Ce 3+ The 5d→4f transition of Gd is greatly affected by the local environment. Therefore, Gd with a larger ionic radius can be selected. 3+ As a sensitizing ion, Ce 3+ The emission spectrum is effectively red-shifted.

[0004] Therefore, with terbium aluminum garnet as the structural matrix, Ce 3+ and Gd 3+ The yellow luminescent phosphors prepared as activators and sensitizers have great potential in warm-color WLED devices. Their advantages are that there are more red light components in the emission spectrum, which can achieve warm-color WLED lighting with low color temperature; higher luminous intensity and internal quantum efficiency can achieve high-brightness luminescence of WLED devices; and excellent luminous thermal stability is conducive to the stable and high-brightness luminescence of WLED devices. Summary of the invention

[0005] An object of the present invention is to solve at least the above problems and / or disadvantages and to provide at least the advantages which will be described hereinafter.

[0006] In order to achieve these purposes and other advantages according to the present invention, a method for preparing a yellow luminescent phosphor for warm color WLED lighting is provided, comprising the following steps:

[0007] Step 1: Add rare earth oxide Tb4O7 into the heated HNO3 solution and stir to obtain a colorless transparent solution;

[0008] Step 2: Acid removal treatment: evaporate the colorless transparent solution, add deionized water to dissolve, repeat 2-3 times to remove excess HNO3 and make the solution pH neutral; then add deionized water to the last evaporated material to obtain a solution;

[0009] Step 3: Add Al(NO3)3·9H2O, Gd(NO3)3·6H2O, Ce(NO3)3·6H2O and citric acid to the solution obtained in step 2, stir, and then heat to react to obtain a light yellow gel;

[0010] Step 4, drying the light yellow gel and grinding it to obtain a precursor powder;

[0011] Step 5: subjecting the precursor powder to a high-temperature sintering process to obtain a yellow luminescent phosphor for warm-color WLED lighting.

[0012] Preferably, in the step 1, the volume fraction of the HNO3 solution is 30-60%; the molar volume ratio of the rare earth oxide Tb4O7 to the HNO3 solution is 0.002-0.003 mol:15-30 mL.

[0013] Preferably, in step 1, the temperature of the heated HNO3 solution is 80-95°C; and the stirring time is 0.5-1.5h.

[0014] Preferably, in the step 3, the molar ratio of rare earth oxide Tb4O7, Al(NO3)3·9H2O, Gd(NO3)3·6H2O, Ce(NO3)3·6H2O and citric acid is 0.975-2.775:0.8-8:0.05-0.15:15-25:30-35;

[0015] Preferably, in step 3, the heating reaction temperature is 75-85° C. and the time is 3-4 hours.

[0016] Preferably, in the step three, the stirred solution is subjected to pulse laser irradiation treatment using a Nd:YAG pulse laser before the heating reaction.

[0017] Preferably, the wavelength of the pulse laser irradiation treatment is 1064nm, the pulse width is 8-15ns, the pulse frequency is 10-50Hz; the single pulse energy is 5-15mJ; the temperature of the heating reaction is 75-85°C, and the time is 0.5-1 hour.

[0018] Preferably, in step 4, the drying temperature is 120-180°C.

[0019] Preferably, in step five, the heating rate of the high temperature sintering process is 5-15°C / min, the temperature is raised to 500-650°C and kept for 0.5-1.5h, then raised to 1400-1600°C and kept for 1.5-4.5h, and then naturally cooled to obtain a yellow luminescent phosphor for warm color WLED lighting.

[0020] The present invention also provides an application of the yellow luminescent phosphor prepared by the preparation method as described above in a warm color WLED device.

[0021] The present invention has at least the following beneficial effects:

[0022] The present invention uses terbium aluminum garnet as the structural matrix, Ce 3+ and Gd 3+ The yellow luminescent phosphor prepared by using the two materials as activator and sensitizer respectively has more red light components in its emission spectrum, and can realize warm-colored WLED lighting with low color temperature; the yellow luminescent phosphor has high luminous intensity and internal quantum efficiency, so that it can realize high-brightness luminescence of WLED devices; and the excellent luminescent thermal stability is conducive to the stable and high-brightness luminescence of WLED devices.

[0023] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is Ce obtained in Example 6 3+ , Gd 3+ Scanning electron microscope image of co-doped phosphor No. 6;

[0025] Figure 2 is Ce obtained in Example 6 3+ , Gd 3+ Excitation spectrum of co-doped phosphor No. 6 (emission wavelength 570nm);

[0026] Figure 3 is Ce obtained in Example 6 3+ , Gd 3+ Emission spectrum of co-doped phosphor No. 6 (excitation wavelength 465nm);

[0027] Figure 4 is Ce obtained in Example 6 3+ , Gd 3+ Variable temperature fluorescence spectrum of co-doped phosphor No. 6 (excitation wavelength 465nm);

[0028] Figure 5 is Ce obtained in Example 6 3+ , Gd 3+ Internal quantum efficiency diagram of co-doped phosphor No. 6 (REF is the test blank sample);

[0029] Figure 6 is Ce obtained from Example 6 3+ , Gd 3+ Color coordinate diagram and luminous effect diagram of WLED device composed of co-doped phosphor No. 6;

[0030] Figure 7 For Ce 3+ , Gd 3+ Excitation spectrum (emission wavelength 570 nm) of co-doped phosphor No. 1-5 (obtained in Example 1-5);

[0031] Figure 8 For Ce 3+ , Gd 3+ Emission spectrum (excitation wavelength 465 nm) of co-doped phosphor No. 1-5 (obtained in Example 1-5);

[0032] Fig. 9 is the ultraviolet absorption spectrum of the non-ion-doped phosphor (Comparative Example 1);

[0033] Fig.10 It is the emission spectrum (excitation wavelength 275nm) of the non-ion-doped phosphor (Comparative Example 7). DETAILED DESCRIPTION

[0034] The present invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0035] It should be understood that terms such as “having”, “including” and “comprising” used herein do not specify the existence or addition of one or more other elements or combinations thereof.

[0036] Embodiment 1:

[0037] Take 20 ml of 50% HNO3 solution and heat it to 90°C, weigh 0.002775 mol of rare earth oxide Tb4O7 and add it to the HNO3 solution, mix and stir for 1 hour to obtain a colorless transparent solution; evaporate the colorless transparent solution, add deionized water to dissolve, repeat 2-3 times, remove excess HNO3, and make the solution pH neutral; then add 50 mL of deionized water to the last evaporated material to obtain a solution, weigh Gd(NO3)3·6H2O, Ce(NO3)3·6H2O, The masses of Al(NO3)3·9H2O and citric acid were 0.0008 mol, 0.0001 mol, 0.02 mol and 0.032 mol, respectively, which were added to the solution and stirred for 1 h. The solution was reacted at 80 °C for 3 h to obtain a light yellow gel. The light yellow gel was dried and ground at 150 °C to obtain a precursor powder. The precursor powder was sintered at a high temperature of 10 °C / min, heated to 600 °C for 1 h, and then heated to 1500 °C for 3 h, and finally cooled naturally to obtain Ce. 3+ , Gd 3+ Co-doped phosphor No. 1; Ce 3+ , Gd 3+ The internal quantum efficiency of the co-doped phosphor No. 1 is 52.72%.

[0038] Embodiment 2:

[0039] Take 20 ml of 50% HNO3 solution and heat it to 90°C, weigh 0.002575 mol of rare earth oxide Tb4O7 and add it to the HNO3 solution, mix and stir to react for 1 hour to obtain a colorless transparent solution; evaporate the colorless transparent solution, add deionized water to dissolve, repeat 2-3 times, remove excess HNO3, and make the solution pH neutral; then add 50 mL of deionized water to the last evaporated material to obtain a solution, weigh Gd(NO3)3·6H2O, Ce(NO3)3·6H2O, The masses of Al(NO3)3·9H2O and citric acid were 0.0016 mol, 0.0001 mol, 0.02 mol and 0.032 mol, respectively, which were added to the solution and stirred for 1 h. The solution was reacted at 80 °C for 3 h to obtain a light yellow gel. The light yellow gel was dried and ground at 150 °C to obtain a precursor powder. The precursor powder was sintered at a high temperature of 10 °C / min, heated to 600 °C for 1 h, and then heated to 1500 °C for 3 h, and finally cooled naturally to obtain Ce. 3+ , Gd 3+ Co-doped phosphor No. 2; Ce 3+ , Gd 3+ The internal quantum efficiency of the co-doped phosphor No. 2 is 52.79%.

[0040] Embodiment 3:

[0041] Take 20 ml of 50% HNO3 solution and heat it to 90°C, weigh 0.002375 mol of rare earth oxide Tb4O7 and add it to the HNO3 solution, mix and stir to react for 1 hour to obtain a colorless transparent solution; evaporate the colorless transparent solution, add deionized water to dissolve, repeat 2-3 times, remove excess HNO3, and make the solution pH neutral; then add 50 mL of deionized water to the last evaporated material to obtain a solution, weigh Gd(NO3)3·6H2O, Ce(NO3)3·6H2O, The masses of Al(NO3)3·9H2O and citric acid were 0.0024 mol, 0.0001 mol, 0.02 mol and 0.032 mol, respectively, which were added to the solution and stirred for 1 h. The solution was reacted at 80 °C for 3 h to obtain a light yellow gel. The light yellow gel was dried and ground at 150 °C to obtain a precursor powder. The precursor powder was sintered at a high temperature of 10 °C / min, heated to 600 °C for 1 h, and then heated to 1500 °C for 3 h, and finally cooled naturally to obtain Ce. 3+ , Gd 3+ Co-doped phosphor No. 3. Ce 3+ , Gd 3+ The internal quantum efficiency of co-doped phosphor No. 3 is 60.64%.

[0042] Embodiment 4:

[0043] Take 20 ml of 50% HNO3 solution and heat it to 90°C, weigh 0.002175 mol of rare earth oxide Tb4O7 and add it to the HNO3 solution, mix and stir for 1 hour to obtain a colorless transparent solution; evaporate the colorless transparent solution, add deionized water to dissolve, repeat 2-3 times, remove excess HNO3, and make the solution pH neutral; then add 50 mL of deionized water to the last evaporated material to obtain a solution, weigh Gd(NO3)3·6H2O, Ce(NO3)3·6H2O, The masses of Al(NO3)3·9H2O and citric acid were 0.0032 mol, 0.0001 mol, 0.02 mol and 0.032 mol, respectively, which were added to the solution and stirred for 1 h. The solution was reacted at 80 °C for 3 h to obtain a light yellow gel. The light yellow gel was dried and ground at 150 °C to obtain a precursor powder. The precursor powder was sintered at a high temperature of 10 °C / min, heated to 600 °C for 1 h, and then heated to 1500 °C for 3 h, and finally cooled naturally to obtain Ce. 3+ , Gd 3+ Co-doped phosphor No. 4. Ce 3+ , Gd 3+The internal quantum efficiency of co-doped phosphor No. 4 is 63.02%.

[0044] Embodiment 5:

[0045] Take 20 ml of 50% HNO3 solution and heat it to 90°C, weigh 0.001475 mol of rare earth oxide Tb4O7 and add it to the HNO3 solution, mix and stir for 1 hour to obtain a colorless transparent solution; evaporate the colorless transparent solution, add deionized water to dissolve, repeat 2-3 times, remove excess HNO3, and make the solution pH neutral; then add 50 mL of deionized water to the last evaporated material to obtain a solution, weigh Gd(NO3)3·6H2O, Ce(NO3)3·6H2O, The masses of Al(NO3)3·9H2O and citric acid were 0.006 mol, 0.0001 mol, 0.02 mol and 0.032 mol, respectively, which were added to the solution and stirred for 1 h. The solution was reacted at 80 °C for 3 h to obtain a light yellow gel. The light yellow gel was dried and ground at 150 °C to obtain a precursor powder. The precursor powder was sintered at a high temperature of 10 °C / min, heated to 600 °C for 1 h, and then heated to 1500 °C for 3 h, and finally cooled naturally to obtain Ce. 3+ , Gd 3+ Co-doped phosphor No. 5. Ce 3+ , Gd 3+ The internal quantum efficiency of co-doped phosphor No. 5 is 69.39%.

[0046] Embodiment 6:

[0047] Take 20 ml of 50% HNO3 solution and heat it to 90°C, weigh 0.000975 mol of rare earth oxide Tb4O7 and add it to the HNO3 solution, mix and stir to react for 1 hour to obtain a colorless transparent solution; evaporate the colorless transparent solution, add deionized water to dissolve, repeat 2-3 times, remove excess HNO3, and make the solution pH neutral; then add 50 mL of deionized water to the last evaporated material to obtain a solution, weigh Gd(NO3)3·6H2O, Ce(NO3)3·6H2O, The masses of Al(NO3)3·9H2O and citric acid were 0.008 mol, 0.0001 mol, 0.02 mol and 0.032 mol, respectively, which were added to the solution and stirred for 1 h. The solution was reacted at 80 °C for 3 h to obtain a light yellow gel. The light yellow gel was dried and ground at 150 °C to obtain a precursor powder. The precursor powder was sintered at a high temperature of 10 °C / min, heated to 600 °C for 1 h, and then heated to 1500 °C for 3 h, and finally cooled naturally to obtain Ce. 3+ , Gd 3+ Co-doped phosphor No. 6;

[0048] Ce 3+ , Gd 3+ The scanning electron microscope image of co-doped phosphor No. 6 is as follows Figure 1 This SEM image shows that Ce 3+ , Gd 3+ Co-doped phosphor No. 6 has a uniform particle size distribution. 3+ , Gd 3+ The excitation spectrum, emission spectrum and internal quantum efficiency of co-doped phosphor No. 6 are shown in the figure below: Figure 2 , 3 and 5. The maximum excitation wavelength of the phosphor of Example 6 is 465nm, the maximum emission wavelength is 580nm, and the internal quantum efficiency is 70.14%, indicating that the Ce prepared by the present invention 3+ , Gd 3+ Co-doped phosphors have good luminescence properties, high energy utilization and high luminescence efficiency. 3+ , Gd 3+ The variable temperature fluorescence spectrum of co-doped phosphor No. 6 is as follows Figure 4 As shown, it can be seen that within the range of 25-300°C, the Ce 3+ , Gd 3+ The co-doped phosphor has excellent thermal stability of luminescence. 3+ , Gd 3+ The color coordinate diagram and luminous effect diagram of the WLED device assembled with co-doped phosphor No. 6 are shown in Figure 6 As shown, the luminescent color coordinates are (0.3726, 0.3519), indicating that Ce 3+ , Gd 3+ Co-doped phosphors are suitable for warm white lighting.

[0049] Embodiment 7:

[0050] Measure 20 ml of 50% HNO3 solution and heat it to 90°C, weigh 0.002775 mol of rare earth oxide Tb4O7 and add it to the HNO3 solution, mix and stir to react for 1 hour to obtain a colorless transparent solution; evaporate the colorless transparent solution, add deionized water to dissolve, repeat 2-3 times to remove excess HNO3 and make the solution pH neutral; then add 50 mL of deionized water to the last evaporated material to obtain a solution, weigh 0.0008 mol, 0.0001 mol, 0.02 mol, and citric acid, respectively. mol and 0.032mol were added to the solution and stirred for 1h; then the solution was irradiated with pulsed laser by Nd:YAG pulse laser for 5min (wherein the wavelength of pulsed laser irradiation was 1064nm, the pulse width was 10ns, the pulse frequency was 10Hz; the single pulse energy was 5mJ), the solution after pulsed laser irradiation was reacted at 80℃ for 1h to obtain a light yellow gel; the light yellow gel was dried and ground at 150℃ to obtain a precursor powder; the precursor powder was sintered at a high temperature of 10℃ / min; the temperature was raised to 600℃ for 1h, and then raised to 1500℃ for 3h, and finally Ce was obtained by natural cooling. 3+ , Gd 3+ Co-doped phosphor No. 7; Ce 3+ , Gd 3+ The internal quantum efficiency of co-doped phosphor No. 7 is 56.85%.

[0051] Embodiment 8:

[0052] Take 20 ml of 50% HNO3 solution and heat it to 90°C, weigh 0.000975 mol of rare earth oxide Tb4O7 and add it to the HNO3 solution, mix and stir to react for 1 hour to obtain a colorless transparent solution; evaporate the colorless transparent solution, add deionized water to dissolve, repeat 2-3 times to remove excess HNO3 and make the solution pH neutral; then add 50 mL of deionized water to the last evaporated material to obtain a solution, weigh Gd(NO3)3·6H2O, Ce(NO3)3·6H2O, Al(NO3)3·9H2O and citric acid, the masses of which are 0.008 mol, 0.0001 mol, 0.02 m ol and 0.032mol were added to the solution and stirred for 1h; then the solution was subjected to pulse laser irradiation treatment with Nd:YAG pulse laser for 5min (wherein the wavelength of the pulse laser irradiation was 1064nm, the pulse width was 10ns, the pulse frequency was 10Hz; the single pulse energy was 5mJ), the solution after pulse laser irradiation was reacted at 80℃ for 1h to obtain a light yellow gel; the light yellow gel was dried and ground at 150℃ to obtain a precursor powder; the precursor powder was sintered at a high temperature of 10℃ / min, heated to 600℃ for 1h, and then heated to 1500℃ for 3h, and finally cooled naturally to obtain Ce 3+ , Gd 3+ Co-doped phosphor No. 8, Ce 3+ , Gd 3+ The internal quantum efficiency of co-doped phosphor No. 8 is 74.78%.

[0053] Comparative Example 1:

[0054] Take 20ml of 50% HNO3 and heat it to 90℃. Weigh 0.003mol of rare earth oxide Tb4O7 and add it to HNO3. Mix and stir for 1h to obtain a colorless and transparent solution. Volatilize the solution and add deionized water to dissolve. Repeat 2-3 times to remove excess HNO3. Weigh 0.02mol and 0.032mol of Al(NO3)3·9H2O and citric acid respectively, add them to the solution and stir for 1h. React the solution at 80℃ for 3-4h to obtain a light yellow gel. Dry and grind the light yellow gel at 150℃ to obtain a precursor powder. Sinter the precursor powder at a heating rate of 10℃ / min, heat to 600℃ and keep it for 1h, then heat to 1500℃ and keep it for 3h, and finally cool it down naturally to obtain an ion-free doped phosphor. The ultraviolet absorption spectrum and emission spectrum of the ion-free doped phosphor are as follows: Fig. 9 and Fig.10 As shown in the figure, it shows that its maximum emission wavelength is 541nm, showing green light, which is not suitable for WLED device applications. 3+, Gd 3+ The emission wavelength comparison of the co-doped phosphors shows that Ce 3+ , Gd 3+ Co-doped phosphors have better luminescence properties and potential applications in the field of WLED lighting.

[0055] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A method for preparing a yellow luminescent phosphor for warm color WLED lighting, characterized in that: The following steps are involved: Step 1: Add rare earth oxide Tb4O7 into the heated HNO3 solution and stir to obtain a colorless transparent solution; Step 2: Acid removal treatment: evaporate the colorless transparent solution, add deionized water to dissolve, repeat 2-3 times to remove excess HNO3 and make the solution pH neutral; then add deionized water to the last evaporated material to obtain a solution; Step 3: Add Al(NO3)3·9H2O, Gd(NO3)3·6H2O, Ce(NO3)3·6H2O and citric acid to the solution obtained in step 2, stir, and then heat to react to obtain a light yellow gel; Step 4, drying the light yellow gel and grinding it to obtain a precursor powder; Step 5: subjecting the precursor powder to a high-temperature sintering process to obtain a yellow luminescent phosphor for warm-color WLED lighting.

2. The method for preparing the yellow luminescent phosphor for warm color WLED lighting according to claim 1, characterized in that: In the step 1, the volume fraction of the HNO3 solution is 30-60%; the molar volume ratio of the rare earth oxide Tb4O7 to the HNO3 solution is 0.002-0.003 mol:15-30 mL.

3. The method for preparing yellow luminescent phosphor for warm color WLED lighting according to claim 1, characterized in that: In the step 1, the temperature of the heated HNO3 solution is 80-95°C; and the stirring time is 0.5-1.5h.

4. The method for preparing yellow luminescent phosphor for warm color WLED lighting according to claim 1, characterized in that: In the step three, the molar ratio of rare earth oxide Tb4O7, Al(NO3)3·9H2O, Gd(NO3)3·6H2O, Ce(NO3)3·6H2O and citric acid is 0.975-2.775:0.8-8:0.05-0.15:15-25:30-35.

5. The method for preparing yellow luminescent phosphor for warm color WLED lighting according to claim 1, characterized in that: In the step 3, the heating reaction temperature is 75-85° C. and the time is 3-4 hours.

6. The method for preparing yellow luminescent phosphor for warm color WLED lighting according to claim 1, characterized in that: In the step three, the stirred solution is irradiated with pulsed laser using a Nd:YAG pulsed laser before the heating reaction.

7. The method for preparing yellow luminescent phosphor for warm color WLED lighting according to claim 6, characterized in that: The wavelength of the pulse laser irradiation treatment is 1064nm, the pulse width is 8-15ns, the pulse frequency is 10-50Hz; the single pulse energy is 5-15mJ; the temperature of the heating reaction is 75-85°C, and the time is 0.5-1 hour.

8. The method for preparing yellow luminescent phosphor for warm color WLED lighting according to claim 1, characterized in that: In the step 4, the drying temperature is 120-180°C.

9. The method for preparing yellow luminescent phosphor for warm color WLED lighting according to claim 1, characterized in that: In the step 5, the heating rate of the high temperature sintering process is 5-15°C / min, the temperature is raised to 500-650°C and kept for 0.5-1.5h, and then raised to 1400-1600°C and kept for 1.5-4.5h. After natural cooling, a yellow luminescent phosphor for warm color WLED lighting is obtained.

10. Use of the yellow luminescent phosphor prepared by the preparation method according to any one of claims 1 to 9 in a warm color WLED device.

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