Purple light excited silicate cyan fluorescent material and preparation method thereof

Abstract

The invention relates to a purple light excited silicate cyan fluorescent material and a preparation method thereof. The chemical formula of the purple light excited silicate cyan fluorescent material is Ba9Lu2-x-nCexSi6O24-3n / 2, wherein x is more than 0 and less than 2, n is more than 0 and less than or equal to 1, and x + n is more than 0 and less than 2.

Description

Technical Field

[0001] The present invention relates to a violet-excited silicate cyan fluorescent material and a preparation method thereof, belonging to the technical field of luminescent materials and their preparation. Background Art

[0002] Solid-state lighting devices based on light-emitting diodes (LEDs) have achieved great development as alternatives to traditional incandescent lamps and fluorescent lamps, due to their advantages such as environmental protection, energy conservation, high efficiency, and long lifespan. In recent years, phosphor-converted white LEDs (pc-wLEDs) have been widely used in the display and lighting fields because of their wide tunable spectra and excellent color rendering index (CRI). Currently, the most common method to achieve pc-wLEDs is to use a blue InGaN chip to excite YAG:Ce 3+ yellow phosphor. However, the low color rendering index (Ra < 80) caused by the lack of red spectral components limits its application, and the blue light emitted by the blue chip participating in white light synthesis affects the human retina and biological rhythm to a certain extent, which is called "blue light hazard". In order to obtain high-quality white light, it is a feasible solution to use a violet chip and a combination of multi-color phosphors (blue / green / red) to prepare high-quality pc-wLEDs, simulate the solar spectrum, and meet the requirements for healthy lighting. However, there is still a lack of cyan light in this spectrum at present, that is, the so-called "cyan gap" (480 - 520 nm). Therefore, developing suitable cyan phosphors that match well with violet chips is crucial for high-quality pc-wLEDs in healthy lighting applications and is the key challenge for obtaining high-quality full-spectrum lighting.

[0003] Regarding violet-excited cyan fluorescent materials, related research at home and abroad is still in continuous development. Zhong et al. (Chem. Mater., 2020, 32(2): 882 - 888.) reported that the doped Ce 3 :Ce 3+ ions in monoclinic NaMgBO 3+ occupy non-equivalent Na + lattice sites, introducing anti-site defects. Under near-ultraviolet light excitation at a wavelength of 370 nm, the main emission peak is located at 480 nm blue-cyan light. Combining a 370 nm near-ultraviolet chip with blue-cyan powder NaMgBO 3 :Ce 3+ , green powder β-SiAlON:Eu 2+ , and red powder CaAlSiN 3 :Eu 2 + , a full-spectrum white LED prototype device was obtained, with a color rendering index of 91.0, color coordinates of (0.399, 0.390), and a color temperature of 3645K.

[0004] Strobel et al. (Chem. Mater., 2018, 30(9): 3122 - 3130.) reported that Sr[Be 6 ON 4 :Eu 2+ Under the excitation of violet light with a wavelength of 410 nm, it emits cyan light with a main emission peak at 495 nm, a full width at half maximum of 35 nm, a quantum efficiency of 20%, and the luminous intensity remains 90% of that at room temperature at 275 °C. However, this cyan powder contains highly toxic Be element.

[0005] In recent years, some garnet - structured cyan fluorescent materials have attracted wide attention. Wang et al. (J. Phys. Chem. C, 2015, 119(28): 16208 - 16214.) reported that the garnet - structured Ca 2 YZr 2 Al 3 O 12 :Ce 3+ Under the excitation of violet light with a wavelength of 410 nm, it emits cyan and green light with main emission peaks at 484 - 503 nm, an internal quantum efficiency of 56%, and the luminous intensity remains 62% of that at room temperature at 150 °C. Ding et al. (Crystengcomm, 2015, 17(17): 3235 - 3242.) reported that the garnet - structured Ca 3 Hf 2 SiAl 2 O 12 :Ce 3+ Under the excitation of violet light with a wavelength of 400 nm, it emits cyan and green light with main emission peaks at 481 - 508 nm, and the luminous intensity reaches 68.9% of that of commercial Y 3 Al 5 O 12 :Ce (YAG:Ce), with a quantum efficiency of 74.7%, and the luminous intensity remains 57.8% of that at room temperature at 250 °C.

[0006] The key to improving the spectral continuity and color rendering property lies in that for the full - spectrum healthy lighting similar to sunlight excited by a violet - light chip, high - performance violet - light - excited cyan fluorescent materials are needed to fill the cyan gap. However, the currently reported violet - light - excited cyan fluorescent materials all have performance defects to a certain extent. Therefore, it is crucial to develop high - quality cyan fluorescent materials suitable for excitation by violet - light chips with high quantum efficiency, good structural and thermal stability, and low cost. Summary of the Invention

[0007] The purpose of the present invention is to provide a violet - light - excited silicate cyan fluorescent material and its preparation method, aiming to improve the spectral continuity and enhance the color rendering index of white LEDs.

[0008] On the one hand, the present invention provides a violet-excited silicate cyan fluorescent material, and the chemical formula of the violet-excited silicate cyan fluorescent material is Ba 9 Lu 2-x-n Ce x Si 6 O 24-3n / 2 , where 0 < x < 2, 0 < n ≤ 1 and 0 < x + n < 2.

[0009] In the present invention, the provided cyan fluorescent material Ba 9 Lu 2-x-n Ce x Si 6 O 24-3n / 2 , based on defect engineering, by creating Lu vacancies, inducing more Ce ions to occupy the Lu lattice sites, effectively enhances the cyan emission intensity of the material, improves the fluorescence quantum efficiency, and enhances the thermal stability. The violet-excited cyan powder Ba 9 Lu 2-x-n Ce x Si 6 O 24-3n / 2 has significant advantages in improving the continuity of the spectrum of violet-excited white LEDs and enhancing the color rendering index, and is a novel and efficient cyan fluorescent powder for healthy lighting full-spectrum white LEDs. Preferably, 0 < x ≤ 0.5, 0 < n ≤ 0.5

[0010] Preferably, the luminescence center is Ce 3+ , and Ce 3+ occupies both the Ba lattice site and the Lu lattice site simultaneously.

[0011] Preferably, before introducing Lu vacancies, the atomic ratio of Ce 3+ occupying the Lu lattice site to Ce 3+ occupying the Ba lattice site is 1:(1 - 4), and after introducing Lu vacancies, the atomic ratio of Ce 3+ occupying the Lu lattice site to Ce 3+ occupying the Ba lattice site is 1:(0.5 - 1.5).

[0012] Preferably, Ce 3+ occupying the Ba lattice site emits ultraviolet light with an emission center wavelength of 385 nm under ultraviolet light excitation at a wavelength of 325 nm; Ce 3+ occupying the Lu lattice site emits cyan light with an emission center wavelength of 485 nm under violet light excitation at a wavelength of 395 nm.

[0013] On the other hand, the present invention provides a preparation method of a violet-excited silicate cyan fluorescent material, including: using Ba source, Lu source, Si source, and Ce source as raw materials, weighing and mixing according to the stoichiometric ratio, pre-calcining in an air atmosphere first, and then performing secondary calcining in a reducing atmosphere to obtain the violet-excited silicate cyan fluorescent material.

[0014] Preferably, the Ba source is BaCO 3 or Ba(NO 3 ) 2 , with a purity ≥ 99.9%; The Lu source is at least one of Lu 2 O 3 , the carbonate of Lu, and the nitrate of Lu, with a purity ≥ 99.99%; The Si source is SiO 2 , with a purity ≥ 99.9%; The Ce source is at least one of CeO 2 , the carbonate of Ce, and the nitrate of Ce, with a purity ≥ 99.99%.

[0015] Preferably, the temperature of the pre-calcination is 400 - 800 °C, and the calcination time is 1 - 5 hours.

[0016] Preferably, the temperature of the secondary calcination is 1300 - 1600 °C, the secondary calcination time is 2 - 8 hours, and it is taken out after cooling to room temperature to obtain the silicate cyan fluorescent material.

[0017] Advantages of the present invention: The cyan fluorescent material Ba 9 Lu 2-x-n Ce x Si 6 O 24-3n / 2 provided by the present invention is characterized in that, based on defect engineering, by creating Lu vacancies, more Ce ions are induced to occupy the Lu lattice sites, effectively enhancing the cyan emission intensity of the material, improving the fluorescence quantum efficiency, and enhancing the thermal stability. The violet light excitation of the cyan powder Ba 9 Lu 2-x-n Ce x Si 6 O 24-3n / 2 has significant advantages in improving the continuity of the violet light excitation white LED spectrum and enhancing the color rendering index, and it is a novel and efficient cyan fluorescent powder for healthy lighting full-spectrum white LEDs. Description of the Drawings

[0018] Figure 1 is the emission spectrum of Ba 9 Lu 2-x Ce x Si 6 O 24 doped with different concentrations of Ce ions (0 < x ≤ 1) under 325 nm violet light excitation; Figure 2 is Ba 9 Lu2-x Ce x Si 6 O 24 (0 < x ≤ 1) The excitation spectrum monitored by light at a wavelength of 385 nm; Figure 3 For Ba doped with different concentrations of Ce ions 9 Lu 2-x Ce x Si 6 O 24 (0 < x ≤ 1) The emission spectrum under excitation by 395 nm violet light; Figure 4 For Ba doped with different concentrations of Ce ions 9 Lu 2-x Ce x Si 6 O 24 (0 < x ≤ 1) The excitation spectrum monitored by light at a wavelength of 485 nm; Figure 5 For Ba doped with different concentrations of Ce ions 9 Lu 2-x Ce x Si 6 O 24 (0 < x ≤ 1) Histogram of the integrated intensity of the emission spectrum under excitation by 395 nm violet light; Figure 6 For samples of n-Ba with different concentrations of Lu vacancies 9 Lu 1.7-n Ce 0.3 Si 6 O 24-3n / 2 (0 ≤ n ≤ 0.5) The emission spectrum under excitation by 395 nm violet light; Figure 7 For samples of n-Ba with different concentrations of Lu vacancies 9 Lu 1.7-n Ce 0.3 Si 6 O 24-3n / 2 (0 ≤ n ≤ 0.5) The excitation spectrum monitored by light at a wavelength of 485 nm; Figure 8 For samples of n-Ba with different concentrations of Lu vacancies 9 Lu 1.7-n Ce 0.3 Si 6 O 24-3n / 2 (0 ≤ n ≤ 0.5) Histogram of the integrated intensity of the emission spectrum under excitation by 395 nm violet light; Figure 9 For n-Ba before and after introducing Lu vacancies 0 -Ba 9 Lu 1.7-n Ce0.3 Si 6 O 24 and n 0.3 -Ba 9 Lu 1.7-n Ce 0.3 Si 6 O 23.55 Variation in the proportion of Ce ions occupying Ba sites and Lu sites; Figure 10 For Ba 9 Lu 2-x Ce x Si 6 O 24 (0 ≤ x ≤ 1) X-ray diffraction patterns and the standard diffraction pattern of pure-phase Ba 9 Sc 2 Si 6 O 24 (X-ray diffraction standard card PDF No. 82-1119); Figure 11 For samples of n-Ba 9 Lu 1.7-n Ce 0.3 Si 6 O 24-3n / 2 (0 ≤ n ≤ 0.5) X-ray diffraction patterns and the standard diffraction pattern of pure-phase Ba 9 Sc 2 Si 6 O 24 (X-ray diffraction standard card PDF No. 82-1119); Figure 12 Before and after introducing Lu vacancies, for n 0 -Ba 9 Lu 1.7 Ce 0.3 Si 6 O 24 and n 0.3 -Ba 9 Lu 1.4 Ce 0.3 Si 6 O 23.55 Quantum efficiency comparison; Figure 13 Before and after introducing Lu vacancies, for n 0 -Ba 9 Lu 1.7 Ce 0.3 Si 6 O 24 and n 0.3 -Ba 9 Lu 1.4Ce 0.3 Si 6 O 23.55 Thermal stability comparison; Figure 14 For the spectrum (upper) of the white LED made by combining a violet chip with blue, green, and red phosphors, and for the spectrum (lower) of the white LED made by combining a violet chip with blue, green, red phosphors and n 0.3 -Ba 9 Lu 1.4 Ce 0.3 Si 6 O 23.55 cyan powder; Figure 15 For Figure 14 the chromaticity coordinate diagram and device photo of the white LED device in Detailed implementation manners

[0019] The present invention will be further described below through the following implementation manners. It should be understood that the following implementation manners are only used to illustrate the present invention and do not limit the present invention.

[0020] In the present disclosure, the chemical formula of the violet-excited silicate cyan fluorescent material is Ba 9 Lu 2-x-n Ce x Si 6 O 24-3n / 2 , where 0 < x < 2, 0 < n ≤ 1 and 0 < x + n < 2.

[0021] In the present invention, the violet-excited cyan fluorescent material is prepared by the high-temperature solid-phase method. The preparation method of the violet-excited cyan fluorescent material provided by the present invention will be exemplarily described below.

[0022] Weigh commercially available BaCO 3 , Lu 2 O 3 , SiO 2 , CeO 2 powders according to the corresponding stoichiometric ratios, grind them in an agate mortar for half an hour, and use the uniformly mixed powders as the raw material powders. For example, commercially available BaCO 3 (99.99%), Lu 2 O 3 (99.99%), SiO 2 (99.99%) CeO 2 (99.99%) powders are used as the raw materials.

[0023] Pre-calcine the raw material powders in an air atmosphere at 400 - 800 °C for 1 - 5 hours. Its function is to decompose carbonates or nitrates into oxides to obtain calcined powders.

[0024] Then, it is calcined at 1300 - 1600 °C for 2 - 10 hours in a reducing atmosphere, which serves to fully react the oxides to form phases. Subsequently, it is taken out when cooled to room temperature to obtain a violet - light - excited silicate cyan fluorescent powder.

[0025] The following further gives examples to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be construed as limiting the protection scope of the present invention. Some non - essential improvements and adjustments made by those skilled in the art based on the above content of the present invention fall within the protection scope of the present invention. The specific process parameters and the like in the following examples are also only an example within a suitable range, that is, those skilled in the art can make selections within a suitable range according to the description herein, rather than being limited to the specific values in the following examples.

[0026] Example 1 (Determining the optimal concentration of Ce ion doping) Using commercially available BaCO 3 , Lu 2 O 3 , SiO 2 , CeO 2 powders as raw materials, proportioned according to the stoichiometric ratio of Ba 9 Lu 2-x Ce x Si 6 O 24 , grinding in an agate mortar for half an hour, and after mixing evenly, it is used as the raw material powder. The raw material powder is calcined at 600 °C for 4 hours in an air atmosphere; then it is calcined at 1450 °C for 6 hours in a reducing atmosphere of N 2 / H 2 (N 2 :H 2 = 95%:5%), and taken out when cooled to room temperature to obtain a series of samples of Ba 9 Lu 2-x Ce x Si 6 O 24 (0 < x ≤ 1).

[0027] Figure 1 and Figure 2 are the emission spectra of a series of samples of Ba 9 Lu 2-x Ce x Si 6 O 24 (0 < x ≤ 1) under 325 nm ultraviolet light excitation, and the excitation spectra monitored at 385 nm wavelength ultraviolet light, originating from Ce 3+ ions occupying the Ba lattice sites; Figure 3 and Figure 4Samples of Ba doped with different concentrations of Ce ions in series 9 Lu 2-x Ce x Si 6 O 24 (0 < x ≤ 1) The emission spectra under 395 nm violet light excitation and the excitation spectra monitored at 485 nm wavelength blue light, which originate from Ce 3+ ions occupying the Lu lattice sites. Figure 5 Samples of Ba doped with different concentrations of Ce ions 9 Lu 2-x Ce x Si 6 O 24 (0 < x ≤ 1) Histogram of the integrated intensity of the emission spectra under 395 nm violet light excitation, indicating that the blue emission is the strongest when the Ce ion doping concentration x is 0.3. Samples of Ba doped with different concentrations of Ce ions in series 9 Lu 2-x Ce x Si 6 O 24 (00 < x ≤ 1) The X-ray diffraction patterns are as Figure 10 shown and are basically consistent with the standard diffraction pattern of Ba 9 Sc 2 Si 6 O 24 Next, fix the Ce ion doping concentration x at 0.3 and continue to study the regulation of the luminescence properties by introducing Lu vacancies on the basis of Ba 9 Lu 1.7 Ce 0.3 Si 6 O 24 .

[0028] Example 2 (Introducing Lu vacancies improves the luminescence intensity of the material) Weigh commercially available BaCO 3 , Lu 2 O 3 , CeO 2 , SiO 2 powders and weigh them according to the molar ratio of 9:(1.7 - n) / 2:0.3:6 (n is 0, 0.1, 0.2, 0.3, 0.4, 0.5 respectively). Grind them in an agate mortar for half an hour, and after mixing evenly, use them as the raw material powder. Calcinate the raw material powder in an air atmosphere at 600 °C for 4 hours; then calcinate it in a reducing atmosphere of N 2 / H 2 (N 2 :H 2 = 95%:5%) at 1450 °C for 6 hours, take it out when cooled to room temperature, and obtain the blue fluorescent powder Ba 9 Lu1.7- n Ce 0.3 Si 6 O 24-3n / 2 , for the convenience of identifying the doping of Lu vacancies, labeled as n-Ba 9 Lu 1.7-n Ce 0.3 Si 6 O 24-3n / 2 .

[0029] As Figure 6 and Figure 7 series of n-Ba samples with different concentrations of Lu vacancies 9 Lu 1.7-n Ce 0.3 Si 6 O 24-3n / 2 (0 ≤ n ≤ 0.5) as shown by the emission spectrum under 395 nm violet light excitation and the excitation spectrum monitored at 485 nm wavelength blue light, the introduction of Lu vacancies enhances the emission spectrum intensity and excitation spectrum intensity of n-Ba 9 Lu 1.7-n Ce 0.3 Si 6 O 24-3n / 2 , and reaches the maximum value when the Lu vacancy concentration n is 0.3.

[0030] n-Ba samples with different concentrations of Lu vacancies 9 Lu 1.7-n Ce 0.3 Si 6 O 24-3n / 2 (0 ≤ n ≤ 0.5) the histogram of the integrated intensity of the emission spectrum under 395 nm violet light excitation is as Figure 8 shown, compared with the sample n 0 -Ba 9 Lu 1.7 Ce 0.3 Si 6 O 24-3n / 2 without the introduction of Lu vacancies, the emission intensity of the sample n-Ba 9 Lu 1..7-n Ce 0.3 Si 6 O 24-3n / 2 with Lu vacancies introduced is significantly increased. When the Lu vacancy concentration n is 0.1, 0.2, 0.3, 0.5, it is increased by 1.08 times, 1.27 times, 1.47 times, 1.13 times respectively.

[0031] The histograms of the ratios of Ce ions occupying Ba lattice sites and Lu lattice sites before and after the introduction of Lu vacancies are as Figure 9As shown, the introduction of Lu vacancies induces more Ce ions to occupy the Lu lattice sites, that is, the concentration of Ce ions occupying the cyan emission sites increases, so the cyan emission intensity is enhanced.

[0032] As Figure 11 shown, the X-ray diffraction patterns of a series of samples of n-Ba 9 Lu 1.7-n Ce 0.3 Si 6 O 24-3n / 2 (0 ≤ n ≤ 0.5) are basically consistent with the standard diffraction pattern of Ba 9 Sc 2 Si 6 O 24 .

[0033] The quantum efficiency measured by a Zolix instrument is as Figure 12 shown, the quantum efficiency of n 0.3 -Ba 9 Lu 1.4 Ce 0.3 Si 6 O 23.55 is 54.5%, and the quantum efficiency of Ba 9 Lu 1.7 Ce 0.3 Si 6 O 24 is 40.9%, indicating that the introduction of Lu vacancies improves the quantum efficiency of the material.

[0034] The line graphs of the emission spectral intensities of the samples of n-Ba 9 Lu 1.7-n Ce 0.3 Si 6 O 24-3n / 2 (n = 0, 0.3) as a function of temperature under 395 nm violet light excitation are as Figure 13 shown, the emission intensity of n 0.3 -Ba 9 Lu 1.4 Ce 0.3 Si 6 O 23.55 at 423 K remains at 96% of the initial intensity at room temperature, higher than 88% of Ba 9 Lu 1.7 Ce 0.3 Si 6 O 24 , indicating that the introduction of Lu vacancies improves the thermal stability of the luminescence of the material.

[0035] Example 3 (Demonstration of White LED Application) To verify n 0.3-Ba 9 Lu 1.4 Ce 0.3 Si 6 O 23.55 For the application potential of 0.3 -Ba 9 Lu 1.4 Ce 0.3 Si 6 O 23.55 , two white light LED prototype devices were fabricated for comparative study. The spectrum of white light LED1 (upper) fabricated by combining a violet chip with blue, green, and red phosphors, and the spectrum of white light LED2 (lower) fabricated by combining a violet chip with blue, green, red phosphors and cyan powder are as Figure 14 shown, indicating that after adding the cyan fluorescent material 0.3 -Ba 9 Lu 1.4 Ce 0.3 Si 6 O 23.55 , the cyan gap in the spectrum of white light LED2 is effectively supplemented, and at the same time, the color rendering index Ra is increased from 87.9 to 94.5. The CIE chromaticity coordinates and the corresponding digital photos of the two LED devices under a current of 40 mA and a driving voltage of 3 V are as Figure 15 shown. The CIE chromaticity coordinates of LED1 are (0.3530, 0.3516), and the CIE chromaticity coordinates of LED2 are (0.3386, 0.3875).

[0036] Industrial applicability: In Ce-ion doped Ba 9 Lu 2 Si 6 O 24 , Ce ions can occupy the Ba lattice sites and Lu lattice sites. Regarding the characteristic that Ce ions occupying the Lu lattice sites can be effectively excited by violet light to generate cyan light emission, through lattice site engineering and defect engineering, Lu vacancies are introduced to induce more Ce ions to occupy the Lu lattice sites, that is, the concentration of Ce 3+ occupying the cyan light-emitting sites increases, effectively enhancing the luminescence intensity of the material, improving the fluorescence quantum efficiency, and enhancing the thermal stability. Ba 9 Lu 2-x- n Ce x Si 6 O 24-3n / 2 emits cyan light with an emission center wavelength of 485 nm under the excitation of 395 nm wavelength violet light, which has significant advantages for improving the spectral continuity and color rendering index of violet light-excited white light LEDs. The preparation process is clean and pollution-free, and it is suitable for large-scale production.

Claims

1. A violet light excited silicate cyan fluorescent material, characterized in that: The chemical formula of the violet light excited silicate cyan fluorescent material is Ba9Lu 2-x-n Ce x SiO 24-3n / 2 , where 0<x<2, 0<n≤1 and 0<x+n<2.

2. The violet light excited silicate cyan fluorescent material according to claim 1, characterized in that: 0<x≤0.5, 0<n≤0.

5.

3. The violet light excited silicate cyan fluorescent material according to claim 1, characterized in that: The Ce element is the luminescence center Ce 3+ , and Ce 3+ Occupies both the bag and the bag position.

4. The violet light excited silicate cyan fluorescent material according to claim 1, characterized in that: Before the Lu vacancy is introduced, Ce occupying the Lu position 3+ and Ce which occupies eight positions 3+ The atomic ratio of is 1:(1~4). After the Lu vacancy is introduced, Ce occupying the Lu lattice site 3+ and Ce which occupies eight positions 3+ The atomic ratio is 1:(0.5~1.5).

5. The silicon violet light-excited salt cyan fluorescent material according to claim 3 or 4, characterized in that: Ce occupies eight positions 3+ Under the excitation of 325nm ultraviolet light, it emits ultraviolet light with a central wavelength of 385nm; Ce occupying the Lu position 3+ When excited by 395nm violet light, it emits cyan light with a central wavelength of 485nm.

6. A method for preparing a violet light excited silicate cyan fluorescent material as claimed in any one of claims 1 to 5, characterized in that: include: Ba source, Lu source, Si source and Ce source are used as raw materials, weighed and mixed according to a stoichiometric ratio, pre-calcined in an air atmosphere, and then secondary calcined in a reducing atmosphere to obtain the violet light excited silicate cyan fluorescent material.

7. The preparation method according to claim 6, characterized in that: The Ba source is BaCO3 or Ba(NO3)2, with a purity of ≥99.9%; The Lu source is at least one of Lu2O3, Lu carbonate and Lu nitrate, with a purity of ≥99.99%; The Si source is SiO2, with a purity of ≥99.9%; The Ce source is at least one of CeO2, Ce carbonate and Ce nitrate, and the purity is ≥99.99%.

8. The preparation method according to claim 6 or 7, characterized in that: The pre-calcination temperature is 400-800° C., and the calcination time is 1-5 hours.

9. The preparation method according to any one of claims 6 to 8, characterized in that: The temperature of the secondary calcination is 1300-1600° C., the time of the secondary calcination is 2-8 hours, and the material is taken out after cooling to room temperature to obtain the violet light excited silicate cyan fluorescent material.

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