研究目的
To fabricate and characterize monodispersed SiO2@SrAl2Si2O8:Eu2+ core-shell submicron spherical phosphors using a sol-gel method, and to study their structural, morphological, and photoluminescent properties.
研究成果
Monodispersed SiO2@SrAl2Si2O8:Eu2+ core-shell spherical phosphors were successfully fabricated with uniform size and spherical morphology. The photoluminescence intensity, dominated by Eu2+ emission at 390 nm, increased with higher annealing temperatures due to improved crystallinity. This method offers advantages in controlling morphology and size for various phosphor applications.
研究不足
The FESEM images could not resolve the core-shell structure due to low magnification, and the coating thickness was not uniform, especially at higher annealing temperatures. The method may have limitations in scalability or cost for industrial applications.
1：Experimental Design and Method Selection:
The study employed a Pechini-type sol-gel process to coat SrAl2Si2O8:Eu2+ phosphor layers on silica spheres, chosen for its ability to produce uniform coatings and control crystallinity through annealing.
2：Sample Selection and Data Sources:
Silica spheres (450-500 nm) were synthesized via the St?ber method using tetraethoxysilane (TEOS), water, and ammonium hydroxide. The core-shell particles were prepared with specific molar ratios of Eu(OOCCH3)3·2H2O and citric acid.
3：List of Experimental Equipment and Materials:
Equipment included a transmission electron microscope (TEM, Hitachi H-800), field-emission scanning electron microscope (FESEM, Hitachi S-4700), X-ray diffractometer (XRD, D/Max2500VB2 + PC), and fluorometer (Hitachi F4600). Materials included TEOS (99 wt.%, analytical reagent), NH4OH (25 wt.%, analytical reagent), Eu(OOCCH3)3·2H2O (99%), citric acid, ethanol, water, and HNO
4：0). Materials included TEOS (99 wt.%, analytical reagent), NH4OH (25 wt.%, analytical reagent), Eu(OOCCH3)3·2H2O (99%), citric acid, ethanol, water, and HNOExperimental Procedures and Operational Workflow:
3. 4. Experimental Procedures and Operational Workflow: Silica spheres were synthesized, centrifuged, and washed. For core-shell synthesis, Eu(OOCCH3)3·2H2O and citric acid were dissolved in an ethanol-water mixture, catalyzed with HNO3, mixed with silica particles, dried at 140°C, preheated at 500°C, and annealed at 800-1000°C for 2 hours. Characterization involved XRD, SEM, TEM, and photoluminescence measurements.
5：Data Analysis Methods:
XRD patterns were compared with JCPDS standards; SEM and TEM images were analyzed for morphology and size; photoluminescence spectra were measured and intensities compared across annealing temperatures.
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Transmission Electron Microscope
H-800
Hitachi
Used to observe the morphology and microstructure of the samples, particularly to resolve the core-shell structure.
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Field-Emission Scanning Electron Microscope
S-4700
Hitachi
Used to provide images of the sample morphology at a larger scale, though it could not resolve the core-shell structure due to low magnification.
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Fluorometer
F4600
Hitachi
Used to measure photoluminescence spectra, with energy correction for data collection.
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X-ray Diffraction Apparatus
D/Max2500VB2 + PC
Used to carry out XRD spectra to analyze the crystallinity and phase composition of the samples.
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Tetraethoxysilane
Used as a reagent in the St?ber method to synthesize silica spheres.
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Ammonium Hydroxide
Used as a reagent in the St?ber method to synthesize silica spheres.
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Europium Acetate Hydrate
Used as a source of Eu ions in the sol-gel process for coating the phosphor layers.
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