Synthesis and Characterization of Yttrium Aluminum Garnet Phosphors for White Light Emitting Diodes
Date Issued
2005
Date
2005
Author(s)
Lin, Yi-Shan
DOI
zh-TW
Abstract
It has been about 10 years since the company of Nichia in Japan realized the white light emitting diodes (WLEDs) by combination of the blue chip with yttrium aluminum garnet (YAG) which emits yellow color. In the past years, various methods were reported in the use of different chips and phosphors and the applications of WLEDs were also noticed in various fields. At the same time, the studies of the UV-LED with phosphors were carried out. It is expected to use the WLEDs as the ideal lighting device in 2010.
Eventhough various methods have been developed over the period of time for the construction of WLEDs, there still exists some disadvantages. Firstly, preparation of LEDs by mixing more than two different phosphors results in different levels of energy transfer efficiency and decay rate for every phosphor. Secondly, the difficulties in the improvement of UV-LED efficacy still need been examined. Even now the most stable way to produce WLEDs is the combination of the blue chip and phosphors emitting yellow light as mentioned above. Nevertheless, the energy transfer efficiency and the absorbance to different excited energy of phosphors are needed to be improved in present time.
In this work, we substituted the Tb3+ into the crystal of the yttrium aluminum garnet structure and investigated its properties. Except being as sensitizers, Tb3+ ions substitute Y3+ to form the host as the terbium-yttrium aluminum garnet structure, which influenced the emission character of activators. We also introduced fluxes in the synthesis of phosphors to change crystallite-formation processes. The flux addition during synthesis enhances the emission efficiency of phosphors which is superior to commercially available phosphor. We proposed the possible mechanisms for the transition and energy-transfer process of electrons by the investigation of VUV-PL spectra, low-temperature PL spectra, and solid state NMR spectra.
In this work, we utilized X-ray diffraction (XRD) to investigate the crystal phase and long range ordering. In regard to the luminescent properties such as excitation and emission spectra, photoluminescence spectrometer (PL) was used. We also investigated luminescent properties by PL spectra excited by VUV synchrotron radiation source and the PL spectra at low temperature to study the energy transfer processes. The SEM was used to analysis the particle size and morphology of phosphors. The TGA/DSC analyses were performed to examine the weight lost process and chemical reactions during the heat treatment. We also utilized the SS.-NMR to investigate the coordination environments of critical elements. Some results of this study are already published in J. Electrochem. Soc. [152, J41 (2005)]. Three more manuscripts are under preparation (Chem. Mater.; J. Electrochem. Soc.; J. Lumin.) and four patents have been filed from the outcome of results.
Eventhough various methods have been developed over the period of time for the construction of WLEDs, there still exists some disadvantages. Firstly, preparation of LEDs by mixing more than two different phosphors results in different levels of energy transfer efficiency and decay rate for every phosphor. Secondly, the difficulties in the improvement of UV-LED efficacy still need been examined. Even now the most stable way to produce WLEDs is the combination of the blue chip and phosphors emitting yellow light as mentioned above. Nevertheless, the energy transfer efficiency and the absorbance to different excited energy of phosphors are needed to be improved in present time.
In this work, we substituted the Tb3+ into the crystal of the yttrium aluminum garnet structure and investigated its properties. Except being as sensitizers, Tb3+ ions substitute Y3+ to form the host as the terbium-yttrium aluminum garnet structure, which influenced the emission character of activators. We also introduced fluxes in the synthesis of phosphors to change crystallite-formation processes. The flux addition during synthesis enhances the emission efficiency of phosphors which is superior to commercially available phosphor. We proposed the possible mechanisms for the transition and energy-transfer process of electrons by the investigation of VUV-PL spectra, low-temperature PL spectra, and solid state NMR spectra.
In this work, we utilized X-ray diffraction (XRD) to investigate the crystal phase and long range ordering. In regard to the luminescent properties such as excitation and emission spectra, photoluminescence spectrometer (PL) was used. We also investigated luminescent properties by PL spectra excited by VUV synchrotron radiation source and the PL spectra at low temperature to study the energy transfer processes. The SEM was used to analysis the particle size and morphology of phosphors. The TGA/DSC analyses were performed to examine the weight lost process and chemical reactions during the heat treatment. We also utilized the SS.-NMR to investigate the coordination environments of critical elements. Some results of this study are already published in J. Electrochem. Soc. [152, J41 (2005)]. Three more manuscripts are under preparation (Chem. Mater.; J. Electrochem. Soc.; J. Lumin.) and four patents have been filed from the outcome of results.
Subjects
白光發光二極體
螢光粉
WLED
phosphor
YAG
Type
thesis
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