Thermal stability of luminous YAG: Ce bulk ceramic as a remote phosphor prepared through silica-stabilizing valence of activator in air
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Abstract:
A prototype of YAG: Ce (Y3Al5O12) luminous bulk ceramic as a remote phosphor for white LED illumination was fabricated in air through a strategy of silica addition. With increasing the amount of silica in a specific range, the opaque sample turns to be semi-transparent. The precipitation of crystals is verified to be in pure YAG phase by X-ray diffraction (XRD). Beyond the limit of silica amount, the dominant phase of YAG crystal is found to coexist with a small amount of newly-formed Y2Si2O7, Al2O3 and the amorphous phase. The YAG crystals are with a grain size of approximately 2 μm and distribute evenly. The YAG hosts after structural modification via addition of silica result in yellow band emission of 5d → 4f transition peaked around 535 nm as excited by a blue LED, owing to the self-reduction of Ce4+ to Ce3+ even in the absence of reductive atmosphere.
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This work has been supported by the National Natural Science Foundation of China (Nos.50872091, 50802062, and 21076161), and the Key Discipline for Materials Physics and Chemistry of Tianjin in China (Nos.10SYSYJC28100, 2006ZD30, and 06YFJMJC0230)
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