Thermal stability of luminous YAG: Ce bulk ceramic as a remote phosphor prepared through silica-stabilizing valence of activator in air

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.