Abstract
In a phosphor synthesis of Y_3Al_5O_<12>:Ce (YAG:Ce) by a liquid phase reaction method, the state of Ce in precursors, intermediate products and completed phosphors are systematically investigated by X-ray Absorption Fine Structure (XAFS) measurement. It has been found out that Ce is initially trivalent in the precursor. However, most of Ce are oxidized and might be segregated as an amorphous tetravalent cerium oxide from the yttrium compounds by firing in air atmosphere. By contrast, Eu stably remains at Y sites as trivalent even fired in air atmosphere. It concludes that the redox activity of luminescent centers dominates the incorporation of them into host lattices.
