Preparation of cerium-activated GAG phosphor powders influence of Co-doping on crystallinity and luminescent properties

An impure-phase GdAlO3 usually remains in the product of gadolinium aluminum garnet (GAG) powder as synthesized. In this study, an attempt to prepare a stable GAG pure-phase powder by substituting small cations (Tb3+, Y3+, or Lu3+) at the dodecahedral sites or the substituting the large cation (Ga3+) for the Al3+ sites of the garnet structure was made. Pure garnet-phase GAG powder was formed by calcining at 1500 C for 2 h. It was found that increasing the Lu3+ content in the Gd3+ lattice site of the dodecahedral or increasing the Ga3+ content in the Al3+ site induces a blue shift in the emission wavelength. The color temperature of the pure GAG:Ce(YAG:Ce) phosphor powder (similar to 2900 K) formed was lower than that of yttrium aluminum garnet and terbium aluminum garnet (TAG: Ce) phosphors. (c) 2007 The Electrochemical Society.