Preparation of Cerium-Activated GAG Phosphor Powders

An impure-phase GdAlO 3 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 ( Tb 3 + , Y 3 + , or Lu 3 + ) at the dodecahedral sites or the substituting the large cation ( Ga 3 + ) for the Al 3 + 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 Lu 3 + content in the Gd 3 + lattice site of the dodecahedral or increasing the Ga 3 + content in the Al 3 + site induces a blue shift in the emission wavelength. The color temperature of the pure GAG : Ce (YAG:Ce) phosphor powder ( ∼ 2900 K ) formed was lower than that of yttrium aluminum garnet and terbium aluminum garnet (TAG:Ce) phosphors.