Sol-gel synthesis and photoluminescent properties of cerium-ion doped yttrium aluminium garnet powders

Luminescent Y3Al5O12:Ce3+ (YAG:Ce3+) ceramics with nanometer- to micronmeter-sized particles were prepared by a new sol-gel pyrolysis method. Notwithstanding thermochemical considerations, the combined fuel system of urea and poly(vinyl alcohol) (PVA) yielded nanoparticles exhibiting single-crystal features. This can be attributed to the pyrolysis of sols trapped within the cages formed by the cross-linking of PVA chains in the presence of urea. Another salient feature of this investigation is the higher luminescence yield for YAG:Ce3+ samples prepared using only urea as the fuel at much lower temperature (1000¢XC) compared to YAG: Ce3+ samples prepared by the conventional solid-state reaction method at 1450¢XC. In addition, the partial aliovalent substitution of Y3+ by Ba2+ in this important luminescent ceramic results in new defect complexes serving as precursors for the generation of excitons. Under band-edge photoexcitation, the excitons thus generated can resonate with excited levels of Ce3+ which have a profound dependence on the particle size.