Abstract

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 °C) compared to YAG∶Ce³⁺ samples prepared by the conventional solid-state reaction method at 1450 °C. 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.