Particle Size Effects in YAG:CR Phosphors

Abstract

ABSTRACTChromium doped yttrium aluminum garnet (Y3Al5O12:Cr or YAG:Cr) phosphors were synthesized by hydrolysis of aqueous nitrate solutions. The resulting as-synthesized powder was amorphous and crystallized into the YAG structure at ~1000°C. The light output as a function of annealing temperature was found to increase with increasing temperature. Particle size, adsorbed surface species or residual impurities, lattice stability and chromium site occupation were investigated as possible explanations. It was found that there was a small decrease in lattice parameter upon annealing, the particle size increased roughly five times, and residual or adsorbed surface species were present for the low temperature annealed powders. There was no evidence that kinetic barriers to diffusion of Cr ions into the luminescent sites occurred.