Synthesis and characterization of Ce:YAG nano-phosphors and ceramics

Yttrium aluminum garnet (YAG), Y3Al5O12 is one of the most important optical materials with many applications such as optical windows, laser host materials, detectors and phosphors. Nano YAG could offer many advantageous over bulk materials and large grain size phosphors. In this work Ce doped YAG (Ce:YAG) nanophosphors (NP) were synthesized using simple chemical methods and crystalized by annealing at 800, 900 and 1100°C. Luminescence was recorded in the range of 200 to 800 nm using X-ray induced luminescence technique to detect all emission centers in the sample and evaluate their relative intensities. The effect of annealing temperature and the use of different complexing and polymerization agents on the particle morphology and luminescence were investigated. Trapping phenomena were studied in Ce:YAG NP and bulk ceramics by thermally stimulated luminescence spectroscopy and a comparison was made between them and Ce:YAG single crystals. Measurements concluded that trapping is dominated by crystal defects in single crystals and by trapping sites at the grain boundaries in ceramics. Ce:YAG NPs -on the other hand- are free of traps, which seems to be characteristic of their small grain structure. This study illustrates the effect of chemical agents and annealing temperatures on the structural and optical properties of Ce:YAG nanophosphors and shed light on the nature and characteristics of traps in YAG, which greatly affect its performance in a wide range of applications. Furthermore it reveals that different trapping mechanisms take place among single crystals, bulk ceramics and NPs which could have impact on understanding the optical and scintillation properties of various luminescent materials.