No abstract

A rare earth ion activated phosphor material has been successfully synthesized for the first time using a newly developed microreaction system. Control of the particle size of Y3Al5O12:Ce3+ (YAG:Ce) yellow phosphor powder has been attempted by changing the reaction space. The size can be varied between 400-1000 nm by maintaining almost the same photoluminescent performance. An internal quantum efficiency of 85% has been achieved for the YAG:Ce powder sample having an average particle size of 400 nm.

To clarify the activation procedure of Ce through the synthesis of Y3Al5O12:Ce (YAG:Ce) phosphor by a coprecipitation method, the valence state of Ce has been studied by X-ray absorption fine structure (XAFS) analysis. A linear combination of reference spectra was fit to the X-ray absorption near-edge structure (XANES) and the extended XAFS (EXAFS) oscillation curves of the oxidized samples. It was found that YAG and CeO2 are formed above 1000 °C. The fitting result indicates that Ce atoms with a concentration of about 0.6 mol % are directly incorporated into the YAG lattice upon oxidation at above 1000 °C without their segregation as CeO2. The incorporated Ce3+ ions are considered to be uniformly distributed in the YAG particles and act as efficient luminescent centers.