A polymer solution process for synthesis of (Y,Gd)3Al5O12:Ce phosphor particles

Cerium-doped yttrium-gadolinium aluminum garnet, (Y,Gd)3Al5O12:Ce, shortened here to (Y,Gd)AG:Ce, was systematically prepared by a polymer complex method, using high molecular weight polyethylene glycol (PEG). Without PEG, only large flakes several micrometers in size containing nearly pure (Y,Gd)AlO3 were obtained. Adding PEG dramatically reduced the particle size. However, the (Y,Gd)AG phase was not obtained by merely adding PEG. Instead, mainly (Y,Gd)2O3 and small amount of Ce2O3 were obtained. Simultaneous use of PEG and a flux (simple salt) such as BF2 resulted in the formation of small YAG particles. The presence of the (Y,Gd)AG phase results in intense yellow-green luminescence. By selecting various heating routes, the fractions of cubic and hexagonal phases were controlled. It was found that the luminescence intensity is proportional to the fraction of cubic phase, and is probably independent of the hexagonal phase.