A New Long Phosphorescent Phosphor with High Brightness, SrAl2 O 4 : Eu2 +  , Dy3 +

A green emitting phosphor with very bright and long lasting phosphorescence has been newly developed. The incorporation of ion into the system as an auxiliary activator dominates the phosphorescence, thermoluminescence, and photoconductivity characteristics of the phosphor to a large extent. Evidence is presented for the mechanism that the phosphorescence is ascribed to the photoconductivity due to holes, and to the trapping and thermal release of the holes by ions in the system. The incorporation of the ion forms a highly dense trapping level located at a suitable depth in relation to the thermal release rate at room temperature, thus producing the very bright and long phosphorescence.