Anomalous luminescence in Sr4Al14O25:Eu, Dy phosphors

Sr 4 Al 14 O 25 : Eu , Dy material with an extraordinarily long afterglow was synthesized via a traditional ceramic processing. Such a long afterglow observed can last over 20 h at recognizable intensity level (0.32 mcd/m2), which is attributed to energy exchange between the traps and emission states resulting from Dy and Eu doping. When the Eu2+ concentration doped in the host is less than 1.2 mol %, the emission spectra of Sr4Al14O25:Eu, Dy show two main peaks at 407 and 494 nm, ascribed to two types of Eu2+ centers existing in the Sr4Al14O25 host. The emission peak at 407 nm disappears slowly with increasing concentration of Eu2+ due to the energy exchange between two types of Eu2+ centers.