Anomalous luminescence in Sr4Al14O25:Eu, Dy phosphors

Abstract

${\mathrm{Sr}}_4{\mathrm{Al}}_{14}{\mathrm{O}}_{25}:\mathrm{Eu},$ 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 ${\mathrm{Eu}}^{\text{2+}}$ concentration doped in the host is less than 1.2 mol %, the emission spectra of ${\mathrm{Sr}}_4{\mathrm{Al}}_{14}{\mathrm{O}}_{25}:\mathrm{Eu},$ Dy show two main peaks at 407 and 494 nm, ascribed to two types of ${\mathrm{Eu}}^{\text{2+}}$ centers existing in the ${\mathrm{Sr}}_4{\mathrm{Al}}_{14}{\mathrm{O}}_{25}$ host. The emission peak at 407 nm disappears slowly with increasing concentration of ${\mathrm{Eu}}^{\text{2+}}$ due to the energy exchange between two types of ${\mathrm{Eu}}^{\text{2+}}$ centers.