Influence of La 3+ and Dy 3+ on the properties of the long afterglow phosphor CaAl 2O 4: Eu 2+, Nd 3+

Abstract

The long afterglow phosphor CaAl 2O 4:Eu 2+,Nd 3+ was prepared by the high temperature solid-state reaction method, and the influence of La 3+ and Dy 3+ on the properties of the long afterglow phosphor was studied by X-ray diffraction (XRD), photoluminescence (PL), and thermoluminescence (TL). The XRD pattern shows the host phase of CaAl 2O 4 is produced and no impurity phase appears. The peak wavelength of the phosphor does not vary with La 3+ and Dy 3+ doping. It implies that the crystal field, which affects the 5d electron states of Eu 2+, is not changed dramatically after doping of La 3+ and Dy 3+. The TL spectra indicate that the phosphor doped with La 3+ or Dy 3+ produces different depths of trap energy level. In the mechanism of long afterglow luminescence, it is considered that La 3+ or Dy 3+ works as trap energy level. The decay time lies on the number of electrons in the trap energy level and the rate of the electrons returning to the excitation level.