The long afterglow phosphor CaAl2O4:Eu2+,Nd3+ was prepared by the high temperature solid-state reaction method, and the influence of La3+ and Dy3+ on the properties of the long afterglow phosphor was studied by X-ray diffraction (XRD), photoluminescence (PL), and thermolu-minescence (TL). The XRD pattern shows the host phase of CaAl2O4 is produced and no impurity phase appears. The peak wavelength of the phosphor does not vary with La3+ and Dy3+ doping. It implies that the crystal field, which affects the 5d electron states of Eu2+, is not changed dramatically after doping of La3+ and Dy3+. The TL spectra indicate that the phosphor doped with La3+ or Dy3+ produces different depths of trap energy level. In the mechanism of long afterglow luminescence, it is considered that La3+ or Dy3+ 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.
