Influence of La^(3+) and Dy^(3+) on the properties of the long afterglow phosphor CaAl_2O_4: Eu^(2+), Nd^(3+)

The long afterglow phosphor CaAl2O4： 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 diffiaction （XRD）, photoluminescence （PL）, and thermoluminescence （TL）. The XRD pattem shows the host phase of CaAl2O4 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.