Energy Transfer in the  Anionic Complex to the Impurities

The creation of a combined radiative state at 2.95–3.1 eV in the phosphor CaSO4−Dy 3+ has been investigated using vacuum ultraviolet and thermoactivation spectroscopy methods. It is shown that the combined radiative electronic state is formed from the radiative electronic states of the impurity electronic trapping centers Dy 2+− SO4− and the intrinsic electronic radiative states SO43−−SO4− during the excitation of the anion complex SO42− , as a result of charge transfer from the excited anion complex O 2−−Dy 3+ to the impurities and the neighboring anion complex O2−− SO42− . In the CaSO4−Dy phosphor, the combined radiative electronic state and impurity emission of Dy 3+ , 2.16 eV and 2.56 eV are excited by photons with energies of 3.95–4.0 eV and 4.5–4.6 eV. Energy transfer from the matrix to the Dy 3+ impurities is revealed upon thermal exposure as a result of the ionization of the electronic capture centers of Dy2+ and SO43− .