Intrinsic and impurity luminescence and multiplication of excitations in complex oxides

The emission bands at 5.1 and 5.0 eV have been detected at 9 K in the cathodoluminescence spectra of pure and doped with Eu2+ ions BaMgAl10O17 and SrMgAl10O17 phosphors, respectively. A comparison of these emissions with the spectra of pure and doped MgO, alpha-Al2O3 and MgAl2O4 crystals allowed to interpret the VUV emissions of phosphors as the recombination of conduction electrons with the holes localized at oxygen ions near Mg2+ substituting Al3+ I in spinel blocks. The creation regions of two or three electron-hole pairs by one photon of 22-32 eV that causes the ionization of the 2p(6) or 2s(2) shells of oxygen in spinel blocks, has been separated in the excitation spectra of blue and UV emissions of BaMgAl10O17 at 9 K. Besides thoroughly investigated 4f(7) --> 4f(6)5d(1) electron transitions in Eu2+ centres (absorption at 3.5-6.2 eV), the creation region of the electronic excitations connected with the excitation and ionization of oxygen ions nearby Eu2+ or Mg2+ ions (6.6-7.8 eV) can be tentatively separated in the excitation spectra of steady luminescence and recombination phosphorescence of SrMgAl10O17:Eu. (C) 2002 Elsevier Science B.V. All rights reserved.