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, α-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+ 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 2p6 or 2s2 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 4f7→ 4f65d1 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.