Investigation of Electronic Excitations of Pure and Ce Doped 12CaO•7Al2O3 Using Luminescence Spectroscopy

Abstract

Pure and Ce doped nanoporous 12CaO•7Al2O3 (C12A7) oxides were synthesized using self-propagating combustion method and solid state reaction. Time-resolved photoluminescence method at low temperatures was applied in studies of powder samples and ceramics, which were obtained in a melt-solidification process partly replacing encaged oxygen ions with electrons. In pure C12A7 with the encaged electrons broad luminescence bands peaked at 3.3 and 5.0 eV were revealed. The first one corresponds to the luminescence due to the encaged oxygen ions and latter one is assigned to the recombination of electrons and holes localized on the framework oxygen ions. Ce doping introduces emission band at 3.0 eV due to 5d-4f transitions with several decay components in nanosecond range. The Ce 5d-4f luminescence is efficiently excited through Ce intra-center absorption as well as through energy transfer processes in the intrinsic absorption region of C12A7 above energy gap at 7.0 eV.