Optical spectroscopy, thermal quenching and electron–vibrational interaction of the octahedrally coordinated Eu2+ ion in CaAl2B2O7 and BaAl2B2O7

Abstract The spectroscopic properties of the six-fold coordinated Eu 2+ in CaAl 2 B 2 O 7 and BaAl 2 B 2 O 7 are investigated and reported in this paper. Relevant optical parameters such as the Stokes shift, crystal-field splitting, the centroid shift and the red shift of the Eu 2+ 4f 6 5d 1 electronic configuration are calculated from the experimental data. Further, the Huang–Rhys factor and the effective phonon energy, which are responsible for the electron–vibrational interaction, are theoretically estimated for the Eu 2+ ion in CaAl 2 B 2 O 7 and BaAl 2 B 2 O 7 . The low quenching temperature of the luminescence in these materials is tentatively connected with the thermally induced promotion of the Eu 2+ 4f 6 5d 1 electron to the host lattice conduction band (photoionization). Evidence for the limited solubility of Eu 2+ in BaAl 2 B 2 O 7 is presented. A comparative study of the Eu 2+ luminescence in M 2+ Al 2 B 2 O 7 (M 2+ = Ca 2+ , Sr 2+ , Ba 2+ ) family of materials is also presented.