Structure and peculiar luminescence of Eu3+-doped sodium/alkaline earths phosphate glasses

Abstract

This study intends to use the luminescence of trivalent europium, as a probe, to extract additional data on structural features detected previously in mixed metaphosphate glasses. To this end, five key compositions were doped with a constant amount of Eu 2 O 3 and synthesized using the melt quenching technique. Raman spectroscopy shows that the structure of the doped samples is in the vicinity of the metaphosphate compositional range i.e., the glasses are mainly formed by middle chain units in addition to a small proportion of end chain units. The variation of the densities of the doped compositions, obtained by the Archimedes’ method, was compared with the undoped glasses. The differential scanning calorimetry shows the uptick of the glass transition and onset of crystallization temperatures upon the addition of Eu 2 O 3. Finally, the fluorescence analyses show the transitions of Eu 3+ starting from the 5 D 0 excited state towards the 7 F J ground state manifold and additional emission lines starting from the higher excited state 5 D 1 to the 7 F 0, 7 F 1, and 7 F 2 energy levels. The presence of the latter lines was investigated by phonon sidebands spectroscopy and correlated with the phonon energy and electron-phonon coupling strength of the doped compositions.