Probing the luminescent properties of (Ca1-xSrx)8Mg3Al2Si7O28:Ce3+/Eu2+: A combined experiment and calculation study

Investigating the relationships between luminescent properties and the energy positions of rare earth ions is helpful for the design of phosphors. Herein, (Ca1-xSrx)Mg3Al2Si7O28:Ce3+/Eu2+ were synthesized by solid state reaction. The variations of energy positions of lowest 5d levels of Ce3+ and Eu2+ with the changes of centroid shift, crystal field splitting and stokes shifts were qualitatively calculated based on the empirical formulas. Substitution of Ca2+ by Sr2+ ions made the emission peaks of Eu2+ in (Ca1-xSrx)Mg3Al2Si7O28 shift from 527 to 469 nm and the full width at half-maximum of Ce3+ in (Ca1-xSrx)Mg3Al2Si7O28 widen from 55 to 66 nm. On the basis of calculated results, the variations of emission peaks of Eu2+ were mainly ascribed to the elevating of lowest 5d levels caused by the weakened centroid shift and crystal field splitting, especially the declined energy of crystal field splitting (from 2.28 to 2.01 eV). The effects of decreased rigidity and increased disorder of lattice caused by Sr2+ substituting Ca2+ had a greater impact than that of the centroid shift and crystal field splitting on the luminescence properties of Ce3+ in (Ca1-xSrx)Mg3Al2Si7O28. Serious thermal quenching behaviors occurred in the series phosphors due to the thermal ionization processes, which were proofed by the constructed host referred binding energy and vacuum-referred binding energy diagrams according to the experimental and calculated results of (Ca1-xSrx)Mg3Al2Si7O28:Ce3+/Eu2+.