Green persistent luminescence excitable by multiple wavelengths in the CaSc2O4:Ce3+ phosphor co-doped with Mg2+

Journal article, 2018

Calcium scandate (CaSc 2 O 4 ), when substituted with a small amount of the activator ion Ce 3+ to replace Ca 2+ , is a recently discovered green-emitting phosphor promising for solid-state lighting applications. The co-doping with aliovalent ions to compensate for the net positive charge, as induced by the Ce 3+ dopants, is a common approach to change the defect structure and tune the performance of the phosphor, but the underlying mechanisms are unclear. Here we investigate the effect of co-doping with charge-compensating Mg 2+ to substitute for Sc 3+ , using photoluminescence and thermoluminescence techniques. In comparison to the defect structure in Ce 3+ doped CaSc 2 O 4 , the co-doping with charge-compensating Mg 2+ leads to the formation of new traps. These traps are featured by activation energies in the range 0.58–0.64 eV, can be emptied at room temperature and show green long-lasting phosphorescence after excitation at 454, 340, and 254 nm, respectively. Analysis of the spectroscopic results in terms of a vacuum referred binding energy diagram allows us to reach at a plausible luminescence mechanism in {Ce 3+ /Ce 3+ Mg 2+ }-doped CaSc 2 O 4 .