Luminescence Kinetic Model for Long-Afterglow Phosphor(Sr_0.5Ca_1.5)MgSi₂O₇:Eu²⁺,Dy³⁺

A luminescence kinetic model for the green-emission long-afterglow phosphor (Sr_0.5Ca_1.5)MgSi₂O₇:Eu²⁺,Dy³⁺ is proposed based on the studies of the thermoluminescence and isothermal decay curves at different temperatures. The isothermal decay curves at different temperatures meet the hyperbolic law and show to be dependent on temperature. Combined with the decay curves and the thermoluminescence curves, it can be concluded that the long afterglow of this material originates from the traps with energy distribution rather than a single level trap. Upon illumination with ultra-violet or visible light, the trap filling can proceed via excitation of 4f electrons to the 5d level of Eu²⁺ ions. After excitation, 5d electrons can be transferred to the trap related to Dy³⁺ ions, and Eu³⁺ is left behind. Upon subsequent heating, the electron is released from this trap and recombines with Eu³⁺ to produce Eu²⁺ emission.