The roles of Eu2+ and Dy3+ in the blue long-lasting phosphor Sr2MgSi2O7: Eu2+, Dy3+

The luminescent properties of the undoped, the Eu2+ or Dy3+ singly doped as well as Eu2+ and Dy3+ codoped Sr2MgSi2O7, were investigated using synchrotron radiation and xenon or mercury lamp as excitation source. Under 172 nm excitation, besides the emission band peaked at 465 nm from Eu2+ in Sr2MgSi2O7:Eu2+, Dy3+, there are evident emission lines at 487 and 575 nm from intraconfigurational 4f transitions of Dy3+. After the UV excitation, the peak temperatures of thermoluminescence curves were at ∼65 °C for Sr2MgSi2O7:Eu2+ and ∼120 °C for Sr2MgSi2O7: Dy3+. Afterglow emission spectra peaking at 465 nm were increased with rising temperature from 180 K to room temperature. The results show that the role of Eu2+ in Sr2MgSi2O7:Eu2+, Dy3+ is not only the luminescence center, but also a trap center. On the contrary, the role of Dy3+ ions can be not only as a trap center, but also as a luminescence center.