Red long lasting phosphorescence in Ca2Ge7O16:Sm3+ via persistent energy transfer from the host to Sm3+

A red long-lasting phosphorescence phosphor Ca2Ge7O16:Sm3+ was synthesized by a high temperature solid state reaction. The persistent energy transfer process from Ca2Ge7O16 host to Sm3+ was confirmed to be much more efficient than that in the photoluminescence process. The color of the persistent luminescence could be adjusted from blue to red with increasing concentration of Sm3+ accordingly. Based on the analysis of the thermoluminescence curves, it was found that Sm3+ doped Ca2Ge7O16 also provided a possibility to be a kind of photo-storage phosphor. Detailed mechanism were studied and illustrated.