Downshifting by energy transfer in Eu3+/Yb3+ codoped Ba4La6(SiO4)6O glass ceramics

We report on an efficient near-infrared downshifting in Eu3+/Yb3+ codoped glass ceramics containing Ba4La6(SiO4)6O crystals. The structural and luminescence properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), static and dynamic photoemission and excitation spectroscopy. After crystallization, the doping ions are found to be selectively incorporated into the precipitated oxyapatite crystals on La3+ sites, contributing to the remarkably enhanced visible emission of Eu3+ under 394 nm excitation. The Eu3+/Yb3+ codoped glass ceramics additionally exhibits efficient near-infrared luminescence of Yb3+ around 1000 nm upon photon excitation of Eu3+ within the 300-550 nm range. The reduced visible emission and decay time of 5D0 state with Yb3+ codoping further confirm the energy transfer from Eu3+ to Yb3+, which is promoted due to the shortened distance between Eu3+ and Yb3+ within crystals. The maximum energy transfer efficiency is evaluated to be 61%. It is revealed that energy transfer process occurs predominantly through the cross relaxation of Eu3+(5D0) + Yb3+(2F7/2) → Eu3+(7F6) + Yb3+(7F5/2).