First Evidence of Electron Trapped Ln2+ Promoting Afterglow on Eu2+, Ln3+ Activated Persistent Phosphor‐Example of BaZrSi3O9:Eu2+, Sm3

BaZrSi3O9:Eu2+, Sm3+ (Em:525 nm) is prepared. The role played by the trivalent co‐doping ion Sm3+ in the afterglow and the type of trap are clarified. BaZrSi3O9:Eu2+, Sm3+ is found to produce Sm2+ during the excitation by X‐ray absorption near‐edge structure (XANES), etc., and it is thus proved that Sm3+ exists as an electron trap in the afterglow process. In the field of persistent phosphors activated by Eu2+ and Re3+ such as Sm3+ or Dy3+ having been widely utilized as emergency guide lights, clock faces, etc. for > 25 years, for the first time it is successfully observed that after excitation Re2+ is formed, transferring its electron to 5d band of Eu2+, returning to Re3+ by itself, where the decrease in Sm2+ coincides with the increase in Sm3+, and the two decay time τ1 and τ2 of PL (5D0→7F0) of Sm2+ coincides with the two evolution time of PL (5d→4f) of Eu2+. The behavior of electron transfer from Sm2+ to Eu2+ as a key of afterglow is detected. The detailed afterglow mechanism is proposed by analysis of thermoluminescence and defect reaction, which is very important for the in‐depth investigation of the long afterglow material and the further improvement of the mechanism. The co‐doped Sm3+ acts as electron trap in the afterglow process demonstrated by the characteristic emission and the X‐ray absorption near‐edge structure (XANES) spectra of Sm2+ before and after excitation in BaZrSi3O9:Eu2+, Sm3+, which is also present in samples co‐doped with other Ln3+. Thus, the type of carriers and traps in this afterglow mechanism is clarified.