The quantum cutting of Tb~(3+) in Ca_6Ln _2Na_2(PO_4)_6F_2 (Ln = Gd, La) under VUV-UV excitation: With and without Gd~(3+)

摘要

The VUV-vis spectroscopic properties of Tb~(3+) activated fluoro-apatite phosphors Ca_6Ln_(2-x)Tb_xNa _2(PO_4)_6F_2 (Ln = Gd, La) were studied. The results show that phosphors Ca_6Gd_(2-x)Tb _xNa_2(PO_4)_6F_2 with Gd ~(3+) ions as sensitizers have intense absorption in the VUV range. The emission color of both phosphors can be tuned from blue to green by changing the doping concentration of Tb~(3+) under 172 nm excitation. The visible quantum cutting (QC) via cross relaxation between Tb~(3+) ions was observed in cases with and without Gd~(3+). Though QC can be realized in phosphors Ca_6La_(2-x)Tb_xNa_2(PO _4)_6F_2, we found that Gd~(3+)-containg phosphors have a higher QC efficiency, confirming that the Gd~(3+) ion indeed plays an important role during the quantum cutting process. In addition, the energy transfer process from Gd~(3+) to Tb~(3+) as well as ~5D_3-~5D_4 cross relaxation was investigated and discussed in terms of luminescence spectra and decay curves.