Upconversion luminescent properties and mechanisms of bulk La2O2CN2: Er3+/Yb3+ phosphors

Er 3+ singly doped and Er 3+ /Yb 3+ co-doped bulk La 2 O 2 CN 2 phosphors were prepared by a classical solid-state reaction of Li 2 CO 3 , Er 2 O 3 , Yb 2 O 3 and LaF 3 under NH 3 gas flow in the presence of graphite at low firing temperature. The crystal structures of La 2 O 2 CN 2 : Er 3+ and La 2 O 2 CN 2 : Er 3+ /Yb 3+ were confirmed by X-ray diffraction (XRD), and all the samples crystallize in a tetragonal structure with space group I4/mmm. FE-SEM was applied to investigate the particle sizes and morphologies. Upconversion luminescence characteristics have been studied in detail by varying Er 3+ and Yb 3+ contents. Under 980 nm light excitation, Er 3+ doped La 2 O 2 CN 2 samples exhibited weak blue and strong green emission peaks which are corresponding to the 4 F 7/2→ 4 I 15/2 and 2 H 11/2 → 4 I 15/2 transitions of Er 3+ . While, Er 3+ /Yb 3+ doped La 2 O 2 CN 2 samples exhibited blue, green and red emission peaks which are respectively corresponding to the 4 F 7/2→ 4 I 15/2 , 2 H 11/2 → 4 I 15/2 , 4 S 3/2 → 4 I 15/2 and 4 F 9/2 → 4 I 15/2 transitions of Er 3+ and also the emission intensity are enhanced due to the energy transfer from Yb 3+ to Er 3+ .