Impact of Er 3+ Concentration on Luminescence in NaLaF 4

Abstract In this work, NaLaF 4 doped with Er 3+ of different concentrations was synthesized. The luminescence spectrum for NaLaF 4 :Er 3+ (0.2 mol%) at 489 nm excitation reveals characteristic Er 3+ luminescence bands in the green (540 nm), red (660 nm) and infrared (980 nm) spectral regions. The green luminescence band originated from the 4 S 3/2 → 4 I 15/2 transition is the most intensive one in the luminescence spectrum. As the concentration of the activator is increasing, the intensity of all luminescence bands changes significantly. The super-linear increase of the infrared luminescence intensity with increasing Er 3+ concentration as well as the quenching of green luminescence at the concentrations exceeding 2 mol% can be attributed to the cross-relaxation process between the activator ions.