How activator ion concentration affects spectroscopic properties on Ba4Y3F17: Er3+, Yb3+, a new perspective up-conversion material

Ba4Y3F17 with Er3+ and Yb3+, a promising material for up-conversion luminescence, was synthesized. Excellent isomorphic capacity was detected. Low-temperature measurements show that erbium ions are incorporated in multiple lattice positions, which is inconsistent with the current model of Ba4Y3F17 crystal lattice structure. Activator ion concentration has a different impact on 4S3/2 and 4F9/2, states (for the green and red luminescence, respectively) depopulation. Energy transfer from Er3+ 4S3/2 state to Yb3+ is observed even at low temperature (15 K) while Er-Er cross-relaxation is observed from 120 K and above. Yb3+ concentration has a great impact to red-to-green up-conversion luminescence intensity ratio. Spectroscopic measurements allow to conclude that red up-conversion luminescence origins from 2.6 energy transfer steps form Yb3+ to Er3+ and violet up-conversion -3.5. Calculation shows that for the green up-conversion luminescence band, the internal quantum yield is in range 1.6-2.8% and for the red up-conversion luminescence, in the range -2.2-3.9%.