The influence of Yb 3+ doping on the upconversion luminescence of Pr 3+ in aluminum oxide based powders prepared by combustion synthesis

Abstract

The effect of ytterbium (Yb 3+) doping on the upconversion (UC) emission of praseodymium (Pr 3+) doped in aluminum oxide based powders prepared by combustion synthesis is reported for near-infrared excitation ( λ = 980 nm). Our experimental results show that the crystalline structure and the UC emission changes with the Yb 3+ concentration. The sample containing only Pr 3+ (1.0 wt.%) did not show any UC signal and the UC emission profiles of the samples containing Pr 3+ (1.0 wt.%) and Yb 3+ (0.5, 2.0 wt.%) are quite different. The sample containing 0.5 wt.% of Yb 3+ has five emission lines in the visible range associated to Pr 3+ 4f–4f transitions, 3P 0 → 3H 4 (∼497 nm), 3P 0 → 3H 5 (∼525 and ∼550 nm), 3P 0 → 3H 6 (∼620 nm) and 3P 0 → 3F 2 (∼650 nm). We believe that the UC process has its origin in energy transfer from Yb 3+ ions to Pr 3+ ions in Pr 0.83Al 11.83O 19 phase. The sample containing 2.0 wt.% of Yb 3+ has only one emission line in the visible range peaked at ∼507 nm which we believe has its origin in cooperative UC emission due to excited Yb 3+ pairs in YbAlO 3 phase. The samples containing Yb 3+ also present UC emission lines in the near-infrared which are assigned to intrinsic lattice defects.