Ana Maria Pires, Stephan Heer, Hans Ulrich Güdel and Osvaldo Antonio Serra
Er, Yb Doped Yttrium Based Nanosized Phosphors: Particle Size, "Host Lattice" and Doping Ion Concentration Effects on Upconversion Efficiency
J. Fluoresc. 16, 461-468 (2006)                 

Abstract: The upconverter phosphors studied herein have different percentages of Er³⁺ and Yb³⁺ as doping ions in different Y³⁺ matrixes (Y₂O₃, Y₂O₂S), and were prepared from different precursors (polymeric resin, oxalate, basic carbonate) and method (combustion). Upconversion emission spectra were recorded at 298 K for all the doped samples in the visible region, for efficiency and Green/Red emission relative intensity comparisons. Therefore, an investigation of the influence of the doping ion concentration, particle size and host lattice on the upconversion process is provided in view of the UPT (Upconverting phosphor technology application). On the basis of the results, it was possible to evaluate the best combination for a specific assay, considering whether it is advantageous to have the greatest contribution from the green or red emissions, or from both in comparable intensities.