Upconversion and pump saturation mechanisms in Er3+/Yb3+ co-doped Y2Ti2O7 nanocrystals

The Er3+/Yb3+ co-doped Y2Ti2O7 nanocrystals were synthesized by the sol–gel method. X-ray diffraction, transmission electronic microscopy, and photoluminescence spectra were measured to verify the Y2Ti2O7 nanocrystalline produced in the sample annealed at 800 °C. The anomalous slopes of the fitted line in the log-log plots for upconversion emissions and the pump-saturation effect of near-infrared emission were observed in the nanocrystalline samples. A theoretical model of practical Er3+/Yb3+ co-doped system based on the rate equations were put forward and explained the experimental phenomena well.