Photoluminescence properties and pump-saturation effect of Er3+/Yb3+ co-doped Y2Ti2O7 nanocrystals

► Pump-saturation of NIR photoluminescence. ► Anomalous slope (less than 1) of the fitted straight line in the double-logarithmic plots for up-conversion emissions. ► We proved the energy back transition(EBT) process and the non-radiative multiphonon relaxation from 2H11/2 and 4S3/2 levels. ► We analyzed the change of PL intensity with annealing temperature. ► The transition from the amorphous to the nanocrystallines.