Energy Conversion in Gd₂O₃ Nanocrystals Doped with Er³⁺ Ions

The conversion of the energy absorbed by cubic Gd₂O₃ nanocrystals doped with Er³⁺ and codoped with Yb³⁺ and Zn²⁺ ions in a temperature range of 95–425 K is studied at various concentrations of dopants. The photoluminescence spectra confirm the ability of excitation energy transfer from the Gd³⁺ ions or the matrix towards the Er³⁺ ions. The population of upper excited states in the Er³⁺ ions depends on the way of excitation, which cause the alterations in the probability of multiphonon relaxation from the excited states to the radiative levels. The kinetics of photoluminescence decay exhibit the possible energy transfer from anionic defects created by extra doping with Zn²⁺ ions. The temperature dependences of the upconversion luminescence yield for emission lines of 560 and 660 nm are found to be different.