Synthesis, characterization and luminescence properties of ZrO2:Yb3+-Er3+ nanophosphor

The effects of the Yb3+ concentration on the structural and luminescence properties of ZrO2:Yb3+-Er3+ nanoparticles prepared by sol-gel process are reported. The evolution of the crystalline structure and crystallite size as a function of Yb3+ concentration were investigated by XRD and TEM. The experimental results show that it is possible to obtain tetragonal and cubic structures by codoping the system 1 mol % Er2O3-ZrO2 with 2 and 8 mol % of Yb2O3, respectively. Upconversion luminescence at 656 nm (red), 544 nm, 525 nm (green) and 410 nm (blue) all characteristic of Er3+ ion, was observed when the ZrO2:Yb3+-Er3+ nanophosphors were excited at 968 nm, as well as the cooperative emission of Yb3+ (525 nm). The red and blue upconversion emission is enhanced with the increment of Yb3+ ion concentration, while the cooperative emission disappears in the presence of Er3+. The nature of this behavior is discussed taking into account the nonradiative energy transfer of one cooperative photon and cross-relaxation process.