Enhancement of Visible Upconversion Emission in Y₂O₃:Er³⁺‐Yb³⁺ by Addition of Thiourea and LiOH in the Phosphor Synthesis

Spherical like Y 2 O 3 nanostructures doped with Er 3+ and Yb 3+ ions have been synthesized by a facile hydrothermal method. The samples were prepared by using different precipitant agents in the synthesis process. The phosphors were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence spectroscopy. Effects of the precipitant agents on structural, morphological, and photoluminescence properties of Y 2 O 3 :Er 3+ ‐Yb 3+ are studied and discussed. XRD analysis indicates that all samples, prepared with different precipitant agents, present the same cubic phase. Electron microscopy measurements show regular spherical shapes with size diameter depending on precipitant agent. Photoluminescence reveals that the samples have strong green (563 nm) and red (660 nm) emissions corresponding to 4 S 3/2 → 4 I 15/2 and 4 F 9/2 → 4 I 15/2 transitions of Er 3+ ions, respectively. The nanophosphors prepared with both Thiourea and Lithium Hydroxide exhibit the stronger visible upconversion luminescence under 980 nm diode laser excitation.