Fabrication and Up-conversion Luminescence Properties of Gd₂O₂S:Yb³⁺, Er³⁺ Nanopowders by Hydrothermal Reduction Method

Gd₂O₂S:Yb³⁺, Er³⁺ nanopowders were fabricated by hydrothermal method assisting with reduction route utilizing commercially available reagents of Gd₂O₃, Yb₂O₃, Er₂O₃, HNO₃, CO(NH₂)₂ and C₁₂H₂₅SO₄Na. The structure, morphology and up-conversion luminescent properties were characterized by fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and up-conversion luminescence spectra (UPL). The results show that the molar ratio of Gd³⁺:CO(NH₂)₂:SO₄^2-=2:1:x have a significant influence on the structure of the as prepared products. The precursor synthesized with x=1.0 could be converted into pure Gd₂O₂S phase by calcining at 800℃ for 2 h in the hybrid atmosphere of flowing hydrogen and argon (90%Ar+10%H₂) resulting in quasi-spherical and agglomerated morphology with 30 nm in size. Under 980 nm infrared light excitation, UPL spectra of the Gd₂O₂S:Yb³⁺, Er³⁺ nanophosphors show a red emission at 671 nm as the most prominent peak and a green emission at 548 nm as the secondary emission peak, which attribute to the ⁴F_9/2→⁴I_15/2 and ⁴S_3/2→⁴I_15/2 transitions of Er³⁺ ions. The quenching concentration of Er³⁺ ions is 5%, and the emission mechanism is two photo model.