Sol-gel synthesis, characterization, and photoluminescence properties of sub-micron Gd₂O₂SO₄ powders

The advanced phosphorescent Gd₂O₂SO₄ (GOS) sub-micron powders were successfully synthesized through a sol-gel method utilizing commercially available Gd(CH₃CO₂)₃.xH₂O, (NH₄)₂SO₄, and CO(NH₂)₂ as precursors. GOS phosphors were characterized by differential thermal analysis-thermogravimetry (DTA-TG), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), particle size analyzer (PSA), and time-resolved spectrometer (TRS). The results showed that the samples calcinated at different temperatures from 950 to 1200 °C were composed of the different Gd-based phases. All analyzes confirmed that pure Gd₂O₂SO₄ crystalline structure was produced at 950 and 1000 °C. However, this structure deteriorated over 1000 °C. At temperature range of 1100 and 1200 °C, Gd₂O₃ and Gd₂S₃ structures were observed in the powder. The powders at 950 °C exhibit a surface morphology smaller than 1 μm. In a fully deoxygenated moiety, when excited at 356 nm, the phosphors exhibited well-shaped narrow emission bands centered at 542 nm and biexponential decay times. The phosphorescence of the material was oxygen resistive and wavelength dependent.