Synthesis and characterization of Gd2O2S:Pr3+, Ce3+(GOS) scintillation phosphors via a homogeneous precipitation followed by solid-state reaction method

Gd2O2S:Pr3+, Ce3+scintillation phosphors (GOS) were successfully synthesized via a homogeneous precipitation followed by solid-state reaction method with Gd2O3, Pr(NO3)3·6H2O, Ce(NO3)3·6H2O, HNO3, NH3·H2O, CO(NH2)2, Na2CO3, and sublimated sulfur (S) as the starting materials. Fourier transform infrared spectrometer (FT-IR), differential scanning calorimetry-thermogravimetry (DSC-TG), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and photoluminescence (PL) were used to characterize the obtained products. FT-IR and DSC-TG results reveal that the precursor is mostly composed of gadolinium and carbonate groups with some crystal water and can be transformed into Gd2O3phase at 1000 °C for 2 h in air. XRD analysis shows that pure Gd2O2S phase can be synthesized with the molar ratio of Gd2O3:Na2CO3:S=1:5:20 when the reaction temperature is 1000 °C and the reaction time is 2 h. FE-SEM analysis shows that the morphology of the obtained Gd2O2S product has a block and irregular polyhedron structure with a significant increase in size of about 4 μm. PL spectrum analysis shows that the strongest green emission of Gd2O2S:0.20% Pr3+, 0.0025% Ce3+scintillation phosphor is observed around 513 nm, which is attributed to the 3P0→3H4transition of Pr3+ions. The average lifetime τ is calculated to be 1.43 μs for Gd2O2S:0.20% Pr3+, 0.0025% Ce3+scintillation phosphor. The above results meet the wavelength and lifetime requirements of GOS fluorescent screen used in medical radiotherapy linear accelerator.