Ultrafine Gd 2 O 2 S:Pr powders prepared via urea precipitation method using SO 2 /SO 4 2− as sulfuration agent—A comparative study

Synthesis of Green-Emitting Gd2O2S:Pr3+ Phosphor Nanoparticles and Fabrication of Translucent Gd2O2S:Pr3+ Scintillation Ceramics

A translucent Gd₂O₂S:Pr ceramic scintillator with an in-line transmittance of ~31% at 512 nm was successfully fabricated by argon-controlled sintering. The starting precipitation precursor was obtained by a chemical precipitation route at 80 °C using ammonia solution as the precipitate, followed by reduction at 1000 °C under flowing hydrogen to produce a sphere-like Gd₂O₂S:Pr powder with an average particle size of ~95 nm. The Gd₂O₂S:Pr phosphor particle exhibits the characteristic green emission from ³P_0,1→³H₄ transitions of Pr³⁺ at 512 nm upon UV excitation into a broad excitation band at 285–335 nm arising from 4f²→4f5d transition of Pr³⁺. Increasing Pr³⁺ concentrations induce two redshifts for the two band centers of 4f²→4f5d transition and lattice absorption on photoluminescence excitation spectra. The optimum concentration of Pr³⁺ is 0.5 at.%, and the luminescence quenching type is dominated by exchange interaction. The X-ray excited luminescence spectrum of the Gd₂O₂S:Pr ceramic is similar to the photoluminescence behavior of its particle. The phosphor powder and the ceramic scintillator have similar lifetimes of 2.93–2.99 μs, while the bulk material has rather higher external quantum efficiency (~37.8%) than the powder form (~27.2%).