Synthesis of Green-Emitting GdOS:Pr Phosphor Nanoparticles and Fabrication of Translucent GdOS:Pr Scintillation Ceramics.

A translucent GdOS: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 GdOS:Pr powder with an average particle size of ~95 nm. The GdOS:Pr phosphor particle exhibits the characteristic green emission from P→H transitions of Pr at 512 nm upon UV excitation into a broad excitation band at 285-335 nm arising from 4→45 transition of Pr. Increasing Pr concentrations induce two redshifts for the two band centers of 4→45 transition and lattice absorption on photoluminescence excitation spectra. The optimum concentration of Pr is 0.5 at.%, and the luminescence quenching type is dominated by exchange interaction. The X-ray excited luminescence spectrum of the GdOS: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%).