Influence of powders calcination temperatures under hydrogen on the microstructures and properties of Gd2O2S:Pr,Ce scintillation ceramics

The precursor of Gd₂O₂S:Pr,Ce powders with stacked layered structure was synthesized in hot water bath using oxide powders and concentrated sulfuric acid as raw materials. The powders were synthesized by calcining the precursor under flowing H₂ atmosphere at 500-900^oC for 3 h. The influence of calcination temperatures under hydrogen atmosphere, which was defined as reduction temperature, on the microstructures and properties of powders was investigated. Using the synthesized powders as initial material, Gd₂O₂S:Pr,Ce scintillation ceramics with high relative density (over 98% of the theoretical value) were fabricated through vacuum pre-sintering at 1350^oC for 3 h followed by HIP post-treatment in an argon atmosphere at 1450^oC for 3 h. Intense green emission line at 511 nm due to the ³P₀→³H₄ transition of Pr³⁺ was obtained in the X-ray excited luminescence (XEL) spectra of all Gd₂O₂S:Pr,Ce ceramics. The Gd₂O₂S:Pr,Ce ceramics fabricated from powders synthesized at 700^oC showed the highest optical transmittance, XEL intensity, and light yield (LY) value of 24,660 ph/MeV @ 662 keV γ rays. The photoluminescence decay time of Pr^{3+ 3}P₀ → ³H₄ transition and scintillation decay time were measured to be ∼3 μs for all Gd₂O₂S:Pr,Ce ceramics. The effect of reduction temperature on optical transmittance and LY of Gd₂O₂S:Pr,Ce ceramics was also discussed.