Microstructure and properties of Gd2O2S:Pr, Ce scintillation ceramics from powders synthesized at different precursor calcination temperatures

Abstract

The precursor with a stacked layered structure was synthesized in a hot water bath using oxide powders and concentrated sulfuric acid as raw materials. The precursor underwent air calcination at temperatures ranging from 400 to 700 °C for 3 h to yield the intermediate product. Gd₂O₂S:Pr,Ce powders were obtained by reduction at 700 °C for 3 h under a flowing hydrogen atmosphere. The effects of calcination temperature on the microstructure and phase transformation of powders were investigated. Using the synthesized powders as starting materials, Gd₂O₂S:Pr,Ce scintillation ceramics were successfully fabricated with high relative density (exceeding 98 % of the theoretical value). This process involved vacuum pre-sintering at 1350 °C for 3 h, followed by HIP post-treatment in an argon atmosphere at 1450 °C for 3 h. A strong green emission line at 511 nm, attributed to the ³P₀→³H₄ transition of Pr³⁺, was observed in the X-ray excited luminescence (XEL) spectra of all Gd₂O₂S:Pr,Ce ceramics. The Gd₂O₂S:Pr,Ce ceramics from powders synthesized at 500 °C showed the relatively higher optical transmittance and light yield (LY) value of 24,660 ph/MeV @ 662 keV γ rays. The photoluminescence (PL) decays of Pr^{3+ 3}P₀ → ³H₄ transition were measured to be ∼2.90 μs for all Gd₂O₂S:Pr,Ce ceramics.