Scintillation properties of In-doped NaI transparent ceramics

In-doped NaI transparent ceramic scintillators were synthesized by the spark plasma sintering method, and In-doped NaI single crystal was grown by the Bridgman–Stockbarger method. The diffuse transmittance at the emission wavelength was ∼70% for the transparent ceramics and ∼90% for the single crystal. In the scintillation spectra under X-ray irradiation, emission peaks were observed at around 320, 460, and 510 nm in both of the transparent ceramic and single crystal samples. The peaks at 460 and 510 nm are due to 3P1 →1S0 transitions of In+. The decay time constants of the transparent ceramics and the single crystal were 1.8 μs. The X-ray induced afterglow level of the 0.1% In-doped NaI transparent ceramic and the single crystal was 170 and 777 ppm, respectively. In pulse height analysis, 662 keV photoabsorption peaks were clearly observed in all the samples when irradiated with 137Cs γ-rays. The light yield of the 0.1% In-doped NaI transparent ceramic was 19,000 ph/MeV, and that of the 0.1% In-doped NaI single crystal was 12,000 ph/MeV. The transparent ceramics showed better scintillation properties than the single crystal.