Optical and scintillation properties of Ce-doped Sr2Gd8(SiO4)6O2 apatite single crystals

We synthesized Sr2Gd8(SiO4)(6)O-2 apatite single crystals with different Ce concentrations by the Floating Zone (FZ) method and evaluated the optical and scintillation properties. We confirmed photoluminescence (PL) and scintillation emissions appearing around 400 nm, which was attributed to the 5d-4f transitions of Ce3+. The PL decay curves were approximated by a sum of two exponential decay functions with the decay constants of 21-24 ns and 78-644 ns, which are due to the host emission and emission by the 5d-4f transition of Ce3+, respectively. The scintillation decays are notably longer than those of PL, and the decay constants decreased with increasing the concentration of Ce. The X-ray induced afterglow was the lowest in the 0.5% Ce-doped sample. The 0.5, 1.6 and 2.1% Ce-doped samples showed a full-energy peak in the pulse height spectrum under Am-241 5.5 MeV alpha-ray irradiation. Among those samples, 0.5% Ce-doped sample showed the highest scintillation light yield of 76 ph/5.5 MeV-alpha.