Tb:Gd<sub>9.33</sub>(SiO<sub>4</sub>)<sub>6</sub>O<sub>2</sub> oxyapatite as an X-ray scintillator

Gd9.33−xTbx(SiO4)6O2 (x = 0, 0.093, 0.467, 0.933, 1.866, 2.799, 3.732) oxyapatite single crystals were grown by the floating zone method, and their photoluminescence (PL) and scintillation properties were systematically investigated. Under UV and X-ray excitation, the samples exhibited emission peaks due to the 4f–4f transitions of Gd3+ and Tb3+. The decay times were on the milliseconds scale, consistent with Tb3+ emission. The PL quantum yields of the 1–30 % Tb-doped samples were approximately 70 %, and the light yield of the 10 % Tb-doped sample was 15400 photons/MeV, as calculated from the pulse height spectra under 137Cs γ-ray irradiation.