Investigation of Er:Bi4Ge3O12 single crystals emitting near-infrared luminescence for scintillation detectors

0.1%, 0.5%, and 1% Er:Bi4Ge3O12 (BGO) single crystals were grown by the floating zone method, and the structural, optical, and scintillation properties were investigated. From the X-ray diffraction analyses, all the obtained crystals were confirmed to be in the single phase of BGO. The crystals exhibited photoluminescence and scintillation due to the 4f–4f transitions of Er3+ peaking at ~550 and 1540 nm as well as an emission band due to the 3P1–1S0 transitions of Bi3+ across 400–600 nm. The photoluminescence quantum yields of the NIR emission (1429–1677 nm) were 50.6%, 85.8%, and 69.0% for the 0.1%, 0.5%, and 1% Er-doped crystals, respectively. The scintillation decay curves were measured in the spectral range from UV to NIR, and the decay time constants of the visible–NIR luminescence were confirmed to be consistent with the known values of Er3+. The afterglow level at 20 ms after X-ray irradiation was 12.0–25.4 ppm, which is similar to the value of Nd:BGO. All the crystals showed a good linearity between the near-infrared luminescence intensity and X-ray exposure dose rate, and the lowest detectable dose rate was 0.006 Gy/h in all the crystals.