Growth and scintillation properties of Ce³⁺-doped (Y_1-xGd_x)AlO₃ crystals

The optical and scintillation properties of 0.5% fixed Ce-doped (Y_1-xGd_x)AlO₃ single crystals have been investigated at three different levels of Gd doping: x = 0.2, 0.4 and 0.6. Single crystal of the Ce³⁺-doped (Y_0.8Gd_0.2)AlO₃, (Y_0.6Gd_0.4)AlO₃ and (Y_0.4Gd_0.6)AlO₃ were successfully grown by μ-PD technique in nitrogen atmosphere. From X-ray diffraction analysis, no impurity phase was detected for the grown Ce-doped crystals. Ce-doped (Y_0.6Gd_0.4)AlO₃ crystal demonstrated highest fluorescence quantum efficiency (∼ 25%) with improvement of excitation efficiency due to the Gd-doping. When irradiated by the alpha-rays from a ²⁴¹Am source, all the Ce-doped crystals showed luminescence band that corresponding to 5d (t_2g)-4f transition of Ce³⁺. The scintillation decay time was characterized by two components; the fast component (5-15 ns) is ascribed to 5d-4f transition of Ce³⁺, while the slow one (100-200 ns) may be related to energy transfer between Ce³⁺ and Gd³⁺ ion. According to the result of ¹³⁷Cs gamma-ray irradiated pulse height spectra compared with BGO scintillator, the relative scintillation light output was found to be about 12200 ± 1220 (Gd 20%) and 16000 ± 1600 (Gd 40%) ph/MeV.