Investigations of optical and scintillation properties of Tm3+-doped YAlO3

Pure, 0.1, 0.5 and 1 mol% Tm-doped YAP single crystalline scintillators were grown by the μ-PD method. Lattice constants were gradually decreased with Tm concentration in XRD analysis. In transmittance measurement, absorption bands due to Tm³⁺ 4f-4f transitions were observed at 265, 360, 485, 690 and 800 nm and they were ascribed to the transition from the ³H₆ ground state to its excited states, ¹I₆, ¹D₂, ¹G₄, ³F₃ and ³H₄, respectively. Strong emission peak due to 1I6-3F4 transition of Tm³⁺ was shown at 350 nm under X-ray irradiation. Photoluminescence decay time constants caused by this transition were evaluated to be from 15.3 to 17.3 μs and the scintillation decay time constants under gamma-ray excitation were estimated to be from 17.5 to 18.8 μs. Tm 1% doped one exhibited the highest light yield of 15100 ± 1500 photons/MeV when excited by ¹³⁷Cs gamma-ray irradiation.