Characterizations of Pr:Ca₂Al₂SiO₇ single crystal scintillator for α-ray detection

Undoped and Pr-doped Ca₂Al₂SiO₇ single crystals were synthesized by the floating zone method. The X-ray diffraction patterns confirmed that all the crystals have no impurity phases. Pr-doped crystals show photoluminescence with broad emission bands from 250 to 400 nm and sharp emission lines from 500 to 800 nm due to the 5d-4f and 4f-4f transitions of Pr³⁺, respectively. Under VUV photon excitation using a synchrotron source, the undoped crystal shows broad emission bands around 380 and 600 nm considered to be due to self-trapped excitons (STEs). The PL decay time constants of the Pr-doped crystals are 15–19 ns and 23–56 μs. The scintillation spectra of Pr-doped crystals are different compared with PL spectra, and the emissions consist of emission peaks due to Pr³⁺ as well as the STEs. From the pulse height spectra measured using the Pr-doped crystals under ²⁴¹Am 5.5 MeV α-rays, all the crystals exhibit a clear peak of full-energy absorption, and the 3.0% Pr-doped crystal shows the highest scintillation light yield of 2,600 ph/5.5 MeV-α.