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Keywords:

  • borate;
  • micro-pulling-down (µ-PD) method;
  • Pr3+ 5d–4f luminescence;
  • scintillator

Abstract

Optical and scintillation properties of Pr3+-activated Ca3(BO3)2 (CBO) single crystals for neutron scintillator applications were examined. The crystals were grown by the micro-pulling down (µ-PD) method. In transmittance spectra, two absorption lines at 210 and 245 nm were observed and they were identified as Pr3+ transition from the ground state 3H to 5d state. The both of photo- and radio-luminescence spectra of Pr3+-doped CBO crystals demonstrated intense peak at 260 and 310 nm which was ascribed to the transition from the lowest 5d excited state to the 4f ground state levels of 3H. The main decay component was about 16–17 ns under 245 nm excitation wavelength. The relative scintillation light yield of 1.0% Pr3+-doped CBO was about 90% when compared with that of reference Li-glass scintillator (GS20) under 241Am 5.5 MeV α-ray excitation, while that measured under 252Cf neutron irradiation was about 20%. It was concluded that this difference originated from the difference of energy released from the neutron reactions.