Photoluminescence and scintillation properties of Yb²⁺-doped ACaCl₃ (A = Cs, Rb, K) crystals

Photoluminescence and scintillation properties are reported for ACaCl₃:Yb²⁺ (A = Cs, Rb, K) crystals that were grown by a self-seeding solidification method. Single emission bands centered at approximately 445 nm with two decay time constants of approximately 10 and 200 μs were observed for photoluminescence and scintillation and are attributed to fast and slow components of spin-forbidden Yb²⁺ 5d–4f transitions, respectively. Light yields of ACaCl₃:Yb²⁺ were estimated to be (3,600–5,200) photons/MeV on the basis of pulse height spectra. If the slow components are considered, they were estimated to be (59,000–75,000) photons/MeV, which are higher than previously reported Yb²⁺-doped scintillators and those used in X-ray CT scanners (CsI:Tl⁺, CWO, and GOS). The developed ACaCl₃:Yb²⁺ (A = Cs, Rb, K) scintillator materials have the potential to replace conventional scintillators in current-mode detectors due to their high light yields.