Efficient Ultrafast Scintillation of KLuS2:Pr3+Phosphor: A Candidate for Fast-Timing Applications

A set of Pr3+-doped KLuS2 samples with different Pr concentrations are synthesized in the form of transparent crystalline hexagonal platelets by chemical reaction under a flow of hydrogen sulfide. Their structural, optical, and scintillation properties are investigated thoroughly by means of x-ray powder diffraction, time-resolved luminescence spectroscopy, scintillation light yield, and decay measurements to assess the spectroscopic properties of Pr3+ ions in the KLuS2 host. Charge-trapping processes are further investigated by electron paramagnetic resonance. The fundamental absorption band edge of the KLuS2 host is located at 303 nm, the absorption due to the Pr3+ 4f -> 5d transition is found at 347 nm, the emission maximum is given by the 4f 15d1 -> 3H4 transition of the Pr3+ ion at 380 nm, and the leading photoluminescence and scintillation decay time is around 1 ns at room temperature. The moderate scintillation light yield reaches 7200 ph/MeV. A phenomenological model is fitted to the measured temperature dependences of the photoluminescence emission spectra and photoluminescence decay times to better understand the dynamics of the 5d excited state of the Pr3+ center in the KLuS2 host. The number of photons emitted in the first nanosecond of the scintillation response is evaluated and found to be considerably higher (1.6-2.5 times) than that in the commercial (Lu;Y)2(SiO4)O:Ce, Ca scintillator, which shows the potential of Pr-doped KLuS2 for fast-timing scintillator applications.