Cerium-Doped Mixed-Alkali Rare-Earth Double-Phosphate Scintillators for X- and Gamma-Ray Detection

Previous measurements of the scintillation properties of members of the single-alkali, rare-earth double-phosphate family have demonstrated high light output and fast decay times when exposed to ionizing radiation. Cerium-doped K3Lu(PO4)2 and Rb3Lu(PO4)2 scintillators have exhibited light outputs of 32,500 and 28,200 photons/MeV respectively and decay times of 37 and 34 nanoseconds respectively. Because of the ease with which the alkali constituents (Li, Na, K, Rb, Cs) of the crystal matrix may be interchanged (e.g. K2CsLu(PO4)2 and CsLi2Lu(PO4)2), the rare-earth double-phosphate family of scintillators provides an ideal system for the study of matrix effects on scintillation efficiency and kinetics. In order to better understand and to ultimately optimize the scintillation properties of these scintillators, new members of the rare-earth double-phosphate family have been synthesized by high temperature flux growth. These new samples, represented by the general formula (A,B)3Lu(PO4)2:Ce where A and B are alkali elements, incorporate mixed alkali rather than single alkali components and varying levels of Ce doping. Light output, scintillation decay times, and photoluminescence measurements for the most promising of the samples to date are reported. In this paper, we identify promising samples and results that clearly demonstrate outstanding light output, up to 270% of BGO, fast decay times, 29-39 nanoseconds, and peak emission wavelengths of ∼ 400 nm for many of the samples.