Emerging New Pseudobinary and Ternary Halides as Scintillators for Radiation Detection

Recently there has been a discernible shift from simple binary halide scintillators (e.g., NaI, CsI) toward host compounds that are structurally and electronically more complex. Besides SrI 2 and LaBr 3 , several pseudobinary, ternary and quaternary halides have emerged as promising scintillators for radiation detection. Here, we survey our recent first-principles based computational studies of different hosts belonging to a class of mixed halides or distinct stoichiometric compounds. The mixed halides are comprised of simple binary end members, NaI or CsI, that are known scintillators. The ternary compounds belong to a family of iodides of the type AB 2 I 5 or ABI 3 , where the A and B cations are alkali and alkaline-earth metals, respectively. These are usually activated by Eu 2+ . We will consider Eu-dopant behavior in these compounds before delving into a set of ns 2 containing ternaries. They are analogous to the AB 2 I 5 group of materials, except that the ns 2 ion is part of the crystal framework, replacing the alkali “A” ion, e.g., InBa 2 I 5 or TlBa 2 I 5 . Interestingly, we predict Eu 2+ activation will be rendered ineffective in these ns 2 compounds, caused by changes in the valence and conduction band edges. However, the possibility of fast electron capture at ns 2 sites and the prospect of self-activated scintillation could be interesting for detector applications.