Emerging New Pseudobinary and Ternary Halides as Scintillators for Radiation Detection

Abstract

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 SrI2 and LaBr3, 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 AB2I5 or ABI3, where the A and B cations are alkali and alkaline-earth metals, respectively. These are usually activated by Eu2+. We will consider Eu-dopant behavior in these compounds before delving into a set of ns2 containing ternaries. They are analogous to the AB2I5 group of materials, except that the ns2 ion is part of the crystal framework, replacing the alkali “A” ion, e.g., InBa2I5 or TlBa2I5. Interestingly, we predict Eu2+ activation will be rendered ineffective in these ns2 compounds, caused by changes in the valence and conduction band edges. However, the possibility of fast electron capture at ns2 sites and the prospect of self-activated scintillation could be interesting for detector applications.