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.