Quaternary Iodides A(BaSr)I5:Eu2+ (A = K, Cs) as Scintillators for Radiation Detection

Abstract

Ternary alkali alkaline-earth iodides of the type AB2I5:Eu2+ (A = K, Cs; B = Sr, Ba) have been found to exhibit desirable properties suitable for high-performance scintillators. In a recent report [Phys. Rev. Appl. 2015, 4, 014012] we discussed preferential site occupation of Eu dopants in the Ba-containing ternary crystals. We alluded to the possibility of (Ba, Sr)-mixed quaternary iodides of the type ABaVIIISrVIII5:Eu2+ as a means to counter Eu clustering due to preferential distribution. Drawing from the previous work, here we report on the four prototypical Ba- and Sr-containing ternary hosts and compare their properties with the predicted mixed compounds. Density functional calculations reveal narrow regions of thermodynamic stability of the parent compounds. However, large excursions in the available ranges of the atomic chemical potentials allow precipitation of stable hosts. Additionally, the ordered quaternary phase ABaVIIISrVIII5 is also energetically favored with respect to its ternary end memb...