Raman spectroscopy study of BaI2 :Eu and SrI2 :Eu scintillator crystals

Europium-doped barium and strontium iodide crystals are high light yield scintillator materials with excellent energy resolution. In this communication, BaI2:Eu and SrI2:Eu single crystals with space groups of Pnma (D2h16) and Pbca (D2h15) respectively were grown from the vertical Bridgman method. The crystals were investigated with polarized Raman spectroscopy at temperatures varied from 77 to 300 K. The observed Raman-active modes for each crystal were assigned with the help of group theory analysis. It is found that the absence of the site symmetry leads to splitting of a spectral line in Pnma structure into two lines in the Pbca structure. Structural defects including dark spots formed during crystal growth and new species produced from hydration were characterized.

Research highlights
► BaI2:Eu and SrI2:Eu crystals were grown from the Bridgman method.
► The crystals were studied with polarized Raman spectroscopy.
► The absence of the site symmetry leads to splitting of spectral lines of SrI2.
► The hydration species were identified as confined I3− anions.