Theoretical and experimental characterization of promising new scintillators: Eu2+ doped CsCaCl3 and CsCaI3

Abstract

An integrated approach was used to characterize Eu2+ doped CsCaCl3 and CsCaI3 crystals theoretically and experimentally. The temperature dependence of photoluminescence excitation, emission, and decay time was studied to better understand the energy transport and migration mechanism in these materials. The broadening and redshift of emission with increasing temperature was explained for both crystals by simultaneous quenching of emission and interaction of emission states with lattice vibration. The unusual increase of photoluminescence decay time with increasing temperature was ascribed to the presence of states with a lowered radiative rate slightly above the emitting states. The electronic and optical properties were also calculated theoretically with the help of Density functional theory in order to explain the Eu2+ emission properties in these crystals. The calculation explains the better scintillation light output and proportionality in CsCaI3. The promising cross-luminescent efficiency of these materials is also explained with the help of electronic band structure and dispersion of the partial density of the states of constituent atoms. Despite structural anisotropy, the calculated optical properties of CsCaI3 are nearly isotropic, and therefore the synthesis of optically transparent polycrystalline ceramics may be possible.