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.

Crystal growth and spectroscopic performance of large crystalline boules of CsCaI3:Eu scintillator

“…For example, grain boundaries in CCI which appear invisible to the unaided eye can be resolved by the contrast produced by changes in the polarization of the transmitted light. The apparent optical isotropy observed in CCI is in agreement with theoretical calculations predicting a negligible optical anisotropy despite the anisotropic structure [13].…”

Effects of increasing size and changing europium activator concentration in KCaI3 scintillator crystals

“…In this manner, scintillation photons escaping all crystal surfaces not directly coupled to the PMT facing window can be channeled through an alternative photon path and collected with reduced interactions in the bulk of the crystal. In our measurements using this approach the medium between the crystal and reflector was typically mineral oil which is suspected to have a different refraction index (n ≈ 1.5) than the KCaI 3 :Eu crystal (with n likely closer to 2.0 based upon the calculations by Tyagi et al on CsCaI 3 :Eu [15]). The refractive index mismatch created between the oil and crystal forms a critical angle of approximately 45° which suggests equal probability a photon incident on this interface will remain in the medium of origin and vice versa.…”

High energy resolution scintillators for nuclear nonproliferation applications

“…Scintillation properties of KCaI 3 :Eu and CsCaI 3 :Eu were reported in [10,11,33]. The highest absolute light output measured for KCaI 3 :Eu 3% and CsCaI 3 :Eu 5% was 70,000 ph/MeV and 39,000 ph/MeV, respectively.…”

“…Complex metal halides with divalent and trivalent substitutional sites in the crystal lattices for the Ce 3+ or Eu 2+ doping are of particular interest. Several promising scintillators in compositional families such as ARE 2 X 7 :Ce, A 3 REX 6 :Ce, AM 2 X 5 :Eu, AMX 3 , A 3 MX 5 :Eu (A = Cs, K, Na; M = Ca, Sr, Ba; RE = Ce, Gd, Y, La; X = Cl, Br, I) have been discovered by our group as well as by others [2][3][4][5][6][7][8][9][10][11][12].…”