Crystal growth and characterization of high performance KSr2BrxI5−x:Eu scintillators

Abstract

In this work we investigated the effects of replacing some of the matrix iodine atoms in KSr2I5:Eu with bromine, forming new solid solutions of KSr2BrxI(5−x):Eu (where 0.05 ≤ x ≤ 1). Transparent 15 and 22 mm diameter single crystals of KSr2BrxI(5−x):Eu were grown via the vertical Bridgman technique using a two-zone transparent furnace. The scintillation properties of the mixed compounds were investigated and compared to the non-mixed parent compound, KSr2I5:Eu. The addition of bromine blue-shifted the x-ray excited emission from 450 to 446 nm, increased the light yield by ~11% and decreased the scintillation decay time by suppressing its secondary component (≥3 µs), while maintaining energy resolutions comparable to the reference crystal. Thermoluminescence glow curves showed that the addition of bromine modified the shallow traps located between 25 and 55 K, suggesting that these traps are responsible for lengthening KSI’s decay time. In large sizes (10.3 cm3), KSr2Br0.10I4.90:Eu 2% had light yields up to 79,000 ph/MeV and energy resolutions as low as 3.2% at 662 keV.