The characterization of Eu2+-doped mixed alkaline-earth iodide scintillator crystals

The high-performance inorganic scintillator, SrI2:Eu2+, when activated with divalent europium in the concentration range of 3–6%, has shown great promise for use in applications that require high-energy-resolution gamma-ray detection. We have recently grown and tested crystals in which other alkaline-earth ions have been partially substituted for strontium ions. Specifically, europium-doped single crystals have been grown in which up to 30 at% of the strontium ions have been substituted for by barium, magnesium, or calcium ions. In the case of the strontium iodide scintillator host, a material that is characterized by an orthorhombic crystal structure, three other column IIA elements are obvious choices for investigations intended to realize potential improvements in the performance of SrI2:Eu2+-based scintillators via the replacement of strontium ions with Mg2+, Ca2+, or Ba2+. Light yields up to 81,400 photons/MeV with an associated energy resolution of 3.7% (fwhm for 662 keV gamma rays) have been observed in the case of partial substitution of Ba2+ for Sr2+. The measured decay times ranged from 1.1 to 2.0 μs, while the peak emission wavelengths ranged from 432 to 438 nm.