Crystal Growth, Optical, and Scintillation Properties of Eu²+-Doped TlSr₂Br₅

Crystals of undoped and Eu2+-doped TlSr2Br5of up to 16 mm in diameter and 50 mm in length were grown by the Vertical Bridgman technique. TlSr2Br5has the monoclinic crystal structure with space group P21/c. Its density and Zeffare 5.03 g/cm3and 58.6, respectively. Radioluminescence spectra of undoped and Eu2+-doped TlSr2Br5feature a broad emission band peaking at about 440 nm for undoped and 520 nm for Eu2+-doped crystals. The light yield of undoped TlSr2Br5is 42,000 ph/MeV, which increases to 55,000 ph/MeV for Eu2+-doped crystals. The energy resolution at 662 keV (137Cs) is about 5 – 6% (FWHM). The scintillation decay of undoped and Eu2+-doped TlSr2Br5is of the order of 100s of nanoseconds.