Structure and scintillation properties of Ce3+-activated Cs2NaLaCl6, Cs3LaCl6, Cs2NaLaBr6, Cs3LaBr6, Cs2NaLaI6 and Cs3LaI6

A systematic study of the structure and scintillation properties of La elpasolites and related compositions with the formula Cs2ALa1−yCeyX6 (where A=Cs, Na; X=Cl, Br, I) is reported. The compounds were determined to crystallize in a variety of crystal structures. Two of the compounds studied are cubic and their structures match a prediction derived from a composition-related tolerance factor. The cubic structure was not obtained with the iodides. Upon optical and X-ray excitation, the samples show the characteristic Ce3+ emission. Depending on the host, the optimal Ce concentration varied between 0.1 and 15%. The luminosity and energy resolution were measured on 4 single crystals with the following results: Cs2NaLaCl6:4% Ce luminosity of 26,400 ph/MeV, energy resolution 4.4%; Cs3LaCl6:8% Ce luminosity of 16,000 ph/MeV, energy resolution 8.6%; Cs2NaLaBr6:4% Ce luminosity of 46,000 ph/MeV, energy resolution 3.9%; Cs3LaBr6:15% Ce luminosity of 32,500 ph/MeV, energy resolution 4.9%. Single crystals of the iodide analogs could not be obtained by the Bridgman technique due to phase separation. Polycrystalline forms of these compounds, obtained by quenching from the melt, are scintillators.