Structural and Scintillation Properties of Cerium-Doped ${\rm Ba}_{{}_{1- \rm x}}{\rm La}_{{}_{\rm x}}{\rm Cl}_{{}_{2+ \rm x }}$ Ceramics

A series of cerium-doped compounds with the composition Ba_1-xLa_xCl_2+x and 0 < x < 0.5 have been prepared in ceramic form. We find from the powder X-ray diffraction patterns that the compounds adopt the cubic fluorite structure for 0.05 < x 0.34. Samples with x~ 0.2 are translucent. When doped with trivalent cerium, the materials show photoluminescence emission peaks at 350, 372 nm (for the Ba_0.66La_0.34Cl_2.34 composition); the photoluminescence decay can be fitted with a single exponential with decay time 25 ns. The scintillation pulse height analysis shows a photopeak ¹³⁷Cs for which can be used to compute a light yield of 4000 photons/MeV. The scintillation decay is non-exponential, with a rapid initial decay which can be represented approximately by a decay constant of ~100 ns, but there is a substantial delayed scintillation which extends over several microseconds.