Photoluminescence processes in LaOCl:Bi and YOCl:Bi

The luminescence of rare earth oxychlorides LnOCL:Bi (with Ln = La and Y) is studied in detail. The main excitation bands, responsible for the blue and UV fluorescences, are attributed to the bismuth activator substituting for Ln³⁺ in the rare earth tetragonal site. The weak shoulder of these bands and the complex decay times are assumed due to a parasitical phase, La₂O₃ or Y₂O₃ doped by bismuth, an X-ray analysis confirming their presence in the samples. Finally, the existence of these phases does not seem to have an important effect upon the interpretation of the luminescence processes of the main center, as shown by the configuration curve model.