Defect Luminescence of LiBaF_3 Perovskites

摘要

Blue and red luminescence of undoped LiBaF_3 crystals was studied. A broad, isotropic photoluminescence band centered at 410 nm can be excited by 210 nm - 275 nm light in as grown crystals. After X-irradiation at RT a new narrower, anisotropic luminescence band apears at 425 nm which has an additional excitation band at 290 nm. The X-irradiation also creates the F-type centres and anisotropic centres with an absorption band at 630 nm and a luminescence band at 700 nm. No F- centre luminescence is observed. All the other centres mentioned act as radiative recombination centers as well. It is speculated that the origin of the blue luminescence is due to oxygen defects and that hte red luminescence is due to defects of a complex structure involving Fe impurity.