The effects of added foreign ions in Gd2O2S : Tb3+; crystal field calculations, lifetimes, photo-luminescence and absorption spectra

A spectroscopic study is carried out in which the effects of added Ca2+ and Ru4+ transition metal ions on some characteristics of the emission of Gd2O2S : Tb3+ phosphors (energy levels, intensities, lifetimes) are examined and compared. In order to distinguish the Tb3+ emissions from impurity ones, the electronic energy levels of trivalent terbium are determined and the energy level scheme is completed by a crystal field analysis. The optical spectra reveal no terbium doped impurity phase; however, other rare earth ions present as impurities in the starting materials are detected. They are identified, and the influence of the added Ca2+ and Ru4+ on their emission lines is also examined.