Deviation from the vavilov law in the short-wavelength band of an f-d transition upon excitation of the luminescence of Tb3+ ions in CaF2 and Tb2(SO4)3 · 8H2O crystals and boron glasses

Luminescence and stability of Tb doped CaF2 nanoparticles

“…37 In 2011 Mamykin et al reported the degradation of UV irradiated CaF 2 :Tb together with the appearance of a brown colour which was associated with the conversion of Tb( iii ) to Tb( iv ) ions. 38 However, our XPS results (Table 2) comparing the irradiated and unirradiated samples indicated no change in the ratio of Tb ions in the two valence states. The shorter wavelength of 215 nm used during this previous study may have contributed to these different findings.…”