Luminescence and stability of Tb doped CaF 2 nanoparticles.

Luminescence properties of CaF 2 :Tb 3+ nanoparticles were studied in order to investigate the effect of CaF 2 native defects on the photoluminescence dynamics of Tb 3+ ions. Incorporation of Tb ions into the CaF 2 host was confirmed by X-ray diffraction and X-ray photoelectron spectroscopy. Cross-relaxation energy transfer was observed from the photoluminescence spectra and decay curves upon excitation at 257 nm. However, the unusual long lifetime of the Tb 3+ ion as well as the decreasing trend of emission lifetime of the 5 D 3 level suggested the involvement of traps, which were further investigated by using temperature-dependent photoluminescence measurements, thermoluminescence and lifetime measurements at different wavelengths. This work highlights the critical role that the CaF 2 native defects play in the photoluminescence dynamics of Tb 3+ ions incorporated in a CaF 2 matrix. The sample doped with 10 mol% of Tb 3+ ions was found to be stable under prolonged 254 nm ultraviolet irradiation.