Luminescence and stability of Tb doped CaF 2 nanoparticles

Luminescence properties of CaF :Tb nanoparticles were studied in order to investigate the effect of CaF native defects on the photoluminescence dynamics of Tb ions. Incorporation of Tb ions into the CaF 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 ion as well as the decreasing trend of emission lifetime of the D 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 native defects play in the photoluminescence dynamics of Tb ions incorporated in a CaF matrix. The sample doped with 10 mol% of Tb ions was found to be stable under prolonged 254 nm ultraviolet irradiation.