Structural and luminescence properties of silica powders and transparent glass-ceramics containing LaF3:Eu3+ nanocrystals

In this work, silica powders and transparent glass-ceramic materials containing LaF3:Eu3+ nanocrystals were synthesized using the low-temperature sol-gel technique. Prepared samples were characterized by TG/DSC analysis as well as X-ray diffraction and IR spectroscopy. The transformation from liquid sols toward bulk powders and xerogels was also examined and analyzed. The optical behavior of prepared Eu3+-doped sol-gel samples were evaluated based on photoluminescence excitation (PLE: (em)=611nm) and emission (PL: (exc)=393nm, (exc)= 397nm) spectra as well as luminescence decay analysis. The series of luminescence lines located within reddish-orange spectral scope were registered and identified as the intra-configurational 4f(6)-4f(6) transitions originated from Eu3+ optically active ions ((D0FJ)-D-5-F-7, J=0-4). Moreover, the R/O-ratio was also calculated to estimate the symmetry in local framework around Eu3+ ions. The luminescence spectra and double-exponential character of decay curves recorded for fabricated nanocrystalline sol-gel samples ((1)(D-5(0))=2.07ms, (2)(D-5(0))=8.07ms and (1)(D-5(0))= 0.79ms, (2)(D-5(0))=9.76ms for powders and glass-ceramics, respectively) indicated the successful migration of optically active Eu3+ ions from amorphous silica framework to low phonon energy LaF3 nanocrystal phase.