Photoluminescence and energy transfer in transparent glass-ceramics based on GdF3:RE3+ (RE = Tb, Eu) nanocrystals

Abstract

In the present work, the transparent oxyfluoride glass-ceramic samples containing GdF3:RE3+ (RE = Tb, Eu) nanocrystals (nGCs) were fabricated via controlled heat-treatment of precursor xerogels prepared using a sol-gel method. The formation of GdF3 nanocrystalline phase from gadolinium(III) trifluoroacetate was verified based on XRD measurements. The average crystal sizes calculated from Scherrer formula were estimated to ∼10 nm as well as ∼6 nm for Tb3+- and Eu3+-doped samples, respectively. The optical behavior of prepared sol-gel samples was evaluated based on photoluminescence excitation (PLE) and emission spectra (PL) as well as luminescence decay analysis. Obtained samples exhibit the 5D4 → 7FJ (J = 6–3, Tb3+) and the 5D0 → 7FJ (J = 0–4, Eu3+) emission bands recorded within the visible spectral area under excitation at near-UV (393 nm (Eu3+), 351, 369, 378 nm (Tb3+)) as well as middle-UV illumination (273 nm (Gd3+)). Additionally, based on recorded decay curves, the luminescence lifetimes (τm) for the 5D4 (Tb3+) and the 5D0 (Eu3+) excited states were also evaluated. In general, recorded luminescence spectra and double-exponential character of decay curves for nGCs indicate a successful migration of Tb3+ and Eu3+ dopant ions from amorphous silicate framework to low-phonon energy GdF3 nanocrystal phase.