Energy Transfer Study on Tb(3+)/Eu(3+) Co-Activated Sol-Gel Glass-Ceramic Materials Containing MF(3) (M = Y, La) Nanocrystals for NUV Optoelectronic Devices

In the present work, the Tb(3+)/Eu(3+) co-activated sol-gel glass-ceramic materials (GCs) containing MF(3) (M = Y, La) nanocrystals were fabricated during controlled heat-treatment of silicate xerogels at 350 °C. The studies of Tb(3+) → Eu(3+) energy transfer process (ET) were performed by excitation and emission spectra along with luminescence decay analysis. The co-activated xerogels and GCs exhibit multicolor emission originated from 4f(n)–4f(n) optical transitions of Tb(3+) ((5)D(4) → (7)F(J), J = 6–3) as well as Eu(3+) ions ((5)D(0) → (7)F(J), J = 0–4). Based on recorded decay curves, it was found that there is a significant prolongation in luminescence lifetimes of the (5)D(4) (Tb(3+)) and the (5)D(0) (Eu(3+)) levels after the controlled heat-treatment of xerogels. Moreover, for both types of prepared GCs, an increase in ET efficiency was also observed (from η(ET) ≈ 16% for xerogels up to η(ET) = 37.3% for SiO(2)-YF(3) GCs and η(ET) = 60.8% for SiO(2)-LaF(3) GCs). The changes in photoluminescence behavior of rare-earth (RE(3+)) dopants clearly evidenced their partial segregation inside low-phonon energy fluoride environment. The obtained results suggest that prepared SiO(2)-MF(3):Tb(3+), Eu(3+) GC materials could be considered for use as optical elements in RGB-lighting optoelectronic devices operating under near-ultraviolet (NUV) excitation.