Understanding up and down-conversion luminescence for Er³⁺/Yb³⁺ co-doped SiO₂-SnO₂ glass-ceramics

Er3+/Yb3+ co-doped SiO2-SnO2 glass-ceramics bulks were synthesized using the sol-gel method. High-re-solution transmission electron microscopy images, x-ray diffraction, and energy-dispersive x-ray spectroscopy mapping confirm that 5 nm SnO2 crystals were homogeneously dispersed in the silica matrix. The incorporation of Er3+ and Yb3+ ions in SnO2 was also confirmed by X-ray photoelectron spectroscopy. This analysis shows Er3+ and Yb3+ ions locate in SnO2 nanocrystal and amorphous silica sites. Er3+/Yb3+ co-doped SiO2-SnO2 glass-ceramics behave as both down and up-conversion luminescent materials. Efficient energy transfers from Yb3+ ion sensitizers to Er3+ activators cause remarkable 5-fold Er3+ emission enhancement at 1.55 mu m. We also propose a mechanism for down and up-conversion processes. (c) 2021 Elsevier B.V. All rights reserved.