Up-conversion luminescence of Er3 +/Yb3 + co-doped LiYF4 nanocrystals in sol–gel derived oxyfluoride glass-ceramics

• Er/Yb doped LiYF4 nanocrystals in glass ceramic show up-conversion luminescence.
• Up-conversion luminescence is due to Er3 + ions through a two-photon process.
• Saturation is due to Yb–Er energy back transfer and Er–Er cross-relaxation processes.

Up-conversion properties of Yb3 +/Er3 + co-doped LiYF4 nanocrystals embedded in a sol–gel derived oxyfluoride glass-ceramic have been studied by comparison to the corresponding polycrystalline sample. Under 980 nm laser light pumping, both Yb3 +/Er3 + co-doped LiYF4 samples show green ((2H11/2, 4S3/2) → 4I15/2) and red (4F9/2 → 4I15/2) up-conversion luminescences explained by a two-photon processes. The tendency for the saturation of the red up-conversion luminescence band observed in the glass ceramic was ascribed to a back energy transfer process Er3 +–Yb3 + and cross-relaxation processes caused by the high Yb3 + and Er3 + ions concentrations in the nanocrystals.