Improved upconversion luminescence and temperature sensing performance of ZrO₂:Er³⁺/Yb³⁺/Li⁺ nanocrystals

ZrO₂:Er³⁺/Yb³⁺/Li⁺ nanocrystals are synthesized by sol- gel method. Li⁺ ions doped in ZrO₂:Er³⁺/Yb³⁺ nanocrystals can greatly enhance the upconversion luminescence intensity of Er³⁺ ions. And the effect of Li⁺ ions on enhancement of upconversion luminescenceis is discussed. The fluorescence intensity ratio of the green upconversion luminescence bands and that of the green upconversion luminescence peaks are studied as a function of temperature in a range of 303 K~753 K. The maximum sensitivity is approximately 0.0050 K^{- 1} at 440 K by adopting the fluorescence intensity ratio of green upconversion luminescence peaks at 525 and 562 nm. It suggests that ZrO₂:Er³⁺/Yb³⁺/Li⁺ nanocrystals is a suitable probe for optical temperature sensing by the fluorescence intensity ratio technique.