Abstract: The ZrO₂∶Er³⁺, Yb³⁺ nanocrystals were prepared by low temperature crystallizing in 1,3-butadinol. Red upconversion emission at 660 nm was observed from ZrO₂∶Er³⁺, Yb³⁺ nanocrystals with 980 nm excitation. The X-ray diffraction patterns confirm that the nanocrystals are cubic. The mechanism of nanocrystals upconvertion was studied. The Stark splits of the two excited states of Er³⁺ were calculated based on the theory of crystallization. The results confirm that the upconverted mechanisms in the ZrO₂∶Er³⁺, Yb³⁺ nanocrystals are due to the two processes, one is a consecutive absorption of two 980 nm photons process, and the other process is that electrons transfer to substeady states after absorption of 980 nm photons, then absorb 980 nm photons.

Key words: ZrO₂, Doping, Split of energy level