The influence of phase evolution on optical properties in rare earth doped glass ceramics containing NaYF4 nanocrystals.

The crystal phase evolution from cubic α-NaYF 4 to hexagonal β-NaYF 4 was achieved in transparent oxyfluoride glass ceramics by modifying glass composition and rare earth doping. It was found that the development of compressive stress during the crystallization process may be responsible for the formation of β-NaYF 4 nanocrystals. The incorporation of Eu 3+ ions into the precipitated NaYF 4 nanocrystals was verified and the difference of the distribution of Eu 3+ ions in the glass ceramics resulted in remarkable changes in the emission spectra, such as the relative emission intensity, Stark splitting and fluorescence decay lifetimes. Bright and efficient upconversion luminescence was observed in the Er 3+ /Yb 3+ co-doped glass ceramics and the corresponding upconversion mechanisms were analyzed. [ABSTRACT FROM AUTHOR]