Structural evolution and enhancement of luminescence in the Eu-doped oxyfluoride glass ceramics containing NaGdF<inf>4</inf> nanocrystals

Abstract

Cubic-to-hexagonal phase evolution, narrow crystalline size distribution and enhancement of luminescence are simultaneously achieved by modifying the ratio of SiO&lt;inf&gt;2&lt;/inf&gt;/B&lt;inf&gt;2&lt;/inf&gt;O&lt;inf&gt;3&lt;/inf&gt; content in the Eu &lt;sup&gt;3+&lt;/sup&gt;-doped oxyfluoride borosilicate glass ceramics containing NaGdF&lt;inf&gt;4&lt;/inf&gt; nanocrystals. The mechanisms of phase evolution of NaGdF &lt;inf&gt;4&lt;/inf&gt; nanocrystals are discussed on the basis of IR spectra, viscosity, XRD and TEM data. The results indicate that the stresses developed during the thermal treatment process play an important role in the phase evolution, which provides an experimental evidence of pressure-induced disorder-to-order phase evolution during the crystallization process for the first time. It is also found that the excitation and emission spectra as well as the luminescence lifetimes of the Eu&lt;sup&gt;3+&lt;/sup&gt; ions in the oxyfluoride glass ceramic are sensitive to the crystal lattice of NaGdF&lt;inf&gt;4&lt;/inf&gt;. © 2013 The Royal Society of Chemistry.