Crystallization and upconversion luminescence of distorted fluorite nanocrystals in Ba2+ containing oxyfluoride glass ceramics

摘要

In this study novel Er3+-doped transparent glass ceramics were prepared from melt-quenched glasses with general composition of Na2O-NaF-BaF2-YF3-Al2O3-SiO2. The phase composition of the annealed glass ceramics strongly depends on the BaF2 content in glass matrix. Crystallization of beta-NaYF4, cubic fluorite type, tetragonal nanocrystals and rhombohedral Ba4Y3F17 was observed. An introduction of BaF2 in the glass matrix suppresses the crystallization of beta-NaYF4, promotes the formation of Ba2+ containing fluoride phases and reduces the cross-relaxation between Er3+ ions in fluoride crystals. Small rate of the nonradiative processes and low local symmetry of rhombohedrally disordered Ba4Y3F17 enables an efficient upconversion luminescence surpassing that of the glass ceramics containing beta-NaYF4 nanocrystals. (C) 2016 Elsevier Ltd. All rights reserved.