Design of crystallization of oxyfluoride glasses based on the local structure of fluorine

Abstract

This article reviews the development of new of new oxyfluoride glass-ceramics designed from the viewpoint of the local fluorine structure and crystallization process. Oxyfluoride glasses often form fluoride crystals, but formation of oxyfluoride crystals with a large fraction of fluorine is rare. We successfully fabricated oxyfluoride crystals of BaAlBO3F2 in glass-ceramics through heat-treatment by controlling the local structure of fluorine. The glass showed highly efficient photoluminescence with Eu3+-doping up to 97%. A reason for this is the high fluorine content and structural similarity to the crystal. Laser-induced crystallization was performed on Ni2+doped glass as a heating source, and lines composed of a single crystal were fabricated. Birefringence images and transmission electron microscope observations indicate that the growth of highly c-axis oriented BaAlBO3F2 crystals follows the laser scanning direction even if it changes. Notably, the direction of the c-axis of BaAlBO3F2 crystals changes gradually at crossing and bending points. The model of ‘‘self-organized homo-epitaxial growth” is proposed for orientations of single crystal line with crossing and bending shapes.