Surface crystallisation of yttrium aluminum garnet from a silicate glass

Abstract

Glasses with the mol% composition 17Y₂O₃·33Al₂O₃·40SiO₂·2AlF₃·3Na₂O·2CeF₃·3B₂O₃ were thermally annealed at 1000 °C for different periods of time. This resulted in the surface nucleation and subsequent growth of Ce³⁺-doped yttrium aluminium garnet (YAG) which shows an intense broadband fluorescence. In the bulk, the nucleation and subsequent growth of an X-ray amorphous star-shaped and alumina enriched phase leads to a depletion of alumina from the glass. The nucleation of monoclinic and orthorhombic Y₂Si₂O₇ adjacent to the YAG layer is observed in addition to pore formation. These pores serve as centres for enhanced nucleation near the surface. The nucleation and growth of the orthorhombic phase and a different monoclinic Y₂Si₂O₇ are additionally observed in the bulk. The phase identification and localization was performed by X-ray diffraction and electron backscatter diffraction (EBSD).