Analysis of Mullite Formation in the Core Glass of a Chromium-Doped Aluminosilicate Fiber

Abstract

Using MCVD, we have produced optically active fibers with a glass-ceramic core containing mullite, 3Al₂O₃ · 2SiO₂, as a major crystalline phase. Thermodynamic prediction of mullite formation conditions has been supplemented by thermal analysis and X-ray diffraction characterization of preform core samples, and fiber heat treatment (annealing) conditions have been established. Luminescence measurements for the fibers annealed under optimal conditions demonstrate that optically active chromium has a crystalline local environment.