Inductive effect of crystalline nucleus on the structure of its local environment in the process of quartz glass crystallization

摘要

The morphology and the structural and chemical properties of crystalline formations appearing on the surface of commercial quartz glasses at the beginning of the induction stage upon heating at temperatures of 1000-1300A degrees C are studied by optical polarization microscopy, mu-Fourier transform infrared spectroscopy, and X-ray diffraction. It is shown that crystalline island nuclei induce crystallization not only in the local environment of the surface layer, but also in the glass bulk at a depth of up to a parts per thousand 200 mu m. Crystalline nuclei in the center of islands often have an imperfect crystal structure formed by intermediate mesophases based on individual low-symmetry SiO4 tetrahedra. However, the induced phase at the periphery of these nuclei has a well-ordered crystal structure consisting mainly of alpha-SiO2 (quartz) and/or alpha-cristobalite. The proportion of these two phases depends on the glass heating temperature, namely, at 1000A degrees C, the induced structure for the most part contains alpha-SiO2, while alpha-cristobalite dominates at 1300A degrees C.