Low-frequency band at 50 cm~(-1) in the Raman spectrum of cristobalite: identification of similar structural motifs in glasses and crystals of similar composition

摘要

Raman spectra of high-temperature #alpha#-cristobalite ceramics and silica glass have been obtained in a wide frequency range from 10 to 1500 cm~(-1). A low-frequency maximum at 50 cm~(-1) in the spectrum of cristobalite has been observed to be similar to the well-known band at 52 cm~(-1) in the Raman spectra of silica glasses. The combination of literature reports on inelastic neutron scattering, low-temperature heat capacity, X-ray and neutron scattering in the region of the first sharp diffraction peak (FSDP) and our data on Raman and far IR spectroscopies indicate a cristobalite-like medium-range order in silica glasses. The comparison of the obtained spectra with the Raman spectrum of #alpha#-quartz, as well as the comparison of far IR spectra of some muticomponent glasses with the ones of corresponding crystals, deomonstrates that by means of low-frequency spectroscopic data it is possible to identify the crystalline polymorphs reflected by the glass.