Small-Angle X-Ray Scattering Study of Phase Separation in Glasses

Abstract

Two heat-treated glasses, a calcium glass (76.1% SiO2, 11.0% CaO, and 12.9% Na2O by weight) and a strontium glass (69.8% SiO2, 18.4% SrO, and 11.8% Na2O by weight), have been investigated by small-angle x-ray scattering. The samples were studied with a Kratky camera and also with a four-slit collimation system of the type developed by Beeman et al. The use of two independent collimation systems provided a check for systematic errors. In addition, the results verify the reliability of the collimation correction methods routinely employed in correction of collimation effects in small-angle x-ray scattering data. The measured radii of gyration correspond to spherical droplets with diameters of about 500 Å in good agreement with the diameters obtained from electron micrographs. By comparison of the scattering from the glass samples with the scattering from calibrated silica suspensions, the difference in the electron densities of the droplet phase and the matrix was computed for each glass. The results indicate that the droplet phase is a high-density form of silica with density 2.32 g/cm3, as compared with the normal value of 2.20 g/cm3 for vitreous silica. A defective cristobalite structure with density 2.32 g/cm3 is proposed for the droplet phase.

Untersuchung glasig‐amorpher Strukturen (I)

“…Sowohl im aniorphen Einkomponenten-als auch in amorphen Mehrkomponenten-Systenien ( VOGEL ; HAMMEL ; CHARLES 1966 ; STROM, TAYLOR) wurden strukturelle Inhoniogenitaten in iiberinolekularen Bereichen gefunden. Wahrend uber die Entstehungsbedingungen heterogener Submikrostrukturen in aniorphen Mehrkoniponenten-Systemen weitgehende Ubereinstimniung besteht (CAHN, CHARLES ; CAHN; HALLER;PATEL et al ;CHARLES 1974;SRINIVASAN et al), gehen die Ansichten uber die Existenz, die Ursachen und die Interpretation struktureller Inhomogenitaten in submikroskopischen Bereichen in amorphen Einkoniponenten-Systenien, wie z. B. glasigeni SiO,, GeO,, BeF, etc.…”