Memory effects of raw materials in glass melts Raman spectroscopy investigations of glass defects

Abstract

The present work is based on investigations of aluminum oxide containing lead glasses. The aim was to decrease the costs in the production of lead glass by addition of alkalis other than potassium and soda. Feldspar and nepheline from different sources were employed. During the melting process inhomogeneities, cords, knots and blisters arise the origin of which could be detected by means of Raman spectroscopic measurement on the glasses. This could be achieved also for very tiny inclusions, where other methods such as light microscopy fall. Only results which can be generalized are considered in this work. Raman spectroscopy has proven to be an excellent method to determine the contents of gas bubbles by means of the rotational spectra of the gases or espectively to trace structural changes back from the mineral to the homogeneous glass via the vibrational spectra of the solids. Thus, the development within a cord can be demonstrated and the origin of knots can be explained. The use of this method in explaining defects, taking aluminum oxide containing lead glasses as an example, is presented by various investigations. The structural inhomogeneities in the glasses may be traced back to their origins. i.e., the glasses "have a memory" of their raw materials.