The degradation of EBSD-patterns as a tool to investigate surface crystallized glasses and to identify glassy surface layers

Surface crystallized samples of glass-ceramics containing cordierite, rhombohedral BaAl2B2O7 and fresnoite were analyzed using electron backscatter diffraction (EBSD). The first two materials were chosen because surface crystallized samples of these materials have previously been shown to contain crystals covered by a very thin layer of glass. In all materials, EBSD pattern degradation occurs if the step size of a scan is chosen to be small. It is shown that the minimum step size enabling an evaluable EBSD-scan increases notably, if the crystals are covered by a thin layer of glass. It is also shown that pattern degradation may be utilized to prove the existence of such a thin glass or otherwise thermally sensitive layer. This provides significant information concerning the nucleation process of glasses also with respect to nucleation theory of glass-ceramics. It is also possible to describe the quantity of crystalline surface covered by the thermally sensitive layer.

► We apply EBSD to glass ceramic materials.
► EBSD-pattern degradation occurs and is enhanced when surface is covered by a thin glass layer.
► Enhanced degradation proves that the surface crystals are covered by a layer of glass.
► Quantification of the degree of surface coverage is possible.