Direct Transmission Electron Microscopy of the Thin Films of Phase Separated Glasses and Glass Ceramics

A simple technique for preparing the thin films for direct transmission electron microscopy was developed. This thinning technique is based on a chemical etching of the thin plate which has been cut from bulk material in advance and makes possible more reliable electron microscope study of the fine scale microstructure of glass.The microstructures of the phase separated alkali silicate, alkali borosilicate glasses and the transparent glass ceramics were observed using thin films and they were compared with those on carbon replicas of fractured and etched surfaces. The results are summarized as follows:1) The morphology observed in the micrographs by direct transmission of thin films coincided very well with that in the corresponding replica micrographs. However, thin films are better specimens than replicas to study fine structure below about 100 A because they reveal less ambiguous structure.2) It was shown with real examples that one could determine by selected area electron diffraction and dark field technique whether the individual phases observed in the micrographs were crystalline or not.3) The mean size of main crystals of transparent glass ceramics was observed to be about 300 A in the direct transmission electron micrographs. This value was not so much different from that calculated on the basis of broadness of X-ray diffraction peaks.4) These results mean that the thin film prepared by the described method is more suitable specimen than replica in study of the structure of phase separated or crystallised glasses in spite of the brittleness and the difficulty of preparation of many specimens at one time.