Electron-microscopical studies of glass

Abstract

During the past 25 years, the use of the electron microscope in glass research has substantially expanded our knowledge of the microstructure of glasses, for instance of the phase separation processes in glasses. The use of electron microscope in glass research calls for special knowledge the lack of which would certainly lead to misinterpretations and wrong conclusions. Direct electron transmission of the specimen: low voltage beams create images of high contrast. On the other hand, there is always the risk of altering the specimen. If very high beam voltages are employed this is at the expense of image contrast. The optimum beam voltage range in the direct electron transmission of glass is 50 to 120 kV, depending very much on the kind of glass to be examined. The replica technique: this technique in electron microscopical investigations of glasses has more advantages than disadvantages but a highly developed technique is necessary. The most important factors will be described. Surface treatment of glass samples prior to making the replica: suitable etching processes of a freshly fractured glass surface sometimes help to enhance the visibility of structural peculiarities but faulty preparations have to be avoided. Use of the scanning electron microscope and the electron-beam microprobe: enormous advantages and problems will be described. Finally selected examples of electron-optical examinations of glass will be given.