Transport Phenomena of alkali-ions in silica glasses

Karel Jurek, Markéta Jarošová, Ivo Drbohlav

The aim of this research project that is realized in cooperation with Institute of Glass and Ceramics of the University of Chemical Technology, Prague is systematic study of the influence of electrons injected under the surface of silica glasses irradiated by the electron beam on the stimulated diffusion of alkali ions and consequently caused structural and chemical changes in irradiated glasses.

Model glasses containing various alkali ions (Na, K, Rb, Cs), mainly binary but also ternary, are prepared at Institute of Chemical Technology , Prague. Samples are prepared (i.e accurate grinded and polished) in optical workshop of Institute of Physics AS CR. Glass samples are exposed to electron beam in Laboratory of scanning electron microscopy and X-ray microanalysis using X-ray microanalyzer JXA-733 of JEOL (Japan). This instriment enables to use electron beams of energy in the range from 1 to 50 keV and beam currents up to 10 A. In the frame of this project the methodology of preparation of cross-sections of irradiated glasses was elaborated using optical grinding and polishing with precission 1m and the chemical and mechanical infuences kept as small as possible. The chemical changes in glasses caused by electron irradiatin were investigated by X-ray microanalysis and photoelectron spectroscopy, volume changes were studied by atomic force microscopy (AFM).

On the base of available information on creation of the electric field by trapping of primary electrons in the glass and electron structure of studied glasses a model was developped which explaines mechanisms causing the migration of alkali ions and consequently the changes of their structure. The gained findings on the structure structure of alkali oxidic glasses and transport of alkali ions can lead to improvement of technology of this materials and creation of new, more resistive glasses for fixing of radioactive vaste, X-ray tubes, TV screens, dozimeters, e.t.c. Each finding on radiative damage of glass has great significance for large range of materials used in new, modern technologies in nuclear power technology, X-ray diagnostics, spectral analysis, information technology, dozimetry, e.t.c. The possibility to change locally the concetration of alkali ions by the electron beam can be applied also in modern nanotechnologies.