Effect of electron irradiation on Na–K silicate glass investigated using X-ray photoelectron spectroscopy and pattern recognition method

Abstract

Alkali silicate glasses and melts play an important role in material science. Electron interaction with glasses is important for radioactive waste deposition, where electrons of various energies lead to irreversible changes. These changes are caused mainly by ionization and ballistic interaction of electrons with atoms, introducing structural disorder, changes in atomic composition and chemical state, accompanied by alkali ions diffusion. The Na–K silicate glass (5Na 2O · 10K 2O · 85SiO 2), pristine and electron irradiated (doses from 25 C m −2 to 20 236 C m −2) are investigated using X-ray photoelectron spectroscopy (XPS) and the pattern recognition (PR) and fitting procedures. Changes of composition and chemical state of atoms dependent on electron dose are analyzed. At low doses (100–300 C m −2), decrease followed by increase of O and Si concentrations was observed. Surface segregation, probable desorption, and in-bulk diffusion of K and Na ions (doses of about 50 C m −2 and 2000 C m −2, respectively) were observed. This was accompanied by changes in the chemical state of K atom, where with an electron dose increasing content of elemental K form accompanied by decreasing potassium peroxide form were observed. No difference in chemical state of Si and O atoms was visible under electron irradiation dose to 20 236 C m −2, within the sensitivity of the applied method.