Characterization of tin at the surface of float glass

Abstract

Transmission Mössbauer spectroscopy (TMS) and conversion electron Mössbauer spectroscopy (CEMS) have been used to obtain spectra of 119Sn in three commercially produced soda–lime–silica float glasses. Measurements have been made of the f-factor of both tin oxidation states from a series of results at temperatures between 290 and 13 K. TM spectra yielded data on the whole tin layer, which extends to a depth of about 20 μm, while CEM spectra gave information on the near-surface region with a depth of about 2 μm. The isomer shift and quadrupole splitting of Sn 4+ in the near-surface were higher than the shift and splitting measured for the whole region, and the Debye temperature, θ D, was found to be significantly less in the surface than in the full depth containing tin, showing that it was less tightly bound. The shift, splitting and Debye temperature of Sn 2+ remained the same throughout the glass surface within experimental errors. These results are discussed in terms of the conditions of the float process and differences in the coordination number of Sn 4+.