Characterization of tin at the surface of float glass

Transmission Mossbauer spectroscopy (TMS) and conversion electron Mossbauer spectroscopy (CEMS) have been used to obtain spectra of Sn-119 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 mu m, while CEM spectra gave information on the near-surface region with a depth of about 2 mu m. The isomer shift and quadrupole splitting of Sn4+ in the near-surface were higher than the shift and splitting measured for the whole region, and the Debye temperature, theta(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 Sn2+ 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 Sn4+. (C) 1998 Published by Elsevier Science B.V. All rights reserved.