ION-BEAM ANALYSIS OF FLOAT GLASS-SURFACE COMPOSITION

Data are reported On ion beam surface analysis methods of proton-induc ed X-ray emission (PIXE), and helium-induced X-ray emission (HIXE), ma de simultaneously with Rutherford backscattering spectrometry (RES), w hich were taken with samples from across the full width of a float gla ss production line. Data are given for both clear and green glass. Sig nificant variations are recorded between signals from the lower surfac e, (the face in contact with tin), and the upper surface, not only for the uptake of the tin, but also for the consequent changes in the nea r surface composition of the other main elements of the glass. In part icular, the tin alters the local compositions of iron, calcium, silico n, and sodium. The changes are interpreted in terms of the furnace tem perature gradients and chemical interactions. In all cases, including the green glass, iron is depleted from the non-tin face relative to th e bulk composition, and the changes of surface content of the iron dif fers on the two faces relative to the bulk value.