Surface fictive temperature of annealed and rate-cooled soda-lime glasses

The structural uniformity of thin (similar to 0.55 mm) annealed soda-lime g lass samples was investigated using an IR reflection method. The surface la yer of annealed soda-lime glasses was found to have an IR reflection struct ural band with a lower peak wave number than the bulk while no residual str ess was observed in the specimens. On the other hand, the IR structural ban d of specimens that were air-quenched from the glass transition temperature was the same both for the surface and the bulk, indicating a uniform struc ture. This finding can be attributed to a lower surface fictive temperature of the annealed glasses produced during the slow cooling due to the surfac e of the glass having a faster structural relaxation than that of the bulk. The surface fictive temperature of rate-cooled specimens was also lower th an the bulk fictive temperature; the slower cooled sample having a thicker surface layer with a lower fictive temperature. (C) 1999 Elsevier Science B .V. All rights reserved.