Surface and Bulk ‐OH Infrared Absorption in ZrF ₄ ‐ and HfF ₄ ‐Based Glasses

Infrared absorption at the 3400 cm −1 ‐OH peak has been measured as a function of thickness for several ZrF 4 ‐BaF 2 ‐LaF 3 and HfF 4 ‐BaF 2 LaF 3 glasses to separate contributions from bulk and surface ‐OH. For glasses melted under CCl 4 reactive atmosphere, the peak is due almost entirely to surface ‐OH. In ambient atmosphere the ‐OH peak exhibited no time dependence over a 30 d period, indicating a very small rate of surface attack by atmospheric H 2 O.