Characterization of shallow stress-profiles in chemically strengthened soda-lime glass

Abstract

Ion-exchange is a strengthening method employed to increase silicate glasses' wear resistance and fracture strength. The characterization of the residual stress-field introduced by the ion-exchange process is a crucial yet challenging problem particularly for shallow exchanged layers. In this work, an enhanced iterative etching method was proposed to more accurately characterize the residual stress-field in shallow, chemically-strengthened glasses. With iterative etching, sub-micron layers are removed from the free-surface of the glass and the local compressive stress is estimated by measuring the variation in the internal tensile stress. In this study, the proven iterative etching method was complemented by the latest phenomenological models describing both the ion-exchange and the stress relaxation processes, as well as by the improved modeling of the etching behavior of soda-lime glass. The approach substantially reduced the number of fitting parameters and provided a physically-truthful description of the stress profile. Finally, the residual stress-profile obtained in this work was compared to the predictions obtained by various optical and mechanical characterization techniques commonly used in the industry. Optical methods were found to be more reliable than mechanical methods for shallow, ion-exchanged glasses.