Interferometric measurements of ionic diffusion in soda-lime glasses

Laser reflection interferometry is used in measurements of ion-exchanged glass while the sample under test is etched in a solution of HF. The technique uses the interference of the reflections of an He-Ne laser from the surfaces of a glass sample normal to the beam of light. A periodic variation of the optical signal is observed as the thickness of the sample is reduced, each period corresponding to a change in thickness of 0.210 mu m. Since the etching rate depends on material composition, it is possible to deduce the concentration of the ion of interest. This method is used to analyze the diffusion of K+ in soda-lime glasses prepared at temperatures ranging from 375 degrees C to 415 degrees C for time intervals of 1-16 h. The diffusion constant was estimated from the experimental data showing agreement with the diffusion constant reported for a similar glass. The results also agreed when compared with scanning electron microscope X-ray diffraction measurements. (C) 1999 Elsevier Science B.V. All rights reserved.