Control of concentration profiles in two step ion exchanged glasses

Two step ion exchange processes have been established to produce strong, flaw tolerant glasses. In order to identify optimum processing conditions, it is necessary to develop a theoretical framework for the procedure. The first step in this process is to develop the ability to predict the concentration profiles in the glass surfaces after the first and second exchange steps. Potassium concentration profiles in the ion exchanged glass surface were experimentally measured by electron microprobe analysis (EMPA) and the diffusion coefficients were calculated. At the same time, surface concentrations were determined by secondary ion mass spectrometer (SIMS). Using the measured diffusion coefficients and surface concentrations, theoretical concentration profiles for the two step process were calculated and a good agreement was found between the calculated and experimentally measured concentration profiles in single step and two step ion exchanged glasses. Therefore, the potassium concentration profile can be suitably controlled by changing the process parameters based on the current analysis.