Modeling platinum-inclusion dissolution in phosphate laser glasses

Abstract

An analytic model is developed describing the dissolution of platinum inclusions in LHG-8 and LG-750 metaphosphate laser glasses. The model assumes a spherical geometry and a diffusion-limited rate process in a quiescent fluid. The time for complete dissolution of a platinum inclusion is proportional to the square of the inclusion radius and is computed to be about 10 h at 1100°C for inclusions 10 µm in diameter in these glasses. This agrees with experimental results. When melting in a platinum vessel, the dissolution of the crucible walls limits the size of the platinum inclusion that can be dissolved because of the background contribution to the ionic platinum content. This effect is included in the model and is related to the exposed surface-area-to-volume ratio of the platinum vessel.