Optical scattering in glass ceramics

We analyse measurements of the optical extinction coefficient for fluorozirconate glasses containing a volume fraction of ∼0.2 of barium chloride nano-particles. We find that the glass ceramics are about a factor of six more transparent than predicted by Rayleigh scattering theory, based on estimates of particle sizes from X-ray diffraction and electron microscopy measurements. A numerical simulation of scattering using the discrete-dipole approximation has been made in order to investigate whether this particular discrepancy, and the “ultra-transparency” observed in other glass ceramics in general, can be explained by particle proximity and interaction effects as has been proposed in the literature. The simulated scattering system behaves essentially as a collection of independent scatterers up to a volume fraction of at least 25%, and so these effects are not responsible for the high transparency in this system.