Optical scattering in glass ceramics

The transparency of glass ceramics with nanocrystals is generally higher than that expected from the theory of Rayleigh scattering. We attribute this ultra-transparency to the spatial correlation of the nanoparticles. The structure factor is calculated for a simple model system, the random sequential addition (RSA) of equal spheres, at different volume filling factor. The spatial correlation given by the constraint that particles cannot superimpose produces a diffraction peak with a low S(q) in its low-q tail, which is relevant for light scattering. The physical mechanism producing high transparency in glass ceramics is demonstrated to be the low density fluctuation in the number of scatterers. The addition of a size distribution of the spherical particles produces important changes in the q-dependence of the scattering intensity in the region of the diffraction peak, but it has minor effects on the low-q tail.