The extinction coefficient caused by light scattering for liquating glass during its crystallization is calculated. The calculation is based on a model that considers the crystallization of regions of inhomogeneity (particles) that form as a result of liquation and are distributed in a glassy matrix. It is shown that the extinction coefficient can reach a maximum when the degree of crystallization is 0.5-1. The cause for the appearance of such a maximum is the incoherent scattering that takes place in a mixture of amorphous and crystallized particles, while the conditions for its appearance are associated with the presence of elements of ordering in the relative position of the particles. It is pointed out that these conditions are apparently satisfied during the crystallization of sodium-niobium silicate glasses.
G. T. Petrovskii, A. A. Zhilin, M. P. Shepilov, V.-B. B'en, and K.-K. Li, "Nonmonotonic transmittance variation of a material during the crystallization of liquating glasses," J. Opt. Technol. 70, 857-863 (2003)