On light scattering in fluorozirconate glass-ceramics containing BaCl2 nano-crystals

The interference approximation is used for explanation of the low level of light scattering observed in fluorozirconate glass-ceramics containing BaCl2 nano-crystals (A. Edgar et al., Curr. Appl. Phys. 6 (2006) 355). For monodisperse BaCl2 nano-crystals with diameter 11 nm and volume fraction 0.2 embedded in the glass matrix, the calculations show that the interparticle interference in light scattering reduces a turbidity by a factor of 5 and more in comparison with the case of independent Rayleigh scattering. The interference effects may be partially suppressed by polydispersity and anisotropy of crystals. The results of our calculations contradict the results of numerical simulation of scattering, which was carried out using the discrete-dipole approximation in the paper cited above; namely, the simulated scattering system behaved essentially as a collection of independent scatterers and did not show any interference effects. To explain such a discrepancy, we have shown that the discrete models of crystal arrangement, used by Edgar et al., lead to inhomogeneous structures with clustering of crystals. The clustering, which takes place if the step of discreteness is of the same order as the crystal size, suppresses interference effects and is an obstacle to increasing a transparency of material. This qualitative conclusion was confirmed by calculation of extinction coefficient for the simplest model with discrete arrangement of crystals (dipoles).