Effect of low NiO doping on anomalous light scattering in zinc aluminosilicate glass-ceramics

The effect of low NiO doping (0-0.15 mol%) on the extinction coefficient of zinc aluminosilicate glass-ceramics prepared by five different two-stage heat treatments was studied experimentally. Extinction coefficient vs wavelength presented as a log-log plot was separated into scattering and absorption coefficients. The NiO addition drastically changes not only values of the scattering coefficient at a given wavelength of visible light (effect 1), but also the type of wavelength dependence of this coefficient (effect 2). These effects do not correlate with variation of sizes and volume fractions of nanocrystals determined by Rietveld refinement of X-ray diffraction data. They cannot be described in the model of independent Rayleigh scatterers. These effects are characteristic features of anomalous light scattering by inhomogeneous glasses and can be explained by interference of light scattered by different nanocrystals. To calculate interference effects, the detailed information on mutual arrangement of nanocrystals is required, which unlikely can be determined experimentally for multiphase polydisperse system of nanocrystals. Instead, simplified models for systems of nanocrystals in glass-ceramics can be considered. And finally, we cannot explain the mechanism of the effect of small NiO additions on light scattering and hence, on structure of glass-ceramics.