Papers by Author: Valerii V. Golubkov

Abstract: An evolution of the structure of three glasses of Na2O-Nb2O5-SiO2 system in the course of isothermal heat treatments at 660–700°C and the extinction coefficient of the material were studied. Spinodal phase separation was found to be a primary process followed by precipitation of nano-sized NaNbO3 crystalline phase. It was found that the spectral dependence of the extinction coefficient in the wavelength range λ= 400–800 nm corresponds to light scattering by spinodal structure at the phase separation stage and by independent Rayleigh scatterers (NaNbO3 nanocrystals) at the early stage of crystallization. The extinction coefficient increases at the first half of the crystallization stage and then decreases. At the late stage of crystallization and for the final glass-ceramics, the extinction coefficient α is 10–20 times smaller than that calculated for independently scattering nanocrystals and is characterized by anomalous wavelength dependence (α ∝ λ−6). The model for calculation of extinction coefficient is proposed, in which the interference effects in light scattering by nanocrystals are taken into account. On this basis, the variation of extinction coefficient in the course of crystallization and its wavelength dependence are explained.

Abstract: Formation processes and morphology of nanostructured glass ceramic materials containing finely dispersed lead sulfide crystalline phase has been studied by X-ray technique. The spatial ordering of PbS nanocrystals has been revealed which manifests itself by interference effects in X-ray scattering. We have ascertained that important morphology feature of the system is nearly monodisperse size distribution of nanocrystals.