In-situ study of the formation of sodium-niobate-silicate glass-ceramics with dielectric spectroscopy

Abstract The dielectric response and the effect of heat treatment on the properties of a potassium-sodium-niobium-silicate glass with a high content of niobium are studied in wide temperature and frequency ranges. Heat treatment of the glass results in the formation of sodium niobate nanocrystals that leads to a significant decrease in the dielectric losses and an increase in the dielectric constant and the activation energy of the DC conductivity of the medium. It is shown that the crystallization process takes place in two stages – the first is the liquid-liquid glass separation (segregation), and the second is the crystals growth. Based on the classical Johnson-Mehl-Avrami-Kolmogorov theory, it is confirmed that the nanocrystals are anisotropic and that no new nuclei arise during the crystallization. The main contribution to the dielectric response of the initial and heat-treated glasses is made by the low-frequency relaxation process associated with the conductivity (charge polarization).