Dielectric and structural studies of a SiO2–Li2O–Nb2O5 glass and glass-ceramic prepared by the sol–gel method

The preparation and properties, of nanocrystals embedded in a glass matrix have recently received a considerable amount of interest. The glass composition 92SiO2–4Li2O–4Nb2O5 (mol%), prepared by the sol–gel route gives origin to a transparent and colorless gel. The dried gel was heat-treated at temperatures between 500 and 750 °C, with and without the presence of an external electrical dc field. X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Raman and dielectric spectroscopy were used to characterize the glass samples. In the samples heat-treated at 650 °C with 1000 kV/m and in the 700 and 750 °C samples series, LiNbO3 crystallites, an important ferroelectric material is present. The behavior of the dc conductivity and the dielectric constant, in the glass and glass-ceramic, reflects the important effect of the temperature and the applied electric field on the sample structure.