Study of the electric and dielectric properties of SiO2–Li2O–Nb2O5 sol–gel glass–ceramics

Glass with composition 88SiO 2 -6Li 2 O-6Nb 2 O 5 (mol%) was successfully prepared by the sol-gel technique. The dried and translucent gel was heat-treated at temperatures between 500 °C and 800 °C. Lithium niobate crystallites, an important ferroelectric material, were detected in the gel derived glass-ceramics heat-treated above 650 °C. The dc electrical conductivity (σ dc ) temperature dependence shows two regions with different activation energies. The dielectric constant decreases with an increase in the treatment temperature. The Z" frequency dependence shows two relaxation peaks, one at frequencies >1 kHz and another at low frequencies. The mean value of the relaxation times shifts to higher frequencies with an increase in measurement temperature. These dielectric behavior was an R 0 (R 1 CPE 1 )(R 2 CPE 2 ) equivalent circuit, using a complex non-linear least squares algorithm. The electrical and dielectrical behavior, of the glass materials, shows the important role of the treatment temperature on the gel-glass structure.