Electrical properties of lithium niobiosilicate gel derived glass and glass-ceramics

Lithium niobiosilicate glasses and glass-ceramics with the composition 95SiO(2)-2,5Li(2)O-2,5Nb(2)O(5) (mole%) were prepared by the sol-gel method. The gel was heat-treated (HT) at 500, 550, 600, 700 and 900 degreesC. The glass structure was analysed by X-ray diffraction (DRX) and scanning electron microscopy (SEM). The samples heat-treated (HT) at 700 and 900 degreesC present LiNbO3 particles. The dc conductivity decreases with the increasing of HT temperature. Complex permittivity at room temperature (1 Hz - 30 MHz) was analysed using the modulus formalism (M = 1/epsilon*). The imaginary part of M* versus frequency shows two maximums in both samples. The dielectric constant, measured at 1 KHz and room temperature, decreases with increasing the HT temperature. The dependence of dc conductivity and the dielectric constant can be ascribed to the diminution of the number of free ions in the glass matrix and to the orientation of the electrical dipoles of the particles.