A comparative study on the dielectric and ac conductivity of ionically conducting lithium silicate ceramics

Lithium silicate ceramics were prepared via solid-state reaction technique. Two ceramics with different molar ratios of Li₂CO₃/SiO₂ (designed as L₁S and L₂S) were prepared for dielectric studies. X-ray diffraction pattern showed that L₁S ceramic is obtained as single-phase composition, whereas L₂S ceramic exhibit multiphase with Li₄SiO₄ as a major phase. Dielectric studies of the compounds shows a strong frequency dispersion of permittivity in the low frequency region followed by a nearly frequency independent behavior in the high frequency region. Dielectric loss (tan δ) seems to be reduced at higher frequencies after reaching the instrumental saturation. The present study reveals that high dielectric compositions can be realized by Li₂O-rich system (i.e., L₂S ceramic). From the dielectric studies, we can prescribe L₁S ceramic as a good dielectric material since it possesses low dielectric loss. The values of activation energies suggest the presence of singly ionized oxygen vacancies in the conduction process.