Structural, dielectric and electrical properties of lithium silicate ceramics: a comparative study

Lithium silicate (LS) ceramics were prepared via a solid-state reaction technique. Two ceramics with different molar ratios of Li₂CO₃/SiO₂ (1:1 and 1:2) were prepared for dielectric studies. X-ray diffraction pattern showed that Li₂CO₃/SiO₂ (1:1) ceramic is obtained as single phase composition whereas Li₂CO₃/SiO₂ (1:2) ceramic exhibit a multiphase structure with Li₂SiO₃ as a major phase. Microstructural analysis shows that the compounds have well defined grains separated by grain boundaries. Dielectric and electrical properties of the samples were studied in a wide temperature (30–400 °C) and frequency ranges (100 Hz–5 MHz). From the dielectric studies, we can prescribe Li₂CO₃/SiO₂ (1:2) ceramic as a good dielectric material since it possesses low dielectric loss. Detailed analysis of the impedance data suggests that the conduction of Li₂CO₃/SiO₂ (1:2) ceramic is mainly due to the bulk effects whereas the complex impedance plots of Li₂CO₃/SiO₂ (1:1) ceramic suggests the presence of both bulk as well as grain boundary contributions. The bulk resistance of the samples has been observed to decrease with rise in temperature showing a typical negative temperature coefficient of resistance behavior. The low activation energies of the samples suggest the presence of singly ionized oxygen vacancies in the conduction process.