Effect of sintering on structural and physical properties of nickel and lithium co-substituted barium titanate ceramics

In this work, polycrystalline Ba0.90Li0.1Ni0.05TiO3 ceramics were prepared by conventional solid state reaction technique after microwave calcination of starting materials. The effect of sintering on structural, dielectric and activation energy of Ba0.90Li0.1Ni0.05TiO3 ceramics was investigated. Phase structure was confirmed by XRD and Rietveld refinement of the XRD patterns was carried out to estimate the lattice parameters and atomic positions. It was observed that distortion of the structure (c/a) increased as the sintering temperature increased and this leads to a shift in phase transition towards higher temperature. The average size of grains was affected by the sintering process. The Curie temperatures were observed to vary within an interval of 150-160 degrees C with a degree of diffusivity gamma > 1. The dielectric constant of the different sintered samples increased from 500 to 1340 at ambient and from 1200 to 2512 at Curie temperature, while the dielectric loss decreased from 0.024 to 0.008 at RT and from 0.04 to 0.022 at Curie temperature as the sintering temperature is increased. The activation energies of all sintered samples were investigated using Arrhenius plots of the temperature dependence of AC conductivity at different frequencies. The result shows that the activation energy decreased with an increase of sintering temperature. The decrease of activation energy with an increase of sintering temperature is attributed to the reduction in a number of grains due to densification which leads to the individual grains come closer and the effective area of the grain to grain contact increases while the grains themselves begin to mimic single crystals.