Small polaron hopping-assisted electrical conduction and relaxation in BCT and Mn-doped BCT samples

Polycrystalline samples of Ba0.96Ca0.04TiO3 (BCT) and Ba0.96Ca0.04Ti0.96Mn0.04O3 (BCMT) were synthesized using the solid-state reaction route. XRD analysis confirmed the presence of the tetragonal phase in both as well as an additional hexagonal phase in the BCMT samples. The wt % of the segregated phase was found to be approximate to 8.96% using Rietveld refinement. SEM micrographs showed an increase in the density and a decrease in the grain size of the BCMT sample. P-E measurements confirmed higher remnant polarization in the BCT samples. A single depressed semicircle was observed in the Nyquist plots indicating non-Debye-type behavior and overlapping contributions of the grains and grain boundaries. The increase in the value of the conductivity exponent "n" (and n < 1) with temperature suggested that the electrical conduction mechanism was non-overlapping small polaron tunneling. The electron acceptor nature of the Mn ions and lower grain size of the BCMT samples resulted in higher activation energy as compared to the BCT samples.