Structural and impedance analysis of Bi0.5Na0.5Ti0.80Mn0.20O3 ceramics

The Bi0.5Na0.5Ti0.80Mn0.20O3 ceramic was synthesized by a conventional solid-state reaction technique. Rietveld refinement of X-ray diffraction data confirms the rhombohedral crystal structure of the compound with R3c space group. The optical band gap energy of the compound is found to be 1.93 eV. The substitution of 20% Mn ions at the Ti sites results in the improved dielectric characteristics and a shift in the ferroelectric to paraelectric electric phase transition peak from 330 degrees C to 370 degrees C in the material. The frequency dispersion of dielectric constant and its footprint in the Nyquist and Cole-Cole plots have been analyzed. The analysis of complex impedance and modulus spectroscopy confirms the non-Debye type of relaxation mechanisms in the material with contributions from both the grain and grain boundary to the electrical properties. The frequency dependence of AC conductivity data exhibits overlapping large polaron tunneling conduction mechanism in the compound.