Dielectric and electrical study along with the evidences of small polaron tunnelling in Gd doped bismuth ferrite lead titanate composites

The phase formation of the polycrystalline samples of 0.6BiGd(x)Fe(1-x)O(3)-0.4PbTiO(3) (x = 0.05, 0.10, 0.15 and 0.20) was studied by X-ray diffraction technique prepared by using solid state reaction route. From analysing the X-ray diffraction pattern, the appearance of morphotrophic phase boundary between rhombohedral and tetragonal phase was observed in some of these composites at room temperature. The dielectric parameters are measured in a frequency range between (10(2)-10(6)) Hz at different temperatures. The nyquist plot (Z' vs. ZaEuro(3)) fit confirmed the contribution of bulk and grain boundary effect in the materials. Impedance, ac and dc conductivity showed the negative temperature co-efficient of resistance behavior. The temperature dependence of dc conductivity and relaxation time followed Arrhenius equation. The ac conductivity followed by the power law showed that the dynamics of charge carrier arises due to translational hopping motion for x = 0.10-0.20 and localised one for x = 0.05. The increasing behaviour of frequency exponent (n) with temperature strongly suggests that the small polaron tunnelling is the dominant conduction mechanism for the studied samples except for x = 0.05 composition.