Ferroelectric phase-transition and conductivity analysis of La3+/Mn4+ modified PbTiO3 nanoceramics

The nanocrystalline samples of Pb0.92La0.08MnxTi1−xO3 (PLMT) (x=0.00, 0.04, 0.07, 0.10) were prepared by using a novel mechanical activation followed by a conventional solid-state reaction technique. The calcination and sintering temperatures were optimized by thermal gravimetric analysis and repeated firing. Preliminary structural studies using high resolution X-ray diffraction (HRXRD) technique at room temperature suggest that compounds are formed in a single phase with tetragonal crystal system. The field emission scanning electron microscopy (FESEM) shows that materials have well-defined granular microstructures, separated by the grain boundaries. The high resolution transmission electron microscopy (HRTEM) confirms about the nano-size of the particles. The ferroelectric phase-transition of PLMT materials is studied using dielectric measurements, which shows a shift in the transition temperature towards the lower-temperature side with increased doping concentration. The electrical conductivity calculated from impedance data has been observed to increase as a function of Mn concentration. The ac conductivity spectrum analysis suggests hopping of charge carriers among localized site as the possible mechanism for electrical conduction. The activation energy of the materials was found sensitive to its crystallite size.