Grain and grain boundary conduction mechanism in sol-gel synthesized and microwave heated Pb0.8-yLayCo0.2TiO3 (y = 0.2–0.8) nanofibers

In this research, the nanosized Pb0.8-yLayCo0.2TiO3 (y = 0.2–0.8) (PLCT) samples were synthesized by microwave heated sol-gel method. The diffraction pattern revealed the existence of tetragonal phases related to lead titanate (PT) and lanthanum cobalt titanate (LCT) structures. Moreover, the PLCT structure was found to be on par with PT structure up to y = 0.4 while for y = 0.6 & 0.8 contents, the PLCT adopted the standard LCT structure. The field emission (FESEM) and transmission (TEM) electron microscopes accomplished complete formation of nanofibers at y = 0.8. The impedance spectroscopy analysis was performed over frequency ranging from 100 Hz to 5 MHz to address the microstructure variation. Furthermore, in order to account for total electrical conductivity, the grain and grain boundary contribution was described. In addition, the Nyquist plots illustrated two-layer model using two series RC circuits as a function of temperature. For the fitted Cole-Cole plots, the corresponding resistances (Rg & Rgb) and capacitances (Cg & Cgb) of grain and grain boundary were evaluated. Moreover, electrical conductivity was improved upon increasing the La-content. Later on, the Arrhenius plots (lnτ versus 1/T) were drawn to determine the activation energies.