Structural and high temperature conduction studies of (Na0.46Bi0.46Ba0.08) (MnxTi1−xO3)–CuO lead-free piezoelectric ceramics

Polycrystalline lead-free (Na0.46Bi0.46Ba0.08)(MnxTi1−xO3) + 0.2CuO ceramics (x = 0.0, 0.5, 2.0, 3.0 wt%) were prepared via solid-state reaction method. X-ray diffraction (XRD) analysis confirmed the formation of single-phase perovskite structure and indicated the presence of morphotropic phase boundary, where the tetragonal and rhombohedral phases co-existed for all the synthesized compositions. Scanning electron microscopy (SEM) analysis revealed that the average grain size decreased with the increase in Mn content. Impedance spectroscopy (IS) indicated that Mn doping was found to decrease the grain boundary resistance. Two semi-circles were observed for higher Mn content which indicates the contribution of both bulk grains and grain boundaries. Non-Debye type and temperature dependent relaxation phenomenon was also revealed by IS studies. The activation energies at different frequencies were found to be 0.05–0.9 eV, indicating hopping charge conduction mechanism. These results have comprehensive implications for the expanded use of BNT based lead free piezoelectric ceramics for practical applications.