Dynamics of Polar\nNanoregions and Relaxation Mechanisms\nin BiFeO<sub>3</sub>–BaTiO<sub>3</sub>–KNbO<sub>3</sub> Relaxor Ferroelectric Ceramics: A Dielectric and Impedance Spectroscopy\nStudy

The comprehensive investigation of dielectric and impedance\nproperties\nof (0.67 – <i>x</i>)BiFeO<sub>3</sub>-0.33BaTiO<sub>3</sub>-<i>x</i>KNbO<sub>3</sub> relaxor ferroelectrics\nhas provided insights into the impact of composition, temperature,\nand frequency on the dynamics and relaxation processes of polar nanoregions\n(PNRs). The presence and distribution of defects, introduced by the\nsubstitution of KN for BF, has a significant impact on PNRs. Two anomalous\npeaks are observed in the dielectric constant at low and high temperatures,\nwhich corresponded to the thermal activation of low-temperature PNRs\nand high-temperature defects, respectively. The peaks exhibited frequency\ndispersion and broadening effects, indicating a remarkable degree\nof disorder and heterogeneity within the material. Interestingly,\nthe <i>x</i> = 0.06 and <i>x</i> = 0.10 compounds\nhave revealed two distinct relaxation processes associated with compositional\nfluctuations, while the <i>x</i> = 0.14 and <i>x</i> = 0.18 compounds demonstrated a more uniform behavior with nearly\na single relaxation mechanism. Notably, at <i>x</i> = 0.14,\nan exceptional manifestation of superior polar ordering and pronounced\nrelaxor behavior was observed, which results in enhanced energy storage\nproperties.