Colossal dielectric constant and non-debye type relaxor in Ca0.85Er0.1Ti1-x Co4x/3O3 (x=0.15 and 0.2) ceramic

We, herein, report on the structural, dielectric and electrical properties of Ca0.85Er0.1Ti1-xCo4x/3O3 ceramic prepared by sol-gel method. The XRD patterns of the samples at room temperature showed a perovskite phase having an orthorhombic structure with a Pbnm space group. The addition of cobalt (x > 0.1) improved the feature of electrical conductivity and dielectric constant. The DC-conductivity measurements show a semiconductor behavior with increasing Co rate and the Arrhenius plots of the direct current conductivity confirmed the existence of two anomalies refer to singly and doubly ionized oxygen vacancies. The (AC) electrical conduction was supported by two theoretical models of conduction that can be attributed to the correlated barrier hopping (CBH) mechanism and the non-overlapping small polaron tunneling (NSPT) model. Excellent dielectric properties were observed in the samples when we studied the dielectric constant and dielectric loss as a function of frequency [10-107 Hz] at different temperatures [460-700 K]. The dielectric constant exceeded 105 which is a colossal permittivity and it is one of the most giant values reported for ceramic capacitors. In the thermal study, we observed a dielectric anomalies, corresponding to relaxor-like behavior attributable to Maxwell-Wagner relaxation and conduction relaxation associated with doubly ionized oxygen vacancy.