Dielectric relaxation and electrical conductivity property correlation in Gd-doped BBTO Aurivillius ceramics

Gd ion-substituted barium bismuth titanate (BaBi₄Ti₄O₁₅; BBTO) Aurivillius ceramics were synthesized to understand the preliminary impact through the structural, optical, frequency-dependent dielectric, conductivity, and complex modulus spectroscopic studies. X-ray diffraction (XRD) study confirmed the phase purity and crystallinity of the orthorhombic crystal system with A2₁am space group. The room temperature Raman study was correlated with the XRD results revealing a more feasible Aurivillius phase. A shift in the Curie temperature (T_m) towards low-temperature regions with increasing concentrations of Gd dopant was observed in temperature-dependent conductivity studies. The frequency-dependent conductivity study revealed a diffuse relaxor signature that degraded with dopant concentration explained by the modified Curie–Weiss law and normalized dielectric permittivity study. The frequency and temperature dependent modulus spectroscopic study indicated a dielectric relaxation mechanism in the presence of doubly ionized oxygen vacancies in pristine BBTO ceramics whereas the dominance of singly ionized oxygen vacancies was observed in Gd-doped one. The dielectric relaxation mechanism for pristine and doped Aurivillius are explained due to the thermal motion of the localized hopping process of electrons in variable oxidation states of different single ionized ions that depart from ideal Debye behavior. A detailed ac-conductivity study revealed the jumping relaxation mechanism or correlated barrier hopping mechanism (CBM) because of the localization of charge carriers, or the formation of polarons, respectively.