Dielectric relaxations and electrical properties of Aurivillius Bi_3.5La_0.5Ti₂Fe_0.5Nb_0.5O₁₂ ceramics

Aurivillius single-phase Bi_3.5La_0.5Ti₂Nb_0.5Fe_0.5O₁₂ ceramics was synthesized by solid state reaction route. The ac data in terms of dielectric and impedance were collected to probe the dielectric relaxation behaviors in the ceramics. Two relaxations were distinguished and determined to originate from grains and grain boundaries, respectively, by the combination of impedance and electric modulus analysis. A phase transition was observed to take place at ∼440 °C. The possible relaxation-conduction mechanisms were discussed on the basis of kinetic analyses of dielectric data. This work elucidated the contributions of microstructures and defects to the relaxations and conduction. It is significant for correct understanding of electrical properties of Bi_3.5La_0.5Ti₂Nb_0.5Fe_0.5O₁₂ related ceramics and consequent modification of process to improve the performance of ceramics.