Dielectric relaxation in A₂FeNbO₆ (A∈=∈Ba, Sr, and Ca) perovskite ceramics

A₂FeNbO₆ (A∈=∈Ba, Sr, and Ca, abbreviated as AFN) ceramics were synthesized by a wolframite method with monoclinic FeNbO₄ precursor. X-ray diffraction studies revealed that Sr ₂FeNbO₆ and Ca₂FeNbO₆ had a orthorhombic structure, while Ba₂FeNbO₆ had a cubic symmetry. Dielectric properties of the AFN ceramics were characterized in a broad frequency range (1 Hz-10 MHz) at a temperature ranged from -120 to 300 °C. Two dielectric relaxations were observed to follow the Arrhenius law at both low and high temperatures for all samples. Polaron relaxation was proposed to explain the low temperature dielectric relaxations in AFN. The high temperature dielectric relaxations in AFN were a competitive phenomenon between the dielectric relaxation and the electrical conduction of the relaxing species.