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

A(2)FeNbO(6) (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 Sr2FeNbO6 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 A degrees 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.