Effect of Dy-substitution on structural, electrical and magnetic properties of multiferroic BiFeO3 ceramics

The polycrystalline samples of dysprosium (Dy)-modified bismuth ferrite (i.e., Bi1−xDyxFeO3; x=0–0.2 with the interval of 0.05) (BDFO) were synthesized using a high-temperature solid-state reaction method. Preliminary X-ray structural analysis showed that the reported crystal structure of BiFeO3 (rhombohedral) is invariant even with Dy-substitution at the Bi-site upto x=0.2. The scanning electron micrograph of the compounds showed (i) the uniform distribution of grains on the sample surface with high density and (ii) reduction of grain size on increasing Dy content in BiFeO3 (BFO). Studies of impedance, electrical modulus and electric conductivity of the materials in wide frequency (10–1000 kHz) and temperature (30–500 °C) ranges using a complex impedance spectroscopy technique have provided new and interesting information on the contribution of grains, grain boundary and interface in these parameters. Detailed studies of impedance spectroscopy clearly exhibit the dielectric relaxation of non-Debye type. The ac conductivity of the Dy-substituted BFO obeyed Jonscherʹs universal power law. An increase in Dy-content in BDFO results in the increase of spontaneous magnetization of BFO due to the collapse of spin cycloid structure.