Effect of Nb substitution on the structural, dielectric and magnetic properties of multiferroic BiFe_(1-x)Nb_xO_3 ceramics

摘要

Polycrystalline BiFe_(1-x)Nb_xO_3 ceramics have been synthesized by standard solid-state reaction method. The effect of Nb substitution on the dielectric, magnetic and magnetoelectric properties of the BiFeO_3 multiferroic perovskite was studied. X-ray diffraction pattern revealed that all the samples with x = 0.00-0.10 showed rhombohedral perovskite structure. We obtained single phase upto doping concentration of x = 0.05 and with further increase in Nb concentration, some impurity peaks appeared. An anomaly in the dielectric constant (ε) and dielectric loss (tan (δ)) in the vicinity of the antiferromagnetic Neel temperature (T_N) was observed. Nb substitution reduced the antiferromagnetic Neel temperature (T_N ) in BiFe_(1-x)Nb_xO_3. Proper amount of Nb could decrease the dielectric loss. Magnetic hysteresis loops measured at 5 K/300 K and temperature dependent magnetization curves indicated ferromagnetism in Nb substituted BiFeO_3 ceramics. The room temperature magnetic moment was found to increase with increase in Nb concentration. The dependence of dielectric constant on the magnetic field is an evidence of magnetoelectric coupling in BiFe_(1-x)Nb_xO_3 ceramics.