Effect of Ba–Nb co-doping on the structural, dielectric, magnetic and ferroelectric properties of BiFeO3 nanoparticles

Multiferroic BFO nanoparticles of compositions Bi1−xBaxFeO3 and Bi1−xBaxFe1−xNbxO3 (x=.05 and .1) have been synthesized using sol–gel followed by an auto-combustion route. The effect of Ba–Nb co-doping on structural, magnetic, dielectric, leakage current and ferroelectric properties has been investigated. XRD patterns confirm the rhombohedral phase for all the samples in which traces of pseudo-cubic phase have been observed as a result of co-doping. The residual and saturation magnetization get increased significantly, which is attributed to a decreased degree of structural distortion and smaller particle size due to co-doping. Dielectric studies show strong dispersion for Ba-doped samples while Ba–Nb co-doped samples are nearly frequency independent. Furthermore, dielectric constant (ε∞) at higher frequencies increases with doping level whereas dielectric loss decreases due to reduction in defect centers by co-doping. Temperature dependent dielectric analysis reveals strong anomaly near magnetic transition (TN), signifying magnetoelectric coupling for all the samples. Leakage current has been decreased to 2–3 orders of magnitude and conductivity behavior has come close to ohmic type for 10% Ba–Nb co-doped sample, which suggested a significant reduction in oxygen vacancies. The saturation level of ferroelectric loop is also improved with doping level and remnant polarization increases from 1.28 μC/cm2 for 5% Ba-doped to 3.24 μC/cm2 for 10% Ba–Nb co-doped sample. Hence, Ba and Nb co-doped BFO nanoparticles can be used as a promising candidate for magneto-electric applications.