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 (epsilon(infinity)) 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 (T-N), 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 mu C/cm(2) for 5% Ba-doped to 3.24 mu C/cm(2) 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. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.