Influence of Ni doping on physical properties of La_(0.7)Sr_(0.3)FeO_3 synthesized by reverse micelle technique

摘要

In the present work, a series of Ni-doped La_(0.7)Sr_(0.3)FeO_3 perovskite nanostructures with chemical composition La_(0.7)Sr_(0.3)Fe_(1-x)Ni_xO_3 (x = 0.0, 0.01 and 0.04) were synthesized by the reverse micelle (RM) technique. The X-ray diffraction (XRD) analysis verifies good crystallinity and an orthorhombic crystal structure of the samples. The remarkable growth of the crystallites was observed in increasing the amount of Ni doping. The morphology, topography, and chemical composition were investigated through field emission scanning electron microscope (FESEM) equipped with an energy dispersive X-ray spectrometer (EDS). The FESEM/EDS measurements confirm uniform morphology and interconnected nature of the particles with relevant elements. The Fourier transform infrared (FTIR) spectra further demonstrate the perovskite structure through Fe/Ni-O asymmetric stretching and deformation of Fe/Ni-O-Fe/Ni bending vibrations in the lattice. A systematic reduction in the bandgap (E_g) is noticed upon the Ni doping in La_(0.7)Sr_(0.3)FeO_3, as estimated from the UV/visible spectra by employing the Tauc's relation. A distinct behaviour of dielectric properties was revealed as a function of frequency and temperature for all the samples. The dielectric constant (ε′), dielectric loss (tanδ), and ac conductivity (σ_(ac)) were measured at selected frequencies and temperatures. The results signify that the dielectric nature was frequency-dependent and thermally stimulated. The magnetic properties at room temperature indicate weak ferromagnetism with gradual increase in the maximum magnetization and coercivity with the increase in Ni concentration.