Dielectric properties, cationic distribution calculation and hyperfine interactions of La3+ and Bi3+ doped strontium hexaferrites

Abstract

La3+ and Bi3+ doped M-type strontium hexaferrites (SrM) were prepared by sol-gel-auto combustion. X-ray powder diffraction (XRD), Scanning Electron Microscopy (SEM), Vibrating Simple Magnetometer (VSM), Mossbauer Spectroscopy and Novo electrical conductivity system were used for structural, morphological, and electrical characterizations of the products. The cation distribution calculations of the products were also provided. Single-phase M-type SrM with a chemical composition SrFe12-2xLaxBixO19 (0.0 <= x <= 0.5) were confirmed by XRD analysis, which also provided lattice constants and crystallite sizes of each product. The crystallite size was in the range of 43-51 nm. SEM analysis confirmed the presence of hexagonal crystal formation while the EDX analysis confirmed the presence of metal ions in the required stoichiometric ratio. From Fe-57 Mossbauer spectroscopy data, the variation in line width, isomer shift, quadrupole splitting and hyperfine magnetic field values on Bi and La substitutions have been determined. It was observed that ac conductivity of SrM increases slightly with increasing La3+ and Bi3+ ion substitutions at first, and then fluctuates with further substitution. Moreover, ac conductivity also increased with increasing frequency which could be regarded as an indication of ionic conductivity. It can be noted that activation energy increases as the enhanced contributions of doped-ion substitutions in SrM NPs with the illustration of a better stability of electrical bonds among the substitutional ions and Fe ions. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.