On structural studies and cation distribution of La added Zn-Ni-Mg-Cu spinel nano ferrite

Abstract

Zn0.75-xNixMg0.15Cu0.1La0.02Fe1.98O4 (x = 0.0, 0.15, 0.30, 0.60, 0.75) was synthesized by sol-gel auto-combustion technique. As-burnt samples were thermally annealed at 500oC for 3 hrs. The as-burnt and annealed powder were characterized by X-ray diffraction (XRD) technique. The lattice constant (aexp), unit cell volume (V) and hopping length at A and B (LA and LB) deceases with increase in Ni2+ content (x). Scherrer's grain diameter (D) for as-burnt and annealed samples respectively ranges between 13.26 - 22.20 nm and 23.61 - 30.93 nm. After annealing the specific surface area of the particles decreases which can be attributed to increase in the particle size. Annealing leads to variation in cation distribution at tetrahedral (A) and octahedral [B] site, which affects theoretical lattice parameter (ath), ionic radii of A- site (rA) and B-site (rB), oxygen positional parameter (u), tetrahedral and octahedral bond length (RA, RB), shared tetrahedral and octahedral edge (dAE, dBE) and Neel's magnetic moment (nBN). The bond angles θ1, θ2, θ3, θ4, θ5 and the distance between the metal ions at tetrahedral/octahedral site and anion (p, q, r) gives information about the A-A, A-B, B-B magnetic interaction. For lower values of Ni content (0.0 ≤ x ≤ 0.3), effective bond length (Reff.) increases with annealing and for higher Ni content (0.30 < x ≤ .75) Reff. decreases.