Spherical to Needle Shaped Particles Transformation Study on Nanocrystalline Mg–Mn Ferrites

The study reports nanoparticles synthesis of Mg _x Mn_1−x Fe₂O₄ (x = 0.0, 0.2, 0.4, 0.5, 0.6, 0.8 and 1.0) spinel ferrite system using the chemical co-precipitation technique and describe the forming mechanism responsible for subsequent changes in grain morphology on Mg²⁺-substitution. The mean particle size of MnFe₂O₄ (x = 0.0) is found to be ∼40 nm, which decreases with increasing Mg-content (x) and becomes ∼27 nm for x = 0.5 composition. The shape of particles gradually transforms from spherical (x = 0.0–0.5) to lamellar (x = 0.6–0.8) to thick needle shape (x = 1.0), as revealed by transmission electron microscopic analysis. The morphological changes have been explained on the basis of role of NaOH, H₂O₂ and Mg²⁺ in governing rate of growth of planes of nanocrystals.