Lattice Strain of Zn-Mn Mixed Ferrite Nanocrystals in a Core-Shell Morpho-Chemical Structure

In this work, the crystalline structure, chemical composition, size, and morphology of core@shell nanoparticles based on Zn-Mn ferrite nanocrystals were investigated. These materials have been proposed as promising candidates for multifunctional applications in biomedicine, catalysis, environmental remediation, among others. Those properties were probed by using several experimental techniques such as Synchrotron X-Ray Diffraction, Energy-Dispersive X-ray Spectroscopy, Transmission Electron Microscopy and Selected Area Electron Diffraction. Results show that all synthesized nanoparticles present a single crystalline spinel phase without the appearance of undesirable byproducts. The nanoparticles present a non-stoichiometric Zn-Mn ferrite core, due to a Fe enrichment and a Zn loss with respect to the synthesis medium. The surface treatment of the nanoparticles induces a greater iron enrichment, which occurs at the nanoparticles surface without changing the crystalline structure. Finally, modifications in lattice parameters and strain suggest a contribution of the Mn²⁺ cations, mainly related to their easy oxidation in the synthesis route, which increases the structural vacancies of Mn-richer ferrites.

Keywords:
Strain; Mixed ferrite; Nanocrystals; Core-Shell; Nanoparticles