Structural and physicochemical properties of nickel manganite NiMn2O4-δsynthesized by sol-gel and ultra sound assisted methods

Abstract

In this work we present the structural, magnetic and surface characterization of the ceramic nickel manganite oxide NiMnO synthesized by two methods: sol-gel and ultrasound-assisted sol-gel using nitrate salts as precursors. We have characterized the non-stoichiometric samples NiMnO using different physicochemical analyses. X-ray diffraction and Rietveld refinement of the X-ray data indicated that the samples crystallize in the Fd3m space group characteristic of cubic spinel-related oxides. The specific surface area of the oxides was 1.3 m/g (SG) and 16.3 m/g (UASG). SEM results showed particle agglomerates of 1.05 μm (SG) and 0.85 μm (UASG). Temperature dependence magnetization measurements were performed and a ferrimagnetic transition was identified at 103 K and 105 K depending on the preparation method (SG and UASG, respectively). The observed Curie constant was found to vary from 7.4 to 7.7 cm K mol and hysteretic magnetization vs. applied field curves at different temperatures were obtained. XPS studies of these oxides reveal the presence of Ni, Mn, Mn and Mn ions at the surface. A probable ionic distribution as a function of the synthesis method is proposed.