Síntese e caracterização de óxidos ternários de Ni-Co-Mn com estrutura espinélio

Abstract

The spinel structure compounds may have a face centered cubic or body centered tetragonal symmetry, in which metal ions are distributed between tetrahedral and octahedral sites. Its physical properties depend not only on the nature of the metal ions, but also the distribution of ions on the sites. In this work, the method of the modified polymeric precursor was used for sample synthesis NixCo1−xMn2O4−δ, with x = 0, 0,15, 0,25, 0,5, 0,75, 0,85 and 1. It being the calcined xerogel at 900oC for 3 hours with an air flow of 50 ml/s and 20 rpm rotation. The results of X-ray diffraction showed that for higher nickel concentrations cubic phase of the spinel becomes predominant. And with the increase in cobalt content, the spinel begins to show both symmetry, cubic and tetragonal, being the predominant tetragonal phase with increasing atomic substitution. With the X-ray diffraction, it was verified that the increase of cobalt content in the material, can generate a distortion in the crystal structure, favoring the formation of the tetragonal spinel structure. Effect explained by the Jahn-Teller effect. Samples with low cobalt content present ferrimagnetic behavior and higher cobalt content show magnetic transitions at lower temperatures