Low temperature synthesis of Co3O4 and (Co1−xMnx)3O4 spinels nanoparticles

Abstract

The (Co1−xMnx)3O4 solid solution have been synthesized in water at 60°C by soda addition to a cationic solution. XRD patterns show that spinel oxide has been obtained except for pure cobalt composition which exhibits also the presence of hydroxide and oxy-hydroxide. Therefore, to reach this composition, a different synthesis route has been developed: the cationic solution is added to the soda and for the first time Co3O4 nanoparticles have been synthesized by a direct precipitation in aqueous solution at low temperature. For each composition, the particles are well crystallized and exhibit a size close to 50nm. Each particle is composed by several crystallographic domains of about 10nm. The cubic to tetragonal transition reported in the literature for x=0.46 is observed in between x=0.33 and x=0.50. Raman spectra show that substitution of Co by Mn, in the cubic phase, introduces a random high disorder. In the tetragonal phase, occupation of the octahedral site remains a random occupation, while the tetrahedral site seems to be preferentially occupied by Co ions. All these results show that the precipitation is a simple, fast and safe process to synthesize pure phase of (Co1−xMnx)3O4 spinel solid solution in aqueous media at low temperature.