Co 3O 4 nanoparticles by chemical combustion: Effect of fuel to oxidizer ratio on structure, microstructure and EPR

Abstract

In this work we describe and discuss the synthesis, (micro)structure (XRD, SEM) and EPR of Co 3O 4 (normal spinel structure with a = 0.808 nm) nanoparticles synthesized by urea-based combustion method using cobalt nitrate precursor. Fuel-to-oxidizer ratio ( Ψ ) is used as a control parameter to investigate how lattice parameter, particle size and EPR susceptibility vary with Ψ = 0.25 – 2 in steps of 0.25. The average crystalline size of Co 3O 4 was estimated from the X-ray diffraction peaks of powders using Scherrer’s formula and Williamson–Hall equation. The average crystalline size varies from 7(±0.1) nm to 18(±0.28) nm. The surface areas were measured using BET method and size of the particles thus deduced agree with XRD based values. The FT–IR confirms formation of Co 3O 4. We also calculated average micro strain of the Co 3O 4 nanoparticles with varying Ψ . The SEM micrographs give evidence for increased porosity upon increasing Ψ . EPR spectra has yielded the paramagnetic susceptibility of the Co 3O 4 nanoparticles. Band gap of Co 3O 4 nanoparticles was determined by UV-visible absorption edge.