Structural, morphological, optical, thermal and magnetic study of mackinawite FeS nanoparticles synthesized by wet chemical reduction technique

Mackinawite FeS nanoparticles were synthesized by wet chemical reduction technique. The chemical composition of the nanoparticles determined by the energy dispersive analysis of X-ray (EDAX) showed them to be near stoichiometric and without any impurity. The X-ray diffraction (XRD) analysis showed the synthesized nanoparticles to be of single phase FeS and possess tetragonal unit cell structure with lattice parameters as a = 3.68 Å, c = 5.03 Å. The transmission electron microscopy showed the synthesized nanoparticles to be spherical in shape. The optical absorbance study revealed that the nanoparticles possess direct optical band gap of 2.39 eV. The thermogravimetric analysis exhibited two steps decomposition which was substantiated by the corresponding differential thermogravimetric peaks. The simultaneously recorded differential thermal analysis showed three regions of decomposition. The endothermic peak around 587 K is due to the solid state phase transformation of FeS structure to the orthorhombic MnP-type structure with space group Pnma. The kinetic parameters were evaluated by employing non-linear Kissinger-Akahira-Sunose method. The vibrating sample magnetometer study showed the nanoparticles samples to behave as super paramagnetic particles. All the obtained results are discussed in detail.