Study of core shell structure and its effect on thermal, optical, electrical and magnetic properties of PPY-Ni_0.5Co_0.5Fe₂O₄ nanocomposites

Nanocomposites of polypyrrole (PY) and Ni_0.5Co_0.5Fe₂O₄ (NC) are prepared by chemical oxidation polymerisation with varying amount of NC. X-ray diffraction confirms their synthesis, and crystallite size (D) of NC particles is found to be in nanometre range. Core shell morphology is observed with the help of scanning electron microscope (SEM) images. Effect of this coating of PY on NC nanoparticles in nanocomposites induces variation in thermal stability pattern as compared to pure PY and NC observed by TGA. Although the shift in optical energy band gap is small, there is a complete transformation of magnetic behaviour of PY. It changes from diamagnetic PY to ferromagnetic nanocomposite material due to the ferromagnetic ferrite at the core. Electric conductivity of the NC material is very small which is enhanced by the PY shell material and as a result nanocomposites obtained electric as well as magnetic properties. This makes them valuable materials for electromagnets and electromagnetic shielding materials. Dielectric behaviour of the nanocomposites is also studied using impedance spectroscopy. All the nanocomposite has positive dielectric constant except the one with highest amount of NC which have negative dielectric constant. This unique negative dielectric constant of the nanocomposite is useful in superconductors.