Evidence for intergranular tunnelling in polyaniline passivatedα-Fe nanoparticles

Abstract

Nanoparticles are of immense importance both from the fundamental and applicationpoints of view. They exhibit quantum size effects which are manifested in their improvedmagnetic and electric properties. Mechanical attrition by high energy ball milling(HEBM) is a top down process for producing fine particles. However, finenessis associated with high surface area and hence is prone to oxidation which hasa detrimental effect on the useful properties of these materials. Passivation ofnanoparticles is known to inhibit surface oxidation. At the same time, coating polymerfilm on inorganic materials modifies the surface properties drastically. In thiswork a modified set-up consisting of an RF plasma polymerization technique isemployed to coat a thin layer of a polymer film on Fe nanoparticles producedby HEBM. Ball-milled particles having different particle size ranges are coatedwith polyaniline. Their electrical properties are investigated by measuring the dcconductivity in the temperature range 10–300 K. The low temperature dc conductivity(I–V) exhibited nonlinearity. This nonlinearity observed is explained on the basis of the criticalpath model. There is clear-cut evidence for the occurrence of intergranular tunnelling. Theresults are presented here in this paper.