Effect of Grain Size on Resistivity and Voltage-Dependent Dynamic Conductance in Nano-crystalline Nd _0.6 Sr _0.4 CoO _3

The resistivity behaviour and voltage-dependent dynamic conductance of Nd _0.6 Sr _0.4 CoO _3 nanomaterials were studied with respect to two different grain sizes ( ∼ 55 nm and ∼ 140 nm). Three distinct regions were observed in the temperature-dependent resistivity ( ρ -T ) graph. An upturn in the ρ -T curve was observed below 100 K, which was enhanced with decreasing grain size. This enhancement was investigated, and the analysis suggests that electron–electron interaction plays a key role. We probed the transport mechanism using the isothermal current–voltage (I–V) characteristics. Non-linear dynamic conductance was found for both samples. A temperature-dependent non-linear exponent suggests three types of current transport mechanisms. A voltage-driven crossover from inelastic tunnelling via localized states to direct elastic tunnelling through the grain boundary was observed around the critical region for metal insulator transition.