Dielectric relaxation and Hopping conduction mechanism in Ni1-xSrxO nanostructures

Abstract

Electrical transport and conduction characteristics of sol-gel prepared Ni1-xSrxO (x = 0.00, 0.02, 0.04) nanostructures have been investigated systematically through DC and AC conduction measurements. The phase purity and structure of the samples have been studied using X-ray diffraction refinement and transmission electron microscope (TEM) analysis. It is observed that metal to semiconductor transition takes place in pure NiO sample whereas, it is suppressed on Sr insertion into NiO lattice. The activation energy (Ea) of the DC conduction have been found between 0.18 and 0.49 meV. Further, we have also observed relaxation process in doped NiO samples which are established by peaking behavior of dielectric constant. To discuss the conduction mechanism, the AC conductivity and temperature dependence of frequency exponent ‘n’ have been analysed using quantum mechanical tunnelling based Non-Overlapping Small Polaron (NSPT) model. Simultaneously, correlated AC conductivity data with NSPT model was used to calculate the value of maximum barrier height (binding energy) (Wm), AC activation energy, tunnelling distance (Rw) and density of states at Fermi level N (EF). Also, impedance spectroscopy suggests that the pure and Sr doped samples exhibit high order insulating behavior at the temperatures of 30 °C and 150 °C.