Structural and electrical investigations of pure and rare earth (Er and Pr)-doped NiO nanoparticles

Applying the coprecipitation technique, we synthesized PVA-capped Ni0.98RE0.02O (RE = Er md Pr) nanoparticles. Thermogravimetric analysis (TGA) was performed to study the thermal stability of the prepared samples to choose the calcination temperature accordingly. Thermal stability was attained at ~ 823 K with no further thermal decomposition beyond. The crystallinity and phase formation of the prepared samples were confirmed by powder X-ray diffraction XRD. Studying the effect of RE3+ doping on the structural parameters of NiO nanoparticles was facilitated by X-ray peak profile analysis, based on the Debye Scherer model, Williamson–Hall model and size strain plot. The doped samples exhibited smaller lattice parameter and strain, with the minimum strain along the (200) direction. Also, a smaller crystallite size was found for the doped samples, depending on the dopant’s ionic radius, giving rise to higher dislocation density and specific surface area. Transmission electron microscopy (TEM) proved the nanoscale of the prepared samples, in agreement with the XRD outcomes, and revealed slight agglomeration of homogeneous nanoparticles. DC conductivity indicated the semiconducting behavior of the prepared samples, triggered by Ni2+ vacancies. Hopping mechanism was found to be the conduction process with two activation energies, depending on the temperature range of study. The dielectric behavior was explained by Maxwell–Wagner interfacial polarization, in agreement with Koop’s theory. The correlated barrier hopping mechanism CBH was found to be the conduction mechanism. Moreover, the Nyquist plot was investigated. Doping by rare earth elements resulted in an increase in dielectric constant, AC and DC conductivities.