Structural analysis and dielectric investigations of pure and rare earth elements (Y and Gd) doped NiO nanoparticles

Abstract

In this work, pure and 2% rare earth elements RE (RE = Y and Gd) doped NiO nanoparticles, capped with polyvinyl alcohol PVA, were prepared by coprecipitation technique. X-ray powder diffraction XRD was performed to investigate the structural properties of the prepared samples. X-ray peak profile analysis was carried out using the Debye Scherrer model DSM, the Williamson Hall WH approach by its three models: Uniform Deformation model UDM, Uniform Deformation Stress model UDSM and Uniform Deformation Energy Density model UDEDM, and using the size-strain plot SSP. It was found that doping NiO with both Y and Gd causes a decrease in the lattice parameter, lattice strain and crystallite size. Transmission Electron Microscopy TEM was done to study the particles size and morphology. The particle size trend obtained from the TEM images were agreeable with the crystallite size obtained from the XRD results. The TEM images showed homogeneous, nearly spherical and slightly agglomerated NiO nanoparticles, that can be good candidates for rechargeable Lithium ion batteries. Dielectric measurements were done by measuring the parallel-equivalent circuit mode capacitance Cp, the dielectric loss tangent D (tanδ), the impedance Z and the impedance phase angle θ. Then, the frequency and temperature dependence of the dielectric constant ε’, dielectric loss ε”, loss tangent, ac conductivity σac and the imaginary part of both impedance Z″ and modulus M” were calculated and studied. Furthermore, the Nyquist plot was studied to correlate the electrical behavior by the microstructural contributions. The ionic radius and the valency of the dopant elements were found to be the factors that affect the dielectric behavior of the prepared samples. The dopant having larger ionic radius and higher valency was found to result in a higher dielectric constant and ac conductivity and a lower dielectric loss and electrical impedance, enhancing the role of NiO nanoparticles in electrical technologies, such as solar cells.