Dielectric investigations of pristine and modified ZnO nanoparticles for energy storage devices

Pristine ZnO, Al-doped ZnO, and TiO₂ coated ZnO nanoparticles (NPs) were synthesized by the wet chemical precipitation technique. All the synthesized NPs were characterized using X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy. XRD analysis of pristine ZnO and Al-doped ZnO NPs revealed the hexagonal wurtzite structure with P6₃mc space group with no secondary phases and impurities. FESEM micrographs also depicted hexagonal grains with well-defined grain boundaries. TEM images showed hexagonal polyhedral shape for pure ZnO NPs and spherical shape dominating polyhedral particle for Al-doped ZnO NPs, and pseudospherical particles for TiO₂ coated ZnO NPs. Energy-dispersive X-ray spectroscopy of Al-doped ZnO indicates the eminent exchange of dopant in the lattice site of Zn. Dielectric Studies reveal the highest value of the dielectric constant and lowest value of dielectric loss for Al-doped ZnO as compared to pure and TiO₂-coated ZnO NPs. Suggesting Al-doped ZnO to be used as a dielectric material that can serve as a basic building block of the energy storage devices such as dielectric capacitor. TiO₂-coated ZnO NPs demonstrated higher AC conductivity in comparison to pure ZnO and Al-doped ZnO NPs suggesting their use as a conductive nanofiller materials in a polymer-based nanocomposite to achieve higher energy density.