A facile microwave-assisted synthesis of novel ZnMn₂O₄ nanoparticles and their structural, morphological, optical, surface area, and dielectric studies

Spinel ZnMn₂O₄ nanoparticles (ZMONPs) were successfully synthesized using a microwave-assisted chemical route. X-ray diffraction (XRD) revealed the growth of ZMONPs along the (211) plane with a tetragonal structure. The crystallite size was ~ 14 nm, estimated using the XRD data. Vibrational analysis confirmed the tetragonal structure of ZMONPs. Scanning electron microscopy images showed nanometer-sized particles, which was in agreement with the XRD results. EDX investigation of the samples demonstrated the good stoichiometric ratio of Zn, Mn, and O (1:2:4). The surface area and pore radius were also investigated in detail through Brunauer–Emmett–Teller analysis and were found to be 10.385 m²/g and 16.24 Å, respectively. The direct band gap for the ZMONPs was estimated using Tauc’s relation and was found to be 2.07 eV, which is larger than that of bulk ZMO (1.91 eV). Dielectric constant and loss values decreased with increasing frequency, while conductivity increased with increasing frequency. The dielectric constant was found to be in the range of 17–25 considering the entire testing range. The dielectric constant value was larger than expected, which could be the result of quantum confinement.