Structural, optical, and dielectric properties of nano-ZnMn_2−xV_xO₄

Nano-ZnMn_2−xV_xO₄ (0.0 ≤ x ≤ 0.4) system was prepared by a simple sol–gel procedure. All samples exhibited a single spinel tetragonal phase excepting the sample with x = 0.4. The microstructure was investigated using X-ray diffraction and transmission electron microscopy. Full structural characterization was performed applying Rietveld analysis, X-ray photoelectron spectroscopic (XPS), and Fourier-transform infrared spectroscopy (FTIR) techniques. XPS analysis revealed the variation of the valence state of V and Mn with the doping level (x). Rietveld analysis revealed the distribution of different cations Mn, Zn, and V between the tetrahedral and octahedral sites, a result confirmed by XPS and FTIR analyses. The average bond lengths of tetra- and octahedral sites were determined and correlated with FTIR bands. Also, the different optical parameters were explored for all samples using UV–Vis diffused reflectance technique. The optical bandgap is increased by increasing the V content (x) in the nano-ZnMn_2−xV_xO₄ matrix. The dielectric characteristics and ac conductivity varied depending on the amount of V doping and purity of the samples. The mechanism of conductivity in the different samples was investigated in detail.