Structural, optical, and dielectric properties of nano-ZnMn2-xVxO4

Nano-ZnMn2-xVxO4 (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-ZnMn2-xVxO4 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.