Impact of Bi doping on the structural, optical, and dielectric features of nano ZnMn2O4

This work aims to upgrade the functional properties of ZnMn2O4 via doping with Bi3+. Nano ZnMn2-xBixO4 (x = 0, 0.03, 0.05, 0.07, 0.1, 0.15, 0.2) samples were prepared by the sol-gel method. The structure, microstructure, and formed phases in ZnMn2-xBixO4 samples were determined using Rietveld-calculated profile fitting of the experimental x-ray synchrotron radiation diffraction data. The tetragonal spinel ZnMn2O4 phase was formed with a tiny (similar to 2-4 %) hexagonal ZnO phase. The morphology and different vibration bands in ZnMn2-xBixO4 samples were investigated using scanning electron microscopy and Fourier transform infrared techniques. The diffused reflectance technique was used to explore the effect of Bi doping on the absorbance and optical band gap of ZnMn2O4. The optical band gap energy decreased from 2.42 to 1.83 eV as the percentage of Bi-doped ZMO increased from 0 to 10 %, then increased again for higher Bi content. The dielectric permittivity is affected by the Bi-doped amounts and temperature. As the amount of Bi and temperature increased, the impedance of the ZMO sample and relaxation time changed. All samples exhibited both metallic and semiconducting behaviors. All samples have a non-Debye relaxation phenomenon. Samples with x = 0.03 and 0.2 exhibited the maximum conductivity among other doped samples. These findings introduce ZnMn2-xBixO4 samples for new applications in optoelectronics and optical devices.