Abstract
The nanocrystalline ZnMn2-xCrxO4 (x = 0, 1, 2) were successfully synthesized by combustion method. The products were characterized by XRD, FTIR, SEM, and TEM. XRD results revealed the formation of cubic phase spinel structure for ZnCr2O4 and ZnMnCrO4 as well as tetragonal spinel crystal structure for ZnMn2O4. The FT-IR data displayed two absorption bands in a range of 400–600 cm−1 arising from tetrahedral (A) and octahedral (B) stretching vibrations. The magnetic character investigated by vibrating sample magnetometer (VSM) spectra showed that all prepared samples exhibited super-paramagnetic behavior. The electrical properties of the ZnMn2-xCrxO4 (x = 0, 1, 2) system were studied at a frequency range of 102–106 Hz and temperatures ranging between 303 and 573 K. The electrical conductivity increased with increasing temperature referring to the semiconducting behavior of all the investigated samples. The conduction phenomenon could be explained based on the correlated barrier-hopping mechanism (CBH). Both dielectric constant (ε′) and dielectric loss (ε'`) values increased at all frequencies and temperatures which is attributed to the orientation polarization of the dipoles in the sample. The impedance spectroscopy (EIS) was examined to review the impact of grain and grain boundary on the electrical properties of all the investigated samples. The cation distribution and the composition effect on physical properties were discussed.