Structural and dielectric correlation in nano ZnMn_(2-x)Cr_xO_4

摘要

Nano ZnMn_(2-x)Cr_rO_4 samples (x = 0, 0.05, 0.15, 0.2) were synthesized by the sol-gel procedure. The synchrotron X-ray diffraction technique was used to investigate the developed phases, cation distributions of different ions between different sites, lattice parameters, and crystallite size upon increasing the amount of Cr doping in nano ZnMn_2O_4. X-ray photoelectron spectroscopy (XPS) was utilized to explore the cation oxidation state and the elemental composition of the samples. The valence state of the incorporated chromium is determined to be Cr~(3+) only. The effect of Cr doping, frequency, and temperature on the dielectric constant, dielectric loss, ac conductivity, complex impedance, and modulus was studied in detail. At a low temperature range, the samples exhibited a semiconductor feature, while at a higher temperature range, the samples revealed metallic behavior. Also, the conduction-type mechanism for each doped sample was determined. The activation energy was affected by the amount of Cr doping. A sample with 15% Cr doping has the highest conductivity among the other samples. Also, the effect of doping and temperature on the Nyquist diagram was examined.