Realization of improved magnetodielectric coupling and electrochemical performance of microwave assisted sol-gel prepared spinel manganese chromium oxide nanopowders

Abstract

Microwave assisted sol-gel approach is used to successfully produce spinel phase of manganese chromium oxide nanoparticles. Hydrous manganese chloride, hydrous chromium chloride and ethylene glycol are used as precursors and solvent. Ratio of Mn/Cr (0.20–0.65) is varied during synthesis. Microwave radiations (720 W) are used to obtain nanopowders of manganese chromium oxide nanoparticles. Mn/Cr ratios of 0.20–0.25 produce amorphous behavior, while Mn/Cr ratios of 0.30, 0.35, 0.40, 0.45, and 0.65 produce mixed phases. Single phase of spinel MnCr2O4 nanoparticles is observed at Mn/Cr ratios of 0.50, 0.55, and 0.6. Normal dispersion behaviour with high value of dielectric constant (~60 at log f=5), low tangent loss (0.004 at log f =5) and low conductivity values are observed for Mn/Cr ratio of 0.6. Cole-Cole plots show a single semicircle, indicating that grain boundary resistance plays a significant role. The results of the vibrating sample magnetometer show that all the samples have ferromagnetic behavior, with a high saturation magnetization value (~ 15 emu/g) for Mn/Cr ratio of 0.6. Large and positive magnetodielectric response is observed for Mn/Cr ratio of 0.55 & 0.6. Cyclic voltammetry curves demonstrate high specific capacitance for Mn/Cr ratios of 0.55, and 0.6. Results obtained under as-synthesized conditions suggest suitability of the optimized material for magnetic and energy storage applications.