Exploiting the effect of inversion degree, phase, and size in nickel ferrite nanoparticles: Implications for electrochemical behaviors and magnetic hyperthermia properties

Abstract

Nickel ferrite (NiFe2O4-NFO) nanoparticles with differences in crystal structure (phase, purity, and cation distribution) and size, were effectively synthesized by a simple hydrothermal method at various treatment temperatures (160, 180, and 200 °C). NiFe2O4 nanoparticles were structurally investigated using XRD measurements with Rietveld refinement and other measurements such as Raman and SEM. Among synthesized NFO samples, benefiting from possessing the smallest size, narrow size distribution, and partially inverted structure (δ = 0.54), as well as the co-presence of the high ratio of the side phase of Ni(OH)2, NFO-180 sample exhibited many unique features in terms of not only electrochemical properties (conductivity, active electrochemical surface area, and charge/electron transfer kinetics) but also the magnetic hyperthermia properties with high saturation magnetization and large SAR coefficient. Some mechanisms and hypotheses were proposed to demonstrate the significant impacts of the crystallite phase, size, purity, and particularly the cation distribution within NFO nanoparticles on electrochemical behaviors and magnetic hyperthermia properties. According to that, the precise control of the crystal structure (phase and purity), size, and cation distribution in NFO in general, and spinel materials in particular, will be an ideal approach to improve efficiency according to the requirements related to given applications.