Magnetic and Nanostructural Properties of Cobalt–Zinc Ferrite for Environmental Sensors

In this study, we compare nanoparticles (NPs) of Co0.5Zn0.5Fe2O4 spinel ferrite produced by a novel simple synthetic technique with those made by standard co-precipitation, sol-gel, and hydrothermal methods. The novel process is based on the addition of a very small amount of ethanol (only 2 vol% in water with a low ethanol:metals molar ratio of 0.5:1, not a co-solvent) during co-precipitation to synthesize a nanopowder, which formed single-phase magnetic spinel ferrite when heated at 700 !C. This technique produced cobalt–zinc ferrite NPs smaller than those formed by the other methods, with an average crystallite size of 17 nm calculated from X-Ray Diffraction and NPs sizes around 30 nm observed by scanning electron microscopy. A surface area of 32 m2/g, and a total pore volume of about 0.56 cm3/g, were determined by the BET isotherm. The best catalytic capabilities for converting ethanol vapor to CO, CO2, and H2O, as well as magnetic properties, were obtained for Co0.5Zn0.5Fe2O4 synthesized by the ethanol-assisted co-precipitation. The ethanol conversion rate rapidly increased above 175 !C, and the total conversion of ethanol was achieved at a relatively low temperature of 230 !C. This sample also had the largest magnetization of 58.2 A m2 kg"1 at 3 T, and a very small, near superparamagnetic, coercivity.