Synthesis of cobalt ferrite with enhanced magnetostriction properties by the sol−gel−hydrothermal route using spent Li-ion battery

Abstract

The combination of a sol–gel method and a hydrothermal method was successfully used for synthesizing the nano-crystalline cobalt ferrite powders with a spinel structure using spent Li-ion batteries as the raw materials. The phase composition, microstructure, magnetic properties and magnetostriction coefficient of cobalt ferrite were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), magnetometer and magnetostrictive measurement instrument. The microstructure of the products exhibited hedgehog-like microspheres with particle size of approximately 5 μm. The different crystalline sizes and the microstructure of cobalt ferrites precursor were controlled by varying the hydrothermal time, which significantly affected the super-exchange and the deflection direction of the magnetic domain, and led to the change of the magnetic properties of sintered cylindrical samples. The saturation magnetization and maximum magnetostriction coefficient were 81.7 emu/g and −158.5 ppm, respectively, which was larger than that of products prepared by the sol-gel sintered method alone.