A comparative study of the structural, magnetic and electrochemical properties of Al3+ and Cu2+ substituted NiZn ferrite/reduced graphene oxide nanocomposites

Abstract NiZn ferrite/reduced graphene oxide (Ni 0.8 Zn 0.2 Fe 2 O 4 /rGO) nanocomposite and Al 3+ and Cu 2+ substituted NiZn ferrite/reduced graphene oxide (Ni 0.8 Zn 0.2 Al 0.1 Fe 1.9 O 4 /rGO and Ni 0.6 Cu 0.2 Zn 0.2 Fe 2 O 4 /rGO) nanocomposites were directly synthesized by one-step hydrothermal route. XRD and FTIR confirmed the formation of Ni 0.8 Zn 0.2 Fe 2 O 4 /rGO, Ni 0.8 Zn 0.2 Al 0.1 Fe 1.9 O 4 /rGO and Ni 0.6 Cu 0.2 Zn 0.2 Fe 2 O 4 /rGO nanocomposites. The average crystallite size was found to be 16.9–20.4 nm. The substitution of Al 3+ /Cu 2+ for Fe 3+ /Ni 2+ ions promotes a variation in unit cell due to the difference of ionic radius between Al 3+ /Cu 2+ and Fe 3+ /Ni 2+ , which leads the lattice parameter to vary from 8.353A to 8.394 A. Magnetic measurements reveal the saturation magnetization to vary with the replacement of Al 3+ /Cu 2+ for Fe 3+ /Ni 2+ ions. The variations of saturation magnetization in Al and Cu substituted NiZn ferrite/reduced graphene oxide nanocomposites have been explained in the light of Neel's two-sublattice theory. A maximum specific capacitance of 136.91 F/g and energy density of 16.80 W h/kg were obtained in Ni 0.8 Zn 0.2 Al 0.1 Fe 1.9 O 4 /rGO nanocomposite at a current density of 1 A/g. The enhanced electrochemical performances could be related to the high electronic conduction of Ni 0.8 Zn 0.2 Al 0.1 Fe 1.9 O 4 /rGO nanocomposite.