Abstract:
Zn sub(0.5-x)Mn sub(x)Ni sub(0.5)Fe sub(2)O sub(4) (x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5) ferrites were synthesized via the combustion route using malic acid as fuel. ICP-AES confirmed the desired stoichiometry of the synthesized ferrites. XRD studies revealed crystallite sizes of 10-23 nm, and with increasing Mn concentration, the lattice parameter decreased. SEM and HR-TEM analyses revealed particles in the nanoscale range. XPS studies confirmed the oxidation states of the constituent metal cations as Mn sup(3+), Fe sup(2+)/Fe sup(3+), Ni sup(2+), and Zn sup(2+). Mn K-edge XANES measurements further confirmed the presence of Mn in the +3 valence state occupying both tetrahedral and octahedral sites in the ferrite lattice. BET surface analysis indicated mesoporosity, with surface areas ranging from 24.26 to 49.06 m sup(2)/g. Electrical resistivity measurements confirmed the semiconducting nature of ferrites, and a decrease in resistivity with increasing Mn concentration was observed. Magnetic studies revealed soft ferrimagnetic behavior in the ferrites, with the saturation magnetization decreasing and the Curie temperature increasing as the manganese concentration increased. Gas sensing tests demonstrated high sensitivity (53 percent), high selectivity, and rapid response (3 s) and recovery (3 s) for composition x = 0.1 towards NO sub(2) gas. Electrochemical analysis showed charge storage behavior, with a specific capacitance of 101.35 F/g for x = 0.4. Collectively, the results demonstrate that systematic substitution of manganese can effectively tailor Ni-Zn ferrites into high-performance multifunctional materials for gas sensing and supercapacitor applications.
