Structural characterisation of nickel-cobalt spinel-related oxides of NixCO3-xO4 (0≤x≤1.2) prepared by four different routes using XRD, FTIR, UV-VIS-NIR and XPS

AbstractFour analytical techniques, i.e. X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), ultraviolet-visible-near infrared reflectance spectroscopy (UV-vis-NIR), X-ray photoelectron spectroscopy (XPS) and four different synthesis methods, i.e the sol gel routes pechini and propionic acid route, thermal decomposition of nitrates and coprecipitation of hydoxides, have been used to characterise Ni – Co mixed oxides NixCo3-xO4 (0 ≤ x ≤ 1.2). XRD patterns show that the oxides crystallise in cubic spinel phases with a unit lattice parameter, which increases with x and closely linked to the preparation method. The UV-vis-NIR reflectance patterns confirm the two mixed valence ionic distribution. IR spectra exhibit strong peak characteristics of pure spinel. XPS study shows that there are possibly structural differences as ions site occupation or types of spinel form in compounds prepared by different methods