Structural, optical, magnetic, and electrical properties of nanospinels containing different molar ratios of cobalt and aluminum ions

Abstract

Aluminum substituted by cobalt of cobalt aluminates having a nominal composition CoCo x Al2-x O4, where x = 0, 0.5, 1, 1.5, and 2, were synthesized by the thermal decomposition of complex precursors derived from metal nitrate salts and glycine. All samples were characterized using different techniques, XRD, FT-IR, TG, DTA, DSC, and TEM. XRD showed that all samples have a spinel cubic crystal structure. Using Debye–Scherrer formula, the calculated crystallite size was found cobalt concentration dependent and varied between 21 and 32 nm. Lattice parameter, X-ray density, porosity, and unit cell volume were calculated to show the effect of Al3+ substitution by cobalt on the crystal structure of the investigated spinel samples. Cation distribution and oxygen content into specific spinel stoichiometry of all samples were calculated. The optical, magnetic, and electrical properties were also studied. The spinel nano cobalt aluminate (x = 0.5) having Co/Al molar ratio of 1 showed the highest values of saturation magnetization (M s = 1.1 emu g−1) and conductivity (3.1 × 10–8 Ω−1 cm−1) compared to the other ones. The color parameters (L*, a*, b*) were also measured. All results were collected and discussed.