Synthesis of cobalt–aluminate spinels via glycine chelated precursors

In this work, synthesis of nanocrystalline CoIICoIIIxAl2 − xO4 (where x = 0, 0.5, 0.8, 1, 1.5 and 2) spinels by the thermal decomposition of complex precursors derived from metal nitrate salts and glycine has been systematically studied. Based on XRD, FT-IR, DTA, TGA, SEM, TEM and BET analyses, it has been found that the as-prepared metal organic precursors with different Co and Al contents display different thermal behavior, crystal development and powder morphology and specific surface areas. Increment of Co content in precursors not only makes the pyrolytic reaction more intense but also improves the degree of crystallinity of the powder. CoIICoIIIxAl2 − xO4 spinel powders prepared from precursors with higher Co content usually have smaller specific surface areas. Higher Co content in the precursors also slightly decreases the unit cell parameters of the resulting CoIICoIIIxAl2 − xO4 spinels. Prepared at 900 °C, the unit cell parameters of CoIIAl2O4, CoIICoIII0.5Al1.5O4, CoIICoIIIAlO4, CoIICoIII2O4 are 8.1038, 8.1007, 8.0867 and 8.0834 Å, respectively. Based on this work, preparation of a series of the CoIICoIIIxAl2 − xO4 spinels including black or bright blue CoIIAl2O4, CoIICoIII0.5Al1.5O4, CoIICoIIIAlO4 and CoIICoIII2O4 from glycine–Co(Al) complexing precursor has been well established.