Synthesis of cobalt–aluminate spinels via glycine chelated precursors

Abstract

In this work, synthesis of nanocrystalline Co IICo III x Al 2 − x O 4 (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. Co IICo III x Al 2 − x O 4 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 Co IICo III x Al 2 − x O 4 spinels. Prepared at 900 °C, the unit cell parameters of Co IIAl 2O 4, Co IICo III 0.5Al 1.5O 4, Co IICo IIIAlO 4, Co IICo III 2O 4 are 8.1038, 8.1007, 8.0867 and 8.0834 Å, respectively. Based on this work, preparation of a series of the Co IICo III x Al 2 − x O 4 spinels including black or bright blue Co IIAl 2O 4, Co IICo III 0.5Al 1.5O 4, Co IICo IIIAlO 4 and Co IICo III 2O 4 from glycine–Co(Al) complexing precursor has been well established.