The Preparation of Blue CoAl2O4 Powders by the Malonate Method: The Effect of the Amount of Malonic Acid Used, the Formation Pathway of CoAl2O4 Crystallites and the Characteristics of the Prepared Powders

A pathway for the formation of normal CoAl2O4 particles is suggested. The optimal amount of malonic acid was determined, and the characteristics of the obtained powders were investigated. Normal CoAl2O4 powders were prepared using solutions of malonic acid and metal nitrates. X-ray diffraction, Brunauer-Emmett-Teller (BET) and scanning electron microscope (SEM) measurements, as well as Fourier transform infrared (FTIR) and ultraviolet/visible (UV-Vis) spectroscopy were carried out. Normal CoAl2O4 crystallites were formed by a solid state reaction between Co2AlO4 and amorphous aluminum oxide. The optimal molar ratio of malonic acid to the nitrate anions present in the initial solution was found to be 0.30 similar to 0.35. The particles were composed of agglomerates of primary particles. The primary particles were 40 run in size. This size was relatively constant regardless of the preparation temperature. However, the size of the agglomerated particles increased to 220 nm with increasing temperature.