Formation of CoAl₂O₄ Nanoparticles via Low‐Temperature Solid‐State Reaction of Fine Gibbsite and Cobalt Precursor

Abstract

Nanocrystalline cobalt aluminate (CoAl 2 O 4 ) was synthesized by the solid‐state reaction method with cobalt chloride hexahydrate (CoCl 2 · 6H 2 O) as the source of Co and gibbsite (Al(OH) 3 ) as the source of Al, respectively. The effects of particle size of the starting fine gibbsite (0.6 and 13 μ m) and calcination temperatures (450, 550, and 650°C) on the properties of CoAl 2 O 4 were investigated by means of X‐ray diffraction (XRD), thermogravimetry analysis and differential thermal analysis (TG/DTA), X‐ray photoelectron spectroscopy (XPS), UV‐visible absorption spectroscopy (UV‐Vis), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Increasing of calcination temperature promoted the insertion amounts of Co 2+ in alumina matrix in CoAl 2 O 4 structure, which resulted in the brighter blue particles and increasing of UV spectra band. The lowest temperature for the formation of nanocrystalline CoAl 2 O 4 particles was 550°C for the solid‐state reaction of cobalt chloride and 0.6 μ m fine gibbsite.