Preparation of nanosized CoAl2O4 powders by sol–gel and sol–gel-hydrothermal methods

Nanosized cobalt aluminate (CoAl2O4) spinel powders were prepared by the sol–gel and sol–gel-hydrothermal methods using aluminum sec-butoxide, cobalt salts and nitric acid as oxides precursors to form sols and gels. The obtained powders were characterized by XRD, DSC–TGA and SEM. The structure, particle sizes and temperature of formation of the resulting CoAl2O4 phases were found to depend on the precursors and processing methods. The temperature for obtaining the blue CoAl2O4 was about 1000 °C and 250 °C by using the sol–gel and sol–gel-hydrothermal methods, respectively, and CoAl2O4 powders with a size of 50–60 nm was resulted by the sol–gel-hydrothermal processing.