A comparative study on citrate sol‐gel and combustion synthesis methods of CoAl <sub>2</sub> O <sub>4</sub> spinel
J. Raffiea Baseri, R. Naghizadeh, Hamid Reza Rezaie, F. Golestani‐Fard, Mohammad Golmohammad
Abstract
Abstract CoAl 2 O 4 spinel was successfully synthesized by combustion synthesis method using glycine and urea by 1:1 molar ratio as fuels and sol‐gel process using citric acid as a chelating agent. The as‐synthesized powders were calcined at desired temperatures to obtain CoAl 2 O 4 spinel as a single phase. X‐ray diffraction, thermogravimetric, and differential thermal analysis results revealed that the formation of CoAl 2 O 4 spinel in combustion method needs 300°C higher temperatures than those of sol‐gel. Scanning electron microscopy and transmission electron microscopy analysis results revealed that “sol‐gel spinel” had nanometric particle size which was smaller than those of “combustion spinel.” Temperature programed reduction with hydrogen and Fourier transform infrared spectroscopy results declared that there was a little residual cobalt oxide in combustion spinel while there is no oxide resided in “sol‐gel spinel.” Consequently, the sol‐gel method has more benefit in synthesizing spinel with sulfate precursors than combustion.