Sol-gel combustion synthesis and characterization of CoCr2O4 ceramic powder used as color solar absorber pigment

Abstract

A facile citric acid assisted sol-gel combustion method was performed to synthesize cobalt chromite (CoCr2O4) ceramic pigment. The effect of the annealing temperature on structure, morphologies, and optical properties of the prepared CoCr2O4 pigments were systematically studied by thermogravimetry, differential thermal analysis, X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM). The results show that CoCr2O4 spinel crystal was achieved after heat treatment of the as-burnt powder at a relatively low temperature (400 °C) and the average crystallite size of the CoCr2O4 pigment increased with the annealing temperature. Furthermore, on the CIE parameters of CoCr2O4 pigment, a* and b* values became much more negative with the annealing temperature due to much more Co2+ ions located in tetrahedral sites and much more Cr3+ ions located in octahedral sites. Finally, the measured solar absorptance indicates that this ceramic pigment is expected to fabricate the color paint coating for solar absorber application.