Influence of temperature and pH on the morphology and the color of the CoAl2O4 prepared by sol gel method

The aim of this study consists in the synthesis of CoAl2O4 spinel by sol gel method using polyacrylic acid as chelating agent, with focusing on the influence of calcination temperature and pH on the morphology and on the color of the powders obtained. The prepared powders have been characterized by X- ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) and colorimetry (L*a*b*). The results obtained show that the spinel phase appears from 500 °C. FTIR spectroscopy reveals oxygen-metal bands characteristic of the spinel structure. The TEM micrographs of powders, synthesized at the temperatures 800°C, 900°C and 1100°C at pH=2,7 and 10, show that these powders are formed of nanometric particle size with a distribution between 20 nm and 90 nm. The colorimetric parameters, measured on powders calcined at 1100 ° C and regardless of the pH values, show an important blueness.