Effect of pH, molar ration of fuel to nitrate and calcination temperature on the glycine-nitrate synthesis of nano CoAl2O4

In this research, solution-based combustion synthesis was applied to prepare the spinel CoAl2O4 pigment from precursor solution of Al(NO3)3.9H2O and glycine. Effect of pH values (2.5, 7, 10.5), the molar ratio of fuel to nitrates in the precursor solutions (1.5, 2) and the subsequent calcinations temperature (600, 800, 1000, 1200°C) on the powder characteristics were described. Gel formation, morphologies, specific surface area and colour of the powder were characterized using DTA/TG, XRD, TEM, BET and UV-Vis. Also quantitative analysis of the obtained samples was performed by the Rietveld-R.I.R. method. The results indicate that the crystalline spinel CoAl2O4 was formed at all different Gl/NO3_ molar ratios, pH and temperatures and higher temperature promote the increase of the crystallite size. According to TEM figures most of the particles calcined at 800 and 1000°C has sizes less than 50 and 100 nm respectively. Corresponding to results of BET experiment, specific surface area has its maximum values at pH=7 and decreases with increasing of temperature. The results of UV-Vis shows that the powders calcined at 600°C are not blue and when temperature increases the amount of b* decreases. Finally the applicability in commercial frits for ceramic glaze was successfully tested.