Synthesis of Mg1-xCoxAl2O4 blue pigments via combustion route

MgAl2O4 was successfully used as crystalline host network for the synthesis of cobalt-based blue ceramic pigments. Different compositions of Mg1-xCoxAl2O4 (x = 0.1-0.3) powders have been prepared by the combustion reaction of corresponding metal nitrates with mixtures of urea and beta-alanine. The resultant powders were characterized by means of XRD, TG-DTA, EDAX, SEM, BET surface area, diffuse reflectance spectrometry and CIEL*a*b* color measurement. For x = 0.2, thermal analysis investigations evidenced that combustion reaction occurs at 276 degrees C. XRD analysis certified the formation of the designed solid solution, no additional thermal treatment being required. EDAX elemental analysis confirmed the purity of the as-prepared compound. The resulted powders had large surface areas, which varied from 8.7 to 62.6 m(2)/g. The crystallite size of Mg1-xCoxAl2O4 powders was less than 15 nm. Experimental results evidenced that as the proportion of Co2+ increased, the crystallite size decreased and the specific surface area increased. The diffuse reflectance spectra of the Mg1-xCoxAl2O4 pigments confirmed the presence of tetrahedrally coordinated Co2+. CIEL*a*b* chromatic coordinates indicated that the bluest color was obtained for x = 0.2. (c) 2010 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.