Synthesis and formation mechanism of cobalt doped willemite blue pigments

Abstract

Turquoise blue pigment of Vanadium-zircon blue (DCMA number 14-42-2), which was already commercialized, was stable to be reproduced but insufficient to give strong blue. However, it possible to obtain more intense blue by partially substituting cobalt ions into the willemite(Zn2Si04) lattice classified into DCMA number 7-10-2 for blue ceramic pigment. By the composition of willemite CoxZn2-xSiO4(X=0-01, 0.03, 0.05, 0.07, 0.09 mole), this study used reagent grade zinc oxide, cobalt oxide and silicon dioxide as starting materials, carrying out the synthesis with solid reaction method by adding H3BO3 as a mineralizer. The firing temperature was between 1200°C and 1400°C. The characteristics of synthesized pigment were analyzed by X-ray diffraction, Raman spectroscopy and SEM and the characteristics of color tones were analyzed by UV-Vis spectroscopy and CIE-L*a*b* measurement. As a result, the optimal composition was Zn1.95Co0.05 with 1wt% of H 3BO3 as a mineralizer and firing condition was 1350°C/3 h. L*a*b* value was 29.25, 41.03, -59.93 for on glaze pigment and 37.03, 36.41, -60.03 for under glaze pigment.