Synthesis of zircon pigments from rice husk ash and their performance in ceramic glaze

Abstract

ZrSiO4-based pigments have been known to be very stable in ceramic glazes but require a high firing temperature required for phase formation. This study examined the feasibility of using rice husk waste as a substitute for crystalline SiO2. The amorphous form of silica with some impurities was obtained by calcining the rice husk at 800℃. The general chemical formula were (Zr0.9M0.1)SiO4, where M = V, Pr, Fe and Cr. The solid-state processing was achieved by firing at 1300℃ for 12 h with NaF (5 wt%). X-ray Diffraction revealed a lower relative fraction between ZrO2 (secondary phase) and ZrSiO4 in the RHA systems compared to the oxide system for all dopants. Amorphousness of RHA did help enhance phase formability. The particle sizes were in the 3 µm to 5 µm range. Elemental analysis revealed some areas with intense signals of zirconium, indicating unreacted ZrO2 particles. Colorations appeared to be blue, yellow, brown and green for dopants of V, Pr, Fe and Cr, respectively. Technological performance was tested in a practical ceramic glaze and frequently used raw materials fired at its maturation point. The results of this study hold huge potential for using rice husks for sustainable manufacturing of pigments as green products.