Synthesis of Zircon Using Zirconium Oxychloride and Sodium Silicate and Application in the Preparation of Iron Zircon Pigment

Abstract

Zircon precursors were synthesized using zirconium oxychloride and sodium silicate as raw materials. According to FTIR and XRD results, the zircon precursor is an amorphous phase with Zr-Si-O bonds. The zircon precursor crystallizes into zircon through the following processes. It remains amorphous even above 600°C, and the orthorhombic zirconia phase is formed in the precursor at 800°C. This orthorhombic zirconia phase is converted to the zircon phase at 1100°C, and the crystallization process of zircon is completed at 1200°C. The presence of Zr-O-Si bonds in the zircon precursor strongly inhibits the crystallization of ZrO₂. Therefore, it does not crystallize at 600°C and remains active, and it crystallizes into orthorhombic zirconia at 800°C. The orthorhombic zirconia is a metastable phase that does not appear during the conventional crystallization of zirconia. The orthorhombic zirconia formed is an unstable phase, so it reacts with silica at a relatively low temperature of 1100°C to form zircon. Zircon precursors synthesized with zirconium oxychloride and sodium silicate as raw materials were mixed thoroughly with iron hydroxide, and then calcined at 1200°C for 3 h to synthesize iron zircon pigments. The application of the zircon synthesis method using zirconium oxychloride and sodium silicate allows the synthesis of iron zircon pigments at relatively low temperatures of 1200°C without the addition of mineralizers.