Synthesis of zircon powder by polyvinyl alcohol addition

The effect of polyvinyl alcohol (PVA) addition on the formation of zircon (ZrSiO4) powders was studied. The powders were prepared with a stoichiometric Zr/Si (1:1 mol%) mixture of zirconium oxychloride aqueous solution (ZrOCL2H2O) and tetraethoxysilane (TEOS) (Si(OC2H5)4) by a sol-gel method after PVA addition. The amount of added PVA varied between 1, 2, 3, and 4% by weight. The addition of PVA was aimed to be a catalyst which can accelerate the formation of zircon. The sol-gel process was followed by a mechanical activation via ball-milling and by calcination at 1000-1200 °C for 10 h. The phase composition of the resulted powders was determined through Rietveld analysis of X-ray diffraction (XRD) data using Rietica software. Results showed that amorphous zirconia transformed to a transient tetragonal zirconia phase at a calcination temperature of 1100 °C for all added PVA compositions, then reacted with silica to form zircon at 1200 °C. The 1, 2, and 4 wt% PVA-added samples crystallized to form zircon with the secondary phases of t-zirconia, m-zirconia, and cristobalite. The single phase of zircon was obtained in the 3 wt% PVA added-powder calcined at 1200 °C.