Crystallization behaviour and microstructural development in ZrSiO4 and V-ZrSiO4 solid solutions from colloidal gels

Zircon and vanadium-doped zircon blue pigments were prepared by heat treatment of gel precursors. Gels with nominal compositions Vx-ZrSiO4 with x=0.0, 0.002, 0.004, 0.02 and 0.2 were prepared by formation of a silica coating on zirconia colloidal particles previously obtained. The crystallization behavior and microstructural evolution were studied using X-ray powder diffraction (XRD), energy dispersive X-rays microanalysis (EDX), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The results indicated that the vanadia loading in the precursor gels speeds up the crystallization of the vanadium-containing tetragonal zirconia solid solutions and their transformation to the monoclinic form. The overall conversion rate of gel precursors to pigmenting powders increased when the vanadia content was higher. Microstructural data revealed that the used procedure for the preparation of vanadium-zircon pigments allowed high-purity and non-agglomerated powders with controlled particle size to be obtained.