Reactivity and microstructural evolution in the V-ZrSiO4 pigmenting systemprepared from colloidal gels

In this paper is intended to examine the microstructural changes associated to the sequence of reaction in the formation of the zircon-vanadium blue p igment, prepared from mixtures of previosly obtained ZrO2 and V2O5 colloida l sols and tetraethylorthosilicate (TEOS). The reaction sequence followed b y X-Ray diffraction (XRD), revealed the formation of a crystalline phase wi th the structure of tetragonal zirconia at the first step. The tetragonal t o monoclinic phase transformation took place before the formation of the V4-ZrSiO4, solid solution. The microstructures were observed by field emisio n scanning electron microscopy (FE-SEM) and energy dispersive X-ray analysi s (EDX). The formation of aggregates of tetragonal ZrO2 particles which wer e dispersed in an amorphous matrix of silica was firstly observed. The mech anism of zircon formation involved the reaction of amorphous silica with th e zirconia particles previously transformed to the monoclinic form. The dev eloped final microstructure of zircon phases consisted of well formed spher ical aggegates up to 3 mu m in diameter.