Microstructure of Fe–ZrSiO4 solid solutions prepared from gels

Microstructural changes associated with chemical and structural evolution from gels to Fex–ZrSiO4 solid solutions are reported. Mineralizer-free Fex–ZrSiO4 gels in the compositional range 0 ≤ x ≤ 0.15 were prepared by sol–gel liquid-phase route from mixtures of alkoxides of silicon and zirconium, and iron (III) acetylacetonate, and annealed at different temperatures and/or times.The first step on the whole process to the final Fex–ZrSiO4 solid solutions was the formation of aggregated of tetragonal Fe-doped ZrO2 nanocrystals with diameters smaller than 50 nm. At this stage the tetragonal Fe–ZrO2 were embedded in amorphous silica resulting nanocomposite materials. The formation of the final Fex–ZrSiO4 solid solution nanocrystals at around 1100 °C occurred almost simultaneously to the Fe–ZrO2 solid solution phase transformation from the tetragonal to the monoclinic form. The microstructural examination of specimens after annealing at 1200 °C revealed the development of Fe-doped zircon nanoparticles smaller than 100 nm.