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RESEARCH PRODUCT

Synthesis and Characterization of Iron-Doped ZrSiO4 Solid Solutions from Gels

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The mechanism of formation and the structural features of tetragonal Fe–ZrO2-amorphous silica composites and particulated Fe-doped ZrSiO4 solid solutions were studied. A series of specimens with compositions Fex–ZrSiO4, 0 ≤ x ≤ 0.10 were prepared by sol–gel techniques and thermally annealed over the range of temperature between 400°C and 1600°C. Results confirmed the formation of tetragonal Fe–ZrO2 solid solution as first crystalline phase on the whole process leading to Fe-doped ZrSiO4 solid solution. The annealing temperature for the preparation of Fe-containing ZrSiO4 solid solutions was dependent on the nominal amount of iron. The Fex–ZrSiO4 solid solutions, with 0.02 < x < 0.08, were almost monophasic at 1100°C. The results of lattice parameter variation, energy-dispersive X-ray (EDX) and diffuse reflectance (DR), showed that in the as-prepared samples, Fe3+ cations entered into the zircon structure being located mainly in tetrahedral sites replacing Si4+. The solubility limit of Fe3+ in ZrSiO4 at 1100°C was in the range 0.07–0.1 mol of iron per mol of zircon (approximately 3–4 wt% as Fe2O3). This study opens new perspectives to the development of more ecological colored zircon-based solid solution materials using mineralizer-free synthetic procedures.