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RESEARCH PRODUCT

Different kinds of solid solutions in the V2O5-ZrSiO4-NaF system by sol-gel processes and their characterization

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Abstract In the V2O5-ZrSiO4-NaF system, three kinds of substances have been identified by sol-gel methods depending on the V2O5 amounts in the composition. Their characterization by X-ray diffraction, measurements of unit cell parameters, UV-visible (UV-V) spectroscopy, differential thermal analysis and lab colour parameter determination allow the consideration of three kinds of solid solution in the zircon lattice: (a) V+5,V+4-ZrSiO4, thermally stable and with a deep green colour; (b) V+4-ZrSiO4, thermally stable and blue coloured, made by the sol-gel method and with V2O5 amounts lower than 0·03 mol per formula weight; and (c) Na+,F−,V+4-ZrSiO4, a solid solution with a deep blue-turquoise colour, made by addition of NaF to the V2O5-ZrO2-SiO2 system. Similarly, the green substance is obtained from the bluish substance synthesized at low temperatures (800°C) by both introduction of the V+5 ion into the zircon lattice and migration of the V+4 ions to the dodecahedral from the tetrahedral sites when the temperature increases.