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Structural Evolution and Vanadium Distribution in the Preparation of V 4+ ‐ZrSiO 4 Solid Solutions from Gels

2002; Wiley; Volume: 85; Issue: 4 Linguagem: Inglês

10.1111/j.1151-2916.2002.tb00174.x

1551-2916

Francisco José Torres, J.V. Folgado, Javier Alarcón,

Catalytic Processes in Materials Science

Vanadium‐containing ZrSiO 4 ‐gel precursors with nominal compositions V x ‐ZrSiO 4 with x = 0.0, 0.002, 0.004, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.1, and 0.2 were prepared using a previously reported procedure and thermally treated over a range of temperature up to the formation of the V 4+ ‐ZrSiO 4 solid solution. The structural evolution and the V 4+ location and its homogenous distribution were followed using powder X‐ray diffractometry and electron spin resonance spectroscopy (ESR). Our experiments showed that a tetragonal form of V 4+ ‐ZrO 2 was the first crystalline phase obtained on heating the gels. On further heating, a phase transformation to the monoclinic form of V 4+ ‐ZrO 2 took place. Finally, the monoclinic form reacted with amorphous SiO 2 to form the V 4+ ‐ZrSiO 4 solid solution. A semiquantitative determination of the vanadium solubility in the ZrSiO 4 phase using ESR confirmed previously reported results obtained by lattice parameter variation over the solid‐solution series.