Resumo

LONDONO-CALDERON, C.L.; VARGAS-HERNANDEZ, C.  e  JURADO, J.F.. Desorption influence of water on structural, electrical properties and molecular order of vanadium pentoxide xerogel films. Rev. mex. fis. [online]. 2010, vol.56, n.5, pp.411-415. ISSN 0035-001X.

Vanadium pentoxide xerogel films were grown by sol-gel method on pre-treated glass substrates, the gelation time was 14 days. The crystallinity of the films was analyzed with X-ray diffraction (XRD), identifying the composite V₂O₅·nH₂O before, and both vanadium pentoxide xerogel and α·V₂O₅ phases after, being subjected to thermal treatment (47, 97, 147, 204, 237, 272, 297 and 330°C during 15 minutes in each isotherm). The termal treatment reduces the degree of hydrations gel (n) from 2.1 to 1.4, besides the secondary phase (α·V₂O₅) has lattice parameters very similar to the precursor powder (which deviate about 0.3%). The electrical conductivity presents a semiconductor behavior in agreement with small polaron model, thermally activated and irreversible. The activation energies for three consecutive cycles were studied and analyzed: a strong dependency between the degree of hidratation's gel n with activation energy for high and low temperature regions was found. µ-Raman Spectroscopy showed the influence of temperature in the vanadium pentoxide gel film, presenting a phase transition from crystalline-amorphous for temperatures above 272^°C and inferring that the water presence in the sample is responsible in some way for the crystallinity of the material.

Palavras-chave : V₂O₅ xerogel; XRD; electrical conductivity; µ-Raman.

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