Desorption influence of water on structural, electrical properties and molecular order of vanadium pentoxide xerogel films
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.
| Main Authors: | , , |
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| Format: | Digital revista |
| Language: | English |
| Published: |
Sociedad Mexicana de Física
2010
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| Online Access: | http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0035-001X2010000500009 |
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