A New Metastable Phase of Needle-like Nanocrystalline VO2·H2O and Phase Transformation

✍ Scribed by Z. Gui; R. Fan; X.H. Chen; Y.C. Wu

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 321 KB
• Volume: 157
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2000.9037

✦ Synopsis

Needle-like nanocrystalline VO 2 ' H 2 O, crystallized in a new metastable phase with orthorhombic symmetry (a ‫؍‬ 6.015, b ‫؍‬ 4.642, and c ‫؍‬ 3.763 A > ), was synthesized by a long hydrothermal reaction from NH 4 VO 3 and hydrazine. The structure and composition of these nanocrystallites were characterized by X-ray powder di4raction, transmission electron microscopy, selected area electron di4raction, infrared absorbency spectroscopy, and thermogravimetric analysis. The in6uence of chemical reaction conditions on the features of the 5nal products was investigated, and the optimum conditions were found to be 1703C for 15 days with a N 2 H 4 concentration of 8.0%. Di4erential scanning calorimetry was conducted to study the phase transformation from as-prepared metastable VO 2 ' H 2 O to the more stable (B)VO 2 and rutile-type VO 2 .