Preparation and Characterization of VO2 Nanopowders

✍ Scribed by Chenmou Zheng; Xinmin Zhang; Jianhui Zhang; Kairong Liao

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 259 KB
• Volume: 156
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2000.8952

✦ Synopsis

VO 2 powders with sizes of < 30 nm were successfully synthesized by pyrolysis of the precursor, [NH 4 ] 5 [(VO) 6 (CO 3 ) 4 (OH) 9 ] ' 10H 2 O. The e4ects of various pyrolysis conditions on VO 2 stoichiometries and crystal states were investigated in detail. The results of IR measurements show that for the stoichiometric VO 2 , from micro-to nanocrystals and to amorphous state, the absorptions shifted to lower wavenumbers, the numbers of bands decreased gradually, and the widths of the bands broadened. Moreover, the IR spectra of nanocrystals were obviously di4erent from those of microcrystals and amorphism. In comparison with stoichiometric VO 2 crystals, the IR absorptions of oxygen-rich VO 2 crystals clearly were blue shift, and those of oxygen-de5cient VO 2 crystals lightly red shift. The heats and temperatures of phase transition from VO 1.96 to VO 2.07 were determined. The results indicate that the phase transition temperature of VO 2.02 is 70.13C and has the maximum phase transition heat.