a College of Materials Science and Technology, Nanjing University of Technology, No. 5, New Mofan Road, 210009 Nanjing, China
b Department of Applied Chemistry, Graduate School of Engineering, 1-4-1 Kagamiyama, Higashi-Hiroshima, Hiroshima, Japan
c Department of Scientific and Engineering Simulation, Nagoya Institute of Technology, Gokiso-Cho, Showa-ku, Nagoya 466-8555, Japan
d Research Center for Industrial Ceramics, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Dingxi Road 1295, Changning, Shanghai 200050, China
Received 2 November 2011. Revised 11 January 2012. Accepted 15 January 2012. Available online 30 January 2012.
There are many similarities between VO2(B) and VO2(A) from crystallographic view. However, missing of VO2(A) during the preparation of VO2 polymorph confused many researchers. Here, the preparation of VO2(A) was studied systemically via a hydrothermal method in V2O5–H2C2O4–H2O system. As a metastable phase, it can be transferred from VO2(B) by assembling process. Usually, poly-crystal VO2(A) nano-fibers are formed by this process. On contrast, owing to the small energy gap between meta-stable VO2(A) and stable VO2(R), single crystal VO2(A) with regular shape can also be obtained by exfoliating some parts of VO2(R) during non-equilibrium cooling process. VO2(A) has higher phase transition temperature than stable VO2(R). The hysteresis in this phase transition can be observed by DSC measurement and the phase transition temperature of VO2(A) can be tuned down by tungsten doping.
