Abstract
VO2 (A), a metastable phase of VO2, was prepared by hydrothermal treatment of an aqueous VOSO4 solution. (VO2 (A) has tetragonal symmetry but the crystal structure remains unknown. DTA and magnetic susceptibility measurements revealed a transition at 162°C which was detectable on heating but not on cooling. Semiconducting behavior was observed and the high-tempertature phase was characterized by lower electric resistivity. The transition on heating expanded the a-axis and contracted the c-axis. It was also observed that the lattice spacing along the c-axis was reduced to the half at the transition. The transition was found to be similar to the metal-insulator transition in the rutile-type VO2.
