THE THERMOCHROMIC VANADIUM DIOXIDE .1. ROLE OF STRESSES AND SUBSTITUTION ON SWITCHING PROPERTIES

The monoclinic ⇔ tetragonal transition occurring at 341 K for VO2 vanadium dioxide and the corresponding switching of the optical properties can be affected in various ways by thermal treatments, substitution, and pressure. The transition in pure or substituted powdered samples is characterized by thermal analysis (DSC), X-ray (XRD) and neutron (NRD) diffractions, and infrared spectroscopy (IR). The influence of pressure on the transition is discussed from neutron diffraction experiments at high pressure. The anisotropic compressibility coefficients in the monoclinic and tetragonal phases are considered. Some kinetic effects close to Tc, the transition temperature, have been observed by X-ray diffraction. The influences of pressure and substitution on the transition are then interpreted from a classical description of the chemical bonds in VO2. © 1993 Academic Press, Inc.