Doubling of the Phase Transition Temperature of VO by Fe Doping.

Vanadium dioxide (VO) undergoes a fully reversible first-order metal-insulator transition from the M1 monoclinic phase (2/) to a high-temperature tetragonal phase (4/) at around 68 °C. Modulation of the phase transition of VO by chemical doping is of fundamental and technological interest. Here, we report the synthesis of highly crystallized Fe-doped VO powders by a carbo-thermal reduction process. The impact of Fe doping on the structural and phase transition of VO is studied. The as-prepared Fe-doped VO samples crystallize in the M2 monoclinic form (2/), which is linked to segregation of the doping ions in the V2 zigzag chains. A large increase in the transition temperature to 134 °C is observed, which does correspond to a breakthrough in VO-type thermochromic materials.