Influence of low Bi contents on phase transformation properties of VO2 studied in a VO2:Bi thin film library

Doubling of the Phase Transition Temperature of VO2 by Fe Doping

Vanadium dioxide (VO₂) undergoes a fully reversible first-order metal-insulator transition from the M1 monoclinic phase (P2₁/c) to a high-temperature tetragonal phase (P4₂/mnm) at around 68 °C. Modulation of the phase transition of VO₂ by chemical doping is of fundamental and technological interest. Here, we report the synthesis of highly crystallized Fe-doped VO₂ powders by a carbo-thermal reduction process. The impact of Fe doping on the structural and phase transition of VO₂ is studied. The as-prepared Fe-doped VO₂ samples crystallize in the M2 monoclinic form (C2/m), 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 VO₂-type thermochromic materials.