Hexagonal VO₂ particles: synthesis, mechanism and thermochromic properties

Monoclinic vanadium dioxide VO₂ (M) with hexagonal structure is synthesized by hydrothermal method, and the phase evolution is evidenced. Interestingly, the hexagonal morphology comes into being as a result of the low-energy coherent interfaces, (211̄)₁//(21̄1̄)₂ and (21̄1̄)₁//(020)₂. The size of hexagonal particles is well controlled by changing the concentration of precursor solutions. Hexagonal particles exhibit excellent thermochromic properties with a narrow hysteresis of 5.9 °C and high stability. In addition, the phase transition temperature can be substantially reduced down to 28 °C by simply W doping.