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, (21 (1) over bar)(1)//(2 (1) over bar(1) over bar)(2) and (2 (1) over bar(1) over bar)(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 degrees C and high stability. In addition, the phase transition temperature can be substantially reduced down to 28 degrees C by simply W doping.