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New-phase VO2 micro/nanostructures built by nanoflakes have been first synthesized by a hydrothermal method with NH4VO3 as precursor in the presence of poly(vinyl pyrrolidone) (PVP). The combined structural analysis of X-ray powder diffraction (XRD) and X-ray absorption fine structure (XAFS) spectroscopy determined the crystal structure as a new-phase vanadium dioxide, which is the isostructure of monoclinic NiWO4 and designated as VO2(D). In particular, electron spin resonance (ESR) measurements provides the direct evidence of vanadium ion in the four oxidation state. The formation energy of VO2(D) was estimated and showed a very close value to rutile-type VO2(R), which guided the preparation of VO2(R/M) by making use of the structural transformation from VO2(D) to VO2(R) at 320 °C, which was a comparatively lower temperature than other vanadium oxide, such as VO2(B). The obtained VO2 …