Accelerated microwave-assisted synthesis and in situ X-ray scattering of tungsten-substituted vanadium dioxide (V1−xWxO2)

Abstract

Vanadium dioxide (VO 2 ) has been widely studied due to its metal-insulator phase transition at 68°C, below which it is a semiconducting monoclinic phase, P2 1 /c, and above it is a metallic tetragonal phase, P4 2 /mnm. Substituting vanadium with transition metals allows transition temperature tunability. An accelerated microwave-assisted synthesis for VO 2 and 5d tungsten-substituted VO 2 presented herein decreased synthesis time by three orders of magnitude while maintaining phase purity, particle size, and transition character. Tungsten substitution amount was determined using inductively coupled plasma-optical emission spectroscopy. Differential scanning calorimetry, superconducting quantum interference device measurements, and in situ heating and cooling experiments monitored through synchrotron X-ray diffraction (XRD) confirmed the transition temperature decreased with increased tungsten substitution. Scanning electron microscopy analyzed through the line-intercept method produced an average particle size of 3-5 μm. Average structure and local structure phase purity was determined through the Rietveld analysis of synchrotron XRD and the least-squares refinement of pair distribution function data.

Harnessing the Metal–Insulator Transition of VO2 in Neuromorphic Computing

“…Conversely, if the R phase is made more stable relative to the M1 phase upon doping (such as upon substitutional incorporation of W 6+ on the cation lattice), [ 40,75 ] the T eq. is decreased (Figure 6D).…”

“…, thus requiring greater energy to initiate the transition from M1 to the R polymorph (Figure 6F). [61] Conversely, if the R phase is made more stable relative to the M1 phase upon doping (such as upon substitutional incorporation of W 6+ on the cation lattice), [40,75] the T eq. is decreased (Figure 6D).…”

Decoupling the metal–insulator transition temperature and hysteresis of VO2 using Ge alloying and oxygen vacancies

“…Substitutional incorporation of alloyant atoms has been used to tune the relative thermodynamic stabilities of the monoclinic and rutile phases, but with a few exceptions engenders suppression of the critical transition temperature. 10–14 Dopant atoms can profoundly modify local atomistic and electronic structure. In this communication, we decipher the mechanistic origins of the unusual elevation of transition temperature observed upon alloying of VO 2 with Ge and demonstrate the decoupling of transition temperature and hysteresis of the MIT through control of Ge alloying and its effects on oxygen stoichiometry.…”