Author(s): Figueiredo, Ana Cláudia Sardinha
Date: 2016
Persistent ID: http://hdl.handle.net/10362/21760
Origin: Repositório Institucional da UNL
Subject(s): Vanadium dioxide; Polymorphs; Metal-insulator phase transition; Hydrothermal synthesis; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia dos Materiais
Vanadium dioxide (VO2) has been intensively studied as it undergoes a metal-insulator phase transition (MIT) and exhibits numerous polymorphs. Therefore, it is very promising for MIT-based electronic and optoelectronic devices. The control of VO2 growth to obtain 1D micro and nanostructures has recently attracted more interest and opened doors for new optoelectronic applications. Herein, pure phase of VO2(B) and VO2(A) nanostructures have been synthesized by hydrothermal treatment in V2O5-H2C2O4-H2O system. The hydrothermal synthesis conditions were studied in order to observe the formation and evolution of VO2(B) and VO2(A) phases. Experiments showed that VO2(B) phase was firstly formed and then transformed into VO2(A) with the increase of hydrothermal reaction time from 8h to 72h. Additionally, it was studied the influence of some modifications on the hydrothermal synthesis process. The composition and morphology of the as-obtained samples were characterized using X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. Furthermore, the phase of transition temperatures and oxidation resistance of the as-obtained samples were evaluated by differential scanning calorimetry (DSC). In addition, the present study also provides an indirect way to obtain VO2(M), more precisely by calcination and laser annealing of VO2(B) and VO2(A), respectively.
