Combined Effect of Temperature Induced Strain and Oxygen Vacancy on Metal‐Insulator Transition of VO2 Colloidal Particles
2020
Vanadium dioxide (VO2) is a promising material in the development of thermal
and electrically sensitive devices due to its first order reversible metal-insulator
transition (MIT) at 68 °C. Such high MIT temperature (TC) largely restricts its
widespread application which could be enabled if a straightforward tuning
mechanism were present. Here this need is addressed through a facile
approach that uses the combined effects of temperature induced strain and
oxygen vacancies in bulk VO2 colloidal particles. A simple thermal annealing
process under varying vacuum is used to achieve phase transformation of
metastable VO2(A) into VO2(M2), (M2+M3), (M1) and higher valence V6O13
phases. During this process, distinct multiple phase transitions including
increased as well as suppressed TC are observed with respect to the annealing
temperature and varied amount of oxygen vacancies respectively. The latent
heat of phase transition is also significantly improved upon thermal annealing
by increasing the crystallinity of the samples. This work not only offers a
facile route for selective phase transformation of VO2 as well as to manipulate
the phase transition temperature, but also contributes significantly to the
understanding of the role played by oxygen vacancies and temperature
induced stress on MIT which is essential for VO2 based applications.
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