Fiber optic application for thermal switching in vanadium dioxide films

In Situ X-ray Diffraction Studies on the Reduction of V2 O5 and WO3 by Using Hydrogen

The reduction of metal oxides with hydrogen is widely used for the production of fine chemicals and metals both on the laboratory and industry scale. In situ methods can help to elucidate reaction pathways and to gain control over such synthesis reactions. In this study, the reduction of WO₃ and V₂ O₅ with hydrogen was investigated by in situ X-ray powder diffraction with regard to intermediates and the influence of heating rates and hydrogen flow rates. Mixtures of V₄ O₉ , V₆ O₁₃ and VO₂ in two modifications were identified as intermediates on the way to phase-pure V₂ O₃ . None of the intermediates occurs in a single phase and therefore cannot be prepared this way. In contrast, the intermediates of the WO₃ reduction, H_0.23 WO₃ and W₁₀ O₂₉ , appear consecutively and can be isolated. For both reactions, the heating and flow rates have little influence on the formation of intermediates.

Strain engineering of optical properties in transparent VO2/muscovite heterostructures

Transparent VO₂/muscovite heterostructures have attracted considerable attention because of their unique chemical and physical properties and potential practical applications. In this paper, we investigated the influence of uniaxial mechanical strain on the optical properties of VO₂/muscovite heterostructures through Raman scattering and optical transmittance measurements. Under applied strain, linear shifts in peak positions of Raman-active phonon modes at approximately 340, 309, and 391 cm^-1 were observed. The extracted Grüneisen parameter values were approximately between 0.44 and 0.57. Furthermore, a pronounced strain-induced change in the metal-insulator transition (MIT) temperature was observed, which decreased under compressive strain and increased under tensile strain. The rates of MIT temperature variation reached 4.5 °C per % and 7.1 °C per % at a wavelength of 1200 nm during heating and cooling processes, respectively. These results demonstrate that the modulation of the optical properties of VO₂/muscovite heterostructures is controllable and reversible through strain engineering, opening up new opportunities for applications in flexible and tunable photonic devices.

Research progress on the preparation methods for VO2 nanoparticles and their application in smart windows

Accompanied with drastic changes in photoelectric properties, vanadium dioxide (VO₂) exhibits a first order metal–insulator phase transition (MIT) at the temperature of about 68 °C.

Size and crystallinity control of dispersed VO2 particles for modulation of metal–insulator transition temperature and hysteresis

Growth mechanism of VO₂ particles with size dependent crystallinity: a solid-state dewetting and pyrolysis synergistic effect. Crystallinity, strain and defects optimize and modulate the MIT behavior of VO₂ particles.

Coherent V2O3 Precipitates in ɑ-Al2O3 Co-Implanted With Vanadium and Oxygen

The oxides of vanadium VO2 and V2O3 are of fundamental and practical interest since they undergo structural phase transitions during which large variations in their optical and electronic properties are observed. In the present work, we report the formation of buried precipitates of V2O3 in sapphire by ion implantation and thermal annealing. It was found that the co-implantation of oxygen and vanadium was required in order to form nanophase V2O3 precipitates. Additionally, these precipitates, which formed only following an anneal of the co-implanted sample under reducing conditions, are coherent with the sapphire lattice. Two epitaxial relationships were observed: (0001)V2O3//(0001) ɑ-Al2O3 and (11-20)V2O3//(0001) ɑ-Al2O3. This finding is in agreement with results obtained elsewhere for thin films of V2O3 deposited on c-axis-oriented sapphire.

Temperature-controlled surface plasmon resonance in VO (2) nanorods

The optical properties of VO(2) nanoparticles formed in an amorphous SiO(2) host by stoichiometric ion implantation of vanadium and oxygen and thermal annealing have been determined and correlated with the particle size and morphology. The results show that that the temperature-controlled semiconductor-to-metal phase transition of the VO(2) nanophase precipitates turns on the classical surface plasmon resonance, with specific features that depend on the size and aspect ratio of the VO(2) particles. This effect improves the optical contrast between the metallic and semiconducting states in the near-IR region of the spectrum as a result of dielectric confinement that is due to the SiO(2) host. A fiber-optic application is demonstrated, as is the ability to control the characteristics of the phase transition by using ion implantation to dope the VO(2) nanoparticles with tungsten or titanium ions.