Teixeira, D;
Quesada-Cabrera, R;
Powell, MJ;
Goh, GKL;
Sankar, G;
Parkin, IP;
Palgrave, RG;
(2017)
Particle size, morphology and phase transitions in hydrothermally produced VO2(D).
New Journal of Chemistry
, 41
(17)
pp. 9216-9222.
10.1039/c7nj02165h.
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Abstract
Different morphologies and sizes of VO 2 (D) particles were synthesised via hydrothermal synthesis using ammonium metavanadate (NH 4 VO 3 ) or vanadium pentoxide (V 2 O 5 ) as a vanadium precursor. By adjusting the concentration of vanadium precursors and the pH of the starting solution, a variety of morphologies and sizes of VO 2 (D) particles from 20 nm to 3 μm could be produced. A flower-shape morphology was obtained under strongly acidic conditions, passing through star-shape particles of 1 μm at pH 2.5 and finally obtaining homogeneous round balls of around 3 μm at pH 6.9. Nanoparticles were produced hydrothermally using V 2 O 5 as a precursor and hydrazine as a reducing agent. The transition from VO 2 (D) to thermochromic VO 2 (R) in micron scale particles occurred at 350 °C under vacuum. However, the nanoparticles of VO 2 (D) had a significantly lower VO 2 (D) to thermochromic VO 2 (R) transition temperature of 165 °C after annealing for only a few minutes. This is, to our knowledge, the lowest annealing temperature and time reported in the literature in order to obtain a thermochromic VO 2 material via another VO 2 phase. After the conversion of VO 2 (D) microparticles to thermochromic VO 2 (R), the metal to insulator transition temperature is 61 ± 1 °C for the heating cycle and 53 ± 1 °C for the cooling cycle. However, VO 2 (R) nanoparticles showed a significantly reduced metal insulator transition temperature of 59 ± 1 °C and 42 ± 1 °C for the cooling cycle lower than that reported in the literature for bulk VO 2 . This is important due to the need for having a compound with a switching temperature closer to room temperature to be used in smart window devices for energy consumption. W-VO 2 (D) star shape microparticle samples were prepared using 2-7 at% of the dopant (using ammonium metavanadate as a precursor), although unexpectedly this does not seem to be a viable route to a reduced metal to insulator transition in this system.
| Type: | Article |
|---|---|
| Title: | Particle size, morphology and phase transitions in hydrothermally produced VO2(D) |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1039/c7nj02165h |
| Publisher version: | http://doi.org/10.1039/c7nj02165h |
| Language: | English |
| Additional information: | © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2017. This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry |
| URI: | https://discovery.ucl.ac.uk/id/eprint/1573953 |
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